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physiology Flashcards

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1
Q

what is the hypothalamus

A

a neuroendocrine hormone as it releases neurone in the brain that travel in the blood to cells

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2
Q

another definition of endocrine gland

A

ductless gland

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3
Q

autocrine secretion

A

cells that secrete chemicals that bind to the same receptors on the cell that secreted it

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4
Q

what are ducted exocrine glands

A

deliver secretions to the external environment such as bile, sweat and saliva

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5
Q

paracrine secretions

A

chemicals diffuse in ECF to affect neighbouring cells and don’t travel in the blood

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5
Q

peptide/protein hormones

A

composed of chains of amino acids ( most common )

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5
Q

amine hormones

A

all derived from one or two hormones (tryptophan or tyrosine)
only melatonin comes from tryptophan)

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6
Q
A
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7
Q

steroid hormones

A

derived from cholestrol

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8
Q

stalk that connects the hypothalamus and pituitary gland

A

infundibulum

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9
Q

describe features of anterior pituitary

A
  1. connected to hypothalamus via capillary portal system
  2. treu endocrine tissue of epithelial origin
  3. makes up 2/3s of the gland
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10
Q

describe features of the posterior pituitary gland

A
  1. continuation of hypothalamus
  2. consists of axons and nerve terminals of hypothalamic neurone
  3. is neuroendocrine
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11
Q

what does non-tropic mean

A

neurohormones produced in the hypothalamus and travel to the posterior pituitary where they are released into the blood

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12
Q

what does tropic mean

A

neurohormones secreted into capillaries travelling to anterior pituitary and govern released of anterior pituitary hormones

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12
Q

name 2 hypothalamic non-tropic hormones

A
  1. vasopressin- ADH
  2. oxytocin- aids expression of milk from lactating breast
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13
Q

describe the hypothalamus-hypophyseal portal system

A

tiny vessels which transfer tropic hormones from hypothalamus to anterior pituitary. very rapid

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14
Q

what does trophic action mean

A

indirect effects in promoting growth

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15
Q

mechanics of action of peptide hormones

A
  1. mRNA binds amino acids onto peptide chain called preprohormone. Goes straight to ER.
  2. Enzyme in the ER chop off the signalling sequence creating an inactive prohormome
  3. Prohormone passes through the Golgi apparatus
  4. secondary vesicles containing prohormones and enzymes bud off the golgi and chop prohormones into active segments/
  5. secretory vesicles release content by exocytosis into extracellular space
  6. hormone moves in circulation for transport to target organ
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16
Q

what receptors do peptide hormones bind too

A

g-protein coupled receptor activate a 2nd messenger system and gives a rapid response

tyrosine kinase linked receptor alters gene expression and gives a slower but longer lasting response

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17
Q

mechanism of action of steroid hormones

A

lipophillicity allows steroid hormones to readily cross the plasma membrane.
2. Activation of intracellular receptors leads to change in gene expression at the level of the nucleus
3. genes control the synthesis of proteins so these hormones increase or decrease protein synthesis

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18
Q

describe half life of steroid hormones

A

hours to days

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19
Q

describe half life of peptide hormones

A

usually minutes therefore requires continued secretion

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20
Q

describe the glucostatic theory

A

food intake is determined by blood glucose
As blood glucose increases the drive to eat decreases

