Animal Physiology - The nervous system

• neural tissue = primary tissue
• tissues:

  • epithelial = covers surface of the body, line body cavities, form glands
  • connective = supports and bind other tissues together and includes blood constituents
  • muscle = contraction
  • neural = conducts impulses
• Homeostatic circuit:

  1. sensor
  2. error detector
  3. controller
  4. effector
  5. controlled variable
  6. regulated variable
• functional nervous system:

  1. receptors - detect change in internal and external environment
  2. sensory division of the Peripheral Nervous System - carries info to CNS from receptor
  3. information processing
  4. motor division of Peripheral Nervous System
  5. ANS + somatic nervous system
  6. effector - target organs
• Sympathetic nervous system

  most active during periods of stress or physical activity
• parasympathetic nervous system

  most active during periods of rest
• parasympathetic + sympathetic nervous system:

  antagonistic = one stimulatory other inhibitory
• effector organ = pupil

  parasympathetic stimulation = constricts

  sympathetic stimulation = dilates
• effector organ = lacrimal gland of eye

  parasympathetic stimulation = secretion

  sympathetic stimulation = none
• effector organ = salivary gland

  parasympathetic stimulation = watery secretion

  sympathetic stimulation = thick secretion
• effector organ = heart

  parasympathetic stimulation = slows heart rate

  sympathetic stimulation = increase heart rate
• effector organ = arterioles

  parasympathetic stimulation = none

  sympathetic stimulation = constricts
• effector organ = nasal gland

  parasympathetic stimulation = secretion

  sympathetic stimulation = none
• effector organ = bronchioles of lungs

  parasympathetic stimulation = constricts

  sympathetic stimulation = dilates
• effector organ = digestive tract

  parasympathetic stimulation = increased motility + secretion

  sympathetic stimulation = decreased motility and secretion
• effector organ = exocrine pancreas

  parasympathetic stimulation = increase enzyme secretion

  sympathetic stimulation = decrease enzyme secretion
• effector organ = endocrine pancreas

  parasympathetic stimulation = stimulates insulin secretion

  sympathetic stimulation = inhibits insulin secretions
• effector organ = male sex organ

  parasympathetic stimulation = erection

  sympathetic stimulation ejaculation
• Neuron structure:

  • dendrites = stimulated by environmental change
  • cell body = contain nucleus, mitochondria, ribosomes,
  • axon = conducts nerve impulses
  • terminal boutons = affect another neuron or effector organ
  • dendritic spines
• afferent = input

  efferent = output
• functional regions of neurons:input zone

  input zone = where neurons collect information - from environment or cells
• functional regions of neurons:integration zone

  integration zone = decision to produce neural signal is made
• functional regions of neuron: conduction zone

  conduction zone = information can be transmitted over distances
• functional regions of neurons

  output zone = neuron transfers information to other cells
• the synapse = specialised site where neuron communicates with another cell
• the synapse; involves two cells:

  1. presynaptic cell = sends message
  2. postsynaptic cell = receives message
• the synapse:

  1. action potential
  2. voltage gates calcium ion channel open
  3. calcium in
  4. synaptic vesicles move to synaptic terminal via axoplasmic transport
  5. attaches to doxing protein
  6. neurotransmitter released
  7. binds to receptor on post synaptic membrane
• types of synapses:

  • synapses with another neuron
  • neuromuscular junction
  • neuroglandular synapse
• Neuroglia in the CNS:

  ependymal cells: line central canal of spinal cord and brain ventricles, help to circulate, produce and monitor cerebrospinal fluid (CSF)
• neuroglia in the CNS:

  oligodendrocytes = myelinate axons from CNS and provide structural support
• neuroglia in CNS:


  astrocytes = maintain blood - brain barrier, provide structural support, regulate ions and nutrients, recycle neurotransmitters, form scar tissue after injury
• neuroglia in the CNS:


  Microglia = remove cell debris, wastes, and pathogens by phagocytosis
• Neuroglia in the PNS

  • satellite cells = surround cell bodies of neurons, regulate oxygen, carbon dioxide, nutrients and neurotransmitter levels around neurons
  • schwann cells = surround all axons, responsible for myelination of peripheral axons and repair processes
• Cerebrospinal fluid (CSF)

  • clear, colourless salty liquid
  • secreted by the choroid plexus
  • bathes external surfaces of brain and spinal cord
  • cushions and supports the brain by bouyance
• cerebrospinal fluid (CSF)


  contains very little protein and no blood cell s
• blood brain barrier

  • barrier between interstitial fluid and blood
  • isolates main control centre from harmful substances in blood and pathogens
• Brain is protected by blood-brain barrier, cerebrospinal fluid, and meninges
• Nerves = bundle of axons, neurons and connective tisue
• types of nerves:

  • cranial nerves = connected to brain
  • spinal nerves = connected to spinal cords
• number of spinal nerves depends on species:

  • dogs = 36 pairs
  • cats = 36 pairs
  • horse = 42 pairs