CNS & PNS

• The Role of The Cranium

  protects the brain from physical blunt force trauma
• The Role of The Vertebral Column

  protects the spinal cord
• Meninges Protective Role

  • covers and protects CNS
  • protects blood vessels
  • contain CSF
• The 3 Layers of Meninges

  1. Dura Matter
  2. Arachnoid
  3. Pia Matter
• Dura Matter

  • outer layer
  • tough and fibrous
  • attached to bone
• Arachnoid

  • middle layer
  • loose mesh of fibre (subarachnoid space) that are filled with CSF
• Pia Matter

  • inner layer
  • delicate and highly vascular
  • follows tight convolutions of the brain
• Cerebrospinal Fluid Structure

  • clear, watery fluid
  • some cells
  • some glucose, protein, urea and salts
  • once produced moves freely through the cavities and in the central canal of spinal cord
• Cerebrospinal Fluid Function

  • Protection - acts as a shock absorber
  • Support - brain is suspended inside the cranium and floats in the CSF
  • Transport - during its circulation it takes nutrients to the cells of the brain and spinal cord and carries away their wastes
• The Cerebrum

  • two hemisphere - left and right
  • outer layer of grey matter called cerebral cortex
  • middle layer of white matter
  • inner layer of grey matter called basal ganglia
• Major Lobs In Hemisphere

  • Frontal
  • Temporal
  • Occipital
  • Parietal
• Frontal Lobe


  Conscious thought

  • personality
  • motor skills
• Temporal Lobe

  • hearing and smell
  • language
  • memory
• Occipital


  vision
• Parietal


  Processing Senses

  • touch
  • pressure
  • pain from skin
• Cerebellum

  • lies under rear part of cerebrum
  • surface folded into parallel ridges
  • outer folded part - grey matter
  • inner - white matter
• Cerebellum Function

  • control over posture and balance
  • fine motor control - coordination of voluntary muscles, ensure smooth coordinated movement
• Cerebellum Receives Sensory Information From

  • eyes - position of body
  • inner ear - posture and balance
  • stretch receptors - skeletal muscles and joints
  • Receives motor information from cerebral cotex
• Hypothalamus

  To maintain constant internal environment

  • control the automatic nervous system
  • initiate physical responses to emotion
  • regulate body temperature
  • regulate food intake
  • regulate water balance and thirst
  • regulate sleep-wake cycles
  • control endocrine system functions
• Hypothalamus Controls Body Functions In 2 Main Ways

  • Nervous via medulla oblongata
  • Endocrine via pituitary gland
• Medulla Oblongata

  1. lowest part of the brain
  2. continuation of the spinal cord
• Medulla Oblongata Functions

  Automatic Reflex Centre To Help Maintain Homeostasis

  • Cardiac centre - heart beat
  • Respiratory centre - breathing
  • Vasomotor centre - diameter of blood vessel
  • Various other centres -sneezing, swallowing, coughing, vomiting
• Spinal Cord


  Myelinated fibres in the white matter arranged in bundles

  • Ascending Tracts - sensory axons the carry impulse towards the brain
  • Descending Tracts - motor axons that carry impulses from the brain
• Spinal Cord Functions

  • integrate certain reflexes (spinal reflexes)
  • pathway of communication between the brain and the muscles and glands
• Peripheral Nervous System Includes

  • 24 cranial nerves
  • 62 spinal nerves
• Peripheral Nervous System Composes of

  • nerve fibres that carry information to and from the CNS
  • group of nerve cell bodies, called ganglia, which lie outside the brain and spinal cord
• Sensory fibres carry impulses into the CNS
• Motor fibres carry impulses away from the CNS
• Ventral roots contain the axons of motor neurons that have their cell bodies in the grey matter of the spinal cord
• dorsal root contains axons of sensory neurons that have their cell bodies in a small swelling on the dorsal root know as the dorsal root ganglion
• Afferent Division

  • has fibres that carry impulses into the CNS by sensory neurons from receptors in the skin and around the muscles and joints
• The Afferent Division Can Be Further Divided Into

  • somatic sensory neurons - impulses from skin and muscle
  • visceral sensory neurons - impulses from internal organs
• Efferent Division

  • fibres carry impulse away from the CNS
• Efferent Division Can Be Divided Into

  • somatic division - impulse from CNS to skeletal muscle
  • automatic division - impulse from the CNS to heart, muscle, involuntary muscles and glands
• Autonomic Division Can be Further Divided Into

  • sympathetic division - fight or flight
  • Parasympathetic division - rest and digest
• Autonomic Nervous System

  • controls the body's internal environment and is involved in many of the mechanisms that keep it constant
  • regulates automatic body functions
• Autonomic Functions Have Their Control Centres In

  • hypothalamus
  • medulla oblongata
  • cerebral cortex
• Functions Controlled By The Autonomic Nervous System

  • heart rate
  • blood pressure
  • body temperature
  • pupil diametre
  • digestion
  • urination
• Autonomic pathway has two motor neurons involved in carrying impulses from the CNS to the effector
• Somatic pathway has one motor neuron carrying impulses from the CNS to effector