THE NERVOUS SYSTEM
THE NERVOUS SYSTEM – It controls and coordinates all body functions. This system monitors internal
and external stimuli such a smell, touch, sound, blood pressure and body position.
– It plays an important role in the maintenance of homeostasis, which stimulates or inhibits the activities
of other systems.
– It is a complex system that coordinates and controls all body activities, enabling you to learn,
remember, imagine and think logically.
2 CLASSIFICATION OF THE CELLS IN THE NERVOUS SYSTEM:
1. NEURONS – The conducting cells
2. NEUROGLIA – The supportive cells
FACTS:
• Neurons receive stimuli and transmit impulses to other neurons or to other body organs such as
muscles.
• Each neuron consists of a cell body (perikaryon)
THE TWO TYPES OF PROCESS OF A CELL BODY:
1. DENDRITES – These are branching processes that receive stimuli from other neurons and conduct
these stimuli toward the neuron cell body. Also called the AFFERENT PROCESSES.
2. AXON – It conducts impulses away from the nerve cell body. Also called as the EFFERENT
PROCESSES.
MYELIN SHEATH – The axons are covered by a lipid-rich membrane.
NEURON – Is the primary functional and anatomic unit of the nervous system.
CLASSIFICATION OF NEURONS:
1. SENSORY NEURONS – It carry sensory impulses to the spinal cord or to the brain.
2. ASSOCIATIVE NEURONS – The neurons that connect sensory and motor neurons.
3. MOTOR NEURONS – It carry motor impulses from the brain or spinal cord to the target muscles.
SYNAPSE – The contact between the two neurons.
NEUROGLIA – Also known as the glial cell, is a supportive cell of the nervous system that forms 40% of
the brain’s bulk.
5 TYPES OF NEUROGLIA:
1. ASTROCYTES – Supply nutrients to neurons and help maintain their ability to transmit impulses.
2. EPENDYMAL CELL – It produce the cerebrospinal fluid (a protective cushion) and bathe the brain
and the spinal cord.
3. MICROGLIA CELLS – Helps in removing debris and bacteria from the central nervous system
(CNS).
4. OLIGODENDROCYTE – It is found in the CNS.
5. SCHWANN CELL – It is found in the PNS that produce the protective myelin sheath for the
insulation of axons
, MULTIPLE SCLEROSIS (MS) – Is an autoimmune disease that involves demyelination of nerve fibers. It is
caused by the destruction of oligodendrocytes and the proliferation of astrocytes.
SALTATORY CONDUCTION – A type of nerve conduction that involves the impulse transmission through
the nodes of Ranvier.
2 MAJOR DIVISIONS OF THE NERVOUS SYSTEM:
1. CENTRAL NERVOUS SYSTEM (CNS) – It consists of the brain and the spinal cord.
- Primarily controls intelligence, sensory and motor activities involving muscle tone, balance,
and coordination.
2. PERIPHERAL NERVOUS SYSTEM (PNS) – It consists of all the nerves outside the brain and the
spinal cord.
PARTS OF THE NERVOUS SYSTEM
BRAIN
– It is the control center of the human body. It is encased by the bone of the head called the SKULL.
– It is divided into parts according to its position: FOREBRAIN in front, MIDBRAIN in the middle and
HINDBRAIN at the back.
1. FOREBRAIN
– It is the largest part of the brain.
– It houses the nerve center that controls motor and sensory functions, intelligence, personality,
memory and understanding of language.
– It has 3 parts: CEREBRUM, THALAMUS AND HYPOTHALAMUS.
1. CEREBRUM
CEREBRAL CORTEX – The outer layer of the cerebrum which consists of unmyelinated
nerve fibers called GRAY MATTER; WHITE MATTER – The myelinated nerve fibers in the
inner layer of the cerebrum.
CORPUS CALLOSUM – The largest white matter structure that bridges the right and left
hemisphere of the cerebrum, allowing communication between corresponding centers in
each hemisphere
2. THALAMUS
– The primary relay center of the brain.
– It relays all sensory stimuli
3. HYPOTHALAMUS
– Plays an important role in maintaining homeostasis, specifically in controlling
temperature, appetite, thirst, salt and water balance and emotional behavior.
– It also controls the production of numerous hormones and sleeping and waking cycles.
GYRI – (singular GYRUS) Numerous folds in each hemisphere. These folds increase the
surface area of the cortex.
SULCI – (singular: SULCUS) The grooves.
