Chapter 7 Homework

Action potentials arriving at a presynaptic terminal cause

calcium ion channels to open.

IPSPs always open K+ channels. T/F?

False

Depolarization of a cell membrane occurs because

More sodium ions diffuse into the cell than potassium ions diffuse out of it

The convergence of many presynaptic terminals onto one postsynaptic neuron is called: temporal summation. synaptic plasticity. spatial summation. an EPSP.

Spatial summation

Which of the following is/are a location of nicotinic ACh receptors? autonomic ganglia specific regions of the brain skeletal muscle All of the above

All of the above

Acetylcholine is actively transported from the pre-synaptic membrane to the postsynaptic membrane. T/F?

False

Acetylcholine is broken down into acetic acid and cholinesterase by choline. T/F?

False

Action potentials can travel in both directions on the axon. T/F?

False

Action potentials travel faster on thin, myelinated axons than on thick, myelinated axons.

False

EPSPs and IPSPs have a long-term effect on a neuron. T/F?

False

The sodium-potassium pump uses bulk transport to move the sodium and potassium ions. T/F?

Fasle

Hyperpolarization that leads to postsynaptic inhibition is a/an.. NMDA. LTP. EPSP. IPSP.

IPSP

Acetylcholine has which effect on the postsynaptic neuron?

Ligand-gated sodium ion channels open and sodium diffuses in.

When a neurotransmitter binds to a nicotinic receptor, the ion channel opens and... only Na+ diffuses into the cell. only K+ diffuses into the cell. Na+ diffuses into and K+ diffuses out of the cell simultaneously. Both Na+ and K+ diffuse into the cell.

Na+ diffuses into and K+ diffuses out of the cell simultaneously.

During depolarization, which of the following statements about voltage-gated ion channels is TRUE? K+ gates open before Na+ gates Na+ gates open before K+ gates Na+ and K+ gates open at the same time Na+ gates open while K+ gates remain closed K+ gates open while Na+ gates remain closed

Na+ gates open before K+ gates

Successive EPSPs from a presynaptic terminal to a postsynaptic neuron is called: temporal summation. synaptic plasticity. spatial summation. divergence.

Temporal Summation

Once threshold is reached on the postsynaptic membrane, an action potential is generated and propagated over the muscle cell membrane.

True

Threshold is the minimum current required for the cell membrane to generate an action potential. T/F?

True

Select the correct word from the list to complete each sentence.

When Na⁺ diffuses into the cell, the cell becomes more depolarized. Na+ diffusing into the cell causes more Na+ gates to open, which is a positive feedback loop. When K⁺ diffuses out of the cell, the cell becomes less depolarized. K⁺ diffusing out of the cell has a negative feedback effect on the initial depolarization. The voltage-gated Na⁺ channels open when the cell membrane reaches threshold level as a result of a stimulus. The voltage-gated Na⁺ channels close when the cell reaches +30 mV.

The period of time when a membrane cannot respond to another stimulus, no matter how strong, is the __________________________________________ relative refractory period. All-or-None period. absolute refractory period. after-potential period.

absolute refractory period.

Absolute refractory period causes...

action potential propagation to occur in one direction

Which type of neuroglial cell supports the metabolic needs of the blood-brain barrier? oligodendrocytes Schwann cells microglia ependymal cells astrocytes

astrocytes

An EPSP will cause...

both sodium and potassium gates to open, allowing sodium to diffuse into the cell and potassium to diffuse out of the cell.

An action potential arriving at the presynaptic terminal causes...

calcium ions to diffuse into the cell.

What is the function of acetylcholinesterase? binds to nicotinic receptors catalyzes resynthesis of ACh blocks muscarinic receptors catalyzes hydrolysis of ACh to remove it from the synaptic cleft

catalyzes hydrolysis of ACh to remove it from the synaptic cleft

The neurotransmitter in the neuromuscular junction...

causes ligand gated sodium channels in the muscle fiber to increase their permeability to sodium, which depolarizes the postsynaptic membrane.

An action potential _____.

causes the inside of the neuron cell membrane to become positively charged in reference to the outside.

Upon arriving at the node of a myelinated neuron, the excitatory postsynaptic potential (EPSP) ____.

causes the neurons inner cell membrane to become more positively charged.

