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NAS Basic Processes
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1The lipid bilayer is a [blank_start]hydrophobic[blank_end] environment. This means that it is [blank_start]impermeable[blank_end] to most molecules including [blank_start]ions[blank_end] (they are usually [blank_start]hydrophilic[blank_end]). This means that intracellular and extracellular compartments are established with very different [blank_start]ionic[blank_end] compositions. Ion [blank_start]pumps[blank_end] are used to [blank_start]maintain[blank_end] the gradient.
- Ahydrophobic
- Bimpermeable
- Chydrophilic
- Dions
- Epumps
- Fmaintain
- Gionic
2The inside of a cell contains a slight excess of [blank_start]anions[blank_end] which sets up a [blank_start]negative[blank_end] voltage inside the cell. This voltage is known as the [blank_start]membrane potential[blank_end] (Em). In neurons this is usually about [blank_start]-65[blank_end]mV. Em is determined by the [blank_start]balance[blank_end] of charges.
- Aanions
- Bnegative
- Cmembrane potential
- D-65
- Ebalance
3Ion movement across the membrane is [blank_start]passive[blank_end]. Ion channels are therefore required. There are a few [blank_start]permeant[blank_end] ions (ions that can pass through the channels): Na+, K+, [blank_start]Ca2+[blank_end], Cl-. There are three different types of ion channels that are available:
Non-gated ([blank_start]leak[blank_end]): these set the [blank_start]Em[blank_end] of the resting membrane
[blank_start]Voltage[blank_end]: generate the action potential
[blank_start]Ligand[blank_end] (chemical): generate the Em changes at the [blank_start]synapse[blank_end]- Apassive
- Bpermeant
- CCa2+
- Dleak
- EEm
- FVoltage
- GLigand
- Hsynapse
4The [blank_start]resting membrane potential[blank_end] of the cell is about -65mV. There are several factors that cause this:
1) the [blank_start]chemical[blank_end] gradient - this is set up due to the [blank_start]potassium[blank_end] [blank_start]efflux[blank_end].
2) the electrical force - the [blank_start]potassium[blank_end] [blank_start]efflux[blank_end] results in the inside being more [blank_start]negative[blank_end] than the outside. This causes [blank_start]potassium[blank_end] influx. At [blank_start]resting membrane potential[blank_end] there is no net movement of [blank_start]potassium[blank_end].
3) the [blank_start]permeability[blank_end] of the membrane to each ion - how easy it is for ions to move across the membrane through ion [blank_start]channels[blank_end].
The following assumptions are made:
- the membrane is only permeable to [blank_start]potassium[blank_end]
- the Em is initially [blank_start]0[blank_end]- Aresting membrane potential
- Bchemical
- Cpotassium
- Defflux
- Epotassium
- Fefflux
- Gnegative
- Hpotassium
- Iresting membrane potential
- Jpotassium
- Kpermeability
- Lchannels
- Mpotassium
- N0
5Which of the following is true about the Nernst and Goldman equation?
- AThe Nernst equation defines the value at which the potassium ions are just in excess of the sodium ions.
- BFor potassium ions, the E(K) value is about -80mV
- CFor sodium ions, the E(Na) value is about -62mV
- DIf E(m) doesn't equal the E(ion) value, it is due to an imbalance in electrical and chemical effects. This is called to potential driving force.
- EThe value of the resting membrane potential is closer to the E(K) value because here the membrane is more permeable to potassium.
- FThe Goldman equation is used to calculate the E(m) and where it lies between E(Na) and E(K).
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- Description
- Medicine Quiz on NAS Basic Processes, created by H G on 03/04/2019.
- Author
- H G
- Language
- English
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- 12
- History
- Created on 3 Apr 2019 · updated on 4 Apr 2019
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