EXAM 5 246 A&P

First, link the definition of the action potential refractory periods, and then drag the name to the proper location on the image.

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

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

Select all that are classes of neurotransmitters.

Acetylcholine Amino acids Monoamines Neuropeptides

Place a single word into each sentence to make it correct. Some terms may be used more than once, some not at all.

Action potentials arriving at the presynaptic terminal cause voltage-gated calcium channels to open. Calcium ions diffuse into the cell and cause synaptic vesicles to release neurotransmitters. Neurotransmitters diffuse from the presynaptic terminal across the synaptic cleft. Neurotransmitters combine with their receptor sites and cause ligand-gated ion channels to open. The diffusion of ions into the cell or out of the cell causes a change in membrane potential.

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EPSP and IPSP graded potentials are local currents of ions that move along the plasma membrane toward the initial segment area of the axon hillock. Graded postsynaptic potentials are added together in the initial segment; this process is called summation. The initial segment, by adding postsynaptic potentials, determines if a(n) threshold membrane potential is reached.This potential is -55 mV. This is a change of +15 mV from the RMP. When this threshold is reached, it initiates the opening of voltage-gated channels and the generation of a(n) action potential that will travel along the axon.

Select all that are true regarding the resting membrane potential.

It has a negative value. It is measured in millivolts. It can range from −40 to −90 millivolts.

Select all of the following that would increase the magnitude of a postsynaptic potential.

More neurotransmitter released from the presynaptic neuron. More chemically gated channels open in the postsynaptic neuron.

Check all that apply to myelinated axons.

Myelinated axons use less energy than unmyelinated axons. In myelinated axons, the nerve impulses "jump" from node to node, and do not have to travel the entire length of the axon membrane. Myelinated axons have faster nerve impulse conduction than unmyelinated axons.

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Neurons are classified functionally according to the direction the action potential travels relative to the CNS. Afferent neurons are the neurons of the sensory nervous system. They are responsible for conducting sensory input from both somatic sensory and visceral sensory receptors. Most sensory neurons are unipolar.Efferent neurons are the neurons of the motor nervous system, conducting motor output from the CNS to the effectors. All motor neurons are multipolar.Interneurons (or association neurons) lie entirely within the CNS. They receive stimulation from many other neurons and carry out the integrative function of the nervous system.The most numerous types of neurons are interneurons.

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PNS axons are vulnerable to cuts, crushing injuries, and other types of trauma. However, a damaged axon can regenerate if the cell body remains intact and a critical amount of neurilemma remains. The success of PNS axon regeneration depends upon two primary factors: (1) the amount of damage, and (2) the distance between the site of the damaged axon and the effector organ. The possibility of repair is decreased with an increase in either of these two factors.Neurolemmocytes play an active role in regeneration.

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Pumps move substances against a concentration gradient, a process that requires energy. Channels instead provide the means to move a substance with a concentration gradient. Neurons contain the following major types of channels:• Channels that are always open, allowing continuous diffusion of a specific ion from a region of high concentration to a region of low concentration are leak channels.• Channels that are normally closed that open in response to the binding of a neurotransmitter are chemically gated channels. When open, they allow a specific ion to diffuse across the plasma membrane.• Channels that are normally closed, but open in response to changes in electrical charge across the plasma membrane are voltage gated channels. When open, they allow a specific ion to diffuse across the membrane.

Fill in the blanks with the terms provided.

The nervous system serves as the body's primary communication and control system. It provides a rapid means of integrating and regulating body functions through electrical activity transmitted along specialized nervous system cells called neurons to accomplish the following:• Collect information. Specialized nervous system structures called receptors monitor changes in both the internal and external environment called stimuli.• Process and evaluate information. After processing sensory 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 motor output via nerves to effectors. These structures include all three types of muscle tissue and glands.

Fill in the blanks with the terms provided. Not all terms will be used.

The peripheral nervous system is further subdivided into an afferent (sensory) division and an efferent (motor) division. The afferent or sensory division transmits impulses from peripheral organs to the CNS. The efferent or motor division transmits impulses from the CNS out to the peripheral organs. The motor division is separated further into a somatic motor division and a(n) autonomic motor division. Autonomic refers to the controls we are not aware of, like smooth muscle, cardiac muscles, and glands.

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The relative difference in charge across a plasma membrane is the resting membrane potential in an inactive excitable cell. A voltmeter is used to measure the voltage difference across the plasma membrane. This is done by placing one microelectrode into the neuron and the other microelectrode outside the neuron into the interstitial fluid. The RMP has a value, which is typically -70 millivolts. More positive ions reside outside a neuron than inside a neuron when it is at rest.

Fifty presynaptic neurons all briefly release a single burst of excitatory neurotransmitter, generating excitatory postsynaptic potentials (EPSPs) in a postsynaptic neuron. Using this example, select all that apply.

These EPSPs will be summed at the axon hillock.

Select all the characteristics of graded potentials.

They are the result of chemically gated ion channels opening. The current generated is localized. The current generated decreases with distance.

Select the correct word from the list to complete each sentence.

When Na⁺ diffuses into the cell, the cell becomes more depolarized. Na+ diffusing into the cell causes more Na+ gates to open, which is a positive feedback loop. When K⁺ diffuses out of the cell, the cell becomes less depolarized. K⁺ diffusing out of the cell has a negative feedback effect on the initial polarization. The voltage-gated Na⁺ channels open when the cell membrane reaches threshold level as a result of a stimulus. The voltage-gated Na⁺ channels close when the cell reaches +30mV.

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

afferent

Acetylcholinesterase

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

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.

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

efferent

When chloride enters the neuron via chemically gated chloride channels, the membrane potential will become more negative than the resting membrane potential. This is called _____________.

hyperpolarization

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

inhibitory postsynaptic potential.

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

mixed

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

positive

Another term for the __________ system is the afferent nervous system.

sensory

Select all that are common features of most neurons.

soma dendrite axon

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

synaptic cleft.

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

the All-or-None principle.

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

the ability to respond to environmental changes. the ability to produce electrical signals that are quickly conducted to other cells at distant locations. the ability to secrete a chemical that will stimulate the next cell when an electrical signal reaches the end of an axon. All of these choices are correct.

The negative value of the resting membrane potential means

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

Complete each statement by using the appropriate word or phrase from the list. Not all terms will be used.

Resting membrane potential is created as a result of a greater net flow of positive charges from the ICF to the ECF. Though potassium and sodium both leak through the membrane at rest, there is a greater diffusional flow of potassium at rest. The diffusional movement of sodium and potassium across the membrane is driven at all times by the electrochemical gradient. The electrical and chemical gradients for sodium are both high during resting membrane potential which results in a very high electrochemical gradient toward the inside of the cell. In order to maintain the electrochemical gradients for sodium and potassium, ATPase pumps move these ions against their respective gradients.

Select all the appropriate classifications for a nerve that sends sensory information from the eye to the brain.

Sensory cranial