Hormones
Signaling molecules / chemical messengers that regulate physiology and behavior
Hormone types
- Amino acid based - proteins, peptides (most common)
- Steroids - made from cholesterol in gonads & adrenal cortex
Major endocrine glands (9)
- Pineal
- Hypothalamus
- Pituitary
- Thyroid
- Parathyroid
- Thymus
- Adrenal glands
- Pancreas
- Gonads (ovaries/testes)
The 2 ways hormones act on receptors:
- Direct gene activation - lipid soluble (steroids & thyroid)
- Second messenger system - water soluble, G proteins, cascade (all AA except thyroid)
3 types of endocrine gland stimulation:
- Humoral - blood levels of ions & nutrients
- Neural
- Hormonal - other hormones
Target cell activation depends on (3 factors):
- Blood levels of hormones
- Relative # of receptors at cell (up regulation/down regulation)
- Affinity (strength of bond)
Determinants of hormone concentration (2 factors):
- Rate of release
- Rate of inactivation & removal via enzymes, kidney + liver > urine/feces
Hormonal interaction (3 types):
- Permissiveness - one requires another* for full effects
- Synergism - multiple w/ same effects, amplified when combined
- Antagonism - opposite effects
Tropic hormones
Hormones that have **other endocrine glands as their target
Aka tropins, “controller hormones”
Nervous system vs. Endocrine system
Nervous system = “built for speed”, rapid on/off
Endocrine system = acts more slowly, regulates processes that GO ON (effects can be long-lasting & diverse)
Hormones circulate to ALL organs but are _______
Receptor specific
Adrenal cortex vs. Adrenal medulla
Cortex: 3 groups of corticosteroids, long-term/chronic stressors, stim. by ACTH from ant. pituitary
Medulla: catecholamines, short term stressors, stim. by sympathetic NS
3 Stages of Hans Seyle’s General Adaptation Syndrome:
- Alarm stage (adrenal medulla/sympathetic NS)
- Resistance stage (adrenal cortex/glucocorticoids)
- Exhaustion stage
