Flashcards in Hypothalamo-hypophysial axis Deck (42):
Functions of the endocrine system?
- growth and development
- sex differentiation
- adaption to an ever changing environment: regulation of digestion, use and storage of nutrients, electrolyte and water metabolism, and reproductive functions
Where does magnocellular neurosecretory neurons have their effect?
- posterior lobe of the pituitary gland (on oxytocin and ADH)
Where does the parvocellular neurosecretory neurons have their effect?
- on anterior lobe of the pituitary gland
Autonomic nerves have effects on what target organs?
- pancreas (has both pre and post ganglionic autonomic neuron) and adrenal gland (just preganglionic autonomic neuron)
What do hormones function as?
- move through the blood/lymph to distant target sites of action (these are endocrine and neuroendocrine cells)
- can also act more locally as paracrine or autocrine (have effect on themselves (like a T cell) messengers that incite more local effects
- most are present in body fluids at all time in greater or lesser amounts as needed
- signal amplification
Characteristics of hormones?
- a single hormone can exert various (pleiotropic) effects in different tissues
- a single function can be regulated by several hormones (ex: HR)
How do water soluble hormones effect cells?
- needs a receptor on cell membrane -> first messenger binds to receptor and this activates G protein , effector cell and second messenger and target cell response in the cell
How do fat soluble hormones effect cells?
These can pass right through cell membrane and bind to receptor, now it is able to go into nucleus and have impact on cell
What are the factors that affect the response of a target cell to a hormone?
- blood level of the hormone
- relative number of receptors: up-regulation, down regulation
- affinity of these receptors for hormones: affected by number of conditions, ex: pH of body fluids plays an important role in the affinity of insulin receptors
Describe up and down regulation of the receptors?
up regulation: number of receptors on the cell wall are increased so this means that there are more areas for the hormones to attach so more hormones are secreted resulting in a greater response
down regulation- ex: sympathetic system stimulates heart for prolonged periods -> leads to tachycardia and to reduce tachycardia, the receptor sites on teh cell are reduced, and there are less receptors for hormones to attach to. Beta blockers decrease the number of sites available on the cell surface, being selective and increasing output
Humoral response of parathyroid glands to low concentration of Ca2+
- capillary blood contains low concentration of Ca this stimulate secretion of parathyroid hormone (PTH) by parathyroid glands
Neural effect on medulla of adrenal gland?
- preganglionic SNS finber stimulates adrenal medulla cells to secrete catecholamines
Hormonal effect on hypothalamus and target organs?
- the hypothalamus secretes hormones that stimulate the anterior pituitary gland to secrete hormones that stimulate other endocrine glands to secrete hormones (thyroid, adrenal cortex and gonads)
How are hormone levels controlled?
- affected by fluctuations that vary with the sleep-wake cycle: GH and ACTH
- secreted in a complicated cyclic manner: femal sex hormones
- regulated by feedback mechanisms that monitor substances such as glucose (insulin) and water (ADH) in the body
- regulated by feedback mechanisms that involve the hypothalamic pituitary target cell system
When do glucocorticoid levels peak?
after you wake up in the morning, between 8 and 9 am (maybe why MIs occur more in the morning)
What has an effect on estrogen levels?
- LH and FSH, when they peak -> estrogen levels rise
Categories of hormones according to structure?
- biogenic amines
- amino acids, peptides, polypeptides, proteins, and glycoproteins
- fatty acid derivatives
Hormones that the hypothalamus secretes?
- TRH, GnRH, CRH, GHRH, somatostatin
Hormones that the anterior pituitary secrete?
- ACTH, TSH, FSH, LH, PRL, GH
Hormones that the posterior pituitary secrete?
- oxytocin and ADH
Hormone that the thyroid secrete?
Hormones that the pancreas secretes?
glucagon, insulin, somatostatin
Hormone that the kidney secretes?
Hormone that the heart secretes?
Hormones that the GI tract secretes?
gastrin, CCK, secretin, GIP, somatostatin, GLP-1
Hormone that adipocytes secrete?
What are the 2 groups of hormones that are derived from the amino acid tyrosine?
- thyroid hormones are basically a double tyrosine with critical incorporation of 3 or 4 iodine atoms
- catecholamines include epi and NE, which are used as both hormones and neurotransmitters (act on vasculature)
Process from preproinsulin to insulin
- preproinsulin -> signal sequence is cleaved off --> proinsulin --> chain c cleaved off -> insulin (chain A and B), now active
Leptin makes you feel?
- full, pts that are obese have decreased sensitivity to leptin
What is the hunger hormone?
What hormones are made in zona fasciculata of adrenal gland cortex?
cortisol and corticosterone
What hormone is made in the zona glomerulosa?
What hormones are made in the zona reticularis?
Why is the pituitary gland so heavily vascularized?
-to allow for rapid access of blood to pituitary and rapid release of hormones
5 cell types of the anterior pituitary gland?
- thyrotrophs: produce thyrotropin, also called TSH
- corticotrophs: prouce corticotrophin, also called ACTH
- Gonadotrophs: produce gonadotropins -> LH and FSH
- somatotrophs: produce GH
- lactotrophs: produce prolactin (production of milk)
How does the negative feedback loop work?
- endocrine cell releases hormones -> target cell -> this illicit a physiologic response and since there is an increase in hormone levels it stops the endocrine cell from secreting anymore hormones and this results in decrease in hormone levels
How does the positive feedback loop work?
endocrine cells releases hormones so increase in levels -> target cell and ilicts a physiologic response and it tells the endocrine cell to keep on secreting hormones even though levels are increasing (positive feedback with continued hormone production)
Where does glucocorticoids provide negative feedback?
- to hypothalamus (stop producing CRH) and to the anterior pituitary gland (stop producing ACTH)
What stimulates the production of cortisol?
stress -> stimulate hypothalamus to produce CRF -> this stimulates anterior pituitary to produce ACTH and this stimulates adrenal glands to produce cortisol and when enough is produced it will decrease stress inhibit hypothalamus and pituitary glands from producing hormones.
Production of LH and FSH?
- hypothalamus produces GnRH which stimulates anterior pituitary to produce LH and FSH and this will have effect on gonads (testes) -> LH produces testosterone and rising levels of testosterone will inhibit anterior pituitary production of LH and hypothalamus, FSH produces inhibin in testes this will inhibit anterior pituitary production of FSH
Parturition feedback loop?
postive feedback loop
PG (prostaglandins) -> uterine contractions -> positive feedback -> increased stretch -> more uterine contractions
Oxytocin -> uterine contractions -> positive feedback loop -> more oxytocin
Ocytocin -> positive feedback to PG -> uterine contractions
->contractions until baby is delivered