Endocrine Flashcards
Distinguish among autocrine, endocrine, paracrine, and neurocrine secretions
Endocrine:
- cell released hormones into the blood and travels to a distant cell
Neuroendocrine:
- neuron releases hormones into blood and travels to a distant cell
Paracrine:
- cell releases hormones into interstitial fluid and travels to neighboring cell
Autocrine
- cell releases hormones into interstitial fluid and travels to itself
define endocrine gland and hormone
Hormone: secretion into blood
Endocrine gland:
- gland product is released into the blood
list the 3 classes of hormones
- Proteins and Peptides
- from pituitary gland - Steroids
- Tyrosine derivatives (amine)
- from thyroid
understand how water or fat soluble hormones act on target organs
Water soluble hormones (WSH):
- Cell releases WSH into the blood stream via secretory vessicle
- WSH binds to signal receptors on the membrane of the target cell
3a) (optional) WSH enters cell and goes to nucleus to undergo gene regulation
3b) WSH enters target cell and triggers cytoplasmic response
Fat Soluble hormones (FSH):
- Cell releases FSH into the ECM
- Transport proteins in the blood bind to FSH
- FSH then unbinds w/ transport proteins and diffuses through lipid-bilayer
- FSH binds to signal receptor in the nucleus to undergo gene regulation
- FSH enters target cell and triggers cytoplasmic response
understand how concentration of hormones could be regulated
[Hormone] balanced by secretion and clearance
Mechanisms of clearance:
1. metabolic destruction (endoycytosis, enzyme)
2. Binding to tissues (receptors)
3. Excretion by liver into bile
4. Excretion by kidneys into urine
Clearance determinants:
endocrine cell makes free hormone.
free hormone can then:
a. be degraded and excreted
b. become a carrier-bound
hormone (and then become un-bounded)
c. bind to a hormone receptor and either:
c.i unbind from receptor OR
c.ii trigger biological effects
List the different pathways (3) from hormone to cellular response
a) WSH binds to g-protein receptor
b) triggers enzymatic reaction (AC / cAMP/ PLC/ IP)
c) elicits cell response
q) WSH binds to enzyme linked rectpro
b) triggers auto phosphorylation of tyrosine kinase
c) elicits cell response
- a) FSH binds to cystolic / nuclear receptor
b) triggers a DNA hormone response element in the nucleus
c) activates gene transcription
d) elicits cell response
What is cyclic variaiton and provide examples
a repeating pattern define within a given time frame
Ex) Menstural cycle
- different stages of the cycle are linked with different [hormone]
Ex) Cortisol
- corisol levels peak and ebb at regular times of the 24 hour cycle
List the classical endocrine glands (7)
- Pituitary Gland
- Pineal Gland
- Thyroid Gland
- Thymus
- Adrenal
- Pancreas
- Ovary and Testis
Pituitary Gland
- makes, stores, and releases hormones
a. Anterior Pituitary (AP)
- requires hypothalamus to send releasing hormones so that AP can release:
- TSH (thyroid gland –> thyroid hormones)
- FSH + LH (ovaries / testes –> estrogen, progesterone / testosterone)
- ACTH (adrenal cortex –> cortical hormones)
- GH (bones, muscles, organs)
- PRL (breasts)
b. Posterior pituitary
- directly makes and releases:
- oxytocin (breasts and uterus)
- ADH (kidneys)
Can undergo both long and short feedback loops:
- long –> hormones releases by anterior pit lead to hypothalmic control
- short –> hormones released by anterior pit directly feedback into anterior pit
Pineal Gland
- small pea in the middle of the brain
synthesizes melatonin in response to darkness (exposure to light inhibits it)
Throid gland
- wing shaped organ enveloping the c1 and c2 spinal cords
involved in feedback loop with the hypothalamus and pit glan d
- pit gland sends TSH to thyroid gland
- results in excretion and T3, T4, and calcitonin (involved in increased metabolism, growth and development)
Thymus
found near the lungs and enveloping the trachea
releases:
1. Thymopoietin
- fuels production of T cells
- tells pit gland to release hormones
- Thymosin + Thymulin
- makes specialized T-cells - Thymic humoral factor
- regulates immune system
Adrenal
On top of the kidneys
- consists of 2 layers:
1. Cortex
a. zona glomerulosa (salt)
- releases mineralcorticoids (regulates salt and water)
b. Zone fasciculata (sugar)
- releases glucorticoids
c. zona reticularis (sex)
- releases androgen
- Adrenal medulla
- releases catecholamines
Hypothalamus-Adrenal gland feedback
1. Hypothalamus activates ant pit via CRF
2. Ant pit activates adrenal gland via ACTH
3. adrenal gland secretes cortisol
4. cortisoal inhibits hypothalmus
Pancreas
Gluose-level control
- insulin (lowers blood sugar)
- increase uptake of glucose
- promotes glycogensis - glucagon (raises blood sugar)
- promotes glycogenolysis - somatostatin (controls blood sugar)
- mild inhibitions of insulin and glycagon (prevents fluctuations in blood sugar level)
- decreases gut motility and secretion of digestive juices
Discuss the hypothalamic-pituitary axis
The mechanism in which:
- hypothalamus sends releasing hormones (RH)
- Dopamine and Somatostatin are inhibitory (prevent the release of prolactin and GH respectively) - ant pit gland makes and sends appropriate hormones
- causes cellular response in target organs
a. gonads
b. adrenal
c. thyroid
d. mammary gland
e. liver
Understand the anterior and posterior pituitary hormones and their regulation
check slides
Understand the basics of blood glucose regulation by insulin and glucagon
High blood sugar:
- pancreas releases insulin
- stimulates glucose update from blood
a. uptake by tissues
b. glycogen formation in liver - lowers blood sugar level
Low Blood Sugar:
- pancreases releases glucagon
- stimulates glycogen breakdown by liver
- raises blood sugar level
!!! Somatostatin performs paracrine action
- inhibits insulin and glucagon secretion (ensure smooth rise and dips in blood sugar levels)
Understand how cortisol can affect homeostatic maintenance actions
Context: abnormally high cortisol levels (Cushing’s syndrome)
Causes:
- problem in thalamus (release CRH) , ant pit gland (ACTH) , adrenal gland (cortisol)
- drugs
- cancer (releases ACTH)
How to diagnose cause of high cortisol levels
- administer corticoids ( synthetic versions of cortisols)
- (small doses should undergo small feedback loop to ant pit gland)
- if high doses don’t work; it is cushing (move to step 2)
- administer dexmathasone (syntethic version of cortisol but more potent)
- is suppressible –> cushing disease (CT scan the ant pit gland)
- is not suppressible (move to step 3)
- check plasma for ACTH levels
- High plasma ACTH –> ectopic cancer is producing ACTH
- low plama ACTH –> problem with adrenal gland
