Central Nervous System

Class XI

Neelam PaniPrincipal

JNV RAIPUR

CNS(command & control system)

controls the volunt

ary movements

, balance of the

body, functioning

of vital

involuntary organ

s

activities of

several endocrine

glands

and human

behaviour

.

thermoregulat

ion, hunger

and thirst,circadian (24-hour)

rhythms of our

body,

site for processing of

vision,

hearing, speech, memory, intelligence,

emotions and thoughts.

CENTRAL NERVOUS SYSTEM

Brain is protected by cranium consists of eight bones:-

one frontal bone; two parietal bones, two temporal bones, one occipital bone, one sphenoid bone and one ethmoid bone. Another 14 bones in the face

make up the entire skull.There are also 3 small bones in

each ear.Brain is protected by three

layers of tissue called meninges.

Brain's Home: The Skull

Skull cranial meninges

An outer layer

Duramater,

very thin middle layer Arachnoid

An inner layer(which is in contact with the

brain tissue)Piamater

BRAINhindbrain

midbrain,

cerebrum, s

Thalamus

hypothalamus,forebrain,

corpora Quaadrigem

ina.

pons,

cerebellum

medulla oblongata

cerebe

PARTS OF BRAIN

PARTS OF BRAIN

FORE BRAIN

ForebrainCerebr

umThalam

usHypothalamus

Cerebrum forms the major part of the human brain.

A deep cleft divides the cerebrum longitudinally into two halves called left and right cerebral hemispheres.

The hemispheres are connected by a tract of nerve fibres called corpus callosum.

FORE BRAIN

Cerebral CortexThe layer of cells which

covers the cerebral hemisphere is called cerebral cortex.

Each hemisphere of the cerebral cortex is divided into four lobes by various sulci and gyri.

The sulci (or fissures) are the grooves and the gyri are the "bumps" that can be seen on the surface of the brain.

The cerebral cortex is referred to as the grey matter due to its greyish appearance.

The cerebral cortex contains motor areas, sensory areas and large regions that are neither clearly sensory nor motor in function.

These regions called as the association areas are responsible for complex functions like inter sensory associations, memory and communication.

Fibres of the tracts are covered with the myelin sheath, which constitute the inner part of cerebral hemisphere. They give an opaque white appearance to the layer and, hence, is called the white matter.

The cerebrum wraps around a structure called thalamus, which is a major coordinating centre for sensory and motor signaling.

Another very important part of the brain called hypothalamus lies at the base of the thalamus.

The hypothalamus is composed of several different area sand is located at the base of the brain.

It is responsible for some very important behaviors.One important function of the hypothalamus is the

control of body temperature The hypothalamus acts like a "thermostat" by sensing changes in body temperature and then sending out signals to adjust the temperature.

The hypothalamus also controls the pituitarygland, emotions, hunger thirst,& circadian rhythms .

The thalamus receives sensory information and relays this information to the cerebral cortex. The cerebral cortex also sends information to the thalamus which then transmits this information to other areas of the brain and spinal cord.

It also contains several groups of neurosecretory cells, which secrete hormones called hypothalamic hormones.

HYPOTHALAMUS & THALAMUS

The inner parts of cerebral hemispheres and group of associated deep structures like amygdale, hippocampus, form a complex structure called the limbic lobe or limbic system.

Along with the hypothalamus, it is involved in the regulation of sexual behavior, expression of emotional reactions like excitement, pleasure, rage and fear and motivation.

The hippocampus is one part of the limbic system that is important for memory and learning.Functions:-

Emotional BehaviorLearning Memory

LIMBIC SYSTEM

The midbrain is located between the thalamus / hypothalamus of the forebrain and pons of the hindbrain.

A canal called the cerebral aqueduct passess through the midbrain. The dorsal portion of the midbrain consists mainly of four round swellings (lobes) called corpora quadrigemina.Functions:-

Vision, Audition, Eye Movement, Body Movement

MID BRAIN

The hindbrain comprises: -Pons, CerebellumMedulla oblongataThe word "cerebellum" comes from the Latin word for

"little brain." Cerebellum has very convoluted surface in order to

provide the additional space for many more neurons.Pons consists of fibre tracts that interconnect different

region of the brain.The medulla of the brain is connected to the spinal

cord. Function:- Movement , Posture, Heart Rate, Blood

pressure, gastric secretions ,Respiration

HIND BRAIN

REFLEX ACTIONThe entire process of response to peripheral

nervous stimulation, that occurs involuntarily, without conscious effort or thought and requires the involvement of a part of the central nervous system is called a reflex action

we do something without thinking about it, or without feeling in control of our reactions.

There are two types of reflex actions:-1) Conditional Reflex Action2) Unconditional reflex Action

conditional Reflex Action

•First control by brain then after practice shifted to the spinal cord.•Ex-Cycling ,Playing the Instruments, etc

unconditional reflex

Action

•Involuntary Actions. Directly control by the spinal cord.•Ex-some sudden action in response to something in the environment like Pull the hand back from the•Flame, mouth starts watering by smelling the tasty food ,etc•e

TYPES OF REFLEX ACTION

RECEPTORORGAN

(Received the stimulus)

SENSORY NERVE

AXON OF SENSORY

NERVE(spinal cord)

INTER NEURON or RELEY

NEURON(spinal cord)

DENTRIDES OF MOTOR NEURON

(ENDPLATES OF MOTOR

NEURON) EFFECTOR

ORGAN

REFLEX ARC

REFLEX ACTION & REFLEX ARC

REFLEX ARC