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Human Physiology > the endocrine system > Flashcards

the endocrine system Flashcards

1
Q

what is homeostasis?

what is a central aspect of maintaining homeostasis and which system conducts this?

A

maintenance of relatively constant chemical/physical conditions of the internal enviro despite changes to the external enviro e.g body temp

goal of every organ

communication is a central aspect and is conducted by the endocrine system

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2
Q

what is the ‘normal physiological range’?

A

homeostasis being able to vary within narrow limits

feedback loops maintain this

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3
Q

what is successful compensation and failure to compensate related to homeostasis?

A

success: homeostasis re-established
failure: results in illness e.g diabetes/death when homeostasis fails

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4
Q

what is the endocrine system?

A

collection of glands which secrete hormones into circulation to be carried to distant organs

essential to the communication part of homeostasis

long-term, ongoing metabolic process throughout the body via hormones

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5
Q

what manufactures specific hormones and how are they released?

A

specialised epithelial secretory cells in endocrine glands

released systematically into capillaries from epithelial cells

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6
Q

what are the 4 ways hormones can communicate and describe these?

A

endocrine - transported in blood to distant site of action

autocrine - hormone acts directly back on cell that has produced it

paracrine - hormone acts directly upon nearby cell

juxtacrine - hormonal intracellular communication between connecting cells so requires physical contact of 2 cells

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7
Q

how are endocrine glands stimulated to release hormones?

A

humoral stimuli - changes in composition of blood

hormonal stimuli - removal or arrival of a specific hormone

neural stimuli - nerve fibres stimulate hormone release

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8
Q

which cells do hormones effect and why?

A

target cells - responds to hormones as bears receptors for the hormones

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9
Q

what does the magnitude of hormone effect depend on?

4 things

A
  1. number of target receptors (continuously synthesised and degraded so number can vary over short periods)
  2. concentration of hormone
  3. affinity of receptor for hormone (sensitivity)
  4. influence of other hormones
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10
Q

what is up-regulation and down-regulation related to target cells?

A

up: increase in number of receptors on target cell
down: decrease in number of receptors on target cell

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11
Q

How are steroid hormones transported in the blood and how do they enter and how are they used by cells?

A

steroid -
* lipid-soluble

transported:
circulate in blood bound to albumin carrier protein

enters and used by:

  1. diffuse into cell which has specific receptor in either cytoplasm or nucleus
  2. hormone-receptor complex activate gene expression
  3. protein synthesis is induced
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12
Q

what is signal transduction?

and an example?

A

extracellular signals are communicated into a cell to affect function
e.g non-steroid hormone binding to receptor on plasma cell membrane

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13
Q

what is the role of the endocrine system in a feedback loop?

A
  1. stimulus activates endocrine gland
  2. endocrine gland secretes hormone into bloodstream
  3. target cells respond to hormone to alter (increase/decrease) original stimulus
  4. signal reaches original endocrine gland to switch-off further hormone production
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14
Q

what is a negative feedback loop?

and an example?

A

decreases function and lessens output of system

e.g body temperature

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15
Q

what is a posiitve feedback loop?

A

rare

rate of a process increases as the concentration of the product increase

stimulus produces a response that reinforces the original stimulus

e.g labour contractions

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16
Q

what are the 2 lobes of the pituitary gland?

what are the under they control of?

A
  1. anterior lobe - receives hypothalamic hormones which stimulates synthesis of hormones e.g GH growth hormone
  2. posterior lobe - stores 2 hypothalamic hormones and releases into circulation (doesn’t synthesise them) e.g ADH and oxytocin

under direct control of hypothalamic hormones

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17
Q

describe the main hormonal function of the pineal gland?

A

produces melatonin which is suppressed by light and stimulated by darkness
modulates sleep patterns in circadian rhythms

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18
Q

describe the thyroid gland?

where?
what does it produce?
what is its role?
what is it stimulated by?

A

located in neck

produces thyroxine and triiodothyronine

tissue development and growth
macronutrient metabolism

hormone production stimulated by thyroid-stimulating hormone (anterior pituitary)

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19
Q

describe the parathyroid gland?

