7 Oct 2015

Nervous system Anatomy

Nervous system Is very much important in controlling all the voluntary and involuntary actions of all parts of the body. 

The nervous system consists of a special type of cell—the neuron or nerve cell. 


Every neuron is made of a cell body (also called a soma), dendrites and an axon. Dendrites and axons are nerve fibres.




1. Central Nervous system (brain and spinal cord)


2. Peripheral Nervous system

        A.   12 pairs of cranial and 31 pairs of spinal nerves


        B.   Afferent (sensory) division


        C.   Efferent (motor) division 

                I. Somatic - Voluntary movements

               II. The autonomic nervous system (Cardiac, smooth Muscle, glands) 

                        (Sympathetic and parasympathetic)


BRAIN – A mass of 12 billion neurons protected by cranial bones.


Parts of Brain

        1. Cerebrum
        2. Cerebellum
        3. Brain-stem
        4. Diencephalon
        5. Ventricles
        6. Meninges

The cerebrum is the largest part of the brain, divided into right and left hemispheres (the left side governs the right side of the body, the right side governs the left side of the body)


There are four lobes in the cerebral hemisphere,


  A.  Frontal – voluntary motor control, learning, planning, and speech

  B.  Parietal – sensory, distance, size, shape, and intellectual processes

  C.  Occipital – vision and visual memory

  D.  Temporal – auditory, olfactory, speech, judgment, & reasoning


The cerebral cortex is the outer layer of grey matter (short- and long-term memory) and cerebral medulla is the white matter (conduction pathways). Corpus callosum is the large fibres that connect the two hemispheres). Gyri and sulci are the elevation and depression on the brain surface, Fissures are deep grooves.


Cerebellum: The RT and LT hemispheres are connected by the central vermis. Outer grey, inner white form the arborvitae. The function is the coordination, movement, posture, balance, running and walking.


Brain stem: Consist of three parts (Mid-brain, Pons and Medulla oblongata)


1. Mid-brain: The upper part of the brain stem.

                          - Controls postural reflexes and walking

                          - Visual reflexes and auditory control


2. Pons – Two-way conduction pathway.

3. Medulla oblongata: The lowest part of the brain-stem.

                                             - 75% of nerve fibres cross here

                                             - Controls vital functions (respiration and circulation)

Diencephalon: Area between the cerebrum and the mid-brain


            A.  Thalamus - The relay station for sensory incoming and motor outgoing impulses.


            B.  Hypothalamus - Controls appetite (hunger and thirst), Temperature control and regulates pituitary secretions. 

Meninges: Three membranous coverings the brain (Dura, Arachnoid, Pia).


    A. Dura mater – strong fibrous tissue, lines the skull bones

                       Epidural space – between the bone and the dura mater.

                       Subdural space – between the dura and arachnoid layers.


    B. Arachnoid – resembles fine cobwebs with fluid (CSF)

                      Subarachnoid space – between the arachnoid and pia layers

    C. Pia mater –covers the brain and spinal cord surface.


Cerebrospinal Fluid (CSF)Serves as a shock absorber for the brain and spinal cord. It is clear, colourless, water, glucose, protein, and WBC. 


Provides nutrients and waste removal for brain tissues, 400-500 ml produced daily, yet only 140 ml is in circulation, Circulates through the ventricles and into the central canal and subarachnoid spaces, and is absorbed back into the blood.


Ventricles: CSF-filled spaces, the rich network of blood vessels and the choroid plexus. maintains selective permeability to protect brain tissue. Foramen of Monro – connects the lateral ventricles to the third ventricle, Aqueduct of Sylvius – connects the third and fourth ventricle.  


In the roof of the fourth ventricle are openings that allow the CSF to move into the cisterna magna, a space behind the medulla that is continuous with the subarachnoid space.  

Spinal Cord: Medulla Oblongata continues as the spinal cord.

“H” - The grey matter of cell bodies of interneurons and motor neurons, divided into anterior, posterior, & lateral horns.

White matter surrounds grey “H”; divided into anterior, posterior, and lateral columns. (Large bundles of nerve axons divided into smaller bundles called tracts); ascending, descending and lateral organizational tracts.

Two bundles of nerve fibres called roots project from each side of the cord, dorsal nerve root (sensory afferent fibres), dorsal root ganglion (sensory cell bodies) and ventral nerve root (motor efferent fibres).

