Transcript Unit Three Nervous System

Unit Three
Nervous System
Lisa Michelek
Regulation
• Regulation is the life process by which
cells and organisms respond to changes in
and around them.
• The actions of the nervous and endocrine
systems control and regulate the body.
• These two systems allow us to adjust to
internal as well as external environmental
changes.
Nerve Regulation
• There are three parts to nerve regulation:
– The stimulus
– The impulse
– The response
• A stimulus is a specific change in the
environment that affects the nervous system.
• A response is a reaction to this stimulus.
Nerve Regulation
• Many organs and glands of the body receive stimuli
that are translated into impulses.
• An impulse is an electrical or chemical message
that is carried by nerve cells.
• The impulses are then transferred to the central
nervous system (brain and spinal cord).
• The central nervous system then sorts out and
interprets the incoming impulses.
• The impulse is then sent to organs or glands.
• These organs and glands provide responses to
these impulses.
Human Nervous System
• The human nervous
system includes the
brain, spinal cord, and
nerves that lie outside
of the brain and spinal
cord.
• Nerve cells receive
impulses and send
them to various body
parts.
Nerve Cells
• Nerve cells are also called neurons.
• A nerve cell is made up of a
– Cell body – containing the nucleus and cytoplasm
– Dendrites – branched parts that receive impulses from
other
neurons or sense
organs
– Axon – a single,
long fiber that carries
impulses away from
the cell body
Nerve Cells
• Between the
dendrites of one
neuron and the axon
of another is a
space called a
synapse.
• Impulses cross the
synapse by means
of chemical
neurotransmitters.
Nerves
• A nerve is a bundle of neurons
or parts of neurons.
• Nerves can be classified as
– Sensory – carry impulses to the brain and spinal
cord
– Motor – carry impulses from the brain and spinal
cord to the various body parts such as muscles or
glands
– Mixed – contain both sensory and motor fibers
• A nerve fiber is like a telephone line carrying
messages to and from your home.
The Brain
• The brain is the major control center of the
body.
• The bones of the skull surround and protect
the brain.
• The cerebrum,
cerebellum, and medulla
are three parts of
the brain.
The Brain - Cerebrum
• The cerebrum is the center of thinking, memory,
emotions, sensory impulse interpretation, and all
voluntary activity.
• It is the largest part
of the brain.
• When you take a test,
you are using your
cerebrum.
The Brain - Cerebellum
• The cerebellum is responsible for coordination of
muscles and is the center of balance.
• When you bounce a basketball, you are using your
cerebellum.
• Alcohol reduces the ability
of the cerebellum to
coordinate muscle activity.
– This results in slurred speech
and unbalanced walking.
The Brain - Medulla
• The medulla or brain stem is the center of
respiration, heartbeat, and other involuntary
activities.
• Your medulla is controlling
all the activities of your
body that you cannot
control such as
breathing
and peristalsis.
The Spinal Cord
• The spinal cord is the tubular mass of
nerve cells that extends from the brain
stem downward through the center of
the spinal column.
• It is surrounded and protected by the
vertebrae of the spinal column
(backbone).
• The spinal cord relays impulses to and
from the brain and is the center of
some reflex actions.
Receptors
• Receptors are special structures that are
sensitive to stimuli.
• Receptors receive messages.
External Receptors
• External receptors, called sense organs include
–
–
–
–
–
Eyes
Ears
Nose
Tongue
Skin.
Internal Receptors
• Internal receptors are located in the internal
organs
• They allow the brain to detect
–
–
–
–
Hunger
Thirst
Muscle position
Carbon dioxide levels in the blood.
Involuntary Behavior
• The total response of an organism to stimuli is
known as behavior.
• The response may be inborn or learned,
voluntary or involuntary.
• Examples of Involuntary behaviors that occur
automatically without conscious control
include:
– Contraction of heart and diaphragm muscles
– Secretion of glands
– Simple reflexes ( knee jerk and iris movement)
Involuntary Behavior
• Examples of Involuntary actions that are
acquired by the individual through
repetition include:
– Writing one’s name
– Riding a bike
– Playing a musical instrument
The Reflex
• The reflex is an example of involuntary
behavior.
• A reflex action does not require thought; it
is an automatic action.
• Blinking and the knee jerk are
examples of a reflex.
Voluntary Behavior
• Voluntary behaviors require thinking.
• The impulses start in the brain and are
carried by nerve cells to muscles or glands.
• The muscles or glands respond in a certain
way.
• Voluntary actions include
– Measuring with a meter stick
– Picking up a book
– Building a model airplane.
Nervous System Disorders
• Paralysis is caused by severe damage to the
spinal cord.
– It results in the loss of feeling
and muscle function in the
lower parts of the body.
– Paralysis occurs because
impulses to and from the
lower body muscles cannot
be transmitted to the brain.
Nervous System Disorders
• Meningitis is an inflammation of the
membranes that surround the brain and
spinal cord.
– The disease is caused by bacteria.
– The symptoms include severe headache and
stiffness of the neck.
– Meningitis can be fatal.
– Antibiotics are used to treat meningitis.
Nervous System Disorders
• Polio is a viral disease of the central
nervous system that can cause paralysis.
– It can be prevented by immunization.
Drugs and the Nervous System
• Drugs affect the nervous system in many
different ways.
• Some drugs create a feeling of euphoria
(well-being).
• Other drugs cause a decrease in inhibitions,
or an inability to stop doing something that a
person would not normally do.
• Using some drugs results in tolerance when
they are taken continually for a few weeks.
– This means that increasingly larger amounts are
needed to get the desired effect.
Drugs and the Nervous System
• There are some drugs that cause
stimulation (excitement) and feelings of
high energy.
• Physical dependence, or addiction, can
result from using drugs.
• When the drug is withheld,
the addict suffers physical
illness and withdrawal
symptoms.
Nervous System Overview
• http://www.youtube.com/watch?v=x4PPZC
LnVkA