الرئيسية
The structural division of the nervous system are :
1. Central nervous system (CNS)
Includes brain and spinal cord
2. Peripheral nervous system
It made up of all the nerves outside the CNS, and it includes all of the cranial and spinal nerve.
Nerve
Is a bundle of nerve fibers located out side the central nervous system (CNS).
Tract
Is a bundles of nerve fibers within the brain and the spinal cord.
cranial nerves
Are those nerves that carry impulses to and from the brain.
Spinal nerve
Are those nerves that carry impulses to and from the spinal cord.
Sensory neurons (afferent neurons)
Are those nerve fibers that carry impulses or conduct impulses to the brain and spinal cord.
Motor neurons (afferent neurons)
Are those nerve fibers that carry impulses from th3e CNS out to the muscle and gland.
Mixed nerves
Are those nerves that contain both types of fibers (afferent and efferent).
Central nervous system (CNS)
The brain
It occupies the cranial cavity and is covered by a membranes, fluid and the bones of the skull
All the parts of the brain are in communication and they function together.
Parts of the brain
Cerebrum
It is the largest part of the brain, divided in to right and left cerebral hemispheres by a deep groove called the longitudinal fissure
Brain stem
Connect the cerebrum with the spinal cord, composed of the (mid brain, pons, and medulla oblongata).
Diencephalon
It is the area between the cerebral hemispheres and the brain stem.
Cerebellum
Located immediately below the back part of the cerebral hemispheres.
cerebrum
The two cerebral hemispheres.
The outer nerve tissue of the cerebral hemispheres is called cerebral cortex, it is made of gray matter (axon is not covered with myelin). This gray cortex is arranged in folds forming elevated portions known as gyri, which are separated by shallow grooves called sulci.
The internal part of the cerebral hemispheres are made of white matter (axon that covered with myelin), and some of gray matter.
Corpus callosum :
is a band of white matter located at the bottom of the longitudinal fissure. This band acts as a bridge between the right and left hemispheres.
There are many sulci on the brain. The important ones:
1. Central sulcus.
Lies between the frontal and parietal lobes of each hemisphere at right angles to the longitudinal fissure.
2. Lateral sulcus.
Which curves along the side of each hemispheres and separates the temporal lobe from the frontal and parietal lobes.
Parts of the cerebral hemisphere
Frontal lobe
It is large in human, located in front of the central sulcus. It contains motor cortex which direct the actions. The left side of the brain governors the right side of the body the right side of the brain governors the left side of the body, and it contain two speech center.
Parietal lobe
It occupies the upper part of each hemisphere and lies just behind the central sulcus, it contains the sensory area, such as touch, pain, and temperature, are interpreted.
The determination pf distance, size, and shapes also take place here.
Temporal lobe.
It lies below the lateral sulcus and folds under the hemisphere on each side.
This lobe contain the auditory area for receiving and interpreting impulses from the ear.
It also contains olfactory area (related with smell).
Occipital lobe
It lies behind the parietal lobe and extends over the cerebellum. Contain the visual area.
Brain Stem
All parts of the brain stem connect the cerebrum with the spinal cord.
Parts of the brain stem :
1. Mid brain
It is the smallest part of the brain stem.
It located just below the center of the cerebrum, forms the forward part of the brain stem.
2. Pons
Located between the midbrain and the medulla oblongata in front of the cerebellum, it serve to connect the two halves of the cerebellum with the brain stem as well as with the cerebrum above and the spinal cord below.
3. Medulla oblongata
It is the most inferior portion of the brain stem.
It is located between the pons and the spinal cord.
Diencephalon or inter brain
It is located between the cerebral hemispheres and the brain stem.
It can be seen by cutting into the central section of the brain. It includes:
1. Thalamus
It sort-out (distribute) the impulses and direct them to particular areas of the cerebral cortex.
2. Hypothalamus
Located in the midline area below the thalamus, it contains cells that help control body temperature, water balance, sleep, appetite, some emotions, and controls the pituitary gland.
