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CIE Biology A1 > T14 Homeostasis > Flashcards

T14 Homeostasis Flashcards

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1
Q

homeostasis

A

the relatively constant internal state of an organism, even when the external environment is changing.

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2
Q

receptor role

A

detects a change in external stimuli and sends an impulse to the control centre

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3
Q

control centre role

A

receives impulse and coordinates a response by sending message to effector

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4
Q

effector response

A

responds to the message from the control centre and brings about the appropriate response

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5
Q

mechanisms operating to restore homeostasis after infection by pathogen

A

production of antibodies against antigens (humoral)
T cell production recognising antigens of the pathogen (cell-mediated)
inflammatory response
fever
antimoicrobial substance production
phagocytosis of pathogen

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6
Q

mechanisms to respond to stimuli

A

hormonal (endocrine glands)

nervous (direct stimulation of nerves by sensory receptor

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7
Q

mechanisms by which water and ion balance are maintained

A

digestive organs and hormones take in ions from food and drink to replace lost
kidneys regulate fluid and ions. ADH causes more water absorption by the kidneys and is released when blood volume is low

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8
Q

mechanisms by which respiratory gases are regulated during exercise

A

breathing rate increase (^^ loading and unloading)

heart rate increase

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9
Q

negative feedback in calcium homeostasis

A

Low Ca stimulates release of PTH from parathyroid glands which stimulates kidneys to reabsorb more calcium into blood from urine and release of Ca from bone.

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10
Q

PTH

A

parathyroid hormone

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11
Q

negative feedback in stomach emptying

A

food is eaten, and stretches stomach wall which activates stretch receptors and smooth muscle contracts, so is mixed and emptied from stomach and stretch receptors are deactivated

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12
Q

negative feedback mechanisms

A

self-correcting and counteracts change away from a set normal to reduce fluctuations to stabilise systems.

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13
Q

what does the hormone oxytocin do

A

intensifies contractions in childbirth and leads to milk release in mothers

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14
Q

interleukins

A

stimulate the hypothalamus to increase prostaglandin production which increases body temp

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15
Q

biological role of positive feedback loops

A

amplifies a physiological process to bring about a particular response

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16
Q

example of positive feedback loops

A

fever
oxytocin production
ovulation

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17
Q

why is positive feedback unstable

A

causes escalation in physiological response, pushing past physiological range vs negative feedback which is self-correcting

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18
Q

control of ovulation from feedback mechanisms

A

oestrogen released by the ovaries, stimulating the hypothalamus to release GnRH and pituitary to release LH
rise in LH stimulates release of more oestrogen from ovary and stimulates ovulation and rupured follicle forms a corpus luteum which secretes oestrogen and progesterone and GnRH release is inhibited

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19
Q

nervous system response

A

rapid, short-lived responses via electrical signals between adjacent cells
usually is the contraction of a muscle or secretion from a gland

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20
Q

endocrine system reponse

A

slow, long-lasting response through hormones in the blood.

usually is a change in metabolic activity in a target cell

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21
Q

where’s the temperature regulation centre found?

A

in the hypothalamus

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22
Q

set temperature of humans

A

36.7 degrees celsius

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23
Q

hypothalamus role in thermoregulation

A

detects movement away from optimum temp and coordinates responses to counteract the change in temp

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24
Q

mechanisms to reduce body temp

A

relaxation of erector muscles, increased blood flow to surface of skin, sweating, decreased metabolic rate

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25
Q

mechanisms to increase body temp

A

shivering, erector muscle contraction, increased metabolic rate, adrenaline and thyroxine release to release energy from the liver, decreased blood flow to skin

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26
Q

sweating

A

decreases temp by evaporation using body’s heat energy, is released by sweat glands to external layer of skin

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27
Q

how does temperature of vaporisation affect feeling on skin

A

lower temp of vaporisation allows for quicker heat absorption from skin

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28
Q

feedback mechanism regulating body temp

A

thermoreceptors (hot and cold) detect changes in temp below 35.8 or above 37.5 degrees celsius and send a message to the hypothalamus which then coordinates a response and sends an electrical signal to an effector (eg, blood vessels or sweat glands).

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29
Q

liver role in homeostasis

A

metabolises proteins and stores/detoxifies hormones/poisons.

30
Q

aspects of protein metabolism in the liver

A

deamination/ transamination of amino acids, ammonia removal from the body by urea synthesis, amino acid synthesis, synthesises plasma proteins (eg, albumins, globulins, and blood clotting proteins

31
Q

storage and detoxification in the liver

A

small intestine outputs hepatic portal blood to be used in haemoglobin breakdown (producing iron to blood). also produces minerals and vitamins to store. blood outputs toxins and hormones to be broken down by liver cells or detoxified.

32
Q

protein metabolism in the liver

A

small intestine outputs amino acids which then goes on to be deaminised, transaminised or used in protein synthesis to produce urea, plasma proteins or new amino acids to be put into the blood.

