Neural communication

Question 1

What is the function of neurons?

Answer 1

Speacalised nerve cells vital for transmitting electrical impulses quickly throughout the body (rapid transmission enables organisms to react to environmental changes)

Question 2

What are the three structural components of mammalian neurones?

Answer 2

Cell body = contains the nucleus and cytoplasmic organelles crucial in neurotransmitter production

Dendrons = short branches extending from cell body further dividing into highly branched dendrites to receive nerve impulses from many other neurons

Axon = singular long nerve fibre responsible for carrying impulses away from the body to other neurons or effectors

Question 3

What type of cells surround myelinated neuron membranes and what is their function?

Answer 3

Schwan cells
- their membranes form myelin sheath
- aid cell regeneration
- remove debris via phagocytosis

Question 4

What is the purpose of the myelin sheath relating to the cell axon?

Answer 4

Surrounds the axon acting as an insulator that prevents the passage of ions into or out of the axon at the regions it covers

Question 5

What is saltatory conduction?

Answer 5

A nerve impulse is conducted rapidly when an electrical impulse ‘jumps’ between gaps in the myelin sheath (nodes of Ranvier) increasing transmission speed

Question 6

What is the function of a sensory neuron?

Answer 6

Carries impulses from sensory receptors to the CNS

Question 7

What is the structure of a sensory neuron?

Answer 7

Cell body between dendron and axon

Question 8

What is the function of a motor neron?

Answer 8

Carries impulses from the CNS to effectors

Question 9

What is the structure of a motor neuron?

Answer 9

Cell body then axon then dendron

Question 10

What is the function of a relay neuron?

Answer 10

Carries impulses within the CNS between other neurons

Question 11

What is the structure of a relay neuron?

Answer 11

Numerous short axons and dendrons

Question 12

What is the typical pathway of an impulse?

Answer 12

• receptor
• sensory neuron
• relay neuron
• motor neuron
• effector

Question 13

What is a sensory receptor and how does it act as a transducer?

Answer 13

Speacalised cells that detect stimuli from the environment

Transducer = converts one form of energy into another, converts the stimuli energy into a nerve impulse passed to the CNS

Question 14

What type of stimulus do photoreceptors detect and where are they located?

Answer 14

Detect = light stimulus

Located = eyes

Question 15

What type of stimulus do chemoreceptors detect and where are they located?

Answer 15

Detect = chemicals

Located = nose, tongue, blood vessels

Question 16

What type of stimulus do mechanoreceptors detect and where are they located?

Answer 16

Detect = pressure/movement

Located = skin, muscles, inner ear

Question 17

What type of stimulus do thermoreceptors detect and where are they located?

Answer 17

Detect = temperature

Located = skin

Question 18

What are the stages of receptor cells completing their function?

Answer 18

1) at rest receptor cell surface membrane has voltage across it due to differences in ion conc in and out of cell (resting potential)

2) when stimuli detected cell surface membrane becomes more permeable resulting in more ions able to enter and leave (NA+)

3) alters membranes voltage creating generator/receptor potential

4) larger stimuli results in bigger change in voltage producing larger generator potential

5) if generator potential reaches threshold level it triggers an action potential which is an electrical signal sent along a neuron

Question 19

What is the pacillian corpuscle and what does it do?

Answer 19

Mechanoreceptors in the skin

Detect = pressure + vibrations

Question 20

What is the structure of the pacillian corpuscle?

Answer 20

• end of sensory neuron wrapped in layers of connective tissue (lamelle)
• lamelle allow it to detect pressure and vibration

Question 21

What happens when the pacillian corpuscle is stimulated?

Answer 21

1) lamelle deform pressing on the sensory neuron ending

2) stretches the neurons membrane causing it to change shape

3) opens stretch mediated NA+ ion channels in the membrane increasing it’s permeability to NA+

4) NA+ diffuses into the neuron depolarising it resulting in a generator potential

5) if this signal reaches the threshold an action potential is triggered