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endocrine > Physiology > Flashcards

Physiology Flashcards

1
Q

describe the structure of insulin

A

two polypeptide chains, an A chain and a B chain, covalently linked by two inter-chain disulphide bridges. There is a third, intra-chain disulphide bridge.

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2
Q

where is insulin synthesised

A

beta cells in the islets of Langerhans

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3
Q

what can be used as a measure of endogenous insulin production

A

C peptide

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4
Q

key points of the production of mature insulin (4)

A

prepoinsulin is synthesised in the RER of pancreatic b cells
removal of signalling peptide during insertion into the endoplasmic reticulum generates proinsulin
proinsulin = A chain + B chain + connecting peptide in the middle (C peptide)
endopeptidases excise the C peptide generating mature insulin

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5
Q

how can synthetic insulin preparations be created

A

by changing the amino acid sequence of endogenous insulin

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6
Q

secretion of insulin (5)

A

glucose enters b cells through the GLUT2 glucose transporter and is phosphorylated by glucokinase
increased metabolism of glucose leads to increase in ATP
ATP inhibits the ATP-sensitive K+ channel
depolarisation of the membrane causes opening of voltage gated Ca2+ channels
fusion of secretory vessels containing insulin with the cell membrane

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7
Q

what are the 2 types of insulin release

A

basal insulin release
post-prandial insulin release

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8
Q

describe post prandial insulin secretion

A

biphasic pattern

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9
Q

why is post-prandial insulin release biphasic

A

5% is immediately available for release to prevent a sharp increase in glucose
reserve pool requires preparation and mobilisation before its available for release

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10
Q

what does insulin release cause to decrease (2)

A

lipolysis
gluconeogenesis in the liver

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11
Q

what does insulin release cause to increase (7)

A
  • Amino acid uptake in muscle
  • DNA synthesis
  • Protein synthesis
  • Growth responses
  • Glucose uptake in muscle and adipose tissue
  • Lipogenesis in adipose tissue and liver
  • Glycogen synthesis in liver and muscle
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12
Q

where in the islets are b cells found

A

close to blood vessels to allow easy identification of blood glucose conc

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13
Q

name the 5 types of cells found in the islets of langerhans

A
  • α-cells secrete glucagon
  • β-cells secrete insulin
  • δ-cells secrete somatostatin
  • PP-cells secrete pancreatic polypeptide(PP)
  • ε-cells secrete Ghrelin
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14
Q

how does T2DM affect beta cells

A

number of secretory granules per β-cell is reduced

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15
Q

what happens to alpha cells at low glucose (4)

A
  1. KATP channels open
  2. Voltage-gated sodium channels (NaV) contributes to action potentials
  3. P/Q type voltage gated calcium channels (CaV) enable calcium influx
  4. Glucagon exocytosis triggered
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16
Q

role of glucagon

A

acts on the liver to promote hepatic glucose
production, raising blood glucose

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17
Q

what is the incretin effect

A

greater increase in insulin production in response to oral glucose than in response to IV glucose

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18
Q

who has an impaired incretin effect

A

patients with T2DM

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19
Q

what are incretins

A

intestinal secretion of insulin

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20
Q

name the 2 key incretin hormones

A

GIP, GLP1

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21
Q

where is GIP secreted from

A

K cells in the intestinal epithelial layer

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22
Q

where is GLP1 secreted from

A

L cells after eating

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23
Q

role of GLP1 (3)

A

increases glucose-induced insulin release by β-cells
promotes beta cell proliferation
suppress glucagon secretion at depolarising glucose concentrations

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24
Q

response of pituitary gland to increased plasma osmolarity

A

increased ADH

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25
Q

consequence of increased ADH (3)

A

more aquaporins in DCT and CD cells of the kidney → more water reabsorbed in kidney → small volume of concentrated urine

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26
Q

response of pituitary gland to decreased plasma osmolarity

A

decreased ADH

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27
Q

consequences of decreased ADH (3)

A

less aquaporins in DCT and CD cells of the kidney → less water reabsorbed in kidney → large volume of dilute urine

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28
Q

what does concentrated urine mean for osmolarity

A

high osmolarity

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29
Q

what does diluted urine mean for osmolarity

A

low osmolarity

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30
Q

how does mineralocorticoid activity affect Na+ balance

A

too much means sodium gain
too little means sodium loss

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31
Q

where is sodium confined to (body compartments)

