Chapter 21

Nervous System

Your body responds to changes in the environment. Any internal or external change

that brings about a response is called a ________________.

stimulus

Give an example of an external stimulus and an internal stimulus.

•External stimulusLoud noise, smell of food

•Internal Stimulushormones

Your nervous system is one of several control systems used by your body to maintain homeostasis. Explain what maintaining homeostasis means.

Regulation of steady, life-maintaining conditions inside an organism despite

changes in its environment.Examples: body temperature, blood glucose levels, proper levels of water in the body

The basic functioning units of the nervous system are nerve cells or

________________.

neurons

Identify the three major parts of a neuron and describe the function of each.

DendritesReceive impulses from other neurons and send

them to the cell bodyCell Body

Factory of the neuron; contains a nucleus and other organelles

AxonCarry impulses away from the cell body

Distinguish between sensory neurons, interneurons, and motor neurons.

• Sensory neuronsReceive information and send it to the brain or spinal

cord• Interneurons

Relay impulses between the sensory and motor neurons

• Motor neuronsConduct impulses from brain or spinal cord to muscles

or glands throughout the body

Neurons do not touch each other. To move from one neuron to another, an impulse crosses a small space between neurons called a _____________________.

synapse

Explain how an impulse crosses the space between neurons.

The axon releases a chemical that flows across the synapse and stimulates the

impulse in the dendrite of the next neuron.

Distinguish between the central nervous system and the peripheral

nervous system.

•Central nervous systemMade up of brain and spinal cord

•Peripheral nervous systemConsists of all nerves outside the central nervous

system. 12 pairs of cranial nerves, 31 pairs of spinal nerves

Identify the three major parts of the brain and the function of each.

•CerebrumLargest part of brain; where thinking occurs, memory

is stored, and senses are interpreted•Cerebellum

Maintains muscle tone, balance•Brain Stem

Controls involuntary actions such as breathing and heartbeat; connects brain to spinal cord; consists of

the midbrain, pons, and medulla

Identify the largest part of the brain.

cerebrum

Define cortex.Outer layer of the cerebrum; marked by many ridges

and grooves ; theses ridges and grooves increase surface area, allowing for more complex thought.

Identify the part of the brain that controls the following:

• Breathingbrain stem• Coughingbrain stem• Tastingcerebrum

• Stores memoryCerebrum• Balance

cerebellum

Identify the part of the brain that controls the following:

•VisionCerebrum•Heartbeatbrain stem

•Blood pressureBrain stem•Muscle toneCerebellum

•Interprets sensescerebrum

Your spinal cord is an extension of your ___________________.

Brain stem

Your brain and spinal cord are connected to the rest of your body by the ________ _________ _______.

Peripheral Nervous System

The peripheral nervous system has two divisions. Identify them and describe

the function of each.•Somatic system

Controls voluntary movements

•Autonomic systemControls involuntary movements

The peripheral nervous system is made up of 12 pairs of nerves from your brain called _______ and 31 pairs of nerves from your

spinal cord called______________.

Cranial NervesSpinal Nerves

Identify three major causes of head and spinal cord injury.

Automobile accidentsBicycle accidents

Motorcycle accidentsSports injuries

What can an individual do to prevent head injury?

Wear appropriate safety gear, such as helmets.

A ________ is an involuntary, automatic response to a stimulus.

reflex

Identify three examples of reflexes.

Touching something hot and jerking your hand away

Stepping on something hot and lifting your foot

Production of insulin by the pancreas when blood glucose levels become too high.

You cannot control reflexes because they occur before you know what happened. A reflex involves a simple nerve pathway called a _______ _________.

Reflex arc

Explain how a reflex impulse moves through a reflex arc.

1. Sensory receptors send an impulse to the spinal cord

2. The impulse passes to an interneuron in the spinal cord.

3. The interneuron relays the impulse to the motor neurons.

4. Motor neurons transmit the impulse to muscles or glands throughout the body

Reflexes are controlled by the ________________, not your brain. Your

brain reacts after the reflex to help you figure out what to do .

Spinal Cord

Contrast stimulants and depressants.

•StimulantsDrugs that speeds up the activity of the central

nervous system, causing restlessness, increased heart rate, and insomnia

DepressantsDrugs that slow down the activity of the central

nervous system, impairing concentration, memory, muscle control, and judgment

Give an example of a stimulant and a depressant.•Stimulants

cocaine, crack , amphetaminesCaffeine in soft drinks, tea, coffee

•DepressantsAlcohol, marijuana, heroine, codeine, morphine

Explain why you might have trouble going to sleep after several cups of hot coffee.

Coffee contains caffeine ,which is a stimulant. The caffeine in the coffee can make you

restless and cause insomnia.

Label the parts of a neuron

Study for the test!!!!!

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