Communication and homeostasis Flashcards
(122 cards)
1
Q
What is homeostasis?
A
The maintenance of a constant internal environment
2
Q
Why is it important to maintain a core body temperature?
A
- If the body temperature is too high then enzymes may denature - the enzyme vibrates too much which breaks the H bonds causing a change in 3D structure.
- If temperature is too low then enzyme activity is reduced.
3
Q
Why is it important to maintain a constant pH?
A
- If blood pH is too high or too low enzymes become denatured.
- The hydrogen bonds are broken so the 3D structure is changed, causing the active site to change shape.
- Metabolic reactions are slowed.
4
Q
Why is it important to maintain a constant concentration of glucose in the blood?
A
- Too high = water potential of blood is reduced, water diffuses out of the cell and cells shrivel up and die.
- Too low = cell can’t carry out normal activities because there isn’t enough glucose for respiration to provide energy.
5
Q
What is negative feedback?
A
Receptors detect when a level is far from the optimum level and the information is passed to an effector via the nervous or hormonal system. The effector responds to counteract the change, bringing the level back to normal.
6
Q
When does the negative feedback mechanism stop working?
A
If the change of a level is too big then the effectors may not be able to counteract the change.
7
Q
What is positive feedback?
A
Effects respond to further increase the level away from the normal level. Useful to rapidly activate something.
8
Q
Examples of positive feedback
A
Widening of the cervix during birth
Hypothermia
9
Q
Which factors must be controlled in the blood?
A
Glucose concentration
Water
Ions
Proteins
10
Q
What is a hormone?
A
Chemicals that travel in the blood plasma towards target cells.
11
Q
What hormones control glucose concentration?
A
Insulin
Glucagon
12
Q
Where are insulin and glucagon secreted from?
A
Islets of Langerhans in the pancreas.
13
Q
Which cells secrete glucagon and which cells secrete insulin?
A
Glucagon = alpha cells
Insulin = beta cells
14
Q
Which factors influence blood glucose concentration?
A
Eating food containing carbohydrates
Exercising as more glucose is used in respiration to release energy.
15
Q
What is glycogenolysis?
A
Glycogen is broken down into glucose.
16
Q
What is glycogenesis?
A
Glucose is converted into glycogen.
17
Q
What is gluconeogenesis?
A
Glucose is formed from glycerol and amino acids.
18
Q
What effect does insulin have?
A
Lowers blood glucose concentration.
19
Q
How does insulin lower blood glucose concentration?
A
1) Binds to specific receptors on liver and muscle cells.
2) Increases the permeability of muscle-cell membranes to glucose by creating more channel proteins.
- vesicles containing glucose transporters move towards the membrane and fuse with it when insulin binds, forming more channel proteins.
3) Activates enzymes in liver and muscle cells that convert glucose into glycogen.
4) The cells can store glycogen as an energy source in the cytoplasm.
5) Also increases the rate of respiration of glucose, especially in muscle cells.
20
Q
What effect does glucagon have on blood glucose concentration?
A
Raises blood glucose concentration.
21
Q
How does glucagon increase blood glucose concentration? (second messenger model)
A
1) Binds to its specific receptors on the liver cell.
2) Activates an enzyme called adenylate cyclase.
3) This converts ATP into cyclic AMP (cAMP), the second messenger.
4) cAMP activates the enzyme protein kinase A.
5) Protein kinase A activates a chain of reactions which break glycogen into glucose.
22
Q
How does adrenaline increase glucose blood concentration?
A
Uses the same second messenger model as glucagon. Also inhibits glycogenesis and activates glycogenolysis, and activates glucagon secretion. More glucose is made available to the muscles for respiration.
23
Q
What is the negative feedback mechanism for the detection of low blood glucose?
A
1) Blood glucose falls.
2) Detected by alpha cells in islets of Langerhans.
3) Glucagon secreted.
4) Detected by target cells (hepatocytes and muscle cells).
5) Glucose formed by glycogenolysis and decreased respiration.
24
Q
What is the negative feedback mechanism for the detection of high blood glucose?
A
1) Blood glucose rises.
2) Detected by beta cells in islets of Langerhans.
3) Insulin secreted.
4) Detected by target cells (hepatocytes).
5) Glucose removed from blood by glycogenesis and increased respiration.
25
What is Type 1 diabetes?
1) The immune system attacks the beta cells in the islets of Langerhans.
