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Biology > Unit 6: Human Physiology > Flashcards

Unit 6: Human Physiology Flashcards

1
Q

What is the purpose of exocrine glands?

A
  • food particles are too big to be absorbed through intestine walls of digestive system
  • food particles need to be digested to soluble molecules that can pass through the membranes in the intestinal tissues
  • to do that, exocrine glands of the digestive system secrete enzymes that hydrolyse large molecules into smaller molecules
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2
Q

Define the digestive system

A

digestive system = complex tube from mouth to anus

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3
Q

What are the two types of organs in the digestive system

A
  • the organs that make the tube are usually called the organs of the digestive tract or alimentary canal
  • organs that secrete chemicals into the tube are called accessory organs
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4
Q

Draw a diagram of the digestive system

A

https://file.notion.so/f/f/e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560/cb3f85ac-4f39-4183-921a-9a1167a341b6/Untitled.png?id=3cf4af86-a088-45d7-a09f-bba6dc61c810&table=block&spaceId=e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560&expirationTimestamp=1714953600000&signature=oyH1djvUhB_W8d1rOgdH68bkU2AMLj5KXQU-ZJXnuQg&downloadName=Untitled.png

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5
Q

Give the steps for digestion

A
  1. in the mouth, you chew food and it’s mechanically mixed with salive
  2. saliva has the enzymes amylase that start the digestion of starches (carbohydrates). saliva also moistens the mixture to make it easier to swallow
  3. the bolus (food mixture) enters the oesophagus (also called the gullet) and then moves to the stomach through peristalsis
  4. longitudinal and circular muscles work antagonistically, meaning opposite to each other. when one contracts, the other relaxes. the longitudinal muscle contracts to widen the lumen of the alimentary canal while the circular muscle contracts to constrict lumen
  5. in the stomach, food is churned with acid. the food and acid mixture is called chyme (pronounced kime). stomach acid kills bacteria and starts digestion of proteins and continues digestion of carbohydrates
  6. food enters small intestine. first section is called the ‘duodenum’ (meaning twelve fingered cuz that’s how it looks). Here, the acid from the stomach needs to be neutralised so enzymes in the small intestine can function properly. These enzymes have an optimum pH of neutral to alkaline, and some digest fat and lipids while others digest carbohydrates, and others digest proteins. By the end, the digestion has been completed and the digested products are absorbed by the last section of the small intestine which is the ileum. Most digestion happens in the small intestine
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6
Q

Define Peristalsis

A

Peristalsis = wave of contraction and relaxation of the longitudinal and circular muscles of the alimentary canal, by which contents are forced along the tube

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7
Q

What are the accessory organs and what do they each do

A
  • pancreas secretes amylase, lipase, and protease (aid in digestion of starch, lipids, and proteins respectively) into the small intestine
  • liver secretes bile to emulsify lipids
  • gall bladder stores bile
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8
Q

Why is bile not an enzyme

A

bile isn’t an enzyme. it breaks large lipid globules into smaller lipid globules (emulsify). bile doesn’t facilitate hydrolysis reactions like enzymes.

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9
Q

Where is the small intestine located and how long is it

A

small intestine is muscular tube of about 6-7 metres long in humans that lies between stomach and large intestine

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10
Q

What are the three sections of the small intestine

A

Duodenum, jejunum, and ileum

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11
Q

What lies on the surface of the small intestine and why

A

inner surface of the small intestine is covered with villi, which increase surface area by 30-60 fold, which is essential for absorption

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12
Q

What are the tissue layers of the small intestine from outside to inside

A
  • serosa — outermost layer with connective tissue in contact with body cavities
  • longitudinal muscles — responsible for peristalsis
  • circular muscles — responsible for peristalsis
  • submucosa — connective tissue supporting mucosa that has large vains and arteries, giving rise to the capillary bed of the mucosa
  • mucosa — innermost layer forming soft lining of the tube comprised of epithelium (lines the lumen of the digestive track), connective tissue, and smooth muscle (villi form part of this layer)
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13
Q

What happens in the small intestine

A
  • in the small intestine, food is broken down to monomers that can easily be absorbed by the villi and taken up by the lymph or blood
  • first large food is broken into smaller units, then the smaller units are broken down into these monomers
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14
Q

What produces enzymes for the small intestine

A

pancreas and wall of the intestine produce necessary enzymes and secrete them into the lumen (centre space) of the small intestine

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15
Q

What digestive enzymes are made by the acinar cells of the pancreas?

A
  • amylase — breaks starch down into maltose
  • endopeptidase aka trypsin — breaks down proteins into smaller polypeptides
  • lipases and phospholipases — break down lipids and phospholipids to fatty acids and glycerol (both produce both). in phospholipids, they also break into a phosphate.
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16
Q

How does pancreatic juice get to the small intestine

A

the pancreatic juice with the enzymes is then carried through the pancreatic duct to the duodenum, where it’s released into the lumen of the small intestine

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17
Q

Which enzymes complete digestion in the small intestine following pancreatic enzymes

A
  • nucleases — break down DNA and RNA
  • Maltase: break down maltose into glucose
  • lactase — breaks lactose down into galactose and glucose
  • exopeptidases — break down small polypeptides into single amino acids
  • dipeptidases — break down a dipeptide into two amino acids
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18
Q

Where do the monomers in the small intestine go?

A

the monomers in the small intestine are then absorbed into the blood or lymph

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19
Q

What happens to cellulose in the digestive system

A

cellulose remains undigested as the enzyme cellulase (which breaks down cellulose) isn’t produced by humans

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20
Q

Where does the absorption of food molecules take place and what is required?

A

actual absorption of food molecules takes place in the small intestine, across the epithelium. transport proteins are necessary for this absorption and so is a large surface area. The capillary network and the lacteal carry absorbed nutrients away from the intestine.

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21
Q

How is SA of small intestine increased

A

SA of small intestine is increased by presence of villi which are the location of absorption of all the monomers produced by the digestive processes in the small intestine

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22
Q

Draw a villi

A

https://file.notion.so/f/f/e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560/a3c9169b-eaa0-4574-8edf-252c8f82d910/Untitled.png?id=e1002e02-d173-4da7-b315-fefc94ae5469&table=block&spaceId=e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560&expirationTimestamp=1714953600000&signature=u9xz3JW-SkUsQ15SgQUHhoCRBvdxVhbUviRY0Altsno&downloadName=Untitled.png

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23
Q

What are epithelial cells

A

epithelial cells are where absorption happens. each epithelial cell has projections of the plasma membrane that protrude into the lumen of the small intestine. the projections are called microvilli, which further increase the surface area

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24
Q

What do goblet cells do

A

goblet cells make mucus

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25
Q

What is the lamina propria

A

lamina propria is the connective tissue of the villus

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26
Q

Define absorption

A

absorption = taking in of digested food substances and minerals and vitamins from the lumen of the small intestine into the blood

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27
Q

Which molecules are directly absorbed by villi

A
  • molecules directly absorbed by the villi:
    • bases and phosphates from nucleic acids
    • fatty acids and glycerol
    • amino acids
    • monomeric carbohydrates, like fructose, glucose, galactose, and ribose
  • vitamins and minerals in food can be absorbed without further digestion.
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28
Q

What are the end products of digestion used for

A

once end products of digestion are distributed around the body through the circulatory system, they can be used by cells for anabolic processes or for respiration. these uses are called assimilation

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29
Q

What happens to contaminants in the blood stream

A
  • food might have contaminants or poisons which contain ethanol (including alcohol, beer, or spirits)
  • most contaminants can pass directly into the blood. the liver can detoxify some of them. but if they can’t be broken down by the liver, they can be secreted in the urine
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30
Q

What happens to medical drugs in the digestive system

A

most medical drugs are taken directly into the blood and broken down by the liver

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31
Q

What are microvilli

A

microvilli are hairlike folds in the membrane of the epithelial cells of the villus, which is where absorption takes place by means of facilitated diffusion, passive, and active transport

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32
Q

What two pathways can absorbed molecules follow

A

to be absorbed into blood, molecules have to pass into capillaries of the villus. fats are absorbed into the lymph, which circulates in the lacteal in the centre of the villus.

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33
Q

What is the process to be absorbed into the body

A
  1. substances to be absorbed move from the lumen into the epithelial villi
  2. amino acids and monosaccharides move from villi into capillaries and monoglycerides move into the lacteals
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34
Q

Define lacteal

A

Lacteal is the specific term for the lymph system

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35
Q

What are the four modes of absorption in the digestive system and when are they used

A
  1. Simple diffusion — when molecules are small and hydrophobic so they can pass through the phospholipid bilayers. this occurs usually with the products of lipid digestion
  2. facilitated diffusion — fructose, glucose, and hydrophilic monomers are moved by protein channels. This still requires a concentration gradient
  3. Active transport — needed when concentrations are lower in the lumen of the small intestine. movement needs to occur against a concentration gradient. glucose, amino acids, and some mineral ions are transported out of the lumen in this way, which needs ATP. the cells of the epithelium have many mitochondria that can synthesis ATP for this process
  4. Pinocytosis — draws in small droplets of liquid surrounded by a small section of the phospholipid membrane. most likely to occur with fat droplets in the lumen of the small intestine
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36
Q

How does starch get digested

A
  • starch digestion starts when you start chewing your food
  • amylase is an enzyme present in saliva
  • once saliva and food have been mixed, amylase starts to break down the alpha-1, 4 glycosidic bonds that connect glucose monomers in amylose and amylopectin. 1 and 4 refer to the carbon atoms in the glucose molecules that are joined by the bond
  • end products of starch breakdown by amylase are maltose, a dimer of glucose connected by a-1, 4 bonds, and maltotriose, which is made of three glucose molecules connected by a-1, 4 bonds
  • amylopectin also has a-1,6 glycosidic bonds. but those can’t be broken by amylase
  • branching of polymers are caused by the a-1,6 glycosidic bonds in amylopectin molecules
    • after the initial catalytic breakdown by amylase, di- and tri- saccharides from starch molecules are still too big to pass through membranes, so they need to be further broken down into monomers (monosaccharides) before absorption
  • what enters the small intestine from starch is a mixture of maltose, maltotriose, and dextrins
  • three enzymes immobilised in the epithelial cells of the small intestine, maltase, glucosidase, and dextrinase, break down these three molecules into glucose, which can be absorbed by villi
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37
Q

What are dextrins

A
  • dextrins — small polymers with the a-1,6 glycosidic bonds.
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38
Q

What happens to excess glucose

A

any excess glucose is taken by the liver and converted into glycogen and converted into glycogen, the animal equivalent of starch

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39
Q

What is dialysis tubing

A

dialysis tubing (AKA Visking tubing) is partially permeable cellulose tubing with microscopic pores that lets water, small molecules, and ions to pass through freely, but doesn’t allow the movement of large molecules. dialysis tubing is used in separation techniques. dialysis enables the removal of small molecules from macromolecules in solutions based on differential diffusion

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40
Q

Define the term dialysis

A

dialysis — separation of smaller molecules from larger molecules in solutions by selective diffusion through a partially permeable (selectively permeable/semipermeable) membrane

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41
Q

How is dialysis tubing used as a model of the small intesting

A
  • the medium outside representing the blood into which digested products are absorbed
  • tubing represents the epithelium of the small intestine
  • the high concentration of glucose solution inside the tubing is what is usually observed after a starchy meal has been fully digested
  • since the size of glucose molecules is small enough to pass through the pores of the tubing, it will diffuse from a region of higher concentration (in the tubing) to a region of lower concentration (in the beaker)
    • movement of glucose mimics absorption of glucose via the epithelial cells
  • if the water in the beaker was tested for glucose, the result would be positive since the water mimics blood
  • if starch solution was added into the tubing through the capillary tube, and samples of water in the beaker were tested for presence of starch at intervals of 10 minutes, a negative result would always be found. starch molecules are too big to pass through the pores of dialysis tubing. same thing would happen in small intestine. starch and other complex undigested models aren’t absorbed
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42
Q

How can the presence of starch be tested

A
  • brownish-orange = no starch
  • black-blue = starch is present
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43
Q

What is a shortcoming of dialysis tubing

A

shortcoming of dialysis tubing is that it can only account for absorption by diffusion or osmosis, not by active transport

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44
Q

Who was william harvey and what did he do

A

Before Harvey’s Findings: Scientists followed Galen’s beliefs, who believed Arteries and veins were separate blood networks (except where connected via invisible pores), veins pumped natural blood (believed to be produced by the liver), and arteries pumped heat (produced by the heart) via the lungs (for cooling).

