5.1.3- Neuronal Communication

Question 1

what are sensory receptors?

Answer 1

specialised cells that detect stimuli

Question 2

what are sensory receptors known as and why?

Answer 2

ENERGY TRANSDUCERS
they convert different forms of energy into electrical energy

Question 3

what are the 4 types of sensory receptors and what is their stimulus?

Answer 3

1- Mechanoreceptor- pressure and movement
2-Chemoreceptors- chemicals
3-Thermoreceptors- heat
4- Photoreceptors- light

Question 4

what is an example of a mechanoreceptor?

Answer 4

Pachinian Corpuscle, in the skin

Question 5

what is an example of a chemoreceptor?

Answer 5

Olfactory receptor in the nose

Question 6

what is an example of a thermoreceptor?

Answer 6

End-bulbs of Kraus, in the tongue

Question 7

what is an example of a photoreceptor?

Answer 7

Cone cells in the eye

Question 8

what is the function of a sensory neurone?

Answer 8

carry impulses from receptors to the CNS

Question 9

what is the function of a relay neurone?

Answer 9

connect the sensory and motor neurone, present in the CNS

Question 10

what is the function of a motor neurone?

Answer 10

carry impulses from CNS to effectors

Question 11

when in resting potential, what is the neurone cell membrane described as?

Answer 11

polarised

Question 12

what is resting potential?

Answer 12

the potential difference across the neurone cell mebrane while the neurone is at rest

Question 13

what happens during resting potential of neurones?

Answer 13

-3 sodium ions are transported out
-2 potassium ions are transported in
-the sodium-potassium pump controls this
-the sodium ion channels are closed so that sodium cannot come back into the neurone, while the potassium ion channels remain open so they can move back out
-this leads to the inside being negative and the outside being positive, with a difference of around -70mV

Question 14

what is action potential?

Answer 14

the depolarisation of the neurone cell membrane, so the inside is more positive than the outside, occurring when the cell is active

Question 15

what happens during action potential of neurones?

Answer 15

-sodium ion channels open, and potassium ion channels close
-this causes a rush of sodium ions into the neurone, causing the flip of charge
-the change becomes around +40 mV

Question 16

what occurs during repolarisation of neurones?

Answer 16

-the Na ion channel closes but the K ion channels open, which leads to a flood of K entering the neurone
-however, this can lead to overpolarisation, as the inside will become too negative
-therefore, the sodium-potassium pump works to get it back to normal

Question 17

what is a pacinian corpsucle?

Answer 17

a specific sensory receptor that detects mechanical pressure

Question 18

how does a pacinian corpuscle convert mechanical pressure into a nervous impulse?

Answer 18

-normal state, PC has a resting potential
-stretch-mediated sodium channels in sensory neurones membrane are too narrow to allow Na ions to pass through
-pressure is applied, so the PC changes shape, membrane stretches
-Na ion channels widen so Na ions diffuse in
-membrane becomes depolarised, resulting in a generator potential
-generator potential if reaching threshold potential creates an action potential

Question 19

what is generator potential?

Answer 19

the transmembrane potential difference produced by activation of a sensory receptor

Question 20

what is habituation?

Answer 20

-body gets used to a particular ‘feeling’ if the body receives the stimulus over a long period of time.
—> less stimulation of corpuscle over time

Question 21

what is a nerve impulse?

Answer 21

a wave of depolarisation followed by a wave of repolarisation

Question 22

how is a nerve impulse transmitted?

Answer 22

-when an action potential is set up, the influx of sodium ions set off the transmission along the neurone
-the increase of these ions set up a local current
-these ions then diffuse sideways along the neurone, causing voltage-gated sodium channels to open further down the neurone, setting off another action potential
-local current moves down as a wave of depolarisation, followed by the nerve impulse (wave of repolarisation)

Question 23

how is a nerve impulse transmitted?

Answer 23

-when an action potential is set up, the influx of sodium ions set off the transmission along the neurone
-the increase of these ions set up a local current
-these ions then diffuse sideways along the neurone, causing voltage-gated sodium channels to open further down the neurone, setting off another action potential
-local current moves down as a wave of depolarisation, followed by the nerve impulse (wave of repolarisation)

Question 24

what does a more intense stimulus mean in terms of frequency?

Answer 24

a high frequency of nerve impulses

Question 25

what is a myelinated neurone?

Answer 25

when a neurone has a fatty sheath wrapped around it, providing electrical insulation, along side layers of membrane, Schwann cells, nodes of ranvier

Question 26

what is the speed of conduction of a myelinated neurone?

Answer 26

FAST= 120m/s
known as saltatory conduction

Question 27

what is a unmyelinated neurone?

Answer 27

when several neurones share one lossely wrapped schwann cell, no nodes of ranvier and no fatty sheath, and so action potential moves along in a wave with no jumping

Question 28

what is the speed of conduction of an unmyelinated neurone?

Answer 28

SLOW= 20m/s

Question 29

what is the advantages of myelinated neurones?

Answer 29

-action potential is transmitted more quickly
-rapid response
-saltatory conduction (AP jumps from node to node)
-insulated parts stay resting

Question 30

what is a synapse?

Answer 30

the junction between two neurones (pre-synpatic and post-synpatic)

Question 31

what allows nerve impulses to cross the synpatic cleft?

Answer 31

neurotransmitters

Question 32

what is a cholinergenic synapse?

Answer 32

a synapse which makes and releases acetylcholine.

Question 33

describe the movement of nerve impulses across a synapse in
8 steps?

Answer 33

1- AP moves down neurone until synpase is reached
2-Within the synpatic knob, acetylcholine is released and transported in vesicles
3- Calcium ions diffuse into the neurone, causing the vesicles to move towards the pre-synaptic membrane.
4-The vesicles then fuse with the membrane (exocytosis), and so acetylcholine diffuses acrosss the synapse towards the post-synaptic membrane
5-the sodium ion channels are attached to a receptor, and these open , allowing the ions to diffuse in
6-Acetylcholine binds to the receptor.
7-This means that the enzyme, acetylcholinesterase is left within the synaptic cleft
8-The enzyme breaks down, with choline moving back into the pre-synaptic neurone, where it then combines with acetylcoenzymeA to create acetylcholine.

Question 34

what are the two types of summation?

Answer 34

-spatial= occurs when a number of pre- connect with one post-, so neurotransiters build up high enough to trigger AP in post-.
-tempora;= occurs when a single pre- releases neurotransmitter to AP over a short period of time, so it builds up in synpase until sufficient to trigger an AP