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A&P I Lecture and Lab > A&P I Ch.10 & 12 Excitable Cells > Flashcards

A&P I Ch.10 & 12 Excitable Cells Flashcards

1
Q

Excitability

A

the ability to send and receive electrical signals across the plasma membrane

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2
Q

Concentration Gradient

A

difference in concentration of a substance between two compartments

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3
Q

What are the ions?

A

-Potassium (K)
-Sodium (Na)
-Chloride (Cl)
-Calcium (Ca)

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4
Q

What is the trend of Potassium?

A

higher inside

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5
Q

What is the trend of Sodium?

A

higher outside

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6
Q

What is the trend of Chloride?

A

higher outside

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7
Q

What is the trend of Calcium?

A

higher outside

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8
Q

Charge of Potassium

A

+1

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9
Q

Charge of Sodium

A

+1

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10
Q

Charge of Chloride

A

-1

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11
Q

Charge of Calcium

A

+2

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12
Q

General equation for calculating concentration gradients

A

Gradient= [Ion]out - [Ion]in

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13
Q

What is the gradient of..
[Na+]out= 150mM
[Na+]in= 15mM

A

135mM

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14
Q

What is the gradient of..
[Na+]out= 150mM
from: [Na+]in= 15mM to 50mM

A

from: 135mM to 100mM
when inside increases gradient decreases

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15
Q

What is the gradient of..
[Na+]out= 150mM
from: [Na+]in= 15mM to 5mM

A

from: 135mM to 145mM
when inside decreases gradient increases

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16
Q

What does it mean to move down a concentration gradient?

A

moving from HIGH to LOW concentration

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17
Q

What does it mean to move up a concentration gradient?

A

moving from LOW to HIGH concentration

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18
Q

Key points about ion channels

A
  1. Pumps only allow passive transport
    -only allow ions to move DOWN their concentration gradient
    -flux increases as concentration gradient increases
    -active transport occurs via combination of transporters and pumps
  2. Pumps are selective for specific ions
    -Na+ channels only allow Na+
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19
Q

Voltage-Gated

A
  • binding
  • gated by change in charge
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20
Q

Ligand-Gated

A
  • electricity
  • gated by chemical messenger
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21
Q

What do ion channels do and what are the two types?

A
  • Transport ions across a membrane
  • Ligand-Gated and Voltage-Gated
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22
Q

Relative Concentrations During Homeostasis

A

-the millions of molecules moving across a concentration gradient represent only a TINY fraction of the molecules present in the interstital fluid and cytoplasm
-the concentration of sodium (for example) will ALWAYS be 10 times greater outside the cell than inside

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23
Q

What is the relative concentration of a healthy person?

A

the relative concentration of any one ion is CONSTANT

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24
Q

Neutral Atom

A

same # of protons and electrons

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25
Q

If the atom is negatively charged…

A

more electrons than protons

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26
Q

If the atom is positively charged…

A

more protons than electrons

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27
Q

Electrostatic Forces

A

-if ions are distributed unevenly across a membrane, then there is uneven distribution of charge across that membrane
-if ions are permeable and being transported across the membrane, then the charge distribution across the membrane is also changing

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28
Q

Membrane Potential

A

a form of potential energy created by a difference in charge between two environments

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29
Q

Membrane Potential Across the Plasma Membrane

A

-When ions move across the membrane, they change the electrochemical gradient
-allows cells to use the stored energy (membrane potential) for critical cellular processes

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30
Q

True or False? The concentration gradients for any one ion generally stay constant

A

True (if you are healthy conc. gradients barely change)

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31
Q

The concept of electrochemical equilibrium

A

-Electrostatic repulsion (flex outward)
-Equilibrium potential (no net flux)
-Concentration gradient (flux inward)

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32
Q

Electrostatic Repulsion (flex outward)

A

eg. Na+ is repulsed by the accumulation of positive charge inside the cell

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33
Q

Equilibrium Potential (no net flux)

A

BALANCE of forces inward versus outward

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34
Q

Concentration Gradient (flux inward)

A

e.g. Na+ flows from high concentration to low

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35
Q

Recoil

A

upward

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36
Q

Equilibrium

A

no movement

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37
Q

Gravity

A

downward

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38
Q

Nernest Equation

A

Eion= 61.5 mV/z * log10 [ion]out/ [ion]in

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39
Q

What does the Nernst equation calculate?

