Chapter 12 LearnSmart: Nervous System (Nervous Tissue)

___ are found in mixed nerves.

Sensory and motor axons

"An action potential either happens or it doesn't." This statement could also be called ___.

The all-or-none law

T/F: In most cases, a single EPSP is not sufficient to cause a neuron to reach the threshold potential.

True

T/F: Most voltage-gated ion channels are closed until the electrical potential across a membrane changes.

True

A flow of electrical current called a(n) ___ ___ is generated within the initial segment of a neuron.

action potential

Sensory ___ neurons carry information ___ the central nervous system.

afferent; toward

The refractory period occurs immediately ___ an action potential.

after

Thenerve impulse causes ___ in the number of calcium ions that enter the synaptic knob.

an increase

Local ___ like lidocaine work by inhibiting impulse propagation along nerves.

anesthetics

The ___ division of the nervous system is subdivided into the sympathetic and parasympathetic divisions.

autonomic

The ___ is sometimes called the nerve fiber.

axon

The synaose is located ___ the presynaptic neuron and postsynaptic neuron.

between

The neurons in the retina of the eye are ___.

bipolar

The central nervous system is made of the ___ and the spinal ___.

brain; cord

The presence of ___ ions causes the synaptic vesicles to bind to the membrane, causing neurotransmitters to be released.

calcium

A soma is another name for the ___.

cell body

The main activity of the ___ is propagation of an action potential along the axolemma.

conductive segment

The tissues that receive nerve impulses from motor neurons are called ___.

effectors

Motor neurons are classified as ___ neurons.

efferent

A difference in the number of charged particles between two sides of membrane forms a(n) ___.

electrical gradient

The electrogradient is formed from a combination of the ___ gradient and the ___ gradient.

electrical; chemical

An individual axon is wrapped in a connective tissue covering called the ____.

endoneurium

An entire nerve is surrounded by a connective tissue covering called the ___.

epineurium

When chemically or voltage-gated channels open, there is a change in ion ___ across a membrane.

flow

Neuron cell bodies in the peripheral nervous system are found clustered in ___.

ganglia

A(n) ___ results in swelling, or enlarged portion, along the length of the nerve, which is often large enough to be observed with the naked eye.

ganglion

A ___ ___ is a temporary change in membrane potential which lasts only as long as the stimulus that causes it and can vary in size.

graded potential

The "I" in IPSP stands for ___, meaning that the potential makes the inside of the postsynaptic cell more ___.

inhibitory; negative

If summates PSPs reach threshold, an action potential begins first in ___.

initial segment

If you were moving across a neuron's membrane from the receptive segment toward the transmissive segment, in the ___ is where would you first enounter large numbers of voltage-gated Na+.and K+ channels.

initial segment

The sensory division of the nervous system is responsible for ___.

input

The electrical gradient in a resting neuron is such that the ___ of the cell is negative relative to the ___.

inside; outside

In the myelinated portion of the axon there are ___ so that there is very little movement of ions.

limited ion channels

The myelin sheath is made of a high percentage of ___.

lipids

A more neurotransmitter is released, ___ channels open in the postynaptic neuron.

more

The ___ consists of all axons that transmit a nerve impulse from the CNS to a muscle or gland.

motor nervous system

Most motorneurons are ___.

multipolar

A(n) is much more efficient because saltory conduction occurs and less energy is required to maintain the RMP.

myelinated axon

A ___ is the propagation of an action potential along an axon.

nerve impulse

The thin outer layer of the neurolemmocyte is called the ___.

neurilemma

The small spaces that interrupt the myelin sheath are called

neurofibril nodes

A toxin which intereferes with the activity of neurons is called a ___.

neurotoxin

In neurons, most chemically gated ion channels open in response to the binding of a(n) ___.

neurotransmitter

The motor nervous system is responsible for ___.

output

A fascicle is surrounded by a dense irregular tissue called ___.

perineurium

A nerve is part of the ___ nervous system.

peripheral

Propagation of depolarization only flow away from the cell body towards the synaptic knob because ___.

