INTRODUCTION

The nervous system and the endocrine system together play an important role in our body.

It works to maintain the homeostasis of our body and allows us to survive.

The nervous system detects changes in our body and responds to those changes.

• ORGANIZATION OF NERVOUS SYSTEM

NERVOUS SYSTEM

• CENTRAL NERVOUS SYSTEM

BRAIN AND SPINAL CORD

• PERIPHERAL NERVOUS SYSTEM

AFFERENT ( SENSORY ) NERVE

EFFERENT (MOTOR) NERVE

SOMATIC (MOTOR) NERVE

• AUTONOMIC NERVOUS SYSTEM

SYMPATHETIC

PARASYMPATHETIC.

• NEURONE

Brain contains a large number (100 billion) of neurons.

Each neuron has the following characteristics:

Cell body and its processes

Axon

Dendrites

Some thread-like nerve fibers are also present.

Neurons cannot divide and need constant oxygen for their survival. It gets its energy from glucose.

A neuron has properties of conductivity and excitability, through which it responds to stimuli from the external environment, which may be mechanical, electrical or chemical stimuli.

This stimulus travels from the dendrites of the nerve cell to the cell and the axon in a process known as slow forward conduction.

•Cell Body: Nerve cells vary in size and shape which cannot be seen with the naked eye.

Gray matter is formed from the part of the body of the nerve cell which is located in the periphery of the brain and in the middle of the spinal cord.

A cell body contains a nucleus, cytoplasm and other organelles just like any other cell.

The body of the nerve cell unites to form nuclei in the central nervous system and ganglia in the peripheral nervous system.

•Axons and dendrites:– They are processes extending from the cell body. Each neuron has an axon and a large number of dendrites called nerve fibers. Each nerve contains a bunch of sensory as well as motor nerve fibers.

Axons and dendrites make up the white matter. Which is in the central part of the brain and in the peripheral part of the spinal cord.

• Structure of Axon:-

An axon is a process extending from the cell body. A neuron has one axon. The axon is a thin, cylindrical process. The length of which can be 100cm.

A volume of axon is called a track.

Axons also have organelles similar to cell organelles. The fluid inside it is called exoplasm and the membrane surrounding it is called axolyma.

Schwann cells are present in the peripheral nervous system surrounding axons.

The small gap between the Schwann cells is called node of Ranvir. These nodes and the myelin sheath are essential for proper nerve conduction with nerve fibers.

The membrane surrounding the Schwann cell is called neurilemma.

Surrounding the axons of neurons is a multi-layered sheath of lipids and proteins called the myelin sheath.

A neuron that has such a sheath around its axon is called a myelinated neuron and one that does not have a sheath around it is called a non-myelinated or unmyelinated neuron.

Nerve transmission is reduced in unmyelinated neurons.

•Dendrites :– are branches extending from the cell body. which conducts impulses towards the cell body of the neuron. Dendrites are not myelinated.

• SYNAPSE AND NEUROTRANSMITTERS.

The bulb-shaped structure at the end of the axon of a neuron is called a synaptic knob. The raised spaces in the dendrites of the cell body of the second neuron are called varicocytes.

Both of the above structures contain sac-like structures called synaptic vesicles that contain chemical substances called neurotransmitters. Impulses are transmitted here which is called synapse.

Amino butyric acid (GABA), acetyl choline, dopamine, serotonin etc. act as neurotransmitters in norepinephrine, Ga.

The above neurotransmitters help in the transmission of nerve impulses.

• NERVES.

•Sensory or afferent Nerves:-

-Sensory impulses from the skin, sense organs, muscles, joints and visceral organs are carried through the spinal cord to the central nervous system. In which the following arias are found.

1. Somatic cutaneous conveys impulses of sensations like pain, temperature, touch, vibration etc.
2. Special senses which convey impulses like taste, smell etc.
3. Proprioceptors transmit impulses from special senses like vision, hearing, balance, and cranial nerves through the cranial nerve.

•MOTOR OR EFFERENT NERVES:-

Which conveys impulses from the central nervous system to effector organs, muscles or glands.

1. Somatic nervous gives impulses to control the contraction of skeletal muscles.

2.Autonomic Nervous (sympathetic and parasympathetic) which causes contraction of smooth muscles, cardiac muscles, glands through cranial and spinal nerves.

