L14

Question 1

what are excitable cells and what are their properties

Answer 1

• Neurons
  
  • Muscles
    ○ Skeletal
    ○ Cardiac
    ○ Smooth
  • Properties
    ○ Irritability- read to respond
    Conductivity- able to conduct electrical signals

Question 2

describe the process of signals traveling through a neuron

Answer 2

• Signal arrives at dendrites
  
  • Summation + nerve impulse generated at axon hillock (trigger zone)
  • Travels along axons, jumping across myelin- conduction zone
    Signal passed through and released through axonal terminals- output zone

Question 3

why is membrane potential neg. at resting

Answer 3

• At rest, inside of membrane is neg.
  
  • This is due to
    ○ Unequal distribution of ions across membrane + selective permeability to NA+ and K+
    ○ Most anions (neg.) cannot leave cell
    ○ Na+/K+ pumps burn ATP to keep RMP in place

Question 4

what are the 3 types of potential

Answer 4

resting membrane potential (RMP)
graded potential (GP)
action potential (AP)

Question 5

how to maintain resting membrane potential

Answer 5

§ Can change slightly
§ Maintenance depends on type of ion channels + flow of ions down electrochemical gradient
§ Change in charge may produce GP or AP
Is -70mV

Question 6

explain graded potential

Answer 6

§ Can trigger a large change in membrane potential
§ Production depends on resting membrane potential + ion changes
§ Must ‘add up’ to a certain value to trigger AP

Question 7

explain action potential

Answer 7

Production depends on graded potentials + ion channels

Question 8

why is there more K+ channels then Na+ channels

Answer 8

• At rest membrane is 50-70 times more permeable to K+ than Na+
  
  • More K+ leaky channels then for Na+
  • This is because if Na+ was continuously leaking along both electrical + chemical gradients over time, would destroy membrane potential + K+ gradient
  • Prevented by Na+/K+ pump actively transporting Na+ OUT and K+ in
    Actively contributes to membrane potential

Question 9

why is RMP important?

Answer 9

• Because change sin membran potential determines the relative excitability of a cell
  
  • Affects its ability to communicate
  • Membran potential changed by triggering events

Question 10

explain E ion

Answer 10

• Is equilibrium potential of an ion
  When conc. Gradient for an ion is balance

Question 11

explain channel opening and closing

Answer 11

• Some may be permanently open (leaky)
  
  • Others gated, alternative in response to stimuli
  • E.g.
    ○ Ligands- chemically gated ion channels
    ○ Physical force- mechanically gated ion channels
    Electrical/membrane potential- voltage gated ion channels