Transcript The Nervous System

The Nervous System
• The NERVOUS
SYSTEM controls
and coordinates
functions
throughout the
body and responds
to internal and
external stimuli
The Nervous System can be
broken into two parts:
• The CENTRAL NERVOUS SYSTEM:
composed of the brain and the spinal
cord
• The PERIPHERAL NERVOUS
SYSTEM: composed of all the nerves
that aren’t part of the brain or spinal
cord
Central Nervous System
• The skull and vertebral column protect the
brain and spinal cord
• The brain and spinal cord are protected in
three layers of tissue called MENINGES
• The space between the meninges and the
brain and spinal cord is filled with
CEREBROSPINAL FLUID, which acts as
a shock absorber and helps protect the
central nervous system.
Parts of the Brain
• CEREBRUM:
contains the frontal,
parietal, occipital, and
temporal lobes
• CEREBELLUM
• BRAIN STEM
• THALAMUS and
HYPOTHALAMUS
The Cerebrum
• Folds in the Cerebrum increase the surface
area of the brain
• Responsible for voluntary actions, intelligence,
learning, and judgment
• Divided into two hemispheres, left and right
• Outer Layer – Gray matter composed of nerve
cell bodies
• Inner Layer – White matter composed of
bundles of axons with myelin sheaths
The Cerebellum:
• Second largest region of the brain
• Located in the back of the skull
• Responsible for balance and muscle
coordination
The Brain Stem:
• Connects the brain to the spinal cord
• Regulates the flow of information from the
brain to the rest of the body
• Controls basic life functions, such as
heartbeat, breathing, swallowing, etc
Thalamus and Hypothalamus
• Located between the brain stem and the
cerebellum
• The THALAMUS receives signals from
the body and sends them to the
cerebrum to be processed
• The HYPOTHALAMUS recognizes and
analyzes hunger, thirst, fatigue, anger,
and body temperature.
The Spinal Cord
• Communication line
between the brain and
the rest of the body
• Made up of bundles of
nerves that branch out
into the rest of the body
• Processes REFLEXES,
quick responses to
stimuli
Peripheral Nervous System
• SENSORY DIVISION
transmits impulses
from the sense
organs to the brain
• MOTOR DIVISION
transmits impulses
from the brain to the
muscles or glands
Peripheral Nervous System
• SOMATIC –
regulates voluntary
impulses
• AUTONOMIC regulates the
involuntary body
functions
SIGHT
Light is focused through the LENS onto the
RETINA. Images are transmitted from the retina
to the brain through the OPTIC NERVE
HEARING – vibrations from noise in the air are
sensed by three tiny bones in the ear, the
HAMMER, ANVIL, and STIRRUP. These create
pressure waves in the fluid of the COCHLEA,
which contains tiny hairs that wave back and forth.
The motion of these hairs produce the nerve
impulses that are sent to the brain
SMELL
• SCENT is the detecting
of trace amounts of
chemicals
• CHEMORECEPTORS in
the lining of the nasal
passages detect these
chemicals and send an
impulse to the brain
• Smell is closely tied to
memory and feeling, and
can generate responses
in people almost
immediately
Taste
• Taste is closely related to
smell, and taste is the
detection of chemicals by
chemoreceptors on the
tongue
• Tastes are classified as
bitter, sour, salty, and
sweet
• The human mouth has
over 10,000 taste buds,
even on the roof!
TOUCH
• Nerve endings in the
skin respond to
temperature, touch and
pain
• The areas that are
most sensitive to touch
have the highest
concentration of nerve
endings: the feet,
hands, and face
How are messages moved in
the nervous system?
NEURONS are cells that transmit
messages, called IMPULSES,
through the nervous system
The CELL BODY contains the
NUCLEUS and most of the cytoplasm,
metabolic activity of the cell takes place
here
DENDRITES branch out from the cell
body, and they carry impulses from the
environment or from other neurons
toward the cell body
The AXON carries impulses away from the cell
body. The axon is covered in a membrane called
the MYELIN SHEATH. There are gaps in the
myelin sheath, called NODES. The signal can
jump from node to node, increasing the speed of
the impulse.
• http://animations.3d4medical.com/Nerveimpulse-animation_AN2162.html
A RESTING NEURON is one that is not
transmitting an impulse.
A neuron can transfer a signal to another cell at
locations called SYNAPSES. At the synapse,
chemicals called NEUROTRANSMITTERS are
released, which sends the impulse to receptors
in an adjacent cell.