2. MIDBRAIN
THE NERVOUS SYSTEM – It controls and coordinates all body functions. This system monitors internal
and external stimuli such a smell, touch, sound, blood pressure and body position.
– It plays an important role in the maintenance of homeostasis, which stimulates or inhibits the activities
of other systems.
– It is a complex system that coordinates and controls all body activities, enabling you to learn,
remember, imagine and think logically.
2 CLASSIFICATION OF THE CELLS IN THE NERVOUS SYSTEM:
1. NEURONS – The conducting cells
2. NEUROGLIA – The supportive cells
FACTS:
• Neurons receive stimuli and transmit impulses to other neurons or to other body organs such as
muscles.
• Each neuron consists of a cell body (perikaryon)
THE TWO TYPES OF PROCESS OF A CELL BODY:
1. DENDRITES – These are branching processes that receive stimuli from other neurons and conduct
these stimuli toward the neuron cell body. Also called the AFFERENT PROCESSES.
2. AXON – It conducts impulses away from the nerve cell body. Also called as the EFFERENT
PROCESSES.
MYELIN SHEATH – The axons are covered by a lipid-rich membrane.
NEURON – Is the primary functional and anatomic unit of the nervous system.
CLASSIFICATION OF NEURONS:
1. SENSORY NEURONS – It carry sensory impulses to the spinal cord or to the brain.
2. ASSOCIATIVE NEURONS – The neurons that connect sensory and motor neurons.
3. MOTOR NEURONS – It carry motor impulses from the brain or spinal cord to the target muscles.
SYNAPSE – The contact between the two neurons.
NEUROGLIA – Also known as the glial cell, is a supportive cell of the nervous system that forms 40% of
the brain’s bulk.
5 TYPES OF NEUROGLIA:
1. ASTROCYTES – Supply nutrients to neurons and help maintain their ability to transmit impulses.
2. EPENDYMAL CELL – It produce the cerebrospinal fluid (a protective cushion) and bathe the brain
and the spinal cord.
3. MICROGLIA CELLS – Helps in removing debris and bacteria from the central nervous system
(CNS).
4. OLIGODENDROCYTE – It is found in the CNS.
5. SCHWANN CELL – It is found in the PNS that produce the protective myelin sheath for the
insulation of axons
, MULTIPLE SCLEROSIS (MS) – Is an autoimmune disease that involves demyelination of nerve fibers. It is
caused by the destruction of oligodendrocytes and the proliferation of astrocytes.
SALTATORY CONDUCTION – A type of nerve conduction that involves the impulse transmission through
the nodes of Ranvier.
2 MAJOR DIVISIONS OF THE NERVOUS SYSTEM:
1. CENTRAL NERVOUS SYSTEM (CNS) – It consists of the brain and the spinal cord.
- Primarily controls intelligence, sensory and motor activities involving muscle tone, balance,
and coordination.
2. PERIPHERAL NERVOUS SYSTEM (PNS) – It consists of all the nerves outside the brain and the
spinal cord.
PARTS OF THE NERVOUS SYSTEM
BRAIN
– It is the control center of the human body. It is encased by the bone of the head called the SKULL.
– It is divided into parts according to its position: FOREBRAIN in front, MIDBRAIN in the middle and
HINDBRAIN at the back.
1. FOREBRAIN
– It is the largest part of the brain.
– It houses the nerve center that controls motor and sensory functions, intelligence, personality,
memory and understanding of language.
– It has 3 parts: CEREBRUM, THALAMUS AND HYPOTHALAMUS.
1. CEREBRUM
CEREBRAL CORTEX – The outer layer of the cerebrum which consists of unmyelinated
nerve fibers called GRAY MATTER; WHITE MATTER – The myelinated nerve fibers in the
inner layer of the cerebrum.
CORPUS CALLOSUM – The largest white matter structure that bridges the right and left
hemisphere of the cerebrum, allowing communication between corresponding centers in
each hemisphere
2. THALAMUS
– The primary relay center of the brain.
– It relays all sensory stimuli
3. HYPOTHALAMUS
– Plays an important role in maintaining homeostasis, specifically in controlling
temperature, appetite, thirst, salt and water balance and emotional behavior.
– It also controls the production of numerous hormones and sleeping and waking cycles.
GYRI – (singular GYRUS) Numerous folds in each hemisphere. These folds increase the
surface area of the cortex.
SULCI – (singular: SULCUS) The grooves.
2. MIDBRAIN
