Download peripheral nervous system

Chapter 33 Notes,
The Nervous System
Nervous System
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A neuron is a cell of the nervous system that
carries nerve impulses through the body.
There are three kinds of neurons in the body.
Interneurons are neurons found in the brain
and the spinal cord.
Interneurons process information received by
the sensory neurons, and transmit that
information to motor neurons.
Sensory neurons are mostly in the skin and
motor neurons control muscles and glands.
Neurons
The Nervous System
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The nervous system consists of two divisions.
The central nervous system (CNS) includes
the interneurons of the brain and spinal cord.
The peripheral nervous system consists of
the sensory neurons and motor neurons that
carry information to and from the CNS.
Sometimes an impulse triggers an involuntary
reflex that does not involve the brain. The
sensory neurons send information to the spinal
cord, and the spinal cord sends information to a
motor neuron. This is known as a reflex arc.
The Central and Peripheral Nervous Systems
Reflex Arc
The Brain
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There are over 100 billion neurons in the brain.
The largest part of the brain is called the
cerebrum. It is divided into two halves called
hemispheres. The cerebrum is responsible for
learning, memory, language, speech, voluntary
body movements and sensory perception.
The many folds and grooves on the surface of
the cerebrum increase the surface area and
allow more complicated thought processes.
The Cerebrum
The Brain
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The next largest part of the brain, located near
the back of the brain, is called the cerebellum.
The cerebellum is responsible for balance,
posture, and coordination.
The brain stem connects the brain to the spinal
cord. The brain stem is made up of two parts;
the medulla oblongata and the pons.
The medulla oblongata relays signals between
the brain and the spinal cord, and it controls the
breathing rate, heart rate, and blood pressure.
Cerebellum, Medulla Oblongata, and the Pons
The Brain
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The pons relays information between the
cerebrum and the cerebellum.
Located between the brain stem and the
cerebrum is a small region of the brain called
the hypothalamus. The hypothalamus is
responsible for maintaining homeostasis
The hypothalamus maintains body temperature,
thirst, appetite, and water balance.
Additionally, the hypothalamus helps regulate
blood pressure, sleep, aggression, and fear.
The Hypothalamus
The Nervous System
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Most of the nerves in the body that are under
voluntary control, that use the skeletal muscles
are part of the somatic nervous system.
The somatic nervous system relays information
from the external sensory receptors to the CNS.
Somatic motor nerves relay information from
the CNS to the skeletal muscles.
A reflex arc is also an involuntary response of
the somatic nervous system.
The Nervous System
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The part of the peripheral nervous system that
transmits impulses from the CNS to internal
organs, that are under involuntary control is
called the autonomic nervous system.
If you have ever woken up from a nightmare
and your heart was pounding, this is a response
caused by the autonomic nervous system.
If you ever came close to running into a moose
or were involved in a car accident, you probably
felt your body's fight-or-flight response.
Organization of the Nervous System
The Nervous System
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The fight-or-flight response is a response
created by the autonomic nervous system.
The autonomic nervous system has two
branches; they are called the sympathetic and
parasympathetic nervous system.
The sympathetic nervous system is most active
in times of emergency or stress. The heart rate
and breathing rate is elevated, pupils dilated.
The parasympathetic nervous system is most
active when the body is relaxed.
Sympathetic vs. Parasympathetic
Nervous System
The Sensory Organs
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A region of the brain that has special sensory
neurons responsible for the sense of smell is
called the olfactory bulb. The nerves of the
olfactory bulb are called olfactory nerves.
Areas of chemical receptors on the tongue
responsible for taste are called taste buds.
Taste buds are connected to sensory neurons.
The olfactory nerves and taste buds
communicate with one another to enhance the
flavor of food. Without smell, food loses flavor.
Taste and Smell
The Sensory Organs
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When light enters the eye it first travels through
a transparent layer of cells called the cornea.
The amount of light entering the eye is
controlled by muscles of the iris, which is the
part of the eye that is colored.
Behind the iris is the lens. The lens inverts the
image and projects it onto the retina.
The retina contains receptor cells called rods
and cones. Rods help to see in low-light.
Cones function in bright light and detect color.
Anatomy of the Eye
The Sensory Organs
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The two main functions that the ear is
responsible for are hearing and balance.
Sound waves enter the auditory or ear canal.
Sound waves cause the eardrum or
tympanum to vibrate. These vibrations cause
three bones called the malleus (hammer),
incus (anvil), and stapes (stirrup) to vibrate.
Vibrations from these bones cause fluid inside
the cochlea to move tiny hairs. These tiny
hairs send nerve impulses to the brain that
interpret sounds generated by sound waves.
The Sensory Organs
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Inside the inner ear, located near the cochlea
are three canals called semicircular canals.
The semicircular canals are also filled with fluid
and tiny hairs. Only these hairs are not
responsible for hearing, but for balance.
As you move, the fluid in the canals causes the
hairs to bend in response to gravity. The way
the hairs bend sends signals to the brain that
allows us to achieve balance and equilibrium.
Anatomy of the Ear