previous regions in the axon have sodium channels in the inactive state

If an analogy is drawn between an action potential and shooting a gun, then reaching threshold would be analagous to ___.

pulling the trigger

The period following an action potential in which an action potential can be initiated with larger stimulus is known as the ___ ___ period.

relative refractory

The relative difference in charge across the plasma membrane of a resting neuron is known as the ___ ___ ___.

resting membrane potential

The flow of ___ ion is the most common cause of depolarization.

sodium

An action potential cannot be initiated during the absolute refractory period because ___.

sodium channels are inactivated, and thus cannot open

If several EPSPs occur at different synapses, they undergo ______ at the initial segment.

spatial summation

A change in membrane potential insufficient to cause an action potential is known as a ___ ___.

subthreshold value

The process by which postsynaptic potentials are added together at the initial segment is known as ___.

summation

The junction between an axon and another cell is called a ___.

synapse

Dendrites transfer information ___ the cell body.

toward

Vescicles involved in retrograde transport are moving ___ the cell body.

toward

Sensory information from the sensory division is ___ sensed.

unconsciously

Most afferent neurons are classified functionally as ___.

unipolar

Psuedounipolar is another name for a ___ neuron.

unipolar

Which of the following segments of a neuron contain large numbers of voltage-gated potassium channels and voltage-gated channels?

-The initial segment -The conductive segment

What must happen in order for a chemical signal to change the membrane potential of a neuron?

-There must be a change in ion flow across the membrane -There must be a change in a number of open ion channels

Which of the following are true of neurolemmocytes?

-They create the myelin sheath in the PNS -They are also called Schwann cells

Place the events of synaptic transmission from earliest to latest.

1. Action potential reaches synaptic knob 2. Voltage-gated calcium channels open 3. Calcium enters the synaptic knob 4. Calcium triggers exocytosis of vesicles 5. Neurotransmitter diffuses across synaptic cleft 6. Neurotransmitter binds to postsynaptic receptors

Match the letter with the appropriate structure.

A: Brain D: Spinal Cord C: Spinal Nerves B: Ganglia

Match the structure with the corresponding letter.

A: Epineurium B: Perineurium C: Endoneurium D: Axon E: Neurolemmocyte

Match the structure with the appropriate letter.

A: Nucleolus B: Nucleus C: Cell body D: Neurolemmocyte E: Neurofibril node

Identify the parts of an action potential.

A: Threshold B: Depolarization C: Repolarization D: Hyperpolarization E: Resting Membrane Potential

Which of the following pumps can you find in the plasma membrane?

Ca2+ Na+/K+

___ occurs in an unmyelinated axon.

Continuous conduction

___ nerves extend from the brain, while ___ nerves extend from the spinal cord.

Cranial; spinal

T/F: Ion channels use the energy of ATP to maintain concentration gradients across neuron membranes.

False

___ are also called association neurons.

Interneurons

Repolarization is due to the opening of voltage-gated ___ and the subsequent movement of ___ out of the cell.

K+; K+

___ channels allow ungated flow of specific ions from regions of high concentration to regions of low concentration.

Leak

___ nerves contain both sensory and motor neurons.

Mixed

___ is caused by the destruction of oligodendrocytes.

Multiple sclerosis

___ are released from synaptic knobs into the synaptic cleft.

Neurotransmitters

___ is the return of polarity from positive feedback to negative (the RMP).

Repolarization

Synapses occur where axons contact which of the following?

-Muscle cells -Other neurons -Gland cells

Which two divisions are of the sensory nervous system?

-Somatic division -Sensory division

Identify all of the components of the central nervous system.

-Spinal cord -Brain

Synapses are classified as:

-Electrical synapses -Chemical synapses

Match the location with the larger concentration or ions.

-Extracellular: Sodium -Intracellular: Organic ions

Which of the following are functional classes of neurons?

-Interneurons -Sensory Neurons -Motor Neurons

The components of the somatic sensory division are:

-Joints and muscles -Taste -Hearing