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Flight or Fight - Muscles, Hormones and Nerves working together

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Flight or Fight - anger or fear

Nervous System

Central nervous system (CNS)
- Brain
- Spinal cord
Peripheral nervous system
- Motor
  - Autonomic nervous system (involuntary)
    - Parasympathetic (cholinergic → acetylcholine) - inhibition/relaxation
    - Sympathetic (adrenergic → noradrenaline) - excitation/stress
  - Somatic nervous system (voluntary)
- Sensory

Autonomic nervous system

Effect on target organ	Parasympathetic (ACh)	Sympathetic (NA)
Iris of eyes	Constricts pupil	Dilates pupil
Bronchioles	Bronchoconstriction	Bronchodilation (↑air flow)
Blood vessels
Vascular smooth muscle		Vasoconstriction
Arterioles supplying skin and gut		Vasoconstriction (require less blood)
Arterioles supplying muscles		Vasodilation
Coronary arteries		Vasoconstriction
Heart	↓heart rate	↑heart rate
Salivary glands	↑secretion	↓secretion
Gut	↑peristalsis	↓peristalsis
Sweat glands	No effect	↑sweat production

Hypothalamus

Receives information from cerebral cortex
Passes on impulses to sympathetic nerve fibres
Sympathetic nerves synapse with target organ
Release noradrenaline (NA) into synaptic cleft

Adrenal medulla

Located just above the kidneys
Innervated by sympathetic nerves
Stimulation causes the release of adrenaline (ADR) into blood

Role of Hormones

Steroid hormones
- Lipid soluble
  - Diffuse though plasma membrane and bind to receptors in cytoplasm
  - Regulate transcription
- Cortisol → stress hormone, turns protein and fat into glucose
- Testosterone and oestrogen
Protein hormones
- Bind to plasma membrane
  - Causes cascade of signals
  - Activates enzymes within the cell
- Adrenaline (released from adrenal glands)
  - Increases sensitivity of nervous system
  - Stimulates release of cortisol
  - Stimulates glycogenolysis in liver and muscles
  - Note: ADR is a hormone while NA acts as a hormone and neurotransmitter
- Insulin
Hormone vs Nervous System
- Hormones
  - Produce delayed and prolonged responses
  - Travel throughout the body and produce widespread effects
  - May cause permanent and irreversible effects
- Nervous System
  - Instant response
  - Usually act locally
  - Temporary and reversible effects