Module 3 Flashcards
What types of glial cells are in the CNS?
astrocytes, microglia, ependymal cells, oligodendrocytes
What times of glial cells are in the PNS?
Satellite cells and schwann cells
What functions do astrocytes provide the CNS?
- Structural support
- Regulate extracellular concentration of ions and neurotransmitters
- Formation of the
blood‐brain barrier
… and … form myelin sheaths around axons
Oligodendrocytes and Schwann cells
T or F
Resting membrane potential is negative in all cells
T
T or F
In all cells there are gradients of ions across the cell membrane
T
T or F
The inside of a cell’s membrane is positive relative to the outside
F
negative
How many sodium and potassium ions are outside the cell during resting membrane potential?
5mM K+
150mM Na+
How many sodium and potassium ions are inside the cell during resting membrane potential?
140mM K+
15mM Na+
The membrane at rest has many open … channels and few open … or … channels.
K+
Na+
Cl-
Na+/K+‐ATPase pumps … Na+ out and … K+ in
3
2
Buildup of ‐ve charge in a neuron is limited by the … gradient vs the … gradient of …
electrical
chemical
K+
The equilibrium potential in a neuron is approx …mV
‐70
T or F
Resting membrane potentials are dependent on voltage-gated ion channels
F
Voltage-gated ion channels are required for action potentials, not resting membrane potentials.
T or F
All cells have a membrane potential
T
… cells experience rapid changes in membrane potential
Excitable
T or F
Ionic gradients are not important in all cells
F
List some excitable cells
Neurons, myocytes and pancreatic beta cells
T or F
Even without an action potential, an axon has many ions moving across its membrane
T
Na+/K+ pumps get their energy from …
ATP
T or F
Na+/K+ pumps passively transport ions across the cell
F
actively
Na+/K+ pumps transport … ions out of the cell and … ions in
sodium
potassium
T or F
Some potassium channels are open all the time, allowing potassium ions to leave the cell
T
T or F
There are only a few constitutively open K+ channels in a cell membrane
F
There are many
T or F
There are only a few constitutively open Na+ channels in a cell membrane
T
T or F
K+ ions are of high concentration in a cell
T
Why do K+ ions have a tendency to diffuse from the inside of a cell to the outside?
Because there is a high concentration of K+ ions in a cell, creating a concentration gradient that moves K+ to the outside of a cell
Why is the chemical gradient of a cell membrane being reduced in a resting membrane potential?
Because potassium ions are moving from a high concentration inside the cell to a low concentration outside the cell.
Why does the electrical gradient of a cell membrane increase during resting membrane potential?
Because the inside of a cell at resting membrane potential is already negative so when K+ are moved out of the cell it becomes even more negative.
If the only channels open in a cell membrane were potassium channels, the value of the membrane potential would be…
EK = -90mV
If the only channels open in a cell membrane were sodium channels, the value of the resting membrane potential would be…
ENa = +65mV
What is the resting membrane potential of most cells?
-70mV
How many mM of Cl- are present in the inside and outside of a cell at resting membrane potential?
10mM of Cl- inside and 120mM of Cl- outside
What happens to a cell’s membrane potential during hyperpolarisation?
The inside of the cell membrane becomes more negative due to the opening of voltage-gated K+ channels and the subsequent movement of K+ out of the cell.
What happens to a cell’s membrane potential during depolarisation?
The inside of a cell membrane becomes more positive due to the opening of voltage-gated Na+ channels and the subsequent movement of Na+ into the cell.
… occurs when a stimulus lowers a cell’s membrane potential (mV) to lower than it is at resting membrane potential without a stimulus.
Hyperpolarisation
… occurs when a stimulus raises a cell’s membrane potential (mV) to higher than it is at resting membrane potential without a stimulus.
Depolarisation
T or F
Action potentials are all-or-nothing
T
T or F
The magnitude of an action potential is dependent on the strength of the original stimulus.
F
Because it is an all-or-nothing reaction it is independent.
T or F
Action potentials are fast (1-2 milliseconds) and have high frequencies
T
T or F
K+ channels transition from closed, open and inactivated stages.
F
Na+ channels do. K+ channels transition from open to closed.
What happens during the repolarisation of an action potential?
K+ channels open and K+ rush out
Na+ channels are inactivated and then start to close
What happens during the undershoot of an action potential?
Small hyperpolarisation
Also need Na+/K+-ATPase to restore Na+ and K+ concentrations.
What happens during the resting state of an action potential?
Voltage-gated ion channels are closed
What happens during the stimulus phase of an action potential?
A STIMULUS causes a few Na+ channels to open Na+ rushes in
What happens during the depolarisation phase of an action potential?
If THRESHOLD is reached:
Lots of Na+ channels open
Lots of Na+ rushes in
What happens during an absolute refractory period?
no AP can be generated
– Na+ channels open then inactivated
What happens during a relative refractory period?
AP only if apply large stimulus
– because some Na+ channels closed again
T or F
During the refractory period, the action potential can only fire in one direction
T