Learn Smart: Chapter 12 (Nervous System: Nervous Tissue)

When a neurotransmitter binds a protein channel, it opens and lets sodium diffuse down its concentration gradient. This is an example of a:

- Chemically gated sodium channel

Local Potentials

- Decremental - Reversible - Cause Summation - IPSPs - EPSPs

It is necessary that the neurotransmitter molecule is eliminated after each stimulation event. Its removal can occur by (1) _____, in which the neurotransmitter is chemically _____ in the _____ and (2) _____, in which the neurotransmitter is reabsorbed by a neurotransmitter _____ in the membrane of the _____ neuron. These neurotransmitters are "recycled" once packaged into another _____for reuse.

- Degradation - Inactivated - Synaptic cleft - Reuptake - Transport protein - Presynaptic - Synaptic vesicle

Neurons that carry signals from the CNS to skeletal muscle for contraction would be classified as _____________ neurons.

- Efferent

The vagus nerve contains afferent and efferent neurons, therefore it is an example of a(n) __________ nerve

- Mixed

Astrocytes

- Most abundant CNS glial cell - Involved with neurogenesis, scar formation, and BBB maintenance

Many dendrites and a single axon:

- Multipolar neuron

Absolute Refractive Period:

- Occurs about ms after and action potential - No amount of stimulus will initiate a second action potential - Voltage-gated sodium channels are opened then closed in the inactivated state

Slow Axonal Transport

- Occurs at to .1 to 3 mm/day - Movement occurs with flow of the axoplasm - Substances move only from cell body toward the synaptic knob

Indicate the glial cells that form a myelin sheath around axons. Check all that apply.

- Oligodendrocyte - Neurolemmocyte

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

- Oligodendrocytes

Includes cranial nerves, spinal nerves, and ganglia:

- Peripheral nervous system (PNS)

When sodium enters the neuron via chemically gated sodium channels, the membrane will depolarize. Therefore, the membrane potential will become more

- Positive

Check all that are a function of the nervous system.

- Processing and evaluating information - Collecting information - Responding to information

The _____ segment includes both dendrites and the cell body, which are the regions of the neuron that receive stimuli to excite the neuron. Channels in this region are _____ ; no significant numbers of _____ channels are present. • The _____ segment is composed of the axon hillock. This segment contains voltage-gated channels. • The _____ segment is equivalent to the length of the axon. It contains voltage-gated channels. • The _____ segment includes the synaptic knob and contains voltage-gated channels and _____.

- Receptive - Chemically gated - Voltage-gated - Initial - Conductive - Transmissive - Pumps

Action Potentials

- Require threshold - Important for transmission over long distances

Which part of a neuron contains calcium pumps and channels?

- Synaptic bulbs

Neurotransmitters are removed from a synapse by degradation and reuptake.

- True

3. One process with two branches; one extending to the CNS, one extending to the periphery:

- Unipolar neuron

Ependymal Cells

Function in the production and circulation of CSF

This results in membrane _____

- depolarization

Consists of the brain and spinal cord:

- Central nervous system (CNS)

Nerve impulses relaying pain would most likely use saltatory conduction

- False

Nerve impulses relaying pain would most likely use saltatory conduction:

- False

If extracellular calcium was absent, which would likely be true?

- Vesicles containing neurotransmitter would not merge with the plasma membrane.

One dendrite and one axon:

- Bipolar neuron

Neurons are unique in that they do not require glucose or oxygen to function.

- False

Fast axonal transport occurs at approximately _____ millimeters per day. The mechanism involves movement along _____ . The power for this movement comes from specialized _____ that split ATP to supply the energy needed. Substances can be moved in _____ . Slow axonal transport occurs at approximately _____ millimeters per day. This type of movement results from the _____ , and is also called _____. The substances are moved in an _____ direction only.

- 400 - micotubules - motor proteins - either direction - 0.1 to 3 - flow of the axoplasm - axoplasmic flow - anterograde

Check all that apply to chemical synapses.

- Chemical synapses are the most numerous type of synapse in the human body. - Chemical synapses are unidirectional (one way).

If neurotransmitter from Neuron A causes Neuron B to hyperpolarize, this is an example of an

- Inhibitory postsynaptic potential.

Fast Axonal Transport

- Involves movement along microtubules - Involves proteins kinesin or dyein - Anterograde or retrograde movement - Occurs at 400 mm/day

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

- Length

The vagus nerve contains afferent and efferent neurons, therefore it is an example of a(n) __________ nerve.

- Mixed

The most common type of neuron contains many dendrites and a single axon. Structurally, this is classified as a(n) ______________ neuron.

- Multipolar

If all the sodium leakage channels were removed from the cell membrane of a neuron,

- The membrane potential would be about -90 millivolts.