William Harvey: English physician who proposed arteries and veins were part of a single connected blood network, but did not know of the existence of capillaries. He also proposed arteries pump blood from the heart to the lungs and body tissues, and that veins return blood to the heart from the lungs and body tissues. This helped explain how body temperature and pH are stabilised in the process of homeostasis.

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45
Q

What is blood made of

A

Plasma, white blood cells, red blood cells, and platelets

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46
Q

Define blood plasms

A

Plasma: Liquid portion which carries dissolved substances such as proteins, hormones, carbon dioxide, glucose, and vitamins and minerals

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47
Q

Define white blood cells

A

White blood cells: part of the immune system, help defend body from disease. Process of phagocytosis to engulf foreign particles/microbes.

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48
Q

Define red blood cells

A

red blood cells: Contain iron-containing hemoglobin proteins to transport oxygen. Iron is recycled. Produced in bone marrow. No nuclei or mitochondria. Also able to pick up CO2 for removal. Bioconcave shape increases the sa:v for exchange of materials. Shape also allows for easier passage in capillaries.

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49
Q

Define platelets

A

platelets (cell fragments): involved in mechanisms that clot blood when blood vessels break. Injury triggers the production of fibrin. Fibrin forms a solid mesh to close the wound.

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50
Q

Define the heart

A

Definition: Four chambered organ consisting of two sets of atria and two sets of ventricles.

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51
Q

Define atria

A

Atria: Like reservoirs. Collect blood returning to the heart through veins.

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52
Q

Define ventricles

A

Ventricles: Like pumps. Expel blood from the heart at a high pressure through arteries.

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53
Q

Define systemic circulation

A

Systemic circulation: Process through which the left side of the heart pumps oxygenated blood around the body

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54
Q

Define pulmonary circulation

A

Pulmonary Circulation: Process through which the right side of the heart pumps deoxygenated blood to the lungs.

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55
Q

Define the myocardium

A

Myocardium: Thicker muscular wall on the left side of the heart, since it pumps blood further

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56
Q

Draw a heart diagram

A

https://file.notion.so/f/f/e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560/c5594793-fc0c-4983-b6f6-933eb00d61f2/Untitled.png?id=7f5af9ad-2e13-4328-95cb-4ab89d97d7ef&table=block&spaceId=e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560&expirationTimestamp=1714953600000&signature=zrSHv7-mZBUvDccta1FlY4qv0MhYBCugR_NgbyS5q1g&downloadName=Untitled.png

https://file.notion.so/f/f/e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560/0325a711-2536-45d3-971e-ed30510eaea7/Untitled.png?id=ea874349-9121-4314-93e2-146285097bea&table=block&spaceId=e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560&expirationTimestamp=1714953600000&signature=QL37OCvOTtJ-_4uyZNIPvvYyNzmj2vWyh2Glr-94YIk&downloadName=Untitled.png

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57
Q

What are the four heart chambers

A
  • Two atria (sing. atrium) are smaller chambers near the top of the heart that collect blood from the body and lungs. They pull blood into the heart.
  • Two ventricles are larger chambers near the bottom of the heart that pump blood to the body and lungs. They push blood from the heart.
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58
Q

What are the heart valves

A

Heart Valves(ensure one way flow):

  • Tricuspid and bicuspid Atrioventricular valves (between atria and ventricles): bicuspid valve on the left side, tricuspid valve on the right side. Connect atriums to ventricles.
  • Pulmonary and aortic Semilunar valves (between the ventricles and arteries): Aortic valve on left side, pulmonary valve on right side. Connect the ventricle to artery.
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59
Q

What are the blood vessels

A
  • Vena cava (inferior and superior) feeds into the right atrium and returns deoxygenated blood from the body
  • Pulmonary artery connects to the right ventricle and sends deoxygenated blood from the heart to the lungs
  • Pulmonary vein feeds into the left atrium and returns oxygenated blood to the heart from the lungs
  • Aorta extends from the left ventricle and sends oxygenated blood around the body
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60
Q

Give the steps of circulation

A
  1. Right side of the heart (Pulmonary circulation)
    1. Blood enters the heart through the inferior and superior vena cava, with oxygen-poor blood from body tissues flowing into the right atrium
    2. The atrium contracts, and blood flows from the right atrium into the right ventricle through the open tricuspid valve
    3. When the ventricle is full, it begins contraction. Increased pressure of blood against the tricuspid valve forces it shut, preventing blood from flowing backwards into the atrium
    4. As the ventricle contracts, blood leaves the heart through the pulmonary valve into the pulmonary artery and flows to the lungs where it’s oxygenated.
  2. Left side of the heart (Systemic circulation)
    1. Pulmonary vein carries oxygen-rich blood from the lungs into the left atrium of the heart
    2. The atrium contracts and blood flows from the left atrium into the left ventricle through the open bicuspid (aka mitral) valve
    3. when full, the ventricle begins to contract. The increased blood pressure against the bicuspid valve causes it to close, preventing blood from flowing backwards into the atrium while the ventricle contracts.
    4. As the ventricle contracts, blood leaves the heart through the aortic valve, into the aorta and to the blood.
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61
Q

What signals regulate the heart rate

A
  • Nerve signals from the brain can trigger rapid changes
  • endocrine signals can trigger more sustained changes
  • changes to blood pressure levels or CO2 concentrations (and therefore also blood pH) will trigger changes in heart rate
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62
Q

What controls the pacemaker

A

pacemaker is under autonomic control from brain, specifically the medulla oblongata (brain stem)

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63
Q

What regulates heart rate

A
  • Two nerves connected to the cardiovascular centre in the medulla oblongata in the brain, can regulate heart rate by signalling to the SA node to either speed it up or slow it down.
    • The cardiac accelerator nerve tells the heart to beat faster.
    • The vagus nerve tells the heart to slow down
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64
Q

What does the cardio vascular centre do

A

Cardio vascular centre monitors the blood pressure, pH, and carbon dioxide concentration of blood, to determine whether impulses should be sent along the cardiac accelerator nerve or vagus nerve.

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65
Q

Why is the speed that the heart slows down after activity a measure of fitness

A

Application: Increased activity means more respiration, causing a greater need for oxygen and increased production of waste products (i.e. CO2). Increased CO2 in the blood will decrease the pH, which will make the cardiovascular centre send impulses along the cardiac accelerator nerve to the sinoatrial node to increase heart rate. As the heart pumps faster, more oxygen is sent to body tissue, and more carbon dioxide is removed. Once activity stops, impulses are sent along the vagus nerve. The speed at which the heart rate slows down is a measure of your fitness.

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66
Q

Define Hormones

A

Hormones Definition: Chemical messengers released into the bloodstream that act specifically on distant target sites (i.e. the heart)

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67
Q

What is adrenaline

A

Adrenaline (aka epinephrine)(called the ‘flight or fight’ hormone) is a hormone secreted by the medulla of the adrenal glands located above the kidneys. Strong emotions can cause it to be released into the bloodstream. It increases heart rate by stimulating the SA node to emit electrical signals at a faster rate, as well as increasing the conduction speed of impulses generated by the SA and AV nodes. Other than that, it also increases muscle strength, blood pressure, and sugar metabolism, to prepare the body for immediate action of vigorous physical activity.

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68
Q

Define atheromas

A

Atheromas definition: Fatty deposits caused by high blood concentrations of low density lipoproteins (LDL) in the arterial wall next to the endothelial cells.

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69
Q

Define thrombosis

A

Thrombosis: Forming of a clot in the blood vessel that can entirely block the blood vessel. If the blocked artery happens to be a coronary artery, the cells in that part of the heart will die resulting in a myocardial infarction (heart attack).

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70
Q

Define coronary arteries

A

Coronary arteries: Blood vessels surrounding the heart that nourish the cardiac tissue. If occluded, the region of heart tissue nourished by the artery will die and cease to function.

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71
Q

Define Angina

A

Angina: Pain caused by restricted flow of blood in a coronary artery due to the heart cells being deprived of oxygen and nutrients.

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72
Q

Define Atherosclerosis

A

Atherosclerosis definition: The hardening and narrowing of the arteries due to deposition of cholesterol.

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73
Q

Define stenosis

A

Stenosis definition: Narrowing or restriction of a tube or blood vessel or valve that reduces blood flow

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74
Q

Define atherosclerotic plaques

A

Atherosclerotic plaques: Lesions in the artery which form as the smooth lining progressively degrades

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75
Q

What is an acute myocardial infarction

A

Heart attack

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76
Q

What are the steps to a coronary occlusion

A
  1. Atheroma’s develop in the arteries and significantly cause stenosis in the lumen
  2. Restricted blood flow increases pressure in the artery, damaging the arterial wall
  3. Damaged region is repaired with fibrous tissue which significantly reduces the elasticity of the vessel wall
  4. Atherosclerotic plaques form as the lining of the artery degrades
  5. If a plaque ruptures, a blood clot is triggered, forming a thrombus which restricts blood flow
  6. If the thrombus is dislodged it becomes an embolus and can cause a blockage in a smaller arteriole
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77
Q

What are the consequences of Atherosclerosis and its treatment

A
  • blood clots which can cause CHD when occurring in coronary arteries. Myocardial tissue requires oxygen and nutrients transported via coronary arteries in order to function. If a coronary artery becomes completely blocked, an acute myocardial infarction will happen.
    • Treatment: By-pass surgery or creating a stent
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78
Q

What are the risk factors for a coronary occlusion

A GODDESS

A
  • Age: Blood vessels are less flexible when older
  • Genetics: Having hypertension predisposes individuals to developing CHD
  • Obesity: Being overweight places strain on the heart
  • Diseases: Certain diseases increase risk of CHD (i.e. diabetes which can cause high blood glucose concentrations). Certain infections with bacteria such as Chlamydia pneumoniae can also play a role.
  • Diet: Diets rich in saturated fats, salts, and alcohol increase the risk
  • Exercise: Sedentary lifestyles increase the risk
  • Sex: Males are at a greater risk due to lower estrogen levels
  • Smoking: Nicotine causes vasoconstriction, raising blood pressure
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79
Q

Draw a labeled diagram of the cardiac cycle

A

https://file.notion.so/f/f/e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560/0c94477e-92e8-48a4-bdbd-a310e94d31cd/Untitled.png?id=2d925fca-fd06-4ce7-81dc-d7215c42829d&table=block&spaceId=e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560&expirationTimestamp=1714953600000&signature=lkBFyR6HFU0NXDJwo9UDrEHE0GuDGLcFe7vIzo0GjU8&downloadName=Untitled.png

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80
Q

Define the cardiac cycle

A

Definition: Describes series of events taking place in the heart over duration of a single heart beat.

