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Biology > Nervous Coordination- Paper 2 > Flashcards

Nervous Coordination- Paper 2 Flashcards

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1
Q

What are the three things that the nervous system involves

A
  1. Detection of stimuli by receptors
  2. Transmission of nerve impulses by neurones
  3. Response by effectors
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2
Q

Provide a definition for what the nervous system entails

A

It provides a rapid response to stimuli and involves the transmission of electrical impulses along neurones, and chemical transmission across synapses between the neurones

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3
Q

What are the two major divisions of the nervous system

A

Central nervous system- the brain and spinal chord
Peripheral nervous system- nerves that originate from brain and spinal chord

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4
Q

What other two systems can the nervous system be divided into in terms of response

A

Voluntary nervous system, under voluntary conscious control and includes muscular and skeletal system
Autonomic nervous system which is involuntary or subconscious

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5
Q

What are the two parts of the autonomic system

A

Sympathetic- fight or flight, speeds up heart rate or blood pressure
Parasympathetic- slows down heart rate or blood pressure

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6
Q

What is a neurone and list the three different types

A

Specialised cells that are adapted to their function which is to carry electrical impulses from one part of the body to the next

Sensory, ralay and motor neurone

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7
Q

explain what a dendrite is

A

many thin extensions that carry impulses towards the cell body- receive impulses towards the cell body- receive impulses from other nerve cells

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8
Q

explain what a cell body is

A

groups of ribosomes which form neurotransmitters (proteins that transmit signals across from one neurone to the next)

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9
Q

explain what an axon is

A

very long extension from the cell body that transmits impulses away from the cell body to the axon endings

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10
Q

explain what the myelin sheath is

A

formed by the folding of shwann cells- protects axon and provides electrical insulation

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11
Q

explain what a schwann cell is

A

associated with an axon and is a specialised cell
peripheral neurones are surrounded and supported by Schwann cells in vertebrate. neurones are myelinated- they grow around the axon of the nerve cells to form a multi-layered myelin sheath

forms the myelin sheath which insulates the axon- increases the speed of electrical impulses along the axon

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12
Q

explain what a terminal branch is

A

ending of axons divide into branches which form synapses with other neurones

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13
Q

explain what a node of ranvier is

A

gaps between myelination of axons. intervals along the myelin sheath which are important for speeding up the nerve impulse transmission

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14
Q

what is resting potential

A
  • electrical impulse
    nerve cells are able to transmit an electrical impulse because there is a difference in electrical potential across the membrane, something which can be measured using a voltmeter

At rest the potential difference in -70mV across the axon membrane

the membrane is polarised as it is maintaining a potential difference between two different sides
when the axon is at rest the difference in voltage is referred to as a resting potential

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15
Q

how is a resting potential established

A

There is a higher concentration of sodium on the outside of the neurone
there is a higher concentration of potassium on the inside of the neurone
the difference maintained by many Na+/K+ pumps that moves 3Na+ out of the cell and 2K+ in to the cell requires energy released by ATP

There are also voltage gated channel proteins for both K+ ions and Na+ ions embedded within the axon membrane
in a resting neurone the Na+ voltage gated channel proteins are closed
Na+ ions pumped out of the cell cannot diffuse back in by FD
some of the K+ ion channel proteins are open as the membrane is more permeable to K+ ions
some of the K+ ions can diffuse back out
more positive ions on the outside of the membrane than inside the neurone so the inside is slightly negative compared to the outside

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16
Q

how is a nerve impulse transmitted

A

the resting potential is maintained until the membrane is disturbed or stimulated
an action potential happens when the membrane reaches threshold and becomes depolarised
an action potential is the reversal of resting potential
the membrane potential goes from -70mV to 40mV in a short period of time

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17
Q

explain the process of depolarisation

A

the stimulus causes the membrane to become more permeable to Na+ ions
if the membrane potential reaches threshold, all the voltage gated Na+ channel proteins open
because there is a higher concentration of Na+ ions outside the cell, the Na+ diffuse rapidly into the cell
the higher concentration of positive Na+ ions inside the cell now reverses the resting potential and causes the inside to become positive in relation to the outside. this process is called depolarisation
the K+ voltage gated proteins remain closed
the high concentration of positive ions inside the cell is the action potential

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18
Q

explain repolarisation

A

once the internal potential difference reaches +40mV the Na+ voltage gated channel proteins close and the K+ ion voltage gated channel proteins open

there are more K+ on the inside of the axon than the outside of the axon membrane and therefore the K+ ions diffuse out of the cell down a concentration gradient

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19
Q

explain hyperpolarisation

A

the K+ ion channel proteins remain open longer than needed to reach resting potential, making the inside of the cell even more negative at -90mV. this process is called hyperpolarisation
the sodium potassium pump restores the resting potential back to -70mV