2) They can't produce insulin.
26
What is hyperglycaemia?
When blood glucose level rises and stays high after eating. The kidneys can't reabsorb all the glucose so some is excreted in urine.
27
How is Type 1 diabetes treated?
Insulin therapy - Regular insulin injections throughout the day or insulin pumps which deliver a constant supply of insulin.
28
What is hypoglycaemia?
A big drop in blood glucose levels. Can be dangerous so insulin therapy has to be controlled.
29
What is Type 2 diabetes?
1) Beta cells don't produce enough insulin.
2) Or body cells don't respond to insulin.
3) The insulin receptors don't work.
4) Blood glucose concentration is higher than normal.
30
How is Type 2 diabetes treated?
Regular exercise and a balanced diet. Glucose-lowering medication is taken if needed. Eventually insulin injections may be needed.
31
How do you reduce the risk of getting type 2 diabetes?
Eat a balanced diet, low in fat, sugar and salt. Regular exercise. Lose weight.
32
How can you determine the concentration of a glucose solution?
1) Colorimetry of known samples.
2) Plot a calibration curve of absorbance against concentration.
3) Test unknown solution.
4) Compare to the graph.
33
What is the function of the kidneys?
1) Excrete waste products.
2) Regulate the water potential of blood.
3) Ultrafiltration.
4) Selective reabsorption.
34
What is the structure of a nephron?
35
What is the glomerulus?
A bundle of capillaries looped inside a hollow ball called a Bowman's capsule.
36
What is the afferent arteriole?
Takes blood into the glomerulus.
37
What is the efferent arteriole?
Takes filtered blood away from the glomerulus.
38
Why is the efferent arteriole smaller in diameter?
Allows the blood in the glomerulus to be under high pressure.
39
What is ultrafiltration?
Substances are filtered out of the blood and passed into tubules that surround the capillaries.
40
How is blood filtered through the nephron?
1) Blood from the renal artery enters small arterioles in the cortex of the kidney.
2) Each arteriole splits into a glomerulus.
3) The high pressure from the efferent arteriole forces liquid and small molecules in the blood out of the capillaries and into the Bowman's capsule.
4) The substances that enter the Bowman's capsule are called the glomerular filtrate - this passes along the rest of the nephron and useful substances are reabsorbed.
5) Large molecules like proteins and blood cells stay in the blood as they are too large.
6) The final filtrate flows through the collecting duct and passes out of the kidney along the ureter.
41
What is selective reabsorption?
1) Useful substances leave the tubules of the nephrons and enter the capillary network that wrapped around them.
2) The epithelium of the wall of the proximal convoluted tubule (PCT) has microvilli for the reabsorption of useful materials from the glomerular filtrate.
3) Useful solutes like glucose are reabsorbed along the PCT by active transport and facilitated diffusion.
4) Water enters the blood via osmosis because the water potential of blood is lower than that of the filtrate.
5) Water is reabsorbed from the PCT, loop of Henle, distal convoluted tubule (DCT) and the collecting duct.
6) The filtrate which remains is urine which passes along the ureter to the bladder.
42
Where does selective reabsorption take place?
As glomerular filtrate flows along the proximal convoluted tube (PCT), through the loop of Henle and along the distal convoluted tube (DCT).
43
What is urine made up of?
Water and dissolved salts
Urea
Hormones and excess vitamins
44
What is osmoregulation?
The maintenance of water potential of the blood.
45
What happens if the water potential of blood is too high?
Less water is reabsorbed via osmosis into the blood from the tubules of the nephrons. This means that urine is more dilute.
46
What happens if the water potential of blood is too low?
More water is reabsorbed by osmosis into the blood from the tubules of the nephron. Urine is more concentrated.
47
Where is the loop of Henle located?
The medulla (inner layer of kidneys).
48
How does the loop of Henle maintain a sodium ion gradient?
1) At the top of the ascending limb, sodium ions are pumped out into the medulla using active transport.
2) The ascending limb is impermeable to water, so water stays in the tubule, creating a low water potential in the medulla.
3) This causes water to move out of the descending limb into the medulla, so the filtrate is more concentrated.
4) The water in the medulla is reabsorbed back into the blood through the capillary network.
5) Near the bottom of the ascending limb, sodium ions diffuse out of the medulla, further lowering the water potential.
6) Water moves out of the DCT via osmosis and is reabsorbed into the blood.
