functional anatomy of the nervous system

CNS

• grey matter- nerve cell bodies

• white matter- nerve cell processes (acons) and their insulating myelin sheaths

• forebrain composed of cerebrum, thalamus, hypothalamus, limbic system

• midbrain

• hindbrain composed of cerebellum, pons, medulla

PNS

• made of cranial and spinal nerves

• cranial connect to the brain

• spinal connect to the spinal ord

• all nerves are bilateral and symmetrical

• 12 pairs of cranial nerves

protection of the cns

shielded by the cranium, verterbrae, meninges between the bony casing and CNS.

afferent system

nerves that transmit impulses towards the brain and SC

joints/skin/skeletal muscle ➜ somatosensory fibers ➜ CNS

viscera/vessels ➜ viscerosensory fibers ➜ CNS

efferent system

nerves that transmit impulses away from brain and SC

CNS ➜ somatomotor fibers ➜ skeletal muscle

CNS ➜ visceromotor fibers ➜ glands/smooth muscle/cardiac muscle

neuron structure

• cell body (soma)

• dendrites- conduct impulses to the cell body

• axon or neuron fibre- relays impulses to other neurons. each neuron has only one axon

myelination

• pns- schwann cells

• cns- oligodendrocytes

• eg in MS oligodendrocytes are desroyed, Schwann are not

• saltatory conduction

different types of neurones

• unipolar- cell body connects to axon

• bipolar- dendrites arborizes in periphery

• pseudounipolar- dendrites and axon not separated by cell body

• multipolar- multiple dendrites with long axon

what are neuroglia cells

cells that surround neurons providing them with structural and functional support and absorb excess neurotransmitters

capable of mitotic activity- brain tumours

blood supply to nervous system

• heart through carotid arteries

• species variation

• but in all blood is pooled into cerebral artery before distribution to the brain

where does CFS come from

• cavities within cns called ventricles

• have ependymal cells that secrete csf from capillaries network (choroid plexus)

• csf made through ultrafiltration of blood

• contains glucose, minerals providing nutrition support and shock protection to the cns

• abnormal accumulation cause hydrocephalus- put excess pressure causing damage