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81
Q

What are the two periods of the cardiac cycle

A

Systole and Diastole

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82
Q

Give the steps of the cardiac cycle

A
  1. Atrial contraction begins (atrial systole)
  2. Atria eject blood into ventricles (atrial systole)
  3. Atrial systole ends, AV valves close (sound)
  4. Isovolumetric contraction of the ventricles (ventricular systole)
  5. Ventricular ejection
  6. Semilunar valves close (second sound)
  7. Isovolumetric relaxation of the ventricles (ventricular diastole)
  8. AV valves open, passive ventricular filling occurs.
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83
Q

How are the atrium and ventricle affected by the different parts of the cardiac cycle

A
  • Atrial systole: Atrium contracts, ventricle relaxes
  • Ventricular systole: atrium relaxes, ventricle contracts
  • Diastole: Atrium relaxes, ventricle relaxes
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84
Q

What is the direction of blood flow throughout the phases of the cardiac cycle

A
  • Atrial systole: From atrium to ventricle
  • Ventricular systole: From ventricle to aorta
  • Diastole: Into atrium and ventricle
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85
Q

What happens to the valves through the different phases of the cardiac cycle

A
  • Atrial systole: AV open, aortic closed
  • Ventricular systole: AV closed, aortic open
  • Diastole: AV open, aortic closed
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86
Q

Define an isovolumetric contraction

A

Isovolumetric contraction: Term for an event occurring at the beginning of systole, during which the ventricles contract with no corresponding volume change. Makes the pressure in a heart chamber rise so blood can be forced into the artery in a one-way direction.

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87
Q

What happens during systole in the cardiac cycle

A
  • Returning blood will flow into the atria and ventricles since the pressure in them is lower due to the volume of blood
  • When the ventricles are almost 70% full, the atria will contract (atrial systole) which increases the pressure in the atria and forces blood into the ventricles
  • As the ventricles contract, the ventricular pressure exceeds the atrial pressure. AV valves then close to prevent backflow, making the first heart sound (ventricular systole)
  • with both sets of heart valves closed, pressure rapidly builds in the contracting ventricles (isovolumetric contraction)
  • When ventricular pressure exceeds blood pressure in the aorta, the aortic valve opens and blood is released into the aorta
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88
Q

What happens during diastole in the cardiac cycle

A
  • Ventricular pressure falls as blood exits the ventricle and travels down the aorta
  • When ventricular pressure drops below aortic pressure, the aortic valve closes to prevent back flow (second heart sound)
  • When ventricular pressure drops below the atrial pressure, AV valve opens and blood can flow from the atria to the ventricle
  • Aortic pressure remains high as muscle and elastic fibres in the artery wall maintain blood pressure
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89
Q

Define myogenic

A

Myogenic: The muscle can generate its own contractions. Signal for compression arises within the organ, originates in the muscle; not controlled by neurons. Neurons don’t need to tell it to compress.

  • Contraction of the heart is myogenic, meaning signal for cardiac compression arises within the heart itself
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90
Q

What are the steps to a heart beat

A
  1. Sinoatrial node sends out an electrical signal that stimulates contraction as it’s propagated through the walls of the atria
  2. Signal passes through the interatrial septum to reach the atrioventricular node.
  3. Signal is relayed from the AV node through a bunch of His located in the interventricular septum to the top of the ventricle (top of the heart/apex is the bottom-most part where two ventricles meet in a point-like shape)
  4. At the top of the ventricles, the signal spreads from the bundle of His (aka atrioventricular/AV bundle) to the ventricles through the Purkinje fibres located in the wall, causing ventricular contraction.
    - These events ensure there’s a delay between the atrial and ventricular contractions, resulting in two heart sounds. This allows time for the ventricles to fill with blood, following atrial contractions to maximise blood flow.
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91
Q

What is the myocardium

A

Myocardium Definition: Heart muscle tissue

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92
Q

Define the sinoatrial node

A

Sinoatrial Node: Specialised cluster of cardiomyocyte cells in the wall of the right atrium which direct contraction of heart muscle cell. Initiates each heartbeat and sets the heart rate, so it’s often called the primary pacemaker. ‘Fires’ (sends electric signals) at regular intervals to cause the heart to beat with a rhythm of 60-70 beats per minute for a healthy, resting heart.

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93
Q

What natural pacemakers do we have

A
  • Normal Sinus Rhythm: 60-100 bpm Cardiac Contractions
  • If SA Node fails, second pacemaker AV Node maintains contractions at 40-60 bpm
  • If SA Node and AV Node fail, tertiary pacemaker which is a bundle of His may coordinate contractions at rate of 30-40 bpm
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94
Q

What is the structure of an artery

A

Arteries have thick walls and narrow lumens because they transport blood at high pressure
Inside to outside:
* Tunica media (smooth mucles
* Tunica intima (endothelial cells)
* Tunica externa (elastin and collagen)

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95
Q

What is the structure of veins

A

Veins have thin walls with wide lumens and valves because they transport blood at low pressure
Inside to outside:
* Tunica media (smooth muscle)
* Tunica intime (endothelial cells)
* Tunica externa (elastin and collagen)

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96
Q

What is the structure of capillaries

A

Capillaries have walls that are only a single cell thick because they exchange materials between blood and tissue

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97
Q

What is the difference in functions of the three vessels

A
  • Arteries send blood from the heart
  • Veins send blood to the heart
  • Capillaries allow material from blood to exchange with tissues
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98
Q

What is the difference in pressure of the three blood vessels

A
  • Arteries have low pressure
  • Veins have high pressure
  • Capillaries have low pressure
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99
Q

Difference in lumen diameter between the 3 blood vessels

A
  • Arteries have narrow lumens
  • Veins have wide lumens
  • capillaries have extremely narrow lumens (1 cell/5 micrometres wide)
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100
Q

Difference in wall thickness between the blood vessels

A
  • Arteries have thick walls
  • Veins have thin walls
  • Capillaries have extremely thin walls (single cell thick)
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101
Q

Difference in wall layers between three blood vessels

A
  • Arteries have the layers tunica adventitia, tunica media, and tunica intima
  • Veins have the layers tunica adventitia, tunica media, and tunica intima
  • Capillaries have one layer of endothelial cells
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102
Q

Difference in tunica media between three blood vessels

A
  • Arteries: Thicker
  • Veins: Thinner
  • Capillaries: Absent
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103
Q

Difference in Muscle and Elastin fibres of three blood vessels

A
  • Arteries have thick layers
  • Veins have thin layers
  • Capillaries have none
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104
Q

Difference in valves of three blood vessels

A
  • Arteries have no valves
  • Veins have valves at intervals
  • Capillaries have no valves
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105
Q

Difference in diameter between three blood vessels

A
  • Arteries can be greater than 10mm
  • Veins can be greater than 10 mm
  • Capillaries are between 2 and 10 micrometers
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106
Q

What is the function of arteries

A

Function: To convey blood at high pressures from the heart to the tissues of the body and lungs

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107
Q

What is the aorta

A

Aorta: Main and biggest artery which connects the heart with the rest of the body. It exerts a systolic pressure of 120-200 mm Hg.

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108
Q

What is systolic blood pressure

A

Systolic blood pressure: Highest pressure experience by arteries when the heart contracts

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109
Q

What is vasoconstriction

A

Process where circular muscles around the arteries resist the outward pressure and constrict during systolic blood pressure.

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110
Q

What is diastolic blood pressure

A

Lowest pressure experienced by arteries when heart relaxes between beats

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111
Q

What is vasodilation

A

Process where the smooth muscles surrounding arteries relax during diastolic blood pressure

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112
Q

What are arterioles

A

Smaller forms of arteries that branch off to supply blood to organs, limbs, etc. They have a higher muscle density and are more susceptible to the hormonal and nervous control of vasoconstriction and vasodilation.

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113
Q

What is the stroke volume

A

Volume of blood pumped out of the left ventricle in the heart during each heartbeat/contraction

114
Q

What is cardiac output

A

Volume of blood the heart pumps through the circulatory system in a minute

115
Q

What is the importance of vasodilation and vasoconstriction

A

Note: Vasoconstriction and vasodilation directly control the flow of blood through the body. They also play a role in regulating body temperature and are involved in slowing down the flow of blood when someone is severely wounded.

116
Q

What is the structure of an artery

A
  • narrow lumen to keep high blood pressure (80-120 mmHg)
  • thick wall with outer layer of collagen to prevent artery from rupturing under high pressure
  • Arterial wall has inner layer of muscle and elastic fibres to maintain pulse flow (can contract and stretch)
  • Muscle and elastic fibres help maintain blood pressure between pump cycles

Layers:

  1. Tunica intima: Part facing the lumen is lined with endothelium. In direct contact with the blood in the lumen. Includes endothelium that lines the lumen of all vessels and forms a smooth, friction-reducing lining.
  2. Tunica media: Thickest layer. It’s the middle coat made up of smooth involuntary muscle cells and elastic fibres arranged in three layers.
  3. Tunica adventitia (AKA Tunica externa): Outermost coat. Tough layer made of loosely woven collagen fibres that protect the blood vessel and anchor it to surrounding structures.
117
Q

Describe the pressure of blood in arteries over time

A

Blood flows in bursts, and not continuously.

118
Q

Define pulses

A

Pulses: Repeated surges in the arteries through which blood flows from the heart upon ventricular contraction. The blood flows at a high pressure, and the muscle and elastic fibres help maintain the pressure between pumps.

119
Q

Define arterial muscle fibres

A

Muscle Fibres: Help make a rigid arterial wall capable of withstanding the high blood pressure without rupturing. They can also contact to narrow the lumen, increasing the pressure between pumps, helping maintain blood pressure through the cardiac cycle.

120
Q

Define arterial elastic fibres

A

On the arterial wall and are formed from elastin protein, which are stretched at every heartbeat when there’s high pressure.

121
Q

Define elastic recoil in artery’s

A

Artery returns to its normal size when pressure exerted on arterial wall is returned to the blood. Helps push blood forward through the artery, and maintain arterial pressure between pumps.

