Chapter 12 : Nervous Tissue

As electrical charge is re-established back to -70mV, the ______________ returns the ions to their initial position with sodium more highly concentrated in the ECF

ATPase pumps

Receptors that bind the neurotransmitter at the post synaptic cell membrane are voltage-gated. T/F

False

Prior to the arrival of a signal from a presynaptic input, the post-synaptic membrane is polar with a greater relative ____________ charge in the ECF.

positive

An action potential arriving at the presynaptic Terminal causes what to occur?

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

Place the following structures in order that an electrical impulse would travel beginning with the post-synaptic membrane. dendrites, soma, internode, axon hillock, node of ranvier, axon terminals, terminal arborization

1) Dendrites 2) Soma 3) Axon Hillock 4) Internode 5) Node of Ranvier 6) Terminal Arborization 7) Axon Terminals

Arrange the following in the order in which they occur at the postsynaptic side of a neuromuscular junction: 1) An action potential is propagated over the muscle cell membrane 2) Depolarization of the postsynaptic membrane 3) Sodium ions move into muscle cell

3, 2, 1 -Sodium ions move into muscle cell -Depolarization of the postsynaptic membrane -An action potential is propagated over the muscle cell membrane

If acetylcholinesterase became mutated and nonfunctional, what would be the immediate result?

Acetylcholine would build up in the synaptic cleft

Place the following labels in the proper position to designate action potential or local potential.

Action potential -Voltage-regulated sodium channels -Voltage-regulated potassium channels -Rate of transmission is increased with myelination -Important for transmission over long distances -Require threshold Local potential -Ligand-regulated sodium channels -Cause summation -Decremental -Reversible Both -Sodium-Potassium ATPase pumps work to re-establish RMP

An unmyelinated fiber has voltage gated ion gates along its entire __________. An action potential at the __________ causes sodium to diffuse into the cell. This results in membrane __________. The depolarization causes a __________ that excites the entire membrane. This continues until the traveling signal reaches the end of the __________.

An unmyelinated fiber has voltage gated ion gates along its entire LENGTH An action potential at the TRIGGER causes sodium to diffuse into the cell. This results in membrane DEPOLARIZATION. The depolarization causes a REPITITION that excites the entire membrane. This continues until the traveling signal reaches the end of the AXON.

If a drug was developed that interfered with the proper functioning of the microtubules found within the axons of neurons, how would you expect this to impact axonal transport processes?

Both anterograde and retrograde transport processes would cease

At the synaptic knob, voltage-gated ____________ channels open, thereby stimulating the synaptic vesicles to release their neurotransmitters by exocytosis

Calcium

The presynaptic membrane releases (via exocytosis) acetylcholine (ACh) into the ____________________.

ECF of the synaptic cleft.

Acetylcholine is actively transported from the presynaptic membrane to the postsynaptic membrane. T/F

False

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

False, uses counter transport

The movement of positive charges to the ________ causes the relative charge across the membrane to become positive in the inner surface.

ICF

Resting membrane potential is created as a result of a greater net flow of positive charges from the __________________.

ICF to the ECF.

When voltage-gated sodium channels are open, sodium flows ____________ the neuron making the inside of the cell more _____________.

Into; Positive

Acetylcholine has which effect on the postsynaptic neuron?

Ligand gated sodium ion channels open and sodium diffuses in.

The ACh diffuses across the cleft and binds to the ____________________ channels.

Ligand-Regulated Sodium

During depolarization, which of the following statements about voltage-gated ion channels is true?

Na+ gates open before K+ gates

Place each label in the appropriate position to designate the appropriate glial cell.

Oligodendrocytes -Form the myelin sheath in the CNS Ependymal Cells -Ciliated cells resembling epithelium -Produce and circulate CSF Microglia -Macrophages of the CNS Astrocytes -Most abundant CNS glial cells -Multi-functioning cells involved with neurogenesis, scar formation, etc. Schwann Cells -Form the myelin sheath in the PNS -Insulate neurons and enhance the rate of transmission in the PNS Satellite Cells -Surround and insulate cells of the PNS and found around the somas

Though potassium and sodium both leak through the membrane at rest, there is a greater diffusional flow of ____________ at rest.

