Endocring Fucking 4 Flashcards
Cortisol - how it causes a cellular response
- produces as required
- carried in blood bound to a carrier protein (corticosteroid-binding globulin)
- travels to target cell and passes through the membrane
- binds to a specific receptor
- moves into nucleus
- activates genes
- mRNA is produced
- protein produces
- protein has an effect
- SLOWEST HORMONE TO GIVE A CELLULAR RESPONSE
Events that lead to the release of cortisol
Two stimuluses:
- stress
- low blood glucose / day-night rhythm
Hypothalamus intergrates stimuluses and decides if response is needed…..
- …..if the corticotropin releasing hormone reach threshold at axon hillock (idk if u need to worry about this - lecturer said it - i think it just means like the initial neural signal on top of portable blood vessels thing)
….. then corticotropin releasing hormone is releases into the portable blood vesssels and travels to anterior pituitary and causes the cells with the correct receptors to secrete adrenocorticotrophic hormone (ACTH)
ACTH goes through systemic system and it will cause the adrenal cortex (outer region or adrenal gland) to synthesise and secrete cotisol (because its a steroid and lipid soluble it can’t be stored)
Metabolic effects of cortisol
Metabolic effects
Muscle:
- increase in protein breakdown
- decrease in glucose uptake
Liver:
- increase in glucose synthesis
Fat:
- increase in fat breakdown
- decrease in glucose uptake
Other effects of cortisol
- helps one to cope with stress
- long-term: suppresses immune system
- essential for maintaining normal blood pressure
How does cortisol cause cellular responses
- at target cells cortisol binds to receptors in the cytoplasm and activates gene transcription
Daily pattern of cortisol secretion
- highest peaks upon waking up
- disturbances of normal sleeping patterns will affect this pathway
Cortisol function
Effects many different body systems in response to stress including:
- increasing blood glucose levels
- increasing fat, protein and carbohydrate metabolism to maintain blood glucose
- promoting anti-inflammatory actions
- increasing blood pressure
- increasing heart and blood vessel tone and contraction
- activation of the CNS
Name for problems of hormone levels
Hyposecretion: too little (or none)
Hypersecretion: too much
Name for problems with hormone receptors
- hyposensitive: little (or no) response
- hypersesitive: respond too much
Problems with hormone signalling are caused by:
- autoimmunity: destruction of receptors
- genetic mutation: mutations can cause gain to loss of function
- tumours: excess tissue usually leads to excess hormone release, but can sometimes prevent release
Events that lead to cortisol releases being inhibited
- cortisol secretion is controlled mainly by negative feedback (except during the stress response)
- cortisol production inhibits the release of ACTH and CRH
Addisons disease
- lowered secretion of both cortisol and aldosterone
- low cortisol concentration leads to an increase in ACTH secretion
- excess ACTH stimulates melanin synthesis - darker skin
HYPOSCRETION
AUTOIMMUINITY - caused by destruction of receptors
Other symptoms:
- low blood pressure
- weakness (lack of fuel)
Coushings diesease
HYPERSECRETION: too much
Caused by tumors: excess tissue usually leads to excess hormone release
- tumor in adreneal cortex leading to an increase in cortisol release
Symptoms:
- buffalo hump (accumulation of fat behind the neck)
- moon face
- high blood pressure
- weakness (muscle wasting) - breakdown of muscle and fat resulting in a redistribution of body fat (hence moon face and lump)
What happens when stress arises (in hypothalamus)
Stress stimulus (can be internal or external)
- activated the hypothalamus
- hypothalamus organises a response and activated the:
- adrenal glans
- sypathetic nervous system
- posterior lope of the pituitary gland
- body responds
Alarm phase - what are the common visceral reflexes?
Increased Sympathetic stimulation
Cardioaccelertory reflex - increase in heart rate and force of contraction
Vasomotor reflexes - changes in diameter of peripheral vessels
Pupillary light reflex - changes in pupil diameter
What causes Immediate short term responses in the altert phase
General sympathetic activaation as well as epineriphe and norepinephrine secretion from the adrenal medulla
