Download Human Nervous System

Nervous System
Regulation in humans involve the interaction of both
nervous and endocrine systems.
•They are similar in that they both secrete chemicals and
both play a role in the maintenance of homeostasis.
•They differ in that the responses of the nervous system are
more rapid and of shorter duration than the endocrine.
The nervous system is made up of nerve cells/neurons.
These transmit impulses. There are 3 types:
1. Sensory neurons
2. Motor neurons
3. Interneurons
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Sensory neurons transmit impulses from the sense
organs (receptors) to the brain and spinal cord.
Receptors include eyes, ears, tongue, nose and shin.
Motor neurons transmit impulses from the brain and
spinal cord to the effectors. Effectors include muscles
and glands.
Interneurons are found in the spinal cord and brain.
These transmit nerve impulses from the sensory
neurons to motor neurons.
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Nerves
Nerve cells are bundled together to create a nerve.
There are 3 types of nerves:
1. Sensory nerves (contain only sensory neurons)
2. Motor nerves (contain only motor neurons)
3. Mixed nerves (contain both)
There a 2 parts to the Human Nervous System
1. Central Nervous System (brain & spinal cord)
2. Peripheral Nervous System (all nerves outside the
central nervous system
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The Brain (part of the central nerves)
Medulla
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The Brain (central nerves)
The brain is a large mass of nerve cells located in the cranial
cavity and it is surrounded and protected by the skull bones.
3 Major Brain Areas:
1. Cerebrum
• Largest
• Center for thought, memory, and learning
• Initiates voluntary or conscious movements
2. Cerebellum
• Below and behind the cerebrum
• Maintains body’s balance
• Coordinates motor activities
3. Medulla
• Connects the brain to the spinal cord at the base of brain
• Controls involuntary activities
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The Spinal Cord (central nerves)
•The spinal cord is
connected to the medulla
(bottom of the brain).
•It is surrounded by
vertebrae (backbone) or
spinal column.
•It coordinates activities
between the brain and rest
of body.
•Impulses from the brain
are carried by motor
neurons through the spinal
cord to the rest of the
body.
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Peripheral Nervous System
•This includes all of the neurons outside the central
nervous system.
•These nerve cells carry impulses between the central
nervous system and the rest of the body.
•There are 2 main divisions of the Peripheral Nervous
System. They are the Somatic and the Autonomic
Nervous Systems.
The Somatic Nervous System controls all voluntary
muscles.
The Autonomic Nervous System controls the involuntary
activities of smooth muscles (heart and glands). These
activities regulate heartbeat, circulation, respiration and
peristalsis.
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Nervous System Behavior
Behaviors help us maintain homeostasis. Some behaviors
are inborn while others are learned.
Habits are learned behaviors that become automatic
through repetition. The repetition establishes
pathways for quick responses.
Reflexes are autonomic inborn responses to a particular
stimulus. Here impulses follow a set pathway called a
reflex arc. Reflexes are generally protective in nature and
cause a quick response to a dangerous situation.
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Disorders of the Nervous System
•Cerebral Palsy is a group of diseases caused by damage
to pasts of the brain that control voluntary movement. This
damage occurs during embryonic development.
•Meningitis is an inflammation of the membranes that
surround the brain and spinal cord. This can be caused by
viral or bacterial infections.
•A stoke is a disorder in which the brain is damaged by a
broken blood vessel or blood clot (hemorrhage).
•Polio is a disease that affects the central nervous system
and can result in paralysis. This is caused by a virus that
most people are vaccinated for today.
•Alzheimer’s is a degenerative disease in which neurons in
the brain are gradually destroyed. This fatal illness usually
strikes older people.
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