Transcript Comparative Vertebrate Physiology

Human Anatomy and
Physiology
Endocrinology
Overview

Nervous system



electrochemical impulses regulate muscles
and glands
quick response
Endocrine system



influences metabolism via chemical messages
prolonged response
Endocrine versus exocrine glands
Endocrine glands

Major glands


Other glands


Pituitary, thyroid, parathyroid, adrenal, pineal and
thymus glands
Pancreas, gonads
Organs/tissues producing hormones

Adipose tissue, intestine, stomach, kidneys, heart
Hormones

Steroidal


Gonads, adrenal glands
Amino acid based

Works by a secondary messenger system



Cyclic AMP : cAMP signaling mechanism
PIP-Calcium signaling mechanism
cAMP components

Receptor, G protein, adenylate cyclase, cAMP, protein
kinase
Cyclic AMP signaling
Cyclic AMP signaling

Steps









First messenger
GDP displaced by GTP
Activation of G-protein
Activation of adenylate cyclase
Hydrolysis of GTP to GDP
Inactivation of G-protein
Second messenger cAMP from ATP
Activation of protein kinase
Activation of metabolism
PIP calcium signaling
PIP calcium signaling

Steps










First messenger
GDP displaced by GTP
Activation of G-protein
Activation of phospholipase
Hydrolysis of GTP to GDP
Inactivation of G-protein
Phospholipase splits PIP2 into DAG and IP3
DAG and IP3 act as secondary messengers
DAG activates protein kinases, IP3 triggers Ca++ release
from ER
Ca++ activates channels on plasma membrane or binds
to calmodulin which activates metabolism
Steroidal hormones
Steroidal hormones

Steps






Diffuse into cell and enter nucleus
Bind to receptors to form receptor complexes
Complexes bind to DNA
Production of mRNA
mRNA + ribosomes make proteins
Proteins include enzymes that stimulate
metabolism
Hormones


Hormones travel in blood free or bound to
protein carriers
Blood hormone concentration decreases



Degraded by target organs
Removal by kidneys and liver
Half-life (seconds to 30 min.)
Hormone release




Three major stimuli
1. Humoral
 Ca++ lowering causes PTH release
2. Neural
 SNS stimulates adrenal gland to release epinephrine
3. Hormonal (common)
 Hypothalamus releases hormones that cause pituitary to
release other hormones (e.g. GnRH to FSH)
Growth hormone

Site of release


Target organ


All body organs especially bones and skeletal
muscle
Stimulation


Anterior pituitary
Primarily in adolescence, low levels of GH
Feedback mechanism

High levels of GH, hyperglycemia, obesity
Thyroid hormone precursors
Hypothermia
TRH
TSH
T3 & T4
Increase in metabolism
& body temperature
Thyroid hormone

Stimulation


Falling levels of T3 (triiodothyronine) and T4
(thyroxine). TH raise BMR and heat production
Feedback mechanism

Increase in BMR and body heat (i.e., exercise)
Parathyroid hormone

Site of release


Target organ


Bone, intestine, kidneys
Stimulation


Parathyroid glands
Falling Ca++ blood levels
Feedback mechanism

Increase in Ca++ blood levels
Parathyroid hormone

Ca++ needed for nerve impulses, muscle contraction and blood
clotting
Adrenocorticotropic hormone

Site of release


Target organ


Adrenal cortex (glucocorticoids)
Stimulation



Anterior pituitary
Stress (i.e., fever, hypoglycemia)
cortisol
Feedback mechanism

Increase levels of blood glucocorticoids
Adrenal gland hormones


Mineralocorticoids (aldosterone)
Site of release


Target organ


Kidneys
Stimulation


Adrenal cortex
Decrease in blood volume, pressure, Na+ level
Feedback mechanism

Increase in blood volume, pressure, Na+ level
Adrenal gland hormones


Epinephrine and norepinephrine
Site of release


Target organ


Heart, vasculature, bronchioles
Stimulation


Adrenal medulla
Sympathetic nervous system (SNS)
Feedback mechanism

None. SNS stimulation decreases when
needed
Pancreatic hormones

Insulin and glucagon
Meal
( plasma glucose)
Starvation
( plasma glucose)
insulin from
pancreas
glucose
uptake
into cells
plasma
glucose
glucagon
glycogen
from
(skeletal
plasma
pancreas
muscle,
liver)
glucose
converted
to glucose
Other hormones

Renal


Arginine vasopressin (antidiuretic hormone - ADH)
Reproduction



Follicle-stimulating hormone (FSH)
Luteinizing hormone (LH)
Oxytocin