Neurology

• Central Nervous System is made up of brain & spinal cord.
• Peripheral Nervous System made of 43 nerves that come from CNS
• Neurons:

  1. Cell body: has a nucleus with nucleolus, dendrites, and axon
  2. Dendrites: transmit impulses to neuron cell bodies
  3. Axons: transmit impulses away from cell bodies
  4. CNS: surrounded by supportive & protective sheaths (unmyelinated axons)
  5. PNS: surrounded by Schwann cells (myelinated axons)
• Gray matter: collection of nerve cells - site of integration within the nervous system
• Types of Neurons:

  1. Sensory: transmit impulses to spinal cord & brain from all parts of body - afferent neurons
  2. Motor: transmit impulses away from spinal cord & brain - go to muscle & epithelial tissues - efferent neurons
  3. Interneurons: conduct impulses from sensory to motor - central/connecting neurons
• Synapse: the gap between neurones that allows the transmission of nerve impulses

  Made of:

  1. Presynaptic terminal (axons endings of one neuron)
  2. Synaptic cleft
  3. Plasma membrane of postsynaptic neuron (dendtrites of another neuron)
• AP starts a series of events in the presynaptic terminal that causes a neurotransmitter to be released - it then diffuses across synaptic cleft & bind specific receptor molecules on postsynaptic membrane. After impulse is generated & conduction by postsynaptic neurons start - neurotransmitter activity stops.
• Reflexes: rapid, automatic responses to stimuli that do not involve the conscious part of the brain - allow unidirectional conduction of impulses.
• Relex Components:

  • Sensory receptor
  • Sensory neuron
  • Interneurons
  • Motor neuron
  • Effector organ
• Arterial blood supply to brain comes from the vertebral & internal carotid arteries.

  • Left & right vertebral arteries - supplies cerebellum, pons - supply posterior portion of cerebrum
  • Internal give rise to anterior cerebral arteries that supply frontal lobes - supply large portion of lateral cerebral cortex
• The circle of Willis is a network of arteries that ensures the supply of blood to all parts of the brain in event of vertebral or internal arteries blockage
• Lateral ventricles: a large space of the brain that contains cerebrospinal fluid
• 1. Brainstem
  2. Medulla
  3. Pons
  4. Midbrain
  5. Site of the reticular formation
  6. Cerebellum
  7. Diencephalon
  8. Cerebrum
• Cerebral blood flow (CBF) depends on cerebral perfusion pressure (CPP) - the pressure gradient across brain

  • CPP = mean arterial pressure (MAP) - ICP
  • CPP is between 50 & 160mmHg; if below 30mmHg - blood flow declines
  • If MAP inc. cerebral blood vessels constrict & prevents an inc. in blood volume & CPF
  • If MAP dec. cerebral blood vessels dilate & inc. CBF
  • ICP inc. (more than 22mHg) perfusion of brain tissue dec.