chapter 7 physiology

Each action potential "injects" positive charges (sodium ions) into the axon A. true B. false

A

The ______ is a longer process that conducts action potentials away from the cell body. A. dendrites B. axon C. axon hillock D. cell body

B

The antagonist for muscarinic receptors is ______ and the antagonist for nicotinic receptors is _____. A. Curare, atropine B. atropine, curare C. muscarine D. nicotine

B

Neurons maintain an average rmp of ___ mV. A. 70 B. -70 C. 55 D. -55

B

In regards to chemically regulated channels, binding of a neurotransmitter to a receptor can open an ion channel in one of two ways:

-Ligand-gated channels -G-protein coupled channels

According to the all or none law, a subthreshold stimulus will not elicit an action potential because A. it will not open the voltage-gated channels. B. the action potential isnt strong enough to fire itself C. there aren't sufficient enough Na+ and K+

A

Do PNS axons or CNS axons have the ability to regenerate? A. PNS axons B. CNS axons

A

For ion channels that are ____________, the receptor protein is also an ion channel but in ___________ the neurotransmitter receptor is separate from the protein that serves as the ion channel. A. ligand gated, g protein coupled channels B. g protein coupled channels, ligand gated

A

In G protein coupled channels, binding of ____ acetylcholine results in the dissociation of the alpha subunit. A. one B. two C. three D. four

A

In g protein coupled channels, binding of acetylcholine opens K+ channels in some tissues (______) or closes K+ channels in others (____). A. IPSP, EPSP B. EPSP, IPSP

A

K+ has two types of channels: • One is not gated (always open); sometimes called ____________. • Another is ____ ____; open when a particular membrane potential is reached; closed at resting potential. A. K+ leakage channels, voltage-gated B. Na+ leakage channels, voltage-gated C. Na+ leakage channels, ligand-gated D. K+ leakage channels, ligand-gated

A

Na+ channels close and K+ channels open at _____ mV, which results in a _______ of membrane potential; this is a _____ feedback loop. A. +30 mV, repolarization, negative B. -30 mV, depolarization, negative C. -55 mV, polarization, positive D. +55 m V, repolarization, positive

A

The ____ ____ _____ is when K+ channels are still open and only a very strong stimulus can overcome this to cause an AP. A. relative refractory period B. absolute refractory period

A

The absolute refractory period occurs _____ the action potential and is due to inactivated ____ channels (not just closed). A. during, Na+ B. before, K+ C. after, Na+ D. after, K+

A

The opening of Na+ or Ca2+ channels results in a graded ________ called an excitatory postsynaptic potential (EPSP). A. depolarization B. polarization C. hyperpolarization D. repolarization

A

What are the two types of glutamate receptors involved in memory storage? a) NMDA and AMPA receptors b) GABA and AMPA receptors c) NMDA and kainate receptors d) GABA and kainate receptors

A

What disease results from degeneration of GABA-secreting neurons in the cerebellum? A. Huntington's disease B. Schizophrenia C. Parkinsons D. Alzheimers

A

When the membrane potential inside the cell increases (becomes more positive), this is called ____________. When the membrane potential inside the cell decreases (becomes more negative), this is called ___________. A. depolarization; hyperpolarization B. Hyperpolarization; depolarization C. polarization; depolarization D. repolarization; hyperolarization

A

Where is LTP found? A. hippocampus of the brain where memories are stored B. Basal ganglia C. neurons D. axons

A

Which ACh receptor is found in the CNS and plasma membrane of smooth and cardiac muscles and glands innervated by autonomic motor neurons? A. Muscarinic ACh receptors B. Nicotinic ACh receptors

A

Which channel is found primarily in the axons and open in response to depolarization and are required for action potentials? A. Voltage-gated channels B. ligand-gated channels (chemically regulated)

A

Which dopamine system is primarily involved in the regulation of motor control? a) Nigrostriatal dopamine system b) Mesolimbic dopamine system c) Both systems are involved in motor control d) None of the above

A

Which of the following is a function of GABA? a) Motor control b) Memory formation c) Anxiety regulation d) Sleep regulation

A

Which of these is not a characteristic of synaptic potentials? a. They are all or none in amplitude. b. They decrease in amplitude with distance. c. They are produced in dendrites and cell bodies. d. They are graded in amplitude. e. They are produced by chemically regulated gates

A

__________ line the ventricles and secrete cerebrospinal fluid. A. ependymal cells B.astrocytes C. microglia D. oligodendrocytes

A

Dysfunction of which dopamine system has been implicated in schizophrenia? a) Nigrostriatal dopamine system b) Mesolimbic dopamine system c) Both systems are implicated in these disorders d) Neither system is implicated in these disorders

B

What disease is associated with loss of cholinergic neurons that synapse on the areas of the brain responsible for memory?

