Option D: Human Physiology Flashcards
(79 cards)
1
Q
essential nutrients
A
- nutrients that can’t be synthesized by the body
- yet are necessary for function
2
Q
dietary minerals
A
- inorganic substances required by living organisms
- they can be recycled but not with 100% efficiency
- thus small amounts of those minerals in our diet are necessary
- as most of them are soluble in water, they are generally referred to as “electrolytes”
3
Q
why are Ca2+ ions necessary?
A
- they are used in the growth and repair of bones
- bones require constant repair so small amounts of Ca ions are always being lost and must be replaced
4
Q
why are Fe2+ ions necessary?
A
- Fe2+ ions are an important component of haemoglobin, found in erythrocytes (RBCs)
- RBCs have a lifespan of 4 months and its components are recycled in the liver after it reaches its limit
- however not all iron can be recovered
- so it has to be replaced in the diet
5
Q
vitamins
A
- chemically diverse carbon (organic) compounds)
- not all vitamins can be synthesized by a particular organism
- so it relies on vitamin intake from other organisms
6
Q
vitamin C as an essential vitamin
A
- it’s not an essential vitamin for most vertebrates but it is for humans
- if humans go without vit C for extended periods, they become afflicted with the deficiency disease scurvy
- it’s produced from glucose in the kidneys of some animals and in the livers of others
- its synthesis requires 4 enzymes in a metabolic pathway
- the 4th enzyme’s gene coding is defective in all humans
- this makes it an essential vitamin
7
Q
vitamin D as an essential vitamin
A
- along with Ca2+, vit D is necessary for proper formation of bones
- going without adequate vit D during adolescence may lead to rickets, a disease causing bone deformities
- bones near growth plates (areas at the end of developing bones) don’t mineralize properly
- this leads to irregular, thick, and wide bone growth
- children with rickets won’t reach their optimal height and their legs are bowed inwards/outwards at the knees
- adults don’t develop rickets but will instead develop osteomalacia (i.e. soft bones)
- the human skin epidermis contains precursors that can synthesize vit D when stimulated by UV rays in sunlight
8
Q
essential fatty acids
A
- alpha linolenic acid (omega-3)
- linoleic acid (omega-6)
9
Q
cholesterol as an indicator of coronary heart disease
A
- people may develop plaque on their arteries
- sufficient build-up of plaque on coronary arteries leads to coronary heart disease (CHR)
- if enough build-up occurs to block a coronary artery, a heart attack occurs
- one component of plaque is cholesterol
- thus monitoring blood cholesterol levels can reduce the risk of heart attacks
10
Q
no. of essential amino acids to humans
A
9 out of 20
11
Q
importance of having essential amino acids in diet
A
- lack of essential amino acids affects protein synthesis
- human body has no storage mechanism for amino acids
12
Q
phenylketonuria (PKU)
A
- genetic disease causing inability to metabolize the amino acid phenylalanine
- due to mutation of gene carrying information on the enzyme phenylalanine hydroxylase, which breaks down phenylalanine
- this inability causes excess buildup of phenylalanine in the bloodstream and in tissues
- resulting in seizures, mental deficiencies, behavioural problems, etc
- the PKU gene is recessive
13
Q
treating phenylketonuria
A
having a diet that limits protein sources high in phenylalanine
14
Q
malnutrition
A
- nutritional problems
- caused by deficiencies/imbalances/excess of nutrients in the diet
15
Q
malnutrition due to deficiency
A
- growth becomes stunted/irregular
- in the case of Ca2+/vit D, children contract rickets
16
Q
malnutrition due to imbalance
A
1 or more essential amino acids may be lacking
17
Q
malnutrition due to excess
A
obesity
18
Q
autonomic activities
A
activities occurring at the subconscious level
19
Q
appetite control center
A
hypothalamus
20
Q
how does the hypothalamus regulate appetite?
