Central nervous system | CNS anatomy

Central nervous system anatomy

Central nervous system consists of brain and spinal cord. Cranial nerves which originates from brain and supply the body. Peripheral nerves originates from spinal cord and spread throughout the body. These nerves supply each single, organ and viscera. Any damage to the part of brain or spinal cord will disrupt the blood supply or function of the organ or viscera which was being supplied by this particular damaged part of Central nervous system. Brain is covered by three layers called meninges, dura mater, arachnoid mater and pia mater. Cerebrospinal fluid is present in arachnoid mater. If due to the rupture of blood vessel blood enters into subarachnoid space, patient experiences a severe head ache called subarachnoid hemorrhage.

Symptoms of Neurological problem:

  • Headache (migraine, cluster headache, meningitis, increased intracranial pressure, subarachnoid hemorrhage, brain tumor)
  • Fits (Focal, generalized, repeated epilepsy, hypoglycemia, hypocalcemia, electrolyte imbalance, uremic fits, ischemic fits)
  • Loss of consciousness (coma, head injury)
  • Loss of memory (dementia, amnesia)
  • Motor weakness (hemiplegic, monoplegia, diplegic, quadriplegic)
  • Sensory weakness (loss of sensations)
  • Gait and balance disturbance (Problem in cerebellum)
  • Speech problem (dysphasia, dysphonia also called hoarseness of voice, dysarthria)

Examination of neurological problem:

Higher mental functions: Check for orientation of time, place and person. Like in dementia patients this orientation is absent. Then observe speech and mental intelligence.

Motor system examination: Examine the muscles of both upper and lower limb. Starting from pelvic region test flexors, extensors, abductors, adductors at pelvic, knee and ankle joint. Then examine the upper limb starting from shoulder, elbow and then wrist joint. Examine all muscles and joints against resistance.

Sensory system examination: Check sensations by pricking at dermatomes. There are two types of touch sensations. Fine touch and crude touch. Fine touch is carried through dorsal column medial lemniscal system. The track which carries the sensation of pain and crude touch from body to CNS is called anterolateral system. Fine touch is tested through cotton and for crude touch prick on patient’s dermatome. To check temperature sensation Thermosensor can used. One end of thermosensor is cold and the other one is hot. Check both sensations for cold and hot.

Cerebellar examination: Examine the cranial nerves which originates from brain and supplies the body. Cranial nerves are twelve in number. Peripheral nerves originates from spinal cord and supply whole body.

Cranial nervesPeripheral nerves
(foot drop)
(knee extension)
(Eye movement)
Femoral cutaneous
(sensations to thigh)
(Eye movement)
(sensation to foot)
(facial sensation)
Spinal accessory
(carry sensations)
(eye movement)
(Sensation at foot sole)
(facial movement)
(arm extension)
(hearing & balance)
(innervation to hand,
wrist, forearm)
(carry sensory information)
(hand movements)
(shoulder shrug)
(cutaneous innervation
of forearm)
(tongue movement)

Brain death:

There are three crucial systems, respiratory system, Central nervous system (responsible for wakefulness, sleeping, balance, memory, eating) and cardiovascular system (responsible for pumping blood to whole body). These three systems are responsible for making a person alive. In case of complete brain damage a person is having respiratory problems, ventilators are present to provide him with oxygen artificially. In case of cardiac injuries chronotropic, ionotropic medications along with pacemakers to stimulate heart. Brain dead patients means, a patient with complete brain damage he is unable to move, but ventilator and pacemakers are providing strength to keep him alive. The patient may even survive for ten years in brain dead position. Turning off ventilator or removing pacemakers will ultimately cause death.

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