•MIXED NERVES:-

The spinal cord contains the sensory and motor nerves while the rest of the body is separated by connective tissue. It is called mixed nerve.

• NEUROGLIA.

•They are the support cells of the nervous system. They are generally smaller than neurons and have the capacity to multiply and divide in the mature nervous system. They are supported by four types of nonexcitable cells, including astrocytes, oligodendrocytes, microglia, and epididymal cells that perform different functions in the nervous system.

• CENTRAL NERVOUS SYSTEM.

• Central nervous system consists of brain and spinal cord.
• Meninges

The brain and spinal cord are surrounded by a layer called the meninges that protects the delicate nerve structures. There are three layers of management

1. Dura mater

2.Arachnoid matter

3. Base Matter.

• MENINGIES.

dura mater

The dura mater is the outermost layer of the brain and spinal cord. The dura mater is dense and tough and lies in a double layer. The outer layer forms the outer lining and the inner layer is attached to it except that the dura mater forms a partition in some places.

• Such as fox cerebri which lies between the two cerebral hemispheres which is located on the upper side which is the superior longitudinal fissure where the sagittal sinus is located which receives the venous blood of the brain. Tentorium cerebelli which separates the cerebrum and cerebellum.

•Arachnoid matter

It is a delicate serous membrane that lies between the dura mater and the basal mater and contains collagen fibers and elastic fibers. The space between the skull bone and the dura mater is called the epi dural space

The space below the dura mater is called the sub-dural space.

The space between the arachnoid mater and the base mater is called the subarachnoid space where the cerebrospinal fluid is located.

• Foundation Matter It is the innermost layer. It is a thin and vascular membrane attached to the spinal cord which contains a large number of collagen fibers and fine elastic fibers and also contains many blood vessels which supply nutrition and oxygen to the spinal cord.

• VENTRICLES OF THE BRAIN.

Cavities within the brain are called ventricles in which fluid is produced and circulates around the brain and spinal cord.

1. Right and Left (Lateral Ventricles)
2. Third ventricle
3. Fourth ventricle

1.Lateral ventricle

These cvts lie beneath the corpus callosum of both cerebral hemispheres separated by the septum leucidum. Its lining is composed of epithelium tissue and its wall contains a network of capillaries called choroid plexuses from which cerebrospinal fluid is produced. It connects to the third ventricle through the interventricular foramen.

1. Third ventricle The narrow cavity below the right and left lateral ventricles is called the third ventricle. It connects to the fourth ventricle through the cerebral aqueduct

2. Fourth ventricle It is diamond shaped, lies below the third ventricle and is continuous with the central canal of the spinal cord. The foramen (Lashka and Magendi) on its roof are connected to the subarachnoid space.

• CEREBRO SPINAL FLUID.

Cerebrospinal fluid is produced by the choroid plexus in the wall of the ventricle. The choroid plexus is a network of capillaries located in the wall of the lateral ventricle. Cerebrospinal fluid from this lateral ventricle drains into the third ventricle through the interventricular foramen of Munro and from there into the fourth ventricle through the cerebral aqueduct. From there, some fluid flows into the central canal of the spinal cord and some fluid circulates through the foramen of Lasca and Magendi into the subarachnoid space.

The fluid circulating in the subarachnoid space is absorbed into the blood through the arachnoid wall. CSF is formed at a rate of 20 ml per hour i.e. 480 ml per day and is absorbed at the same rate.

CSF pressure can be measured using a lumbar puncture needle which is 10 cm h2o in the lying position and 30 cm h2o in the sitting position.

CSF is a clear, slightly alkaline fluid with a specific gravity of 1.005.

Its composition includes water, mineral salts, glucose, plasma proteins, some amount of albumin and globulin, creatinine, urea, and some leukocytes.

FUNCTIONS OF CSF.

1.Mechanical protection in which it acts as a shock absorbing medium and provides protection to the delicate structures of the brain.

2. Chemical protection that provides an optimum chemical environment for CSF neural signaling.

3.Circulation in which CSF acts as a medium for exchange of nutrients and waste products between nervous tissue and blood…

• BRAIN.