122
Q

What are capillaries

A

Capillaries are found when arteries split into arterioles, which then split into capillaries, decreasing arterial pressure since the total vessel volume is increased. Capillaries then fuse together to form venules, which fuse together to form veins. Arteries branching into capillaries ensures blood is moving slowly, and all cells are near a blood supply.

123
Q

What is the function of capillary’s

A

Function: Exchanging materials between cells in tissues and blood travelling at low pressure through diffusion or active transport. After this material exchange has occurred, tissue fluid is mostly reabsorbed into capillaries, which drains into venules.

124
Q

What is the structure of capillaries

A
  • Small diameter (5 micrometres wide), allowing passage of only a single red blood cell at a time, resulting in optimal exchange
  • Capillary wall is made of a single layer of cells, to minimize the diffusion distance for permeable materials
  • Surrounded by a basement membrane, which is permeable to necessary materials
  • Can contain pores to further help in transportation of materials between tissue fluid and blood
  • Rather leaky walls, allowing easy exchange of materials

Tissue fluid/Interstitial Fluid: Liquid part of blood that passes through the capillary wall. Mainly composed of water, sugars, salts, fatty acids, amino acids, coenzymes, hormones, and waste products from the cells.

How capillary structure changes depending on its location in the body and specific role:

  • A capillary wall might be continuous with endothelial cells held together by tight junctions to limit the permeability of large molecules
  • In tissues specialized for absorption (intestines, kidneys, etc.), the capillary wall might be fenestrated (have pores)
  • Some capillaries are sinusoidal and have open spaces between cells and be permeable to large molecules and cells
125
Q

Describe blood flow in capillaries

A
  • Blood flows through capillaries slowly and at low pressure, to allow for maximal material exchange
  • high blood pressure in arteries is dissipated by extensive branching of the vessels and the narrowing of the lumen
  • Higher hydrostatic pressure at the arteriole end of the capillary forces material from the bloodstream into the tissue fluid. material leaving the capillaries at body tissues include oxygen and nutrients which are needed by cells for respiration.
  • lower hydrostatic pressure at the venule end of capillary lets materials from the tissues to enter the bloodstream. materials that enter capillaries at body tissues are carbon dioxide and urea (wastes produced by the cells)
126
Q

What is the function of veins

A

Function: Collecting blood from the tissues and conveying it at low pressure to the atria of the heart.

127
Q

What is the structure of veins

A
  • Very wide lumen to maximise blood flow for more effective return
  • Thin wall with less muscle and elastic fibres, since blood flows at a very low pressure (~5–10 mmHg)
  • Since pressure is low, veins have valves to prevent backflow and stop the blood from pooling at the lowest extremities
128
Q

Describe the flow of blood in veins

A
  • Low blood pressure which can make it hard for blood to move against the force of gravity. Veins have numerous one-way valves in order to maintain blood circulation by preventing backflow
  • Veins typically pass between skeletal muscle groups, which facilitate venous blood flow via periodic contractions. When skeletal muscles contract, they squeeze the veins and cause blood to flow from the site of compression. Veins typically run parallel to arteries, and a similar effect can be caused by the rhythmic arterial bulge created by a pulse.
  • Blood flow in veins is helped by pressure exerted by skeletal muscles. When you move, the muscles squeeze the veins like a pump. Patients that are immobilised for long periods of time or are in a coma need manual manipulation of the muscles to help the flow of blood, prevent blood boils, and bed sores.
  • Valves close to prevent backflow. Valves in veins ensure that blood flows in one direction only, towards the heart, by preventing backflow.
129
Q

What are the sections of the immune system

A
  • Non-specific immune system (involves phagocytes)
  • Specific immune system (lymphocytes + antibodies)
130
Q

What is the body’s primary defence

A

Primary defence against infection: Preventing entry of organisms and viruses that cause disease

Method of Primary Defence: Skin, Mucous membranes

131
Q

What is the structure of the skin

A
  • Pores for sweating
  • hair follicles
  • sebaceous glands (produce oils called sebum to keep skin supple and at a slightly lower pH. oil and low pH both act as growth inhibitors for certain bacteria.)
132
Q

What are mucous membranes

A

Mucous membranes: Protect body in parts open to outside world. Made up of a surface layer of epithelial cells over a deeper layer of connective tissue. Produce a sticky mucus for lubrication and protection, that contains glycoproteins and lysozymes, which are enzymes that attack the bacterial cell walls. Both of them have antiseptic properties (properties discouraging or preventing the growth of microorganisms). The mucus itself also forms a barrier and traps organisms which can be killed by white blood cells found in the mucous membranes.

133
Q

Outline the process of blood clotting

A
  1. Blood vessel is damaged (initial cut)
  2. Platelets release chemicals
  3. First reaction triggers second reaction by producing a required chemical for the second reaction
  4. Continues through series of several reactions with up to 12 factors. Each reaction takes an inactive protein in blood called a clotting factor and activates it
  5. Conversion of fibrinogen to insoluble fibrin. Reaction is catalyzed by enzyme ‘thrombin’ which itself was activated through the cascade of reactions
  6. Network of fibres that trap red blood cells and platelets form a soft scab to prevent the entry of pathogens into the body as well
  7. Scab hardens, forming protective layer
  8. Skin heals under protective layer
134
Q

Define fibrinogen

A

Fibrinogen: Soluble and inactive clotting factor in blood

135
Q

What is the most common cause of hemophilia

A

Most Common Cause: Missing clotting factor VIII (7)

136
Q

What is a thrombus

A

Thrombus: Clot formed in a vessel which remains where it was formed

137
Q

What is a coronary thrombus

A

Thrombus formed in coronary artery

138
Q

Define atherosclerosis

A

Atherosclerosis: Narrows lumen of arteries, slows down blood flow, ultimately increasing chance of a thrombus occluding a coronary artery, leading to certain parts of the heart not receiving oxygen and nutrients, causing that part of the heart to die, and a heart attack.

139
Q

Define angina

A

Angina: Chest pain caused by a thrombus reduces the amount of blood reaching heart muscles instead of stopping it completely, causing heart muscles to not get enough oxygen-rich blood.

140
Q

What is the process of thrombosis of coronary arteries

A
  1. Plaque in artery walls rupture lining of the vessel
  2. Clot that began at site of rupture can grow larger and completely block artery
141
Q

What factors increase the risk of clot formation

A
  • smoking
  • obesity
  • hypertension
  • diabetes
142
Q

What is our second line of defence

A

Second Line of defence by immune system is activated when pathogens enter the body and cause disease.

Function: Recognizes proteins and other molecules on pathogens as foreign, triggering an immune response.

143
Q

Define an antigen

A

Any molecule that enters the body and triggers an immune response

144
Q

Define a white blood cell

A

Also known as leukocytes. Blood cells with immune function.

145
Q

What are the types of leukocytes

A

Macrophages aka phagocytes

146
Q

Define a pathogen

A

Pathogen: Disease-causing virus/microorganism. Examples: viruses, bacteria, protozoans, prions, fungi.

147
Q

Define a macrophage/phagocytes

A

AKA: Phagocytes because one main function is phagocytosis

Function: Engulf pathogen that entered the body. Once inside the phagocyte, enzymes secreted by the lysosome will digest the pathogen.

Location: Lymph nodes or blood

148
Q

Define amoeboid motion

A

Amoeboid motion: Process of movement for phagocytes, which involves the extension of pseudopods.

149
Q

How do phagocytes showcase non-specific immunity

A

Phagocytes can squeeze past leaky endothelial cells of capillaries and invade tissue where infection occurs, i.e., in a small wound in the skin. This is an example of non-specific immunity to diseases, since phagocytes can respond equally well to a variety of organisms.

150
Q

What is the sequence of destruction of pathogens by phagocytes

A
  1. Chemical recognition
  2. amoeboid motion (extension of pseudopodia)
  3. endocytosis
  4. enzymatic digestion
151
Q

Define an antibody

A

Antibody: Large protein with variable regions produced by the body that will bind to an antigen. Molecules produced by immune system in response to the detection of antigens. A Protein molecule made by lymphocytes with a specific structure. They recognise antigens

152
Q

Define an antigen

A

A molecule or entity that enters the body and triggers an immune response. Often found on the surface of a pathogen.

153
Q

Define a lymphocyte

A

Lymphocyte: Type of white blood cell responsible for production of antibodies

154
Q

Define a B lymphocyte

A

B lymphocyte: Also known as a B cell. Have capability to recognize millions of antigens through the receptors on their surfaces, which are essentially an antibody attached to its cell surface as an integral protein so that the antigen binding site points outwards.

155
Q

What happens when a B cell recognizes an Antigen

A
  1. Clonal selection: B cell divides repeatedly through mitosis to make many copies of the B cell that can recognise the antigen
  2. Most B cells become plasma cells which make and secrete large quantities of the antibody for the antigen to circulate in the blood
    1. Antibodies may bind to the antigen, allowing phagocytes to recognize then destroy the pathogen
    2. Antibodies may bind to proteins in the coat of a virus, preventing the virus from entering the other cells
  3. Some B cells become memory cells, a long-lived pool of cells capable of responding quickly to the antigens in case of re-encounter. They remain in the bloodstream and lymph nodes for a long period of time, allowing the next antibody production be quicker. The next antibody production is called specific immunity.
  4. When infection is overcome, the number of plasma cells which produce the antibodies will decrease
156
Q

Define a T lymphocyte

A

T Lymphocyte: Also called a T helper cell. Is important in helping B cells complete their function of making antibodies. Once antigen is recognized by T helper cell, the immune system is activated to fight against the antigen. It triggers production of antibodies and activates macrophages and killer T cells, which engulf and destroy the antigen.

157
Q

What is an APC

A

APC: Antigen Presenting Cell which is a special type of white blood cell that traps the antigen and presents it to the T helper cell.

158
Q

Define HIV

A

Definition: Human immunodeficiency virus. Infects and stops T helper cells from functioning. Infected T helper cells are destroyed. Since they’re needed to activate B cells to produce antibodies, infections with HIV cause a loss in the ability to produce antibodies, which can lead to the development of AIDS (acquired immune deficiency syndrome). HIV Causes an overall reduction of active lymphocytes, including T cells and B cells. Activated T cells decrease as infected T helper cells are destroyed and activated B cells decrease since there are less T helper cells to cause their activation.

Composition: Retrovirus with RNA as genetic material. Once it infects a cell through the proteins on its surface, it makes a DNA copy from its RNA, with the help of enzyme called reverse transcriptase. cDNA produced is inserted into the host cell’s genome.

Cure: Infection can be slowed down or stopped with the use of antiviral drugs targeting reverse transcriptase activity.

159
Q

What are the symptoms of HIV

A
  • High fever
  • Chills
  • Pneumonia
  • Headaches
  • Loss of appetite
  • Mood swings
  • cough with sputum or phlegm
  • Shortness of breath
  • Pleuritic chest pain
  • Hemoptysis
  • High heart rate
  • Joint pain
  • Nausea
  • Vomiting
  • Clamminess
  • Blueness
  • Muscle fatigue
  • Muscle aches
160
Q

What happens if HIV is left untreated

A

Will develop into AIDS, which is a range of diseases normally only seen in severely immuno-suppressed patients, i.e. fungal pneumonia and Kaposi sarcoma (form of skin cancer).

