Nervous System RQ

1. What does white matter have that gray does not?

2. Which two ions are necessary for nerve impulse transmission?

3. Your senses of taste and ______ are received by chemical receptors.

4. Which class of drugs slows the CNS?

1. What is the basic unit of the nervous system? List

and describe the three main categories.

A “neuron”, or nerve cell is the basic unit

1. Sensory neurons: carry impulses from the body to the brain & spinal cord

2. Interneurons: found within the brain & spinal cord; process impulses & pass response impulses to motor neurons

3. Motor neurons: carry response impulses away from the brain or spinal cord to a muscle or gland

2. How many categories of neurons are there, and what are their jobs?

3. How does your nervous system relay an impulse?

Impulses (messages) travel electrically within a neuron, and chemically between neurons

Sensory information sensory neurons spinal cord brain motor neurons movement/reaction

4. Describe a neuron at rest.

Neurons have three parts: Dendrites – receive impulses from other

neurons Cell body – process the impulses Axon – send impulses to other neurons,

muscles or glands At rest:

The neuron is “polarized” with higher [K+] inside the membrane and higher [Na+] outside of the membrane

5. How is an impulse transmitted?

1. A stimulus excites a neuron and Na+ channels in the cell membrane open & Na+ rushes in

2. This depolarizes the cell (which was negatively charged compared to it’s surroundings)

3. This depolarization travels down the axon to the next neuron

6. What is the difference between the white and gray matter?

White matter (much of the brain & spinal cord) Axons that have “myelin” insulating the

plasma membrane Myelin hinders the movement of ions, which

move fast down the axon’s length (increasing the speed of reactions

Gray matter (interior of brain) Neurons whose axons are not myelinated

7. Describe the connections between neurons.

1. The space between the axon of one neuron and the dendrite of the next neuron is called a synapse

2. Neurotransmitters are the chemicals that diffuse across the synapse to link neurons

3. Enzymes break down the neurotransmitters after the impulse is relayed

8. How do the central and peripheral nervous systems work together?

Central (CNS) – the brain & spinal cord Coordinates all of your body’s activities Receives & processes info from the PNS

Peripheral (PNS) – everything else Senses the environment and with direction

from the CNS responds to that environment

9. Overview the anatomy of the brain.

1. Cerebrum Two connected hemispheres Controls conscious activities, language, skeletal

muscles & senses It is folded and groovy to increase surface area

2. Cerebellum Back of your brain, all foldy looking Controls balance, posture, coordination

3. Brain stem Made up of medulla oblongata, pons, and midbrain MO controls involuntary stuff like breathing & heart rate Pons & midbrain connect the different parts of the brain

10. What does your peripheral nervous system do?

PNS carries impulses to the CNS and performs the reaction necessary (sensory interneuron motor)

Two divisions:1. Somatic NS2. Autonomic NS

11. Describe the somatic nervous system and what it does.

Made up of 12 pairs of cranial nerves and 31 pairs of spinal nerves, all bundled together

Usually in charge of voluntary reactions to stimuli, like skeletal muscle movement Exception: reflexes (next slide)

12. What are reflexes?

Occur within the somatic NS It is an automatic, unconscious

response to a stimulus The sensory information goes to the

spinal cord or brain stem and is immediately dealt with; the cerebrum gets the information after the reflex has occurred

Why would this happen?

13. Your autonomic nervous system is divided into two parts. Name them and describe what they do.

In charge of the involuntary reactions (not under conscious control)

Sympathetic NS Control during stress Causes the release of epinephrine &

norepinephrine that causes “fight or flight” Parasympathetic NS

Controls during rest Calms you down after stressful situations

14. Describe the chemical senses of smell and taste.

Smell The chemical receptors in your nose are hairlike

nerve endings that signal the brain about certain chemicals

The brain processes this information as a particular smell

Taste Chemicals dissolve in saliva and contact the taste

buds (sensory receptors) You have about 10,000 taste buds

Tastes are sour, sweet, bitter, salty, and most recently umami (MSG) and fat!

