Brain and spinal cord HAP notes : Unit 1

Table of Contents

Brain and spinal cord

Central nervous system brain and spinal cord

The nervous system is the most complex system of human body containing millions of nerve cells network. It is the major controlling and coordinating system of human body. It commands body.

Classification of nervous system

Nervous system has two type:

1. CNS : Brain and spinal cord

2.PNS : ANS and Somatic NS.

NEURONS

They generates, carry and transmit nerve impulses.

Structure of Neurons

A Neuron is basically composed of three parts:

Dendrites

Cell body

Axon

CELL BODY: It is also known as Soma. The cell body is the central region containing nucleus is the siteof all major metabolic activity of cell. It is approx 4-100 micrometes in diameter,The ribosomes of neurons is called as Nissle’s Granules.

AXON: Axon is a thin, long and cylindrical process/extension that arisefrom the cell body of Neuron.• Axons are the most important part of neuron • Generally most of the axons are covered by a fatty substance called Myelin Sheath which is further wrapped by Schwann Cells.The area of axon where myelin sheath is absent is known as Node of Ranvier.The site from which axon is extended from cell body is known as Axon Hillock.

Arrangement of neurons in brain and spinal cord

CLASSIFICATION OF NEURONS/NERVE FIBRES

Neurons can be classified on the basis 3 categories:

On the basis of polarity/extension
On thebasis of functionSheath
On the basis of Myelin

On the basis of Polarity neurons are of 4 types:

Unipolar Neurons

Bipolar Neurons

Pseudounipolar Neurons

Multipolar Neurons

UNIPOLAR: These are the neurons in which cell body has Single process.

BIPOLAR: These are those neurons in which cell body has two process

PSEUDOUNIPOLAR : These neurons has Single process but further this process divided into two other process.

MULTIPOLAR : These are the neurons in which cell body has multiple process.

Cns brain and spinal cord

CENTRAL NERVOUS SYSTEM•The central nervous system is mainly consist of Brain and spinal cord.

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How is brain and spinal cord protected

Both Brain and Spinal Cord is protected by cranial cavity .The control nervous system is the major contesting mulatory• It is responsible for everything we do, feel think.Parts of CNSBrain Spinal Cord

MENINGES

Although Brain and Spinal Cord is protected by cranial bones and vertebral column but since they are very sensitive important organ of our body, hence they are further protected by three layer of covering called Meninges.

Meninges are made up of these Layers :

Dura Matter (Outermost Layer)
Arachnoid Matter (Middle Layer)
Pia Matter (Innermost Layer)

Dura Matter :It is divided into sub layers:- Endosteal layer Outer layer towards skull.- Meningeal layer Inner layer towards Arachnoid matter.

Arachnoid Matter: It is the middle fibrous layer.

Pia Matter:It is highly vascular connective tissue layer.

Grey matter and white matter in brain and spinal cord

GREY MATTER & WHITE MATTER

The organs of Central Nervous System ie, Brain & Spinal Cord are composed of two kind of tissues

Grey Matter

White Matter

Grey Matter: It is the major component of central nervous system mainly consist of Neuronal Cell body dendrites.

White Matter: The white matter is the network of fibers mainly consist of myelinated axons/nerve fibers.• In brain it is present in the inner side while in spinal cord it is present on the outer side.

Structure of brain and spinal cord

THE BRAIN

Brain is one of the largest organ in the body which coordinates. most of the body activities.• In males the average weight is about 1370 g while in females it is about 1200 grams.• It is one of the most complex living structures in this universe.

VENTRICLES OF BRAIN:The ventricles are cavities (hollow spaces) filled with Cerebrospinal Fluid•There are four ventricles in our brain that are interconnected to each other.•Each ventricles is lined by ependymal cells which forms Choroid.

Four Ventricles of Brain :

Right Lateral Ventricles

Left Lateral Ventricles

Third Ventricle

Fourth Ventricle

CEREBROSPINAL FLUID (CSF)

CSF is a clear, colourless transparent fruid found in the ventricles.

Choroid Plexus: Choroid Plexus is a network of blood vessels lined by ependymal cells that produces CSF.The volume of CSF is approx 100- 150 ml. • It is secret at a rate of 0.5 ml/min or 500-700 ml/day.

Composition of CSF It is composed of: 99%. Water, 1% Solid Substances

INORGANIC	ORGANIC
Sodium, Potassium	Proteins
Calcium, magnesium	Sugar
Bicarbonates	Uric acid
Chlorides etc	Creatinine etc

Function of CSF :It support, protects act as shock absorbent for CNS.

PARTS OF BRAIN

The Brain can be divided into 4 major parts:

Cerebrum
Cerebellum
Brain Stem
Diencephalon

LOBES OF CEREBRUM

The cerebrum of brain is divided into 4 mayor lobes:

Frontal Lobe
Parietal Lobe
Temporal Lobe
Occipital Lobe
Frontal Lobe: It is also known as Motor Cortex.It controls motor functions like personality, movement planning decision making, creativity, concentration, thoughts etc.
Parietal Lobe: It is also known as Sensory Cortex.It is responsible for controlling logical reasoning recognition, storage of language.
Temporal Lobe: It is also known as Auditory Cortex • It controls hearing, smell, dreams etc.
Occipital Lobe: It is also known as Visual Cortex.It receives input from eyes & controls vision.