Endocrinology Flashcards
1
Q
What are characteristics of water-soluble hormones?
A
Travel loose in plasma, bind to plasma membrane-based recepticles, vesicles > exocytosis
2
Q
What kind of protein is hCG?
A
Glycoprotein
3
Q
What are characteristics of lipid-soluble hormones?
A
Diffuse out of cells, travel bound to carrier proteins, bind to receptors inside the cell
4
Q
Why are prostaglandins paracrine?
A
Broken down rapidly
5
Q
What makes up the blood-brain barrier?
A
Capillaries connected by extra-tight junctions, basement membrane and glial feet
6
Q
Which molecules can pass the BBB?
A
Lipid-soluble
7
Q
Which regions have a permeable BBB?
A
Posterior pituitary, median eminence, pineal gland, OVLT, subfornical organ, area postrema
8
Q
Which are the circumventricular organs?
A
OVLT, subfornical organ, area postrema
9
Q
Where is hCG released?
A
Chorion (placenta)
10
Q
Why do some hormones show pulsality?
A
Receptor would be down-regulated if constant growth
11
Q
What is a Zeitgeber?
A
Tunes the circadian clock
12
Q
What produces melatonin?
A
Pineal gland
13
Q
What does blue light do?
A
Blue light > Intrinsically photosensitive retinal ganglion cells containing melanopsin (ipRGC) > retinal hypothalamic tract > SCN
14
Q
What does SCN inhibit during light?
A
Paraventricular nucleus
15
Q
What does the paraventricular nucleus do?
A
Causes sympathetic nerves to cause pineal gland to produce melatonin
16
Q
What controls circadian rhythms?
A
Suprachiasmatic nucleus
17
Q
How do you get act pots during the day and not at night?
A
Proteins induce membrane ion channels so depolarised during the day (so act pots) and hyperpolarised at night so no act pots here
18
Q
Where are vomeronasal organs?
A
In nasal cavity between mouth and nose
19
Q
Where does the hypothalamic hypophyseal tract go?
A
From the paraventricular and supraoptic nucleus to the posterior pituitary
20
Q
What is the neurohypophysis?
A
Posterior
21
Q
What is the adenohypophysis?
A
Anterior
22
Q
What does the posterior pituitary produce?
A
ADH and oxytocin
23
Q
Why does the anterior pituitary lie outside the BBB?
A
Originates from Rathke’s pouch which pinches off mouth roof in embryo
24
Q
What can white fat do?
A
White fat > leptin > arcuate nucleus > suppresses feeding behaviour, increases metabolic rate, increases reproductive function
25
How does leptin increase metabolic rate?
PVN > TRH > pituitary/thyroid > thyroid hormone
26
Why isn't anterior pituitary a neural tissue?
Pulsatility is preserved
27
What are secretory cells of the anterior pituitary called?
Trophs
28
What is long loop feedback?
Hormone produced elsewhere negatively feeds back on hypothalamus
29
What is short loop feedback?
Pituitary hormone feeds back on hypothalamus
30
What is ultra short loop feedback?
Hypothalamic hormone inhibits its own production
31
Why does thyroid colloid contain?
Thyroglobulin
32
What families does the anterior pituitary produce?
Somatomammotropins, pro-opiomelanocorticoids, glycoproteins
33
What are the Somatomammotropins?
Growth hormone, prolactin
34
What are the pro-opiomelanocorticoids?
Melanocyte-stimulating hormone, adrenocorticotropic hormone
35
What are the glycoproteins?
GOnadotropind LH and FSH, thyroid stimulating hormone
36
What is the process of T3 production?
PVN > TRH > thyrotrophs in anterior pituitary > TSH > thyroid gland > T4 > T3
37
Which enzyme converts T4 > T3?
Deiodinase
38
Which transporter gets I- into the cells? Which into the follicular lumen?
NIS then pendrin
39
Why doesn't T4 show circadian rhythm?
Half life is long anyway
40
Which enzyme produces iodinated thyroglobulin?
Thyroid peroxidase
41
Which transporters gets T4 into the blood?
MCT8
42
Why do growth hormones have along half life?
Travel bound to binding proteins
43
How do thyroid hormones cause thermogenesis?
Promote less efficient ATP synthesis, increase brown fat oxidation, upregulate futile cycles
44
How are thyroid hormone receptors activated?