The normal weight of brain is 1200 to 1400 grams

It is located in the cranium cvt

Its parts are as follows

Cerebrum

Mead brain

Pons Veroli

Medulla oblongata

The cerebellum

Blood supply to the brain is from anastomoses of several arteries of the circle of Wills.

• CEREBRUM.

The cerebrum is composed of the right and left cerebral hemispheres.

The two cerebral hemispheres are connected by the corpus callosum. Each hemisphere has a cavity called a lateral ventricle.

Gray matter is located in the structure of the superficial part of the cerebrum called the cerebral cortex. White matter is located in the deep part of the cerebrum.

The cerebral cortex consists of elevated areas called gyri or convolutions and these are separated by notches called fissures or fissures.

The deepest of these fissures is the longitudinal fissure that separates the right and left hemispheres.

The hemispheres of the cerebrum are divided into different lobes which are as follows.

The cerebrum is composed of the right and left cerebral hemispheres.

The two cerebral hemispheres are connected by the corpus callosum. Each hemisphere has a cavity called a lateral ventricle.

Gray matter is located in the structure of the superficial part of the cerebrum called the cerebral cortex. White matter is located in the deep part of the cerebrum.

The cerebral cortex consists of elevated areas called gyri or convolutions and these are separated by notches called fissures or fissures.

The deepest of these fissures is the longitudinal fissure that separates the right and left hemispheres.

The hemispheres of the cerebrum are divided into different lobes which are as follows.

• Longitudinal sulcus or fissure which is the deepest and divides the cerebrum into two hemispheres.

•Central sulcus which lies between the frontal and parietal lobes.

• Lateral sulcus which is a deep groove and separates the temporal lobe from the frontal and parietal lobes.
• Parieto-occipital sulcus which separates the occipital lobe from the two parietal lobes….

•Nerve fiber tracks are located inside the cerebrum viz

•Association fibers

•Commissural fibers

•Projection fibers

These fibers are interconnected and connect one area to another and help in the transmission of impulses.

FUNCTIONS OF THE CEREBRUM.

1. The control of intelligence, memory, reasoning, thinking, speaking, reading, writing, etc. is seen in the cerebrum.

2.No control is seen for perception of sensory perception like pain, temperature, touch, sight, hearing, taste, smell etc.

3. Control of skeletal muscle contraction is seen from this area.

Functional areas of the Cerebrum.

Many cells in the hemispheres of the cerebrum

Brain Functional Areas

• Motor area Which is mainly located in the anterior part of the cerebral hemisphere. In which the following areas are found.

1.Primary motor area which is located in the frontal lobe and controls the voluntary contraction of muscles.

2. Motor speech area also called Broca’s area which is located in the frontal lobe.

•Sensory Areas of Cerebrum

•Primary somatosensory area or general area located in the parietal lobe behind the central sulcus is the sensory area for touch pain and temperature.

•Primary visual area located in the occipital lobe that interprets vision.

•Primary auditory area located in the temporal lobe and associated with hearing.

•Primary gestatory area located behind the central sulcus in the parietal cortex which is connected to the testes.

• Primary olfactory area which is located in the temporal lobe. Area connected with smell is..

• OTHER AREAS OF CEREBRUM.

There are some special areas in the cerebrum which are connected with the transmission of impulses and other important functions which are as follows.

1.Basal ganglia..it is an area located in each cerebral hemisphere which is responsible for co-ordination of muscle tone, posture and voluntary muscle movement..

2. Thalamus..It is located in the middle of the brain at the top of the brain stem. It acts like a relay station of sensory impulses coming to the sensory area of ​​the cerebral cortex, which leads to the interpretation of proper sensation and some movement control.
3. Hypothalamus…Hypothalamus is made up of a group of nerve cells located below the thalamus whose functions are as follows..

• Hypothalamus controls the following functions.

•Body temperature

• Hunger and thirst

•Emotional reaction

•Autonomic Nervous System

•Sexual behavior

•Biological clock or circadian rhythm…

• Secretion of certain hormones All of the above is done by the hypothalamus.

BRAIN STEM.

The brain stem consists of the following parts

1. Mid brain

2.Pons Veroli

3. Medulla oblongata

•Mid brain

It forms the upper part of the brain stem. On its side, the cerebral aqueduct connects the third and fourth ventricles.

