Central nervous system

1. CENTRAL NERVOUS SYSTEM

2. CLASSIFICATION OF NERVOUS SYSTEM
• All bodily activities, voluntary and involuntary, are controlled by the nervous system.
• Nervous system is classified into
I. Central Nervous system
II. Peripheral Nervous system

3. Classification of Nervous system……….
• CNS is composed of the brain(located in the cranial cavity) and the spinal cord (located in the
vertebral cavity), which serve as the main control centers for all body activities.
• PNS is composed of nerves derived from the brain and spinal cord (12 pairs of cranial nerves and 31
pairs of spinal nerves),which serve as linkage between the CNS and the body.
• PNS can be subdivided into Sensory(afferent) nerves and Motor(efferent) nerves. Sensory nerves
send nerve impulse from the body to CNS, while motor nerves send impulse from CNS to effector
organs.
• Motor nerves are divided into the Somatic Nervous system (SNS) which regulates the voluntary
contraction of skeletal muscles and autonomic nervous system(ANS) which regulates the involuntary
control of smooth, cardiac muscles and glands.

4. Classification of Nervous system……….

5. • The central nervous system is composed of two major interconnected organs.
-The Brain
-The Spinal cord
• These organs work together to integrate and coordinate sensory and motor information for the
purpose of controlling the various tissues, organs and organ systems of the body.
• The central nervous system is responsible for higher neural functions such as memory, learning and
emotion.
I. CENTRAL NERVOUS SYSTEM

6. CENTRAL NERVOUS SYSTEM

7. 1.BRAIN
• Brain is one of the largest organ in the body.
• The brain contains approximately 100 billion neurons.
• It is responsible for many of the qualities that make each individual unique-thoughts, feelings,
emotions, talents, memories, and the ability to process information.
• The adult human brain weighs an average of 1.4kg, or about 2 percent of the total body
weight.
• It lies within the cranial cavity.

8. The brain is also wrapped in three layers of connective tissue known as the Meninges.
• The inner most layer------PIA MATER. It is a fibrous layer made up of many blood
vessels which carry food and oxygen to the brain.
• The Middle layer------ ARACHNOID MATER is the thin, elastic, weblike layer between
the Pia mater and the Duramater. It contains CSF.
• The outer layer------DURA MATER, is composed of thick connective tissue.
Brain…….

9. • Between the pia mater and the arachnoid is a space filled with cerebrospinal fluid.
• Cerebrospinal fluid separates the middle and inner meninges and fills four interconnected ventricles, or
cavities in the brain. within the ventricles, cerebrospinal fluid acts as a transport medium for substances
that are important to brain function.
• The Cerebrospinal Fluid is a clear liquid that protects the Brain from mechanical injury by acting as a
Shock Absorber.
• In order for the Brain to perform its functions, it must have a constant supply of Food and Oxygen.
• If the Oxygen supply to the brain is cut off even for a few minutes, the brain will usually suffer enormous
damage. Such damage may result in DEATH.
Brain…….

10. Brain…….

11. • It is divided into 3 main parts on the basis of their function and placements.
• The three main parts of Human brain are
i. Fore brain
ii. Mid brain
iii. Hind brain
Brain…….

12. Brain…….

13. Brain…….

14. i.) FORE BRAIN
Fore brain is also known as Prosencephalon.
It is the anterior part of the brain.
It has 2 parts-Telencephalon & Diencephalon.

15. TELENCEPHALON: Cerebrum
• The cerebrum is the control center of the brain.
• The largest and most prominent part of the human brain is the cerebrum. 85% of the weight of a
human brain.
• The cerebrum is responsible for all the voluntary (conscious) activities of the body. It is the site of
intelligence, learning and judgment.
• The cerebrum is divided into two hemispheres, the left and right cerebral hemispheres.
• The RIGHT hemisphere is associated with creativity and artistic ability. The LEFT hemisphere is
associated with analytical and mathematical ability.