A

responsible in producing PTH (parathyroid hormone)

which regulates serum calcium levels by stimulating reabsorption so increase PTH = increase serum calcium levels

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20
Q

describe the pancreas?

dual functions?

A

exocrine - secretes enzymes to digest substances e.g CHO

endocrine - secrete insulin and glucagon which regulate blood glucose levels

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21
Q

what do alpha and beta cells in the endocrine part of the pancreas do?

A

alpha - secrete glucagon which increases blood glucose levels by converting glycogen into glucose

beta - secretes insulin which decreases blood glucose levels by promoting uptake of glucose in tissues to be stored as glycogen

22
Q

describe the adrenal glands?

A

pair of glands

each one consists of:

outer adrenal cortex - produces steroid hormones

inner adrenal medulla - secretes catecholamines which help in fight or flight response

23
Q

3 main faults of endocrine system leading to dysfuction?

A

1) abnormal hormone receptor function/levels: affects non-steroid hormones e.g insulin
2) altered intracellular responses to hormone-receptor complex causing impaired cellular hormone response
3) hyper or hypo-secretion of hormones by a gland

24
Q

overview of fight or flight response?

what stimulates the start of sympathetic response

receptors

A

sympathtic nerve fibres reach adrenal medulla

stimulates release of catecholamines: neurotransmitters epinephrine (75-80% of output) and norepinephrine

effect alpha receptors (found on sympathic organs stimulated by nor)

and

beta receptors (located on membranes of many organs)

alpha receptors mainly stimulated by norepinephrine

epinephrine stimulates both alpha and beta receptors so has global response

stress response caused

25
Q

one of the ways which hormones work during exercise?

A

work to ensure glucose and free fatty acids (fuel sources) are available for muscle energy metabolism

26
Q

relationship between exercise intensity and contribution of different fuel source?

A

amount of free fatty acids contributing to fuel sources decreases as exercise intensity increases

amount of muscle glycogen breakdown contributing to fuel sources increases as exercise intensity increases

27
Q

which 4 hormones work to increase levels of circulating glucose in plasma?

A
  1. glucagon
    - at rest facilitates glycogenolysis and gluconeogenesis
    - secretion increases during exercise

2 & 3. ephinephrine and norepinephrine increase during exercise to increase glycogenolysis (glycogen to glucose)

  1. cortsol
28
Q

relationship between plasma insulin levels and prolonged exercise?
why?

A

plasma insulin levels decline during prolonged submaximal exercise

due to receptors being more sensitive to insulin so concentration of hormone doesn’t need to be high

29
Q

what are the effects of epinephrine and norepinephrine on insulin and glucagon secretion due to the receptors they bind to?

A

their effect on alpha cells - increases glucagon so increase in blood glucagon which promotes glycogen breakdown to glucose

their effect on beta cells - decrease levels of insulin so levels of plasma insulin decrease which prevents the uptake of glucose by tissues to be storedas glycogen

30
Q

what effect does epinephrine and norepinephrine have on plasma free fatty acids?

and how?

A

stimulates breakdown of triaglycerides to free fatty acids

so increases free fatty acid concentration

stimulates HSL which promotes conversion of triaglyceride to fatty acids and glycerol

31
Q

differences between the nervous system and endocrine system?

A

nervous system:
short-term very specific responses to enviro stimuli
via chemical messengers (neurotransmitters)

endocrine system: long-term, ongoing metabolic processes throughout the body
via chemical messengers (homrones)

32
Q

differences between the nervous system and endocrine system?

A

nervous system:
short-term very specific responses to enviro stimuli
via chemical messengers (neurotransmitters)

endocrine system: long-term, ongoing metabolic processes throughout the body
via chemical messengers (homrones)

33
Q

how do hormones ultimately regulate cell function etc.?

A

through their effects on enzymes which control all cellular activity

34
Q

how do non-steroid hormones convey messages?

example of such hormone?