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20
Q

explain the all or nothing response

A

an action potential will only occur when the membrane is stimulated so that all the local Na+ voltage-gated channel proteins open

the minimum intensity of stimulus is called the threshold
sub threshold no action potential will occur
above the threshold a full size action potential is given regardless of the increase in the size of the stimulus

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21
Q

explain what a refractory period is

A

after transmitting an electrical impulse an exon has to recover before it can transmit another impulse

a period of inactivation following the transmission of an impulse is the refractory period
another action potential cannot be formed at that point until the period is over

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22
Q

define refractory period

A

the time taken to restore the resting potential

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23
Q

explain the impulse transmission along the axon

A

the nerve impulse is the movement of an action potential along the neurone. action potential act as a stimulus to ajacent polarised areas of the membrane and this causes the action potential to be passed along

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24
Q

explain how the myelin sheath and saltatory conduction lead to conduction of impulses

A

the impulse travels by jumping from one node of ranvier to the next node of ranvier - this is known as saltatory conduction
it occurs because the myelin sheath provides electrical insulation along the axon and depolarisation can only occur at the nodes of ranvier
the electrical impulse depolarise the next node and the impulse is passed along by jumping from node to node
this increases the rate of transmission as depolarisation only occurs at the nodes/ less of the axon membrane needs to be depolarised

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25
Q

explain how temperature increases speed of conduction of impulses

A

higher temp increases the kinetic energy so increases the rate of diffusion of ions therefore increasing the rate of conduction

26
Q

explain how axon diameter can affect the speed of conduction of impulses

A

the larger the axon diameter the greater the speed of conductance as larger membrane surface area means there is an increase in the number of channel proteins

27
Q

what are most synapses

A

cholinergic
uses acetylcholine neurotransmitters

28
Q

do impulses travel in a direction

A

they are unidirectional, from presynaptic neurones to post synaptic neurones

29
Q

where are neurotransmitters found

A

vesicles containing neurotransmitters are only produced in the presynaptic neurone and neurotransmitter receptor proteins are only found on the membrane of the post synaptic neurone membrane

30
Q

What is acetylene-choline

A

Neurotransmitter in parasympathetic branch of the autonomic nervous system

31
Q

A full description of how the synapse works

A

When an action potential arrives at the synaptic knob it causes voltage gated calcium ion channels in the pre-synaptic membrane to open

Calcium ions diffuse into synaptic knob by facilitated diffusion as there is a higher concentration of Ca2+ in the tissue fluid than synaptic cleft

Ca2+ activate enzymes which cause the synaptic vesicles to move towards the pre-synaptic membrane

The vesicles fuse with the pre-synaptic membrane and release the acetylcholine by exocytosis
- requiring ATP

Acetylcholine diffuses down a concentration gradient, across the cleft and bind to acetylcholine receptors on the post-synaptic membrane (acetylcholine receptors are protein molecules which are complementary to neurotransmitter)

When the neurotransmitter binds to complementary receptor proteins, Na+ channel proteins open and Na+ diffuse in

When reached threshold potential, the membrane becomes depolarised and an action potential occurs and spreads across the axon membrane of the postsynaptic neurone

In cholinergic synapse the enzyme acetylcholinesterase hydrolyses acetylcholine into choline and ethanol acid using hydrolysis

Choline and ethanol acid diffuse back across the synaptic cleft and are transported across the presynaptic neurone membrane

ATP released by mitochondria is used to re synthesise acetylcholine which is then stored in vesicles inside the presynaptic neurone

32
Q

Key points to remember for the synapse

A

The synapse will delay the impulse slightly
Synapse will prevent the impulse from going in the wrong direction
Synaptic transmission is the same regardless of the neurotransmitter

33
Q

What happens as a result of synapses being unidirectional

A

Vesicles containing neurotransmitter are only found in presynaptic neurone
Receptors for neurotransmitter are only found on post synaptic neurone

34
Q

What is a neuromuscular junction

A

A synapse between the motor neurone and a muscle cell. they use acetylcholine which binds to nicotine cholinergic receptors

35
Q

How does a neuromuscular junction work

A
  1. The postsynaptic membrane has lots of folds that form clefts. These clefts increase the surface area so more acetylcholinesterase enzymes that hydrolyse acetylcholine at faster rate
  2. The post synaptic membrane has more receptors than other synapses
  3. When a motor neurone fires an action potential it always triggers a response in a muscle cell
36
Q

Describe the reaction between a neuromuscular junction between a motor neurone and the muscle fibre

A

The never impulse passes down the sarcolemma into the T-Tubule, which allows more Na+ to diffuse into the muscle cell, stimulating the release of Ca2+ from the sarcoplasmic reticulum

37
Q

Give a simple definition of spatial summation

A

Different neurones converge at a single synapse. Action potentials arrive from several different neurones at the synapse
This causes the release of enough neurotransmitter to reach threshold and cause an action potential in the post-synaptic neurone

38
Q

Give a simple definition of temporal summation

A

Only one presynaptic neurone but the impulses arrive in rapid succession giving a cumulative effect which is sufficient to depolarise the post synaptic neurone

39
Q

What can cause fatigue

A

If the rate of transmitter is higher than the rate at which it is formed, then it is said to be fatigued. the presynaptic neurone cannot release enough neurotransmitter to generate an action potential in the post synaptic neurone until the transmitter is regenerated.