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21
Q

describe the satiety centre

A

promotes feelings of fullness by suppressing feeding centre

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22
describe the lipostatic theory
food intake is determined by fat stores as fat stores increase the drive to eat decreases.
23
what does leptin do and what type of hormone is it
leptin is released by fat stores which depress the feeding centres reducing hunger and is a peptide hormone
24
what are the three categories of energy output
cellular work mechanical work heat loss
25
what is the only voluntary energy output
mechanical work by skeletal muscle
26
when do we enter the absorptive state
after eating when the ingested nutrients supply the body with energy and the excess is stored anabolic phase
27
when do we enter the post-absorptive state
between meals and overnight as nutrients in plasma decrease and we rely on our bodies energy stores. This is a catabolic phase
28
what is the normal BG levels
4.2-6.3mM
29
what is the level of BG for hypoglycaemia
<3mM
30
where are the hormones found in the pancreas
islets of langerhans
31
name the 4 types of langerhans cells
alpha cells- produce glucagon beta cells- produce insulin delta cells produce somatostatin F cells- unknown function
32
simple function of insulin
stimulates glucose uptake by cells
33
how is insulin synthesised
1. As a large preprohormone (preproinsulin) which is converted to proinsulin in the ER 2. Proinsulin is then packaged into vesicles and stored until secreted
34
what form is excess glucose stored in the liver and muscle
As glycogen
35
what form is excess glucose stored in the liver and adipose tissue
as triglycerols
36
describe the primary action of insulin in terms of crossing into cells
1.insulin binds to tyrosine kinase receptors on the cell membrane of insulin dependent tissues to increase glucose uptake 2. Stimulates mobilisation of GLUT 4 and it migrates to the membrane and able to transport glucose into the cell
37
name 2 tissues that are insulin dependent
muscle and fat
38
how do other tissues other than muscle and fat take up glucose
through other GLUT transporters which aren't insulin dependent
39
stimuli which increase insulin release
1. increased BG 2. increased amino acids in plasma 3. glucagon 4. incretin hormones which control GI secretion 5. vagal nerve activity
40
stimuli which inhibit insulin release
1. low BG 2. somatostatin 3. sympathetic alpha 2 effects 4 stress e.g hypoxia
41
why take glucose orally vs IV
orally you have vagal stimulation which stimulates GI hormone release as well as insulin release
42
primary actions of glucagon
1. increase glycogenolysis 2. increase gluconeogenesis 3. formation of ketones from fatty acids All occur in the liver
43
stimuli that promote glucagon release
1.low BG <5mM 2. high amino acids 3. sympathetic innervation and epinephrine 4. cortisol 5. stress
44
stimuli that inhibit glucagon
1. glucose 2 FFAs and ketones 3. insulin 4. somatostatin
45
parasympathetic innervation on islet cells
increase insulin and decrease glucagon
46
sympathetic innervation on islet cells
increased glucagon, increase epinephrine and inhibition of insulin
47
function of pancreatic somatostatin
surpresses release insulin and glucagon
48
what happens if you have a SS secreting tumour
you have diabetes
49
effect of exercise on BG
glucose can be taken up independently of insulin GLUT 4 transporters can migrate to membrane without insulin being present
50
what can hyperglycaemia cause
neuropathy retinopathy nephropathy CVD
51
hormones that contribute to growth
GH IGF-1 thyroid hormone sex steroids glucocorticoids insulin
52
function of growth hormone
promote elongation of bones and increase height, weight and body mass
53
function of sex hormones in growth
close epiphyses and stop boner elongation
54
what happens in congenital hypothyroidism
babies are born of normal size but have retarded growth and development. They retain infantile facial features
55
what is IGF-1
also known as somatomedin C as it mediates the action of GH Has insulin like qualities as it stimulates glucose uptake in muscle and bone secreted primarily by the liver and controls GH through a negative feedback loop
56
things that stimulate GHRH (GH)
increased amino acids in the plasma physical stress and illness delta sleep oestrogen and tesosterone
57
stimuli that increase GHIH (somatostatin secretion)
1. glucose 2. FFAs 3. ageing 4. cortisol
58
hypersecretion of GH
gigantism- excessive growth acromegaly- enlarged hands and feet but long bones don't increase
59
2 active forms of thyroid hormones
T3 and T4
60
2 types of cells present in thyroid gland
1. C cells secrete calcitonin which is a calcium regulating hormone- fewer cells 2. follicular cells which support thyroid hormone synthesis swell as thyroglobulin
61
what is a thyroid follicle
spherical structure whose walls are made of follicular cells and centre filled with colloid= sticky glycoprotein metric and contains 2-3 mths of TH
62
why does T4 have a longer half life than T3
thyroxine binding globulin has a high affinity for T4 releasing it slowly into the plasma
63
how much more T4 do you have than T3 in the plasma
50x more T4
64
key hormones in foetal development
thyroid hormone and insulin
65
thyroid hormone function
Bind to nuclear receptors in target cells were they change transcription and translation to alter protein synthesis
66
symptoms of hyperthyroidism
1. increased metabolic rate and heat production 2. increased protein catabolism- muscle weakness/weight loss 3. altered nervous system function 4. elevated cardiovascular function- increased HR
67
causes of hypothyroidism
Hashimoto disease- autoimmune attack on thyroid gland and can't produce hormone deficiency of dietary iodine
68
symptoms of hypothyroidism
weight gain and cold intolerant brittle nails and thin skin slow speech/ reflexes and fatigue slow HR and weaker pulse
69
what does goitre mean
enlargement of thyroid gland
70
cause of hyperthyroidism
graves disease- antibodies produces that mimic TSH and continually activate thyroid gland
71
function of adrenal medulla (central part and neural in origin)
modified sympathetic ganglion secretes catecholamines from the postganglionic cell
72
function of adrenal cortex
secretes 3 steroid hormones 1. mineralocorticoids 2. glucocorticoids 3. sex steroids
73
3 zones in the cortex
zona glomerulosa- aldosterone zona fasciculata- glucocorticoids zona reticularis- sex hormones
74
actions of cortisol on glucose metabolism
1. gluconeogenesis 2. proteolysis 3. lipolysis 4. decrease insulin sensitivity
75

endocrine (3 decks)

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