161
Q

How is HIV transmitted

A
  1. Sexual intercourse
  2. Transfusion of infected blood
  3. Sharing hypodermic needles by drug users
  4. Pregnancy, birth, or breastfeeding (mother to child)
162
Q

Define antibiotics

A

Any substance produced by a microorganism that can inhibit growth of other microorganisms. Normally require low concentrations to be effective, however, with uncontrolled use in hospitals and agriculture, resistance has become widespread and routinely effective concentrations must be increased to higher dosages.

163
Q

How do antibiotics function

A

Block processes in prokaryotic but not eukaryotic cells. Target bacterial cell wall and membrane formation, ribosome function, or DNA replication, transcription, and translation slowing down or stopping growth of bacteria. Can be used to treat bacterial infections in humans and animals without harming body cells, as they are eukaryotes.

164
Q

Whats the relation between fungi and antibiotics

A

Fungi: Most antibiotics are isolated from saprotrophic fungi, since fungi often secrete antibiotics to inhibit growth of competing bacteria. An example is penicillin.

165
Q

What is the relation between viruses and antibiotics

A

Viruses: Viruses are not affected by antibiotics, since they are not living and do not have their own metabolic processes. Viruses infect living cells and make use of the cells own metabolic processes to spread the viral infection.

166
Q

How does resistance to antibiotics change over time

A

Natural selection favours the spread of resistance, so if a mutation causing resistance to an antibiotic occurs in a bacterium, after several generations a strain of bacteria will evolve with genes that have resistance to the antibiotic. This has occurred many times with many different type of bacteria. However, some bacteria have exchanged genes coding for antibiotic resistance and developed resistance to several. Some bacteria have become resistant against all known antibiotics, making them lethal. These include tuberculoses and some STDs (i.e. gonorrhoea and chlamydia).

167
Q

What is chlamydia

A

Chlamydia causes a build-up of scarring that can block the fallopian tube and prevent fertilisation

168
Q

How was penicillin discovered and tested

A

Discovered by Fleming in 1928

Testing: Done to ascertain if the molecule would be effective in fighting human infections by Howard Florey and Ernst Chain in the early 1930s.

  1. On Mice
    1. They infected eight mice with Streptococcus, a bacterium causing pneumonia in mice. They were kept under identical conditions, but four were given an injection of penicillin. The ones injected stayed alive, but the others died within 24 hours. This gives a strong indication that penicillin may have played a role in the recovery of mice
  2. On humans
    1. proceeded to test penicillin on very sick patients with infections. Most of them survived
  3. Commercial production
    1. In the 1940s and allowed testing on more and more patients, eventually confirming it as a very effective weapon against infection
169
Q

Define physiological respiration

A

Transport of oxygen to cells within the tissues where energy production occurs. It is comprised of three distinct processes: Ventilation, gas exchange, and cell respiration.

170
Q

Define ventilation

A

The active exchange of air between the atmosphere and the lungs. In humans, it is achieved by the act of breathing.

171
Q

Define gas exchange

A

The passive exchange of oxygen and carbon dioxide between the alveoli and bloodstream via passive diffusion.

172
Q

Define cell respiration

A

The release of ATP from organic molecules. It’s enhanced by the presence of oxygen.

173
Q

What is gas exchange dependent on

A
  • concentration gradient of oxygen
  • concentration gradient of carbon dioxide
174
Q

What is ventilation

A

Definition: The exchange of air between the atmosphere and the lungs. In humans, it is achieved by the act of breathing: bringing fresh air into your alveoli and removing the stale air.

Purpose: Maintaining a concentration gradient of oxygen and carbon dioxide in between air in the alveoli and blood flowing in adjacent capillaries. The longer air remains in the alveoli, the lower the concentration of oxygen in the air, decreasing the concentration gradient that drives the diffusion of oxygen into the blood. Ventilation removes the lower oxygen air and replaces it with fresh higher oxygen air. This ensures oxygen continuously diffuses into the blood from the alveoli. The exchange of gases that occurs at the alveoli is called gas exchange and is directly dependent on ventilation. gas exchange is a passive process.

175
Q

Define breathing/ventilation rates

A

The number of breaths, including both inhalation and exhalation, taken per minute. Between 12-20 times/minute is normal for adults, but can increase to 30-40 times/minute when running at full speed.

176
Q

What happens during inspiration and expiration

A

Inspiration:
* External intercostal muscles contract
* internal intercostal muscles relax
* Diaphragm contracts (drops)
* Abdominal muscles relax
* Pressure in lungs decreases while volume increases, air enters

Expiration:
* Internal intercostal muscles contract
* External intercostal muscles relax
* Diaphragm relaxes (rises)
* Abdominall muscles contract
* Pressure in lungs increases while volume decreases, air escapes

177
Q

What are the two gas laws

A
  • The pressure of a gas is directly related to the number of molecules that occupy a certain volume(when volume is larger the pressure is lower). The flow of gas then is always from an area of high pressure to an area of low pressure.
  • When a gas is compressed, its volume decreases and pressure rises.
178
Q

What is the pathway for oxygen entering the body

A

mouth/nasal passage → trachea → two bronchi → bronchioles → alveoli (oxygen, reverse for CO2)

179
Q

What muscles are involved in ventilation

A
  • External intercostals contract to make the ribs move up and out during inspiration
  • To move ribs back down and in, the internal intercostals contract during expiration

These are antagonistic muscles. Diaphragm muscles are also antagonistic (contract to increase volume of thorax, other muscles contract to move diaphragm back up during exhalation).

180
Q

How are the lungs structured for ventilation

A

The lungs are a ventilation system, as they continually cycle fresh air into the alveoli from the atmosphere, meaning O2 levels stay high in alveoli, diffusing into the blood, while CO2 levels stay low, diffusing from the blood.

Structure: Large surface area to increase the overall rate of gas exchange

181
Q

Give the steps of the respiratory system

A
  1. Air enters through the nose or mouth and passes through the pharynx to the trachea
  2. Air travels down the trachea until it divides into two bronchi which connect to the lungs
  3. Right lung is composed of three lobes, while the left is only comprised of two (due to position of the heart)
  4. In each lung, bronchi divide into many smaller airways called bronchioles, increasing the surface area
  5. Each bronchiole terminates with a cluster of air sacs called alveoli, where gas exchange with the blood stream occurs.
182
Q

Define breathing

A

The active movement of respiratory muscles that enable the passage of air into and out of the lungs.

183
Q

What is the mechanism of breathing according to Boyle’s law

A

When gas is compressed (volume decreases), pressure rises. In the lungs, when breathing in, the thorax (chest) expands, and the pressure in the lungs is lowered, ensuring the thoracic pressure is lower than atmospheric pressure. This causes air to rush into the lungs. When breathing out, the thorax gets smaller, the pressure rises, and air is forced out of the lungs.

184
Q

What happens physically during breathing

A
  • Respiratory muscles contract to change the volume of the thoracic cavity, and hence alter the pressure in the chest. Since muscles only do work via contraction, different groups are required to expand and contract chest volume. Changing chest volume creates a pressure differential between the chest and atmosphere, with air then moving to equalise.
    • Muscles that increase the volume of the chest cause inspiration (since chest pressure<atmospheric pressure)
    • Muscles that decrease the volume of the chest cause expiration (since chest pressure>atmospheric pressure)
  • Atmospheric pressure is lower at high altitudes, meaning a greater increase in chest volume is required before a pressure differential is formed, making it harder to breathe at high altitudes
    • The body will adapt mechanisms to improve oxygen uptake under these conditions which is why athletes often undertake high altitude training prior to competitions
185
Q

What muscles are responsible for inspiration and what is the process

A

Responsible muscles: Diaphragm, external intercostals, some accessory muscles.

Process:
1. Diaphragm muscles contract, causing the diaphragm to flatten and increase the volume of the thoracic cavity
2. External intercostals contract, pulling ribs upwards and outwards (expanding chest)
3. Additional muscle groups might help pull the ribs up and out

186
Q

What muscles are responsible for and what is the process of expiration

A

Responsible muscles: Abdominal muscles, internal intercostals, accessory muscles

Process:
1. Diaphragm muscles relax, causing the diaphragm to curve upwards and reduce the volume of the thoracic cavity
2. Internal intercostal muscles contract, pulling ribs inwards and downwards, reducing breadth of chest
3. Abdominal muscles contract and push the diaphragm upwards during forced exhalation
4. Additional muscle groups help pull the ribs downwards

187
Q

Define lung cancer

A

Lung Cancer Definition: the uncontrolled proliferation of lung cells, leading to the abnormal growth of lung tissue (tumour). The abnormal growth can impact on normal tissue function, leading to a variety of symptoms according to size and location. The tumours can remain in place (benign) or spread to other regions of the body (malignant).

188
Q

Why is lung cancer the most common cause of cancer-related deaths

A
  • Lungs are vital to body function and thus the abrogation of their normal function is detrimental to health
  • Lungs possess a rich blood supply, increasing the likelihood of metastasis
189
Q

What are symptoms of lung fcancer

A
  • Coughing up blood
  • Cough that does not go away
  • Wheezing
  • Shortness of breath
  • Respiratory distress
  • Weight loss
  • Accumulation of fluid in the chest
  • Loss of appetite
  • Fatigue
  • Repeated problems with pneumonia or bronchitis
  • Can cause chest pain, difficulty swallowing, and heart complications, if the cancer compresses adjacent organs
190
Q

causes of lung cancer

A
  • Asbestos dust particles lodge in the lungs and can’t be broken down
  • Smoking
  • Passive smoking (second-hand smoking)
  • Air pollution (diesel exhaust fumes contain many carcinogens)
  • Radon gas: If there’s a higher concentration of Radon gas, it emits alpha particles, which can cause mutations when inhaled
191
Q

Define emphysema

A

Definition: Lung condition caused by the long-term exposure to cigarette smoke and other pollutants. It gives rise to an inflammatory response in the lungs, resulting in a narrowing of the small airways and breakdown of lung tissue. Alveoli also become less elastic, making ventilation more difficult. Also results in increased protease activity, which breaks down the alveolar wall, creating one larger air space instead of many tiny ones, reducing the surface area of the lungs and resulting in a smaller amount of oxygen reaching the bloodstream. The proteases are normally inhibited by alpha-1-antitrypsin.

Note: A small proportion of emphysema cases are due to a hereditary deficiency in alpha-1-antitypsin due to a gene mutation

192
Q

What are symptoms of emphysema

A
  • Shortness of breath
  • Phlegm production
  • Expansion of the ribcage
  • Cyanosis
  • Increased susceptibility to chest infections
193
Q

How does ventilation change in response to physical activity levels

A
  1. ATP production via cellular respiration produces carbon dioxide as a waste product, and may consume oxygen aerobically.
  2. Changes in blood CO2 levels are detected by chemo sensors in the walls of the arteries which send signals to the brainstem
  3. As exercise intensity increases, the demand for gas exchange, leading to an increase in levels of ventilation
194
Q

How does exercise influence ventilation

A
  • Increase ventilation rate: greater frequency of breaths allows for a more continuous exchange of gases
  • Increase tidal volume: Increasing the volume of air taken in and out per breath allows for more air in the lungs to be exchanged
195
Q

What are the methods to measuring ventilation

A
  • Simple observation (counting number of breaths per minute)
  • Chest belt and pressure meter (recording the rise and fall of the chest)
  • Spirometer (recording the volume of gas expelled per breath)
196
Q

Define spirometry

A

Spirometry definition: Involves measuring the volume/flow at which air can be inhaled or exhaled. A spirometer is a device that detects the changes in ventilation and presents the data on a digital display. A simpler method to perform spirometry involves breathing into a balloon and measuring the volume of air in a single breath (volume can be determined by submerging the balloon in water and measuring the volume displaced; 1ml=1 cm3).