A

the electrochemical equilibrium point

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40
Q

What is Eion in the nernst equation?

A

the equilibrium potential for an ion

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41
Q

What is 61.5mV in the nernst equation?

A

a constant that assumes the cell is at 37 degrees celcius

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42
Q

log10[ion]out/ [ion]in

A

refers to the concentrations of the ion inside and outside of the cell

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43
Q

What is “z” in the nernst equation?

A

charge of the ion

44
Q

Calculate the equilibrium potential of Chloride, when [Cl]out= 136mM and [Cl]in= 45mM

A

ECl= -29.52mV

45
Q

Aside from constant values, what does the equilibrium potential of a given ion depend on? (What changes in the formula (DV)?)

A

Concentration of that ion inside and outside of the cell

46
Q

If the concentration gradient is 0 what is the equilibrium potential?

A

It is also 0 (no concentration gradient -> no equilibrium)

47
Q

True or false? Equilibrium is calculated together with each ion

A

FALSE; Equilibrium Potential is calculated SEPARATELY for each ion

48
Q

True or false? Ion concentrations are regulated randomly, so equilibrium potentials generally change randomly

A

FALSE; Ion concentrations are regulated HOMEOSTATICALLY, so equilibrium potentials generally DO NOT change

49
Q

Membrane potential depends on __________ _________
across the membrane

A

ION PERMEABILITY

50
Q

Although cells are permeable to more than one ion, they are…

A

not equally permeable

51
Q

What is the movement of ions at resting membrane potential?

A

the point where the movement of all ions is equal and opposite across the membrane (i.e., the net flux is zero); however, it is not a point where ions have stopped moving

52
Q

At resting membrane potential: Net Flux=

A

0 (equal in and out)

53
Q

Permeability of an ion increases —->

A

Resting membrane potential moves TOWARDS that ion’s equilibrium potential

54
Q

Permeability of an ion decreases —->

A

Resting membrane potential moves AWAY FROM that ion’s equilibrium potential

55
Q

The permeability of sodium were decreased, what would happen to the resting membrane potential?

A

It would decrease (become more negative)

56
Q

What does the saying, “The Neuron is an excitable cell” mean?

A

the neuron detects a stimulus and transduces it into an electrical signal

57
Q

Dendrites

A
  • area where we receive signals from
  • projections that extrude from the cell body
  • site of signal input
    -contain mainly ligand-gated channels
58
Q

Axon

A

-“tail”
-sends signal
-long process extruding from soma
-where action potential travel
-contains voltage-gated channels that respond to local electrical changes

59
Q

Axon Terminal

A
  • distal portion of the axon
  • site of signal output
  • has synaptic cleft
60
Q

Soma

A

-cell body
-contains nucleus, organelles, and majority of cytoplasm

61
Q

Axon Hillock

A
  • beginning of axon
  • “trigger zone” where action potential is generated
62
Q

What structure do neurons relay messages through?

A
  • Synapses
    -pre-synaptic cell
    -synaptic cleft
    -post-synaptic cell
63
Q

Pre-Synaptic Cell

A

-neuron located before a synapse
-sends the signal

64
Q

Synaptic Cleft

A

gap between two cells filled with interstitial fluid

65
Q

Post-Synaptic Cell

A

-neuron located after a synapse
-receives the signal (receives neurotransmitters through dendrites)

66
Q

Messages are sent as ____________

A

Neurotransmitters

67
Q

Neurotransmitters

A

-molecules used by the body to carry signals

68
Q

Popular Neurotransmitters

A
  • Acetylcholine
  • Glutamine
  • Dopamine
  • Serotonin
  • Norepinephrine
69
Q

Acetylcholine

A

responsible for stimulating muscle contraction

70
Q

Neurotransmitters Target Destinations

A
  • other neurons
  • muscle cells
  • glands
71
Q

Which part of the neuron transmits the electrical signal from one end of the cell to the other?

