Lecture 5 Flashcards
(7 cards)
1
Q
What does a neuron do?
A
- Passes a signal
- a communication device
- a neuron can be quiet in a resting state - the resting membrane potential
2
Q
What is the resting membrane potential?
A
- Using an electrode to measure the membrane potential of a neuron reads -70mv
- the resting membrane potential has different concentrations of ions inside and outside the neuron
- the inside of the neuron is the more -ve than the outside (thats why its -ve)
- there are more Na+ ions outside the cell
- there are more K+ ions inside the cell
- if the membrane was there, there would be a balance of + and -, the membrane causes the imbalance
- it takes a lot of hard work/energy to maintain the resting membrane potential
3 forces/pressures act to maintain the unequal distribution of ions in the resting membrane potential
- Electrochemical pressure
- concentration gradient
- sodium-potassium pump
3
Q
What is the resting membrane potential ionic basis?
A
Salts in a solution exist as negative and positive ions (+ve cations and -ve anions):
- Atoms normally have the same number of positively charged protons and negatively charged electrons
- if it loses and electron it becomes overall more positive
- if it gains an electron it becomes overall more negative
4
Q
What are the 2 passive forces that work on these ions of the resting membrane potential?
A
- Electrostatic pressure:
- The -ve charge inside the cell attracts cations (+ve ions) into the cell - Pressure from the concentration gradient:
- Ions (atoms) move from a location of high concentration to an area of low concentration
5
Q
What is the 1 active force that works on these ions of the resting membrane potential?
A
Sodium-potassium pump:
- There is a great pressure on Na+ atoms to enter the cell
- there is a great pressure on K+ atoms to exit the cell
- they do this with difficulty because the channels through the membrane are almost shut
- despite this, a few pass through
- For every 3 Na+ ions that are moved out
- 2 K+ ions are moved in
- this takes a lot of energy
- there is great pressure for Na+ ions to ‘flood’ into the neuron and for K+ ins to rush out
6
Q
What is the Action Potential?
A
- The threshold of excitation (-70mv to -50mv)
- sodium channels open
- Na+ rushes in = +50mV
- K+ ions rushes out
- sodium channel closes; K+ ions still comes in
- potassium channel closes
- Polarised: The neuron in the resting membrane potential (-70mV)
- Depolarised: in the action potential (+50mV)
- Repolarised: back to -70mV
- Hyperpolarised: drops below -70mV
7
Q
What is the transmission of the action potential?
A
A series of ‘train’ of action potentials
