Neural Communication

Question 1

Action potential

Answer 1

A brief reversal of the potential across the membrane of a neurone, causing a peak of +40mV compared to the resting potential of -60mV

Question 2

Positive feedback

Answer 2

A mechanism that increases a change taking the system further away from the optimum

Question 3

Resting potential definition

Answer 3

The potential difference across the membrane while the neurone is at resting

Question 4

Resting potential

Answer 4

About -60mV

Question 5

Pacinian corpuscle

Answer 5

A pressure sensor found on the skin

Question 6

Sensory receptors

Answer 6

Cells/sensory nerve endings that respond to a stimulus in the internal or external environment of the organism - can create action potentials

Question 7

Transducer

Answer 7

A cell that converts one form of energy into another

Question 8

What do most energy transducers do?

Answer 8

Convert one form of energy to another

Question 9

Stimulus

Answer 9

A change in the environment that elicits a response

Question 10

How do sensory receptors respond to a stimulus

Answer 10

Respond by creating a signal in the form of electrical signal

Question 11

What does a change in light intensity result in

Answer 11

Light sensitive cells (rods and cones) in the retina (sensory receptor) convert light to electrical signals

Question 12

What does a change in temperature result in?

Answer 12

Temperature receptors in the skin and hypothalamus detect the change and convert heat to electrical energy

Question 13

What does changes in pressure on the skin result in?

Answer 13

The Pacinian corpuscles in the skin detect the change and convert movement to electrical energy

Question 14

What does a change in sound result in?

Answer 14

Vibration receptors in the cochlea of the ear detect the change and convert movement to electrical energy

Question 15

What does a change of chemicals in the air result in?

Answer 15

Olfactory cells in epithelium lining the nose detect the presence of a chemical and create an electrical nerve impulse

Question 16

Describe the structure of the Pacinian corpuscles

Answer 16

• An oval shaped structure

- Consists of a series of concentric rings of connective tissue wrapped around the end of a nerve cell

Question 17

How does the Pacinian corpuscles detect the stimulus?

Answer 17

-When pressure on the skin changes this deforms the rings of connective tissue, which push against the nerve ending

Question 18

Energy transducer

Answer 18

Transforms one mode of energy into another e.g. Chemical to electrical

Question 19

What are neurones more specialised channels specific to?

Answer 19

Sodium and potassium

Question 20

Approximately what is the potential difference across a resting neurone?

Answer 20

-65 millivolts (mV)

Question 21

What is the cell membrane said to be when the cell is inactive?

Answer 21

Polarised (negatively charged inside compared to the outside)

Question 22

How many sodium ions are transported across the cell membrane for how many potassium?

Answer 22

3 sodium out for 2 potassium in

Question 23

What do cells associated with the nervous system have?

Answer 23

Specialised channel proteins e.g. Sodium channels are specific for sodium

Question 24

What will happen if protein channels are permanently open?

Answer 24

Ions will diffuse across the membrane until their concentrations on either side reach an equilibrium

Question 25

What happens across a membrane due to sodium channels being sensitive?

Answer 25

- As they are so sensitive to small movements across the membrane, when the membrane is deformed by the changing pressure the sodium channels open. - This allows sodium ions to diffuse into the cell producing a generator potential (receptor potential)

Question 26

What is the role of the sodium/potassium pump?

Answer 26

-When the channels proteins are shut it works to create a concentration gradient -

Question 27

How is a nerve impulse created?

Answer 27

By altering the permeability of the nerve cell membrane to sodium ions

Question 28

How is the creation of a nerve impulse achieved?

Answer 28

- By opening the sodium ion channels - As the sodium ion channels open, the membrane permeability is increased and sodium ions can move across the cell membrane down their concentration gradients into the cell - Movement of ions across the membrane creates a change in the potential difference across the membrane - Inside of cell becomes less negative (depolarisation)

Question 29

What happens if only a small stimulus is detected?

Answer 29

Only a few sodium channels will open

Question 30

The larger the stimulus.....

Answer 30

The more gated channels will open

Question 31

What happens if enough sodium gates are open?

Answer 31

Enough sodium ions will enter the cell, the potential difference across the cell membrane changes significantly and will initiate an impulse or action potential.

Question 32

Motor neurones

Answer 32

Neurones that carry an action potential from the CNS to the effector muscle

Question 33

Myelinated neurones

Answer 33

Has an individual layer of myelin around it. Myelin sheath

Question 34

Non-myelinated neurones

Answer 34

Has no individual layer of myelin

Question 35

Relay neurones

Answer 35

Join sensory neurones to motor neurones

Question 36

Sensory neurones

Answer 36

Neurones that carry an action potential from the sensory receptor to the CNS

Question 37

What does the cell body of all neurones contain?

Answer 37

Many mitochondria, a nucleus and ribosomes

Question 38

What is different about motor neurones?

Answer 38

- Motor neurones have their cell body in the CNS and have a long axon that carries an AP out to an effector

Question 39

What is different about sensory neurones to other neurones?

Answer 39

- Sensory neurones have a long dendron carrying the AP from the sensory receptor to the cell body, which is positioned just outside the CNS - Have a short axon carrying the AP into the CNS

Question 40

What is different about relay neurones to other neurones?

Answer 40

- Relay neurones connect the sensory and motor neurones together - Have many short dendrites and a short axon - No. Of dendrites and divisions of the axon is variable

Question 41

Structures that are the same in all neurones

Answer 41

- long so to transmit action potential over a long distance - cell surface membrane with many gated ion channels - sodium/potassium pump that uses ATP to actively transport ions - maintain a potential difference across the membrane - axon carries impulse away from cell body - axon surrounded by myelin sheath

Question 42

What are the advantages of myelination?

Answer 42

- Myelinated neurones can transmit AP much quicker, typically 100-120 ms-1 - Myelinated tend to be longer and can so carry APs further