Alzheimers disease

Action potentials can only increase in frequency to a certain point. There is a refractory period after an action potential when the neuron cannot become excited again, called the: __________. This period occurs during the action potential and Na+ channels are inactive (not just closed). A. relative refractory period B. absolute refractory period

B

An action potential occurs when the membrane depolarises to a certain threshold, if this threshold is not reached the action potential will not be triggered. This is referred to as the: A. refractory period B. all or none law C. change in membrane potential

B

Depolarization of the cell is ________; Hyperpolarization is ________. A. inhibitory; excitatory B. excitatory; inhibitory

B

The opening of Na+ or Ca2+ channels results in a graded depolarization called an __________. A. action potential B. excitatory postsynaptic potential (EPSP) C. graded potential D. inhibitory postsynaptic potential (IPSP)

B

There are ____ types of glia in the PNS and ____ types of glia in the CNS. A. four; two B. two; four C. four; six D. six; four

B

What is the result of Long Term Depression? a) Insertion of AMPA receptors b) Removal of AMPA receptors c) Insertion of NMDA receptors d) Removal of NMDA receptors

B

What type of channel does Na+ have? A. Leakage B. Voltage-gated C. Both D. None

B

When Voltage-gated Na+ channels open and Na+ enters, this is ____________; and a ______ feedback loop. Membrane potential reaches ______ mV. A. polarization; positive; +30 mV B. depolarization, positive; +30 mV C. polarization; negative; -30 mV D. depolarization, negative; -30 mV

B

When do K+ voltage-gated channels open? A. Always B. When a particular membrane potential is reached C. At rest D. None of the above

B

When the membrane potential inside the cell decreases (becomes more negative), this is called _________. (occurs when positive ions leave the cell (usually ____) or negative ions (___) enter the cell.); inhibitory A. depolarization, K+, Cl- B. hyperpolarization, K+, Cl- C. hyperpolarization, Na+, Cl- D. depolarization, Na+, Cl-

B

When the membrane potential inside the cell increases (becomes more positive), this is called ___________. (occurs when positive ions enter the cell, usually ____.) A. depolarization, K+ B. depolarization, Na+ C. hyperpolarization, K+ D. hyperpolarization, Na+

B

Which ACh receptor is found on the motor end plate of skeletal muscle cells, in autonomic ganglia, and in some parts of the CNS? A. Muscarinic ACh receptors B. Nicotinic ACh receptors

B

Which channel is found in the postsynaptic membrane and open in response to the binding of postsynaptic receptor proteins to their neurotransmitter ligands and is associated with graded potentials? A. Voltage-gated channels B. ligand-gated channels (chemically regulated)

B

Which dopamine system is primarily involved in the regulation of emotional reward? a) Nigrostriatal dopamine system b) Mesolimbic dopamine system c) Both systems are involved in motor control d) None of the above

B

Which of the following best describes the main function of the mesolimbic dopamine system? A) Motor control B) Emotional reward C) Temperature regulation D) Sensory perception

B

Which of the following is false about Nicotinic ACh receptors? A. Can be stimulated by nicotine B. Found in CNS and plasma membrane of smooth and cardiac muscles and glands innervated by autonomic motor neurons. C. Found on the motor end plate of skeletal muscle cells, in autonomic ganglia, and in some parts of the CNS.

