Central Nervous System

1. Central Nervous System

2.  CONTENTS
 Nervous system
 Central nervous system
 Division of CNS
 Brain and its parts
 Spinal cord
 Other structures in the brain
 PNS
 ANS
 Physiology of ANS

3.  NERVOUS SYSTEM
The nervous system is divided into
1. CNS consist of Brain & Spinal cord.
2. PNS consisting of:
a. 31 pairs of cranial nerves arising from spinal cord
b. 12 pairs of cranial nerves arising from brain.
c. Autonomic nervous system:
i) Sympathetic nervous system
ii) Parasympathetic nervous system

4.  The central nervous system (CNS) is comprised of the brain and spinal cord.
 The CNS receives sensory information from the nervous system and controls the body's responses.
 The brain plays a central role in the control of most bodily functions, including awareness, movements,
sensations, thoughts, speech, and memory.
 Some reflex movements can occur via spinal cord pathways without the participation of brain
structures. The spinal cord is connected to a section of the brain called the brainstem and runs through
the spinal canal.
 CENTRAL NERVOUS SYSTEM

5. 2
Divisions of the central nervous system

6.  The Brain
• The brain is the control center of the body
• It is about 2% of your body weight and uses 20% of your body’s oxygen.
• The central nervous system is made up of the brain and spinal cord.
• The brain constitutes about one-fiftieth of the body weight and lies within the
cranial cavity.
• The brain parts are
– Cerebrum
– The brain stem (midbrain, pons, medulla oblongata)
– Cerebellum
• The average brain weight of the adult male was 1336 gm,
• for the adult female 1198 gr.
• With increasing age, brain weight decreases by 2.7 gr in males, and by
2.2 gr in females per year.

7. • Cerebrum:
• This is the largest part of the brain and it occupies the anterior and middle cranial fossae.
• Gray Matter – Absenceof myelin in masses of neurons accounts for thegray matter of the brain – Cerebral
Cortex.
• White Matter - Myelinated neurons gives neurons a white appearance – inner layerof cerebrum
• The cerebral cortex is the outer covering of gray matter over the hemispheres.
• Largest partof the brain: Learning and Senses
• 2 hemispheres- Right and Left
• Connected by the Corpus Callosum
• Right side controls- left side
• Left side controls – right side of body
• Each hemisphere of the cerebrum is divided into
lobes which take the names of the bones of the cranium under which they lie:
• frontal
• parietal
• temporal
• Occipital
Cerebral cortex

8.  FUNCTIONS OF THE CEREBRUM
 Frontal Lobe- associated with reasoning, planning, parts of
speech, movement, emotions, and problem solving
 Parietal Lobe- associated with movement, orientation,
recognition, perception of stimuli
 Occipital Lobe- associated with visual processing
 Temporal Lobe- associated with perception and recognition of
auditory stimuli, memory, and speech

9.  CEREBELLUM
 The cerebellum is situated behind the pons and immediately below the posterior portion of the
cerebrum
 It is ovoid in shape and has two hemispheres, separated by a narrow median strip called the
vermis.
 Second largest
 located below the cerebrum at back of skull
 This part is responsible forthe balance and muscle
coordination

10.  Functions of cerebellum
 The cerebellum is concerned with the coordination of voluntary muscular
movement, posture and balance. It coordinates activities associated with the
maintenance of the balance and equilibrium of the body.
 It is also involved in certain cognitive functions, such as language.
 The cerebellum plays a major role in adapting and fine- tuning motor programs to
make accurate movements through a trial-and-error process.
 Damage to the cerebellum results in clumsy uncoordinated muscular movement,
staggering gait and inability to carry out smooth, steady, precise movements.

