9.4 LH

The electrical properties of cells are the result of

Ion concentration differences across the plasma membrane

The ____________ part refers to the identical action potentials created throughout a cell's membrane; the ____________ indicates that an action potential is not generated if the threshold is not met.

"All", "none"

Sodium channels and some potassium channels are ____________ ; potassium diffuses ____________ the cell. Inside of cell membrane is ____________ charged relative to outside.

Closed, out of, negatively

The cycle of a mysosin molecule forming cross-bridges, moving, then releasing and returning to its original position is called _____________.

Cross bridge movement

The ____________ principle refers to the creation of an ____________ potential along a muscle cell membrane.

All-or-none, action

____________ enter the axon terminal leading to the release of acetylcholine via ____________ .

Calcium ions, exocytosis

The organophosphate poisons found in insecticides cause death by spastic paralysis of the respiratory muscles. Which of the following may be a mechanism of the poison?

Decrease in acetylcholinesterase activity

This level is the amount of ____________ that must occur along the plasma membrane prior to an action potential being created.

Depolarization

The role of the drug neostigmine in the treatment of myasthenia gravis is to partially block the action of acetylcholinesterase (AChE). Blocking AChE will therefore result in ______________.

Increased stimulation of the muscle cell

Acetylcholine receptors function as ____________ .

Ligand-gated ion channels

Sodium channels are ____________ ; sodium diffuses ____________ the cell. Inside of cell membrane becomes ____________ charged relative to outside.

Open, into, positively

Once this level is reached, changes in membrane ____________ occur, which lead to the creation of an action potential.

Permeability

Excitation-contraction coupling begins with ______________.

Production of an action potential on the sarcolemma

The charge difference across the plasma membrane of an unstimulated cell is called the __________.

Resting membrane potential

Which of the following lists the structures in the order they participate in excitation-contraction coupling?

Sarcolemma; T tubules; sarcoplasmic reticulum; calcium ions

Depolarization of the cell membrane occurs when there is a rapid influx (inflow) of

Sodium ions

In response to acetylcholine binding, ____________ move into the muscle fiber causing the membrane potential to rise.

Sodium ions

The ____________ channels close; ____________ channels open; potassium diffuses out of the cell. Again, the ____________ becomes negatively charged relative to the ____________ .

Sodium, potassium, inside of the cell membrane, outside of the cell membrane

Acetylcholine diffuses across the ____________ before binding to its receptor located on the ____________ .

Synaptic cleft, motor end plate

Each presynaptic terminal contains ___________, which contain the neurotransmitter __________ that, when released, cause ligand-gated Na+ channels to open in the motor end-plate. This causes __________ in the muscle cell.

Synaptic vesicles; acetylcholine; depolarization

The plasma membrane of an excitable cell is more permeable to potassium ions because

There are more leak ion channels for K+ than Na+

The all-or-none states that an action potential will not be created until a critical level, or ____________ , is met.

Threshold

When the membrane potential reaches ____________ , an action potential spreads across the sarcolemma due to the opening of ____________ .

Threshold, voltage-gated Na+ channels

If a stimulus is strong enough to produce a depolarization that reaches (or exceeds) threshold, all of the permeability changes responsible for an action potential proceed without stopping.

True

An action potential reaches the axon terminal causing ____________ to open.

Voltage-gated Ca2+ channels