Physiology of Neurons Flashcards
Which channels help a cell maintain its resting membrane potential?
- Na+ and Ca2+
- Na+ and K+
- Na+ and Cl-
- Na+ and Po
2 - Na+ and K+ leaking channels (slow leaking)
- Na+ = 2 molecules leave the cell
- K+ = 3 molecules enter the cell
What is the function of the Na+/K+ pump?
- transfer 3 Na+ out of the cell
- transfer 2 K+ into the cell
- requires ATP to memtain membrane potential
What is required for a voltage gated channel to open?
- ligand binding
- neurotransmitters recognised in synaptic cleft
- change in membrane potential
- GPCR to activate
3 - change in membrane potential
- Must be above a specific threshold (tissue dependent)
- remain closed when membrane is at resting state
What is the equilibrium potential?
- voltage is the same across membranes due to fluid levels
- voltage is the same across membranes do to neurotransmitter concentration
- voltage is the same across membranes due to balance between ion concentration and voltage of electrical energy
3 - voltage is the same across membranes due to balance between ion concentration and voltage of electrical energy
- ion concentration and electrical potential energy are equal
What is the general concentration of Na+ inside and outside the nerve cell?
- inside = 10mM and outside = 145mM
- inside = 140mM and outside = 4mM
- inside = 140mM and outside = 145mM
- inside = 10mM and outside = 140mM
- inside = 10mM and outside = 145mM
What is the general concentration of K+ inside and outside the nerve cell?
- inside = 10mM and outside = 145mM
- inside = 140mM and outside = 4mM
- inside = 140mM and outside = 145mM
- inside = 10mM and outside = 140mM
2 - inside = 140mM and outside = 4mM
What are the 4 stages of the action potential graph in order?
- voltage rises above threshold, de-polarisation, re-depolarisation, hyper-polarisation
- de-polarisation,, voltage rises above threshold, re-depolarisation, hyper-polarisation
- voltage rises above threshold, de-polarisation, hyper-polarisation, re-depolarisation
- hyper-polarisation , voltage rises above threshold, de-polarisation, re-depolarisation
- voltage rises above threshold, de-polarisation, re-depolarisation, hyper-polarisation
- 1 - voltage of cell increases and threshold is reached
- 2 - depolarisation occurs
- 3 - repolarisation occurs
- 4 - resting state (following hyperpolarisation)
In an action potential, what channels help maintain a membrane potential of around -70mV?
- Cl- and Na+
- Na+ and K+
- K+ and Cl-
- K+ and Ca2+
- Na+ and K+
* These channels are leaky Na+ and K+ leaky channels
Once an action potential is received, what happens to generate an action potential and allow the cell to reach its membrane potential?
- Cl- channels open
- K+ channels open
- Ca+2 channels open
- Na+ channels open
- Na+ channels open
- Na+ channels open and Na+ influx inside cell
- membrane potential reaches threshold and we get depolarisation
Once the neuronal cell has received an action potential, Na+ has rushed inside the cell through Na+ voltage gated channels, depolarisation occurs. In addition to Na+ channels, what other main channel drives depolarisation?
- Cl- channels open
- K+ channels open
- Ca+2 channels open
- Na+ channels open
- K+ channels open
- K+ voltage channels open and K+ leaves the cell
- K+ rushes out of the cell
When a cell is undergoing hyperpolarisation, is the cell able to receive another action potential?
- no
- Na+ voltage pump cannot open
What does propagation of an action potential mean?
- a Na+ channel opening then opens a K+ channel and continues
- a K+ channel opening then opens a Na+ channel and continues
- a Na+ channel opens which stimulates surrounding Na+ channels to open
- a Na+ channel closes then closes other Na+ channel and continues
3 - a Na+ channel opens which stimulates surrounding Na+ channels to open
- one Na+ voltage channel opens stimulating surrounding channels
- action potential spreads to surrounding Na+ channels
To facilitate saltatory conduction there is a specific channel that is densely populated at the nodes of Ranvier. Which channels are these?
- Na+ voltage gated channels
- K+ voltage gated channels
- Ca2+ voltage gated channels
- Cl- voltage gated channels
- Na+ voltage gated channels
What are the 2 different types of synapse?
1 - chemical (more common)
2 - electrical (physically connected)
What are graded potentials and their function?
- small temporary changes in membrane potential
- large static changes in membrane potential
- small permanent changes in membrane potential
- large permanent changes in membrane potential
- small temporary changes in membrane potential
- alone there are insufficient to reach threshold
- lots of graded potential combined can facilitate depolarisation
What are the 2 types of graded potentials?
1 - hyperpolarising graded potential
2 - depolarising graded potential
Can graded potentials create an action potential alone?
- No
- but with lots of of them then YES, accumulate to cross the threshold
Carbamazepine is a drug that is used to treat epilepsy, functioning as an anti convulsant (GABA agonist). What is its mechanism of use?
1 - bind and inhibit Na+ channels so no action potential and depolarisation
2 - bind and inhibit K+ channels so no action potential and depolarisation
3 - bind and inhibit Ca2+ channels so no action potential and depolarisation
4 - bind and inhibit Cl- channels so no action potential and depolarisation
1 - binds and inhibits Na+ channels reducing depolarisation and action potential
- act as an agonist of GABA and ensure depolarisation occurs less or not at all
Carbamazepine is a drug that is used to treat epilepsy, functioning as an anti convulsant. It works by binding to and in inhibiting voltage gated Na+ channels, increases the threshold, so it is harder to reach an action potential. Does Carbamazepine work on everyone?
- no
- 30% of patients develop resistance related to genetics
Lidocaine is a local anaesthetic (means only a small part of the body is treated and patient is generally awake) medication that is used to block pain sensations in a wide variety of superficial and invasive procedures. Lidocaine is able to inhibit action potentials, therefore reducing the sensation of pain in the CNS. What is the mechanism of action of Lidocaine?
1 - enters cell, ionised, binds with K+ channels and keeps them closed
2 - enters cell, ionised, binds with Ca2+ channels and keeps them closed
3 - enters cell, ionised, binds with Na+ channels and keeps them closed
4 - enters cell, ionised, binds with Po+4 channels and keeps them closed
3 - enters cell, ionised, binds with Na+ channels and keeps them closed
- able to pass into the cell
- due to lower pH inside cell Lidocaine is ionised and cannot leave the cell
- ionised lidocaine then binds with Na+ channels and keeps them closed
Sodium Valproate is an anticonvulsant medication that is used primarily in the treatment of epilepsy and neuropathic pain. It have been shown to have a broad spectrum and reduce action potentials. What is its mechanism of action?
1 - binds and inhibits Na+ and Ca2+ channels reducing depolarisation and action potential
2 - binds and inhibits K+ and Na+ channels reducing depolarisation and action potential
3 - binds and inhibits Cl- and K+ channels reducing depolarisation and action potential
4 - binds and inhibits Mg+ and Ca2+ channels reducing depolarisation and action potential
1 - binds and inhibits Na+ and Ca2+ channels reducing depolarisation and action potential
- acts as an agonist on GABA receptors
