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Anatomy > Conduction In The Nervous System > Flashcards

Conduction In The Nervous System Flashcards

1
Q

What is the plasma membrane?

A

A watery medium that surrounds a cell

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2
Q

What does the plasma membrane (cell membrane) separate?

A

The cytoplasm from the extra cellular fluid

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3
Q

What is the cytoplasm?

A

All materials inside the cell and outside the nucleus

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4
Q

The inside of the includes

A

Cytosol and intracellular structures collectively known as organelles

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5
Q

What is the cytosol?

A

Liquid (intracellular fluid)

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6
Q

A function of the plasma membrane is that it results in physical isolation

A

It forms a barrier

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7
Q

Another function of the plasma membrane is that it regulates exchange with the environment

A

Ions and nutrients enter

Wastes eliminated and cellular products released

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8
Q

Another function of the plasma membrane is that it results in sensitivity to the environment

A

Extra cellular fluid composition

Chemical signals

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9
Q

Another function of the plasma membrane is structural support

A

Anchors cells and tissues

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10
Q

The components of the plasma membrane that allow it to perform its characteristic functions are

A

Membrane lipids, membrane proteins and membrane carbohydrates

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11
Q

Membrane lipids make up

A

42% of its weight

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12
Q

Membrane lipids form

A

Phospholipid bilayer

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13
Q

The phospholipid bilayer has

A

Hydrophilic heads- towards watery environment
Hydrophobic fatty-acid tails- inside membrane
Barriers to ions and water-soluble compounds

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14
Q

Membrane proteins are

A

55% of its weight

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15
Q

Membrane proteins can be

A

Within the membrane-integral proteins or bound to inner or outer surface of the membrane- peripheral proteins

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16
Q

Examples of important types of functional proteins include the following:

A
  1. Anchoring proteins
  2. Recognition proteins
  3. Enzymes
  4. Receptor proteins
  5. Carrier proteins
  6. Channels
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17
Q

Anchoring proteins act as

A

Stabilisers and attach to inside or outside structures

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18
Q

Recognition proteins act as

A

Identifiers and label cells as normal or abnormal

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19
Q

Enzymes

A

Catalyse reactions

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20
Q

Receptor proteins bind and respond to

A

Ligands (ions, hormones)

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21
Q

Carrier proteins transport specific diluted

A

Through membrane

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22
Q

Channels

A

Regulate water flow and solutes through membrane

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23
Q

Membrane carbohydrates are

A

3% of its weight

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24
Q

Membrane carbohydrates include

A

Proteoglycans, glycoproteins and glycolipids

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25
Q

Membrane carbohydrates

A

Extend outside cell membrane and form sticky “sugar coat” (glycocalyx)

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26
Q

Functions of the glycocalyx include

A
  • lubrication and protection
  • anchoring and locomotion
  • specificity in binding (receptors)
  • recognition (immune response)
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27
Q

Transmembrane potential is

A

The electrical potential of the cell’s interior relative to its surrounding

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28
Q

The transmembrane potential charges are separated creating a

A

Potential difference

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29
Q

Unequal charge across the plasma membrane

A

Is transmembrane potential

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30
Q

Membrane potential is

A

Ion movements and electrical signals

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31
Q

All plasma (cell) membranes produce

A

Electrical signals by ion movements

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32
Q

Membrane potential is particularly important to

A

Neurons

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33
Q

The five main membrane processes in neural activities are:

A 
Resting potential
Graded potential
Action potential
Synaptic activity
Information processing
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34
Q

The resting potential is the

A

Membrane potential of resting cell

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35
Q

The graded potential is the

A

Temporary, localised change in resting potential and is caused by stimulus

36
Q

Action potential is

A

An electrical impulse produced by graded potential and propagates along surface of axon to synapse

37
Q

Synaptic activity releases

A

Neurotransmitters at presynaptic membrane and produces graded potentials in postsynaptic membrane

38
Q

Information processing is

A

Response (integration of stimuli) of postsynaptic cell

39
Q

Passive forces acting across the plasma membrane are

A

Chemical gradients and electrical gradients

40
Q

Chemical gradients are

A

Concentration gradients (chemical gradients) of ions (Na+, K+)

41
Q

Electrical gradients

A

Separate charges of positive and negative ions and result in potential difference

42
Q

Electrical currents and resistance include

A

Electrical current and resistance

43
Q

Electrical current is

A

Movement of charges to eliminate potential difference

44
Q

Resistance is the

A

Amount of current, ion movements, a membrane restricts

45
Q

What are the two types of membrane potential?

A

Passive channels and active channels

46
Q

Passive channels aka leak channels are

A

Always open and permeability changes with conditions

47
Q

Active channels aka as gated channels

A

Open and close in response to stimuli and at resting potential, most gated channels are closed

48
Q

The three states of gated channels are

A
  1. Closed, but capable of opening
  2. Open (activated)
  3. Closed, not capable of opening (inactivated)
49
Q

What are the three classes of gated channels?