A

extracellular fluid

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32
Q

state some clinical signs of hyponatraemia

A
  • Increased pulse
  • Dry mucous membranes
  • Soft/sunken eyeballs
  • Decreased skin turger
  • Decreased consciousness
  • Decreased urine output
  • Postural decrease in blood pressure
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33
Q

state some clinical signs of hypernatremia

A
  • Coughing, shortness of breath
  • Tiredness
  • Pulmonary oedema
  • Pleural effusion
  • Ascites
  • Swelling in ankles and legs
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34
Q

what can cause hyponatraemia

A

too little sodium or too much water

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35
Q

what can cause hypernatremia

A

too much sodium or too little water

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36
Q

what is the most common cause of low Na+

A

SIADH

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37
Q

what is the most common cause of high Na+

A

low water intake

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38
Q

management of low Na+ (2)

A
  • If due to too little sodium - give sodium IV as saline or orally
  • If due to too much water - remove water through fluid restriction
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39
Q

management of high Na+

A
  • If due to too little water - give water as IV dextrose
  • If due to too much sodium - remove sodium through diuretics
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40
Q

what does SIADH stand for

A

Syndrome of Inappropriate Antidiuretic Hormone Secretion

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41
Q

what happens in SIADH

A

excessive release of ADH causing an abnormal and excessive retention of water

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42
Q

describe the hypothalamic-pituitary-thyroid axis (5)

A
  • hypothalamus produces TRH
  • stimulates anterior pituitary to produce TSH
  • binds to receptor on thyroid epithelial cells
  • production of cAMP increases production and release of T3 and T4
  • circulate in bound and free forms and suppress the production of TRH and TSH
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43
Q

state the 2 gonadotrophic hormones secreted by the pituitary

A

follicle stimulating hormone
luteinizing hormone

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44
Q

role of FSH in men

A

causes the testes to produce sperm

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45
Q

role of FSH in women

A

causes the growth of ovarian follicles and causes the ovary to secrete oestrogen which thickens the endometrium

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46
Q

role of LH in men

A

causes the testes to secrete testosterone

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47
Q

role of LH in women

A

causes ovulation and causes progesterone production by the corpus leutum

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48
Q

what is GnRH

A

gonadotrophin releasing hormone

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49
Q

describe the release of GnRH

A

pulsatile manner

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50
Q

where is GnRH synthesised and released from

A

hypothalamus

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51
Q

role of GnRH

A

causes the release of FSH and LH from the anterior pituitary

52
Q

what is GnRH pulsatility regulated by

A

oestrogen and progesterone/testosterone

53
Q

effect of progesterone on GnRH

A

increase in progesterone reduces the frequency of GnRH pulses

54
Q

effect of oestrogen on GnRH

A

increase in oestrogen will increase pulsatility of GnRH driving the release of LH

55
Q

what are the 3 key events in the menstrual cycle

A

follicular growth
ovulation
luteal phase

56
Q

frequency of GnRH pulses throughout the menstrual cycle

A

more frequent during early follicular phase and less during the luteal phase

57
Q

what does a follicle consist of

A

an oocyte surrounded by follicular cells

58
Q

what causes endometrium to thicken

A

oestrogen

59
Q

what causes endometrium to become a secretory tissue

A

progesterone

60
Q

what does early stage follicular growth depend on

A

NOTHING

61
Q

when does the LH surge happen

A

34-36 hours before ovulation

62
Q

what influences the formation of the corpus leutum

A

LH

63
Q

what happens during the formation of the corpus luteum (2)

A

increase in progesterone production
granulosa and theca cells transform to luteal cells

64
Q

name some functions of oestrogen

A

regulates LH surge
reduces vaginal pH
decreases viscosity of cervical mucous to facilitate sperm penetration

65
Q

what secretes oestrogen

A

ovaries and adrenal cortex
and placenta during pregnancy

66
Q

what secretes progesterone

A

corpus luteum
placenta during pregnancy

67
Q

what is the main function of progesterone

A

maintains pregnancy - inhibits the secretion of LH

68
Q

how is progesterone pro-gestation

A

maintains thickness of the endometrium
relaxes the myometrium
increases basal body temperature

69
Q

name 3 ways we can predict ovulation

A

spinnbarkeit
ovulation kits
basal body temperature

70
Q

what is spinnbarkeit

A

describes the property of cervical mucous which changes in response to oestrogen levels around the time of ovulation

71
Q

how do ovulation kits work

A

use the LH surge to predict the onset of ovulation

72
Q

when should basal body temperature be measured

A

in the morning before moving about or eating after at least 6 hours of sleep

73
Q

what regulates sperms ability to penetrate cervical mucous (4)

A

thickness of the mucous
motility of the sperm
interaction with ROS
interaction with mucins

