5. Physiology of excitable tissues. Ligand/voltage gated channels, transmembrane/resting potential Flashcards

1
Q

What are excitable tissues

A

Muscle and nerve tissue due to their partly electrical response to external stimuli

Excitable cells use electrical signals (fast
changes in ion permeability and membrane
potential) to encode, process and transmit
information.

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2
Q

What is an excitable membrane (DEF)

A

They are membranes that react to stimuli with selective change in their ionic permeability

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3
Q

What is a diffusion potential - mV
( Potential difference)

A

Caused by the diffucsion of ions

Created when a charged solute diffuses down its concentration gradient

ONLY CREATED IF MEMBRANE PERMEABLE TO THAT ION

Created by movement of only a FEW ions

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4
Q

What is equilibrium potential of a particular ion

A
  • Net flow through a membrane for a fiven ion is equal to zero
  • When the flow of ions moving along conc grad, equalizes w flow of ions moving along electrochemical gradient

The equilibrium potential is the diffusion potential that exactly balances or opposes the tendency for diffusion down the concentration difference

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5
Q

What happens at electrochemical equilibrium

A

The chemical and electrical driving forces
acting on an ion are equal and opposite, and no further net diffusion occurs.

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6
Q

How is membrane potential created?

A

Potential difference between 2 sides of the cell membrane

This is caused by diffusion of ions Na+/K+ pump

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7
Q

What is important in determining membrane potential

A

permeability of an ion

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8
Q

What equation do you use to calculate equilibrium potential

A

NERNST

Eion = RT/zF . ln (ion ex)/(ion int)

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9
Q

What equation do you use to calculate membrane potential

A

GOLMDMANS

bit long to type but includes permeability

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10
Q

What is the electogenic effect of Na+/K+ pump

A

exports 3 Na+
imports 2K+

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11
Q

For charged solutes, the driving force must consider the conc differecne and electical potential difference

How is driving force calculated

A

Difference btw the membrane potential and the ions calculated eqm potential

  • When the driving force is negative (i.e., Em is more negative than the ion’s equilibrium potential), that ion will enter the cell if it is a cation and will leave the cell if it is an anion.
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12
Q

What is a electrochemical gradient

baso driving force

A

Difference btw electochemical potentials of ion on both sides of membrane

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13
Q

What causes membrane potential to change

A

slective change of ionic permeability

when pump activity chnages

proportional changes in conc gradient

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14
Q

What is the result if the electrochemical gradient of an ion has negative value

A

ion flow will be directed inwards the cells

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15
Q

What ion flow will be larger when
non-selective Na+- К+ channels in
a postsynaptic membrane open?

A

Na+ flow larger therefore mem will depolarize

BC 5.4 times more sodium will enter the cell than k+ will leave

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16
Q

What is the change in the membrane potential in permeability of K+ increases

A

hyperpolariation

17
Q

What is the change in membrane potential if permeability of Na+ increases

A

depolarization

18
Q

what is the change in membrane potential if permeability of Cl- increases

A

hyperpolarization

19
Q

what happens to membrane potential if na+/K+ pump:

Blocked
activated

A

depolarization

hyperpolarixation

20
Q

What are the basdic types of ion channels depending on their gated mechanisms

A

VOLTAGE GATED- when electrical signal open/close channel (electrically excitable membrane)

LIGAND GATED-bchemical stimulus binds to channel (electrically non excitable)

Mechanically gated-mechanical/stress stimulus eg sensory receptors for touch and pressure

21
Q

Does light cause the opeing and closing of ion channels

A

not directly

photons stimulate pigment in eye-ligand gated ion channel

22
Q

where are voltage gated sodium potassium channels abundantly found

A

axon hillock

23
Q
A
24
Q
A