The central nervous system (CNS) consists of the brain and spinal cord. The CNS is protected by three layers of tissue called meninges and surrounded by cerebrospinal fluid. It contains four interconnected ventricles that produce cerebrospinal fluid. The brain is divided into the forebrain, midbrain, and hindbrain. The forebrain contains the cerebrum and limbic system. The cerebrum is made up of grey matter and white matter and is involved in voluntary movement and complex functions. The spinal cord carries signals between the brain and body and contains 31 pairs of spinal nerves.

1. Central nervous system
(CNS)
• IT INCLUDES BRAIN AND SPINAL CORD
• IT IS THE SITE OF INFORMATION PROCESSING AND CONTROL

2. Introduction
 inside the skull the brain is covered by cranial meninges consisting of an
outer layer called dura mater a very thin middle layer called arachnoid
and an inner layer called pia mater.
 It is protected by bones, where cranial bones protect the brain and neural
canal of vertebral column protects the spinal cord.
 The whole CNS acquires full growth by the age of 6 years.
 CNS is enclosed in 3 meninges and the cavity are lined by ependyma.

3. Meninges
 These are connective tissue membranes with the sequence of Duramater-
archnoid mater and piamater (from outside to inside)
 Dura Mater/hard mother:-outermost and toughest meninx, it carries
epidural space above, subdural space below, both the spaces content
serous fluid
 Archnoid mater:-middle meninx, arrange in the form of spider web, it
carries subarachnoid space below itself, which carries CSF/cerebrospinal
fluid.Archnoid mater also carries meningocytes as the the type of
macrophage an increase in their number is the indication of meningitis.
 Pia mater/soft mother:-thinnest and innermost, highly vascularised in
nature and lice immediately outside of grey matter of brain and white
matter of spinal cord.

4. Ventricles of brain/cavities
 There are four cavities in the brain, commonly termed as ventricles, and
together they form ventricular system
 All the ventricles are interconnected, and they are also connected to
neurocioel/Central canal of spinal cord.
Lateral ventricle/Paracoel(2)
Diocoel/third ventricle(1)
Metacoel/fourth ventricle (1)

5. Lateral ventricles
 These are cavities of cerebral hemisphere, so are the largest ventricle of
the brain. The roof accommodates choroid plexus. The ventricle also basal
nuclei.
 Choroid plexus :- it is a network of blood capillaries which produce
cerebral spinal fluid/CSF
 Basal nucleus :- they are specialised nuclei in the brain,which help to
perform some specific function like involuntary contraction of facial
muscles during expression of emotions, muscles of limbs during walking
and running.
THE BASAL NUCLEI SECRETES DOPAMINE IN AT THE LEVEL OF MOTOR
AREA OF CEREBRUM,THE BALANCE OF DOPAMINE AND ACETYLCHOLINE
ACTUALLY DETERMINES THE MOTOR ACTIVITY OF THE BODY.

6. Third ventricle/Diocoel
 It is the cavity of diencephalon part of forebrain, so fore brain carries 3
ventricles.
 The third ventricle is connected to fourth ventricle through aqueduct of
sylvius/cerebral aqueduct.
 Aqueduct of sylvius passes through midbrain, so midbrain does not have
any ventricle.

7. Fourth ventricle/Metacoel
 It is the cavity of medulla oblongata, and is the smallest of 4 ventricles
 Roof carries posterior choroid plexus and three apertures,where the two
apertures are foramen luschka, and the single median is foramen of
magendie.
 All the three apertures open into the sub arachnoid space and help to
conduct the CSF from metalcoel to subarachnoid space.
 the extension of matter seal is known as neurocoel/centra canal that
passes through spinal cord (extension of medulla oblongata), which is
accommodated in neural canal of vertebral column.
 Neuro seal is terminated at the level of first second lumbar vertebrae

8. Cerebrospinal fluid{CSF}
 It is colourless odourless fluid of CNS which is also regarded as the lymph
of CNS.
 Quantity 150 ml
 Produced by choroid plexus
 Absorbed by veins in Arachnoid villi.
 pH of CSF is 7.2 to 7.4
 Function: it helps to provide nutrition to ependyma and protects the CNS
from Mechanical jerks in the form of cushion.