Select all that are true of oligodendrocytes:

- They are glial cells found in the CNS - They can form myelin around several axons simultaneously - They help form a myelin sheath around CNS axons

A regenerating axon in the PNS is guided by the regeneration tube, and grows at a rate of about 5 mm per day

- True

Axoplasmic flow is an example of slow axonal transport.

- True

On a typical neuron, the axon is usually longer in length than the dendrites.

- True

Sodium has a higher concentration outside the cell than within.

- True

The enzyme acetylcholinesterase, located in the synaptic cleft and on the postsynaptic membrane, breaks ACh down into acetate and choline, thereby stopping the stimulation of a postsynaptic cell.

- True

Between each presynaptic and postsynaptic neuron is a _____ that is the fluid-filled space between them. Each presynaptic neuron releases _____ that binds with receptors in the _____ segment of a postsynaptic neuron. The _____ channels of the receptive segment open when these molecules bind. Specific ions then cross the membrane, initiating a _____ potential in the postsynaptic neuron. This local potential is a small voltage change in the _____ potential. Graded potentials that occur in postsynaptic neurons are SPECIFICALLY called _____ potentials

- synaptic cleft - neurotransmitter - receptive - gated - ? - ? - postsynaptic

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

- trigger

Relative Refractory Period:

- Neuron is hyperpolarized - Ensures that the action potential moves down the axon in only one direction - Occurs when voltage-gated sodium channels have returned to resting state

Spatial Summation

- Various locations of receptive segment are exposed to neurotransmitter - Multiple presynaptic neurons releasing neurotransmitter - Can generate an EPSP, IPSP, or both

A synapse is the specific location where _____ is functionally connected to either another neuron or _____ There are two types of synapses in the human body: chemical synapses and electrical synapses. Most synapses within the nervous system are _____ synapses.

- a neuron - an effector. - chemical

The voltage-gated Na⁺ channels _____ when the cell reaches +30mV.

- close

The nervous system serves as the body's primary _____ and control system. It provides a rapid means of _____ and regulating body functions through electrical activity transmitted along specialized nervous system cells called _____ to accomplish the following: • Collect information. Specialized nervous system structures called _____ monitor changes in both the internal and external environment called _____. • Process and evaluate information. After processing _____ input, the brain and spinal cord determine what response, if any, is required. • Initiate response to information. The brain and spinal cord initiate a response as _____ output via nerves to _____ . These structures include all three types of muscle tissue and glands.

- communication - integrating - neurons - ? - stimuli - sensory - motor - effectors

Oligodendrocytes

Form the myelin sheath in the CNS

Neurolemmocytes

Form the myelin sheath in the PNS

Microglia

Macrophages of the CNS

The voltage-gated Na⁺ channels _____ when the cell membrane reaches threshold level as a result of a stimulus.

- open

Satellite Cells

PNS cells that surround and insulate the somas

When K⁺ diffuses out of the cell, the cell becomes _____ depolarized.

- less

When Na⁺ diffuses into the cell, the cell become _____ more depolarized.

- more

K⁺ diffusing out of the cell has a _____ feedback effect on the initial polarization

- negative

Na+ diffusing into the cell causes more Na+ gates to open, which is a _____ feedback loop

- positive

The depolarization causes a _____ that excites the entire membrane

- repetition

This continues until the traveling _____ reaches the end of the axon

- signal

The _____ classification of nerves is based upon the _____ from which the nerve extends: Cranial nerves extend from the _____ and spinal nerves extend from the _____. The _____ classification of nerves is based upon whether a nerve contains sensory neurons or motor neurons. Sensory nerves contain only sensory neurons that relay information _____ , and motor nerves contain primarily motor neurons that relay information _____ . In contrast, _____ nerves contain both sensory and motor neurons

- structural - CNS component - brain - spinal cord - functional - to the CNS - from the CNS - mixed

Pain receptors in the skin send signals to the CNS for processing. These pain receptors are an example of ____________ neurons.

- Afferent

Rank in order the events that occur when an action potential reaches the transmissive segment of an axon.

1) Action potential reaches synaptic knob. 2) Voltage-gated calcium channels open. 3) Vesicles containing neurotransmitter merge with plasma membrane. 4) Neurotransmitter diffuses across synaptic cleft.

Place the items in the correct order for an IPSP from beginning to end.

1) An inhibitory neurotransmitter binds to chemically gated K+ channels 2) K+ channels open 3) K+ flows out of the neuron 4) The inside of the neuron becomes more negative 5) The IPSP propagates toward the axon hillock

On a particular patch of axolemma, the electrical events that occur as an action potential travels by can be ordered as

1) Depolarization 2) Repolarization 3) Hyperpolarization

Temporal Summation

- A single presynaptic neuron releases neurotransmitter - The same location of neuron is exposed to neurotransmitter in a very short period of time