Chapter 1.3 (page 7)

Question 1

What are whitish, fatty, segmented sheaths that many nerve fibres are covered with?

Answer 1

Myelin sheaths

Question 2

What are the 2 cells that produce myelin sheaths in the body?

Answer 2

Schwann cells

Oligodendrocytes

Question 3

Schwann cells along with the axon do not touch and leave gaps called ________________.

Answer 3

Nodes of Ranvier

Question 4

What is an electrical signal or disturbance that carries a message that travels along the surface of neurons in a tract (CNS) or a nerve (PNS)?

This has to be started or initiated by a stimulus such as pressure, temperature or chemical changes.

Answer 4

Nerve impulse

Question 5

A nerve impulse travels in one direction, either toward the CNS over sensory nerves or away from the CNS over motor nerves, toward effector organs; muscles or glands.

Nerve impulses travel along ___________ faster than along _____________ neurons.

Answer 5

Myelinated

Unmyelinated

Question 6

A ________________ (nerve impulse) occurs on the dendrite or cell body of a neuron.

While an ________________ (nerve impulse) only occurs on the axon of a neuron.

Answer 6

Graded potential

Action Potential

Question 7

The outside of the neuron’s plasma membrane and the inside of the cell are positively charged due to the presence of ___________.

Answer 7

Sodium ions (Na+)

Question 8

____________________ is a type of action potential that occurs when an impulse encounters myelin on the whole length of the axon. This type is simply a ‘jump’ of the imulse around the myelin.

Answer 8

Saltatory Conduction

Question 9

What are 3 structures that make up a synapse?

Answer 9

Synaptic knob

Synaptic cleft

Plasma membrane of post-synaptic neuron or effector

Question 10

_____________: These cells wrap themselves around axons of some
nerve fibres found in the PNS.

Answer 10

Schwann cells

Question 11

The outer cell membrane of the
Schwann cell is called the _________ and can play an important role in the regeneration of cut and injured axons.

Answer 11

neurilemma

Question 12

Schwann cells along
with the axon do not touch and leave gaps called ______.

Answer 12

Nodes of Ranvier

Question 13

____________: These cells coil around many different axons in the CNS. They lack Neurilemma. Nodes of Ranvier are present but further apart.

Answer 13

Oligodendrocytes

Question 14

A _____________ is an electrical signal or disturbance that carries a message
that travels along the surface of neurons in a tract (CNS) or a nerve (PNS).

Answer 14

nerve impulse

Question 15

An impulse has to
be started or initiated by a stimulus such as _________ ___________ ____________.

Answer 15

pressure, temperature or chemical changes.

Question 16

A
nerve impulse travels in _______ direction, either toward the CNS over ________ or away
from the CNS over __________, toward effector organs; muscles or glands.

Answer 16

one

sensory nerves

motor nerves

Question 17

A nerve impulse (___________ or _________) is a self-
propagating wave of electrical disturbances that travel along
the surface of a neuron’s plasma membrane.

Answer 17

graded potential or action potential

Question 18

A ___________ occurs on the dendrite or cell body of aneuron. An _______ only occurs on the axon of a neuron.

Answer 18

graded potential

action potential

Question 19

________ allow nerves to communicate with each other by generating and propagating graded and action potentials.

Answer 19

Nerve impulses

Question 20

________________ must be initiated by a stimulus; pressure, temperature, chemical changes, etc. If the stimulus initiates a
______“________, the potential has to reach the neuron’s axon in order to generate an action potential.

Answer 20

Graded potentials

Question 21

The inside of the cell is also positively charged, but there is ____
sodium inside the cell than outside the cell therefore we can say that the inside of the
cell has a __“__ than positive charge as compared to the outside of the neuron; or we
can say the inside of the neuron is _____ charged.

Answer 21

less

less

negatively

Question 22

Resting neuron membrane
potential range is _______ (average______)

Answer 22

• 40 to -90
• 70 millivolts