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
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2
Q

Na/K pump process

A
  1. 3 sodium ions bind to intracellular sites of the pump
  2. phosphate group is transferred to the pump via hydrolysis of ATP
  3. conformational change occurs, translocating sodium ions across membrane
  4. conformational change exposes 2 potassium binding site on extracellular surface of pump
  5. phosphate group is removed, pump returns to original conformation
  6. this translocates potassium ions across membrane
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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 )
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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
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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
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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
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7
Q

AP - hyperpolarisation

A
  • instead of going back to normal, extra K+ leaves the cell
  • due to K+ channels being slow to close
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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
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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
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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
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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

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12
Q

multiple sclerosis

A
  • immune mediated
  • demyelination of fibres
  • causes slowing of AP propogation
  • CNS disease
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13
Q

Guillain Barre Syndrome

A
  • autoimmune disease
  • demyelination of axons
  • causes slow propogation of AP
  • causes immobility
  • can recover
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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
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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

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16
Q

serotonin

A
  • neurotransmitter that affects mood
  • lack of it believed to be a cause of depression
  • prozac prescribed as an antidepressant
  • prozac block serotonin re-uptake (prolongs effect of serotonin)