33
Q

deamination

A

removal of NH2

34
Q

transamination

A

transfer of NH2

35
Q

aspects of protein metabolism in the liver

A

deamination
transamination
protein

36
Q

waste products from deamination

A

keto acids and an amino group is formed. the keto acids feed into the krebs cycle and are oxidised to form ATP and the amino group is converted to ammonia and reacts w carbon dioxide to enter the ornithine cycle to produce urea.

37
Q

consequences of a faulty ornithine cycle

A

leads to a build-up of ammonia and could be fatal.

38
Q

where does the kidney get a plentiful blood supply from?

A

the renal artery

39
Q

urinary system role

A

filters the blood and removes waste, to produce urine.

40
Q

nephron

A

selective filter element of kidney, filtering blood plasma.

comprises of a renal corpuscle and associated tubules and ducts, producing urine via ultrafiltration.

41
Q

structure of the kidney

A

bean shaped organ surrounded by a fibrous membrane. divided into an outer cortex and inner medulla. renal pyramids end in small ducts (papillae which open into calyces of ollecting channels. with inner medullas alternated with renal pyramids and nephrons with collecting ducts facing inwards to the renal pelvis. a ureter drains out of the kidney leading to the bladder.

42
Q

nephron role in excretion

A

produces filtrate of the blood, modifies the filtrate and produced a final excretory fluid as urine.

43
Q

ultrafiltration

A

forcing fluid and dissolved substances through a membrane by pressure

44
Q

where does ultrafiltration occur in the nephron

A

in the first part of the nephron, across the capillary membranes and the glomerular capsule.

45
Q

effect of blood pressure and the formation of glomerular filtrate`

A

increasing pressure increases filtration rate, decreasing pressure decreases filtration rate

46
Q

how is urine modified

A

via secretion and tubular reabsorption according to physiological needs

47
Q

renal corpuscle

A

blood is filtered and filtrate enters convoluted tubule

filtrate contains water, glucose, urea, ions/ no cells or large proteins

48
Q

proximal convoluted tubule

A

reabsorption of most of filtrate, including glucose and ions

49
Q

loop of henle

A

salt transport and passive movement of water create salt gradient through kidney, water transported away by blood vessels around nephron.

50
Q

distal convoluted tubule

A

filtrate further modified by active reabsorption and secretion of ions

51
Q

collecting duct

A

water leaves the filtrate via osmosis, so is more concentrated. loop of henle salt gradient allows water to be removed along entire length of the collecting duct.

52
Q

podocytes

A

specialised cells making up epitheliuim of bowman’s capsule, wrapping around capillaries of the glomerulus and plasma filtrate passes through filtration slits between them

53
Q

role of glomerular filtration

A

produces initial filtrate of the blood that can be modified be modified later on

54
Q

role of active secretion

A

allows to rid of unwanted substances and maintain salt gradient

55
Q

role of osmosis in kidney nephron

A

allows urine to be concentrated

56
Q

purpose of the salt gradient in the kidney

A

allows water to be withdrawn from the urine in order to maintain the osmotic gradient which withdraws water from the urine

57
Q

how is the salt gradient produced by the kidney

A

via the active and passive movement of salt from the filtrate into the extracellular fluid in the medulla

58
Q

hormones that affect the volume and composition of urine

A

ADH and aldosterone

59
Q

where is ADH produced

A

the posterior pituitary gland

60
Q

where is aldosterone produced

A

in the adrenal cortex

61
Q

ADH function

A

regulates water reabsorption from the collecting duct

62
Q

aldosterone function

A

regulates sodium absorption from kidney tubules

63
Q

where are osmoreceptors found

A

in the hypothalamus

64
Q

factors causing ADH release

A 
low blood volume
more negative water potential
high blood sodium levels
low fluid intake
nicotine and morphine
65
Q

factors inhibiting ADH release

A

high blood volume
less negative water potential
low blood sodium levels
alcohol

66
Q

factors causing release of aldosterone

A

low blood volumes

mediated via complex pathway between osmoreceptors, kidney glomeruli and the hormone renin

67
Q

process by which urine output is controlled

A

low blood volume (high osmotic pressure) stimulates osmoreceptors which send signals to neurosecretory cells to synthesise and release ADH from pituitary. arterioles constrict to increase blood pressure and sweat glands decrease activity and water reabsorption increases from collecting ducts. blood volume is restored and detected by osmoreceptors

68
Q

what happens to urine and blood volume when ADH is released

A

urine vol decreases and blood volume increases

69
Q

what happens to urine and blood volume when ADH is inhibited

A

blood volume decreases, urine volume increases

70
Q

effect of aldosterone on nephron

A

increases reabsorption of sodium into the nephron kidney tubules so that theres is more sodium in the blood, maintaining the salt gradient so that the osmotic tendencies of the liver are maintained. also leads to more water being reabsorbed so the blood volume increases

71
Q

minimum atomic mass required to go through membrane within nephron

A

69000 RPM

CIE Biology A1 (15 decks)

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