Transcript The Nervous System

The Nervous System
The Nervous System
• Gathers information both externally and
internally
• Transmits this information for processing
• Processes the information to determine the
best response
• Sends information to the muscles, glands
and organs so they can respond
appropriately
The Nervous System
Central Nervous System
(CNS)
Peripheral Nervous
System (PNS)
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• Nerves that extend
throughout the body
• Gathers and delivers
information
• Works with the Central
Nervous System
Brain and Spinal Cord
Main Control Center
Processes information
Sends instructions to other
parts of the body
The Nervous System
Structure of the Neuron
• Cell body
• Dendrites receive and carry information toward the
cell body
• Axon carries nerve impulses away from the cell
body
• Glial cells protect, support and assist neurons
• In the PNS, the glial cells are Schwann cells
– Schwann cells are wrapped by a myelin sheath
The Central Nervous System
• Brain
Brain Stem: Joins brain to spinal
cord
Cerebellum: Center of coordination
Cerebrum: Largest part of brain,
conscious thought
Cerebral Cortex: Sensory, motor
and association areas
• Spinal Cord
Relays nerve impulses to and from
the brain
Controls spinal reflexes
Parts of the Brain
• 2 cerebral hemispheres
– Further divided into lobes
• Parietal Lobe – somatic sensory area, impulses
traveling from the body’s sensory receptors are
localized & interpreted here
– Ex. pain, cold, touch
• Occipital Lobe – visual area
• Temporal Lobe – auditory area and olfactory area
• Frontal Lobe – primary motor area – skeletal muscles,
also specialized area for fine motor control such as
speech
Cerebral Cortex – sensory and
motor areas
Cerebellum
• 2 hemispheres
– Under occipital lobe of cerebrum
• Balance
• Coordinates body movements (makes
movements smooth)
Cerebellum (colored purple)
Brain Stem
• 3 inches long, diameter of thumb, base of
brain
• 3 parts:
– Midbrain – reflex centers for vision and hearing
– Pons – (means bridge), center for breathing
– Medulla oblongata – merges into spinal cord,
controls heart rate, blood pressure, breathing,
swallowing, vomiting and many others
Spinal Cord
• Continuation of brain stem
• 2-way conduction pathway to and from the
brain and a major reflex center
• Cushioned and protected by meninges
– Meninges = connective tissue membranes
• 31 pairs of spinal nerves arise from the spinal
cord
The Peripheral Nervous System
Somatic Nervous System
Autonomic Nervous System
• Controls voluntary responses of
skeletal muscles
• May involve some reflex
reactions
• Controls the activities of smooth
muscles, organs, and glands
• Divided into:
Sympathetic Nervous System
which controls the response of the
body to stress
Parasympathetic Nervous
System which controls the
functions of the body related to
rest and digestion
The Nervous System
Senses and Sensory
Receptors
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Sight
Hearing
Balance
Taste
Smell
Touch
Temperature
Pain
The Nervous System
Problems
• Regeneration doesn’t occur with nerves that begin in the brain
or spinal cord
• Peripheral nerves may regenerate if they are partially cut or
crushed
• Spinal cord injuries
• Stroke
• Multiple Sclerosis (MS): Body’s own immune system attacks
myelin sheath of nerve fibers
• Amyotrophic Lateral Sclerosis (ALS) or Lou Gehrig’s Disease:
Destroys motor neurons in spinal cord and brain
• Alzheimer’s Disease: Degeneration of the brain’s cortex