Neurones

Question 1

what is the role of neurones?

Answer 1

• transmit electric impulses rapidly around the body so that an organism can respond to changes in its internal and external environmenet

Question 2

why are there several types of neurones in a mammal?

Answer 2

• they work together to carry information detected by a sensory receptor to the effector to carry out an appropriate response

Question 3

what are the features of neurone?

Answer 3

• cell body
• dendrons/dentrites
• axons

Question 4

what features do a sensory and motor neurone have but relay don’t?

Answer 4

• node of ranvier
• myelin sheath

Question 5

what is the structure of a cell body?

Answer 5

• contains nucleus surrounded by cytoplasm
• large numbers of ER and mitochondria which are involved in the production of neurotransmitters

Question 6

what is a neurotransmitter?

Answer 6

• chemical involved in communication across a synapse between adjacent neurones OR a neurone and a muscle

Question 7

what is the structure of a dendron?

Answer 7

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

Question 8

what is the structure of an axon?

Answer 8

• they are singlular, elongated nerve fibres
• these fibres transmit impulses AWAY from the cell body
• the fibre is cylindrical in shape consisting of very narrow region of cytoplasm surrounded by a plasma membrane

Question 9

what are the 3 types of neurones?

Answer 9

• sensory
• motor
• relay

Question 10

what is a sensory neurone?

Answer 10

• transmit impulses from a sensory receptor cell to a relay neurone, motor neurone, or the brain
• they have ONE dendron
• they have ONE axon

Question 11

what is a relay neurone?

Answer 11

• transmit impulses between neurones
• i.e. between sensory and motor neurones
• multiple short axons and dendrons

Question 12

what is a motor neurone?

Answer 12

• transmit impulses from a relay or sensory neurone to an effector
• i.e a muscle gland
• they have one long axon
• multiple short dendrites

Question 13

what is the typical electrical impulse pathway in nervous responses?

Answer 13

receptor -> sensory neurone -> relay neurone -> motor neurone -> effector cell

Question 14

what specialised cells produces layers of membrane for a myelin sheath?

Answer 14

• Schwann cells

Question 15

what happens each time a myelin sheath grows around the axon?

Answer 15

• a double layer of phospholipid bilayer is laid out

Question 16

what is the purpose of a myelin sheath?

Answer 16

• act as an insulating layer
• allows myelinated neurones to conduct an electrical impulse at a faster speed

Question 17

how quickly can myelinated neurones transmit impulses?

Answer 17

• approximately 100 m/s

Question 18

how slowly can non-myelinated neurones transmit impulses?

Answer 18

• approximately 1m/s

Question 19

what is between each adjacent schwann cell?

Answer 19

• a small gap
• known as the nodes of ranvier

Question 20

what is the purpose of a sensory receptor?

Answer 20

• convert the stimulus they detect into a nerve impulse (act as a transducer)

Question 21

what are the four types of sensory receptors?

Answer 21

• mechanoreceptor
• chemoreceptor
• thermoreceptor
• photoreceptor

Question 22

what is the mechanoreceptor?

Answer 22

• stimulus: pressure and movement
• example: pacinian corpuscle
• detected by skin

Question 23

what is a chemoreceptor?

Answer 23

• stimulus: chemicals
• example: oilfactory receptor
• detected by nose

Question 24

what is a thermoreceptor?

Answer 24

• stimulus: heat
• example: end-bulbs of Krause
• detected by tongue

Question 25

what is a photoreceptor?

Answer 25

• stimulus: light
• example: cone cell (detects different light wavelengths)
• detected by eye

Question 26

what are panician corpsucles?

Answer 26

• specific sensory receptors
  -detect mechanical pressure
• located deep within your skin i.e. fingers and soles of feet

Question 27

where is the end of a sensory neurone located in a pacinian corpuscle?

Answer 27

• the centre
• surrounded by layers of connective tissue where each layer is separated by gel

Question 28

what is within the membrane of the neurone with the pacinian corpuscle?

Answer 28

• stretch-mediated sodium channel

Question 29

how are sodium ion channels adapted?

Answer 29

• they change shape
• as a result the sodium permeability will also change

Question 30

how does a pacinian corpuscle convert mechanical pressure into a nervous impulse?
( 5 STEPS)

Answer 30

1. at resting state , the stretch-mediated sodium channel in the sensory neurones membrane are too narrow to pass through them (resting state)
2. when there is pressure applied, the corpuscle changes shape so the membrane surrounding the neurone stretches
3. sodium ion channels widen so sodium can diffuse into the neurone
4. the influx of positive sodium ions changes the potential of the membrane and becomes depolarised (resulting in a generator potential)
5. the generator potential creates an action potential that passes along the sensory neurone