Dimers attached to thyroid hormone responsive elements (TRE), co-repressor released when hormone attaches
45
Which kinase does thyroid hormone receptor activate?
janus kinase 2 which phosphorylates tyrosine
46
How does growth hormone promote growth at growth plates?
Released during high AA levels, promotes uptake by muscle and chondrocytes, promotes growth
47
What takes the role of prolactin in cows?
Growth hormones
48
What is a diabetogenic effect?
Inhibits glucose uptake
49
What is growth hormone released in response to during fasting?
Ghrelin, hypoglycaemia, low FFA levels
50
What does growth hormone do during fasting?
Increased lipolysis and FFA release, stimulates gluconeogenesis and hepatic glucose output
51
What is pituitary dwarfism?
Defective growth hormone axis, either can't produce or respond to it, small but correct proportions
52
What is pituitary gigantism?
Pituitary tumour causing joint problems, diabetes, tunnel vision
53
Why does pituitary gigantism cause tunnel vision?
Squashed optic chiasm
54
What is dwarfism of Sindh?
GHRH receptor deficiency
55
What is Laron syndrome?
GH receptor deficiency
56
What is african pygmy?
IGF-1 receptor deficiency
57
What is Achondroplasia?
Mutation of fibroblast growth factor receptor
58
What is acromegaly?
Where growth hormone is oversecreted and periosteal bone growth continues
59
What induces growth plate closure?
Oestrogens (in males testosterone is converted to oestrogen for this)
60
When is insulin-like growth factor released?
By liver in response to growth hormone
61
What does IGF-1 do?
Inhibits somatostatin release by pituitary
62
What is IGF needed for in bone?
Hypertrophy not proliferation
63
What is the dual effector hypothesis?
Where GH stimulates chondrocyte differentiation and local IGFs which drive further growth
64
Why are people with dodgy growth hormones born normal sie?
Growth hormones not needed in utero
65
What produces fibroblast growth factor 21 and what does it promote?
Liver when fasting, promotes growth hormone resistance
66
How does liver increase levels of free IGF-1?
Augments its production and reduces levels of binding proteins
67
Where is the adrenal cortex from?
Mesoderm
68
Where is the adrenal medulla from?
Neural crest
69
Which does IGF-2 do in the fetus?
Expressed in placenta as imprinted gene from father for large placenta and nutrient transfer
70
Which IGF is for fetal growth and which is for embryonic?
IGF-2 is embryonic, IGF-1 is fetal
71
Which way does adrenal blood flow?
Outside > inside
72
Which enzyme does adrenaline > NA?
PNMT
73
What are adrenal androgens?
Produced by reticularis, only significant in females, can be converted to oestrogen after menopause
74
What happens to pro-opiomelanocortins?
Cleaved to produce stuff eg ACTH
75
WHat is ACTH needed for?
Cortex growth and function
76
What forms MSH?
ACTH
77
When is cortisol released?
Anxiety, trauma, infection, hypoglycaemia, pain
78
What does cortisol promote?
Protein breakdown, inhibits glucose uptake, promotes FFA release, protects and maintains liver glycogen stores
79
What does cortisol do to immune system?
Blocks it but could be bringing down to normal after alarm response
80
What are some other effects of cortisol?
In the fetus, allows arterioles to respond to other hormones, affects food, memory and sleep, inhibits collagen synthesis and bone formation, suppresses reproductive function
81
How does glychrrhetinic acid cause hypertension?
Inhibits enzymes which breaks down cortisol
82
How do you measure BMR?
at rest, thermoneutral. 12-14 hours after last meal
83
Which are essential fats?
Plasma membrane, myelin
84
How to work out metabolic rate?
Normal diet RQ = 0.82, gives 20.2 kJ per litres O2, measure O2 useand times by 20.2
85
What are the two kinds of storage fat?
Android and gynoid
86
Formula for body fat volume underwater?
5.5(total body volume - residual volume) - 5 x mass
87
What is Bioelectrical Impedence Analysis?
Measure electrical resistance between two points
88
Which hormones increase blood sugar levels?
Glucagon, cortisol, growth hormone, adrenaline
89
Which hormones inhibits alpha cells?
Glucose and insulin
90
Why does insulin decrease but glucagon not rise overnight?
So everything insulin blocks can occur
91
What causes Kwashiorkor?
