L1 Neurons And Action Potential

Question 1

Name the 2 types within the peripheral nervous system

Answer 1

Autonomic (level of arousal) and Somatic (control of body movements)

Question 2

What are the 2 types of autonomic nervous system

Answer 2

Sympathetic and parasympathetic

Question 3

Describe the 4 main parts of a multipolar neuron

Answer 3

Soma (cell body), dendrites (like tree branches), axon, terminal buttons

Question 4

What do dendrites do?

Answer 4

Receive info from terminal buttons of other neurons

Question 5

What is a synapse?

Answer 5

A junction between the terminal button of an axon and the membrane of another neuron.

Question 6

What is an axon?

Answer 6

The long, thin, cylindrical structure that conveys information from the soma of a neuron to its terminal buttons.

Question 7

What is the difference between a bipolar and a unipolar neuron?

Answer 7

Bipolar =     A neuron with one axon and one dendrite attached to its soma. Is primarily found in sensory systems (for example, vision and audition)
Unipolar =     A neuron with one axon attached to its soma; the axon divides, with one branch receiving sensory information and the other sending the information into the central nervous system.  found in the somatosensory system (e.g. touch,    pain)

Question 8

What is a synapse?

Answer 8

A junction between the terminal button of an axon and the membrane of another neuron. The connection from one neuron to another (they don’t touch).

Question 9

What does the myelin sheath cover?

Answer 9

The axon(s).

Question 10

What forms the myelin sheath in the CNS?

Answer 10

Oligodendrocytes. Has small gaps called “nodes of Ranvier”. Each Oligodendrocyte is attached to several axons.

Question 11

What forms the myelin sheath in the PNS?

Answer 11

Schwann cells = same role as oligodendrocytes, but only 1 per axon.

Question 12

What is the Action Potential?

Answer 12

A brief electrical message which travels down the neuron’s axon. “Transient change in electrical charge across a neuron’s membrane”.

Question 13

What the the 3 ions in cell fluid?

Answer 13

Sodium (Na+), Potassium (K+), Chloride (Cl-)

Question 14

What is the value of the resting potential within the neuron?

Answer 14

• 70 mv

Question 15

During action potential what does the charge of the neuron change to?

Answer 15

+ 40 mv

Question 16

What is the force of diffusion?

Answer 16

Ions move from area of higher concentration to area of lower concentration.

Question 17

What is electrostatic force?

Answer 17

Two ions with the same charge repel each other. Two ions of different charge attract each other.

Question 18

Which ion has both diffusion and electrostatic charge forces moving from outside to inside the neuron?

Answer 18

Na+ Sodium - concentration outside neuron is higher and it is +ve charged so attracted to the -ve chanrge of the neuron

Question 19

Why doesn’t Na+ move into the neuron at rest?

Answer 19

1. Neuron membrane (at rest) is not very permeable to Na+

2. Some Na+ which does leak into the neuron but is removed by sodium potassium transporter.

Question 20

What happens to the Na+ (sodium) channels when the neuron receives a signal?

Answer 20

They open and Na+ enters the neuron.

Question 21

How is the action potential initiated?

Answer 21

It reaches the threshold of excitation (-55 mv)

Question 22

What 2 things happen when an action potential fires?

Answer 22

1. Electrical signal goes down the axon, reaches the terminal button and becomes a chemical message (neurotransmitter)
2. More Na+ channels open & Na + rushes into cell, causing the inside of the cell to become +40 mv relative to the outside of the cell.

Question 23

How does the neuron move back to the resting potential?

Answer 23

K+ (potassium) exits the cell as the inside is now +vely charged and the K+ channels have opened. Electrostatic pressure and force of diffusion pushes it out of the neuron.

Question 24

What is saltatory conduction?

Answer 24

Conduction of action potentials by myelinated axons. The action potential appears to jump from one Node of Ranvier (gaps in the myelin sheath where the neuron is exposed to extracellular fluid) to the next. Conduction is faster in myelinated axons vs unmyelinated.

Question 25

What is the rate law?

Answer 25

The rate of firing determines the strength of a stimulus. The size of AP doesn’t vary - the frequency does.

Question 26

What happens during the refractory period during the action potential?

Answer 26

Sodium channels do not allow any more sodium to enter the cell and cannot be stimulated again until they reset (when the potassium channels close).

Question 27

How is action potential conducted in both myelinated and unmyelinated neurons?

Answer 27

The Na+ channels, just ahead of where the action potential is at, open.

Question 28

What the the 2 advantages of myelin?

Answer 28

Speeds conduction (jumps using Nodes of Ranvier) and reduces interference from adjacent neurons (sodium can only enter at the Nodes of Ranvier)

Question 29

What stain identifies a neuron?

Answer 29

Golgi stain

Question 30

What do glial cells do?

Answer 30

Act like glue. Hold things in place

Question 31

What do astrocytes do?

Answer 31

Star-like. Take away toxins, release nutritious chemicals.

Question 32

What are -vely charged ions called?

Answer 32

Anions

Question 33

What are +vely charged ions called?

Answer 33

Cations