11.  THE BRAIN STEM (midbrain, pons, medulla oblongata)
 Brain stem is the stem-like part of the base of the brain that is connected to the spinal cord.
 This structure is responsible for basic vital life functions such as breathing, heartbeat, and
blood pressure.
 Medulla oblongata directly controls breathing, blood flow, and other essential functions.
 Connects the brain to spinal cord
 The Two Regions act as “switchboard”
 Medulla Oblongata – Controls heart rate, breathing rate, and
flow of blood through the blood vessels.
 Pons – Relays signals between the cerebrumand thecerebellum

12.  SPINAL CORD
 Link between brain and rest of body (PNS)
 31 pairs of spinal nerves
 Spinal cord is continuous above with the medulla oblongata.
 It is a long, thin bundle of nervous tissue.
 It is approximately 45 cm long in an adult male, and is about the thickness of
the little finger.
 The spinal cord receives and transmits electric signals throughout the entire
body & then back to the brain.
 The white matter tracts in the spinal cord are highways for nerve impulse
propagation. Sensory input travels along these tracts toward the brain (afferent
neurons), and motor output travels from the brain along these tracts toward
skeletal muscles and other effector tissues (efferent neurons).
 The gray matter of the spinal cord receives and integrates incoming and
outgoing information.

13.  The spinal cord enables us to do the things automatically.
 This automatic action is called as Reflex action.
 For e.g., when you touch a hot object, you immediately withdrawn your hand.
 This action does not involve your brain because you do not think at all whether you avoid
the hot object or not.
 In a Reflex action, the nerve impulses take a special pathway called as Reflex arc.
 A reflex is rapid automatic response to the environment that happened without action of the
brain.
 They can be movement or develop through memory.
 The brain remembers how to respond to certain signals or situations.
 This is called as conditional reflex.

14.  THALAMUS
 Receive messages from sensory receptors; relays information to proper
regions of cerebrum
 HYPOTHALAMUS
 Regulates hunger, thirst, fatigue, anger, etc…
 Control of pituitary forendocrine function
 Other Structures inside the Brain
Pons
Pituitary gland
Hypothalamus
Cerebrum
Medulla oblongata Spinal cord
Cerebellum
Thalamus
Pineal
gland
Section 35-3

15.  PERIPHERAL NERVOUS SYSTEM
Spinal nerves: 31 pairs
 8 pairs of cervical nerves
 12 pairs of thoracic nerve
 5 pairs of lumbar nerve
 5 pairs of sacral nerve
 1 pair of coccygeal nerve
Nerve Plexuses
 Cervical
 Brachial
 Lumbar
 Sacral
Cranial nerves
1. Olfactory
2. Optic nerve
3. Occulomotor
4. Trochlear
5. Trigeminal
6. Abducens
7. Facial
8. Vertibulocochlear
9. Glossopharyngeal
10.Vagus
11.Accessory
12.Hypoglossal

16.  AUTONOMIC NERVOUS SYSTEM
 CNS makes person aware of external environment.
 Many activities which do not reach the consciousness of person are regulated and controlled
by the system called as ANS.
 Thus ANS controls and regulate the involuntary functions.
 Called as Autonomic because it is not under the control of will.
Division of ANS
1. Sympathetic nervous system
 Enables the individual to adjust to stress .
 It originates in the thoracic and the lumbar region of the spinal cord.
1. Parasympathetic nervous system
 Participate in tissue building.
 It originates in the cranial and sacral region of the spinal cord.

17.  PHYSIOLOGY OF ANS
Sympathetic stimulation Organ Parasympathetic stimulation
Dilate the pupils Eye Constrict the pupils
Bronchodilation Bronchi Bronchoconstriction
Increase heart rate Heart Decrease the heart rate
Vasodilation Blood vessels Vasoconstriction
Relaxation Smooth muscle Increases the movement
Increase the sweating Sweat glands
Decrease the salivation Salivary gland Increase the salivation
Inhibit secretion Gastric gland Increase secretion
Kidney
Decrease urine flow Blood flow
Relaxation of muscle wall Urinary bladder Constriction of muscle wall
Increase Metabolic effect
Contraction of uterine
muscles
Sex organs Vasodilation and erection