7) The first three stages increase the ion concentration in the medulla, thus lowering the water potential.
8) This causes water to move out of the collecting duct and be reabsorbed into the blood by the capillary network.
49
How is water reabsorption controlled by hormones?
1) When the water potential of blood decreases, water will move out of the cells by osmosis.
2) This causes the cell to decrease in volume, which then sends signals to the posterior pituitary gland.
3) This releases the hormone ADH into the blood.
4) More water is reabsorbed from the tubules into the medulla and into the blood via osmosis.
50
Which cells monitor the water potential of blood?
Osmoreceptors in the hypothalamus.
51
What does the hormone ADH do?
Causes the walls of the DCT and collecting duct to be more permeable to water when the water potential of blood decreases.
52
Adrenal glands
Endocrine glands located above the kidneys that produce adrenaline.
53
Adrenaline
A hormone produced by the adrenal glands that is involved in the 'fight or flight' response. It increases heart rate, blood pressure, blood flow to muscles and blood glucose levels.
54
Anti-diuretic hormone (ADH)
A hormone secreted by the pituitary gland that increases the collecting duct's permeability to water, allowing more water to be reabsorbed into the blood.
55
Assisted Reproductive Technology (ART)
A fertility treatment in which a woman's eggs are handled outside of the body.
56
Barrier method
A type of contraception that prevents the sperm and egg meeting, e.g. condoms, diaphragms.
57
Body mass index (BMI)
A value based on height and mass used to categorise an individual as underweight, normal weight, overweight or obese.
58
Bowman's capsule
The cup-like structure at the start of a nephron that surrounds the glomerulus. Small molecules, water and ions are forced into the Bowman's capsule during filtration.
59
Clomifene
A drug prescribed to women who do not ovulate regularly. It stimulates the secretion of more FSH and LH, triggering egg production and ovulation.
60
Collecting duct
The final section of the nephron in which water is selectively reabsorbed and urine is sent to the ureter. Its permeability to water is altered by ADH.
61
Combined pill
A contraceptive taken orally that contains both oestrogen and progesterone.
62
Contraception
A method or device used to prevent pregnancy.
63
Contraceptive injection
An injection that releases progesterone into the bloodstream to prevent pregnancy.
64
Contraceptive patch
A patch that releases both oestrogen and progesterone into the bloodstream through the skin to prevent pregnancy.
65
Corpus luteum
A temporary endocrine structure, formed from the remains of the follicle, that secretes progesterone.
66
Dermis
The layer of tissue below the epidermis. It contains temperature-sensitive receptors and sweat glands.
67
Diabetes
A condition where the homeostatic control of blood glucose levels stops working.
68
Dialysis
A medical procedure that artificially filters the blood of patients with kidney failure. It relies on a partially permeable membrane between the patient's blood and dialysis fluid.
69
Effector
An organ, tissue, or cell that produces a response to a stimulus.
70
Endocrine gland
Glands of the endocrine system that secrete hormones directly into the bloodstream.
71
Endocrine system
A network of glands that produce and secrete hormones into the bloodstream.
72
Epidermis
The outer layer of the skin.
73
Temperature-sensitive receptors
Structures that provide information about the external temperature.
74
Fight or flight response
A physiological reaction that occurs in response to stress where the body prepares to confront danger or flee from it.
75
Filtration
The removal of small molecules, water and ions from the blood in the glomerulus of the kidney at high pressure.
76
Follicle-stimulating hormone (FSH)
A hormone secreted by the pituitary gland that binds to follicle cells, stimulating them to mature and secrete oestrogen.
77
Glomerulus
A bundle of capillaries located in the capsule of a nephron adapted for the filtration of blood.
78
Glucagon
A hormone secreted by the pancreas when blood glucose concentration is too low. It causes the breakdown of glycogen to glucose in the liver.
79
Glycogen
A store of glucose in the liver and muscle tissues.
80
Homeostasis
The maintenance of a stable internal environment in the body despite fluctuations in internal and external conditions.
81
Hormone
A cell signalling molecule produced by endocrine glands and released into the blood. It travels to a target organ and binds to receptors on effectors, initiating a response.
82
Hypothalamus
A structure in the brain that contains the thermoregulatory centre. It coordinates information from the receptors and sends instructions to the effectors.
