5.3 Neuronal Communication

Question 1

Why are neurones very long?

Answer 1

So that they can transmit an action potential over a large distance

Question 2

Why does a neurone plasma membrane have many gated ion channels?

Answer 2

To control the entry or exit of Na+ , K+ and Ca2+

Question 3

Sodium/Potassium pumps use _____ to actively transport Na+ ____ and K+ ____ the cell.

Answer 3

ATP, Na+ out, K+ in

Question 4

What is the function of a dendrite?

Answer 4

To carry nerve impulses towards the cell body

Question 5

What is the function of the axon?

Answer 5

To carry nerve impulses away from the cell body

Question 6

What is the purpose of Shwann cells?

Answer 6

To insulate electrical activity from affecting nearby cells

Question 7

Where do motor neurones have their cell body?

Answer 7

In the CNS

Question 8

What is a myelinated neurone?

Answer 8

A neurone insulated by an individual mylein sheath.

Question 9

Why do motor neurones have an extra long axon?

Answer 9

To carry the action potential from the CNS to an effector.

Question 10

Where is the cell body of a sensory neurone?

Answer 10

Just outside the CNS

Question 11

Sensory neurones have a long ______ that carries an action potential from a sensory _______ to the cell body (just outside CNS) then a short _____ carrying the impulse into the CNS.

Answer 11

Long dendrite, sensory receptor, short axon

Question 12

What are gaps in the myelin sheath called?

Answer 12

Nodes of Ranvier

Question 13

What is an action potential?

Answer 13

A brief reversal of the potential difference across the membrane at a peak of +40mV

Question 14

What is resting potential?

Answer 14

When the nerve cell is at rest with a potential difference across the membrane of -60mV

Question 15

What is the all or nothing principle?

Answer 15

All nerve impulses are identical, independent of the strength of a stimulus.

Question 16

What value (mV) must be reached before an action potential can be transmitted?

Answer 16

+40mV

Question 17

What is a Pacinian corpuscle?

Answer 17

A pressure sensory receptor that detects pressure changes on the skin

Question 18

Sensory receptors are energy _________ that convert energy from one form to the other.

Answer 18

Transducers

Question 19

What is a corpuscle?

Answer 19

An oval shaped structure that consists of rings of connective tissue wrapped around a nerve cell ending

Question 20

What is generator potential (receptor potential)?

Answer 20

The change in potential across a receptor membrane

Question 21

How does a Pacinian corpuscle generate a nerve impulse?

Answer 21

When pressure is applied to the corpuscle it becomes deformed and pushes against the nerve ending, opening Na+ channels

Question 22

When a neurone is at rest, the inside of the cell is ___________ charged.

Answer 22

Negatively

Question 23

Why do larger diameter axons send faster impulses?

Answer 23

Have low SA:V so less ions leak out the axon making action potentials easier

Question 24

What is a local current?

Answer 24

The movement of Na+ along the axon, away from where they came in

Question 25

What is summation?

Answer 25

When the effect of neurotransmitters can be combined to make the membrane depolarisation reach a threshold allowing an action potential to be generated

Question 26

What is spacial summation?

Answer 26

When neurones converge each neurone releases a small amount of neurotransmitter and together will be enough to generate an action potential

Question 27

What is temporal summation?

Answer 27

When nerve impulses arrive in quick succession making action potential more likely because more neurotransmitter is in the synaptic cleft

Question 28

What is synaptic divergence?

Answer 28

When one neurone connects to many, allowing information to be dispersed to different areas of the body

Question 29

What is synaptic convergence?

Answer 29

When many neurones connect to one allowing information to be amplified

Question 30

Why can nerve impulses only be transmitted in one direction?

Answer 30

Because receptors for neurotransmitters are only on the postsynaptic membrane