Cerebellum
It located below the back part of the cerebral hemisphere.
It is made of three parts the middle portion and two lateral hemispheres.
The cerebellum has an outer area of gray matter and an inner portion that is largely made of white matter.
The function of the cerebellum are:
• Coordination of voluntary muscles.
• Maintenance of balance.
• Maintenance of muscle tone.
Spinal cord
It extends from the foramen magnum at the base of the skull to the second lumber vertebra.
The spinal cord has a small, irregular shape. It has a gray matter (H-shape appearance) surrounded by a large area of white matter.
Covering of the brain and the spinal cord
The meninges are three layers of connective tissue that surrounded the brain and spinal cord to form a complete enclosure.
The layers of the meninges from out side to in side
• The dura mater
It is the outer most one and it is the thikest one.
• The arachnoid :
It is loosely attached to the deepest of the meninges.
• The pia matter :
It is attached to the nerve tissue of the brain and spinal cord and dips into all depression.
Ventricle of the brain
Are champers or spaces, they are four, and in which cerebrospinal fluid (CSF) is produced.
Cerebrospinal Fluid (CSF)
It is a clear liquid formed in side the ventricles of the brain.
The peripheral nervous system
Cranial nerve
There are 12 Pairs of cranial nerve, they are numbered according to their connection with the brain. The first 9 pairs and the 12 the pair supply structures in the head.
The 12 cranial nerves are always numbered according to the traditional roman style
Names and Functions of the cranial nerves
I. Olfactory nerve: Contain sensory fibers. Carries smell impulses (from receptors in the nasal mucosa to the brain).
II. Optic nerve: Contain Sensory fibers. Carries vesual impulses (from the eye to the brain)
III. Oculomotor nerve: Contain motor fibers. It is concerned with the contraction of most of the eye muscles.
IV. Trochlear nerve: Contain motor fibers. Supplies one eyeball muscle.
V. Trigeminal nerve: Contain both sensory and motor fibers (mixed nerve). A great sensory nerve of the face and head. It has three branches carry general sense impulses from the face to the brain.
VI. Abducens nerve: Contain motor fibers. It send control impulses to an eye ball muscle
X. Vagus nerve: Mixed nerve . It is the longest cranial nerve, it supplies most of the organs in the thoracic and abdominal cavities.
XI. Accessory nerve: Contain motor fibers. Control two muscles of the neck (Trapezius and sternocleidomastoid).
XII. Hypoglossal nerve: Contain motor fibers. Control the muscles of the tongue.
Spinal Nerves
There are 31 pairs of spinal nerve. Each pair numbered according to the level of the spinal cord from which it arises. All the spinal nerves are mixed nerve.
Branches of the spinal nerves:
1. Posterior divisions (small)
2. Anterior divisions (large)
The anterior branches interlace to form networks called (Plexuses)
There are three main plexuses
1. Cervical plexus: Supplies motor impulses to the muscles of the neck and receives sensory impulses from the neck and the back of the head
2. Brachial plexus: Sends numerous branches to the shoulder, arm, forearm, wrist and hand.
3. Lumbosacral plexus: Supplies nerves to the lower extremities
The Autonomic Nervous System
It related to the involuntary impulses. The afferent impulses from the viscera (sensory neurons) are grouped with those that come from the skin and voluntary muscles.
While the efferent neurons (motor neurons) are arranged very differently from those that supply the voluntary muscles.
This variation in the location end arrangement of the visceral afferent neurons has led to their classification as part of separate division called Autonomic nervous system
Parts of the autonomic nervous system
1. Sympathetic pathway: It arise from the spinal cord at the level of the first thoracic nerve down to the level of the second lumbar spinal nerve.
2. Parasympathetic pathway: It begins in the craniosacral area, with fibers arising from the midbrain. Medulla and lower (sacral) part of the spinal cord.
Function of the autonomic nervous system:
It regulates the action of the glands, smooth muscles of hollow organs and the heart .
• The parasympathetic part of the autonomic nervous system normally acts as a balance for the sympathetic system.