A
  • water-soluble
  • peptide
  1. can’t diffuse across cell membrane as have high molecular weight
  2. bind with receptor on plasma membrane of cell (first message)
  3. signal transduction into cell by activation of transducer leading to enzyme activation in cell (second messenger)
35
Q

what is the Islets of Langerhans?

A

endocrine part of pancreas (regulating blood glucose levels)

contains 4 types of cells: alpha, beta, delta, F

36
Q

what are several roles of insulin?

A

stimulates glucose uptake into tissues to be stored as glycogen to reduce amount of glucose circulating in blood

stimulates glycogen synthesis

inhibits protein breakdown in muscle

37
Q

what happens when there’s a decline in blood glucose level?

A

detected by glucagon-releasing cells of pancreas

stimulated to release glucagon into the blood

liver breaks down glycogen stores and releses glucose into blood

blood glucose levels rise

stimulus for glucose release diminishes and body returns to homeostasis

38
Q

what happens when there’s an increase in blood glucose level?

A

detected by insulin-secreting cells of pancreas

stimulated to release insulin into lood

body cells take up more glucose and liver takes up glucose and stores it as glycogen

blood glucose level declines

stimulus for insulin release diminishes and body returns to homeostasis

39
Q

what is the role of GLUT4 translocation?

what is it stimulated by?

A

insulin and exercise can stimulate GLUT4 recruitment to the cell surface

in order to aid movement of glucose into the cell

40
Q

example of insulin and glucagon as antagonistic?

A

glycogenesis requires high levels of insulin and low levels of glucagon

whereas glycogenolysis requires high levels of glucagon and low levels of insulin

41
Q

what causes type 1 diabetes?

A

body’s failure to produce enough insulin so hyperglycemia occurs asglucose not bein stored (high levels of glucose in blood)

onset in childhood

42
Q

what causes type 2 diabetes?

A

insulin resistance leading to lack of glucose storage in cells as GLUT4 not translocated to cell surface

due to decreased no. of insulin receptors or abnormal post-receptor signlling events within target cell

onset in adulthood

43
Q

what can type 1 diabtes lead to?

A

glucose appearing in urine as glucose threshold exceeded

weight loss:
loss of CHO as fuel source so fat used for energy
protein breakdown occuring

hypoglycemia (glucose deficiency)

44
Q

describe ketoacidosis in type 1 diabetes?

A

ketones formed by lack of CHO so fat used as energy source and lipolysis

worsens dehydration as body tries to remove ketones through urine
ph falls

45
Q

what are the 3 vascular complications of type 2 diabetes and another effect?

A

microvascular disease - blindness and kineys

macrovascular disease - coronary artery disease

peripheral vascular diseas - foot lesions

nerve damage

46
Q

what happens to blood glucose levels after exercise compared to rest?

A

blood glucose levels decrease after a period of exercise due glucose being taken up by the muscles from the blood and used as energy

47
Q

what is an OGTT and what are the expected results?

A

an oral glucose tolerance test
blood samples taken in exercising and resting ppts and after glucose taken in and glucose content analysed in YSI analyser

glucose levels drop after exercise and increase when glucose taken in

exercise - levels return to baseline (4) quicker as exercise makes body more insulin responsive

rest - levels return to baseline slower as no stimulus to cause quick decrease

48
Q

what may effect blood glucose levels recorded in OGTT?

A

food eaten and exercise untaken during day

blood tube not filled with blood so air bubbles

49
Q

what is the effect of HIIT training on insulin receptors and glucose levels?

A

improves ability of insulin receptors to stimulate glucose uptake via GLUT4 transporter protein so less insulin required in blood (insulin sensitivity) so brings down plasma glucose levels quickly afterwards

reduces total amount of blood glucose and insulin in general so reduces risk of certain diseases

50
Q

what is the effect of endurance training on insulin sensitivity?

A

improves insulin sensitivity meaning insulin receptors better at stimulating glucose uptake from blood so less insulin needed

Human Physiology (9 decks)

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