15. Describe the anatomy of an eye and how this allows you to see.

Retina: thin layer of tissue at the back of the eye that has light receptors and sensory neurons

Rods cells adapted to see in dim light Cones adapted for bright light & colors

1. Light enters through the pupil2. It is focused by the lens3. The focused picture strikes the retina which

comes together to form the optic nerve, which sends the information to the back of the brain

16. How are your senses of hearing and balance related? What structures are associated?

Both are examples of how we sense mechanical stimulation

Both use structures of the earHearing1. Sound causes vibrations (sound waves) which strike

the tympanic membrane2. These vibrations cause the middle ear to vibrate, and

this vibration travels along, deeper into the ear3. Vibration reaches the fluid in the cochlea which causes

the hair cells (sensory receptors) to produce electric impulses

4. These travel along the auditory nerve to the brain where the sound is interpreted

Balance1. Fluid-filled semicircular canals in the inner ear are lined

with hair cells also2. When you tilt your head it bends the hairs sending the

impulse to your brain

17. How does your sense of touch work? Describe what kinds of receptors your body has.

Sensory receptors in the dermis respond to mechanical stimuli

Temperature Heat receptors are deep in the dermis Cold receptors are close to the surface

Pressure Light pressure sensors found especially in the

fingertips, palms, eyelids, lips, and tip of the tongue Heavy/deep pressure sensors found in muscle,

joints, some organs, palms and soles of feet Pain (nocireceptors)

Found everywhere except brain

18. What is a drug? How does it interact in the brain or endocrine system?

Drug – any chemical that affects the body’s functions

Most interact with neurotransmitter or hormone receptors on cells

19. How do pain relievers work on your body? What is an example?

Two ways pain relievers (analgesics) work:

1. Inhibit the receptors that initiate the pain impulse (ex: aspirin)

2. Narcotics manipulate the CNS that receives the impulses (ex: opiates)

20. Describe how drugs can also be used to treat circulatory and nervous disorders. Cardiovascular drugs…

High blood pressure (norvasc, lopressor) Normalize heartbeat (Diltiazem) Increase pumping capacity Enlarge small blood vessels Prevent blood clots (heparin, coumadin, warfarin)

Nervous disorders… Stimulants (amphetamines)

Increase wakefulness and alertness Depressants (sedatives)

Encourage calmness and sleep; reduce anxiety

21. What happens when people misuse drugs? How do addiction, tolerance, and withdrawal fit into this?

Can cause death Misuse…

Taking someone else’s prescription Not taking the drug as prescribed Mixing contraindicated medicines

Abuse… The inappropriate use of a drug for non-

medical purposes Can be illegal or excessive use of legal drugs

Addiction – when a person psychologically needs a drug to function normally; or when a person’s body has developed a chemical need for a drug

Tolerance – when a person needs more and more of a drug to get the same effect

Withdrawal – when a person stops taking the drug and becomes ill

22. Briefly describe stimulants, depressants, narcotics and hallucinogens. How do these different classes of drugs affect the body?

Stimulants: increase CNS activity Caffeine, nicotine, cocaine Can cause alertness, nervousness, anxiety and possible

convulsions Depressants: slows down the CNS activity

Alcohol & barbiturates Relieve anxiety, produce sedation Can cause brain damage and liver cirrhosis; reduced

circulatory and respiratory function Narcotics: opiates (most abused is heroin)

Acts directly on the CNS Slows breathing, lowers heart rate, tolerance develops

quickly Hallucinogens: alter perceptions of the CNS

Disorientation, high blood pressure, body temperature, even convulsions

23. Why is breaking a drug habit difficult? How do smokers try to avoid nicotine withdrawals?

Addiction can be both physiological (body is dependent) and psychological (you feel like you need it)

Replacement therapies can help addicts Nicotine patches and gum for smokers Methadone for morphine and heroin addicts