Unit 1 - Resting/Action/ Post synaptic potentials

Question 1

What is an ‘excitable’ cell?

Answer 1

cell that responds to stimuli by producing a current generating an AP

Question 2

what are the concentrations of these molecules in ICF?

• Na+
• K+
• Cl-

Answer 2

Na+ = 15
K+ = 150
Cl - = 5

Question 3

what are the concentrations of these molecules in ECF?

• Na+
• K+
• Cl-

Answer 3

Na+ = 145
K+ = 5
Cl - = 100

Question 4

how does an AP start?

Answer 4

• sensory transduction: activation of sensory receptor which converts external stimulus into AP
• but must be suprathreshold to elicit AP

Question 5

What are the two parts of refractory period?

Answer 5

Absolute RP: second AP cannot be generated immediately after first - because sodium channels have not reverted to closed state (inactivated)
Relative AP: reduced excitability so stronger than normal stimulus required to elicit AP

Question 6

how is a compound AP generated and what is it?

Answer 6

electrical stimulus applied to nerve trunk which produces compound AP = summed activity of all nerve fibres in the trunk

Question 7

why will a number of peaks appear when recording cAP of a stimulated long nerve?

Answer 7

reflects the differences in conduction velocity(speed at which they conduct AP) in the fibres

Question 8

what factors affect the conduction velocity?

Answer 8

• diameter (resistance)
• myelination
• capacitance (how quickly membrane responds to change in current)

Question 9

what is the phenomenon of accommodation? what is the significance of this?

Answer 9

• occurs due to inactivation of Na+ channels
• maintained depolarisation of membrane leads to increase in threshold
• prevents fatiguing the neuron which could result in neural death

Question 10

what is the difference between fast and slow synaptic transmission? give functional significance of these

Answer 10

• fast: neurotransmitter binds to ligand-gated ion channel =fast, short-lived/ useful for rapid processing of info/mvt
• slow: neurotransmitter binds to G protein-linked receptor = slow, long lived/ useful for regulation/ autonomic system

Question 11

what is the difference between fast excitatory and inhibitory synaptic transmission?

Answer 11

• excitatory - binds to/open non-selective cation channels heading to EPSP (depolarisation of postsynaptic nerve cell)
  inhibitory - activates chloride channels
• hyperpolarisation in postsynaptic membrane = IPSP (negative shift in membrane potential)

Question 12

what is frequency and long term potentiation?

Answer 12

short intervals between successive AP leads to increase in amplitude due to increase of neurotransmitter
- long term: increase in amplitude sustained for hours