Lecture 2 Flashcards
1
Q
Na/K pump
A
- integral protein that exchanges 3 sodium ions ( out) with two potassium ions ( in )
- energy dependent process
2
Q
Na/K pump process
A
- 3 sodium ions bind to intracellular sites of the pump
- phosphate group is transferred to the pump via hydrolysis of ATP
- conformational change occurs, translocating sodium ions across membrane
- conformational change exposes 2 potassium binding site on extracellular surface of pump
- phosphate group is removed, pump returns to original conformation
- this translocates potassium ions across membrane
3
Q
Resting membrane potential
A
- difference in charge across a membrane when a neuron is not firing
- value inside cell relative to extracellular environment ( -70mV )
4
Q
AP - depolarisation
A
- in response to a signal initiated by a dendrite, sodium channels open
- Na+ rushes into the cell down electrochemical gradient
- inside of cell becomes more positive
- outside the cell becomes more negative
5
Q
how does lidocaine work?
A
- lidocaine blocks fast voltage gated Na+ channels
- membrane of the post synaptic neuron can’t depolarise
- neuron will fail to transmit an action potential
- no pain signals propogate to the brain
6
Q
AP - repolarisation
A
- refers to restoration of membrane potential following depolarisation
- Na channels close
- K channels open
- K+ ions more concentrated inside cell
- causes passive efflux of K+ ions
- causes membrane potential to reurn to more negative internal differential
7
Q
AP - hyperpolarisation
A
- instead of going back to normal, extra K+ leaves the cell
- due to K+ channels being slow to close
8
Q
Absolute refractory period
A
- period of time where a 2nd AP cannot occur no matter how strong the stimulus is
- cause : inactivation of Na+ channels ( time taken for channels to rest )
- serves to limit frequency of APs and ensure undirectional APs
9
Q
Relative refractory period
A
- period of time where a 2nd AP can only occur with a stronger than normal stimulus
- cause : some Na+ channels open & can be activated
10
Q
AP - propogation
A
- axon surrounded by myelin
- acts as electrical insulation - less voltage loss - signal travels faster
- speed also depends on diameter
- large diameter - faster velocity
11
Q
why is propogation slower for unmyelinated fibres?
A
in unmyelinated fibres, every part of the axonal membrane needs to undergo depolarisation, propogation slower
12
Q
multiple sclerosis
A
- immune mediated
- demyelination of fibres
- causes slowing of AP propogation
- CNS disease
13
Q
Guillain Barre Syndrome
A
- autoimmune disease
- demyelination of axons
- causes slow propogation of AP
- causes immobility
- can recover
14
Q
Synapses
A
- junction b/w the nerve cell and its target tissue
- are chemical
- central synapse - b/w 2 neurons in CNS
- peripheral synapse - b/w neuron and muscle or gland
15
Q
Neurotransmitter termination
A
3 ways
* reuptake by astrocytes where the neurotransmitter is stored or destroyed by enzymes
* degradation by enzymes in synaptic cleft such as AChE
* diffusion of neurotransmitter as it moves away from synapse