A
- full stomach –> electrical impulses sent to hypothalamus
- intestines + pancreas produce hormones to transmit info to the hypothalamus
- adipose (fat) tissues produce the hormone leptin to transmit info to the hypothalamus
21
Q
health implications of anorexia
A
- anorexia is an eating disorder characterized by having an unhealthy body ideal
- tendencies include starving oneself, coupled with excessive exercise
- insufficient amount of essential nutrients –> body systems are negatively affected
- without adequate essentials, the heart gets smaller and weaker over time
22
Q
health risks of obesity
A
more likely to develop hypertension and type II diabetes
hypertension:
- high blood pressure
- increased strain on heart and arteries
- some factors of HBP are uncontrollable (e.g. age) but others are (e.g. BMI)
type II diabetes:
- resistance to insulin = can’t metabolize glucose correctly
- glucose can no longer be stored effectively and remains at higher concentrations in the bloodstream
23
Q
what happens during starvation?
A
- body tissues are digested for their stored nutrients
- their own skeletal muscles are used as a source of amino acids to make other proteins
- the skeletal muscles are still there but barely noticeable
24
Q
digestion
A
- chemical process
- requires secretion of digestive fluids
- these secretions are controlled by the nervous and endocrine systems
25
importance of regulating digestive fluids
would be wasteful + possibly harmful to continuously secrete digestive juices
26
exocrine glands
- secretes into ducts (NOT into bloodstream)
| - the ducts take the secretion either out of the body or into the lumen of the gut
27
examples of exocrine glands
- lacrimal glands
- gastric glands
- pancreas
- liver
28
function of lacrimal glands
- secretes tears
- taken by ducts to outer section of the eye
- for lubrication
29
function of gastric glands
- secretes gastric fluid
- taken to stomach lumen
- mucus secretions protect stomach lining
- HCl denatures proteins and its pH kills some pathogens
- the enzyme pepsin breaks down proteins
30
function of pancreas (exocrine gland only)
- secretes pancreatic fluid
- taken to the duodenum
- contains digestive enzymes and a bicarbonate solution to neutralize partially-digested food
(NOTE: as the pancreas also secretes hormones into the bloodstream, it's also an endocrine gland)
31
function of liver (exocrine gland only)
- secretes bile
- taken to the gallbladder and duodenum
- for emulsification of lipids
32
mechanisms regulating digestive fluids
- nervous system: seeing/smelling/thinking about food triggers digestive secretions
- endocrine system: includes all glands that secrete hormones into the bloodstream
- the two systems control the volume and content of secretions e.g. in the stomach lumen
33
gastric pit
- numerous small exocrine glands in the stomach lining
- pit-like structures lined with cells that secrete substances into the lumen
- secretions include: mucus, HCl, pepsinogen
34
gastric fluid
the overall secretions of gastric pits
35
gastrin
- hormone released by certain stomach cells
- secretions are controlled by the nervous system
- gastrin stimulates the production of more gastric juice
36
how does the nervous system regulate gastric juice during digestion?
- the thought/smell/sight/taste of food sends an electrical impulse to the medulla oblongata in the brain stem
- action potentials are sent by the vagus nerve to the stomach to stimulate the secretion of gastric juices and gastrin
- as gastrin joins the bloodstream, it stimulates more production of gastric juice in other areas of the stomach
- when food enters the stomach, the stomach walls become distended (expanded)
- more messages are sent to the medulla oblongata, which sends back impulses to maintain/increase gastric juice secretion
- when the chyme (partially-digested food) passes into the duodenum, a set of signals stimulates the secretion of the hormone secretin
- it terminates the secretion of HCl and pepsinogen
37
how are the acidic conditions of the stomach suitable for digestion?
- HCl helps prevent food poisoning by destroying many pathogens
- also provides a pH that favors certain hydrolysis reactions
- pepsinogen is an inactive enzyme that activates in low pH to become the enzyme pepsin, which breaks down proteins into amino acids
- however, the highly acidic conditions also cause health problems
- acid reflux is a condition in which oesophagus walls are damaged by gastric fluids
- stomach ulcers are made worse by the acidic gastric juice
38
how have health problems caused by gastric juices been mitigated?
- proton pump inhibitor drugs were developed
| - they inhibit the production of HCl in gastric pits
39
what causes stomach ulcers
- it was believed that nothing could survive in the pH 2 conditions of the stomach
- but H. pylori bacteria can survive by burrowing into the mucous layer to infect stomach lining cells
- they then neutralize stomach acid using the enzyme urease to create ammonia
- infection leads to gastritis and stomach ulcers
40
how are villi adapted to their function?