197
Q

Define tidal volume

A

The amount of air that enters or leaves the lungs in a single breath at rest. Average tidal volume is 500 ml.

198
Q

Define alveolus

A

Definition: Air sacs of the lung where gaseous exchange takes place. Oxygen concentration in the alveoli is higher than the concentration of oxygen in the blood that flows past it. Carbon Dioxide however, is less concentrated in the alveoli and has higher concentrations in the blood.

199
Q

Draw a diagram of an alveoli

A

https://file.notion.so/f/f/e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560/ac522bb9-ca0d-43ab-be11-c38d232b544e/Untitled.png?id=e94dc201-a205-4d23-924a-6e0e2aa7ffa9&table=block&spaceId=e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560&expirationTimestamp=1715040000000&signature=KUU-M1UwBYb1cJx5VFXyZq8Rk5YzfJSLAyyEjn3P1f8&downloadName=Untitled.png

200
Q

What is the function of alveoli

A

Function: The gradient, the thin walls, and moisture of the alveoli and the short distance to the capillaries, facilitate gas exchange by diffusion. Each molecule diffuses based on its concentration gradient, not a constant amount.

201
Q

What is the strucutre of alveoli

A
  • Thin epithelial layer (one cell thick) to minimise diffusion distances for respiratory gases
  • Surrounded by rich capillary network to increase capacity for gas exchange in blood
  • Roughly spherical in shape, in order to maximise available surface area for gas exchange
  • Lined by a layer of liquid to create a moist surface conducive to gas exchange with the capillaries as dissolved gases are better able to diffuse into the bloodstream. It’s easier for oxygen to diffuse across the alveolar and capillary membranes when dissolved in liquid. However, the lining also creates a tendency for the alveoli to collapse and resist inflation.
202
Q

How does surfactant contribute to alveolis

A

https://file.notion.so/f/f/e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560/81ee79bf-ce68-4e28-a800-b21ffcf38e11/Untitled.png?id=f9c78589-9584-4641-af4d-f21528333166&table=block&spaceId=e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560&expirationTimestamp=1715040000000&signature=NAKA1BaxNnRFagYDzZcGrAax-bv8QZItIMCLfxkIW7M&downloadName=Untitled.png

203
Q

Define surface tension

A

Surface tension: The elastic force created by a fluid surface that minimises the surface area via cohesion of liquid molecules.

204
Q

What are the types of alveolar cells

A

Type 1 and Type 2 Pneumocytes

205
Q

What are pneumocytes

A

Alternative name: Alveolar cells

Definition: Cells that line the alveoli. Comprise of the majority of the inner surface of the lungs.

Types: Type I pneumocytes, type II pneumocytes

206
Q

What are type 1 pneumocytes

A
  • Function: Involved in process of gas exchange between alveoli and the capillaries
  • Structure: Squamous (flattened) in shape and extremely thin (0.15 micrometres), to minimise diffusion distance for respiratory gases
  • Connected by occluding junctions, preventing leakage of tissue fluid into the alveolar air space
  • Amitotic and unable to replicate
207
Q

What are type 2 pneumocytes

A
  • Function: responsible for secretion of pulmonary surfactant, which reduces surface tension in the alveoli. As an alveoli expands with gas intake, the surfactant becomes more spread out across the moist alveolar lining, increasing surface tension and slowing the rate of expansion, ensuring all alveoli inflate at roughly the same rate.
  • Structure: Cuboidal shape and many granules for storing surfactant components
  • Only comprise around 5% of the alveolar surface but are 60% of the total cells
  • Can differentiate into type 1 if required
208
Q

What is a pulmonary surfactant

A

Water-based solution containing phospho-lipoproteins. They create a moist surface inside the alveoli to prevent the sides of the alveoli from sticking to each other by reducing surface tension. It also increases the speed at which gases dissolve, helping gas exchange.

209
Q

What is the speed of nerve impulse

A

80-120 metres/second

210
Q

Draw a neuron

A

https://file.notion.so/f/f/e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560/d4056153-f786-4940-94b1-f11a3a0bb74c/Untitled.png?id=e986172d-f927-45fb-b107-15db9c32b3d8&table=block&spaceId=e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560&expirationTimestamp=1715040000000&signature=GnvAnxZiugu-P4OW2RIb94hRD28U0e6nDf42LfY-NeY&downloadName=Untitled.png

211
Q

What is a neuron

aka, amount, function

A

Alternative Name: Nerve Cell

Amount: 80-90 billion in a human body

Function: Transmitting signals in the form of electrical impulses

Nervous System: Used for communication throughout the body and communication within the brain, generating higher brain functions.

212
Q

What is the structure of neurons

A
  • Axons
    • Some are coated with a myelin sheath, which is an insulating layer that speeds up transmission of a nerve impulse. This is made of compacted layers of the Schwann cell membrane (mostly lipid, but also has several proteins. help maintain structure and compaction of myelin and adhesion of the sheath to the axon)
  • Gap between adjacent Schwann cells is called the node of Ranvier. A nerve signal propagated along a myelinated axon can move at speeds of up to 120 m/s, whereas in the case of an axon which isn’t myelinated, the speed can be as slow as 1 m/s. Myelin sheath forces nerve signals to jump from one node of Ranvier to the next, accounting for the faster speed of impulse transmission, called saltatory conduction of nerve impulses.
213
Q

What is a propagated signal

A

It moves down the length of the axon towards the terminals.

214
Q

What is the resting potential in a neuron

A

Definition: A Neuron has a sodium (NA+) and potassium (K+) ion gradient across the membrane. When a neuron isn’t transmitting a signal, it has more sodium on the outside than inside, and more potassium on the inside than outside. There are also some proteins with a negative charge located inside the neuron. The ion gradient causes an electrical imbalance, known as the resting potential.

Function: A Sodium-Potassium pump transfers potassium ions into the cell and sodium ions out (so dum get out). For every turn of the pump, 3 sodium ions are transferred out of the neuron, but only two potassium ions are transferred back into the neuron, resulting in an overall loss of positive ions and the development of the negative resting membrane potential of -70 mV.

Note: The membrane is more permeable to potassium ions than sodium ions.

Types of channels: Sodium and potassium ion channels are passive, since the movement is driven by the concentration gradient. Sodium potassium pump is active, requiring energy in the form of ATP to move the ions against their concentration gradient.

215
Q

What is the action potential of a neuron

A

When neurons send electrical messages it happens through a pattern of changes in the membrane potential. When stimulated, neuron can become depolarised. Depolarisation is caused be opening of sodium channels, allowing rapid influx of Na+ ions (passive movement) into the cell. Since there’s a concentration gradient across the membrane (more outside), this is a rapid change. Membrane potential of -70 mV changes quickly to positive value of around 30 mV. Once an area of the neuron is fully depolarised, the change in potential causes voltage-gated potassium channels to open. As a result of the channels opening, potassium ions that are at a higher concentration in the neurons diffuse out, and result in a decrease in membrane potential, which is a process called repolarisation. The potassium ions stay open until the potential becomes as negative as the resting potential. However, in many cases, the potential becomes more negative than the resting potential for approximately 2 ms, which is called hyperpolarisation. This is because not all potassium channels close immediately after the resting potential is reached. After hyperpolarization, that part of the neuron enters a refractory period and can’t be depolarised (to make an action potential) since the sodium channels are inactivated. Once depolarised to about -50 mV(the threshold potential), the depolarisation will rise rapidly to +30 mV, and the action potential will occur, meaning a nerve impulse is sent. Depolarisation over the threshold causes an action potential, called the all or nothing principle. If a neuron doesn’t reach a threshold potential of around -50 mV, the neuron won’t depolarise enough to send an impulse. If it reaches the threshold, there’s a positive feedback effect in the membrane, and nearby sodium channels open to further depolarise the neuron and instigate action potential.

Example: When touching something, the dendrites of a neuron in the tip of fingers will become depolarised

216
Q

How are neurons voltage-gated

A

Voltage-gated: The trigger to open the protein channels is a membrane potential of 30 mV.

217
Q

What is an oscilloscope trace of a neuron

A

Oscilloscope trace of neuron shows a graph of the membrane potential values in mV, as it would appear on the screen of an oscilloscope.

218
Q

What is an oscilloscope

A

Device that registers electrical voltages and displays them on a screen as time passes

219
Q

Define the threshold potential for a neuron

A

Threshold potential: Minimum level to which membrane potential must be depolarized to trigger an action potential. The threshold potential varies between -55 mV and -40 mV.

220
Q

Define the all or nothing principle for a neuron

A

All or nothing principle: Neurons can not be depolarised without the threshold potential of around -50 mV.

221
Q

How do depolarisation and repolarisation of a neuron happen

A

Depolarisation: Na+ channels open, Na+ diffuse to the inside of the neuron

Repolarisation: Na+ channels close and K+ channels open, allowing K+ to diffuse out

222
Q

Draw a membrane potential graph for a neuron

A

https://file.notion.so/f/f/e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560/c196bee0-fc22-4921-96cd-d826a83ea9e4/Untitled.png?id=f90c5b8a-11b5-4368-af73-bc92a12a2649&table=block&spaceId=e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560&expirationTimestamp=1715040000000&signature=IdbkzSRamLvwgUEtn1cBro7XlbASSt6NMWUHB1FsXX8&downloadName=Untitled.png

223
Q

What is the process for propogation of nerve impulses

A

When sodium from the part of the axon that was depolarised previously diffuses to the right, it makes the membrane potential in that area less negative. When the membrane potential reaches the threshold point, sodium channels open and let more sodium flow into the cytoplasm of the axon and cause depolarisation. Increased sodium ion concentration in the cell disturbs the concentration gradient that normally exists, and establishes a new concentration gradient. Inside the cell, the sodium concentration is high because it just diffused into the cell, therefore it will diffuse to the right and left inside the axon because that’s where the sodium concentration is still low. On the left side of the axon, the sodium channels are inactive as they’re in the refractory period, so no depolarisation can occur. To the right, the increased sodium depolarises that part of the axon and makes a new action potential, which repeats itself until the end of the axon is reached.

224
Q

Define nerve impulses

A

Action potentials propagated along axons of neurons. Propagation of nerve impulses is the result of local currents that cause each successive part of the axon to reach the threshold potential.

225
Q

Define synapses and their structure

A

Synapses: Connections between neurons and other things like neurons, glands, muscles, and receptors (sensory cells).

