1. Nervous System
(Eye and Ear)

2. Three Functions of Nervous System
Receive Information
Sensing stimuli
Respond to Information
Reacting to a stimuli
Maintaining Homeostasis
Directing the body to keep in balance

3. Major Structures
of the
Nervous System

5. A Neuron

6. Microscope View of Neuron Stained

7. Key Terms: Nervous System
Nerve (Neuron) = a bundle of nerve fibers, that carries information (impulse) through the nervous system.
Axon = carries impulses away from the cell body.
Dendrite = carries impulses toward the cell body
Synapse = tiny space between each axon tip and the next structure.
Neurochemicals carry the impulse across the synapse.

9. More Terms: Nervous System
Stimulus = any change or signal in the environment that can make an organism react.
Response = what you body does in reaction to a stimulus.
Three Types of Neurons:
Sensory = picks up stimuli inside or outside body
Interneurons = carries impulses nerve to nerve
Motorneurons = sends impulses to a muscle

10. Types of Neurons

12. Central Nervous System: Control Center of the Body
Brain = Controls most of the body’s functions
Concussion = bruiselike injury of the brain.
Using a helmet on skateboards and bikes is important.
Spinal Cord = thick column of nerve tissue linking the brain to the peripheral nerve system.

13. The Human Brain

15. The Brain 100 billion neurons (all interneurons)
Each receives from up to 10,000 other neurons
Each sends to about 1,000 more neurons
Cerebrum = interprets input from senses and controls skeletal muscles, thinking, etc.
Cerebellum = coordinates muscles and balance
Brainstem = controls involuntary actions
Automatic actions like breathing, heart beat, etc.

16. Brain Section

17. Spinal Cord

19. Peripheral Nervous System
A network of nerves branching out from the central nervous system and connecting it to the rest of the body.
It is subdivided into two branches:
Somatic = controls the voluntary actions using your skeletal muscles (like tying your shoes).
Autonomic = controls the involuntary actions using your smooth muscles (stomach, blood vessels).

20. A Voluntary Somatic Response:

21. Reflex =
Automatic response that occurs very rapidly and without conscious control.

22. Your Six Senses Vision: cells convert light stimulus to a nerve signal
Hearing: cells converts sound waves to nerve signal
Smell: cells in nose convert chemical stimuli
Taste: cells on tongue convert chemical stimuli
Touch: cells on skin convert mechanical pressure to nerve signals (impulses).
Balance: Inner ear’s semicircular canals indirectly convert the effect of gravity to nerve signals for balance

23. Structures of the Human Eye:

24. Vision Eyes convert light into nerve impulses Eye Structure:
Cornea – clear tissue covering the front of the eye
Pupil – the opening through which the light enters
Iris – colored area around the pupil which opens or closes
Lens – flexible structure that focuses the light (bends rays)
Retina – layer of receptor cells at back of the eye (130 million) (Rod cells see black/white) (Cones see color)

25. Vision Problems Nearsightedness Farsightedness
Able to see near objects clearly, not distant objects
Eyeball is too long, so focal point is before retina.
Corrected by a concave lens
Farsightedness
Able to see far off objects clearly, not near objects.
Eyeball is too short, so focal point is beyond retina.
Corrected by a convex lens

26. Optical Illusions Simply seeing is not perceiving
Perception involves the brain
Sensory information is processed
The information must be interpreted
It is not always interpreted accurately

43. Describe the function of each of these in allowing you to see:
Guided Practice Questions
Describe the function of each of
these in allowing you to see:
cornea pupil
lens retina
optic nerve brain.
2. How and why does the pupil change
size?
3. Compare and contrast the functions
of the rods and cones.

45. Hearing Ears convert sound waves into nerve impulses
Sound waves are vibrating waves in any substance
Hearing Structures and Processes
Eardrum – receives waves and vibrates the “ear bones”
Cochlea – receives vibrations from the stirrup bone
It is filled with fluid & lined with receptors that respond to sound.
Sensory neurons send the receptor signals to the interneurons of the brain.

46. Your Brain on Alcohol & Drugs
Medicines used properly are helpful, but even they can have serious side-effects.
Drowsiness, confusion, tremors, memory loss, etc
Can become addictive, making you a slave of the chemical
Alcohol and many drugs are chemicals that interfere with your ability to control your brain. Disrupts coordination, making many activities dangerous
Can damage heart and brain cells.