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Biology of the mind > Communication in the nervous system > Flashcards

Communication in the nervous system Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is the resting membrane potential? (2)

A

Defined as the electrical potential difference across the plasma membrane when the cell is in a non-excited state

Electrical potential difference across a cell membrane is expressed by its value inside the cell relative to the extracellular environment

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2
Q

How is the potential difference measured? (1)

A

By placing electrodes inside neurones and measuring potential difference between inside and outside of the cell

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3
Q

What is the potential difference when both electrodes are in the bath solution? (1)

A

Potential difference is 0

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4
Q

What is the potential difference when electrode is inserted into the cell? (1)

A

Reveals a negative potential of -65mV

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5
Q

Why is resting potential important? (1)

A

Without it you could die

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6
Q

How do neurones create and use electrical forces? (1)

A

An electrical gradient drives an ion towards an area of oppositely charged ions

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7
Q

What are ion pumps? (3)

A

Proteins
Actively move ions against concentration gradients
Create ion concentration gradients

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8
Q

What are ion channels? (3)

A

Proteins
Allow ions to diffuse down concentrations or electron gradients
Cause selective permeability to ions

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9
Q

What are the three different ways channels can be opened? (3)

A

Chemicals (ligand gated)
Voltage changes (voltages gated)
Mechanically (stretch activated)

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10
Q

What are the four factors contributing to resting potential? (4)

A

Charged intracellular proteins
The Na+/K+ pump
K+ ions
Na+ ions

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11
Q

What is the role of charged intracellular proteins in resting potential? (2)

A

Cannot cross the membrane and leave the cell interior, so contribute to its negativity

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12
Q

What is the role of Na+/K+ pump in resting potential? (2)

A

Uses ATP to move three Na+ ions out for every two K+ ions in
Thus inside of the cell gets more negative

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13
Q

What is the role of K+ ions in resting potential? (2)

A

Membrane is freely permeable to K+ at rest due to selective channels in the membrane

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14
Q

How does potential of K+ reach equilibrium? (3)

A

K+ tries to leave cell down a gradient
But inside of cell is negative (electrical gradient) and tries to pull K+ back in
Eventually they become balanced and the potential of K+ would be in equilibrium

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15
Q

What is the Nernst Equation? (2)

A

The voltage produced by a difference in concentration of a single ion across a membrane is:

E = 2.303 RT/zF log[A]0/[A]i

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16
Q

Why is the Nernst Equation not sufficient to calculate the resting membrane potential? (2)

A

Few Na+ ions flow in the cell at rest too so resting potential will not be equal to Ek
Need to take into account the effect of flow of Na+ ions

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17
Q

Why is the Goldman-Hodgkin-Katz (GHK) equation used to calculate Vm? (2)

A

Takes into account concentration gradient of the permeant ions and the relative permeability of the membrane to each ion

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18
Q

What is the GHK equation? (1)

A

https://www.google.com/url?sa=i&url=https%3A%2F%2Fnicoaddae.com%2F2017%2F04%2F23%2Fthe-nernst-and-goldman-equations%2F&psig=AOvVaw19Id08s6DKJPtFzTXmDuT-&ust=1708349434096000&source=images&cd=vfe&opi=89978449&ved=0CBMQjRxqFwoTCIDxhtv_tIQDFQAAAAAdAAAAABAE

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19
Q

What is an action potential? (2)

A

Period of rapid reversal of membrane potential that overshoot 0mV, lasting a few millisecond
Reached when threshold is reached

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20
Q

How can action potential be measured? (2)

A

Electrode placed inside neurone
Another electrode placed inside to inject current

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21
Q

What is depolarisation? (2)

A

Inside of the cell is negative compared to the outside
A positive current is injected into the cell
Inside becomes more positive
As positive ions flow towards negative areas, local currents are created that depolarise adjacent membrane areas and allow the wave of depolarisation to spread

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22
Q

How does a higher depolarisation stimulation affect action potential? (2)

A

More action potential
But they are of the same magnitude

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23
Q

Name the phases of action potential (4)

A

Polarised at rest
Rising phase (depolarisation)
Overshoot phase
Falling phase (repolarisation)
Undershoot phase (after hyperpolarisation)

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24
Q

When does an action potential occur? (2)

A

When a neurone sends information down an axon, away from cell body
The action potential is an explosion of electrical activity that is created by a depolarising current, usually from a synaptic input from another neurone

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25
Q

Describe what happens to the voltage gated Na+/K+ channels during the resting state (2)

A

All voltage-gated Na+/K+ channels closed
Neither Na+ or K+ can pass through the channels at rest

26
Q

Describe what happens to the voltage gated Na+/K+ channels during depolarising phase (2)

A

Activation gates of Na+ channels open
Leads to large influx of Na+ ions

27
Q

Describe what happens to the voltage gated Na+/K+ channels during repolarising phase (2)

A

Inactivation of Na+ channels closing
K+ channels open
K+ leave the neurone

28
Q

What is the absolute refractory period? (1)

