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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
consequence of increased ADH (3)
more aquaporins in DCT and CD cells of the kidney → more water reabsorbed in kidney → small volume of concentrated urine
26
response of pituitary gland to decreased plasma osmolarity
decreased ADH
27
consequences of decreased ADH (3)
less aquaporins in DCT and CD cells of the kidney → less water reabsorbed in kidney → large volume of dilute urine
28
what does concentrated urine mean for osmolarity
high osmolarity
29
what does diluted urine mean for osmolarity
low osmolarity
30
how does mineralocorticoid activity affect Na+ balance
too much means sodium gain too little means sodium loss
31
where is sodium confined to (body compartments)
extracellular fluid
32
state some clinical signs of hyponatraemia
- Increased pulse - Dry mucous membranes - Soft/sunken eyeballs - Decreased skin turger - Decreased consciousness - Decreased urine output - Postural decrease in blood pressure
33
state some clinical signs of hypernatremia
- Coughing, shortness of breath - Tiredness - Pulmonary oedema - Pleural effusion - Ascites - Swelling in ankles and legs
34
what can cause hyponatraemia
too little sodium or too much water
35
what can cause hypernatremia
too much sodium or too little water
36
what is the most common cause of low Na+
SIADH
37
what is the most common cause of high Na+
low water intake
38
management of low Na+ (2)
- If due to too little sodium - give sodium IV as saline or orally - If due to too much water - remove water through fluid restriction
39
management of high Na+
- If due to too little water - give water as IV dextrose - If due to too much sodium - remove sodium through diuretics
40
what does SIADH stand for
Syndrome of Inappropriate Antidiuretic Hormone Secretion
41
what happens in SIADH
excessive release of ADH causing an abnormal and excessive retention of water
42
describe the hypothalamic-pituitary-thyroid axis (5)
- 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
43
state the 2 gonadotrophic hormones secreted by the pituitary
follicle stimulating hormone luteinizing hormone
44
role of FSH in men
causes the testes to produce sperm
45
role of FSH in women
causes the growth of ovarian follicles and causes the ovary to secrete oestrogen which thickens the endometrium
46
role of LH in men
causes the testes to secrete testosterone
47
role of LH in women
causes ovulation and causes progesterone production by the corpus leutum
48
what is GnRH
gonadotrophin releasing hormone
49
describe the release of GnRH
pulsatile manner
50
where is GnRH synthesised and released from
hypothalamus
51
role of GnRH
causes the release of FSH and LH from the anterior pituitary
52
what is GnRH pulsatility regulated by
oestrogen and progesterone/testosterone
53
effect of progesterone on GnRH
increase in progesterone reduces the frequency of GnRH pulses
54
effect of oestrogen on GnRH
increase in oestrogen will increase pulsatility of GnRH driving the release of LH
55
what are the 3 key events in the menstrual cycle
follicular growth ovulation luteal phase
56
frequency of GnRH pulses throughout the menstrual cycle
more frequent during early follicular phase and less during the luteal phase
57
what does a follicle consist of
an oocyte surrounded by follicular cells
58
what causes endometrium to thicken
oestrogen
59
what causes endometrium to become a secretory tissue
progesterone
60
what does early stage follicular growth depend on
NOTHING
61
when does the LH surge happen
34-36 hours before ovulation
62
what influences the formation of the corpus leutum
LH
63
what happens during the formation of the corpus luteum (2)
increase in progesterone production granulosa and theca cells transform to luteal cells
64
name some functions of oestrogen
regulates LH surge reduces vaginal pH decreases viscosity of cervical mucous to facilitate sperm penetration
65
what secretes oestrogen
ovaries and adrenal cortex and placenta during pregnancy
66
what secretes progesterone
corpus luteum placenta during pregnancy
67
what is the main function of progesterone
maintains pregnancy - inhibits the secretion of LH
68
how is progesterone pro-gestation
maintains thickness of the endometrium relaxes the myometrium increases basal body temperature
69
name 3 ways we can predict ovulation
spinnbarkeit ovulation kits basal body temperature
70
what is spinnbarkeit
describes the property of cervical mucous which changes in response to oestrogen levels around the time of ovulation
71
how do ovulation kits work
