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Animal Responses (The Mammalian Nervous System (Central Nervous System…

- - - - Mostly non-myelinated relay neurones - grey matter
    - - Non-myelinated neurones in the centre
      - Myelinated nurones in the outer reigon - white matter
  - - - Somatic
        
        Usually mylinated
        
        One neurone connects the CNS and the effector
      - Autonomic
        
        Sympathetic
        
        Prepares body for activity
        
        Slows down digestive system
        
        Noradrenaline
        
        Parasympathetic
        
        Conserves energy
        
        Increases digestive activity
        
        Acetylcholine
        
        Usually non-myelinated
        
        Multiple neurones connect the CNS and the effector, the neurones connected at small swellings called ganglia
- - - - Controls homeostatic mechanisms, has sensory receptors and controls negative feedback
    - - Hormones made in the hypothalamus pass down neurosecretory cells in the posterior lobe and are released into the blood (e.g. ADH)
      - The anterior lobe produces its own tropic hormones in response to releasing factors from the hypothalamus, controlling various physiological processes (e.g. responding to stress + growth)
- - - - Overriding Reflex Actions
        
        The brain can then send action potentials down myelinated inhibitory neurones faster than the non-myelinated relay neurones in the pons
        
        The sensory neurone involved passes action potentials to the pons as well where myelinated neurones tell the cerebral cortex a stimulus has been detected.
      - The sensory neuron enters the pons, connects to a relay neurone and then connects to the motor neurone
    - - Protects light-sensitive cells in the retina
      - Is mediated by the optical centre and is slower than the corneal reflex
- - - - Rapid response
      - The hypothalamus increases sympathetic nervous system activity
      - The adrenal medulla is activated and releases adrenaline
      - It also activates glands and smooth muscle
    - - Prolonged response
      - Hypothalamus sends releasing factors/hormones to stimulate anterior pituitary gland
      - TSH is released from pituitory gland
      - ACTH is released from the pituitory gland
      - Thyroid gland secretes thyroxine
      - Adrenal cortex secretes corticoid hormones
  - - - Adrenaline (a primary messenger) binds to receptor on plasma membrane
      - A G-Protein is activates the enzyme adenyl cyclase
      - Adenyl cyclase converts ATP to cyclic AMP (a secondary messenger)
      - cAMP causes a cascade of enzyme action depending on the cell
    - - Adrenocorticotropic hormone (ACTH) stimulates the adrenal cortex to release corticosteroid hormones. Glucocorticoids (e.g. cortisol) regulate metabolism of carbohydrates, more glucose is released
    - - Thyroid-stimulating hormones (TSH), stimulates the thyroid gland to release thyroxine, acting on nearly every cell, increasing metabolic rate and increased sensitivity to adrenaline