- each villus has epithelial cells with microvilli for increased SA
- digested molecules pass through these cells before entering a villus
- one side of each epithelial cell is in direct contact with the fluid in the lumen (i.e. digested molecules)
- tight junction: epithelial cells are held tightly together by shared proteins
- this prevents undigested food from entering the villus without passing through a plasma membrane
- some molecules are absorbed via active transport, so each epithelial cell contains numerous mitochondria
- near the epithelial cells is a capillary bed for absorption into the bloodstream
41
importance of fibre in diet
- the higher the fibre content, the more efficiently undigested material moves through the large intestine
- bc fibre can't be digested
- high fibre content helps all solid waste to continue moving
- this prevents the waste from remaining in the large intestine for long
42
symbiotic conditions in the large intestine
- a large amount of bacteria lives in the large intestine
- they thrive due to the water, warmth, and food material provided
- in turn they provide vit K, which is necessary for blood clotting
43
circulation of blood to and from the liver
- hepatic artery: supplies oxygenated blood
- hepatic portal vein: brings absorbed nutrients from intestines
- hepatic vein: brings blood from liver to vena cava, then right atrium
44
hepatic portal vein
- receives blood from all the capillaries in the small intestine
unlike other blood vessels arriving at an organ, it:
- is filled with low-pressure deoxygenated blood
- contains a variable amount of nutrients depending on the type of food ingested and the timing of ingestion/digestion/absorption
45
hepatocyte
- liver cells that filter toxins in the bloodstream
| - they chemically alter toxins so they either become useful or are added back to be eliminated via kidney filtration
46
role of the liver with relation to RBCs
- as RBCs don't have a nucleus, their lifespan is short (4 months)
- a single RBC contains 250 mil haemoglobin proteins
- each haemoglobin contains 4 polypeptides that contains a non-protein haem group at the centre
- the liver makes sure the RBCs' components are recycled as much as possible
47
how is each RBC component recycled?
- sinusoids are lined with Kupffer cells (specialized WBCs)
- they remove RBCs via phagocytosis
- all 4 polypeptides are hydrolysed into amino acids in the Kupffer cell
- amino acids are returned to the bloodstream or deaminated by the liver (depending on blood conc)
- haem groups are separated from the globin chain and sent to nearby hepatocytes for further modification
- the iron is removed from each haem group and sent to the bone marrow
- iron-less haem groups are modified to bilirubin (an important component of bile)
48
role of the liver with relation to cholesterol
- lipids are not water-soluble, so they combine together
- this forms lipid droplets in the lumen of the stomach and small intestine
- the enzyme lipase can break down lipids, but only whatever is on the surface
- bile, a fluid secreted by the liver, helps emulsify lipids (i.e. breaks them into smaller droplets), increasing their SA for faster digestion
- bile is made up of 2 components: bile salts and bilirubin
- bilirubin is synthesized from the remains of a haem group after Fe2+ is removed
- bile salts are synthesized in the liver from surplus cholesterol
49
plasma proteins
proteins circulating in blood plasma
50
examples of plasma proteins
- albumin
| - fibrinogen
51
albumin
- protein regulating the osmotic balance of blood
| - used as a carrier molecule for bile salts and other fat-soluble molecules
52
fibrinogen
- protein used in blood clotting
- when a blood vessel is damaged, the inactive enzyme prothrombin activates into thrombin and converts fibrinogen to fibrin
- the fibrin mesh traps blood clots to seal in the cut area
53
role of the liver in plasma protein production
hepatocytes secrete plasma proteins using golgi apparatus and the endoplasmic reticulum
54
role of the liver in the regulation of nutrients
- the hepatic portal vein transports nutrients directly from the small intestine
- the liver regulates the nutrient levels so that nutrient levels are more stable and consistent in the hepatic vein compared to the hepatic portal vein
55
sinusoids
- capillaries of the liver
| - where exchanges occur between blood and hepatocytes
56
differences between sinusoids and regular capillaries
- sinusoids are wider than regular capillaries
- they're lined with endothelial cells with gaps in between
- the gaps allow large molecules (e.g. proteins) to be exchanged
- as hepatocytes are in direct contact with blood components, exchanges are more efficient
- sinusoids contain Kupffer cells
- they receive a mixture of oxygen-rich and nutrient-rich blood
57
how does alcohol cause liver damage?