use the LH surge to predict the onset of ovulation
72
when should basal body temperature be measured
in the morning before moving about or eating after at least 6 hours of sleep
73
what regulates sperms ability to penetrate cervical mucous (4)
thickness of the mucous motility of the sperm interaction with ROS interaction with mucins
74
histology of the stroma of the cervix
fibroblast cells surrounded by a collagen matrix
75
histology of epithelium of the cervix
columnar epithelial cells, site of mucus production
76
role of the stroma of the cervix
regulates the rigidity of the cervical wall
77
role of the epithelium of the cervix
site of mucous production
78
what is released once an embryo implants
HCG
79
what produces testosterone
leydig cells of the testis
80
where are sertoli cells found
seminiferous tubes
81
what is produced by sertoli cells
mature sperm inhibin
82
where does spermatogenesis occur
in the testes
83
how long does the entire spermatogenic process take
70 days
84
what happens to testosterone when it reaches target tissues
converted to dihydrotestosterone and oestradiol
85
hypothalamic-pituitary -thyroid axis
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
what cells does the thyroid gland consist of
follicles lined by cuboidal epithelial cells
87
which is the biologically active thyroid hormone
T3
88
what is the most common (in terms of amount) thyroid hormone
T4
89
role of T4
prohormone converted to T3 by the liver and kidney to become biologically active
90
what is the most common hormone binding protein for T3 and T4
thyroxine binding globulin
91
which versions of T3 and T4 can enter cells
ONLY unbound hormones
92
name some states that can cause an increase in TBG
pregnancy, OCP, chronic active hepatitis and biliary cirrhosis
93
name some states that can cause a decrease in TBG
cushings, severe systemic illness, chronic liver disease
94
consequence of alterations in TBG levels
confusing total T4 levels - most levels measure free T4
95
effect of thyroid hormones on all cells
increase metabolic rate increase glucose uptake
96
effect of thyroid hormone on liver tissue
increased glycogenolysis and gluconeogenesis decreased gylcogenesis
97
effect of thyroid hormone on adipose tissue
increased lipolysis decreased lipogenesis
98
effect of thyroid hormone on the lungs
increased breathing rate
99
effect of thyroid hormone on the heart
increased HR and force of contraction
100
how do thyroid hormones increase basal metabolic rate (3)
- Increase number and size of mitochondria - Increase oxygen use and rates of ATP hydrolysis - Increase synthesis of respiratory chain enzymes
101
key enzyme in the degradation of thyroid hormones
de-iodinases
102
where are type 1 de-iodinases found
liver and kidney
103
where are type 2 de-iodinases found
heart, skeletal muscle, fat, thyroid, and pituitary
104
where are type 3 de-iodinases found
foetal tissue, placenta, and brain (except pituitary)
105
role of type 3 de-iodinases
breaks down the majority of T3 into inactive T2 and T4 into inactive reverse T3
106
role of TRH
stimulates the anterior pituitary to release TSH and prolactin
107
role of CRH
stimulates the anterior pituitary to release ACTH
108
what is autocrine signalling
cell signals to itself
109
what is paracrine signalling
cell signals to its close neighbours
110
what is endocrine signalling
cell signals via molecules transported by the blood to target distant cells
111
give some examples of peptide hormones
oxytocin, ADH, GH, insulin
112
thyroxine binding globulin
binds thyroxine selectively and also some T3
113
another name for T4
thyroxine
114
another name for T3
triodothyronine
115
role of albumin
binds many steroids and thyroxine
116
role of transthyretin
binds thyroxine and some steroids
117
what controls the release of prolactin
tonic inhibition by hypothalamic dopamine
118
what inhibits prolactin secretion in non-pregnant women
prolactin inhibiting hormone (dopamine)
119
what regulates cortisol production
HPA axis
120
HPA axis
hypothalamus release corticotropin releasing hormone anterior pituitary releases adrenocorticotropic hormone adrenal cortex releases cortisol
121
what regulates aldosterone
RAAS
122
what activates RAAS
decreased blood pressure
123
RAAS run through
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
consequence of the release of aldosterone
acts on the kidneys to stimulate the reabsorption of salt and water
125
what is another role of angiotensin 2
acts directly on blood vessels to stimulate vasoconstriction

endocrine (15 decks)

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