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Medicine Sem 1 > Physiology week3,4,5 > Flashcards

Physiology week3,4,5 Flashcards

1
Q

Name the 2 types of simple diffusion

A

Simple and facilitated

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2
Q

Name and describe the 2 types of diffusion

A

Simple diffusion : Where molecules move through the membrane openings or spaces without interactions with carrier proteins .
Facilitated diffusion : Where carrier proteins help transport molecules by binding with them and moving them through the membrane

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3
Q

NAME the 2 pathways of simple diffusion

A

Through the lipid bilayer and
Through protein channels

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4
Q

Explain the 2 pathways of simple diffusion

A

1.Through the lipid bilayer
- Where lipid soluble substances like oxygen, nitrogen, carbon dioxide and alcohols dissolve in the lipid bilayer and diffuse easily .
2. Through protein channels
Where water and small insoluble molecules pass through the channels in protein molecules embedded in the membrane .

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5
Q

How is water diffused?

A

Through aqaporins

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6
Q

Explain the structure of protein pores

A

They are integral membrane proteins that form open tubes that allow substantances to move by simple diffusion from one side to another

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7
Q

Name 2 features of a protein pore and what they provide and give an example of what they cause

A

The diameter of a pore and its electrical charges provide selectivity that allows only certain molecules to pass through .
E.gAquaporins which have a narrow pore that allow water molecules to diffuse through the membrane but the pores is too narrow for hydrated ions

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8
Q

Name 2 features of a protein pore and what they provide and give an example of what they cause

A

The diameter of a pore and its electrical charges provide selectivity that allows only certain molecules to pass through .
E.gAquaporins which have a narrow pore that allow water molecules to diffuse through the membrane but the pores is too narrow for hydrated ions

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9
Q

Explain the potassium channel selectively-

A
  • The potassium channels allow potassium ions to pass more easily than sodium ions due to a specific selectivity filter lined with carbonyl oxygen which intercats with the potassium ions and excludes Na ions.
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10
Q

Explain the sodium channel selectivity

A
  • Na channels have a narrow selectivity filter lined with negatively charged amino acids that attract and allow sodium ions to pass while excluding other ions.
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11
Q

Why is the sodium channel selectivity important?

A
  • It is crucial for cellular function as it ensures that Na ions can pass through the channels under normal conditions
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12
Q

What is the role of Gating of protein channel

A

They control ion permeability by opening or closing channles in response to stimuli

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13
Q

Name the types of gatings

A
  • Voltage
  • Chemical(Ligand) gating
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14
Q

Explain both types of gating without examples

A

VOLTAGE
- The gate responds to changes in electrical potential across the cell membrane
CHEMICAL(LIGAND)
-The gate opens when a chemical(ligand) binds to the protein, causing a confromational change

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15
Q

Give examples for both types of gating

A

Voltage
- A negative charge inside the membrane keeps the Na channels closed but when the membrane looses its negativity the Na channels open allowing the ions to pass
Chemical(ligand)
- The nerotransmitter acetylcholine binding to its receptors opening a channel for ion passage facilitating nerve signal transmission

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16
Q

What is the patch clamp method?

A

A technique used to measure ion current through single channels by creating a seal between a micropipette and a small membrane path

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17
Q

Name the factors affecting net rate of diffusion

A
  • Concentration difference across the membrane
  • The membrane electrical potential
  • The pressure difference across the membrane
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18
Q

What is Osmosis?

A
  • It refers to the net movement of water across a selectively permeable membrane from an area of high water concentration to an are of low water concentration
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19
Q

What is the role of the selectively permeable membrane in osmosis

A

Allows water to pass more easily than solutes like Na and Cl

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20
Q

Name the factors affecting osmotic pressure

A
  1. The number of osmotic particles
    - the number of solute particles
  2. Osmole
    - If a substance dissociates the number of osmoles increases with the number of ions
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21
Q

What is Osmolality?

A

The concentration of osmotically active particles in osmoles

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22
Q

What is the osmotic pressure

A

The pressure required to stop osmosis. It is determined by the concentration of non-diffusible solute particles on one side of the membrane.

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23
Q

What is Active transport?
+ the substances they move

A

It moves substances across the cell membrane against their conentration gradient, requiring enrgy
substances include: Na, Cl, K, H, ca ions
and certain sugars and amino acids

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24
Q

Name and describe the types of Active Transport

A
  • Primary AT
  • Energy is dervied from the breakdown of ATP
    Secondary ATP
  • Which uses energy stored in ionic concentration differences created by PAT
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25
Q
  • What mechanism does Primary Active Trasnport use
  • What is the function
  • And its importance
A

Mechanism: Sodium-Potassium Pump
Function: It pumps Na ions out of the cell and K ions in.
It uses ATP to exchange 3 Na ions out of the cell and 2 K ions in the cell
Importance: -Mainatais cell volume . -Creates cells negative electrical potential, cruicial for nerve function

26
Q

What is the Mechanism for the primary Active transport of Calcium ions and its function

A

Mechanism Calcium Pump
- It pumps calcium out of the cells or into organelles, maintaining low cytosolic calcium levels

27
Q

What is the Mechanism for the primary active transport of hydrogens and where is it found

A
  • Hydrogen Pump
    It is found in the gastric glanels and kidney tubules
28
Q

What 2 types of transport are in Secondary Active Transport

A
  • co transport and counter transport
29
Q

Describe the role and give examples of the 2 types of transport in Secondary Active Transport

A

-Co-Transport (Symport): Substances are transported in the same direction as sodium ions.
Examples: Glucose and amino acids are co-transported into cells with sodium.
-Counter-Transport (Antiport): Substances are transported in the opposite direction of sodium.
Examples: Sodium-calcium exchange and sodium-hydrogen exchange, important for calcium and pH regulation.