83
Insulin
A hormone secreted by the pancreas when blood glucose concentration is too high. It causes liver and muscle cells to increase their uptake of glucose and the conversion of glucose to glycogen in the liver.
84
In vitro fertilisation (IVF)
The fertilisation of an egg using sperm outside of the body. The zygote is allowed to grow and the resulting embryo is transferred to the uterus.
85
Kidney
One of a pair of organs in the abdomen that has a role in osmoregulation and nitrogenous excretion.
86
Luteinising hormone (LH)
A hormone secreted by the pituitary gland that initiates ovulation and stimulates the development of the remains of the follicle into a corpus luteum.
87
Menstrual cycle
The monthly cycle in women that involves the development of the uterus lining, ovulation, maintenance of the uterus lining and its shedding.
88
Menstruation
The shedding of the uterus lining that begins at day 1 of the menstrual cycle.
89
Metabolic rate
The rate at which biochemical reactions occur in cells.
90
Mini-pill
An oral contraceptive that contains progesterone only.
91
Negative feedback
A corrective mechanism that allows only small shifts from a set point, reversing a change in conditions.
92
Nephron
The functional unit of the kidney.
93
Oestrogen
A female sex hormone released by the ovaries that causes the growth and repair of the uterus lining. High levels of oestrogen stimulate a surge in LH production.
94
Osmoregulation
The maintenance of constant water levels in the body fluids of an organism.
95
Ovaries
A pair of endocrine glands in females that secrete oestrogen into the bloodstream.
96
Ovulation
When an ovary releases an egg at around day 14 of the menstrual cycle.
97
Pancreas
An endocrine gland situated behind the stomach that produces insulin.
98
Pituitary gland
An endocrine gland that produces hormones which control other glands (e.g. adrenal glands). Often described as the 'master gland'.
99
Progesterone
A female sex hormone secreted by the corpus luteum that maintains the uterus lining. It also inhibits FSH and LH release.
100
Receptor
A specialised structure that detects a specific type of stimulus.
101
Renal arteries
Blood vessels that carry oxygenated blood to the kidneys.
102
Renal veins
Blood vessels that drain the kidneys.
103
Selective reabsorption
The selective reuptake of useful substances (all sugars, some water and some ions) into the blood. This takes place along the nephron.
104
Shivering
The involuntary contraction of muscles which generates heat from respiration.
105
Testes
A pair of endocrine glands in males which secrete testosterone into the bloodstream.
106
Thermoregulation
The maintenance of core body temperature.
107
Thermoregulatory centre
An area of the hypothalamus that regulates body temperature. It contains receptors sensitive to blood temperature.
108
Thyroid gland
An endocrine gland located in the neck that produces thyroxine.
109
Thyrotropin-releasing hormone (TRH)
A hormone secreted by the hypothalamus when blood thyroxine levels are lower than normal. It stimulates the pituitary gland to release TSH.
110
Thyrotropin-stimulating hormone (TSH)
A hormone secreted by the pituitary gland that stimulates the thyroid gland to release thyroxine.
111
Thyroxine
A hormone secreted by the thyroid gland that controls metabolic rate, heart rate and temperature.
112
Transplant
A medical procedure in which an organ or tissue in an individual is replaced.
113
Type 1 diabetes
A type of diabetes in which the pancreas fails to produce enough insulin. It is controlled using daily insulin injections, limiting refined sugar intake and getting regular exercise.
114
Type 2 diabetes
A type of diabetes in which a person develops insulin resistance or doesn't produce enough insulin. It is often due to obesity and is controlled by eating a balanced diet and getting regular exercise.
115
Urea
A chemical produced from the breakdown of excess amino acids in the liver.
116
Ureter
A tube that takes urine to the bladder from the kidneys.
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Urethra
A tube that releases urine from the bladder, out of the body.
118
Urinary system
The body's drainage system that removes waste materials. It consists of the kidneys, the ureters, the bladder and the urethra.
119
Urine
The waste product of the kidney that contains urea, excess water and excess ions.
120
Vasoconstriction
Constriction of blood vessels near the surface of the skin. Less blood flows close to the skin surface, decreasing heat loss to the surroundings.
121
Vasodilation
Dilation of blood vessels near the surface of the skin. This allows blood to flow closer to the skin surface, increasing heat loss to the surroundings.
122
Waist-to-hip ratio
The ratio of the circumference of the waist to the circumference of the hips. It can be used to indicate abdominal obesity.
