Week 1: Ion Channels, Resting Membrane & AP I

Question 1

What are the two main cell types in the nervous system?

Answer 1

Neurons and glial cells.

Question 2

What are the primary functions of astrocytes?

Answer 2

Support neurons, anchor them to capillaries, regulate blood-brain barrier, mop up K+ and neurotransmitters.

Question 3

What is the role of microglial cells?

Answer 3

Monitor neuronal health and transform into macrophages to remove debris.

Question 4

What do ependymal cells do?

Answer 4

Line ventricles and help circulate cerebrospinal fluid.

Question 5

Which glial cells form the myelin sheath in the CNS?

Answer 5

Oligodendrocytes.

Question 6

Which glial cells form the myelin sheath in the PNS?

Answer 6

Schwann cells.

Question 7

What is the function of satellite cells?

Answer 7

Provide support to neuronal cell bodies in the PNS, similar to astrocytes.

Question 8

Define afferent neurons.

Answer 8

Neurons that carry sensory information to the CNS.

Question 9

Define efferent neurons.

Answer 9

Neurons that carry motor commands from the CNS to muscles.

Question 10

What are interneurons and their types?

Answer 10

CNS-only neurons; local (short distances) and projection (long distances).

Question 11

What is the function of neuroendocrine cells?

Answer 11

Release hormones into the blood to affect distant organs.

Question 12

What is the integration zone of a neuron?

Answer 12

Axon hillock, where action potentials are initiated.

Question 13

What structures make up the neuronal cytoskeleton?

Answer 13

Microtubules (transport), neurofilaments and microfilaments (rigidity).

Question 14

What are Nodes of Ranvier?

Answer 14

Gaps in myelin sheath that facilitate saltatory conduction.

Question 15

What structures make up a typical neuron?

Answer 15

Dendrites, cell body, axon, and axon terminals.

Question 16

What are the three main regions of ion channels?

Answer 16

Funnel-shaped entrance, central pore, and exit region.

Question 17

What determines ion movement through a channel?

Answer 17

Whether the channel is open, the concentration gradient, and the electrical gradient.

Question 18

What are non-gated ion channels?

Answer 18

Channels that are always open, allowing passive ion flow.

Question 19

How do chemically-gated ion channels operate?

Answer 19

Open in response to binding of specific ligands like neurotransmitters.

Question 20

Where are chemically-gated channels typically located?

Answer 20

At synapses between neurons.

Question 21

How do voltage-gated channels work?

Answer 21

Open or close in response to changes in membrane potential.

Question 22

What is a mechanically-gated ion channel?

Answer 22

Opens or closes in response to physical deformation like pressure.

Question 23

What does it mean when a channel is refractory?

Answer 23

It is closed and cannot reopen until reset.

Question 24

List one reason a channel may become refractory.

Answer 24

Voltage, binding of a chemical, or removal of an activating chemical.

Question 25

What is ion selectivity in channels based on?

Answer 25

Charge and hydrated size of the ion.

Question 26

Why can't Na+ pass through K+ channels?

Answer 26

Hydrated Na+ is larger than hydrated K+.

Question 27

Why are channels passive transporters?

Answer 27

Ions move along concentration and electrical gradients without energy.

Question 28

What is the role of protein subunits in ion channels?

Answer 28

They form the structure and determine selectivity.

Question 29

Which ion channel type is involved in sensory reception?

Answer 29

Mechanically-gated ion channels.

Question 30

What is the significance of the axon hillock?

Answer 30

It is the primary site for action potential initiation.

Question 31

What is the typical resting membrane potential (RMP) of a neuron?

Answer 31

-70 mV.

Question 32

What causes the resting membrane potential?

Answer 32

Unequal ion distribution, mainly K+ and Na+.

Question 33

What is depolarization?

Answer 33

Decrease in membrane potential (more positive).

Question 34

What is hyperpolarization?

Answer 34

Increase in membrane potential (more negative).

Question 35

What equation calculates ion equilibrium potential?

Answer 35

The Nernst equation.

Question 36

What does the Nernst equation consider?

Answer 36

Concentration gradient of a single ion.

Question 37

Why is the resting potential closer to K+ equilibrium?

Answer 37

Membrane is more permeable to K+ at rest.

Question 38

What is the Goldman equation used for?

Answer 38

Calculating membrane potential considering multiple ions.

Question 39

Why can't Nernst fully explain RMP?

Answer 39

It only accounts for one ion at a time.

Question 40

What is the role of Na+/K+ ATPase pump?

Answer 40

Maintains Na+ and K+ gradients using ATP.

Question 41

What are leak channels?

Answer 41

Always-open channels that allow ions like K+ and Na+ to passively move.

Question 42

Why is the interior of the neuron negative?

Answer 42

Due to K+ efflux and impermeable anions.

Question 43

What is an equilibrium potential?

Answer 43

The voltage at which an ion’s net flow is zero.

Question 44

How does ion movement affect membrane potential?

Answer 44

Ions move down gradients, altering charge difference.

Question 45

What ions are mainly involved in RMP?

Answer 45

Potassium (K+) and sodium (Na+).

Question 46

What initiates an action potential?

Answer 46

A stimulus strong enough to reach threshold (-55 mV).

Question 47

What ion influx causes depolarization?

Answer 47

Sodium (Na+).

Question 48

What happens during repolarization?

Answer 48

Potassium (K+) exits the cell.

Question 49

What is the peak membrane potential during an action potential?

Answer 49

Approximately +30 mV.

Question 50

What causes hyperpolarization after an action potential?

Answer 50

Delayed closure of K+ channels.

Question 51

What is the refractory period?

Answer 51

Time when a neuron cannot fire another action potential.

Question 52

How is the RMP restored after an action potential?

Answer 52

Na+/K+ pump restores ion distribution.

Question 53

What is the axon hillock's role in action potentials?

Answer 53

Acts as the trigger zone for AP initiation.

Question 54

What determines the strength of a stimulus?

Answer 54

Whether it reaches threshold and triggers an AP.

Question 55

Why don’t weak stimuli trigger APs?

Answer 55

They fail to depolarize the membrane to threshold.

Question 56

How do graded potentials differ from action potentials?

Answer 56

Graded are local; action potentials travel long distances.

Question 57

What channel state prevents back-to-back APs?

Answer 57

Refractory (inactive) state of Na+ channels.

Question 58

Why does K+ movement lead to hyperpolarization?

Answer 58

K+ efflux continues briefly after threshold is restored.

Question 59

What direction does Na+ move during an action potential?

Answer 59

Into the cell.

Question 60

How does the action potential propagate?

Answer 60

Sequential opening of voltage-gated Na+ channels.