Structure: A presynaptic neuron and a postsynaptic neuron, with a gap of 20 nm between. The gap prevents movement of a nerve signal from one neuron to another.

226
Q

What is a neurotransmitter

A

Neurotransmitter: Chemical diffusing from the presynaptic neuron to the postsynaptic neuron, allowing electric signals in a presynaptic cell to ensure that another nerve signal is propagated in the postsynaptic neuron. It is a crucial factor in the transmission from one neuron to the next. There are about 40 neurotransmitters in the body. Acetylcholine and noradrenaline are two often found in synapses connecting nerves and muscle fibres.

227
Q

What are the steps in propagation of a nerve signal

A
  1. Neurotransmitter is synthesised and stored in vesicles of the presynaptic neuron
  2. Action potential reaches the presynaptic terminal
  3. Depolarisation of the presynaptic terminal causes opening of voltage-gated calcium 2+ channels
  4. Influx of calcium 2+ through channels
  5. Ca 2+ causes vesicles with neurotransmitters to fuse with a presynaptic membrane
  6. Neurotransmitter is released from presynaptic neuron into the synaptic cleft via exocytosis
  7. Neurotransmitter binds to receptor molecules on postsynaptic membrane
  8. Opening/closing of postsynaptic ion channels (i.e. if Na+ channels are opened, Na+ ions will enter the postsynaptic neuron and depolarise it, possibly initiating an action potential)
  9. Membrane potential of postsynaptic neuron changed (i.e. depolarised if sodium channels are opened). This affects whether the postsynaptic cell may have an action potential.
  10. Retrieval of vesicular membrane from plasma membrane in the presynaptic neuron
228
Q

What is the postsynaptic potential

A

Postsynaptic potentials: Changed in postsynaptic membrane potential. When many excitatory postsynaptic potentials occur in a neuron at once, they might add up to initiate an action potential, and information is passed from one neuron to the next. The propagation of an action potential across a synapse involves the depolarisation of the presynaptic neuron, which triggers a cascade of reactions that lead to the release of a neurotransmitter into the synapse.

229
Q

What is acetylcholine and what is its role in synapses

A

Acetylcholine: Choline and acetyl group. In presynaptic cell, it’s combined by the enzyme choline acetyl transferase and then stored in vesicles. When the acetylcholine is released into the synaptic cleft by exocytosis and diffuses across to the postsynaptic cell, it binds briefly to the receptors on the postsynaptic neuron. This causes sodium ion channels to open and the postsynaptic membrane to be depolarised. If the threshold is reached an action potential will occur. Once the neurotransmitter is released, an enzyme called acetylcholinesterase breaks the neurotransmitter down into choline and acetate. The choline is reabsorbed by the presynaptic cell and used again, while the acetate is recycled in the presynaptic knob.

Note: Secretion of acetylcholine by neurons at synapses by exocytosis ensures the action potential is propagated to the postsynaptic neuron. The timely reabsorption of acetylcholine ensures the intensity and duration of the signal being sent is controlled.

230
Q

What is modulation

A

Modulation: Modulating the message means controlling the intensity and duration of the signal across the synapse. This can happen through reabsorption of the neurotransmitter by the presynaptic neuron, which is how antidepressants work. Modulation can also occur when enzymes in the synapse break down a neurotransmitter like in MAOIs.

231
Q

What are SSRIs

A

SSRIs (Selective serotonin reuptake inhibitors): Antidepressant drugs that prevent presynaptic neurons from absorbing the neurotransmitter serotonin from the synapse, allowing it to affect the postsynaptic neuron for a longer period of time.

232
Q

What are MAOIs

A

MAOIs (monoamine oxidase inhibitors): Antidepressants. Monoamine oxidase is an enzyme that breaks down serotonin. When it’s inhibited by these types of antidepressants the serotonin is able to affect the postsynaptic neuron for a longer period of time.

233
Q

What are neonicotinoids

A

Neonicotinoids: Derivatives of nicotine used as insecticides. Neonicotinoids can bind to nicotinic acetylcholine receptors in cholinergic synapses. Once a neonicotinoid enters the nervous system, it irreversibly binds with receptors, preventing acetylcholine from binding. Acetylcholinesterase also can not break down the compounds

234
Q

What are cholinergic synapses

A

Synapses that use acetylcholine as the neurotransmitter

235
Q

What is the effect of neonicotinoids

A

Effect: Synaptic transmission is permanently blocked; the nerve signals can’t be propagated to the postsynaptic nerve. If in the brain this can result in paralysis or death.

Effect per species: Binding of neonicotinoids to receptors is not as strong as in insects. Thus, humans and other mammals are less affected by these compounds than insects. Most of the cholinergic receptors in insects are also located in the brain, making neonicotinoids useful insecticides.

236
Q

What is imidacloprid

A

Type of insecticide that’s a neonicotinoid. It has an annual turnover of over 1 billion dollars.

237
Q

What is the effect of neonicotinoids on bee populations

A

Bee populations are lower due to a casual relationship with exposure to neonicotinoids.

238
Q

What are the standard blood glucose levels and how are they maintained

A

Blood Glucose Levels: Need to be kept within 70-130 milligrams/decilitre for most people so that your blood has a certain osmotic balance, and cells of your body (especially brain cells) have an ample supply of glucose for cellular respiration. If sensors detect blood glucose levels are above or below the limits, two hormones are secreted.

Insulin and Glucagon: Produced by the Islets of Langerhans in the pancreas. Responsible for maintaining and controlling blood glucose concentrations.

239
Q

What is insulin

A

Insulin: Secreted when blood glucose is higher than normal. It’s produced and secreted by the beta-cells of islets of Langerhans in the pancreas. It causes the blood glucose levels to fall by stimulating glucose uptake into muscles and liver cells, where it’s converted into glycogen.

240
Q

What is glucagon

A

Glucagon: Secreted when blood glucose is lower than normal. It’s produced and secreted by the alpha-cells of islets of Langerhans in the pancreas. It causes the blood glucose levels to rise by stimulating glycogen hydrolysis to glucose in the liver, which releases glucose into the blood.

241
Q

What are the two types of pancreatic function

A

The pancreas has exocrine AND endocrine functions. As an exocrine gland (gland associated with a duct) it secretes enzymes that help in digestion, while as an endocrine gland (ductless gland) it secretes hormones that regulate blood sugar levels.

242
Q

What is the difference between glucagon and glycogen

A

Glucagon is a protein-based hormone released from the pancreas. Glycogen is NOT a hormone; it’s a carbohydrate found in the liver that is in the form that glucose takes when stored there.

243
Q

What is diabetes

A

Diabetes mellitus: Blood glucose levels are consistently too high, and urine has elevated glucose levels.

Symptoms: Frequent urination, increased thirst, hunger

244
Q

What happens if diabetes is left untreated

A

If untreated: Serious long-term complications can occur such as heart disease, kidney failure, and retinal damage

245
Q

What are the types of diabetes

A
  • Type 1 Diabetes: Results from body’s failure to produce insulin. This is sometimes referred to as insulin-dependent diabetes mellitus (IDDM) or juvenile diabetes
    • Treatment: Injecting insulin into the body daily
  • Type 2: Results from insulin resistance which is a condition where the body cells fail to use insulin properly. This was previously referred to as non insulin-dependent diabetes mellitus (NIDDM), or adult-onset diabetes because it usually starts later in life.
    • Treatment: Eating food with low levels of carbohydrates, frequent but small meals, strenuous exercise, losing weight.
246
Q

What is thyroxin

A

Definition: Main hormone that regulates metabolism and body temperature

Overall Effect: To activate nuclear transcription of large numbers of genes for synthesis of enzymes, structural proteins, transport proteins, and other substances in almost all cells of the body. Therefore, increasing metabolic activities of almost all body tissues.

Effects List:

  • Increased rate of utilisation of foods for energy
  • Increased breathing rate to obtain oxygen and get rid of carbon dioxide
  • Increased rate of protein synthesis and protein carabolism
  • Increased number and size of mitochondria in most cells of the body
  • Increased growth rate of children and adolescents
  • Growth and development of the brain during fetal life and for the first few years of post-natal life
  • Enhanced carbohydrate metabolism
  • Enhanced fat metabolism

Note: All of those effects are regulated by the level of thyroxine produced. Too much or too little will affect the normal functioning of the body

247
Q

How does thyroxin affect body temperature

A

Body Temperature: When body’s metabolic rate increases, the rate of cellular respiration also increases, producing a large amount of heat. Thus, elevated thyroxine production accounts for increased body temperature. When body temperature is too high, thyroxine level is thus decreased, and vice versa.

248
Q

Where is thyroxine produced

A

Production: In thyroid gland. Requires 4 iodine atoms and amino acid tyrosine. If there’s not enough of these, a goitre may be developed.

249
Q

What is hyperthyroidism, hypothyroidism, and a goitre

A

Hyperthyroidism: Body makes too much thyroxin

Hypothyroidism: Not enough thyroxin

Goitre: Enlargement of the thyroid gland

Goitre treatment: Supplementing diet low in iodine with iodine tablets

Symptoms of thyroxine deficiency:
- Fatigue
- Depression
- Forgetfulness
- Feeling cold
- Constipation
- Impaired brain development if in young children

250
Q

What are the adipose tissues

A

Adipose Tissues: Fatty tissues mainly composed of fat cells (adipocytes) that are specialised in the synthesis and storage of fat globules/lipids

251
Q

What is leptin

A

Leptin: Hormone produced and secreted by cells in adipose tissues

252
Q

What factors control blood leptin concentration

A
  • Food intake
  • The amount of adipose tissues in the body
253
Q

Where are leptin receptors and how does appetite inhibition occur

A

Leptin Receptors: Found in the hypothalamus of the brain

Appetite inhibition: Occurs when leptin binds to leptin receptors

254
Q

What happens to leptin and appetite when fat mass decreases or increases

A

When fat mass decreases: the level of plasma leptin falls (only a few of the leptin receptors bind to leptin in the hypothalamus) so appetite is stimulated until the fat mass is recovered. There’s also a decrease in body temperature and energy expenditure is suppressed

When fat mass increases: Leptin levels increase and appetite is suppressed until weight loss occurs.

255
Q

What is the function of leptin

A

Regulation of energy intake and fat stores so weight is maintained within a narrow range.

256
Q

What is the relation between leptin and obesity and how was it found

A

Mice: Strain of mice was discovered in the 1950s with a mutation that made them greedy. They quickly became obese and had a mass of up to 100g whereas the normal range was 20-25 g. These mice were homozygous for the ob (obese) allele. Mice with two of these recessive alleles could not produce leptin, thus having no appetite inhibition. They were then injected with leptin and their body mass reduced by 30% in a month.

Humans: A small subset of humans are also homozygous for the ob allele, and are frequently obese. In a double-blind trial (no one know if they had placebos or the real leptin drug, including researchers), some participants did lose body mass but others gained it. Those that lost it quickly regained it after the trail was stopped. These are very disappointing results compared to the mice.

