Neurons

Question 1

What is special about nervous tissue?

Answer 1

• It is densely packed with cells such as neurons (less than 25% extracellular space).

Question 2

What surround the neurons in the nervous system?

Answer 2

Glial cells.

Question 3

What is the function of glial cells?

Answer 3

Provide support, nutrition, insulation and aid synaptic transmission in the nervous system.

Question 4

What is the lifespan of neurons in the cerebral cortex?

Answer 4

They will live as long as you do (most of the time).

Question 5

Most neurons are amitotic, what does this mean?

Answer 5

Once they specialise and take their given roles they lose the ability to divide, meaning they are irreplaceable.

Question 6

What makes neurons irreplaceable?

Answer 6

They are amitotic (cannot divide once specialised so the number is fixed).

Question 7

Describe the metabolic rate of neurons:

Answer 7

Very high, they require an abundant supply of glucose and oxygen, (25% of daily calories are consumed by the brains activity).

Question 8

What is the basic structure of a neuron?

Answer 8

• Cell body,
• Dendrites,
• Axons,

Question 9

What is the function of the cell body?

Answer 9

Contains cellular components found in typical cells such as mitochondria, ribosomes, cytoplasm, nucleus, ER’s and golgi.

Question 10

What is the function of the dendrites?

Answer 10

Receive messages from other neurons and allow them to travel to the cell body.

Question 11

What is the function of the axon?

Answer 11

Carry electrical impulses from the cell body to the axon terminals, (where neurotransmitters are released into the synapse).

Question 12

What are the branch-like structures protruding from the cell body.

Answer 12

Dendrites.

Question 13

Where is the nucleus of the nervous cell?

Answer 13

In the cell body.

Question 14

How is the dendrite adapted to increase Surface Area?

Answer 14

They have small dendritic spines to increase SA.

Question 15

What are the long tube-like structures that protrude from the cell body?

Answer 15

Axons.

Question 16

Bipolar neuron cells are rare, where might they be found?

Answer 16

In the retina of the eye.

Question 17

Where would unipolar neuron cells be found?

Answer 17

In sensory receptors.

Question 18

What is the function of a sensory neuron?

Answer 18

To transmit impulses from sensory receptors towards the CNS.

Question 19

Most sensory neurons are what ____polar?

Answer 19

Uni(polar) as they transmit electrical impulses one way.

Question 20

What is the function of a motor neuron?

Answer 20

To move and impulse from the CNS to the rest of the body.

Question 21

Motor neurons are mostly _____polar?

Answer 21

Multi(polar) as they

Question 22

What is the fatty layer surrounding the axon?

Answer 22

The myelin sheath.

Question 23

Which type of neuron transmits impulses towards the CNS?

Answer 23

Sensory receptors.

Question 24

What is the function of the nucleus?

Answer 24

Controls cell function and contains all cellular DNA.

Question 25

What is the function of the Schwann cell?

Answer 25

To produce the myelin that will form the sheath.

Question 26

What part of the neuron acts as insulation to minimise the dissipation of electrical impulses?

Answer 26

The myelin sheath.

Question 27

What part of the neuron speeds up electrical transmission?

Answer 27

The myelin sheath.

Question 28

What are the functions of the myelin sheath?

Answer 28

To speed up electrical transmission by minimising the dissipation of electrical impulses.

Question 29

What biological molecule is myelin?

Answer 29

Lipid (fat).

Question 30

What are the gaps in the myelin sheath called?

Answer 30

The nodes of ranvier.

Question 31

Relay neurons are mostly ___polar:

Answer 31

Bi(polar), as they act as a messenger between other neurons.

Question 32

Which type of neurons are found in receptors such as the eyes, ears, tongue and skin?

Answer 32

Sensory neurons.

Question 33

Match the following:

• Unipolar
• Bipolar
• Multipolar
• Relay
• Motor
• Sensory

Answer 33

Sensory = Unipolar.
Relay = Bipolar.
Motor = Multipolar.

Question 34

Where are relay neurons found?

Answer 34

Between the sensory and motor neurons, in the brain and spinal cord.

Question 35

What is the function of the relay neurons?

Answer 35

To allow other neurons to speak to each other, a messenger (bipolar).

Question 36

What happens when the motor neurons are stimulated?

Answer 36

They send signals to the muscles causing them to contract and movement occurs.

Question 37

Which type of neuron is directly responsible for muscle movement?

Answer 37

Motor neurons.

Question 38

Describe the length of an axon:

Answer 38

The length has a high variation, can be very small or large enough to be seen by the human eye.

Question 39

How do the nodes of ranvier speed up transmission?

Answer 39

They force the impulse to ‘jump’ across the gaps in the axon.

Question 40

Roughly how many neurons does a human have and how many of these are in the brain?

Answer 40

Roughly 100 billion neurons, 80% of which are located in the brain (80 billion).

Question 41

What is the general variation in size for a neuron?

Answer 41

Less than a millimetre to a metre long.

Question 42

How quickly is information passed through neurons?

Answer 42

Information can travel through neurons at speeds exceeding 100 meters per second.