Synapse and RMP

Question 1

What is a general characteristic of a synapse?

Answer 1

• a synapse is a site at which a neuron transmits a nerve impulse to another neuron
• where neurons communicate with other cells

Question 2

What is a presynaptic neuron?

Answer 2

• sends impulse

- cell before the synapse

Question 3

What is a postsynaptic neuron

Answer 3

• receives impulse

- cell after the synapse

Question 4

What is a synaptic cleft?

Answer 4

• separates 2 neurons

Question 5

How does synaptic transmission work?

Answer 5

• a one-way transfer of info
• impulse travels down axon of presynaptic neuron to axon terminal
• when impulse reaches synaptic knob, causes influx of calcium ions
• this leads to release of neurotransmitters from styptic vesicles by exocytosis
• neurotransmitter will exert either excitatory or inhibitory effect on postsynaptic neuron

Question 6

What is cell membrane potential?

Answer 6

• a cell membrane is usually electrically charged, or polarized, so that the inside of the membrane is negatively charged with respect to the outside of the membrane
• this is a result of unequal distribution of ions on the inside and the outside of the membrane
• important in conduction of impulses in neurons and muscle fibers

Question 7

What are 3 types of cell membrane potentials?

Answer 7

• Resting membrane potential
• Local/graded potentials
• Action potentials

Question 8

What is the definition of membrane potential?

Answer 8

• a charge inside of a cell
• indicates that there is potential for charges to move across the cell membrane
• When charges flow from one area to another they create an electrical current

Question 9

What is the resting membrane potential in a neuron?

Answer 9

• about -70mV (millivolts)

- this is when neurons rest or are inactive

Question 10

What is the resting cell membrane more permeable to?

Answer 10

• potassium ions rather than sodium ions
• calcium ions are less able to cross the resting cell membrane than sodium and potassium, and have a special role in neuron function

Question 11

What happens before the membrane potential is established?

Answer 11

• potassium ions diffuse out of the cell faster than sodium ions diffuse in
• A net loss of positive charge from the cell results

Question 12

What is the function of the Na+/K+ pump that maintains the concentration gradients for Na+ and K+ ions?

Answer 12

• the membrane potential is negative on the inside of the membrane and aids in sodium diffusion into the cell, and opposes potassium diffusion out of the cell
• as a result, slightly more sodium ions enter the cell than K+ ions leave
• the sodium/potassium pump balances these movements by maintaining the concentrations of these ions and the resting membrane potential

Question 13

Constant activity of the Na+/K+ pump requires a constant supply of which substance?

Answer 13

• ATP

Question 14

What is the net effect of the constant diffusion of sodium/potassium ions?

Answer 14

• three sodium ions “leak” into the cell for every two potassium ions that “leak” out
• The Na+/K+ pump balances these leaks by pumping three sodium ions out for every two potassium ions it pumps in

Question 15

What is action potential?

Answer 15

• A rapid change in the membrane potential
• First in the pos. direction
• Secondly, in the neg. direction
• Then returns to resting membrane potential
• when a neuron conducts an electrical current, that current is in the form of a series of action potentials occurring in sequence along the axon, from the cell body to the axon terminal

Question 16

When is a neuron considered at “rest?”

Answer 16

• it’s membrane is polarized, because there are more positive ions outside the cell, and more negative ions inside the cell - which creates a charge difference across the membrane

Question 17

What does the sodium potassium pump do to maintain RMP?

Answer 17

• is an active transport mechanism that carries more sodium and less potassium ions across the membrane to maintain this charge difference

Question 18

What is it called when an electrical charge flows thru a dendrite?

Answer 18

• local membrane potential
• a dendrite detects. stimulus and a sodium channel in its plasma membrane opens and lets sodium into the neuron
• the influx of positive ions reverses the charge across a particular section of the membrane, in a process called depolarization