Reasons for difference between mice and humans:

  • Obese people have very high leptin levels in their blood, meaning that receptor cells in the hypothalamus might no longer be sensitive and responsive to leptin.
  • The exact mechanisms by which leptin activates hypothalamic neurones to suppress appetite is not fully understood yet
257
Q

What is melatonin and how is it made

A

Melatonin: Hormone that controls the internal clock of your body; your internal circadian rhythm. Melatonin levels are high at night and low during the day.

Synthesis: Produced in pineal gland from the amino acid tryptophan and its production is dictated by light. Exposure to light has a negative effect on the release of melatonin.

258
Q

What is the pineal gland

A

Small endocrine gland found near the centre of the brain between two hemispheres. It’s reddish-gray and shaped like a pine cone about 0.8 cm long.

259
Q

Why can we maintain a day/night cycle independent of external cues

A

Human brains can maintain a day/night cycle independent of external cues due to melatonin level cycles. However, without external cues, the day/night cycle is slightly longer than 24 hours, so it slowly shifts away from the actual night and day cycle. The reason those with external cues don’t shift away from the cycle is because of certain receptor cells in the retina that signal dawn and dusk to the pineal gland.

260
Q

How do impulses from the retina regulate melatonin levels

A

Impulses from retina: first channeled to a group of cells in the anterior hypothalamus, which are called the suprachiasmatic nuclei (SCN). The SCN then pass on information to the pineal gland. The pineal gland adapts melatonin concentrations to coincide with a normal 24-hour cycle.

Note: Melatonin receptors are also present on neurons of the suprachiasmatic nuclei of most species, implying the possible involvement of a negative feedback loop in the regulation of melatonin

261
Q

What are the effects of melatonin

A
  • Internal temperature drops
  • Receptors in the kidney cause decreased urine production
262
Q

How do estrogen and progesterone affect embryonic development

A

Embryo: All embryos in the uterus start out as female

Estrogen and Progesterone: Two hormones that are continually present during pregnancy because the mother’s ovaries and placenta keep secreting them. They start the embryo on the path to becoming a female, with the gonads developing into ovaries.

263
Q

How does sexual distinction occur

A

Male and female reproductive systems have a similar pattern of development. Sexual distinction only occurs as a result of the influence of hormones. The first sign of development of reproductive organs happens during the 5th week and sexual distinction of the external genitalia becomes apparent in the 10th to 12th week.

264
Q

Draw a diagram of the female reproduction system

A

https://file.notion.so/f/f/e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560/513edcf9-067d-4ab3-9930-4d60b672ecb0/Untitled.png?id=69af44aa-185d-4ad6-8586-274e6b19edf1&table=block&spaceId=e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560&expirationTimestamp=1715040000000&signature=3z3Rm71-_v-cIu1uvkwhRUokUI75LXkWy0zFnwDcg-o&downloadName=Untitled.png

265
Q

What are the organs of the female reproductive system

A

Ovary: Produces estrogen, progesterone, and ovum (eggs)

Fallopian tubes (oviduct): Collect eggs from the ovary and carry them to the uterus

Uterus: Place for the gestation(development) of the embryo and fetus

Cervix: Blocks entry to the uterus during pregnancy and dilates during birth

Vagina: Canal connecting cervix and outside of body. Forms birth canal and is the receptacle for penis during heterosexual intercourse

Vulva: External parts for the production of the internal reproductive system

266
Q

What happens if an embryo has XY chromosomes

A

Protein named testis determining factor (TDF) is coded for by the SRY gene on the Y chromosome. This triggers the development of testis. TDF is a DNA-binding protein that regulates transcription of a number of genes that are involved in the differentiation of the gonads into the testis. This happens around week 8 of pregnancy. Once testis have developed, they start producing testosterone. This triggers the development of male genitalia. During puberty, testosterone production increases further, giving rise to the secondary male sexual characteristics such as pubic hair, penis enlargement, and deepening of the voice. Testosterone is also responsible for triggering the production of sperm.

267
Q

Draw a diagram of the male reproductive system

A

https://file.notion.so/f/f/e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560/a78b79ee-8392-4be0-ac45-8e55f7bbb393/Untitled.png?id=39fe48f3-1110-4a76-b974-b1e709ab6ed0&table=block&spaceId=e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560&expirationTimestamp=1715040000000&signature=VZn8ybAT9GLdkOn9djAOM14IrZoaPi76et6FxZCfR3A&downloadName=Untitled.png

268
Q

What are the organs of the male reproductive system

A

Testis: Sperm and testosterone production

Epididymis: Store sperm until ejaculation

Sperm duct: Transfers sperm during ejaculation

Seminal vesicles: Produce an alkaline, sugar-rich fluid (fructose) that provides sperm with a source of energy to help them move

Prostate gland: Produce an alkaline fluid, rich in proteins, which with seminal vesicle’s secretion and sperm makes semen

Urethra: Transfer semen during ejaculation and is the passage of urine during urination

Penis: Becomes erect during sexual arousal. Penetrates vagina during heterosexual intercourse to deposit semen close to the cervix.

269
Q

Define the menstrual cycle

A

Definition: Cyclic and periodic change in ovarian and pituitary hormones that control when a women is fertile. This occurs between the onset of puberty and the end of menopause. It also controls the timing of menstruation and the release of blood and tissue from the uterus through the vagina

270
Q

Define puberty

A

Phase of adolescence when the individual reaches sexual maturity and becomes capable of reproducing. It’s accompanied by the maturation of genital organs, development of secondary sexual characteristics, and the first occurrence of menstruation in females (in humans and some primates).

271
Q

Define menopause

A

Phase in woman’s life around age of 45-50 when menstruation stops.

272
Q

What are the phases of the menstrual cycle

A
  1. Follicular(1st 14 days): Formation of follicles in the ovary which each contain one egg during its development until ovulation
  2. Luteal(2nd 14 days): Transformation of a follicle into a corpus luteum once ovulation has taken place around day 14
273
Q

Define menstruation

A

Marks the start of the menstrual period. Lining of the uterus is shed and bleeding starts. Menstruation normally lasts around 3-5 days. If fertilisation doesn’t happen, the corpus luteum breaks down, resulting in a decrease in the level of progesterone and estrogen. With a drop in the progesterone level, the thickened lining of the uterus can’t be maintained anymore, and breaks down. As a result, the extra layers of the endometrium lining, the unfertilised egg, and a small amount of blood, pass through the vagina. This lasts 3-5 days. While menstruation is happening, the amount of estrogen in the blood falls, reducing the inhibitory effect of estrogen on FSH secretion. The pituitary gland then increases its output of FSH, a new follicle starts maturing, and the cycle starts again.

274
Q

What are the hormones controlling the menstrual cycle

A

Luteinising hormone (LH) and follicle-stimulating hormone (FSH) (secreted by pituitary gland); Estrogen and progesterone (secreted by ovaries).

275
Q

What is the follicular phase of the menstrual cycle

A

FSH causes several follicles in the ovary to begin to develop, and usually only one matures. As it develops, it secretes estrogen which stimulates the uterine lining (endometrium) to thicken with mucus and a rich supply of blood vessels. These changes last about 10 days and prepare the uterus for a possible pregnancy. The endometrium is where a fertilized ovum will implant in order to further develop during pregnancy.

276
Q

Define ovulation

A

A high level of estrogen in the blood (produced by the follicle) causes the pituitary gland to reduce secretion of FSH(negative feedback) and begin secretion of LH(positive feedback). The decrease of FSH then decreases the production in estrogen. When the concentration of LH in the blood reaches a threshold, ovulation occurs, meaning one mature follicle (a Graafian follicle) ruptures, and releases a mature egg. Ovulation occurs around the middle of the menstrual cycle.

277
Q

What is the luteal stage of menstruation

A

After ovulation, LH causes the ruptured follicle to fill with cells, which forms the corpus luteum (yellow body). It secreted the hormone progesterone, which maintains the continued growth of the endometrium. The corpus luteum also produces estrogen, which accounts for the rise in this hormone level after ovulation. As the concentration of estrogen and progesterone rise to a threshold, they inhibit the secretion of FSH and LH respectively (negative feedback). Luteal stage lasts 14 days.

278
Q

What are the hormones of the menstrual cycle (include where their made, when they rise, and their function)

A
  • Progesterone
    • Produced: Ovary
    • Rises: Start of luteal phase
    • Function: Promotes thickening and maintenance of the endometrium
  • Estrogen
    • Produced: Ovary
    • Rises: Peaks near end of follicular phase
    • Function: Stimulates repair of endometrium and increase in FSH receptors on ovary cells
  • FSH
    • Produced: Pituitary
    • Rises: Starts near end of the cycle
    • Function: Stimulates development of follicles and production of estrogen by the follicle wall
  • LH
    • Produced: Pituitary
    • Rises: Suddenly during end of follicular phase
    • Function: Stimulates completion of meiosis in the oocyte, and thinning of the follicular wall, so that ovulation can occur. After ovulation, it stimulates the development of the remaining part of the Graafian follicle into the corpus luteum by causing an increase in the number of follicle cells, which secretes estrogen (positive feedback) and progesterone.
279
Q

Define IVF

A

Definition: Artificial fertilisation. The fertilisation (joining of the sperm and egg) takes place in vitro (glass)

280
Q

What are the steps of IVF

A
  1. Egg production stimulated by hormone therapy
    1. Woman is given drug(s) to suppress her natural cycle by suspending her normal secretion of hormones. She can administer them herself in the form of a daily injection or nasal spray. This happens for about 2 weeks.
    2. FSH and LH are injected at a higher dose than normal for around 12 days to stimulate production of a number of ova (egg cells), called superovulation. The clinic monitors progress throughout by vaginal ultrasound scans and possibly blood tests
  2. Between 34 and 38 hours before eggs are due for collection, the woman is given a hormone injection to help them mature. This is likely to be human chorionic gonadotrophin. Eggs are then usually collected from the ovaries by using ultrasound guidance while the woman is sedated. A hollow needle is attached to the ultrasound probe and used to collect eggs from the follicles in each ovary
  3. A sperm sample is collected from the man and checked for viability
  4. Eggs are mixed with sperm and cultured in the lab for 16-20 hours after which they are checked for signs of fertilisation. Sperm can also be injected directly into the egg. The eggs then grow into embryos and fetus’ in the laboratory incubator for up to 6 days. This is monitored by an embryologist and the best embryos will be chosen for transfer. The remaining ones are frozen for future use.
  5. If the woman is under age of 40, one or two embryos are implanted in the uterus at the right time in her menstrual cycle. But if she’s older than 40 years, a maximum of 3 can be used. The number of embryos transferred is restricted due to risks associated with multiple births.
281
Q

What did Harvey find for investigating in Sexual Reproduction

A

Philosophers and physicians in Harvey’s day believed in Aristotle’s theory, where the man produces a seed which develops into an egg, which then develops into an embryo with the help of menstrual blood.

Harvey: Used a scientific approach by observing and dissecting female deer in the mating season to see if small embryos could be found immediately after fertilisation. He said that the seed and soil theory put forward by Aristotle couldn’t be true because there were no small embryos in the uterus of female deer after fertilisation. However, he couldn’t fully explain how development occurred, since he couldn’t see any embryo until many weeks after fertilisation.

Biology (7 decks)

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