Neuroendocrine Flashcards
What are hormones?
They are chemical messenger produced in one location and transported to a second location
What does the endocrine system do?
- maintain homeostasis
- regulate growth and development
- control energy storage and use
- mediate the body’s response to environmental cues
What is neurocrine communication?
When a hormone is a neurotransmitter
What is paracrine communication?
When a hormone acts on neighbouring cells
What is autocrine communication?
When a hormone hits back on its origin cell
What is the synergistic effect?
The effect of two hormones together is greater than the addition of the two effects
What is melatonin?
It is a product of tyrosine and it produced by the pineal gland. it is produced when it is dark, in order to adjust the circadian rhythm
What is the GHRH axis stimulated by?
exercise, stress, fasting, low glucose and sleep
What is the result of excess growth hormone production?
Giganticism (can be caused by a pituitary gland tumor, usually benign)
How do the hypothalamus and posterior pituitary communicate?
Hypothalamus neurons have their axon terminal projecting to the posterior pituitary
What hormones does the posterior pituitary produce?
oxytocin and vasopressin
What is vasopressin?
also called anti-diuretic hormone. VP is secreted in response to increased plasma osmotic pressure or increased blood volume. inhibits urine production and causes blood vessel contraction
what does oxytocin to?
- it acts upon the kidney to promote sudium excretion,
- increases release of atrial natriuretic factor from the heart,
- contracts mammary ducts for milk let-down
- causes uterine contraction during delivery
What 2 structures make up the matrix of the adrenal gland?
- cortex - capsulated the medulla, it on the outside
2. medulla - on the inside
Where are androgens secreted in the adrenal gland?
The reticularis zone
What does the adrenal medulla secrete?
E and NE
What is the steroid precursor?
cholesterol
What are the cardiovascular effects of adrenaline?
- increase cardiac contractility
- increase heart rate
- dilate smooth muscle around arterioles
- constrict other arterioles
- shunt blood to exercising muscles and the brain
What hormone has similar metabolic effects to adrenaline?
cortisol
What are the effects of chronic stress?
increased cortisol secretion, which leads to:
- decreased immune function
- increased risk of infection and cancer
- worse diabetes due to anti-insulin effects
- decreases bone density
- induces infertility
What is the kJ/g for carbohydrates, fat and protein?
carbohydrates = 17 kJ/g protein = 17 kJ/g fat = 37kJ/g
How much kJ/g is there is one Cal?
Cal = 4.14kJ/g
What is hypoglycaemia?
decreased CNS function, come and death due to decreased blood sugar levels
What is hyperglycaemia?
too high blood glucose levels which can lead to osmotic duress, dehydration, vascular collapse or even death
What makes glucose the main energy source?
it produces the most ATP
What do pancreatic islet delta cells secrete?
somatostatin
How many pancreatic islet of Langerhans are there?
1-3 million
What is the structure of insulin receptor?
two extracellular alpha chains and two membrane spinning beta chains
What is the incretin effect?
orally injected insulin leads to a large effect of insulin secretion, while when glucose is injected intravenously, insulin secretion is reduced. this is used as a marker for diabetes diagnosis.
What is type I diabetes?
loss of beta cells in the pancreas leading to a deficiency in insulin. it is an autoimmune disease
What is type II diabetes?
insulin resistance or reduce insulin sensitivity
What organ controls the production of glucose in the liver?
the brain. we have an insulin receptor in the hypothalamus
What is the accuracy of the difference between consumed and spent energy?
99.8%
do humans have a hormone that can digest fructose?
no
What do mutations in leptin receptors lead to?
they can lead to truncate of the intercellular domain, so when leptin binds so no signal is produced
What happens when we get obese (in response to leptin)?
When we get obese, we absorb more fat and build more adipose tissues. this results in increased leptin secretion. however, leptin secretion is increased to the point where the leptin receptor in the hypothalamus becomes desensitised to leptin. now the brain is leptin resistant.
What is gametogenesis?
sperm production in the testes and ova development in the ovary
What are the units which produce sperm?
seminiferous tubules
Where does storage of the sperm occur?
in the epididymis
How many ovulation dominant follicles do we have?
~450
What is the corpus luteum?
It is the remnants of the dominant follicle but without the ovum. it is made of enlarger granulosa cells
What does the corpus lute secrete?
estrogen, progesterone and inhibin
What is the folliclular phase?
it is follicular development, prior to ovulation
What is the luteral phase?
when the corpus luteum is active, after ovulation
How do the contraceptive pills prevent ovulation?
by maintaining negative feedback, so the LH surge doesn’t occur and neither does ovulation
What is the LH surge?
After the estradiol levels reach a certain threshold for a minimum of 2 days—and perhaps because of the accelerated rate of estradiol secretion—the hypothalamic-pituitary axis reverses its sensitivity to estrogen. That is, estradiol now exerts positive feedback on the axis. The LH surge is an abrupt and dramatic rise in the LH level that occurs around the 13th to 14th day of the follicular phase in the average woman. The LH surge peaks ~12 hours after its initiation and lasts for ~48 hours. The LH surge causes the dominant follicle to rupture and releases its oocyte—ovulation.
