Cortisol released from adrenal glands - two parts: cortex and medulla
Adrenal glands structure
1. Three layers - name 'em
Adrenal cortex (outer region - has 3 layers) secretes 3 different steroid hormones.
1. Glomerulosa outer layer secretes: aldosterone (sodium homeostasis – covered in HUBS 192 urinary system lectures)
2. Fasciculata middle layer secretes: cortisol (focus of this lecture)
3. Reticularis inner layer secretes: androgens (minor reproductive role)
Don't memorise this image
Just know that all the reactions taking place are starting from pre-cursor cholestrol - difference reactions occur in difference layers to ger differene steriod hormones
Since they all originate from cholestrol, they're all hydrophobic etc
Cortisol mechanism of action
-In the liver, what happens?
-In muscle, what happens?
1. . Cortisol in blood bound to carrier protein
2. Leaves carrier, enters target cell
3. Binds to receptor in cytoplasm
4. Hormone-receptor complex migrates to nucleus
5. Binds to DNA
6. Transcription of specific genes is activated
7. New proteins made
8. Protein alters (enhances or inhibits) cellular processes in target cell
EFFECTS TAKE MINS TO DAYS TO DEVELOP
• In the liver increased expression of enzymes involved in gluconeogenesis. Liver makes and releases more glucose into the bloodstream.
• In muscle, stimulates breakdown of muscle protein.
• Fat mobilisation
-stress = hypo will increase cortisol
-Gluconeogenesis: process of aa' conversion to glucose
-Liver: thus cortisol related to stress bc when fight/flight, need gluose to form ATP so we have energy to run or fight
-Muscle: stimulates enzyme to breakdown of muscle - free up aa' and liver uses that to make enzymes
-Fat mobil: fatty acids can be used to make ATP (cortisol enourages breakdown of fat in fat cells)
Sequence of events that leads to cortisol secretion and the response of the target cells
1. Cortisol secretion is controlled mainly by.....?
2. What kind hormome is cortisol?
1. Cortisol secretion is controlled mainly by negative feedback (except during the stress response)
2. Cortisol is a steroid hormone
-This feedback loop stops only when stress is gone
-The decrease of glucose uptake; muscle stopped from taking glucose from blood stream
-We get bursts of cortisol bc hypo gets activated in bursts (so end up with peaks)
-The blood pressure has something to do with arteries so just find out lol
What're cortisol's functions? (7)
• Cortisol influences changes that occur in the body in response to stress including:
Ø Blood glucose levels,
Ø Fat, protein and carbohydrate metabolism to
maintain blood glucose
Ø Immune responses
Ø Anti-inflammatory actions
Ø Blood pressure
Ø Heart and blood vessel tone and contraction
Ø CNS activation
Cortisol secretion: daily pattern
Any disturbances of normal sleep patterns (e.g. jet lag, changing work shifts or a weekend with little sleep) will affect this pathway.
That big peak is reflective of low glucose levels
What happens if you have low cortisol? (8)
- • Brain fog, cloudy-headedness, mild depression
- • Low thyroid function (bc over stimulated)
- • Blood sugar imbalances (hypoglycemia)
- • Fatigue (morning, midafternoon) (both, hv high cortisol & fatigue if low)
- • Sleep disruption
- • Low blood pressure
- • Lowered immune function
- • Inflammation
What's Addison's disease?
1. How does it occur?
2. What are the other symptoms?
1. Not enough cortisol or aldosterone
2. Low cortisol concentration causes the anterior pituitary to increase ACTH secretion
-MSH is a byproduct of ACTH production
-MSH stimulates melanin synthesis and pigmentation of the skin.
3. Low blood glucose, low blood pressure, unexplained weight loss, fatigue, weakness and low blood sodium and high blood potassium.
1. What is it?
2. Read this
1. Too much cortisol
An 8 year old boy was brought to the Endocrine Clinic because of excessive weight gain, high blood glucose and unusually high blood pressure. Scans showed a tumour in the region of the pituitary and tests showed excessive blood levels of the pituitary hormone adrenocorticotrophin.
The diagnosis of Cushing’s disease was made and he was referred for surgical treatment.
1. What're the 2 catecholamines? Realeased by what? What about two other hormones? Released by?
2. What's the adrenal divided into?
3. What's the adrenal medulla part of?
1. Epinephine, norepinephrine - these are called catecholamines and released by adrenal medulla. Aldosterone (mineralocorticoid) and cortisol (glucocorticoid) - both steorids released by cortex.
-Water soluble hormomes made by the medulla; cortex has lipid hormones - make and secrete steorid hormones - also regulated differently
-NE and E have same effect in cells;
Both norepinephrine and epinephrine are released from the adrenal medulla as hormones, but norepinephrine aloneis released from nerves as a neurotransmitter.
The main point of the slides is to differentiate between the two mechanisms, where generally speaking, NE acts as a neurotransmitter released by nerves, and epinephrine travels through the blood as a hormone to activate target cells.
2. Divided into two regions: inner medulla and outer cortex
3. The adrenal medulla is a part of the sympathethic nervous system
-hypo pituitary axis --> the inner medulla not under this axis (not regulated by this)
Yo memorise this
-Endocrine system acts in conjunction with the nervous system
-Medulla is part of sympathethic nervous
-Epi and NE travel and act on heart etc act on pacemaker
-the target organs are e.g. pacemaker cells
-That box = increases ability to fight or flight
So left side can't be sustained for too long so need right side
1. Epi is secreted as part of?
2. Increase in epi secretion supplements?
1. Epinephrine is secreted as part of the sympathetic nervous system’s response to stress.
2. Increase epinephrine secretion supplements the actions of direct sympathetic innervation of tissues, particularly in times of stress.
-The sympathetic target/effector cell = pacemaker
-finitie NE (right side)
-released in blood stream (epi)
-the sympathetic pre gang fibres fire at same time
-Key difference: the RHS is instantaneous whereas the RHS follows secs/mins later - sustained longer than others (as long as AP sent)
Memorise this too
1. What're other sympathetic nervous system actions? (4)
Other SNS actions:
• increase heart rate
• Increased blood pressure
• Expanding air passage of lungs
• Redistributing blood flow to muscles
-Skeletal muscle: also has glycogen stores
-Liver - increases glucogeneosis (enzymes breakdown glycogen into glucose)
-Both those at the end are same outcome but different mechanism
-Stress: even just thinking about runnning can activate these pathways - bc need glucose to run (body is preparing for the exercise)
Water soluble - can't enter via diffusion (acivates mem recep - a protein etc)
-that activates kinase which does something about response and then liver activates enzymes that'll breakdown glycogen
Right red - gene transcription etc
Right blue - backs up the response that's done by LHS
Both make same outcome but different approach
Stress activates neurons to release CRH
RHS - direct stimulation