Chapter 4: How do Neurons Use Electrical Signals to Transmit Information?

Question 1

Resting potential

Answer 1

Electrical charge across the cell membrane in the absence of stimulation

A store of negative energy on the intracellular side at -70 millivolts relative to the extracellular side

1. Because the membrane is relatively impermeable to large molecules, the negatively charged proteins remain inside the cell.
2. Ungated potassium and chloride channels allow potassium and chloride ions to pass freely, but gates on sodium channels keep out positively charged sodium ions.
3. Na+–K+ pumps extrude Na+ from the intracellular fluid and inject K+.

Question 2

Resting potential Associated ions?

Answer 2

Sodium (Na+) and chloride (Cl−)
Higher concentration outside cell

Potassium (K+) and large proteins (A−)
Higher concentration inside cell

Question 3

Graded potentials

Answer 3

Hyperpolarization -> Inhibition
Depolarization -> excitation

membrane potential that vary in size, as opposed to being all-or-none

Question 4

Hyperpolarization

Answer 4

efflux of potassium and influx of Cl- makes the extracellular side of the membrane more positive

Question 5

Depolarization

Answer 5

influx of Na+ through sodium channels

Question 6

Nerve impulse

Answer 6

A WAVE OF DEPOLARIZATION ACROSS THE MEMBRANE, THIS IS THE SIGNAL, Propagation of an action potential on the membrane of an axon

Question 7

Nodes of Ranvier

Answer 7

• Part of an axon that is not covered by myelin
• Tiny gaps in the myelin sheath
• Enables saltatory conduction
• Saves time in generating an action potential, more axons in brain,

Question 8

Saltatory conduction

Answer 8

the action potential jumps rapidly from node to node, doesn’t need to restart the action potential

Question 9

Action potential

Answer 9

• Transmitting information down that neuron
• Generate an action potential, lasts 1 millisecond
• Large, brief reversal in polarity of an axon
• Gets to about 30 mv and goes to -90 all in one millisecond

Question 10

Threshold potential

Answer 10

• Voltage on a neural membrane at which an action potential is triggered
• Opening of Na and K voltage-activated channels
• Approximately - 50 Mv relative to extracellular surround

Question 11

Voltage-activated ion channels

Answer 11

• Gated protein channels that open or close only at specific membrane voltages
• Sodium (Na+) and potassium (K+),
• Closed at membrane’s resting potential
• Na+ channels are more sensitive than K+ channels and, therefore, open sooner.

Question 12

Absolute refractory period

Answer 12

an action potential cannot be fired, occurs after an action potential is fired

no way an action potential is fired because gate 2 of sodium channels is closed

Question 13

Relatively refractory period

Answer 13

an action potential cannot be fired, occurs after an action potential is fired

it could happen, potassium channels are still open, the gates are not repolarized yet

Question 14

Multiple sclerosis

Answer 14

If myelin is damaged, a neuron may be unable to send any messages over its axon

MS the myelin formed by oligodendroglia is damaged, which disrupts the functioning of neurons whose axons it encases

Question 15

Myasthenia gravis

Answer 15

a chronic autoimmune, neuromuscular disease that causes weakness in the skeletal muscles that worsens after periods of activity and improves after periods of rest

Caused by an error in the transmission of nerve impulses to muscles. It occurs when normal communication between the nerve and muscle is interrupted at the neuromuscular junction—the place where nerve cells connect with the muscles they contro