A

Chemically gated channels
Voltage gated channels
Mechanically gated channels

50
Q

Chemically gated channels open in presence of

A

Specific chemicals (e.g ACh) at a binding site and they are found on neuron cell body and dendrites

51
Q

Voltage gated channels respond to

A

Changes in membrane potential and have activation gated (open) and inactivation gated (close)

52
Q

Voltage gated channels have characteristic of

A

Excitable membrane and are found in neural axons, skeletal muscle, cardiac muscle

53
Q

Mechanically gated channels respond to

A

Membrane distortion and are found in sensory receptors (touch, pressure, vibration)

54
Q

What is an action potential?

A

An electrical event

55
Q

Action potentials are propagated by

A

Changes in membrane potential, that once initiated, affect an entire excitable membrane

56
Q

These electrical events are also known as

A

Nerve impulses and link graded potentials at cell body with motor end plate actions

57
Q

What are the four steps in the generation of action potentials?

A

Step 1: depolarisation to threshold
Step 2: activation of Na+ channels
Step 3: inactivation of Na+ channels and activation of k+ channels
Step 4: return to normal permeability

58
Q

With step 2: activation of Na+ channels there is

A

Rapid depolarisation
Na+ ions rush into cytoplasm
Inner membrane changes from negative to positive

59
Q

With step 3: inactivation of Na+ channels and activation of k+ channels

A

Occurs at +30mV
Inactivation gates close (Na+ channel inactivation)
K+ channel open
Repolarisation begins

60
Q

With step 4: return to normal permeability

A

K+ channels begin to close when membrane reaches normal resting potential (-70mV)

K+ channel finish closing and membrane is hyper polarised to -90mV. Membrane potential returns to resting level and action potential is over

61
Q

What is the all or none principle?

A

If a stimulus exceeds threshold amount:
The action potential is the same
No matter how large the stimulus

62
Q

With the all or none principle, action potential is either

A

Triggered, or not

All stimuli that bring the membrane to threshold generate identical action potentials

63
Q

Similar example to all or none principle

A

The speed and range of the bullet that leaves the gun do not change, regardless the force that you applied to the trigger

64
Q

The refectory period is the time period between;

A

From beginning of action potential
To return of resting state
During which membrane will not respond normally to additional stimuli
Because all the gated voltage sodium channels either are already open or are inactivated

65
Q

Similar example to the refractory period

A

Flushing a toilet, nothing happens while you press the handle, until the water starts to flow (threshold is reached). After that, the amount of water that is released is independent of how hard or quickly you pressed the handle (all or none principle). Finally, you cannot flush the toilet again until the tank refills (refractory period)

66
Q

There are two parts the the refractory period:

A

Absolute refractory period which lasts 0.4-1msec and the relative refractory period

67
Q

With the absolute refractory period the sodium channels

A

Open or inactivated and no action potential is possible

68
Q

With the relative refractory period the membrane potential is

A

Almost normal and very large stimulus can initiate action potential

69
Q

What is propagation?

A

Moves action potentials generated in axon hillock and along entire length of axon

70
Q

What are the two methods of propagating action potentials?

A
  1. Continuous propagation (Unmyelinated axons)

2. Saltatory propagation (myelinated axons)

71
Q
  1. Continuous propagation of action potentials along an Unmyelinated axon affects
A

One segment of axon at a time

72
Q

Steps in propagation:

A

Step 1: action potential in segment 1
- depolarises membrane to +30mV
- local current
Step 2: depolarises second segment to threshold- second segment develops action potential
Step 3: first segment enters refractory period
Step 4: local current depolarises next segment

73
Q

After the steps in propagation,

A

The cycle repeats and action potential travels in one direction (1m/sec)

74
Q

What is saltatory propagation?

A

Action potential along myelinated axon

75
Q

Saltatory propagation is faster and used

A

Less energy than continuous propagation

76
Q

In saltatory propagation myelin,

A

Insulates axon, prevents continuous propagation

77
Q

With saltatory propagation, local current

A

“Jumps” from node to node and depolarisation occurs only at nodes

78
Q

What are the components of the plasma membrane that allow it to perform its characteristic functions?

A

Membrane lipids, membrane proteins and membrane carbohydrates

79
Q

Which component of the plasma membrane is primarily responsible for the membranes ability to form a physical barrier between the cells internal and external environments?

A

The phospholipid bilayer of the plasma membrane forms a physical barrier between the cells internal and external environments

80
Q

What type of integral protein allows water and small ions to pass through the plasma membrane?

A

Channel proteins are integral proteins that allow water and small ions to pass through the plasma membrane

81
Q

The resting potential

A

Is the transmembrane potential of a normal cell under homeostatic conditions

82
Q

What effect would a chemical that blocks the voltage gated sodium channels in neuron plasma membranes have on neurons ability to depolarise?

A

If the voltage gated sodium channels in a neurons plasma membrane could not open, sodium ions could not flood into the cell, and it would not be able to depolarise

83
Q

An action potential is a

A

Propagated change in the transmembrane potential of excitable cells, initiated by a change in the membrane permeability to sodium ions

84
Q

What effect would decreasing the concentration of extra cellular potassium ions have on the transmembrane potential of a neuron?

A

If the extra cellular concentration of potassium ions decreased, more potassium would leave the cell, and the electrical gradient across the membrane (the transmembrane potential) would increase. This condition is called hyper polarisation

85
Q

What does the transmission speed of the action potential depend on?

A

The diameter of the axon and if it is myelinated or not

Anatomy (8 decks)

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