Nervous system

Nervous system

1. Functions

   • Sensory input
   • Integration
   • Homeostasis
   • Mental Activity
   • Control of skeletal muscle

2. Central Nervous System

   • Brain and spinal cord

3. Peripheral Nervous System

   • 31 pairs of spinal nerves and all neural tissue outside of CNS
     • 12 Thoratic nerves
     • 5 Lumbar nerves
     • 1 coccygeal nerve
     • 5 sacral nerves
     • 8 cervical nerves
   • 12 pairs of cranial nerves
   • Afferent division
     • Sensory info to CNS via ascending pathway
   • Efferent division
     • Motor info to glands and muscles via descending pathway
     • Somatic nervous system
       • Skeletal muscle
     • Autonomic muscle system
       • Smooth muscle, Cardiac muscle, Glands
       • Sympathetic
         • Ganglion close to CNS
       • Parasympathetic
         • Ganglion close to organ

4. Cellular organisation in neural tissues

   • Neurons
     • Communication
     • Large, prominent centrally located nucleus, lot of mitochondria, lot of Nissl bodies (RER) for neurotransmitter production
     • Axons
       • Long cell process
       • Single structure or branch= collateral axons
       • Carry impulse away from body
     • Dendrites
       • Short, highly branching cytoplasmic extenstion
       • Sensory messengers to be processed
     • Cytoskeleton
       • neurofilament- architecture
       • Microtubules - axinal transport
     • Synaptic terminals
       • Synapse communication with other cell
   • Neuroglia
     • Support, Defence and Myelination (insulation)
     • Oligodendrocytes
       • Myelination in CNS
     • Astroglia
       • White matter - fibrous astrocyte
       • Grey matter protoplasmic astrocyte
     • Microglia
       • Phagocyte in CNS
     • Ependymal cells
       • Cubodial or low columnar lining in central spinal canal, no basement membrane, lining ventricles in cerebrum rest on basement membrane and secrete cerebral spinal fluid
     • Schwann cells
       • Myelination in PNS
       • Support non-myellinated axons which bury themselves into the schwann cell cytoplasm

5. Functional classifications

   • Sensory
     • Unipolar - single neuron process from cell body
   • Interneurons
     • Bipolar neuron - 1 dendrite, 1 axon
   • Motor
     • Multipolar- single axon, many dendrites

6. Spinal reflexes

   • Stimulus Receptor Sensory neuron Motor neuron Effectors Response
   • No interneuron in reflex arc of knee jerk

7. Myelin

   • Spiral of membrane wrapped around axon
   • Increase speed of conduction along axon
   • Space between small units = nodes of Ranvier
   • Multiple sclerosis, myelin of CNS attacked by immune system, destruction results in severe functional deficits, such as paralysis, loss of sensation and/ or loss of coordination