72
Q

What are the two major types of changes in membrane potential do neurons produce?

A

Graded and Action

73
Q

Graded Potential

A
  • produced when a ligand opens a ligand- gated channel in dendrites, allowing ions to enter or exit the cell
  • transient change from resting membrane potential
  • decreases in intensity over time and distance
74
Q

Depolarization

A

membrane potential moves from rest to more positive value

75
Q

EPSP

A

Excitatory Post Synaptic Potential

76
Q

Repolarization

A

membrane potential moves back to resting value

77
Q

Hyperpolarization

A

membrane potential moves from rest to a more negative value

78
Q

What is the purpose of hyperpolarization?

A

-to maintain checks and balances
-gives cell time to rest

79
Q

Graded potentials are ____________

A

decremental

80
Q

Decremental

A
  • changes in membrane potential are restricted to local area where ions are moving
81
Q

No Summation

A

weak and unviable

82
Q

Temporal Summation

A

-short period of time
-many signals received at the same time

83
Q

Spatial Summation

A

-sent from same location

84
Q

EPSP- IPSP Cancellation

A

alternating signals being sent out + bump and
- bump

85
Q

Threshold Potential

A

must be reached for signal to be viable

86
Q

An excitatory post synaptic potential (EPSP) is…

A

depolarizing (positive)

87
Q

Action Potential always begins with _________

A

depolarization

88
Q

The depolarization phase is characterized by ________ _________ ________

A

Rapid Sodium Entry

89
Q

Rapid Sodium Entry

A

always begin with opening sodium channels so Sodium floods the cell which makes the cell more positive and voltage “shoots up”

90
Q

What does a closed odium channel mean?

91
Q

What does an opening sodium channel mean?

A

Subthreshold

92
Q

What does an open sodium channel mean?

A

Depolarization

93
Q

What does an inactivated sodium channel mean?

A

Repolarization

94
Q

The Repolarization phase is accelerated by _______ _______

A

Potassium Efflux

95
Q

Repolarization Phase

A

voltage gated potassium channels reach peak permeability

96
Q

Hyperpolarization on Phase

A
  • potassium channels still open
  • inactivation gate on sodium channels opens
  • relative refractory period- cell is hyper polarized, so requires greater stimulus to reach threshold
97
Q

After- Hyperpolarization on Phase

A
  • all channels close off
  • potassium permeability reduced
  • membrane potential goes back to resting value
98
Q

True or False? Open sodium channels accelerate the repolarization phase of an action potential.

A

FALSE: Open potassium channels accelerate the repolarization phase of an action potential.

OR: Open sodium channels accelerate the depolarization phase of an action potential.

99
Q

Action Potential Propagation

A

Action potential is “recharged” at each axon segment by fresh flow of Na+

100
Q

Factors affecting action potential propagation

A
  • Axon Diameter
  • Myelination
101
Q

Axon Diameter

A
  • More space = more sodium channels = more depolarization
  • Wider axons= faster action potential propagation
102
Q

Myelination

A

-put myelin on the axon
-substance that coats (partially electrically insulates) axon
-produced by Schwann cells and oligodendrocytes

103
Q

Nodes of Ranvier

A

where axons are refreshed

104
Q

Axon Terminals

A
  • goal is to make it to the bottom to open calcium channels
  • when the action potential reaches the axon terminal, voltage-gated calcium channels are triggered to open, allowing calcium channels are triggered to open, allowing calcium influx into the axon terminal
    -calcium allows membrane-bound vesicles, containing neurotransmitters produced by this neuron, to attach to the post-synaptic membrane and be released into the synapse
  • If the post synaptic cell is a neuron, then the process will repeat when the neurotransmitter binds to ligand-gated ion channels on its dendrites
105
Q

Electrical Synpases

A

-specialized gap junction
-current spreads passively across gap junction
-allows action potential from one cell to move rapidly into another
-avoids delay inherent in chemical synapses
-cannot be modulated
-e.g. cardiac cells

106
Q

Graded Potential V.s. Action Potential

A&P I Lecture and Lab (12 decks)

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