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biology unit 1/2 > chapter 6 - homeostasis > Flashcards

chapter 6 - homeostasis Flashcards

unit 1 aos 2

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1
Q

homeostasis

A

a process that maintains the internal environment of an organism within set limits so that cells and systems can function properly

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2
Q

parameters that affect the functioning of cells

A

-temperature (36.5-37.5 c)
-pH (7.35-7.45)
-blood sugar levels (4.0-7.8 mmol/L)
-sodium concentration (135-145 mmol/L)
-potassium concentration (3.5-5.0 mmol/L)
-fluid balance

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3
Q

homeostatic mechanisms

A

-stimulus response model
-positive feedback loop
-negative feedback loop

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4
Q

stimulus response model stages

A

stimulus-receptor-modulator-effector-response

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5
Q

stimulus

A

change in external or internal environment of an organism

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6
Q

receptor

A

stimulus is detected by receptors which transfers it into a chemical or electrical signal for transmission to the modulator

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7
Q

modulator

A

compares info from receptors with ideal condition that the body aims to maintain, then releases molecules that alter the functioning of effector

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8
Q

effector

A

a molecule, cell, or organ that responds to a signal and produces a response

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9
Q

response

A

any change in the function of a target cell, organ, or organism after stimulation from an initial response

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10
Q

types of receptors

A

-thermoreceptors: detect changes in temperature
-nociceptors: detect painful stimuli
-baroreceptors: detect changes in pressure
-chemoreceptors: detect changes in chemical concentration
-photoreceptors: detect changes in light

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11
Q

positive feedback system

A

-when the response increases the initial stimulus (eg production of breast milk)

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12
Q

negative feedback system

A

-occurs when the response counters the stimulus (response attempts to revert system back to the state before the stimulus occurred)
-usually overcompensates, therefore another negative feedback loop is created

eg when temperature rises, body responds by sweating to lower body temp

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13
Q

cellular signalling

A

-at a cellular level, the stimulus response model is represented as a 3 step process

1: reception (the detection of stimulus and transmitting of this stimulus into a mechanical, electrical, or chemical signal)

2: transduction (transmission of a signal. this stage includes everything up to the final response)

3: response - by effector (the change in the function of a target cell, organ, or organism)

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14
Q

how does heat travel?

A

from a region of high temp to low temp

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15
Q

types of heat transfer

A

-conduction
-convection
-evaporation
-radiation

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16
Q

conduction

A

the transfer of heat through physical contact with another object

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17
Q

convection

A

the transfer of heat via the movement of a liquid or gas between areas of a different temperature

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18
Q

evaporation

A

the loss of heat via the conversion of water from liquid to gas form

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19
Q

radiation

A

the transfer of heat via electromagnetic waves such as light (doesn’t require physical contact)

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20
Q

two groups of thermoregulation

A

-endotherms (warm blooded) are able to generate the majority of their heat energy internally using metabolic processes

-ectotherms (cold blooded) produce very little metabolic energy and instead rely on environmental sources of heat to warm themselves

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21
Q

overall body temperature

A

-is a balance of the heat being put into the system, the heat generated within a system, and the heat lost by the system

total heat change = heat in + metabolic heat - heat out

22
Q

what happens when it’s too hot?

A

-the hypothalamus sends signals to different effectors, which produce responses which aim to increasing the amount of heat lost to the environment and decreasing the amount of heat produced by the body

23
Q

effectors and responses for an increase in body and/or environmental temperature

A

-sweat glands = sweating
-small blood vessels in skin = dilation of arterioles
-cerebral cortex = change in behaviour
-arrector pili muscles = flattening in hair
-cells = decrease in metabolic rate

24
Q

what happens if it’s too cold

A

-the body detects changes and signals the hypothalamus, which aims to increase the amount of heat produced by the body

25
Q

effectors and responses for an decrease in body and/or environmental temperature

A

-skeletal muscle cells = shivering
-small blood vessels in skin = constriction of arterioles
-cerebral cortex = change in behaviour
-arrector pili muscles = lifting of hair
-cells = increase in metabolic rate
-brown fat = burning of triglycerides

26
Q

how is glucose used in the body?

A

-we get glucose from eating carbohydrates, which are broken down in the digestive system
-glucose is then absorbed by the small intestine and released into the blood stream via glucose transporters
-glucose can travel around the body (in blood plasma), where it is taken up by cells
-in the cells the process of cellular respiration breaks glucose into smaller parcels of energy, which powers the cell

27
Q

glycogen

A

-a long series of glucose molecules joined together which can be stored for a long period of time
-is another source of glucose

28
Q

how is glycogen produced and broken down?

