Endocrine Physiology Flashcards
What is the endocrine system responsible for?
homeostasis
What 6 things are regulated by the endocrine system?
- growth
- development
- reproduction
- blood pressure
- concentrations of substances in blood
- behavior
What are the 9 classical endocrine glands?
- hypothalamus
- anterior and posterior lobes of the pituitary
- thyroid
- parathyroid
- adrenal cortex
- adrenal medulla
- gonads
- placenta
- pancreas
What are the 3 classes of hormones?
- peptides and proteins
- steroids
- amines
What are peptides and proteins synthesized from?
amino acids
Describe the steps involved in the synthesis of peptide hormones
1) DNA is transcribed into mRNA
2) mRNA is translated on the ribosomes to the first protein product, a prepohormone
3) the signal peptide is removed in the endoplasmic reticulum, converting the perpohormone to a prohormone
4) the prohormone is transferred to the Golgi apparatus
5) the final hormone is stored in secretory vesicles until the endocrine cell is stimulated
Steroid hormones are synthesized and secreted by what 4 endocrine glands?
- the adrenal cortex
- gonads
- corpus luteum
- placenta
All steroid hormones are derivatives of what?
cholesterol
What are the 6 steroid hormones?
- cortisol
- aldosterone
- estradiol and astriol
- progesterone
- testosterone
- 1,25-dihydroxycholecalciferol
What are amine hormones derivatives of?
tyrosine
What are the 4 amine hormones?
- catecholamines (epinephrine, norepinephrine, and dopamine)
- thyroid hormones
Adjustments in secretion of hormones is accomplished via what?
neural or feedback mechanisms
Neural mechanisms are illustrated by what?
By the secretion of catecholamines into the circulation
Which mechanism is more common?
feedback mechanisms
What are the 2 types of feedback mechanisms?
Negative and Positive
Which type of feedback is the most important and common mechanism for regulating hormone secretion?
negative feedback
What does negative feedback mean in endocrine systems?
That some feature of hormone activity action, directly or indirectly, inhibits further secretion of the hormone
What is the net result of any version of feedback?
When hormone levels are judged to be adequate or high, further secretion of the hormone is inhibited.
When hormone levels are judged to be inadequate or low, secretion of the hormone is stimulated
What is an example of negative feedback?
The hypothalamic-pituitary axis
Is positive feedback very common?
No
What is the basis of positive feedback?
Some feature of hormone action causes more secretion of the hormone
What are a couple examples of positive feedback?
- the opening of Na+ channels during the upstroke of an AP
- oxytocin
Negative feedback is self-_____, whereas positive feedback is self-_____.
limiting
augmenting
The responsiveness of a target tissue to a hormone is expressed via what relationship?
the dose-response relationship
Describe the dose-response relationship
The magnitude of a hormone response is correlated with hormone concentration
As hormone concentration increases, the response usually ______ and does what?
increases and then levels off
What is sensitivity?
The hormone concentration that produces 50% of the maximal response
If more hormone is required to produce 50% of the maximal response, than there has been a _____ in sensitivity of the target tissue.
decrease
What are 2 ways in which sensitivity can be altered?
- by changing the number of receptors
- by changing the affinity of the receptors for the hormone
A change in the number or affinity of receptors is called what?
down-regulation or up-regulation
Down-regulation is a mechanism in which a hormone ______ the number or affinity of its receptors in a target tissue.
decreases
Up-regulation is a mechanism in which a hormone ______ the number or affinity of its receptors in a target tissue.
increases
