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Physiology FoM > Physiology of Ion Distribution > Flashcards

Physiology of Ion Distribution Flashcards

1
Q

What is an ion?

A

Atoms/molecules that carry a net electrical charge

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2
Q

What is a cation?

A

Positive electrical charge

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3
Q

What is an anion?

A

Negative electrical charge

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4
Q

What is ionic charge relative to?

A

Valency

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5
Q

Give examples of physiological ions and their functions

A
  • Sodium= determines osmolarity
  • Potassium= membrane potential
  • Calcium = muscle contraction
  • Phosphate = ATP
  • Hydrogen = pH
  • Chloride = Acid-base
  • Bicarbonate= buffer in the blood
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6
Q

What is the purpose of gradients?

A

Allow storage of potential energy

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7
Q

Give examples of passive transport

A

Filtration and osmosis which require gradients

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8
Q

Give examples of active transport

A

Primary and secondary which require energy

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9
Q

Give examples of vesicular transport

A

Endo and exocytosis

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10
Q

Describe filtration

A
  • Passive movement from high to low hydrostatic pressure
  • Filtration through glomerulus
  • Osmotic pressure in capillary
  • Net difference drives movement
  • Not crossing membranes
  • Occurs between cells without entering cells
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11
Q

Describe passive diffusion

A
  • Selectively permeable membrane
  • Passive diffusion for lipid soluble molecules
  • -> Gases and steroid hormones act as intracellular
  • Down concentration gradinet
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12
Q

Describe facilitated diffusion

A
  • Polar hydrophilic substances as they cannot cross hydrophobic core
  • Requires channel
  • Cells regulate expressed channels, changes permeability
  • This establishes gradients
  • Ionic movement, calcium and sodium moves in potassium out
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13
Q

Describe membrane channels

A
  • Relatively specific, competition can occur for similar molecules (like glucose and galactose)
  • Limited number of carriers available which makes saturation possible (finite movement)
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14
Q

Describe uniports

A

One molecule in

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15
Q

Describe symports

A

Co-transport

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16
Q

Describe antiports

A

One in and one out

17
Q

Describe ligand-gated channels

A

Opened by change in ligand, regulated changes response to stimulus

18
Q

Describe voltage gated

A

Potential change, closed during rest, required threshold potential to open

19
Q

Describe active transport

A
  • Against gradient, requires energy
20
Q

What is primary active transport?

A

Uses ATP (can create gradient)

21
Q

What is secondary active transport?

A

Uses gradients created by primary active transport

22
Q

Describe sodium/potassium ion ATPase

A
  • Na+ binds to the inner membrane
  • ATP is hydrolysed
  • Protein expels sodium
  • Shape of protein reverts and K+ moves in (3rd ATP usage)
23
Q

What is the importance of gradients?

A
  • Gradients store energy
  • Energy expended to create gradient
  • Energy release when molecules diffuse
24
Q

Describe transport for larger molecules

A

Enter via vesicular transport, too big to diffuse or enter channels

25
Q

Describe endocytosis

A
  • Active
  • Phagocytosis, pinocytosis and receptor mediated endocytosis
  • Invaginations form in the membrane as part of continual recycler
  • Vesicles formed traps same extracellular fluid internalising it
  • Vesicles digested and contents recycled
  • Pinocytosis is random/untargeted
26
Q

Describe receptor mediated endocytosis

A
  • More specific forms of transport
  • Target binds to cell-surface receptor, stimulating internalisation of ligand-receptor complex
  • Created vesicle digested and contents used by cell
  • All require energy
27
Q

Describe exocytosis

A
  • Molecules packaged into vesicles
  • Vesicles fuse with membrane
  • Contents released and vesicle recycled
  • Active
  • Membrane could get too big with all the fusion, so recycling occurs
28
Q

Describe relative distributions

A
  • Overall osmolality balanced (extra/intracellularly)
  • Permeability depends on number of available channels
  • All cells have a resting membrane potential
29
Q

Describe membrane potentials and how they are established

A
  • Excitable cells can rapidly change membrane potential- change membrane permeability
  • Electrical gradients
  • > fixed anions in the cell (overall negative in the cell)- proteins and phosphates
  • > Na+/K+ ATPase- one positive charge out- leaves cell relatively negative
  • Ion movement due to both conc. and electrical gradients; ions move down gradients
30
Q

Describe equilibrium potentials

A
  • E.g. potassium
  • Pumped in through Na/K+ pumps at rest K+ leaves cell
  • Charge is not sufficient to hold in K+ - EP= -90mV (no longer diffusion)
  • EP for sodium- +60mV
  • Membrane more permeable to K+, resting potential determined mostly by K+
31
Q

Define equilibrium potential

A

Theoretical voltage difference across membrane when diffusion gradient = electrical gradient

32
Q

Describe action potential

A
  • Changing membrane permeability allows for establishment of new equilibrium
  • Depolarisation causes influx of ions which makes potential positive
  • Change in permeability caused by opening of voltage-gated channels

Physiology FoM (6 decks)

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