74
Q

histology of the stroma of the cervix

A

fibroblast cells surrounded by a collagen matrix

75
Q

histology of epithelium of the cervix

A

columnar epithelial cells, site of mucus production

76
Q

role of the stroma of the cervix

A

regulates the rigidity of the cervical wall

77
Q

role of the epithelium of the cervix

A

site of mucous production

78
Q

what is released once an embryo implants

A

HCG

79
Q

what produces testosterone

A

leydig cells of the testis

80
Q

where are sertoli cells found

A

seminiferous tubes

81
Q

what is produced by sertoli cells

A

mature sperm
inhibin

82
Q

where does spermatogenesis occur

A

in the testes

83
Q

how long does the entire spermatogenic process take

A

70 days

84
Q

what happens to testosterone when it reaches target tissues

A

converted to dihydrotestosterone and oestradiol

85
Q

hypothalamic-pituitary -thyroid axis

A

hypothalamus produces TRH
stimulates anterior pituitary to produce TSC
thyroid gland produces and release T3 and T4
T3 and T4 supress the production of TRH and TSH

86
Q

what cells does the thyroid gland consist of

A

follicles lined by cuboidal epithelial cells

87
Q

which is the biologically active thyroid hormone

A

T3

88
Q

what is the most common (in terms of amount) thyroid hormone

A

T4

89
Q

role of T4

A

prohormone
converted to T3 by the liver and kidney to become biologically active

90
Q

what is the most common hormone binding protein for T3 and T4

A

thyroxine binding globulin

91
Q

which versions of T3 and T4 can enter cells

A

ONLY unbound hormones

92
Q

name some states that can cause an increase in TBG

A

pregnancy, OCP, chronic active hepatitis and biliary cirrhosis

93
Q

name some states that can cause a decrease in TBG

A

cushings, severe systemic illness, chronic liver disease

94
Q

consequence of alterations in TBG levels

A

confusing total T4 levels - most levels measure free T4

95
Q

effect of thyroid hormones on all cells

A

increase metabolic rate
increase glucose uptake

96
Q

effect of thyroid hormone on liver tissue

A

increased glycogenolysis and gluconeogenesis
decreased gylcogenesis

97
Q

effect of thyroid hormone on adipose tissue

A

increased lipolysis
decreased lipogenesis

98
Q

effect of thyroid hormone on the lungs

A

increased breathing rate

99
Q

effect of thyroid hormone on the heart

A

increased HR and force of contraction

100
Q

how do thyroid hormones increase basal metabolic rate (3)

A
  • Increase number and size of mitochondria
  • Increase oxygen use and rates of ATP hydrolysis
  • Increase synthesis of respiratory chain enzymes
101
Q

key enzyme in the degradation of thyroid hormones

A

de-iodinases

102
Q

where are type 1 de-iodinases found

A

liver and kidney

103
Q

where are type 2 de-iodinases found

A

heart, skeletal muscle, fat, thyroid, and pituitary

104
Q

where are type 3 de-iodinases found

A

foetal tissue, placenta, and brain (except pituitary)

105
Q

role of type 3 de-iodinases

A

breaks down the majority of T3 into inactive T2 and T4 into inactive reverse T3

106
Q

role of TRH

A

stimulates the anterior pituitary to release TSH and prolactin

107
Q

role of CRH

A

stimulates the anterior pituitary to release ACTH

108
Q

what is autocrine signalling

A

cell signals to itself

109
Q

what is paracrine signalling

A

cell signals to its close neighbours

110
Q

what is endocrine signalling

A

cell signals via molecules transported by the blood to target distant cells

111
Q

give some examples of peptide hormones

A

oxytocin, ADH, GH, insulin

112
Q

thyroxine binding globulin

A

binds thyroxine selectively and also some T3

113
Q

another name for T4

A

thyroxine

114
Q

another name for T3

A

triodothyronine

115
Q

role of albumin

A

binds many steroids and thyroxine

116
Q

role of transthyretin

A

binds thyroxine and some steroids

117
Q

what controls the release of prolactin

A

tonic inhibition by hypothalamic dopamine

118
Q

what inhibits prolactin secretion in non-pregnant women

A

prolactin inhibiting hormone (dopamine)

119
Q

what regulates cortisol production

A

HPA axis

120
Q

HPA axis

A

hypothalamus release corticotropin releasing hormone
anterior pituitary releases adrenocorticotropic hormone
adrenal cortex releases cortisol

121
Q

what regulates aldosterone

A

RAAS

122
Q

what activates RAAS

A

decreased blood pressure

123
Q

RAAS run through

A

renin released from the kidneys
causes angiotensinogen from the liver to be converted to angiotensin 1
ACE from the lungs converts angiotensin 1 -> 2
angiotensin 2 acts on the adrenal gland to stimulate aldosterone

124
Q

consequence of the release of aldosterone

A

acts on the kidneys to stimulate the reabsorption of salt and water

125
Q

what is another role of angiotensin 2

A

acts directly on blood vessels to stimulate vasoconstriction

endocrine (15 decks)

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