In the neuromuscular junction, acetylcholine...

diffuses across the synaptic cleft and binds to acetylcholine receptors on the postsynaptic muscle fiber.

Depolarization occurs because...

more sodium ions diffuse into the cell than potassium ions diffuse out of it.

What type of cells produce the myelin sheath in the central nervous system (CNS)? Schwann cells microglia oligodendrocytes astrocytes

oligodendrocytes

Repolarization occurs because...

potassium ions continue to diffuse out of the cell after the inactivation gates of the voltage-gated sodium ion channels begin to close.

Opening of sodium channels and sodium influx causes _____.

sodium ions diffusing through the intracellular fluid of the internode to the next node

Which of the following statements about the resting membrane potential is TRUE? the exterior of the cell has a net negative charge and the interior has a net positive charge the exterior of the cell has a net negative charge and the interior is neutral the exterior of the cell has a net positive charge and the interior has a net negative charge the exterior of the cell has a net positive charge and the interior is neutral the exterior of the cell is neutral and the interior has a net negative charge

the exterior of the cell has a net positive charge and the interior has a net negative charge

Hyperpolarization, or afterpotential occurs because...

the increased potassium ion permeability lasts slightly longer than the time required to bring the membrane potential back to its resting level.

Depolarization of the postsynaptic membreane by an excitatory postsynaptic potential (EPSP) causes ____.

the sodium channels open and sodium ions pour into the intracellular fluid.

An action potential arriving at the presynaptic terminal causes _____. voltage-gated sodium ion channels to open, and sodium ions to diffuse into the cell. voltage-gated sodium ion channels to open, and sodium ions to diffuse out of the cell. voltage-gated calcium ion channels to open, and calcium ions to diffuse into the cell. acetylcholine to diffuse into the cell. ligand-gated sodium channels to open, and sodium ions to diffuse out of the cell.

voltage-gated calcium ion channels to open, and calcium ions to diffuse into the cell.

An inhibitory post synaptic potential (IPSP)...

will make the membrane potential of a neuron's inner cell membrane more negative.

When threshold is reached in a neuron, depolarization occurs with the same amplitude of potential change. This is known as:

*the All-or-None Law. cable properties of axons. a graded response. salutatory conduction.

An excitatory post synaptic potential (EPSP)...

will make the membrane potential of a neuron's inner cell membrane more positive.

Number the events of neurotransmitter release from the synaptic terminal in the correct order Exocytosis of neurotransmitter into synaptic cleft Extracellular Ca2+ enters terminal and binds to sensor protein in the cytoplasm Ca2+-protein complex stimulates fusion of the docked synaptic vesicle with the plasma membrane Action potential reaches axon terminal Voltage-gated Ca2+ channels open

5. Exocytosis of neurotransmitter into synaptic cleft 3. Extracellular Ca2+ enters terminal and binds to sensor protein in the cytoplasm 4. Ca2+-protein complex stimulates fusion of the docked synaptic vesicle with the plasma membrane 1. Action potential reaches axon terminal 2. Voltage-gated Ca2+ channels open

A recently depolarized area of a cell membrane cannot generate an action potential because of the

Absolute refractory period

Receptors that bind the neurotransmitter at the postsynaptic cell membrane are voltagegated. T/F?

False

All neurotransmitters are made from amino acids. T/F?

False

After the passage of the action potential, the sodium-potassium pump reestablishes the resting membrane potential. T/F?

True

During the transmission of an action potential along the neurilemma of a myelinated neuron, as one node is repolarizing, the next node is depolarizing. T/F?

True

If the postsynaptic membrane potential reaches threshold level, an action potential will be produced. T/F?

True

Nicotinic receptors are also ion channels. T/F?

True

The area between the presynaptic nerve cell and the postsynaptic muscle cell is termed the synaptic cleft. T/F?

True

The inflow of sodium ions into the intracellular fluid causes depolarization of the neuron's inner cell membrane. T/F?

True

The nerve impulse is an electrical current that travels along dendrites or axons. T/F?

True

The neurotransmitter at the neuromuscular junction is_______

acetylcholine.

An action potential generates local currents that tend to _____ the membrane immediately adjacent to the action potential.

depolarize

What structures are involved in electrical synapses?

gap junctions