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HUBS191 P2 > homeostasis > Flashcards

homeostasis Flashcards

1
Q

homeostasis

A

the presence of a relatively stable internal environment

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2
Q

normal range is?

A

an individual’s normal range within which their levels of a given variable fluctuate

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3
Q

reference range is?

A

the populations reference range based on the breadth of individual normal ranges within a population. the population reference range tends to be wider than normal fluctuations within an individual:

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4
Q

features of neural (aka synaptic) control system (4 features)

A
  • action potentials in axons and neurotransmitter release at synapse
  • targeting achieved by specific ‘wiring’
  • fastest transmission speed (compared to endocrine), to minimise response delays
  • good for brief responses
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5
Q

features of endocrine control system (3 features)

A
  • hormones released into the blood
    targeting by presence of specific receptors on target cells
  • relatively slow, but long lasting action
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6
Q

endocrine system (secrete-travel-target) consists of (4 facts)

A
  • endocrine gland cells that secrete hormones
  • these are carried in the bloodstream to the target cells upon which they act
  • target cells are mainly in other distant tissues and organs
  • target cells must have appropriate receptors
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7
Q

major endocrine glands

7 glands

A 
hypothalamus
pituitary gland
thyroid gland
adrenal gland
pancreas (pancreatic islets)
pineal gland
parathyroid glands
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8
Q

hypothalamus does?

A

links the nervous system to the endocrine system and controls the secretion of many endocrine glands

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9
Q

organs with secondary endocrine functions

5 organs

A 
heart
thymus
digestive tract
kidneys
gonads - testis, ovary
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10
Q

hormones

A

true hormones are chemical messengers produced in one location and transported via the bloodstream to a second location (target cells) where they cause a response in those cells

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11
Q

specificity of hormone action

what is the only thing a hormone can affect?

A

a hormone can only affect cells with specific receptors for that hormone. each receptor is a protein. it can be in the target cell membrane or inside the target cell

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12
Q

water soluble hormones

chemical classification

A

mostly peptides (75% of hormones), some catecholamines include adrenaline and noradrenaline

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13
Q

water soluble hormones

storage classification

A

made and stored until required (released by exocytosis)

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14
Q

water soluble hormones

transport classification

A

travel dissolved in the blood

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15
Q

water soluble hormones

receptors classification

A

cell surface

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16
Q

water soluble hormones

mechanism of action classification

A

through 2nd messengers

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17
Q

water soluble hormones

speed of response classification

A

milliseconds to minutes

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18
Q

Lipid (fat) soluble hormones

chemical classification

A

steroids

thyroid hormones including both T3 and T4

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19
Q

Lipid (fat) soluble hormones

storage classification

A

steroids are made from cholesterol as required

thyroid hormones are made in thyroid cells and stored until required

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20
Q

Lipid (fat) soluble hormones

transport classification

A

travel in blood bound to a carrier protein

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21
Q

Lipid (fat) soluble hormones

receptors classification

A

intracellular receptors in cytoplasm or nucleus

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22
Q

Lipid (fat) soluble hormones

mechanism of action classification

A

by altering gene transcription

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23
Q

Lipid (fat) soluble hormones

speed of response classification

A

hours to days

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24
Q

where are the water soluble hormone receptors located?

A

cannot cross the cell membrane, therefore receptors are located in target cell/plasma membrane

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25
Q

where are the lipid soluble hormone receptors located?

A

can diffuse across the cell membrane into the target cell, therefore receptors are located in the cytoplasm or nucleus

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26
Q

cellular response to receptor activation

water soluble hormones (4 steps)

A
  1. water soluble hormone binds to cell surface receptor
  2. hormone binding allows activation of associated G-protein
  3. G-protein activates/inhibits second messenger production/reduction
  4. downstream proteins/pathways are activated or deactivated
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27
Q

cellular response to receptor activation

lipid soluble hormones (8 steps)

A
  1. lipid soluble hormone dissociates from carrier protein
  2. hormone diffuses across cell membrane
  3. hormone binds to intracellular receptor
  4. hormone-receptor complex acts as a specific transcription factor
  5. target gene is generated
  6. new mRNA is generated
  7. new protein is generated by translation of mRNA
  8. new protein mediates cell specific response (slow process)
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28
Q

maintenance of hormone levels for?