40
Q

What are the two different types pf neurotransmitters

A

Excitatory neurotransmitters and inhibitory neurotransmitters

41
Q

Explain how an excitatory neurotransmitter works

A

Causes action potential in post synaptic neurone by making the resting potential less negative, so less sodium ions are required to reach threshold

42
Q

Explain how an inhibitory neurotransmitter works

A

They affect different receptors on the post synaptic neurone
The resting potential becomes hyper-polarised and the postsynaptic membrane is therefore less likely to reach threshold and generate an action potential

43
Q

List one way drugs can act on a synapse- excitatory

A

Stimulate the nervous system by creating more action potentials in the post synaptic neurone
Drug may have similar shape to neurotransmitter and so binds to receptors on post synaptic membrane mimicking the effect of true neurotransmitter
Drug may can cause an increase in the release of a neurotransmitter
Drug may inhibit enzyme that hydrolyses the neurotransmitter

44
Q

Explain how a drug can have an inhibitory effect

A

They can create fewer action potentials in the post synaptic neurone and have an inhibitory effect. Drug may inhibit the release of neurotransmitter or bind or block receptors on post synaptic membrane

45
Q

Explain how cocaine works

A

Prevents the hydrolysis of the neurotransmitter involved in the sympathetic branch of the autonomic nervous system

46
Q

Explain how codeine works

A

Binds to receptors for endorphins which are neurotransmitters used in sensory nerve pathways particularly pain pathways

47
Q

Explain how heroin works

A

Binds to receptors for endorphins which are neurotransmitters used in sensory nerve pathways particularly pain pathways

48
Q

Explain how valium works

A

Increases the effect of GABA, an inhibitory neurotransmitter found binding to receptors for endorphins which are neurotransmitters used in sensory nerve pathways particularly pain pathways

49
Q

Explain how caffeine works

A

Reduces the threshold value for excitation of neurones

50
Q

Explain how BOTOX works

A

Botulinum toxin inhibits the release of acetylcholine

51
Q

As a neurone transmitters an impulse, its rate of oxygen consumption increases. Explain why

A

ATP required for active transport
Na+ actively transported out only at nodes in myelinated axon

52
Q

Describe how a resting potential is maintained in a neurone

A

Active transport of sodium ions across membrane
Out of neurone
Differential permeability to K+ and Na+
Membrane more permeable to K+ ions (leaky channels)

53
Q

The potential across the membrane is reversed when an action potential is produced. Describe how

A

Sodium ion gates open, Na+ rapidly diffuse in

54
Q

Describe the sequence of events leading to the release of acetylcholine and its binding to the postsynaptic membrane

A

Depolarisation of presynaptic membrane
Ca2+ channels open and calcium ions enter (synaptic knob)
Calcium ions cause synaptic vesicles to move to presynaptic membrane and release acetylcholine
Acetylcholine neurotransmitter diffuses across synaptic cleft
Acetylcholine binds to receptors on postsynaptic membrane
Sodium ions enter postsynaptic neurone leading to depolarisation

55
Q

When a nerve arrives at a synapse, it causes the release of neurotransmitter from vesicles in the presynaptic knob. Describe how

A

Nerve impulse causes Ca2+ channel proteins to open.
Ca2+ enter by facilitated diffusion
Causes synaptic vesicles to fuse with presynaptic membrane

56
Q

The binding of GABA to receptors on postsynaptic membranes causes negatively charged chloride ions to enter postsynaptic neurones. Explain how this will inhibit the transmission of nerve impulses by postsynaptic neurone

A

Inside of postsynaptic neurone becomes more negative/hyper-polarised
More sodium ions required to reach threshold for depolarisation

57
Q

Describe how the speed of the conduction could be increased by a neurone

A

Axon is myelinated

So saltatory conduction can occur
Axon has larger diameter so less resistance to flow of ions

58
Q

Myelination affects the rate of conduction of never impulses. Explain how

A

Impulse jumps from node of ranvier to node of ranvier
Fewer jumps/ depolarisations to travel length of axons

59
Q

Describe how the inhibition of acetylcholinesterase affects the action of synapses

A

Acetylcholine not broken down
Na+ continue to enter/ continued depolarisation

60
Q

Describe what is meant by the time refractory period

A

Limits the number of impulses per second
Maximum frequency of impulse transmission
Period of time between threshold and resting membrane potential
When maximum frequency reached, no further increase in information

Biology (21 decks)

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