Potassium

In somatic neurons, an action potential arrives at the synapse causing synaptic vesicles to fuse with the ________________ membrane.

Pre-synaptic

_______________ is the time between signals sent from the same presynaptic terminal increases the strength of the graded potential. This is an example of ______________ summation.

Reducing; Temporal

Activated (open) sodium channels allow a rapid diffusion of ____________ down it's electrochemical gradient towards the ICF.

Sodium

The electrical and chemical gradients for ______________ are both high during resting membrane potential which results in a very high electrochemical gradient towards the inside of the cell.

Sodium

What happens as a result of ion flow at a presynaptic terminal?

Synaptic vesicles migrate to the plasma membrane and release acetylcholine.

If demyelination occurs, why don't action potentials occur at regions of the axon that were previously myelinated?

These regions lack the appropriate concentration of voltage-gated sodium channels.

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

True

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

True

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

True

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

True

The sodium-potassium pump is involved in establishing the resting membrane potential. T/F

True

The primary neurotransmitter at the neuromuscular junction is _______________.

acetylcholine

Neurotransmitter release from the presynaptic membrane ceases an existing ACh in the cleft is broken down by ____________.

acetylcholinesterase

In order to maintain the electrochemical gradients for sodium and potassium, ATPase pumps move these ions __________ their respective gradients.

against

Substances that cause facilitation of a neuron

cause the neuron to fire that may not fire under the same circumstances in the absence of the facilitator

A resting membrane potential of -70 mV indicates that the

charges lining the inside of the plasma membrane are negative compared to the charges lining the outside

The enzyme choline acetyltransferase catalyzes the reaction between acetyl-CoA and choline resulting in the formation of the neurotransmitter acetylcholine. This enzyme is produced within the cell body of neurons, but the synthesis of acetylcholine occurs within the axon terminals. Which statement best describes the axonal transport mechanism associated with this process?

choline acetyltransferase is transported in the anterograde direction

Demyelination diseases cause a(n) ______________ in the conduction velocity of action potentials

decrease

With a ______________, the ligand-regulated channels begin closing as they release their bound ACh.

decreasing cleft concentration of ACh

The diffusional movement of sodium and potassium across the membrane is driven at all times by the ____________ .

electrochemical gradient

Action potentials occur

in the unmyelinated regions of an axon

Without continued sodium influx into the cell through the ligand-regulated channels, the constant ________________ causes the membrane potential to return back to the RMP.

leak of potassium to the ECF

Graded potentials result from the opening of

ligand-gated channels

Why does depolarization occur?

more Na+ diffuse into the cell than K+ diffuse out of it

Assume in a laboratory you were able to isolate a neuron and remove the Acetylcholine receptors from the postsynaptic membrane. The substance _____________ would no longer cause facilitation of this neuron

nicotine

An inhibitory postsynaptic potential results from the opening of

potassium and/or chloride channels

Why does repolarization occur?

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

Graded potentials are produced within the _______________ segment of a neuron

receptive

The following information best describes the ____________ phase of an action potential - A membrane potential reading of +10 mV - Inactivated voltage-gated sodium channels - Open voltage-gated potassium channels

repolarization

Suppose that a new virus is discovered that specifically infects motor neurons. Assume that this virus enters neurons conjunction with choline molecules. Once inside the cell, the virus enters the nucleus and replicates. Which direction describes axonal transport route taken by this virus?

retrograde transport

Normally, sodium and potassium leakage channels differ because

sodium ions diffuse through leakage channels into the cell, but potassium ions diffuse through leakage channels out of the cell

Which of the following statements about the resting membrane potential is true?

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

Why does hyperpolarization occur?

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

Indicate the summative effect that brings the initial segment closest to threshold.

two EPSPs in proximity to each other