A

-produced through glycogenesis
-broken down into glucose via glycogenolysis

29
Q

what happens when blood glucose levels increase?

A

-when islet of langerhans detect high blood glucose, beta cells release insulin

30
Q

pathways of insulin

A

-skeletal muscles and fat cells absorb more glucose from the blood

-liver cells are stimulated to convert more glucose to glycogen

31
Q

what happens when blood glucose levels decrease?

A

-when islet of langerhans detect low blood glucose, alpha cells secrete glucagon
-glucagon stimulates liver cells to break down glycogen into glucose and release it into the blood stream via glycogenesis

32
Q

osmoregulation

A

regulation of water balance so cells can function properly

33
Q

osmolality

A

the total concentration of solute in a given weight of water

34
Q

regulating water balance

A
  • total water change = water in + metabolic water - water out
    -ideally, water in + metabolic water should be equal to water out (no net loss)
35
Q

what happens when water levels decrease?

A

-ADH and renin increase the reabsorption of water from kidney filtrate back into the bloodstream

–increase in osmolality = pathway involving release of ADH
–decrease in blood pressure = pathway involving release of renin

-both of these pathways lead to increased reabsorption of water from kidney filtrate and increase in consumption of fluid

36
Q

what happens when water levels increase?

A

-the secretion of ADH is supressed, increasing the amount of water excreted by the kidneys in urine
-when ADH is supressed this leads to a decrease in reabsorption of water from urine, and a decrease in the consumption of fluid

37
Q

ADH

A

-antidiuretic hormone
-causes kidneys to release less water, decreasing the amount of urine produced

38
Q

what is type 1 diabetes and how does it occur?

A

-occurs after an autoimmune response causes the immune system to destroy insulin secreting beta cells in the pancreas using autoantibodies
-as a result people produce little to no insulin, meaning their blood glucose levels are also unregulated (alpha cells are impaired and can’t function properly)

39
Q

what is hyperglycaemia?

A

-high blood sugar

40
Q

short term symptoms of hyperglycaemia

A

-increased urination and excessive thirst
-excessive hunger and lethargy
-weight loss

41
Q

long term symptoms of hyperglycaemia

A

-vision loss
-heart disease and stroke
-tingling or numbness
-prolonged wound healing
-kidney damage

42
Q

what is hypoglycaemia and how does it occur?

A

-low blood glucose
-occurs when blood sugar levels drops below 4.0 mmol/L
-impaired alpha cells means they don’t produce normal amounts of glucose in periods of fasting, and without enough glucose, cells don’t have enough energy to function

43
Q

how is type 1 diabetes managed?

A

-manual maintenance of blood glucose through insulin replacement therapy
-this involves patients artificially altering insulin levels via monitoring, injections, pumps etc

44
Q

hyperthyroidism

A

-a condition caused by an overactive thyroid gland, causing increased amounts of thyroid hormones to be secreted in the body

45
Q

thyroid gland

A

-a small butterfly shaped gland located in the base of the neck
-secretes T3 (triiodothyronine) and T4 (thyroxine), which are both made from amino acid tyrosine and iodine

46
Q

what does the thyroid gland stimulus response model involve?

A

-in a healthy individual, the hypothalamus periodically releases TRH (thyrotropin-releasing hormone)
-anterior pituitary gland is stimulated to secrete TSH (thyroid-stimulating hormone)
-T3 and T4 inhibit secretion of TRH and TSH via negative feedback

47
Q

what happens when thyroid hormone levels in the blood increase?

A

both the hypothalamus and pituitary gland release less TRH and TSH respectively

48
Q

what happens when thyroid hormone levels in the blood decrease?

A

both the hypothalamus and pituitary gland release more TRH and TSH respectively

49
Q

causes of hyperthyroidism

A

-one of the most common causes is grave’s disease, which causes a production of an autoantibody called TSI (thyroid-stimulating immunoglobulin)
-this autoantibody binds to TSH receptors, stimulating the release of T3 and T4, meaning that these people have elevated levels of thyroid hormones

50
Q

symptoms of hyperthyroidism

A

-are pretty varied as thyroid hormone can affect lots of cells
-can include increased metabolism, heat intolerance, sweating, increased heart rate, weakness

51
Q

management of hyperthyroidism

A

can be managed via:
-medications: beta blockers (reduce heart rate) or anti thyroid drugs (reduce production of thyroid hormones
-radioactive iodine: kills cells in thyroid gland
-thyroid gland can be surgically removed

some treatments can result in hypothyroidism, so artificial hormones may need to be taken

biology unit 1/2 (9 decks)

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