- alcohol can be mistaken for useful nutrients and brought to the liver hepatocytes
- each time blood passes through the liver, the hepatocytes attempt to remove the alcohol
- over time the exposure incurs damage to the liver cells
58
types of liver damage due to alcohol
- cirrhosis: scar tissue where hepatocytes have been destroyed due to alcohol exposure -- areas with cirrhosis no longer function
- fat accumulation: damaged areas may build up fat instead of normal liver tissue
- inflammation: swelling of damaged liver tissue due to alcohol exposure (i.e. alcoholic hepatitis)
59
nutrients stored by the liver
- glycogen: polysaccharide of glucose
- iron: removed from haemoglobin and later sent to bone marrow
- vit A: associated with good vision
- vit D: associated with healthy bone growth
- vit B12/K
60
jaundice
- condition caused by excess bilirubin in bloodstream
- as bilirubin is a yellow pigment, people with jaundice have a yellow tinge to their skin and whites of their eyes
- if untreated, may cause acute bilirubin encephalopathy
- because excess bilirubin levels are toxic to brain cells
61
types of jaundice
- infant jaundice: found in babies born prematurely (their liver can't fully process bilirubin into bile)
treatment: exposure to blue-green light spectrum -- this changes the shape and structure of bilirubin molecules
- adult jaundice: similar symptoms and consequences, but the cause is not an immature liver (obviously) but to liver damage
62
how are heart muscles adapted to their function?
- cardiac muscle cells are connected via intercalated discs
- discs contain small holes called gap junctions where cytoplasm and electrical impulses can be transmitted/shared
- muscle cells form branches, so they can chemically communicated with one another
- result: all the cells work together to contract as a unit
63
how do the SA and AV nodes work?
- the SA node (group of cells in the right atrium) creates an impulse that extends across muscle cells in the atria via intercalated disks and branches
- however, these disks and branches don't extend into the ventricles
- the ventricles get their signal from the AV node, which doesn't act spontaneously but transmits the signal to contract from the SA node after a brief delay
64
what happens during the delay between the SA and AV impulse?
- both atria have enough time to complete atrial systole (process of contracting and forcing blood into the ventricles) before the AV valves close
- heart valves open and close based on pressure differences on either side of the valve
- after the delay, the ventricles contract as the AV valves close and SL valves open, forcing the blood out of the ventricles into the aorta
65
how is ventricle contraction coordinated?
- ventricle muscular walls are very thick (thicker than atrial walls)
- there are too many cells in the ventricular walls for efficient cell-to-cell communication
- thus the ventricles rely on nerve fibres to quickly spread the impulse from the AV node
- this is done via a system of conducting fibres from the AV node to the septum between the two ventricles
- from there, branches called Purkinje fibres are spread out into the thick cardiac muscle tissue of the ventricles
- the impulse is carried from the conducting fibres to the muscle fibre
- gap junctions conduct them across the ventricles
66
how are normal heart sounds made?
