Unit A Part 1: Nervous System

Question 1

3 nerve types from stimuli to response:

Answer 1

Sensory Neurone
Interneuron
Motor Neurone

Question 2

PNS

Answer 2

Peripheral Neurvous System.
Includes all nerves not in the Brain or Spinal Cord.
All motor and sensory neurones.
Myelinated Neurones

Question 3

CNS

Answer 3

Central Nervous System.
All nerves in brain and spinal cord.
Unmyelinated neurones.

Question 4

Peripheral Nervous System nerve types:

Answer 4

Somatic Nerves: voluntary nerves (sensory/motor).

Autonomic Nerves: involuntary (Sympathetic [stress] and Parasympathetic [return from stress]).

Question 5

Examples of Sympathetic and Parasympathetic nervous reactions:

Answer 5

• pupils (dilates->constricts)
• bronchioles (dilates->constricts)
• heartrate (increase->decrease)
• digestion (increase->stop epinephrine release)

Question 6

The Reflex Arc:

Answer 6

1. Receptor
2. Sensory neurone
3. Spinal cord interneuron
4. Motor neurone
5. Effector

Question 7

Axon:

Answer 7

Extended arm of neurone that carries nerve impulse away from body.

Question 8

Dendrites:

Answer 8

Smaller arms of neurones that receives a nerve impulse.

Question 9

End plates:

Answer 9

Ends of axons that transmits signals to other neurones.

Question 10

Neurilemma:

Answer 10

Delicate membrane that surrounds axon of PNS nerves. Promotes regeneration.

Question 11

Schwann Cells:

Answer 11

A type of glial cell that produces myelin. Only on PNS neurones.

Question 12

Myelin Sheath

Answer 12

An insulating covering over the axon of a neurone produced by Schwann Cells.

Question 13

Node of Ranvier:

Answer 13

Gaps in the myelin sheath where action potentials are performed on myelinated neurones.

Question 14

Why do neurones only send signals one way?

Answer 14

Because Dendrites can only receive signals and End plates can only send.

Question 15

Synapse:

Answer 15

Gap between neurones (post and pre) where a chemical signal is sent. A neurotransmitter is sent to the other neurone into the synapse through an ion channel, which means the impulse is sent.

Question 16

Action Potential:

Answer 16

Electrochemical impulse created by movement of jobs through the nerve cell membrane (signal is being sent).

Question 17

Resting potential:

Answer 17

Step 1 of Action Potential:
Neurone is not sending a signal.
K+ is inside Neurone and more Na+ is outside, meaning neurone is negative.

Question 18

Depolarization:

Answer 18

Step 2 of Action Potential.

Na+ gate is opened and Na+ diffuses across membrane into Neurone. Neurone is now net positive.

Question 19

Repolarization:

Answer 19

Step 3 of Action Potential.
K+ gate opens and it diffuses out of neurone. Pump also turns on, forcing Na+ out and K+ in at a 3/1 ratio.
At some point it’s so effective that it negativity goes below normal, but soon returns (hyperpolarization).
Neurone returns to net negative.

Question 20

Refractory Period:

Answer 20

Recovery time before a nerve can fire again.

Question 21

Threshold:

Answer 21

Charge a Neurone must pass for it to fire (all or nothing).

Stimulus must be greater or equal to threshold.

Question 22

Why are reflexes fast?

Answer 22

They are fast because the PNS, which is what most of reflexes travel through, are myelinated which allow signals to move faster.

Question 23

Neurotransmitters:

Answer 23

Chemicals sent between neurones in synapse to cause change in postsynaptic membrane.

Question 24

Two types of Neurotransmitters:

Answer 24

• Excitatory: open Na+ channels and bring membrane potential towards threshold (activates).
• Inhibitory: makes membrane more permeable to K+ and moves membrane potential further form threshold (deactivates).

Question 25

Summation:

Answer 25

The sum of multiple excitatory potentials produced together may be enough to produce an Action Potential in the postsynaptic neurone if one is not.

Question 26

Another word for sensory and motor nerves is:

Answer 26

Afferent and efferent.