connect exam 3

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

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

presynaptic

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

ECF of the synaptic cleft.

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

ligand-regulated sodium

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

sodium

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

ICF

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

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

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

Synaptic vesicles migrate to the plasma membrane and release acetylcholine.

Acetylcholine has which effect on the postsynaptic neuron?

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

True or false: If the postsynaptic membrane potential reaches threshold level, an action potential will be produced.

true

true or false: Acetylcholine is actively transported from the presynaptic membrane to the postsynaptic membrane.

false

- muscle spindles are the receptor
- initiated by an increase in muscle length
- is monosynaptic

stretch reflex

- marked by removal of the body from injurious elements

flexor reflex

- utilizes an integrating center

all reflexes

- inhibits excessive muscle contraction
- tendon organs are the receptors

tendon reflex

- marked by actions to stabilize the limb opposite of injurious agents
- is contralateral
- marked by actions that stabilize the contralateral limb

crossed-extensor reflex

Which spinal nerve roots carry sensory nerve signals?

Posterior

In an adult, the spinal cord ends at which vertebra?

Between L1 and L2

cervical enlargement

lumbosacral enlargement

medullary cone

cuada equina

terminal filum

dural sheath

subarachnoid space

A damaged ________ nerve fiber may regenerate if its soma is intact and some neurilemma remains.

peripheral

When a nerve fiber is cut, the fiber distal to the injury _______ survive.

cannot

Near the site of injury, the basal lamina and the neurilemma form a ________ tube.

regeneration

The tube guides the growing sprout back to the original target cells, reestablishing ________ contact.

synaptic

When contact is established, the ________ shrinks, and reinnervated muscle fibers regrow.

soma

A

- Na+ arrive at the axon hillock and depolarize the membrane at that point
- potential across the membrane is becoming less negative

B

- -55 mV
- at threshold, voltage-gated Na+ channels open quickly

C

- voltage-regulated K+ channels open

D

- hyperpolarization

E

- resting membrane potential
- -70 mV

Which of the following are made of gray matter?

Anterior, posterior, and lateral horns

What is the loose connective tissue surrounding an individual nerve fiber called?

Endoneurium

what neurons: One axon; multiple dendrites

Multipolar neurons

what neurons: One axon; one dendrite

Bipolar neurons

what neurons: A single process

Unipolar neurons

what neurons: No axon; multiple dendrites

Anaxonic neurons

Why is myelin important?

- It speeds up signal conduction in the nerve fiber.
- It is formed to assist in the regeneration of damaged fibers.
- It insulates the nerve fiber.

anatomical features of a neuron.

What are the three general classes of neurons that correspond to the three major aspects of nervous system function?

- Motor neurons that send signals predominantly to muscle and gland cells
- Interneurons that lie between, and interconnect the incoming sensory pathways and the outgoing motor pathways of the CNS
- Sensory neurons that are specialized to detect stimuli such as light, heat, pressure, and chemicals and transmit information about them to the CNS

he reflex that results in quick contraction of the same muscle stimulated is called the _________ reflex.

stretch

A reflex hammer striking the tendon is the ________ that triggers the __________.

stimulus; receptor

The afferent neuron synapses with the ___________ in the integrating center.

efferent neuron

This makes it a(n) ___________ reflex arc

monosynaptic

If we are using the patellar ligament as the example, the quadriceps muscles are the _________.

effectors

The antagonists will be inhibited. This is an example of __________.

reciprocal inhibition

Assume all of the presynaptic synapses identified produce EPSPs. If two of these synapses fired simultaneously, which synaptic combination brings the initial segment closest to threshold based on spatial summation?

3 and 4

Graded potentials result from the opening of

ligand-gated channels

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

Two EPSPs in proximity to each other

_______________ 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

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

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

lumbosacral enlargement

thoracic region

cervical enlargement

cervical region

- medullary cone
- cauda equina
- terminal filum

sacral and lumbar region

Which portion of a reflex arc is located entirely within the central nervous system?

Interneuron

true or false: Reflexes have four important properties: they require stimulation, they are quick, they are involuntary, and they are stereotyped.

true

Which of the following cause a postsynaptic transmission to stop?

- Diffusion of the neurotransmitter into the nearby extra-cellular fluid
- Reuptake of the neurotransmitter by endocytosis
- Degradation of the neurotransmitter in the synaptic cleft

regions of a neuron

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

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

spinal nerves: Sacral plexus

L4, L5, and S1-S4

spinal nerves: Brachial plexus

C5 to T1

spinal nerves: Lumbar plexus

L1-L4

spinal nerves: Cervical plexus

C1-C5

diverging neural cicuits

converging neural circuits

parallel after-discharge neural circuits

reverberating neural circuits

spinal nerves and their plexuses

Which term describes all neurons that carry signals towards the CNS?

Afferent

anatomical features of the neuroglia

action potential order: 1

a neuron starts at its resting membrane potential

action potential order: 2

excitatory postsynaptic potentials (EPSP's) are received

action potential order: 3

Na+ flows into the cell making the inside more positive

action potential order: 4

the cell reaches threshold

action potential order: 5

voltage-gated Na+ channels open

action potential order: 6

an action potential is generated

An unmyelinated fiber has voltage-gated ion gates along its entire _______

length

An action potential at the ________ zone causes sodium to diffuse into the cell.

trigger

This results in membrane ___________

depolarization

The depolarization causes a _________ that excites the entire membrane.

repetition

This continues until the traveling signal reaches the end of the ___________

axon

anatomical features of a neuron

anatomical features of the spinal cord

Which of the following describes a reverberating circuit?

There is a prolonged or repetitive effect that lasts until one or more neurons in the circuit fail to fire or until an inhibitory signal from another source stops one of them from firing. Neurons stimulate each other in a linear sequence such as A→B→C→D, but neuron C sends an axon collateral back to A.

anatomical features of a neuron

phases of action potential

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

into; positive

The following information best describes the _____________ phase of an action potential.

repolarization

Action potentials occur ____________________________.

in the unmyelinated regions of an axon

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

decrease

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

postsynaptic potential

Graded potentials are produced within the _______________________ segment of a neuron

receptive

Graded potentials result from the opening of ________________.

ligand-gated channels