Transcript The Nervous System

The Nervous System
Communication Central
Nervous System
• Function: To control and coordinate
functions throughout the body and to
respond to internal and external stimuli.
COMMUNICATION
HOW IS COMMUNICATION
ACCOMPLISHED?
• Cells called neurons transmit electrical
signals called impulses.
• Three Types of Neurons
• Sensory neurons – carry impulses from sense organs to
spinal cord and brain.
• Motor neurons - carry impulses from the brain to muscles
and glands.
• Interneurons - connect sensory and motor neurons.
Divisions of the Nervous System
1. The Central Nervous System
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Brain
Spinal cord
2. The Peripheral Nervous System
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Somatic Nervous System
Autonomic Nervous System
Central Nervous System
The Brain
• 100 billion neurons
• Protected by skull
bones
• Wrapped in three layers
of connective tissue
called meninges.
• Bathed in cerebrospinal
fluid which acts as a
shock absorber.
The Central Nervous System
Spinal Cord
• The communication
link between the
brain and the body.
• 31 pairs of spinal
nerves branch from
the spinal cord.
The Peripheral Nervous System
• All of the nerves that are not a part of the
central nervous system.
• Somatic nervous System - regulates activities that
are under conscious control (muscles) and pain
reflexes.
• Autonomic Nervous System – regulates activities
that are automatic or involuntary.
• Ex: heart rate, blood flow, muscles of digestive system
Sensory Receptors
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Pain receptors (entire body) - indicate danger
or injury
Thermoreceptors (skin, hypothalmus) - detect
variations in temperature
Mechanoreceptors (skin, skeletal muscles,
inner ear) - sensitive to touch, pressure,
sound, motion
Chemoreceptors (nose, taste buds) sensitive to chemicals in environment.
Photoreceptors (eyes) – sensitive to light.
The Senses
Vision
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Iris
Pupil
Lens
Retina
• Rods
• Cones
The Senses
Hearing and Balance
• Hearing is the detection
of sound vibrations.
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Auditory canal
Typmanum
Hammer, anvil, stirrup
Oval window
Cochlea
• Balance is controlled by
the inner ear.
• Semicircular canals
The Senses
Smell and Taste
• The senses of smell and
taste are chemical
senses.
• Much of taste is actually
smell.
• Taste buds are sence
organs that detect taste.
• Taste buds are classified
as salty, bitter, sweet,
and sour.
The Senses
Touch
• All of the regions of
your skin are
sensitive to touch.
• Not all parts of the
body are equally
sensitive to touch.
Why?
• Where would the
most receptors be
found?