Unit 9 - Nervous System

Question 1

What are neurons?

Answer 1

Specialized cells that conduct nerve impulses (nerve cells)

Question 2

What is a neuron composed of?

Answer 2

Dendrites
Cell body
Axon

Question 3

What is a neuron composed of?

Answer 3

Dendrites
Cell body
Axon

Question 4

What are dendrites?

Answer 4

Short processes that conduct an impulse towards the cell body. Usually branches

Question 5

What is the cell body?

Answer 5

Contains the nucleus and maintains the cell

Question 6

What is the axon?

Answer 6

Long process conducts an impulse away from the cell body

Question 7

What is information flow in the neurons?

Answer 7

One directional. It only flows from dendrites to the axon

Question 8

What are the three types of neurons?

Answer 8

Sensory neurons
Inter neurons
Motor neurons

Question 9

What do the three neurons make up?

Answer 9

The reflex arc

Question 10

What do receptors do?

Answer 10

Detects stimuli that surpasses a threshold
Initiates impulse in the sensory neuron

Question 11

What does the receptor do?

Answer 11

Detects stimuli that surpasses a threshold
Initiates impulse in the sensory neuron

Question 12

What are some examples of receptors?

Answer 12

Stretch receptor in the alveoli of the lungs
Pain receptor in the skin
Photo receptor in the eyes - light
Chemo receptors in heart and brain - chemicals ex. Tastebuds

Question 13

Describe a sensory neuron

Answer 13

Long dendrite
Nucleus in the dorsal root ganglion (cell body) on the side
Takes sensory info from the receptor to the interneuron

Question 14

Describe an interneuron

Answer 14

Short dendrite and short axon
Entirely in the spinal cord or cns
Connects sensory neuron with the correct motor neuron to get correct response

Question 15

Describe a motor neuron

Answer 15

Short dendrites and long axon (up to 3cm)
Dendrites are in the cns, axon is outside the spinal cord
Takes the impulse to an effector

Question 16

What is an effector?

Answer 16

A muscle or gland
When stimulated, muscle will contract
When stimulated, gland will release a hormone

Question 17

Why can the dendrite of a sensory neuron be in?

Answer 17

Thé sans nerve as the axon of a motor neuron

Question 18

What do long fibres of neurons make up?

Answer 18

Mixed nerves

Question 19

What is in mixed nerves?

Answer 19

Hundreds of long fibres from different neurons taking messages, electrical impulses in both directions to different places.

Question 20

What is a nerve?

Answer 20

A bundle of long fibres from neurons

Question 21

What are long fibres covered with?

Answer 21

A fatty sheath called The myelin sheath

Question 22

What is the myelin sheath composed of?

Answer 22

Schwann cells that wrap around the nerve fibre

Question 23

What are the two functions of a Myelin sheath?

Answer 23

It insulated the neurons from each other as they pass through the nerve

It helps to speed up the impulse

Question 24

What are the points between Schwann cells called?

Answer 24

Nodes of ranvier

Question 25

What do the nodes of ranvier do?

Answer 25

Speed the impulse as it jumps from node to node

Question 26

What is the location and function of a sensory neuron?

Answer 26

Throughout the body
Connects receptors to interneuron

Question 27

What is the location and function of an interneuron?

Answer 27

Nerve cord
Connects sensory to motor neurons

Has no Schwann cells

Question 28

What is the location and function of a motor neuron?

Answer 28

Throughout the body

Connects the interneuron to effector

Question 29

What is a reflex arc?

Answer 29

Fast reaction. Nerve impulse passes the brain

Question 30

Examples of a reflex arc

Answer 30

Pinprick on finger
Spider crawling on leg

Question 31

Are nerve pulses electrical in nature?

Answer 31

Yes

Question 32

When a nerve impulse travels along a nerve fibre what is there a wave of?

Answer 32

Ionic charges that occur which creates a very small shift in the electrical nature of the fibre

Question 33

What does an axon look like at rest?

Answer 33

-20mV
SODIUM IONS (+ve): concentrated on the outside of the axon
POTASSIUM IONS (+ve) and negative organic ions are concentrated on the inside of the axon

The outside of the neuron is slightly positive

The membrane is not permeable to these ions
The sodium and potassium gates are closed
Ions can not move in or out of the nerve cell

Question 34

Axon during depolarization (at peak)

Answer 34

+30mV
If a stimulus is strong enough and surpasses threshold (-55mV), the membrane is suddenly made permeable to sodium

Sodium gates open
Sodium ions go inside of the axon

Question 35

Axon during repolarization (lowest point)

Answer 35

-70mV
When the voltage reaches +30mV, it causes the potassium gates to open, and the potassium goes to the outside

Causes the initial polarity or be restored (-70mV), the ions are in reverse positions
The sodium gates close

Question 36

Axon during recovery phase (refractory period)

Answer 36

At -70mV all gates close

The sodium potassium pump (help from ATP) actively pumps the sodium and potassium ions back to their original condition

During recovery the neuron cannot fire

Question 37

What is the all or none response?

Answer 37

Each impulse is equal to all other impulses

A stronger stimulus does not mean a bigger impulse, but it means a greater number of impulses will give bigger results

Question 38

What makes integration?

Answer 38

Excitatory signals + inhibitory signals

Question 39

What allows the impulse to move faster?

Answer 39

The myelin sheath. It surrounds the long fibres

Question 40

What allows the impulse to move faster?

Answer 40

The myelin sheath. It surrounds the long fibres

Question 41

What is action potential?

Answer 41

The ionic nature of the fibre associated with the movement of the impulse

Question 42

What is the small space between neurons called?

Answer 42

The synaptic gap