1. he Nervous system is very much important in controlling all the
voluntary and involuntary actions of all parts of the body.
The nervous system consist 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 fibers.
PARTS OF NERVOUS SYSTEM,
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. Autonomic nervous system (Cardiac, smooth Muscle,
glands)
(Sympathetic and parasympathetic)
Brain – A mass of 12 billion neurons protected by cranial bones.
Parts of Brain
— Cerebrum
— Cerebellum
— Brain-stem
— Diencephalon0
— Ventricles
— Meninges
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
2. Cerebral cortex is the outer layer of gray matter (short- and long-term
memory) and cerebral medulla is the white matter (conductionpathways).
Corpus callosum is the large fibers 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 gray, inner white form the arbor vitae. Function is
coordination, movement, posture, balance, running and walking.
Brain stem: Consistof three parts (Mid-brain, Pons and Medulla
oblongata)
1. Mid-brain – the upper part of the brain stem.
- Controls posturalreflexes and walking
- Visual reflexes and auditory control
2. Pons – Two way conductionpathway.
3. Medulla oblongata – the lowest part of the brain-stem.
- 75% of nerve fibers cross here
- Controls vital functions (respiration and circulation)
Diencephalon: Area between the cerebrum and the mid-brain
— Thalamus - the relay station for sensory incoming and motor
outgoing impulses.
— Hypothalamus - Controls appetite (hunger and thirst), Temperature
control and regulates pituitary secretions.
Meninges:Three membranous coverings the brain (Dura, Arachnoid,
Pia).
Dura mater – strong fibrous tissue, lines the skull bones
— Epidural space– between the boneand the dura mater.
— Subdural space– between the dura and arachnoid layers.
Arachnoid – resembles fine cobwebs with fluid (CSF)
— Subarachnoid space – between the arachnoid and pia layers
Pia mater –covers the brain and spinal cord surface.
3. CerebrospinalFluid (CSF): Serves as a shockabsorber for the brain and
spinal cord. It is clear, colorless, 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 backinto 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 Sylvus – 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 spacebehind the medulla that is continuous with the
subarachnoid space.
Spinal Cord: Medulla Oblongata continues as spinal cord.
“H” - The gray matter of cell bodies of interneurons and motor neurons,
divided into anterior, posterior, & lateral horns.
White matter surrounds gray “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 fibers called roots project from each side of the
cord, dorsal nerve root (sensory afferent fibers), dorsalroot ganglion
(sensory cell bodies)and ventral nerve root(motor efferent fibers).
The nerve roots join together to form a single, mixed nerve called a spinal
nerve.
Peripheral Nervous System:
Cranial Nerves – 12 pairs
1. Olfactory– I: sensory, smell
4. 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 eye
7. FacialNerve – 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
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 network – Plexuses (Cervical, Brachial, Lumbar,
and Sacral).
Dermatome is an area of skin that is mainly supplied by a single spinal
nerve.
Upper extremity nerves Lowerextremity nerves
— Median nerve Femoral nerve
— Ulnar nerve Sciatic nerve
— Radial nerve Common
peroneal nerve
Tibial and Sural nerve
Common DiseaseofNervous System
5. 1. Epilepsy -A disorderin which nerve cell activity in the brain is
disturbed, causing seizures.
2. Parkinson's disease -is a long-term degenerative disorderof 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
MEDICALTERMS:
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