A

need to maintain hormone levels to maintain effects of hormones

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29
Q

maintenance of hormone levels

negative feedback

A

most common

reduce change until stimulus is removed or directly inhibit further release

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30
Q

maintenance of hormone levels

positive feedback

A

occasionally

amplification of change until a desired outcome is achieved

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31
Q

control of hormone secretion is?

A

amount of hormone depends on rate of hormone secretion, rate of removal from blood

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32
Q

control of hormone secretion

what is secretion usually controlled by?

A

negative feedback loops, most use negative feedback control

33
Q

control of hormone secretion

what does deviation do?

A

occurs in a system and is detected by a ‘receptor’ and recognised by a control centre (sometimes the same organ is the ‘receptor’ and control centre, sometimes they are different).

34
Q

control of hormone secretion

a mechanism is activated to?

A

bring the variable back to the set point (or reference range), change occurs in effectors

35
Q

control of hormone secretion

in the long term, the secretion rates of many hormones?

A

are maintained at a fairly constant level by negative feedback

36
Q

control of hormone secretion

a few hormones use?

A

positive feedback (at specific times)

37
Q

control of hormone secretion

the goal of hormones is to?

A

maintain homeostasis

too much or too little hormone can lead to endocrine disorders

38
Q

pancreas

A

an exocrine gland and an endocrine gland

39
Q

pancreatic islets

A

~1% of mass
beta cells secrete insulin
alpha cells secrete glucagon

40
Q

energy utilisation and storage

blood glucose concentration must be?

A

maintained within a narrow range at all times for normal functioning (homeostasis)

41
Q

energy utilisation and storage

diabetes develops if?

A

blood glucose concentration is too high for too long

42
Q

energy utilisation and storage

hypoglycemia occurs if?

A

blood glucose concentration is too low

43
Q

energy utilisation and storage

what must the brain be supplied with at all times and why?

A

glucose as glucose is the only fuel that the brain uses

44
Q

energy utilisation and storage

why do blood glucose levels fluctuate throughout the day?

A

because we use fuel continuously but eat intermittently

45
Q

energy utilisation and storage

two metabolic states

A

fed state

fasting state

46
Q

energy utilisation and storage

fed state

A

cellular uptake of nutrients and anabolic metabolism

synthesis of glycogen, protein and fat

47
Q

energy utilisation and storage

fasting state

A

mobilisation of nutrients and catabolic metabolism

breakdown of glycogen, protein and fat

48
Q

hormone regulation

A

insulin and glucagon maintain blood glucose concentration between 70-110 dL-1

49
Q

pituitary gland

location

A

base of the brain and attached to the hypothalamus

50
Q

pituitary gland

controls the?

A

secretion of pituitary hormones (when activated by neural input, the hypothalamus stimulates the pituitary gland to secrete hormones)

51
Q

pituitary gland
what do pituitary hormones do?
(2 jobs)

A

some stimulate target cells

some stimulate the secretion of hormones by other endocrine glands

52
Q

pituitary gland

two part of the pituitary gland are?

A

anterior lobe

posterior lobe

53
Q

pituitary gland
posterior lobe
connected to the hypothalamus by?

A

neurons - cell bodies in the hypothalamus

axons terminate in the posterior lobe

54
Q

pituitary gland
posterior pituitary hormones
3 facts

A

made in hypothalamus (cell body of the neuron)
travel down the axon
stored at the axon endings until required (peptide hormones)

55
Q

pituitary gland
posterior lobe
communication

A

hypothalamus uses neural communication with the posterior lobe to release hormones into the blood: increased (or decreased) frequency of action potentials leads to corresponding change in hormone release

56
Q

pituitary gland
posterior lobe
what two hormones can be released into the blood by means of the posterior lobe?

