22 - Endocrine & Pituitary Flashcards
How is endocrine system different from the nervous system
NS: direct connection to target cells
- through neurotransmitters
- works in milliseconds
- effects are brief
Endocrine: hormones enter the blood to circulate throughout the body and affect the activity of distant cell
- binds to receptors
- through hormones
- can take seconds, hours or days
- duration of action longer
What are the types of glands in the body
exocrine (secrete products into ducts)
endocrine (secrete products into the blood or tissues fluids)
what is a circulating hormone
most endocrine hormones
travel through the blood to distant tissues
What are local hormones
act on a paracrine or autocrine fashion
paracrine: act on neraby cells
autocrine: work on the cell that released them
Describe the path of lipid solupble (lipophilic) hormones
cross the plasma mebrnae to act on intracellular receptors (cytoplasmic or nuclear) that affect levels of gene transcription
- lipophilic hormone diffuses into cell
- activated receptor-hormone complex binds response element on DNA to alter gene expression
- newly formed mRNA directs synthesis of specific proteins on ribosomes
- new proteins alter cellular activity
Describe the path of water-soluble (hydrophilic) hormones
cannot cross the plasma membrane –> act on cell surface receptors
- allows for amplication effect
- hydrophilic hormone (first messenger) binds to receptor and activates G protein
- activated adenylate cyclase coverts ATP to cAMP (second messanger)
- cAMP activates protein kinases
- activated kinases phosphorylate cellular proteins
- millions of phosphorylated proteins cause reactions that produce physiological responses
How are endocrine hormones controlled
1) signals from the NS
2) chemical changes in the blood
3) other hormones
most operate through negative feedback mechanism
What are the two parts of the pituitary
anterior pituitary (adenohypophysis: more of a gland)
posterior (neurohypophysis: arises from neurological tissue)
Where is the pituitary found
sits in the hypophyseal fossa
formed between the sellae of the sphenoid bone
How is the pituitary seperated from the sphenoid sinus
with paper thin segment of bone
Where do pituitary tumors largely occur
what would that result in
adenohypophysis (glandular part)
may cause compression of the optic chiasm leading to diplopia (double vision)
- adenomas can be functional (release hormones) or non-functional (does not release hormones)
- pituitary lies deep and posterior to the optic chiasm
TF the pituitary does not have BV around it
False
because the pituitary releases endocrine hormones to the blood stream, there is a rich network of BV around it
TF the ant and post pituitary have seperate circulations
True
both arise from the internal carotid arteries
What is a cause of panhypopituritarism
blood in ant pituitary supplied by portal system (vein –> capillary bed –> vein)
makes anterior pituitary susceptible to damage following a significant hemorrhage
What are the hormones of the posterior pituitary
hormones released from neurosecreotry cells located in the hypothalamus
axons extend through the infundibulum to release their hormones into the capillary network around the posterior pituitary
1) antidiuretic hormone (ADH) - vasopressin because large doses cause vasoconstriction
- released from the supraoptic nucleus
2) Oxytocin
- released from the paraventricular nucleus