At the top of the midbrain are the important centers of vision and hearing.

In the lower part of the midbrain passes the motor pathway that goes through the pons veroli and medulla oblongata to the spinal cord.

The midbrain contains the control centers for balance and eye movement.

•Pons Veroli

It forms the middle part of the brain stem.

It also has the same ascending and descending nerve pathways as the midbrain, and many nerve tracks are connected to the cerebellum and cerebellar cortex.

Trans of those impulses

•Medulla oblongata

It forms the lowest part of the brain stem and connects the pons veroli to the spinal cord

It is approximately 2.5 cm long and has the following centers.

1.Respiratory center

2. Cardio Vascular Center

3.Vazzo Motor Centre

4. Reflex center for vomiting, gagging and swallowing.

• Medulla oblongatahas some special effects which are as follows

1. Descending motor pathways from the medulla cross and pass through the spinal cord, providing impulses primarily to the skeletal muscles.
2. Like the motor pathway, the sensory pathway also crosses the medulla to the brain.
3. Cardio vascular center located in medulla which controls heart rate and force Sympathetic stimulation increases heart rate and force while parasympathetic stimulation decreases heart rate and force.
4. The medulla houses the respiratory center which controls the rate and depth of respiration in which the intercostal muscles and dia pharm receive nerve impulses for inspiration and expiration.
5. The medulla houses the vasomotor center which controls the diameter of the blood vessels causing vasoconstriction and vasodilatation.
6. The reflex center in the medulla controls vomiting, gagging and hiccups, this is also a protective response.

• CEREBELLUM.

It is the second largest area of ​​the brain behind the medulla and pons veroli.

It is separated from the cerebrum by a transverse fissure where the inner layer of dura mater is inserted to form the tentorium cerebelli.

•The cerebellum performs the following functions

1. It regulates posture and postural activity
2. It plays an important role in coordination of muscles
3. To maintain body balance

• SPINAL CORD.

It starts from the medulla.

It passes through the foramen magnum and is continuous to the second lumbar vertebra.

Its length is about 45 cm.

The spinal cord acts as a connection between the brain and body parts.

Sensory impulses reach the brain and motor impulses travel from the spinal cord to different parts of the body.

Some activities are individualized by the spinal code, which are not required for the functioning of the brain. After the operation is completed, the brain becomes aware of them. This action is completed by spinal reflexes.

For the action of the final reflex, the sensory and motor neurons in the spinal cord are connected by connecting neurons found in the cord at different levels.

•Spinal cord is incompletely divided into two equal parts in which the anterior middle fissure is seen anteriorly and the posterior median septum is seen posteriorly.

In the spinal cord, gray matter is found in the center and white matter in the periphery.

The spinal cord also has layers of meninges just like the brain.

• Gray matter.

H-shaped gray matter is found in the center of the spinal cord. There are two posterior, two anterior and two lateral columns of gray matter arranged in an H shape.

It also has a central canal from the fourth ventricle that contains the cerebrospinal fluid.

Gray matter contains sensory neurons motor neurons and connecting neurons.

• White matter..

The white matter of the spinal cord is located at the periphery

Which is also divided into anterior, lateral and posterior columns. This column also forms tracks through sensory neurons, motor neurons, and connecting neurons.

• FUNCTIONS ..

1. The spinal cord transmits sensory impulses to the brain where they are interpreted.
2. Motor impulses from the brain pass through the spinal cord to different parts of the body.
3. A reflex arch is formed by the spinal cord, which results in a quick action that takes the load off the brain.

• Riflex action Reflex action

The spinal cord acts as a connection between the brain and the body parts. The length of the spinal cord is 45 cm.

It carries sensory impulses to the brain and motor impulses from the spinal cord to different parts of the body.

The spinal code individuates certain activities which are not required for the brain to function and the brain becomes aware of them after the function is completed.

which action is accomplished by spinal reflexes. It is called reflex action.

For spinal reflex action, sensory and motor neurons in the spinal cord are connected by connecting neurons found at different levels in the cord.

A reflex arch is formed by the spinal cord which results in a quick action which reduces the workload of the brain.