9. Structure and function of brain

10. functions of brain
 Voluntary movement
 Balance of the body
 Functioning of vital involuntary organs(lungs,heart,kidneys,etc.)
 Thermoregulation Hunger and thirst
 Circadian rhythms of the body
 Activities of several endocrine glands
 And human behaviour

11.  The brain consists of Three major parts forebrain,midbrain and hind brain
 Cerebrum,Cerebellum and brainstem.the fore brain consist of
1. Cerebrum: It is the largest part of the brain and is composed of right and
left cerebral hemisphere.
the two hemispheres are connected by a tract of nerve called Corpus
callosum
the layer of cells which cover the cerebral hemisphere is called cerebral
cortex and is thrown into prominent Folds( or grooves and ridges called sulci
and guru respectively).

12.  cerebral cortex is referred to as Grey matter due to its greyish
appearance.
 the neurone cell bodies are concentrated care during the colours.
 It contains motor area, sensory area and large area that are neither motor
nor sensory in function.
 These regions called as association areas , responsible for complex
functions like inter sensory association,memory and communication.
 Fibres of tract are covered with the myelin sheath,which constitute inner
part of the cerebral hemisphere.

13.  Hypothalamus opaque white appearance to the layer and hence it is
called as white matter.
 THALAMUS :- The celebrando etapa around a structure called tha lamha
,which is a major coordinating centre for sensor and motor signaling
 HYPOTHALAMUS :- important part of brain and lies at the base of
thalamus
Thalamus contains in number of centres which control body temperature
urge for eating and drinking .
Hypothalamus also regarded as master of Masters gland.

14.  Limbic lobe Or limbic system:- the inner part of cerebral hemisphere and
a group of associated deep structures amygdala hippocampus etc forms a
complex structure called limbic lobe or limbic system.
 Along with the hypothalamus, It is involved in the regulation of sexual
behaviour expression of emotional reaction(e.g.,excitement,pleasure,rahe
and fear)and motivation.

15. MIDBRAIN
 Midbrain is located between the thalamus and hypothalamus of the fore brain and
Pons of the brain.
 Canal called cerebral aqueduct passes through midbrain.
 The dorsal portion of the midbrain consists of mainly of four rounds
swellings(lobes)called corpora quadrigemina(optic lobes).
 midbrain and hindbrain forms the brainstem( specifically phones in medulla
oblongata part of hindbrain).

16. Hindbrain
 The Hind brain comprises of.
1. Pond:- Ek consists of fibre tracts that interconnect different region of brain, it is
the middle part of the brain stem.
2. Cerebellum:- cerebellum has very convoluted surface in order to provide the
additional space for many more neurones.
Cerebellum is the second largest part of brain and is also the largest part of
hindbrain, it also consists of two cerebral hemispheres.
the cerebellum helps to maintain the balance of body by regulating coordination
among striated muscles of the body through proprioceptors and vestibular Apparatus
of ear.

17. 3. Medula oblongata:- the middle of brain is connected to spinal cord. The medulla contains Centre
which controls respiration Cardiovascular reflexes and gastric secretion.

18. Spinal cord
 Gross structure:- it is the part of central nervous system and houses inside
vertebral column.
Spinal cord is roughly cylindrical in shape.
Superiorly it begins from the foramen megnam of the brain and inferiorly it
terminates at the level of lumber vertebrae in adults.
It gives attachment to the 31 pairs of nerves along its entire length by the
help of anterior or motor roots and posterior or sensory roots .

19. Internal structure of spinal cord
 The inner portion of spinal cord is known as grey matter and is surrounded by
white matter.
 all spinal nerves are mixed in nature as they carry sensory as well as motor fibres.
 All spinal nerves are formed by union of dorsal and ventral roots.
 All spinal nerves show homolateral / ipsilateral arrangement in the sense the
sensory fiber enter from one side of spinal cord ,will come out as motor nerve
from the same side .

20. Distribution of 31 pair of spinal nerves
 Cervical spinal nerves
 Thoracic spinal nerve: 8pairs
 Lumbar spinal nerve: 12 pairs
 Sacral spinal nerves: 5 pairs
 Caudal spinal nerve: 1pair
{can be remembered as 812,551}

21. Function of spinal nerves
 Afferent fibres/sensory nerves :- These nerve fibre transmit impulses from
tissue /organ to CNS.
 efferent fibres/motor nerves :- the Efferent fibres transmit regulatory
impulses from the CNS to the concerned peripheral tissue /organ.