Inadequate protein, enough calories so break down plasma protein so oedema
92
What is marasmus?
Enough protein but not enough calories
93
What happens in fasting phase 1?
Glucagon high, insulin low, growth hormone rises, cortisol changes little, T3 decreases so metabolic rate drops, lipolysis and ketogenesis from growth hormone
94
What happens in fasting phase 2?
Insulin low, glucagon normal, FGF21 released by liver to block growth hormone, protein catabolism slows, fat metabolim inreases, ketogenesis increases further
95
What happens during fasting phase 3?
Cortisol rises to access protein mucle usage, no mroe fat reserves, die after 1/2 of protein reserves gone, die because can't cough - get pneumonia
96
The metabolic rates of which tissues are the most variable?
Heart and skeletal mucsle
97
How is damage from neonatal asphyxia reduced?
Hypoxic hypometabolism is accompanied by anapyrexia
98
How does cold affect cardiac output?
Reduces
99
What happens to skeletal muscle as it cools?
A fall in force
100
Why do testes have a lower optimum temperature?
Fertility decreases if warmed
101
What's the equation for mean body temperature?
0.9 core + 0.1 skin
102
WHy are oral temperatures not good?
Evaporation
103
What do ear probes measure?
Tympanic membranes
104
What happens if body temp was any higher?
C-C bonds would break
105
What happens if body temp was any lower?
Molecules wouldn't have enough energy
106
How do camels thermoregulate?
Start day at low temperature and have larger extremes in body temperature if dehydrated because they're saving water
107
What is torpor?
Inactive but not actually asleep, major reduction of metabolic rate
108
What is bears "hibernation"?
Don't hibernate but heart and metabolic rate drops, temp doesn't drop as low as true hibernators and can wake nearly instantly
109
What temp is life threatening?
40 degrees
110
What temp has 50% chance of survival?
41.5 degrees
111
What temp has 30% survival?
42.1 degrees
112
What is haemoconcentration?
Dehydration using thermoregulation causing increased risk of thrombosis and cardiac workload increases
113
What is perniosis?
Chilblains - rapid warming following cold damages capillary beds
114
What causes frostbite?
Irreversible damage due to water crystals and increased osmolarity
115
What is a heterotherm?
Something which hibernates so hibernating mammals are heterothermic endotherms
116
How much heat to humans produce?
100 W
117
What does the pre-optic area do?
Integrates info from hypothalamus and feedforward signals from skin
118
What control is shivering under?
Somatic
119
What are the two types of peripheral thermoreceptors?
Warm or cold
120
Which nerves do peripheral thermoreceptors use to the spinal cord?
Afferent fibres (A delta and C)
121
Which transient receptor potential ion channels are activated by heat?
TRP V1, V2, V3
122
Which transient receptor potential ion channels are activated by cold?
TRP V5
123
What causes non-shivering thermogenesis?
Brown adipose tissue
124
What activates brown adipose tissue?
NA (sympathetic) via B3 receptors
125
WHat does UCP1 do in brown fat?
Uncoupling protein 1 - activated by long chain fatty acids from lipolysis of cytoplasmic lipid droplets from adrenergic stimulation
126
What prevents malignant hyperthermia?
Dantrolene
127
What does bird countercurrent between arterial and venous blood do?
Good blood supply and temperature gradient
128
How are arteriovenous anastomoses in hairless skin controlled?
Vasoconstrictor sympathetic control, tonic activity keeping them shut
129
What nerve control does hairy skin have?
Vasoconstrictor NA supply and vasodilator cholinergic supply
130
Does panting cause salt loss?
No
131
How does shallow panting reduce alkalosis?
Only ventilating upper respiratory dead space
132
Why do dogs pant at ribcage resonant frequency?
To reduce work
133
What is a rete mirabile?
Venous blood cooling arterial blood in specialised structures
134
What happens to sweat at high flow rates?
Hypotonic at low flow rate and more concentrated but still hypotonic at high flow rates
135
What happens to sweat in athletes?
Occurs earlier and in larger volumes
136
What is pyrexia?
Fever
137
What is a pyrogen?
Raises body temperature
138
What are some pyrogens?
Cytokines, pathogens, prostaglandins
139
What is an example of an antipyrexic?
NSAIDs
140
When can fevers be useful?
Signal need for rest, can indicate if treatment is working