16. Cerebrum………
Left hemisphere
Right hemisphere

17. Cerebrum………
• The two hemispheres are connected by a bridge of nerve fibres that relay information between the
two hemispheres called the Corpus callosum.
• The most obvious feature on the surface of each hemisphere are numerous folds.
• These folds and the grooves increase the surface area of the cerebrum. The ridges are called gyri,
and the grooves are called sulcus.
• The cerebrum, which looks like a wrinkled mushroom, is positioned over the rest of the brain.

18. Cerebrum………
Corpus callosum

19. Cerebrum………

20. Cerebrum………
• Each hemisphere of the cerebrum is divided into four regions called lobes.
• These lobes are named for the skull bones that cover them, frontal, parietal, temporal, and occipital lobes.
• Sometimes blood vessels in the brain are blocked by blood clots, causing a disorder called a Stroke. During a Stroke,
circulation to an area in the brain is blocked and the brain tissue dies.
• A severe Stroke in one side of the brain may cause PARALYSIS of the other side of the body.
• The cerebrum consists of two surfaces
• The folded outer surface is called the cerebral cortex and consists of gray matter (unmyelinated neurons).
• The inner surface is called the cerebral medulla, which is made up of bundles of myelinated axons-The white
matter.

21. Cerebrum………

22. Cerebrum………

23. Cerebrum………

24. Cerebrum………

25. Cerebrum………

26. DIENCEPHALON
Thalamus
It is located above the brain stem and between the mid brain. It receives the
impulses from the eyes, ear, skin and other internal organs and send these
impulses to the cerebrum.
Hypothalamus
It is present below the thalamus. It is the control centers for hunger, thirst,
fatigue, anger and body temperature.

27. ii.) MID BRAIN
• Mid brain is also known as Mesencephalon.
• The roof of this region contains four nuclei. The nuclei form mounds. They are
collectively called corpora quadrigemina.
• It is formed of 2 superior colliculi or mounds and 2 inferior colliculi or mounds.
• The superior colliculi are involved in visual reflexes. They control eye and head
movements. They aid in visual tracking of moving objects.
• The inferior colliculi are involved in hearing.

28. Brain stem……..

29. Brain stem……..

30. Brain stem……..

31. Brain stem……..

32. Brain stem……..

33. iii.) HIND BRAIN
• Hind brain is also known as Rhombencephalon.
• It has 3 parts
 Cerebellum
Pons
Medulla oblongata

34. CEREBELLUM
• It lies below the cerebrum.
• Cerebellum coordinates musculoskeletal movement to maintain posture, balance and muscle tone.
• Tentorium cerebelli is a layer of durameter which separates the cerebrum and cerebellum.
• It has 3 parts Flocculonodular-which aids in balance & maintenance of muscle tone.
• Vermis – anterior part-Which plays a vital role in motor co-ordination and muscle tone.
• Vermis-posterior part-which plays a vital role in fine motor co-ordination and muscle tone.

36. PONS
• Located between the midbrain and the medulla oblongata.
• PONS mean Bridge. This region relays information from the
cerebrum to the cerebellum.
• It also contains sleep center and respiratory centers.
• These centers along with medulla help to control respiratory
movements.

37. Brain…….

38. MEDULLA OBLONGATA
• Medulla oblongata is the most inferior part of the brain stem.
• It contains white matter that conducts impulses between the spinal cord and brain.
• It contains centers that regulate heart and lung functioning, swallowing, vomiting, coughing and sneezing.
• Another important part of the medulla is a group of cells known as the Reticular Activating System (RAS).
• RAS actually helps to alert, or awaken, the upper parts of the brain, including the cerebral cortex. Such
actions keep the brain alert and conscious.
• The RAS helps to control respiration and circulation and serves as a filtering system for incoming sensory
signals. For example, we awaken to the sound of an alarm clock, to a bright light flash, or to a painful pinch
because activity in the RAS that arouses the cerebral cortex.