Essay 5 - Functions of the Nervous System – functional morphology. Physiology of the nerve cell. Glia. Neuronal circuits and processing of information by groups of neurons – convergence, divergence, reverberating circuits, inhibition.

sections

what is nervous system

responsibility of nervous system

main parts of nervous system

divisions of pns

physiology of nerve cells

what are gilial cells

function of gilial cells

processing

what is nervous system

Nervous system - complex collection of nerves and specialized cells called neurons, glial cells ,brain and spinal cord.

• Concerned with reception of stimuli

• processing information

• control of function of internal organs and systems

• Transmit signals between different parts of the body.

responsibility of nervous system

• auditory and visual responses

• coordination and control of reflexes

main parts of nervous system

• CNS - consisting of the brain and spinal cord

• PNS - made up of ganglion (collection of nerve cell bodies), sensory neurones are nerves that connect to one another and to the CNS.

divisions of pns

1. Autonomic nervous system (involuntary) → Parasymp- rest and digest, sympathetic- fight controls many body processes, e.g.

   • blood pressure

   • breathing rate

   • these are all under unconscious control.

1. Somatic nervous system: (voluntary)

   • consists of nerves (sensory and motor nerves) that connect the brain and spinal cord with muscles and sensory receptors in the skin.

   • involved in voluntary movement and muscle movement.

physiology of nerve cells

• Nerves respond to stimuli eg. light and communicate information and conduct impulses which can be transmitted

• In myelinated neurons, -impulse moves faster

• impulses travel from one neurone to another by crossing a synapse.

• The message is converted from electrical → chemical → electrical again.

1. Sensory neurones transmit impulses from their receptors to the CNS where the information is processed.

2. Motor neurones transmit impulses from CNS to muscles. They are synonymous with efferent nerves

3. Interneurons- connect sensory neurons

what are gilial cells

They are used for support, protection, nourishment of the nerve cell: astrocytes- bbb, schwann—satellite- nutrition, oligo support, ependymal-CSF, microglia- immune defense

function of gilial cells

1. surround neurones- holding them in place

2. Provide insulation from one neurone to another

3. Provide nutrients such as oxygen

4. Destroy pathogens and remove dead neurons.

5. Myelin formation

processing

• Convergence- when one part of the synaptic neurone receives input from many different nerve fibres

• Divergence- when a neurone communicates with many other neurones in a network

• Reverberating circuits- chain made up of neurons, each neuron is linked by collateral synapses.—uses positive feedback to prolong signal

• Inhibitory circuits- inhibit input neurons or intermediate neurons when sensory neurons are over excited – slows down excitation