Animal responses

• label

  A) Cerebrum

  B) hypothalamus

  C) Cerebellum

  D) Medulla oblongata

  E) posterior pituitary

  F) anterior pituitary

  
• knee-jerk reflex:

  stimulus: patellar tendon streches

  receptor: stretch receptors detect

  coordinator: sensory neurone -> motor neurone

  Effector: leg muscles

  Response: leg kicks

  fast response as there is only one synapse
• blinking reflex:

  stimulus: object hits cornea

  receptor: cornea receptors detect

  coordinator: sensory neurone -> relay neurone -> motor neurone

  effector: eyelid muscles

  response: eyelids close
• Fight or flight response:

  stimulus (threat) -> Receptor -> sensory neurone -> hypothalamus:

  activation of:

  
  

  Adrenal-cortical system:

  peptide hormone released by the hypothalamus and sent to the pituitary gland and stimulate the production of ACTH

  ACTH stimulates the cortex of the adrenal to produce useful chemicals to survive like cortisol which increases glucose production and use

  
  

  Sympathetic nervous system:

  SNS stimulates the medulla of the adrenal glands to produce adrenaline and noradrenaline which increases heart rate and stimulates glycogenolysis
• Action of adrenaline:(second messenger model)

  adrenaline binds onto the receptor of a liver cell which activates adenylate cyclase which converts ATP -> cAMP

  cAMP binds to and activates protein kinase which activates enzymes responsible for converting glycogen to glucose.

  So adrenaline stimulates glycogenolysis

  
  

  adrenaline is the first messenger

  cAMP is the 2nd messenger that causes the effect
• Autonomic Nervous System


  Self-controlling system that controls involuntary bodily functions
• Exercise

  Increases heart rate
• Medullaoblongata


  Region of the brain that plays a vital role in controlling the heart rate
• The medulla is found at the base of the brain near the top of the spinal cord
• Parts of the medulla

  • Acceleratory centre
  • Inhibitory centre
• Acceleratory centre


  Causes the heart to speed up
• Inhibitory centre


  Causes the heart to slow down
• Sinoatrial node (SAN)


  The heart's natural pacemaker
• Autonomic nervous system


  Nerves that control involuntary bodily functions, different from nerves that control conscious activities
• Acceleratory centre activation

  1. Impulses sent along sympathetic neurones to SAN

  2. Noradrenaline secreted at SAN synapse

  3. Noradrenaline causes SAN to increase electrical wave frequency

  4. Increased heart rate
• Inhibitory centre activation

  1. Impulses sent along parasympathetic neurones to SAN

  2. Acetylcholine secreted at SAN synapse

  3. Acetylcholine causes SAN to reduce electrical wave frequency

  4. Reduced heart rate
• Changes in carbon dioxide concentration and blood pressure are detected by chemoreceptors and baroreceptors
• Receptor activation

  1. Receptors release nerve impulses

  2. Lower frequency impulses activate inhibitory centre

  3. Higher frequency impulses activate acceleratory centre
• Adrenaline

  Hormone produced by adrenal glands, chemically similar to noradrenaline, released during fight-or-flight response
• Adrenaline release

  Causes increased heart rate
• Increased heart rate from adrenaline allows rapid increase in blood supply to respiring muscles</b>