Chapter 12 QS Anatomy (Nervous System)

Answer these True/False questions regarding graded potentials.

1. Graded potentials can result from voltage across the plasma membrane.=True 2. Graded potentials can result from mechanical stimulation or temperature changes=True 3. The potential change can vary from small to large depending on the stimulus strength or summation.=True 4. The effects produced by one graded potential can be added onto the effects of another graded potential=True 5. Increased permeability of the membrane to sodium results in depolarization=True 6. A depolarizing graded potential can cause an action potential=True

Match the most common types of neurons with where they can be found in the human body.

Most common type; innervate muscles and glands=Multiploar neurons Most neurons in the PNS=Unipolar neurons Special senses=Bipolar neurons

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

Oligodendrocytes

Myelin sheaths mainly consist of which part of the glial cells that form them?

Plasma membranes

Scorpion agitoxin is a neurotoxin that blocks the activity of voltage-gated potassium channels. In the presence of agitoxin, which will occur during an action potential?

The neuron will remain depolarized and unable to repolarize.

The _______ is a period when a membrane cannot respond to another stimulus (no matter how strong).

absolute refractory period

To enhance the effect acetylcholine has in a particular synapse, a drug may block acetylcholinesterase (AChE) so that

acetylcholine is not destroyed and will remain in the synapse longer.

Label the figure with the items provided.

bipolar neuron, anaxonic neuron, unipolar neuron, multipolar neuron

Acetylcholinesterase

catalyzes hydrolysis of ACh to remove it from the synaptic cleft.

Nitric oxide is a neuromodulator that

causes some blood vessels to dilate.

Label the parts of the typical myelinated neuron.

cell body, neurofibril nodes, myelin sheath, neurolemmocyte neurilemma, axon

Ependymal cells help produce

cerebrospinal fluid

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

efferent

On a graph of an action potential, the small depolarizations that lead to threshold are from

excitatory postsynaptic potentials (EPSPs).

An axon with a large diameter transmits an impulse ____ than an axon with a smaller diameter.

faster

Label the features of a myelinated axon.

myelin sheath, axon, neurolemmocyte nucleus, neurilemma

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

positive

A typical synapse in the CNS consists of a presynaptic neuron and a postsynaptic neuron, separated by a narrow space called the

synaptic cleft.

An excitatory postsynaptic potential (EPSP) causes

the postsynaptic neuron's membrane potential to become more positive.

An inhibitory postsynaptic potential (IPSP)

will make it more difficult for the postsynpatic neuron to reach threshold.

Which part of a neuron contains calcium pumps and channels?

Synaptic bulbs

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

True

After its synthesis in a neuron, acetylcholine is stored in synaptic vesicles within the synaptic knob.

True

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

Vesicles containing neurotransmitter would not merge with the plasma membrane.

Classifying axons into types A, B, and C is based on their

conduction velocity.

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

inhibitory postsynaptic potential.

Neuronal pools are composed of

interneurons.

An EPSP will cause the postsynaptic membrane

to depolarize.

Neurolemmocytes produce myelin in the _____ nervous system.

peripheral

During the transmission of an action potential along a myelinated axon, as one neurofibril node is depolarizing, the previous node is repolarizing.

True

Neurotransmitters are removed from a synapse by degradation and reuptake.

True

The negative value of the resting membrane potential means that

there are more negatively charged particles on the inside of the membrane than on the outside.

Link the definitions to the correct action potential periods.

1. A time when there is a decrease in the sensitivity of the plasma membrane to further stimulation. =(refractory period) 2. The time when there is complete insensitivity of the plasma membrane to another stimulus. =(absolute refractory period) 3. The time when a stronger-than-threshold stimulus is needed to initiate another action potential.= (relative refractory period)

Correctly identify each of these definitions or examples as either depolarization or hyperpolarization of the plasma membrane.

1. Decrease in the membrane potential=depolarization 2. Inside of the cell becomes more positive=depolarization 3. An increase in the extracellular concentration of potassium=hyperpolarization 4. Increase in the membrane potential=hyperpolarization 5. Inside of the cell becomes more negative=hyperpolarization 6. A decrease in the extracellular concentration of potassium=depolarization 7. An increase in the number of sodium leak channels=depolarization

Myelin does more than protect axons, it also permits action potentials to travel more rapidly. Complete these True or False questions to test your understanding of myelinated and unmyelinated neurons.

