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Semester 2 Biology Revision > Electrophysiology > Flashcards

Electrophysiology Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is an ion’s equilibrium potential?

A

Gradient across the membrane to maintain a concentration gradient.

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2
Q

If there is a higher concentration of Potassium ions inside the cell than outside what happens?

A

Potassium ions diffuse out the cell down the chemical gradient.

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3
Q

What is Chemical Potential governored by?

A
  1. Ion Concentration

2. Valency

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4
Q

Chemical Gradient

A

Difference in SOLUTE concentration across the membrane.

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5
Q

Electrical Gradient

A

Difference in charge across membrane.

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6
Q

Ionic Gradients

A

Chemical Gradient & Electrical Gradient

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7
Q

How influential the ionic gradients are on membrane potential depends on….

A

relative permeability of the membrane to each ion.

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8
Q

Why will most cells at rest have a membrane potential closer to potassium?

A

As the cell is most permeable to Potassium ions at rest.

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9
Q

Squid Axon- When lowering the external sodium in the solution what happens to the AP? Why?

A

Lowers to peak of the action potential because electrochemical driving force is lower.

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10
Q

What does a voltage clamp measure?

A

Measures the current.

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11
Q

Why are sodium/ potassium current active at different times?

A

Potassium/ Sodium channels are open at different times.

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12
Q

Lowering the intercellular concentration of potassium ions what does this cause? How?

A

Decreases peak of potassium ions of K+ current by lowering the value of Nearst Equation.

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13
Q

What is the magnitude of current dictated by?

A
  1. Number of channels the current can pass through.

2. The electrochemical gradient (different between both membrane potentials).

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14
Q

Absolute Refractory Period

A

Too few Sodium channels have recovered from inactivation so not possible to send another action potential.

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15
Q

Relative Refractory Period

A

Proportion of Sodium channels have recovered possible to send an action potential with a greater stimulus.

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16
Q

Why can cardiac action potentials not elect to summative contraction?

A

Refractive period too long.

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17
Q

Compare the length of a normal AP and a Cardiac AP:

A

Normal: 7 m/s
Cardiac: 225 m/s

18
Q

What is the “ALL OR NOTHING PRINCIPAL”?

A

If an stimulus does not hit the threshold then the action potential will not fire. Action potentials are all the same size.

19
Q

A single skeletal muscle action potential leads to what?

A

Release of Calcium ions in the sarcoplasmic reticulum which leads to a contraction.

20
Q

How is a larger muscle contraction created?

A

Repeated stimulus at a neuromuscular junction.
Greater number of skeletal action potentials.
‘Summate’ larger contraction.

21
Q

Voltage Gated Ion Channels?

A

Channel conductance is determined by changes in membrane potential.

22
Q

Describe the structure of a potassium voltage gated ion channel.

A

6 Transmembrane Domains (S1-S6) = 1 Subunit.
4 Alpha Subunits= Channel
Channel is a TETRAMER of x4 alpha subunits

23
Q

In a potassium voltage gated ion channel where is the pore region?

A

Between S5+S6.

24
Q

Describe the structure of a sodium/ calcium voltage gated ion channel.

A

Similar to Potassium except 4 homologous domains form 1 protein.

25
Q

Why is the S4 Helices in Voltage gated ion channels special? Why is it special?

A

Voltage Sensor.

Activation/ Deactivation of ion channel.

26
Q

What type of current does positive ions entering the cell/ negative ions leaving the cell give?

A

Negative Current

27
Q

Describe how the neuromuscular junction works?

A
  1. AP arrives at axon terminal of motor neurone.
  2. Voltage gated Calcium channels open so influx of Calcium ions down electrochemical gradient.
  3. Ca 2+ entry- Release of ACh by exocytosis.
  4. Ach diffuses across synaptic cleft and binds to receptors on sarcolemma.
  5. ACh binds to channels - Open Na+ channels- Influx of Na + into muscle fibre and K+ exit. More Na+ enters than K+ leaves.
  6. Local change in membrane potential called END PLATE POTENTIAL.
    Acetylcholine broken down by Acetylcholinerases in synaptic Cleft.
28
Q

Ligand- Gated ion channels.

A

Channels open (or close) in response to certain ligand.

29
Q

What are Ligand- Gated ion channels also known as?

A

Ionic tropic Receptors.

30
Q

What are Ligand- Gated ion channels also known as?

A

Ionic tropic Receptors.

31
Q

What type of ion channels are Cys Loop Receptors? Why are they named Cys Loop Receptors?

A

Ligand- Gated ion channels.

Named after loop made by a disulphide bond between Cysteine residues in the N terminal of extracellular domain.

32
Q

Examples of Cys Loop Receptors:

A

Cationic Channels:
Serotine (5- HT) Receptors
Nicotinic AcetylCholine Receptor
Zinc Activated Receptor

Anionic Channels:
GABA Receptor
Glycine Receptor.

33
Q

Describe the structure in the Cys Loop Receptors receptor?

A

5 Protein Subunits.

34
Q

What type of ion channels are Ionotrophic Glutamate Receptors? What neurotransmitter binds to them?

A

Ligand- Gated ion channels.

Glutamate.

35
Q

Name examples of Ionotrophic Glutamate Receptors Cation Channel classifications:

A

GluA (AMPA)
GluK (Kainate)
GluN (NMDA)
GluD (‘Orphans’)

36
Q

Describe the structure of Ionotrophic Glutamate Receptors.

A

4 subunits each have 4 domains:

  1. Amino- terminal domain.
  2. Extracellular ligand binding domain.
  3. Transmembrane domain.
  4. Intra- cellular carboxyl terminal domain.
37
Q

What are P2X receptors activated by?

A

3x ATP molecules.

38
Q

How many subtypes of P2X receptors are there?

A

7 (P2X1-7)

39
Q

What type of ions do P2X receptors carry?

A

Cations- Mainly 1+ ions but sometimes carry Ca 2+ ions.

40
Q

Where are P2X receptors expressed in?

A
  1. Vas Deferens
  2. Platelets
  3. Neurones
  4. Smooth Muscle
  5. Leukocyte.

Semester 2 Biology Revision (5 decks)

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