Anatomy and Physiology of brain

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Anatomy and Physiology of brain
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Brain cells

• Neurons and neuroglia

neuroglia neuroglia
In CNS In PNS
Asrocytes Schwann cells
Oligodendrocytes Satellite cells
Microglia
Ependymal cells
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Neuron

• Basic units of nervous tissue
• Function as electrical impulse generation and
  transmission.
• Cannot regenerate when damaged

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Neuroglia/Glial cells

• Makes half of the volume of CNS
• Smaller than neurons and 5-50 times more numerous
  than neurons.
• Do not propagate nerve impulses
• Can regain after injury, highly growing.

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Astrocytes

• Star shaped cells, have many processes, largest
  and most numerous
• Two types of astrocytes-protoplasmic and fibrous
• Processes of astrocytes make contact with blood
  capillaries, pia matter and neurons.

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Functions of astrocytes

• strength to support neurons.
• blood brain barrier.
• growth and interconnection of neurons.
• chemical environment for generation of nerve
  impulses by neurons.
• learning and memory

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Oligodendrocytes

• These resemble astrocytes but have fewer
  processes and smaller in size.
• Maintain myelin sheath around the CNS axons.
• A single oligodendrocyte may myelinate several
  neurons.

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Microglia

• Small in size, contains spindle like projections
• Function as phagocytes and clear cell debris

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Ependymal cells

• Cuboidal to columnar cells contain cillia and
  microvilli.
• Lines the ventricals of brain and central canal
  of spinal cord.
• Produce, monitor and assist in CSF circulation.
• Form blood cerebrospinal fluid barrior.

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Schwann cells

• Form myelin sheath around the neurons.
• Single cell can line only one axon.
• Participate in axon regeneration.

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Satellite cells

• Surrounds the cell bodies of neurons in PNS
  ganglia.
• Exchange of materials between neuronal cell
  bodies and interstitial fluid.

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Meninges
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CSF circulation
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C S F C I R C U L A T I O N
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CSF composition

• Normal CSF secretion is 20 ml/hr or 480 ml/day
• Total volume is 80-150 ml
• Carries oxygen and nutrients
• Contains glucose, protein, lactic acid, urea,
  cations ( Na, K, Ca2, Mg2) and anions (Cl,
  HCO3-)
• Functions are mechanical support, chemical and
  nutritional.

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Brain stem

• Consists of 3 parts
• Medulla ablongata
• Pons
• Mid brain

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Medulla ablongata

• contains sensory and motor tracts extends between
  the brain and spinal cord.
• Contains cardiovascular centre
• Medullary rythmicity area of respiratory centre
• Responsible for vomiting, coughing, sneezing,
  swallowing and hiccupping.
• Sensitive to touch, vibration and proprioception.

• Contains 5 pairs of cranial nerves
• Vestibulocochlear VIII
• Glossopharyngeal IX
• Vagus X
• Accessory XI
• Hypoglossal XII
• Damage to this part cause cranial nerve
  alterations at the same side and paralysis in
  opposite side.

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Pons

• contains pneumotaxic area and apneustic area
  which helps in respiration.
• Have 4 pairs of cranial nerves
• Trigeminal V
• Abducens VI
• Facial VII
• Vestibulocochlear VIII

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Mid brain

• connects cerebrum to medulla, pons and spinal
  cord.
• Reflex centre for visual activities
• Helps in tracking moving objects
• Helps in scanning stationary objects
• Eyes, head and neck movements with moving objects
• Startle reflex
• Sudden movement of head with noise
• Have substantia nigra which release dopamine and
  also responsible for subconscious muscle
  activities.

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RAS- reticular activating system

• brain stem consists of small clusters of neuronal
  cell bodies.
• It maintains consciousness
• Awakening from sleep
• Muscle tone maintenance

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cerebellum

• Skilled skeletal muscle movements
• Posture and balance
• Cognition and language processing