Nervous systems

Question 1

What is a nerve impulse

Answer 1

Self propagating wave of electrical disturbance travelling along surface of axon membrane

Question 2

What is resting potential

Answer 2

Potential difference across he axon when a neuron is at rest

Question 3

What are the charges of inside and outside of an axon

Answer 3

Inside is negatively charged relative to outside

Question 4

What is an axon

Answer 4

The long fibre in a neurone tat conducts impulses away from the cell body

Question 5

What is the purpose of the myelin sheath

Answer 5

Made of schwaan cells that insulates the axon, shields the axon from surrounding tissue fluid and insulates it from other neurones

Question 6

What is depolarisation

Answer 6

A rapid temporary reversal of the resting membrane potential

Question 7

What is re polarisation

Answer 7

A return to the resting membrane potential

Question 8

How is resting potential maintained?

Answer 8

Membrane more permeable to potassium ions and less to sodium ions
Sodium ions are actively transported out and potassium ions pumped in

Question 9

How does MS lead to slower responses to stimuli?

Answer 9

Myelin sheath broken down
Impulse is unable to jump from node to node
More depolarisation over length of membrane

Question 10

How does a lower temperature lead to slower nerve impulse conduction?

Answer 10

Ions have less kenetic energy and therefore they diffuse more slowly

Question 11

What factors affect speed of nerve impulse conduction

Answer 11

Myelination
Diameter of axon
Temperature

Question 12

What is the absolute refractory period?

Answer 12

After generation of an action potential
Voltage gated sodium channels are inactivated
They cannot respond to further stimulus

Question 13

What is a synapse?

Answer 13

Junction between neurones

Question 14

Where are neurotransmitters made and where are they stored?

Answer 14

Made in pre synaptic neurones

Stored in synaptic vesicles

Question 15

What is summation?

Answer 15

Arrival of multiple action potentials leading to a build up of neurotransmitter

Question 16

Why does depolarisation happen?

Answer 16

Sodium ion gates open

Question 17

Why can another action potential not be generated once one has just been generated?

Answer 17

Membrane more impermeable to sodium ions
Sodium ion cannot enter axon
Membrane becomes more negative than resting potential

Question 18

Explain why a neurotransmitter (e.g. acetylcholine) can only bind with one type of receptor protein in the postsynaptic membrane.

Answer 18

Unique shape of receptor protein / binding site
Due to (tertiary) structure of protein molecule

Question 19

What is the role of calcium ions (Ca2+) in synaptic transmission?

Answer 19

Cause vesicles to move to presynaptic membrane

Question 20

How is an action potential generated?

Answer 20

Sodium ion channels open;

Allowing rapid influx of sodium ions

Question 21

How does an increase in exercise cause an increase in heart rate?

Answer 21

Chemoreceptors detect rise in PH sends impulse to medulla. More impulses to SAN by sympathetic nervous system.

Question 22

DDT binds to sodium channels, and consequently channels remain open, how does this kill?

Answer 22

Neurones remain depolarised

No action potentials generated

Question 23

What does the SAN do?

Answer 23

Sends waves of excitation through the atria initiating the heart beat

Question 24

What delays the contraction of the ventricles?

Answer 24

Non- conductive tissue prevents electrical impulse from reaching ventricles
Electrical impulse forced via AVN

Question 25

Why is it important that there is a delay before the contraction of the ventricles?

Answer 25

Allows the atria to fully contract and empty

Question 26

Why does the left ventricle have the highest blood pressure and why is this important?

Answer 26

It has the most cardiac muscle so it contracts at a higher force which is important as it pumps blood to the whole body

Question 27

What is the role of the Purkyne tissue and the bundle of his?

Answer 27

Conduct the electrical impulse

Question 28

What is the effect of adrenaline on heart muscle?

Answer 28

Beats faster | Beats stronger : myoctyes contract with greater force

Question 29

How does adrenaline increase heart rate?

Answer 29

It binds to specific receptors on the membranes of cells in the SAN

Question 30

What do baroreceptors detect?

Answer 30

Change in pressure

Question 31

Response to high blood pressure in the heart

Answer 31

Detected by baroreceptors Then via parasympathetic Releases acetylcholine

Question 32

How are the parasympathetic and sympathetic nervous systems antagonistic?

Answer 32

If one system contracts a muscle then the other relaxes

Question 33

The sympathetic nervous system does what to an activity?

Answer 33

Speeds up activity

Question 34

The parasympathetic nervous system does what to an activity?

Answer 34

Inhibits effectors and so slows down any activity

Question 35

Changes to heart rate are controlled by which region of the brain?

Answer 35

Medulla oblongata

Question 36

What do rods detect in the eye?

Answer 36

Light vs dark

Question 37

What do cones detect in the eye?

Answer 37

Wavelength i.e colour

Question 38

Describe a simple reflex arc

Answer 38

Stimulus-receptor-sensory neurone-motor neurone- effector- response

Question 39

What are the types of photoreceptors in the eye?

Answer 39

Cones and rods

Question 40

Why do rod cells provide low visual acuity?

Answer 40

More than one rod cell shares the same synapse with a biopolar cell. As a result multiple rods need to be stimulated to give a generator potential

Question 41

Why do cone cells provide good visual acuity?

Answer 41

each cone cell has its own synapse via a bipolar neurone connecting to the optic nerve

Question 42

The speed of an action potential depends on?

Answer 42

Presence or absence of a myelin sheath Diameter of an axon Temperature

Question 43

What is the refractory period?

Answer 43

A period where the neuron cannot become excited as sodium ion channels enter a recovery stage

Question 44

Why is the refractory period important

Answer 44

Prevents action potentials travelling in the wrong direction

Question 45

What are some of the roles of synapses?

Answer 45

Prevent action potentials travelling in the wrong direction Amplify the effects of low frequency action potentials Inhibitory or excitory

Question 46

What happens when an action potential reaches a synapse?

Answer 46

Presynaptic membrane depolarises Ca2+ channels open Calcium ions diffuse into presynaptic neurone

Question 47

Roles of calcium ions in transmission across a synapse?

Answer 47

Causes the fusion of vesicles filled with neurotransmistter with presynaptic membrane

Question 48

Role of neurotransmitter in transmission across a synapse

Answer 48

Released into synaptic cleft Binds to receptors in the post synaptic membrane which stimulates the opening of Na+ channels allowing Na+ ions to enter neurone

Question 49

What happens to acetylchloline after an action potential has been generated?

Answer 49

Acetylchloinesterase hydrolyses it and it diffuses back into presynaptic membrane where it can be reused and prevents continous generation of an action potential

Question 50

Why is the response in heart beat less in diabetic rats?

Answer 50

``` Damage to autonomic nervous system Pressure receptors dont work as well Damage to medulla Change in number of impulses to medulla Damage to sympathetic system so doesnt speed up enough ```