- the thumping sounds are caused by the opening and closing of the SL and AV valves
- the first sound is the AV valves closing
- the second sound is the SL valves closing
67
systolic pressure
measurement of pressure in arteries when ventricles contract (undergo systole)
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diastolic pressure
measurement of pressure in arteries when ventricles are at rest and refilling with blood
69
hypertension: causes, effects, and treatment
```
- consistent HBP
cause:
- loss of elasticity in blood vessels
- build-up of plaque in arteries
effect: increased risk of heart attack/stroke
treatment:
```
70
thrombosis: causes, effects, and treatment
- thrombus (clot) develops and breaks loose within a blood vessel
cause: usually plaque build-up -- the thrombus is a formed from a part of the plaque breaking away
effect: can be fatal if the thrombus gets stuck in lung or coronary arteries
treatment: anticoagulant medications -- prevents blood clotting from occurring as quickly
71
artificial pacemakers and their use
- small battery-operated device implanted under the
skin
- sets the heart rate in the same way that a healthy SA node would
- connected to one or more wires (leads) that are threaded into a blood vessel leading directly into the interior of the heart
- a very small electrical shock occurs at regular intervals, each shock triggering a cardiac cycle
- placement of lead(s) is dependent on the patient’s heart problem and how many leads are being placed
72
defibrillation devices and their use
- heart attack can mean the heart has stopped (cardiac arrest) or is no longer in sequence with the set of electrical impulses typical of a cardiac cycle (arrhythmia)
- effect: blood is not being pumped effectively to the rest of the oxygen-deprived body
- defibrillation: process involving a device that delivers an electric shock to the heart
- it resets the electrical signals starting with the SA node
- the heart will continue beating on its own once the electrical shock has been delivered
73
factors contributing to risk of coronary heart disease (CHD)
CHD: plaque build-up in arteries and the problems associated with them
risk factors:
- obesity
- stress
- HBP
- cholesterol problems
- remember that these risk factors have a cascading effect (one factor affects another)
e. g. stress → smoking and overeating → obesity → HBP, cholesterol problems, etc
74
steroid hormones
- controls protein production within the target cell
- synthesized from cholesterol
- in a cell, it binds with a receptor protein to form a receptor–hormone complex
- the complex passes through the nuclear membrane and selectively binds to 1+ specific gene(s)
- can inhibit or promote transcription
- target cell(s) have their biochemistry dramatically altered due to the presence of the hormone
75
peptide hormones
- composed of amino acids
- upon reaching a target cell, it binds to a receptor protein on the outer surface of the cell membrane
- the presence of the receptor protein determines whether or not a cell is a target cell
- similar mechanics with enzyme-substrate specificity
- a peptide hormone's chemical binding to a receptor protein activates a secondary messenger molecule in the cytoplasm
- the secondary messenger chemically activates 1+ other messenger molecule(s) in the cytoplasm in a cascade of reactions
- the final messenger either activates an enzyme in the cytoplasm (thus allowing a rxn that was not possible before), or activates a transcription factor that enters the nucleus and either promotes or inhibits transcription in general
76
how does the posterior lobe of the pituitary gland communicate with the hypothalamus?
- hormones produced in the hypothalamus are secreted in the posterior pituitary
- posterior lobe of the pituitary contains axons of neurosecretory cells (very long cells whose dendrites and cell bodies are located in the hypothalamus)
- hormones are produced in the hypothalamus and secreted in the posterior pituitary gland (in a similar way to the release of a neurotransmitter)
77
how does the anterior lobe of the pituitary gland communicate with the hypothalamus?
- target cells of hormones produced + secreted in the hypothalamus are the anterior pituitary cells
- hypothalamus contains capillary beds that take in hormones produced by the hypothalamus itself (also
produced by neurosecretory cells, but the kind entirely within the hypothalamus)
- these hormones are often referred to as releasing hormones (e.g. gonadotropin-releasing hormone, GnRH)
- capillary beds join together into a blood vessel (portal vein) extending down into the anterior pituitary
- the portal vein branches into a second capillary bed that allows the releasing hormones to leave the bloodstream for their target cells (anterior pituitary cells)
- releasing hormones stimulate the anterior pituitary cells
to secrete specific hormones
78
how hormones control milk secretion
- the pituitary hormones prolactin (anterior) and oxytocin (posterior)
- during pregnancy, increasing prolactin levels → development of milk-producing cells
- naturally high levels of oestrogen during pregnancy inhibit those cells from releasing milk
- after birth, 2 things occur: drastically lowered levels of oestrogen (due to birth), and high levels of oxytocin (needed to stimulate uterine contractions)
- without oestrogen to inhibit, milk-producing cells begin releasing milk
- oxytocin stimulates contraction of smooth muscle tissue surrounding milk ducts → milk ejection
- production of both hormones is increased by the stimulation of the nipple caused by a suckling infant
- i.e. positive feedback
79
examples of hormones produced by pituitary gland
- LH
- FSH
- ADH
- prolactin
- oxytocin
