Term test 1- endocrine and renal Flashcards
what is an endocrine gland?
a tissue which releases a substance into the blood stream; the substance then travels via blood to influence a target cell.
what is an exocrine gland?
a tissue which releases substances via ducts
name four kinds of hormones (ie what are hormones)
proteins & polypeptides
steroids
amines: catecholamines and thyroids
what are the 3 levels at which hormones can create an effect?
1) autocrine (sc=tc)
2) paracrine (tctc)
3) endocrine (SC -> TC)
how can hormones bind?
1) receptors in target cells, where very high specificity for a particular hormone, but non-specific binding does occur
* there is continuous trun-over of the receptor-hormone complex.
where are receptors located for most hormones?
on the transmembrane
where are receptors located for steroid hormones?
in the cytoplam
where are receptors located for thyroid hormones?
in the nucleus
explain how transmembrane receptors work.
a hormone binds to an extracellular domain which activates signal pathways. these can then use phosphorylation and enzyme activation, and follow through with DNA, mRNA and protein pathways to respond, and some will directly cause an effect.
explain adenylate cyclase pathways and give an example
1) hormone receptor, G-protein dissociate
2) a-subunit activates AC
3) catalyzes prod of cAMP
4) removes reg unit from PK
5) PK acitvates other molecule-hormonal response.
ie. epinephrine binds to b-adrenergic
explain phosphlipase C-Ca2+ pahtways
1)hormone and receptor
2)g=-proteins dissociate
2) activates PLC
3)causes breakdown of membrane phospholipid to IP3
4) IP3 binds endoplasmic reticulum
5) releases of stored Ca2+ into cytoplam
5)ca2+ activates other molecules-hormonal response
ie epinephrine binds alpha-adrenergic
what does Dopamine (PIH) do?
inhibits secretions of prolactin
what PRH: prolactin releasing hormone do?
stimulates release of prolactin
what TRH: thyrotropin-releasing hormone do?
regulates secretion of thyroid stimulating hormones
what CRH: caticotropin-releasing hormone do?
regulates secretion of adrenocorticotropic hormone [ACTH]
what does GHIH somatosin do?
it inhibits secretion of growth hormone [GH].
what does GHRH, growth hormone releasing hormone do?
it stimulates secretion of GH.
what does GnRH: gonadotropin-releasing hormone do?
regulates secretion of gonadotropin-releasing hormone, luterinizing [LH] and follicle stimulating hormone [FSH].
what is involved in the hypothalamus-anterior pituitary adrenal cortex axis?
hypothalamus releases corticotropin releasing hormone (CRH) which activates the anterior pituitary to secrete the adrenorcorticotropic hormone (corticotropin). this effects the adrenal cortext to increase cortisol levels, which regulates the secretion of hormones by the hypothalamus and the anterior pituitary through negative feedback.
what is cortisol?
its a glucocorticoid, which controls the chronic stress hormone.
explain the CRH synthesis and release. a
what is an inhibitory influence as well?
the central stimulatory stimulates pre-proCRH gene expression, which then stimulates pulsatile release of CRH. the inhibitory influence is that physiological levels of cortisol inbihits release of CRH (negative feedback)
what is the full name of POMC?
proopiomelanocorticotropin
what are some of the peptides off the POMC? (5) and explain them.
1) ACTH (regulates adrenal cortex function)
2) MSH (skin pigmentation in response to UV radiation)
3) EndL (analgesic roles in central nervous system
4) Enk (analgesic roles in fetus)
5) MC3,4,5 (hypothermia, hypotension, feeding behavior, appetite)
what is ACTH, what does it do, where does it move to?
adrenocorticotropic hormone, and it creates the bases for cortisol, and it moves through to the adrenal gland
where is the adrenal gland, and describe it.
located on top of the kidney. like a hat. and it i 2 embryological distinct tissues merged during development adrenal cortex + adrenal medulla.
describe the Adrenal cortex and the adrenal medulla
the cortex: steroid factory
examples: glucocorticoids, muneralocorticoids and sex steroids.
medull: modified sympathetic ganglia-secrete catecholamines* epinephrine
name the adrenal hormones released from the adrenal gland and how they are controlled.