30
Q

What is the definition of the Nerst potential

A

-It is the diffusion potential across a membrane that exactly counteracts the net diffusion of a particular ion

31
Q

What is the Neest potential based on

A

The concentration gradient of the ions across the membrane

32
Q

How is the magnitude of the nerst potential determined ?

A
  • By the ratio of the concentrations of the specific ion on the two sides of the membrane
33
Q

What does the formula for the Nerst potential assume

A

It assumes the potential in the ECF remains at zero potential

34
Q

How is the membrane potential measured?

A
  • By inserting a micropipette filled with electrolyte solution into a cell or nerve fibres
35
Q

What is the role of the voltmeter

A
  • It measures the potential difference between the inside and outside of the cell
36
Q

What is the resting membrane potential?

A
  • -70 mv
37
Q

why is the resting membrane potenital negative?

A
  • The sodium potassium pump actively transports Na ions out of the cell and K ions in the cell in the ratio of 3 Na + out for every 2 K + in.
  • This creates a deficient + ions, resulting a negative potential inside the membrane
38
Q

What happens in Potassium lekage?

A
  • The potassium ions can leak out of the cell through potassium ‘leak’ channels, which are 100 times more permeable to potassium than sodium.
39
Q

What is the definition of action potential

A
  • A rapid change in membrane potential ., propagating along the nerve fibre, transmitting signals
40
Q

What happens at the resting stage

A

-The memabrans is polarised at -70mv

41
Q

What happens in depolarisation

A
  • Membrane becomes permeable to Na ions, Na ion channel opens
  • Allows the postively charged sodium ions o difffuse through the membrane
  • Making it more postively charged
42
Q

What happens in repolarisation

A
  • The Na ion channels close
  • K ion channels open
    They excite the cell , restoring the negative resting potential
43
Q

Explain activaton,in the voltage-gated sodium channels

A

When the membrane potential becomes less negative, rising from the -70mv to near -55mv, the activation gates open allwoing a large influx of sodium ion.

44
Q

What happens in inactivation in the voltage gated sodium ion channels

A
  • A slower process closes the inactivation gate after a brief time, stopping the sodium ions influx
45
Q

What happens in resting in the voltage gated sodium channels

A

The sodium channels cannot open till the memrbane returns to its resting state

46
Q

What happens in the resting state of the voltage gated potassium channels

A
  • The gate is close, preventing k ions from exititng
47
Q

What happens in activation in the voltage gated potassium ion

A

The activayion gate opens when the membrane potential rises towards 0 allowing potassium ions to flow out

48
Q

Explain the timing stage in the voltage gated potassium channels

A

The potassium channels open as the sodium channels inactivate, speeding up repolarisation

49
Q

What is the nerst equation used to calculate

A

The equillibirum potential for an ion at a given concentration difference acroos a membrane

50
Q

What is the goldman equation

A

Used to calculate the diffusion potential when the membrane is permeabke to several differentions

51
Q

What is the refractory period?

A
  • When another Action potential cannot be generated in an excitable cell
52
Q

what happens in the propogation of an action potential

A

An action potential excites the adjacent regions of the membrane, sending signals along the membrane

53
Q

Explain the mechanism of propogation of Action potential

A
  • The sodium influx in depolarised areas generate postive charges which spread along the axon
  • These positive charges deoplarise the adjcant regions, opening the sodium channels and propogating the action potential further
54
Q

What is the direction of propgation

A

An action potential travles in all directions from the stimulus point convering the enitre excitable membrane

55
Q

What is the All or nothing principle

A
  • One an action potential is triggered at a point at point on the membrane, it propogates across the enitre membrane if the conditions are favourable
    If the condiitons are not favourable action potentil does not propogate
56
Q

What are the key features of the All or nothing principle

A

For propogation to occur the acion potential must reach a certain voltage, to stimulate adjacent membrane areas

57
Q

Explain the mylinated nerve fibres.

A
  • Large with thick mylein sheath that surrounds the axon
58
Q

What is myelin sheath formed by ?

A

Schwaan cells that create layers rich in sphingomylein

59
Q

what is Saltory conduction

A
  • Action potentials only occur at the node of ranvier
  • impulses jump from node to node through extracelluler fluid
60
Q

What are the advantages of Salatory conduction?

A
  • Increased speed
  • Energy efficient

Medicine Sem 1 (18 decks)

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