Neural Communication - Topic 13

Question 1

What is a voluntary response?

Answer 1

1. Stimulus - change in environment (e.g. change in pressure/temp/smell)
2. Sensory Receptors - detect stimulus (e.g. pain/thermo receptors in skin, eyes, nose, ears)
3. Sensory Neuron
4. CNS - spinal cord/brain - coordinates response, sending electrical impulse to effector
5. motor neuron
6. effectors - e.g. muscle or gland (producing a chemical response)

Question 2

Structure of a Neurone - What’s a cell body?

Answer 2

• Contains the nucleus surrounded by cytoplasm, large amounts of endoplasmic reticulum and mitochondria, involved in the production of neurotransmitters.
• in sensory neurone, cell body will be in-between the dendron and axon
• in motor neuron, cell body will be at the start of the axon (as MN doesn’t have a dendron)

Question 3

Structure of a Neurone - What’s a dendron?

Answer 3

• are short extensions which come from the cell body
• extensions divide into smaller and smaller branches known as dendrites
• responsible for transmitting electrical impulses towards cell body

Question 4

Structure of a Neurone - What’s an axon?

Answer 4

• are singular, elongated nerve fibres that transmit impulses away from the cell body.
• fibres can be very long, e.g. those that transmit impulses from the tips of toes and fingers to spinal cord
• the fibre is cylindrical in shape consisting of very narrow region of cytoplasm surrounded by a plasma membrane

Question 5

Types of neurone - what’s a sensory neurone?

Answer 5

• transmit impulses from a sensory receptor cell to a relay neurone, motor neurone or brain
• Have one dendron, which carries the impulse to the cell body
• Have one axon, which carries the impulse away from cell body

Question 6

Types of Neurone - what’s a motor neurone?

Answer 6

• transmit impulses from a relay neurone or sensory neurone to an effector (e.g. muscle or gland)
• Have one long axon and many short dendrites

Question 7

Myelinated neurone - how is the myelin sheath formed?

Answer 7

• formed by specialised cells known as Schwann cells, which wrap themselves around the axon
• lipid rich, helps insulate the axon, speeding up impulses

Question 8

Myelinated neurone - what are the nodes of Ranvier?

Answer 8

• uninsulated sections along the axon in myelin sheath.
• action potentials can only occur here, this is because they ‘jump’ from node to node