Physiology 3120 Lecture 56: Phys 3120 - Lecture 56
2 May 2018
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Human Physiology Lecture 56
Stress
- Adrenal medulla: help produce catecholamine (fight or flight)
- Adrenal cortex: address stress (subjected to fear, hyperglycemia, cold temperature)
o Activate hypothalamic pituitary adrenal axis – make cortisol (steroid hormone) helping you
deal with long term stress
o Biggest thing that occurs due to cortisol = raise blood glucose
▪ Blood glucose is sent to the brain
▪ Oppose the actions of insulin
▪ Behave in similar manner in glucagon BUT unlike glucagon, cortisol can be released
under stress rapidly
Functional Anatomy
- CORTEX
o 3 “zones”
▪ 1. Zona glomerulosa - aldosterone
▪ 2. Zona fasciculata – cortisol
▪ 3. Zona reticularis – sex steroids
o Source of adrenal steroids
▪ Factory for making steroid hormones
o Regulated by pituitary ACTH
o Zona glomerulosa - aldosterone
o Zona fasciculata – cortisol
o Zona reticularis – sex steroids
- MEDULLA
o Composed of “chromaffin” cells
o Source of catecholamines (in addition to the sympathetic nervous system
▪ Short term stress – not just enough from the sympathetic nervous system, you need
the adrenal medulla
o Secretion controlled by direct innervation; neuroendocrine response
▪ Often sensed by higher centers in the brain
Adrenal Steroidogenesis
- Occurs in the adrenal cortex
- All steroid hormone precursor = cholesterol
o Due to different intercellular enzymes in the adrenal cortex, the cholesterol can be converted
to different hormones depending on the activity of the intercellular enzymes to produce
corticosterone (inactive cortisol) or aldosterone
- Ultimately lead to 3 things:
o Corticosterone aldosterone
o Cortisol
o Estradiol
- Adrenal cortex plays a big role in helping us make testosterone and estradiol
- Intercellular enzymes in adrenal cortex play a bigger role than the synthesis of cholesterol itself
o Interconversion of the hormones and activity of the intercellular enzymes matters more than
the actual amount of hormone produced
o Hormones can be converted en route to its receptor by action of these intracellular enzymes
- KNOW THAT
o All steroid hormones come from a cholesterol precursoe
o Interconversion of hormones occurs due to these cytochrome p450 enzymes that are
situated in the cortex
- Steroidogenic enzymes are cytochrome p450s—e.g. CYP17
- Found in membranes of mitochondria and ER (of adrenal cortical cells)
- Energy comes from electron transport chain
- Adrenal cortex is a factory to make all of our steroid hormones
Major Pathways for the Synthesis of Steroid Hormones in he Adrenal Cortex
- Adrenal cortex can make precursors for reproductive sex hormones
HPA Axis
- Hypothalamic pituitary adrenal axis
o In response to systemic stress (long term stress)
- Hypothalamus releases corticotropin release hormone (CRH)
o Via – cells it acts on CRH receptors in the anterior pituitary, which releases ACTH
- ACTH is peptide hormone
o Comes along in the blood, circulate and bind to ACTH receptors in the adrenal cortex
o Elicit increase in cortisol production from the adrenal cortical cells
- When levels of cortisol get too high in circulation, it shows down production of CRH at level of
hypothalamus and ACTH at the level of the anterior pituitary
- CORTISOL:
o Increased blood glucose
▪ Get blood glucose to the brain
o Gluconeogenesis in liver and other organs
o Muscle catabolism (amino acids)
▪ Break down proteins, liberate amino acids, which is used by the liver to make more
blood glucose
o Inhibition of GLUT4 activity
▪ Imposes actions of insulin
▪ If we supress GLUT4 in muscle or adipose, we are going to keep blood glucose high
Document Summary
Adrenal medulla: help produce catecholamine (fight or flight) Zona reticularis sex steroids: source of adrenal steroids, factory for making steroid hormones, regulated by pituitary acth, zona glomerulosa - aldosterone, zona fasciculata cortisol, zona reticularis sex steroids. Medulla: composed of chromaffin cells, source of catecholamines (in addition to the sympathetic nervous system. Short term stress not just enough from the sympathetic nervous system, you need the adrenal medulla: secretion controlled by direct innervation; neuroendocrine response, often sensed by higher centers in the brain. Ultimately lead to 3 things: corticosterone aldosterone, cortisol, estradiol. Adrenal cortex plays a big role in helping us make testosterone and estradiol. Intercellular enzymes in adrenal cortex play a bigger role than the synthesis of cholesterol itself. Interconversion of the hormones and activity of the intercellular enzymes matters more than the actual amount of hormone produced: hormones can be converted en route to its receptor by action of these intracellular enzymes.