A

antidiuretic hormone (ADH
or
oxytocin

57
Q

pituitary gland
posterior lobe
antidiuretic hormone

A

stimulates kidneys to reabsorb water (the kidneys conserve water when the body dehydrates)

58
Q

pituitary gland
posterior lobe
oxytocin

A

stimulates the contraction of uterine muscles during childbirth (an example of positive feedback)
stimulates milk release in breastfeeding (milk ejection reflex)

59
Q

pituitary gland
posterior lobe hormones
made and stored where?

A

both hormones are made in the hypothalamus and stored in the posterior pituitary until required

60
Q

pituitary gland
anterior lobe
connected to the hypothalamus by?

A

blood vessels

hypothalamic hormones stimulate or inhibit release of stored hormones from specific anterior pituitary cells

61
Q

pituitary gland
anterior lobe
communication
3 steps

A

stimulus - neural input within hypothalamus
hypothalamus signals the anterior pituitary to release hormones by hormonal stimulation, secreting stored releasing hormone (or inhibiting hormone)
hormone binds to receptor on membrane of a specific cell type and a specific anterior pituitary hormone is secreted e.g. prolactin, growth hormone

62
Q

pituitary gland
anterior lobe
feedback regulation of the anterior pituitary gland
4 steps

A

hypothalamus releasing hormone —>
anterior pituitary gland releasing the pituitary hormone —>
target organ to release another hormone —>
hormone has an effect

63
Q

pituitary gland
anterior lobe
8 hormones

A 
GH-RH
GH-IH (SS)
TRH
PIH
PRH
PRL
GnRH
CRH
64
Q

pituitary gland
anterior lobe
GH-RH function, target gland, secretes?

A

stimulates release of growth hormone
liver
IGF-1

65
Q

pituitary gland
anterior lobe
GH-IH (SS) function

A

inhibits the release of growth hormone and TSH

66
Q

pituitary gland
anterior lobe
TRH function, target gland, secretes?

A

stimulates the release of TSH
thyroid
T3 and T4

67
Q

pituitary gland
anterior lobe
PIH function

A

inhibits the release of TSH and PRL

68
Q

pituitary gland
anterior lobe
PRH function, target gland, secretes?

A

stimulates the release of PRL
mammary
breast milk

69
Q

pituitary gland
anterior lobe
PRL function

A

inhibits the release of GnRH

70
Q

pituitary gland
anterior lobe
GnRH function, target gland, secretes?

A

stimulates the release of FHS and LH
gonads
estrogen and testosterone

71
Q

pituitary gland
anterior lobe
CRH function, target gland, secretes?

A

stimulates the release of ACTH
adrenal cortex
cortisol

72
Q

pituitary gland
anterior lobe
growth hormone
activity in the hypothalamus

A

one set of neurons will release the growth hormone releasing hormone and one set of neurons will release the growth hormone

73
Q

pituitary gland
anterior lobe
growth hormone
travels to?

A

the anterior pituitary gland where the growth hormone is released
then travels to the liver and causes it to release somatomedin C (IGF-1) which will cause effects in the body

74
Q

pituitary gland
anterior lobe
growth hormone
once the growth hormone has been released what feedback to we get and why?

A

negative feedback to the hypothalamus to limit GH-RH release

and negative feedback to anterior pituitary via stimulation of hypothalamus to release GH-IH

75
Q

pituitary gland
anterior lobe
growth hormone
direct effects - muscle

A

stimulates protein synthesis (long term) and inhibits cellular uptake of glucose (short term)

76
Q

pituitary gland
anterior lobe
growth hormone
direct effects - liver

A

stimulates glucose synthesis (short term)

77
Q

pituitary gland
anterior lobe
growth hormone
direct effects - fat

A

increases triglyceride breakdown in adipose tissue (short term)

78
Q

pituitary gland
anterior lobe
growth hormone
indirect effects (2)

A

promotes the growth of bones, muscle and other tissues by causing release of somatomedin C which promotes cell division (long term)
GH has a long term effect on growth and short-term effects on metabolism

HUBS191 P2 (9 decks)

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