1. In myelinated axons, the plasma membrane of neurolemmocytes or oligodendrocytes must repeatedly wrap around a segment of an axon to form the myelin sheath=True 2. Neurofibril nodes are gaps found in the plasma membrane of neurolemmocytes and oligodendrocytes=False 3. There are neurolemmocytes or oligodendrocytes in unmyelinated areas of the neuron=True 4. There are neurolemmocytes or oligodendrocytes at a neurofibril node=True 5. In unmyelinated axons, the axon may be surrounded by a series of neurolemmocytes or oligodendrocytes=True

The structural classification of neurons is based on the number of processes that extend from the neuron cell body. Match these definitions to the correct term. 1. Many dendrites and a single axon (Click to select) 2. One dendrite and one axon (Click to select) 3. One process with two branches; one extending to the CNS, one extending to the periphery (Click to select)

1. Many dendrites and a single axon (Multipolar neuron) 2. One dendrite and one axon (Bipolar neuron) 3. One process with two branches; one extending to the CNS, one extending to the periphery (Unipolar neuron)

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

3, 5, 1, 4, 2

The fundamental physiological properties that enable nerve cells to communicate with other cells are

All of these choices are correct

Which glial cell is starlike in shape and helps form the blood-brain barrier?

Astrocytes

Match the subdivision of the nervous system with its components.

Consists of the brain and spinal cord=central nervous system Includes cranial nerves, spinal nerves, and ganglia=peripheral nervous system

A neuromodulator is another name for a neurotransmitter.

False

EPSPs and IPSPs have a long-term effect on a neuron.

False

Ganglia are clusters of neuron cell bodies located within the CNS.

False

Greater current flow is possible with larger resistance and a lower voltage.

False

In neurons, protein pumps allow substances to move passively down their concentration gradients.

False

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

False

One function of the nervous system is to always respond to sensory input.

False

The endoneurium wraps around groups of fasicles to form a nerve.

False

Fast retrograde transport returns used synaptic vesicles and other materials to the soma and informs the soma of conditions at the axon terminals.

True

If extracellular concentrations of potassium are increased dramatically, a neuron may not be able to repolarize during an action potential.

True

Inhibitory postsynaptic potentials (IPSPs) may be caused by the opening of either chemically gated potassium channels or chemically gated chloride channels.

True

Postsynaptic neurons can generate both inhibitory and excitatory postsynaptic potentials simultaneously.

True

Sodium has a higher concentration outside the cell than within.

True

The entry of sodium ions into the postsynaptic neuron causes depolarization.

True

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

afferent

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.

Label the different types of neuronal pools in the figure.

converging circuit, diverging circuit, reverberating circuit, parallel-after-discharge circuit

Upon binding of endocannabinoids to their target, there is a(n)

decrease neurotransmitter release from presynaptic neurons.

A message traveling from one presynaptic neuron to multiple postsynaptic neurons is an example of a ____ circuit.

diverging

A small group of neurons in the brain coordinating the action of many leg, back, and arm muscles during running is an example of a

diverging circuit

An excitatory postsynaptic potential (EPSP)

may result from positively charged ions entering the postsynaptic neuron.

Which glial cell acts as a phagocyte?

microglial cell

Correctly label the following anatomical features of the neuroglia.

microglial cell, neuron, oligodendrocyte, astrocyte, perivascular foot, capillary, ependymal cell

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

Nerve growth factors that stimulate outgrowth of severed axons are secreted by

neurolemmocytes.

Identify the components of a typical neuron.

nucleolus dendrite axon hillock telodendria synaptic knobs

Correctly label the structures and areas associated with a neuron at rest.

receptive segment, axon hillock, conductive segment, synaptic knob, initial segment, axon, transmissive segment

What type of neural circuit results in a repeating, cyclical response?

reverberating

The ___________ nervous system transmits information from receptors to the CNS, while the ___________ nervous system transmits information from the CNS to the rest of the body.

sensory; motor

As a result of a neurotransmitter opening up chemically gated sodium channels on the postsynaptic membrane,

sodium ions enter the cell.

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

the all-or-none principle.

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

the membrane potential would be about -90 millivolts.