1. Central nervous system (CNS)
Includes brain and spinal cord
2. Peripheral nervous system
It made up of all the nerves outside the CNS, and it includes all of the cranial and spinal nerve.
Nerve
Is a bundle of nerve fibers located out side the central nervous system (CNS).
Tract
Is a bundles of nerve fibers within the brain and the spinal cord.
cranial nerves
Are those nerves that carry impulses to and from the brain.
Spinal nerve
Are those nerves that carry impulses to and from the spinal cord.
Sensory neurons (afferent neurons)
Are those nerve fibers that carry impulses or conduct impulses to the brain and spinal cord.
Motor neurons (afferent neurons)
Are those nerve fibers that carry impulses from th3e CNS out to the muscle and gland.
Mixed nerves
Are those nerves that contain both types of fibers (afferent and efferent).
Central nervous system (CNS)
The brain
It occupies the cranial cavity and is covered by a membranes, fluid and the bones of the skull
All the parts of the brain are in communication and they function together.
Parts of the brain
Cerebrum
It is the largest part of the brain, divided in to right and left cerebral hemispheres by a deep groove called the longitudinal fissure
Brain stem
Connect the cerebrum with the spinal cord, composed of the (mid brain, pons, and medulla oblongata).
Diencephalon
It is the area between the cerebral hemispheres and the brain stem.
Cerebellum
Located immediately below the back part of the cerebral hemispheres.
cerebrum
The two cerebral hemispheres.
The outer nerve tissue of the cerebral hemispheres is called cerebral cortex, it is made of gray matter (axon is not covered with myelin). This gray cortex is arranged in folds forming elevated portions known as gyri, which are separated by shallow grooves called sulci.
The internal part of the cerebral hemispheres are made of white matter (axon that covered with myelin), and some of gray matter.
Corpus callosum :
is a band of white matter located at the bottom of the longitudinal fissure. This band acts as a bridge between the right and left hemispheres.
There are many sulci on the brain. The important ones:
1. Central sulcus.
Lies between the frontal and parietal lobes of each hemisphere at right angles to the longitudinal fissure.
2. Lateral sulcus.
Which curves along the side of each hemispheres and separates the temporal lobe from the frontal and parietal lobes.
Parts of the cerebral hemisphere
Frontal lobe
It is large in human, located in front of the central sulcus. It contains motor cortex which direct the actions. The left side of the brain governors the right side of the body the right side of the brain governors the left side of the body, and it contain two speech center.
Parietal lobe
It occupies the upper part of each hemisphere and lies just behind the central sulcus, it contains the sensory area, such as touch, pain, and temperature, are interpreted.
The determination pf distance, size, and shapes also take place here.
Temporal lobe.
It lies below the lateral sulcus and folds under the hemisphere on each side.
This lobe contain the auditory area for receiving and interpreting impulses from the ear.
It also contains olfactory area (related with smell).
Occipital lobe
It lies behind the parietal lobe and extends over the cerebellum. Contain the visual area.
Brain Stem
All parts of the brain stem connect the cerebrum with the spinal cord.
Parts of the brain stem :
1. Mid brain
It is the smallest part of the brain stem.
It located just below the center of the cerebrum, forms the forward part of the brain stem.
2. Pons
Located between the midbrain and the medulla oblongata in front of the cerebellum, it serve to connect the two halves of the cerebellum with the brain stem as well as with the cerebrum above and the spinal cord below.
3. Medulla oblongata
It is the most inferior portion of the brain stem.
It is located between the pons and the spinal cord.
Diencephalon or inter brain
It is located between the cerebral hemispheres and the brain stem.
It can be seen by cutting into the central section of the brain. It includes:
1. Thalamus
It sort-out (distribute) the impulses and direct them to particular areas of the cerebral cortex.
2. Hypothalamus
Located in the midline area below the thalamus, it contains cells that help control body temperature, water balance, sleep, appetite, some emotions, and controls the pituitary gland.
Cerebellum
It located below the back part of the cerebral hemisphere.
