Neurons

Question 1

What is a dendrite

Answer 1

short extension of the cytoplasm that carry nerve impulses/messages into the cell body

Question 2

What is an Axon

Answer 2

long extensions of cytoplasm that carry messages/nerve impulses AWAY from cell body

Question 3

What is a Myelin sheath

Answer 3

Fatty material that covers axon

Axons without Myelin sheath- unmyelinated
Axons with Myelin sheath- myelinated fibres

Question 4

What is a nerve fibre

Answer 4

Long extension of a nerve cell

Question 5

What is an axon terminal

Answer 5

The end of an exon divides into smaller branches. Each of these branches are named axon terminals

Question 6

What are Nodes of Ranvier

Answer 6

Intervals along the axon where there are gaps in the myelin sheath

Question 7

What are Schwann cells

Answer 7

Cells outside the brain and spinal chord that from the myelin sheath

Question 8

Functions of the Myelin sheath

Answer 8

• Acts as insulator
• Protects axon from damage
• Speeds up movement of nerve impulses along the axon

Question 9

What is neurilemma

Answer 9

Outermost coil of Schwann cell that helps in repair of injured fibres

Question 10

What is a synapse

Answer 10

junction between an axon terminal of one nerve to the dendrite of another

Question 11

What is a neurotransmitter

Answer 11

chemicals carried across the synapse that carry messages

Question 12

What is a neuromuscular junction?

Answer 12

synapse where axon meets a skeletal muscle cell

Question 13

What is a Sensory/Afferent neuron

Answer 13

carries messages from receptors on skin/sense organs to the CNS

Question 14

What is a Motor/Efferent neuron

Answer 14

carries messages from CNS to the effectors

Question 15

What are Interneurons

Answer 15

link between sensory and motor neurons

Question 16

Describe transmitton across a synapse

Answer 16

1) When nerve impulses reach axon terminal, activated voltage gated calcium ion channels
2) As there is a high concentration of calcium ions in the extracellular fluid, they flow into the cell
3) Causes sympathetic vesicles to fuse with the membrane, releasing neurotransmitters (exocytosis)
4) Neurotransmitters diffuse across gap and attach to receptors on the membrane of the next neuron
5) Stimulates ligand-gated protein channels to open, allows for influx sodium ions and incites an action potential
6) Neurotransmitters are reabsorbed by the presynaptic membrane, and degraded by enzymes

Question 17

What are the 4 different types of receptors

Answer 17

• Osmoreceptors
• chemoreceptors
• touch receptors
• thermo receptors
• pain receptors

Question 18

What is depolarisation

Answer 18

started by a stimulus from another neuron to a receptor. This stimulus opens sodium channels

Question 19

What is repolarisaton

Answer 19

The closing of sodium channels and opening of potassium channels. Flow of sodium ions into cell decreases + flow of potassium ions out of cell increases = making cell more negative than outside, reducing action potential

Question 20

Action potential along nerves

Answer 20

Action potential in one area of membrane simulates action potential in adjacent area. Therefore, potential moves along the nerve fibres (nerve impulse)

Question 21

What is action potential

Answer 21

Rapid depolarisation and repolarisation of cell membrane

Question 22

What are reflexes

Answer 22

Rapid, automatic changes to a change in environment