HomeCells & MoleculesDiseasesEcosystemHuman BiologyAQA BIOL1AQA HBIO1AQA HBIO2AQA HBIO4AQA HBIO5
HBIO4 > Flight or Fight
Welcome, Guest!
Login with Facebook | Login

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