L-28 Flashcards
What is cortisol?
Steroid hormone produced in the adrenal cortex released in response to stress, day/night rhythms, or low blood glucose
When is cortisol produced
Produced as required when signalled by the hypothalamus and pituitary
What is the process from secretion to effect of cortisol?
- carried in the blood bound to a carrier protein (corticosteroid-binding globulin) to target cell
- disassociates from carrier protein and diffuses through membrane
- binds to receptor in the cytoplasm
- Complex formed moves into the nucleus and binds to DNA causing the activation of specific genes
- mRNA transcription and translation occurs and a new protein is synthesised
Is cortisol fast or slow acting?
Slow acting
What are the steps of the cortisol secretion sequence?
- stress/ daynight rhythms/ blood glucose concentration stimulates hypothalamus to secrete corticotropin releasing hormone (CRH)
- this stimulates anterior pituitary to secrete adrenocorticotropic hormone (ACTH)
- this stimulates the adrenal cortex to secrete cortisol
What are the effects of cortisol secretion?
- increased protein breakdown and decreased glucose uptake in muscle
- increased fat breakdown and decreased glucose uptake in fat
- increased glucose synthesis in the liver
- helps to cope with stress
- long term suppresses the immune system
- essential for blood pressure maintainence
What are trends in the daily pattern of cortisol secretion? What can effect these?
- pulses during the day in response to specific body conditions and stresses
- highest peak is upon waking
- affected by disturbances to normal sleep patterns ( little sleep, jet lag, night shifts)
What are the functions of cortisol? (5)
- increasing fat, protein, and carbohydrate metabolism to increase blood glucose concentration
- promoting anti-inflammatory actions
- increasing blood pressure
- increasing heart and blood vessel tone and contraction
- activation of the CNS
How is cortisol secretion homeostasis controlled?
Through negative feedback from intermediate products except in times of stress
What are potential problems with hormone signalling?
Hyposecretion- to little hormone secretion
Hypersecretion- to much hormone secretion
Hyposensitive- little (or no) response from receptors
Hypersensitive- too much response from receptors
What can problems with hormone signalling be cause by?
- autoimmmunity- destruction or receptors or artificial stimulation of receptors
- genetic mutation- can cause gain or loss of function
- tumors- excess tissue leads to excess hormone release, can rarely lead to prevention of release
- other- many other factors can disrupt hormone signalling
What is Addison’s disease caused by?
What are the symptoms?
- hyposecretion of cortisol and aldosterone caused by destruction of receptor due to autoimmunity
- low cortisol concentration leads to repeated signalling of anterior pituitary to release ACTH
- excess ACTH simulates melanin synthesis, low blood pressure and weakness
What is Cushing disease cause by? What are the symptoms?
- hypersecretion or cortisol due to tumors
- high cortisol leads to high blood pressure, weakness due to muscle wasting, and weight gain in unusual places
What are the phases of the stress response?
- Alarm
- Resistance
- Echaustion
Explain the alarm phase of the stress response:
- fight or flight immediate short term response
- adrenaline secretion causes short term sympathetic nervous system response
Explain the resistance phase of the stress response
- occurs if still receiving stimulus after a few hours
- ADH and cortisol have their effects
- remaining energy reserves are mobilised
- glucose is conserved
- increased blood glucose concentration
Explain the exhaustion phase of the stress response:
- occurs after weeks or months of continual stress
- can lead to heart attacks and death
Explain the integrated stress response
- stimulus is tress
- hypothalamus secretes corticotropin releasing hormone (CRH)
- this stimulates action potentials to travel down the sympathetic preganglionic neuron to the adrenal medulla, the anterior pituitary to release adrenocorticotropic hormone (ACTH), and the posterior pituitary to secrete ADH
- The adrenal medulla secretes adrenaline, the adrenal cortex secretes cortisol, and the ADH travels to the receptors
- blood glucose increases, blood pressure increases, heart rate increases (adrenaline), water excretion decreases (ADH), blood volume increases (ADH)