1) glucocorticoids (cortisol) controlled by ACTH
2) sex steroids controlled by ACTH
3) mineralocorticoids controlled by the renin-angiotesin system. (NOT ACTH)
why is cortisol, an adrenal glucocorticoid essential for life>
it cases breakdown of skeletal muscle (gluconeogenesisi), supresses immune system, catabolic on bone, and affects brain function. It keeps the stress levels down. it is a natural regulator of the inflammatory response.
when cortisol levels are high it can lead to what?
cushing’s syndrome. can come from too much ACTH, and it causes changes in carbohydrate and proein metabolism, hyperglycemia, hypertension, muscular weakness.
cortisol helps with what? and what are its levels like during the day? what is its cycle pattern?
cortisol spikes in the morning to help get us up and running. People with insomnia secrete more cortisol around sleep time. it follows a continuous, pulsatile, circadian rhythm.
how does the hypothalamus- pituitary gland work (what is the process)?
the hypothalamus produces thyrotropin releasing hormone (TRH) which acts on the anterior pituitary. that then produces the thyroid-stimulating hormone (TSH) which acs on the thyroid. to produce thyroid hormones that grow the thyroid, and the thyoxine hormones. (this system is controlled by the thyoxines negative feedback where it inhibits responsiveness to TRH and inhibits secretion of TRH).
where is the thyroid gland located?
it is located just below the larynx, on either side of the trachea. Its composed of 2 lobes connected by isthmus. it is also the largest purely endocrine gland.
explain how t3 and t4 are made.
follicles take up iodide from the blood and in the colloid, the enzyme TPO helps attach it to a tyrosine residue in thyroglobulin. the attachment of one iodine produces MIT (monoiodotyrosine) and the attachment of two iodines produces DIT (Diiodotyrosine).enzymes in the colloid modify the structure (through condensation) of MIT and DIT to make thyroid hormones. T3 and T4.
what is the name of T3 and T4
T3= triiodothyronine T4= tetraiodothyronine
how are thyroid hormones transport in the body?
99% will transport in the blood system by means of a plasma carrir protein called thyroxin-binding globulin (TBG)
1 % (free fractions of TH) are biologically active.
what are some secretion properties of Thyroid hormones?
its pulsed because it increases our BMR (highest between 10 am and 2 pm), and it impairs with age. When you are stressed or cold, your thyroid hormones will increase.
what are physiological actions of thyroid hormones?
it elevates basal metabolic rate, needed for normal gonadal development and function, needed for normal embruonic/fetal development, and particularly for the development of the central nervous system.
explain the problem with hypothyroidism.
abnormally low BMR, and results in wright gain, lethargy and intolerance to cold
explain the problem with hyperthyroidism
increased BMR, and results in weight loss, muscular weakness, nervousness, and protruding eyes.
what is Cretinism, how can you avoid it, how was it done?
thyroid hormone is deendent in utero, without it there will be underdevelopment. treatment with T4 soon after birth, completely or almost completely restores development of intelligence. its usually due to innate maternal hypothyrodism, however it can also rise due to diet deficiency with iodine.
what can cause hypothyroidism and hyperthyroidism
insufficient dietary iodide, thyroid gland defect, impaired thyroid hormone pathway, insufficient ant. pit. TSH, insufficient hypothalamic TRH, mutant TSH or TRH receptors, mutant TH transport proteins.
hyper- common in cats
hypo- common in dogs
what are some treatments of thyroid disorders
1) surgery
2) hormone supplementation
3) radiation therapy
4) blockers (thiouracil derivatives-thiocabamides)
5) stimulants (furosemide)
6) diet, electrolyte infusions
describe Growth hormone
it is a protein, with a small half life. it is the most abundant ant. pit. hormone and plays a role in growth. It has insuline0like growth factors (somatomedins) IGF-1 and IGF-2.
describe the GH secretion patterns
GH secretion occurs as several large pulses or peaks each day. the largest GH peak occurs before sleep. over the years the GH secretion slows down (specially after 10 years).
how is GH transported in the flood?
is may be transported as a free hormone but much of GH is bound to binding protein GHBP.