It is made of three parts the middle portion and two lateral hemispheres.
The cerebellum has an outer area of gray matter and an inner portion that is largely made of white matter.
The function of the cerebellum are:
• Coordination of voluntary muscles.
• Maintenance of balance.
• Maintenance of muscle tone.
Spinal cord
It extends from the foramen magnum at the base of the skull to the second lumber vertebra.
The spinal cord has a small, irregular shape. It has a gray matter (H-shape appearance) surrounded by a large area of white matter.
Covering of the brain and the spinal cord
The meninges are three layers of connective tissue that surrounded the brain and spinal cord to form a complete enclosure.
The layers of the meninges from out side to in side
• The dura mater
It is the outer most one and it is the thikest one.
• The arachnoid :
It is loosely attached to the deepest of the meninges.
• The pia matter :
It is attached to the nerve tissue of the brain and spinal cord and dips into all depression.
Ventricle of the brain
Are champers or spaces, they are four, and in which cerebrospinal fluid (CSF) is produced.
Cerebrospinal Fluid (CSF)
It is a clear liquid formed in side the ventricles of the brain.
The peripheral nervous system
Cranial nerve
There are 12 Pairs of cranial nerve, they are numbered according to their connection with the brain. The first 9 pairs and the 12 the pair supply structures in the head.
The 12 cranial nerves are always numbered according to the traditional roman style
Names and Functions of the cranial nerves
I. Olfactory nerve: Contain sensory fibers. Carries smell impulses (from receptors in the nasal mucosa to the brain).
II. Optic nerve: Contain Sensory fibers. Carries vesual impulses (from the eye to the brain)
III. Oculomotor nerve: Contain motor fibers. It is concerned with the contraction of most of the eye muscles.
IV. Trochlear nerve: Contain motor fibers. Supplies one eyeball muscle.
V. Trigeminal nerve: Contain both sensory and motor fibers (mixed nerve). A great sensory nerve of the face and head. It has three branches carry general sense impulses from the face to the brain.
VI. Abducens nerve: Contain motor fibers. It send control impulses to an eye ball muscle
X. Vagus nerve: Mixed nerve . It is the longest cranial nerve, it supplies most of the organs in the thoracic and abdominal cavities.
XI. Accessory nerve: Contain motor fibers. Control two muscles of the neck (Trapezius and sternocleidomastoid).
XII. Hypoglossal nerve: Contain motor fibers. Control the muscles of the tongue.
Spinal Nerves
There are 31 pairs of spinal nerve. Each pair numbered according to the level of the spinal cord from which it arises. All the spinal nerves are mixed nerve.
Branches of the spinal nerves:
1. Posterior divisions (small)
2. Anterior divisions (large)
The anterior branches interlace to form networks called (Plexuses)
There are three main plexuses
1. Cervical plexus: Supplies motor impulses to the muscles of the neck and receives sensory impulses from the neck and the back of the head
2. Brachial plexus: Sends numerous branches to the shoulder, arm, forearm, wrist and hand.
3. Lumbosacral plexus: Supplies nerves to the lower extremities
The Autonomic Nervous System
It related to the involuntary impulses. The afferent impulses from the viscera (sensory neurons) are grouped with those that come from the skin and voluntary muscles.
While the efferent neurons (motor neurons) are arranged very differently from those that supply the voluntary muscles.
This variation in the location end arrangement of the visceral afferent neurons has led to their classification as part of separate division called Autonomic nervous system
Parts of the autonomic nervous system
1. Sympathetic pathway: It arise from the spinal cord at the level of the first thoracic nerve down to the level of the second lumbar spinal nerve.
2. Parasympathetic pathway: It begins in the craniosacral area, with fibers arising from the midbrain. Medulla and lower (sacral) part of the spinal cord.
Function of the autonomic nervous system:
It regulates the action of the glands, smooth muscles of hollow organs and the heart .
• The parasympathetic part of the autonomic nervous system normally acts as a balance for the sympathetic system.