The nerve roots join together to form a single, mixed nerve called a spinal nerve.


Peripheral Nervous System:

A. Cranial Nerves – 12 pairs

1. Olfactory – I: sensory, smell


2. Optic – II: sensory, vision


3. Oculomotor – III: motor, eye movement and pupil


4. Trochlear – IV: motor, eye movement, peripheral vision


5. Trigeminal – V: both, face and head (motor & sensory)


6. Abducens – VI: motor, abducts the eye


7. Facial Nerve – VII: both, facial expression, taste, tongue movement.


8. Vestibulocochlear – VIII: sensory, hearing and balance


9. Glossopharyngeal – IX: both, tongue, throat, swallowing


10. Vagus – X: both, organ sense (thoracic and abdominal) inhibitor


11. Accessory – XI: motor, spinal accessory, shoulder and head movement


12. Hypoglossal – XII: motor, tongue and throat movement



B. Spinal Nerves – 31 pairs


        1.   Cervical        – 8 pairs

        2.   Thoracic       – 12 pairs

        3.   Lumbar        – 5 pairs (Nerves exit the cord at the 1st lumbar vertebra, but do                                                     not exit the spinal canal until reaching their intervertebral                                                  foramina; this gives the cord a “cauda equina” look).

        4.   Sacral          – 5 pairs

        5.   Coccygeal    – 1 pair

Each nerve joins to form a network – Plexuses (Cervical, Brachial, Lumbar, and Sacral).

A dermatome is an area of skin that is mainly supplied by a single spinal nerve.

Upper extremity nerves            Lower extremity nerves

        —  Median nerve                                        Femoral nerve

        —  Ulnar nerve                                            Sciatic nerve      

        —  Radial nerve                                          Common peroneal nerve

                                                                            Tibial and Sural nerve



Common Disease of Nervous System


     1. Epilepsy - A disorder in which nerve cell activity in the brain is disturbed, causing seizures.


    2.  Parkinson's disease - is a long-term degenerative disorder of the central nervous system


    3.  Multiple sclerosis - is a demyelinating disease in which the insulating covers of nerve cells in the brain and spinal cord are damaged


    4.  Hemiplegia - Paralysis of one side of the body. Hemiparesis - a weakness of the entire left or right side of the body. 


    5.  Alzheimer's disease - A progressive disease that destroys memory and other important mental functions.


    6.  Encephalitis - Inflammation of the brain, often due to infection.


    7.  Meningitis - is an acute inflammation of the protective membranes covering the brain and spinal cord


    8.  Quadriplegia - total loss of use of all four limbs


Common Signs and Symptoms of Nervous System

1. Pain

2. Inability to concentrate

3. Memory loss

4. Loss of muscle strength

5. Tremors

6. Slurred speech

7. Seizures

8. Paralysis


1.    Brain                        - Encephalo

2.    Meninges               - Meningo

3.    Spinal cord           - Myelo

4.    Nerve                      - Neuro

5.    Cerebrum             - Cerebro

6.    Cerebellum          - Cerebello

7.    Mind                       - Psycho,   ment/o

8.    Head                       - cephal/o

9.    Nerve root            - radic/o,   radicul/o

10.  Speech                   - phas/o

11.  Sensation             - esthesi/o



1. Ear                               - Auri

2. Hearing                     - Audio

3. Eye                               - Ophthalmo

4. Lens                            - Phako

5. Eyelid                         - Blepharo

6. Pupil                           - Coreo         

7. Lip                               - Cheilo / Labio

8. Cornea                       - Kerato

9. Tympanic membrane  - Myringo 

10. Fingernail / Toenail    - Onycho




1. ADD - Attention deficit disorder

2. ADHD - Attention deficit hyperactivity disorder

3. ANS - Autonomic nervous system

4. CNS - Central nervous system

5. CP - Cerebral palsy

6. CSF - Cerebrospinal fluid

7. CVA - Cerebral vascular accident,

8. EEG - Electroencephalogram

9. HA – Headache

10. ICP - Intracranial pressure

11. IQ - Intelligence quotient

12. LOC - Level of consciousness; loss of consciousness

13. MS - Multiple sclerosis

14. PNS - Peripheral nervous system

15. Sz - Seizure

16. TIA - Transient ischemic attack


Test your Knowledge:


                A. Nervous System Anatomy Quiz