BPS 402 EXAM 3

neuro unit; he said he focuses a lot on conceptual stuff and not necessarily memorization

Is neuron signaling an electric or chemical process?
Why? What is this process called?

Chemical process

Release of NT from pre-synaptic cleft, binds to receptors on post-synapse

Process is called synaptic transmission or neurotransmission

Why is resting membrane potential NEGATIVE?

Leak K+ channels are open at rest

Is there a higher concentration of K+ inside or outside the cell?

Inside the cell

Is there a higher concentration of Na+ inside or outside the cell?

Outside the cell

Is there a higher concentration of Cl- inside or outside the cell?

Outside the cell

Is there a higher concentration of Ca2+ inside or outside the cell?

Outside the cell

Why is there a low concentration of Na+ inside the cell, and a high concentration of K+ inside the cell?

Na+/K+ ATPase pump

• For every ATP molecule used:

  • 3 Na+ ions are pumped OUT of the cell

  • 2 K+ ions are pumped INTO the cell

Are nerve signals traveling along the nerve fibers chemical or electrical? Why? What is this process called?

They are electrical impulses

• Change in voltage across the cell membrane

• Electrical signaling is faster than chemical signaling, can pass along a message faster

Called action potentials

Describe the activation of ligand-gated ion (ionotropic) channels

Opens in response to a specific NT

Describe the activation of mechanically-gated ion channels

Open in response to pressure or tension on the membrane

Describe activation of voltage-gated channels

Selectively permeable to specific ions

• Opens in response to changes in membrane potential (membrane voltage)

What is a leakage channel

An ion channel that is always open

Why do cells have a negative resting membrane potential?

In terms of potassium

1. K+ concentrations are greater inside the cell & K+ ion channels are open at rest

   • K+ responsible for hyperpolarization and makes the cell more negative

In terms of sodium

1. Na+ concentrations are lower inside the cell

   • Na+ responsible for depolarization, makes the cell more positive

POTASSIUM > SODIUM = NEGATIVE

What role does Cl- play in AP?

Opening of Cl- channels hyperpolarizes the cell

• More negative

• Less excitable

• Less likely to conduct nerve impulse/AP

What role does Ca2+ play in AP?

Opening of Ca2+ channels depolarize the cell

• More positive

• More excitable

• More likely to conduct nerve impulses/AP

How do dendrites receive information from other neurons?

Synaptic transmission, release of NTs

What role do inhibitory NTs/inhibitory signals play in terms of AP?

Either directly or indirectly hyperpolarize the membrane (decrease voltage inside the cell)

What role do excitatory NTs/excitatory signals play in terms of AP?

Either directly or indirectly depolarize the membrane (increase voltage inside the cell)

How do NTs generate APs?

1. Directly (ionotropic) or indirectly (metabotropic) activate ion channels on the postsynaptic neuron

2. Can depolarize or hyperpolarize postsynaptic cell membrane

3. If the sum of NT voltage signaling excites (depolarizes) the postsynaptic neuron than an AP chain rxn is initiated at the post-synaptic neuron

Why is AP only initiated when the neuronal membrane hits a threshold value?

Voltage-gated Na+ ion channels are only activated once the membrane potential hits this value / is sufficiently depolarized

• Influx of Na+ from these ion channels results in rapid electrical response

Describe action potential

Wave of depolarization that travels along an axon. It is propagated by the sequential opening of voltage-gated Na+ channels

Is GABA inhibitory or excitatory

Inhibitory

Is glutamate inhibitory or excitatory

Excitatory

Describe the activation process of voltage-gated Na+ channels

1. At rest, the channel is closed.

2. Channel is activated by depolarization of cell membrane (meets threshold value)

3. Activation gate opens, Na+ flows into the cell

4. After the cell is depolarized, the inactivation gate closes the channel

5. After the cell is repolarized by K+, the activation gate closes, and the inactivation gate opens

   • The channel remains inactivated until the cell meets threshold value

Describe the “resting” state of AP

Concentration of K+ is higher than Na+ inside the cell, membrane is most permeable to K+