Endocrine Response to Stress Flashcards
What is the structure of the Adrenal gland (from top to bottom)
Capsule
Zona glomerulosa
Zona fasciculata
Zona reticularis
Adrenal medulla
What does the Zona glomerulosa produce
Minercorticoids -> Aldosterone
What does the Zona fasciculata produce
Glucocorticoid -> Cortisol
What does the Zona reticularis produce
Sex steroids -> Androgens
What does the Adrenal Medulla produce
Catecholamines -> Adrenaline/Noradrenaline
What is Adrenaline synthesised from?
Tyrosine
What is the Catecholamine Biosynthetic Pathway?
What enzyme converts Tyrosine to L-dopa?
Tyrosine Hydroxylase
What cell is Adrenaline synthesised in?
Chromaffin cells of renal medulla
What are the steps of Adrenaline MoA?
- Adrenaline attaches to Adrenergic receptor -> activates G proteins
- G proteins -> promote adenylyl cyclase -> prod. cyclic AMP
- Cyclic AMP activates PKA
- PKA mediates fight/flight
Synthesis of Adrenal cortex steroids
Describe the steps of the Hypothalamic-Pituitary-Adrenal (HPA) axis
- Stress -> Parvocellular neuron releases CRH (cortico-trophin releasing hormone)
- CRH -> produces ACTH (a posterior pituitary hormone)
- ACTH binds to Adrenal cortex -> stimulates steroid hormone production -> increases activity of steroidogenic enzymes
- Cortisol feeds back to Hypothalamus -> suppresses ACTH and CRH production
Describe the cortisol MoA steps
- Cortisol binds to Cytosolic Glucocorticoid receptors
- Cortisol-receptor complexes -> bind to specific DNA sites (GRE)
- Alters expression of specific genes
- Proteins synth. in response to cortisol vary depending on the type of cell
How does cortisol travel in blood?
- bound to CBG
Cortisol metabolic actions
Does cortisol have antiinflammatory and immunosuppressive actions?
Yes
Does cortisol have anti-reproductive actions?
Yes -> decreases function of reproductive axis at hypothalamic, pituitary and gonadal levels
What is Addison’s Disease? and what are symptoms? what is the treatment? what is it usually caused by?
= Adrenal insufficiency
Symptoms:
- weakness
- fatigue
- loss of weight and appetite
- low BSL
- low BP (bc less aldosterone so upsets Na+/K+ balances in blood)
Treatment:
- oral administration of glucocorticoids and minerocorticoids
Causes:
- autoimmune disease
What can excess cortisol lead to?
Cushing’s syndrome
What is Cushing’s caused by? what effects can it cause?
Causes:
- Cortisol-secreting tumour in adrenal gland (primary)
- ACTH-secreting tumour of anterior pituitary (secondary)
Effects:
- bone strength dimishes
- muscles weaken
- fat on the face, back and belly
- weakened immune system
What are the 3 phases of the General Adaptation Syndrome
- Alarm reaction (6-48 hours)
- Resistance (>48 hours)
- Exhaustion (>1-3 months)
What are the characteristics and significance of the Alarm reaction stage?
Characteristics:
- stimulation of sympathetic adrenal medulla axis -> release of Adrenaline
Significance:
- fight/flight response
What are the characteristics and significance of the Resistance stage?
Characteristics:
- ACTH-glucocorticoids increased
- adrenaline decreased
Significance:
- adaptation to the given stressor increases but decreases to additional stressors
What are the characteristics and significance of the Exhaustion stage?
Characteristics:
- symptoms of alarm stage reemerge
- glucocorticoids still increased
Significance:
- depletion of resources brings on diseases and disorders