A

No further action potential can be elicited

29
Q

Why is the absolute refractory period important? (1)

A

Ensures that action potential propagation is unidirectional

30
Q

What is the relative refractory period? (1)

A

A larger stimulus can result in an action potential

31
Q

How does myelination increase conduction velocity? (1)

A

Ensures no leaked of current

32
Q

What is saltatory conduction? (2)

A

Action potential jumps from node of Ranvier to node of Ranvier
Transmission is significantly enhanced

33
Q

What is electrical transmission? (2)

A

Direct flow of ions from one neurone to another, hence direct influence of electric current from one to another

34
Q

What can gap junctions be modulated by? (3)

A

pH
Neurotransmitters
Changes in intracellular calcium

35
Q

Where can gap junctions be found in neurones? (2)

A

Between axons of mossy fibres in hippocampus
Between dendrites in interneurones of the cerebellum

36
Q

What are the functions of gap neurones? (2)

A

Transmission of action potentials at an electrical synapse in a crayfish
Synchronisation of electrical activity - enhances responses

37
Q

What is chemical transmission? (2)

A

Neurotransmitter substance released from presynaptic cell, diffuse across synaptic cleft, produces effect on post synaptic neurone

38
Q

What is the criteria for a chemical messenger to be considered a neurotransmitter? (4)

A

Must be synthesised in the neurone
Must be present in presynaptic terminal and be released in amounts sufficient to exert its supposed effect on the postsynaptic neurone
When applied exogenously in reasonable concentrations, it must mimic exactly the actions of the endogenously released neurotransmitter
Must be a specific mechanism of removing it from its site of action

39
Q

How are amines and amino acid neurotransmitters synthesised? (2)

A

Small organic molecules
Synthesised in the synaptic terminal using synthesising enzymes that are transported from the cell body

40
Q

How are peptide neurotransmitters synthesised? (1)

A

Synthesised in the cell body using protein synthesis machinery

41
Q

After synthesis, how are neurotransmitters stored? (1)

A

In synaptic vesicles

42
Q

What are the two types of synaptic vesicles (2)

A

Small clear vesicles
Large dense core vesicles

43
Q

Which type of neurotransmitters do small clear vesicles store? (1)

A

Amines and amino acids

44
Q

Which type of neurotransmitters do large dense core vesicles store? (1)

A

Peptides

45
Q

Why is it important to store neurotransmitters in synaptic vesicles? (2)

A

Concentrate neurotransmitters
Ready for release

46
Q

What is co-existence/co-transmission? (1)

A

A single neurone may synthesise and release more than one transmitter substance

47
Q

What are active zones in presynaptic neurones? (1)

A

Areas where synaptic vesicles are concentrated

48
Q

How are neurotransmitters released - calcium influx in chemical transmission? (5)

A

Action potential arrives in the presynaptic terminal causing depolarisation
Voltage-gated calcium channels are opened by depolarisation
Calcium rushes into the terminal at active zones
Calcium ions trigger neurotransmitter release
Calcium influx an also influence the shape of the action potential

49
Q

Describe the process of synaptic vesicles cycling (5)

A

Free vesicles are targeted to the active zone
Vesicles dock with the active zone
The docked vesicle is primed for exocytosis
In response to a rise in [Ca2+], the vesicles undergo fusion and release their contents
The fused vesicle membrane is taken up into the cell by endocytosis

50
Q

Why is synaptic vesicle docking important? (1)

A

Allows a fast release of synaptic content

51
Q

How are neurotransmitters released? (3)

A

Released in quanta
A single quantum contains thousands of neurotransmitters
Quanta can be released spontaneously

52
Q

Which two receptors are important for postsynaptic effect? (2)

A

Metabotropic receptors
Ionotropic receptors

53
Q

What are metabotropic receptors? (2)

A

Coupled to intracellular proteins that transduce the signal to the cell interior (slow response)

54
Q

What are ionotropic receptors? (2)

A

Form ion channels, that depolarise or hyper polarise the post synaptic cell (fast response)

55
Q

After release of neurotransmitter, why is rapid clearance of neurotransmitter important? (1)

A

Desensitisation

56
Q

How does vesicle recycling take place? (2)

A

Re-uptake of neurotransmitter into terminal by:
- endocytosis
- neurotransmitter transporters

57
Q

What is an excitatory postsynaptic potential? (1)

A

Excitatory neurotransmitter draws membrane potential towards threshold

58
Q

What is an inhibitory postsynaptic potential? (1)

A

Inhibitory neurotransmitter draws membrane potential away from threshold and makes it more negative

59
Q

What is temporal summation? (1)

A

Involves a single presynaptic neurone rapid-firing signals to a single postsynaptic neuron’s synapse

60
Q

What is spatial summation? (1)

A

Involves multiple presynaptic neurones simultaneously sending signals to a single neurone

61
Q
A

Biology of the mind (9 decks)

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