1. Control and Coordination
Chapter 21
Control and Coordination

2. Section 1- The Nervous System
Homeostasis
The regulation of steady, life-maintaining conditions inside an organism, despite changes in its environment.
Neurons
Working unit of the nervous system; a nerve cell
Neurons consist of a cell body, axons, and dendrites.
Dendrite
Part of neuron; they receive
messages and send them to cell body.
Axon
Part of neuron; it carries
messages away from cell body.
Synapse
Small space between neurons

3. Types of Nerve Cells Motor Neurons Sensory Neurons Interneurons
Conduct impulses from brain or spinal cord to body parts
Sensory Neurons
Receive info. and send impulses
Interneurons
Relay impulses to motor neurons

4. The Brain Coordinates all of your body activities. Cerebrum Cerebellum
Thinking takes place
Largest part of your brain
Interprets impulses from the senses
Cerebellum
Part of the brain that coordinates your muscle movement. Helps maintain balance.
Brain stem
Connects brain to the spinal cord
Includes the midbrain, pons, and the medulla
Medulla- involuntary actions (heartbeat, breathing and digestion)
Midbrain & pons- acts as pathways that connect various parts of the brain with each other

5. Spinal cord Controls reflex responses
Ex. Withdrawing your hand from a hot stove, your foot from a sharp piece of glass, putting your hands out in front of you to stop a fall.

6. Central Nervous System (CNS) Peripheral Nervous System (PNS)
Made up of the brain and spinal cord
Peripheral Nervous System (PNS)
Made up of nerves outside the central nervous system.
Connects the brain and spinal cord to other body parts. Sensory neurons send impulses to the brain or spinal cord.
2 Major Division of PNS
1) Somatic 2) Autonomic
Somatic- Voluntary Actions
Autonomic- Involuntary Actions
Reflex
Involuntary, automatic response to a stimulus
Stimulus
Change that causes a response in your body

7. What steps happen when you run an iron over your hand accidentally?
1. You aren’t paying attention when you run the iron over your hand.
2. Sensory neurons in your hand send messages to interneurons.
3. Interneurons relay impulses to motor neurons
4. Motor neurons relay impulses to muscles of your hand.
5. Muscles of your hand contract,
responding to the impulses.
6. You pull your hand away
from the iron and scream.

8. Drugs and the Nervous System
Caffeine is a stimulant
A drug that speeds up the activity of the central nervous system.
Increases heart rate
Causes restlessness and insomnia
Causes kidneys to produce more urine
Alcohol is a depressant
A drug that slows the activities of the central nervous system.
Impairs judgment
Destroys brain and liver cells

9. Section 2- The Senses
Sense organs intercept different forms of energy, which are then converted into impulses by the nervous system.
Your senses work together
Maintain homeostasis within your body.
Senses
1) Vision
2) Hearing
3) Smell
4) Taste
5) Touch

10. Vision How do you see???? Light enters the eye – cornea
Next passes through the lens
Lens directs light into the retina
Tissue at back of eye that is sensitive to light energy
Rods (respond to dim light) and cones (respond to bright light and color) are found in the retina.
Light energy stimulates an impulse
Optic Nerve- Carries impulses from the retina to the brain.

13. Rods and Cones
Lens
Cornea
Optic Nerve
Retina

14. Hearing Sound energy is to hearing as light energy is to vision.
When an object vibrates, sound waves are produced.
Outer Ear
Intercepts sound waves and funnels them into the ear canal

15. Middle Ear
Eardrum vibrates
Contains hammer, anvil, and stirrup
Inner Ear
Cochlea- fluid-filled structure in the inner ear
Causes electrical impulses to be sent to the brain by a nerve

16. Smell Olfactory cells Nerve cells in the nose stimulated by molecules
Kept moist by mucus

17. Taste
Taste buds
Major sensory receptors on the tongue
In order to taste something, it has to be dissolved in water. Saliva begins this process.
Smell and taste are related!
Olfactory cells are stimulated through the back of your throat.

18. Other Sensory Receptors
Skin
sensory receptors are located throughout your skin. (Fingertips)
You can tell whether an object is smooth or rough, hot or cold, hard or soft.