Neuronal Communication 5.3 -by J + M

Question 1

Name 4 receptors and state where they are found/ what stimulus they receive

Answer 1

Mechanoreceptors-skin/ touch
Photoreceptors-eyes/ light
Chemoreceptors-aorta and carotid artery/ pH
Thermoreceptors-skin, hypothalamus/ temperature

Question 2

Describe the structures of the three different types of neurons

Answer 2

SENSORY- receptor, dendron, cell body, axon

RELAY- dendrites, cell body, axon, pre-synaptic terminal

MOTOR-dendrites around cell body, axon with nodes of ranviers, axon terminal

https://www.google.co.uk/url?sa=i&url=https%3A%2F%2Fwww.tutor2u.net%2Fpsychology%2Freference%2Fbiopsychology-sensory-relay-and-motor-neurons&psig=AOvVaw3G4Z8kWJeCEtSoE2mu9xbK&ust=1581594887940000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCNCyrLX6y-cCFQAAAAAdAAAAABAE

Question 3

What value is the resting potential

Answer 3

-60mv

Question 4

What value is the threshold potential

Answer 4

-50mv

Question 5

At what value does the membrane become depolarised

Answer 5

+40mv

Question 6

What value is the membrane REpolarised?

Answer 6

-70mv

Question 7

What is it called if the value is more negative than -70mv

Answer 7

HYPERpolarised

Question 8

When is the axon polarised and what does it mean?

Answer 8

At resting potential, the axon is polarised; meaning that inside the membrane is more negative than outside

Question 9

Name 5 specialised features of NERVES

Answer 9

Long
Voltage gated ion channels
NA+/K+ co-transporter pump
Potential difference of -70mv inside compared to outside
All organelles in cell body

Question 10

What is a pacinian corpuscle?

What is its structure?

Answer 10

A pressure sensor that detects changes in pressure on the skin.
-oval-shaped
-concentric rings of connective tissue wrapped around the end of the nerve cell
When pressure deforms the rings they push against the nerve ending. If the pressure is constant, they stop responding.

Question 11

What are transducers?

Answer 11

A cell which converts one form of energy into another

Question 12

What is a generator potential?

Answer 12

The depolarization of the membrane of the receptor cell

Question 13

How is the resting potential created?

Answer 13

Sodium/potassium pump actively transports 3Na+ out of the cell for 2K+ going into the cell.

This means that the charge inside the cell is lowered compared to the charge outside of the cell.

This is increased by potassium channels which allow the build-up of 2K+ to move out of cell down the concentration gradient, making the cell even more negative.

Negative anions reduce the resting potential further

Question 14

What does it mean when the neurone is polarised?

Answer 14

It is at its resting potential, which is -60Mv, or the inside of the neurone is more negative than the outside.

Question 15

What is depolarisation?

Answer 15

When the inside of the cell becomes less negative compared to the outside.

Question 16

How does depolarization occur?

Answer 16

A stimulus (change in energy levels of the environment) cause sodium channels open, causing sodium to move down the concentration gradient, into the cell making it less negative and depolarised.

Question 17

How is an action potential created?

Answer 17

When a stimulus creates a generator potential, sodium channels open to make the neurone less negative.
If enough generator potentials combine, enough sodium will enter the neurone to raise the potential above the threshold potential and trigger an action potential.

This triggers the voltage-gated sodium ion channels to open and sodium floods in raising the potential to +40

Question 18

Summarise the stages of the action potential in 5 steps.

Answer 18

1) Sodium-ion channels open and some sodium flows down concentration gradient into the neurone
2) The Neurone becomes depolarised, it reaches the threshold potential (-50Mv) when the voltage-gated ion channels open
3) Sodium comes flooding in raising the potential to +40 Mv inside the cell. Positive feedback causes more VG sodium channels to open
4) The Sodium ion channels close and potassium channels open, so K+ comes flooding out of the cell, lowering the potential back down.
5) Potential overshoots making the cell hyperpolarised.

Question 19

How is an action potential passed down a neurone?

Answer 19

The movement of sodium into the neurone causes the VG sodium channels to open.

This increases the concentration of sodium further, and sodium diffuses down the neurone to where concentrations are lower. This is called a Local Current.

This raises the Potential of that section, causing the VG gated sodium channels in that section to also open.

Question 20

What is a Local current?

Answer 20

The sideways movement of sodium along a neurone.

Question 21

What is saltatory conduction?

Answer 21

When the action potential jumps between nodes of Ranvier, as ions cant pass through the myelin sheath.

Question 22

How and why does saltatory conduction occur?

Answer 22

For an action potential to be passed along a neurone, ions need to pass through the cell membrane.

As ions cant pass through the fatty myelin sheath, this can only occur at the nodes of Ranvier.

This means the sodium ions have to diffuse from one node to another.

This means the action potential appears to jump from one node to the next.

Question 23

What is the advantage of saltatory conduction?

Answer 23

Forcing the action potential to jump between nodes enables faster transmission.

This is why myelinated neurones can transmit a signal faster than non-myelinated.

Question 24

How does our brain detect the different intensities of stimuli?

Answer 24

When a stimulus is at a higher intensity, more sodium channels are opened in the sensory receptor.

This produces more generator potentials, so there are more frequent action potentials.

Your brain interprets a higher frequency of action potentials as an increase in the intensity of the stimuli.

Question 25

What is the name of the gap between two synapses?

Answer 25

Synaptic cleft

about 20 nm wide

Question 26

What is a cholinergic synapse?

Answer 26

A Synapse which uses acetylcholine as a neurotransmitter.

Question 27

What is a neurotransmitter?

Answer 27

A chemical used as a signalling molecule between neurones in a synapse.