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Chapter 7:)
The Nervous
System
I How it Works
(section !)
• Functions
- receives information about what is happening inside
and outside the environment
* makes you aware of environment around you
* checks conditions inside your body
- directs the way your body responds to information
* stimulus –
* response –
- helps maintain homeostasis
*homeostasis * directs body to respond appropriately
• Structure
- the nervous system includes the brain, nerves, and the
spinal cord.
- nerve- a tissue inside an organ in the nervous system
that is made up of nerve fibers
- neuron- a cell in the nerve tissue in the nervous system
that carries information
* nerve impulse- message that the neuron carries
* dendrites – a nerve fiber in the neuron that caries
impulses
towards the neuron’s cell body
* axon – a nerve fiber in the neuron that carries impulses
away
from the cell body
* the nerve impulse travels into the dendrite then down
the axon
- three types:
* sensory –
* interneuron –
* motor -
• Nerve Impulse Travel
- travels along the neuron in the form of electrical
and chemical signals
*impulses move rapidly toward the neuron cell
body down the axon to the axon tip.
- The a space between the axon tip and next
structure is a synapse.
- The structure could be either another neuron, a
muscle or the cell of another organ.
- To get to the next organ it releases chemicals To
cross
Neuron http://www.youtube.com/watch?v=z6t9Yss45VI
II Divisions of nervous system
(section 2)
• Central Nervous System
- Is the control center of the body
- What's happing in and out of the body is brought
here
* the brain is located in the skull is part of this, it
controls most of the functions in the body
* the spinal cord is a thick column of nerve tissue
that links the brain to most of your nerves in the
peripheral nervous system
• The brain
-
Contains 100 billion neurons which are interneurons
Three layers of connective tissues cover the brain
There are three main parts of the brain
Cerebrum* interprets input from the senses
* controls the movement of skeletal muscles
* carries out mental process such as learning,
remembering, and making judgments.
- cerebellum
* coordinates actions of muscles
* helps keep balance
* motor neuron impulses send messages to
cerebellum and tell how to move body
-
brain stem
* controls body’s involuntary actions
* regulates breathing
* controls heartbeat
The Brain
• spinal cord
- link between brain stem and peripheral nervous
system
- vertebral column
*surrounds and protects spinal cord
- same layers of connective tissue that cover
brain cover spinal cord
- also protected by watery fluid
• Peripheral Nervous System
- consists of a network of nerves that branch out
from the central nervous system and connect it
to the rest of your body
- there are 43 pairs of nerves in entire system
* 12 are in brain
* 31 are in spinal cord
- the pairs split and one nerve goes to left side
and another never impulse goes to the right
side
- These nerves leave spinal cord in spaces
between vertebrae
• reflexes
-
something that your body does automatically
occurs rapidly without conscious control
a good example of a response
some are controlled by spinal cord only, not
brain
* sensory neurons send impulses to spinal cord
* then reaches interneurons in spinal cord
* lastly, it goes directly to motor neurons: at this
time another nerve impulse contracts your
muscle
* it takes longer for pain impulses to reach brain
than it takes the reflex action to occur
• Damages
- concussion
* bruise like injury of brain
* occurs when soft tissue of cerebrum bumps against
skull
* in most headaches occur for short period and tissue
heals itself
* but in some confusion and/or drossiness occurs and
doctors are needed
- spinal cord injuries
* occur when spinal cord is cut or crushed
* when cut, all nerve axon in the region are split and
impulses cannot pass
* paralysis – loss of movement in some part of body
Review:
LABLE THE NEURON
LABLE THE BRAIN