B

Which of the following is the main function of the nigrostriatal dopamine system? A) Emotional reward B) Motor control C) Learning and memory D) Pain modulation

B

Which system involves neurons that originate in the midbrain and send dopaminergic neurons to regions of the forebrain and is involved in emotional reward systems and associated with addictions such as nicotine, alcohol, and other drugs? a) Nigrostriatal dopamine system b) Mesolimbic dopamine system c) Substantia nigra d) Ventral tegmental area (VTA)

B

_________ regulate the external environment of the neurons in the CNS. A. ependymal cells B.astrocytes C. microglia D. oligodendrocytes

B

the amplitudes of all action potentials are about equal size (____ mV) and duration ( ____msec). A. -70; 6 B. +30; 3 C. 70; 3 D. -30; 3

B

All cells in the body maintain a potential difference (voltage) across the membrane called the _____, in which the inside of the cell is negatively charged in comparison to the outside of the cell. A)action potential B)threshold potential C)resting potential D)graded potential

C

At threshold membrane potential (−55mV), voltage-gated Na+ channels _____, and Na+ rushes ____. As the cell depolarizes, more Na+ channels are open, and the cell becomes more and more permeable to Na+. A. close, out B. opens, out C. open, in D. closes, in

C

Conduction of nerve impulses •When an action potential occurs at a given point on a neuron membrane, voltage- gated ____ channels open as a wave down the length of the axon. •The action potential at one location serves as the ________ stimulus for the next region of the axon. •The impulse only travels in one direction due to the refractory period in the preceding axon segment. A. Na+, hyperpolization B. K+, polarization C. Na+, depolarization D. K+, repolarization

C

How are patients with Parkinson's disease typically treated? a) Antidepressants b) Anxiolytics c) L-dopa and MAOIs (monoamine oxidase inhibitors) to try to increase dopaminergic transmission d) Beta blockers

C

Repolarization of an axon during an action potential is produced by A. inward diffusion of Na+. B. active extrusion of K+. C. outward diffusion of K+. D. inward active transport of Na+.

C

The ion that must flow into the presynaptic neuron ending through voltage-regulated channels to activate the release of neurotransmitter chemicals from synaptic vesicles is A)sodium B)potassium C)calcium D)iron

C

The opening of K+ or Cl− channels results in a graded _______ called an inhibitory postsynaptic potential (IPSP). A. depolarization B. polarization C. hyperpolarization D. repolarization

C

What is associated with the insertion of AMPA glutamate receptors in the postsynaptic neuron? a) Long-term depression (LTD) b) Short-term potentiation (STP) c) Long-term potentiation (LTP) d) Short-term depression (STD)

C

What is the cause of Parkinson's disease? a) Degeneration of the dopaminergic neurons in the hippocampus b) Degeneration of the dopaminergic neurons in the amygdala c) Degeneration of the dopaminergic neurons in the substantia nigra d) Degeneration of the dopaminergic neurons in the VTA

C

What is the primary function of the dopaminergic neurons sent from the substantia nigra to the corpus striatum? a) Emotional regulation b) Memory formation c) control and initiation of Voluntary movements d) Sensory processing

C

What is the role of calcium ion concentration in LTP and LTD? A) It has no role in either LTP or LTD B) A rapid rise leads to LTD, while a prolonged rise leads to LTP C) A rapid rise leads to LTP, while a smaller, prolonged rise leads to LTD D) A rise in calcium ion concentration is only necessary for LTP, not LTD

C

What is the threshold membrane potential? A. +30 mV B. -30 mV C. -55 mV D. +55 m V

C

When an axon in the PNS is cut, the _____ part degenerates, and a regeneration tube is formed by ________ _______. A. proximal; astrocyte cells B. distal; ependymal cells C. distal; Schwann cells D. proximal; Schwann cells

C

When ligand-gated ion channels are opened, they produce a graded change in the membrane potential known as a _____ _____. A. action potential B. excitatory postsynaptic potential (EPSP) C. graded potential D. inhibitory postsynaptic potential (IPSP)

C

When the membrane potential inside the cell decreases (becomes more negative), this is called ___________. A. depolarization B. polarization C. hyperpolarization D. repolarization

C

Which of the following about EPSPs in ligand gated channels is true? A. EPSPs occur in the dendrites and cell bodies. B. EPSPs from the binding of several ACh molecules can summate to produce greater depolarization, therefore they are graded potentials. This may reach the threshold for voltage-gated channels in the axon hillock, leading to an action potential. C. all of the above

C

Which of the following about ligand-gated channels is false? A. Nicotinic ACh receptors are ligand-gated channels with two receptor sites for two AChs. B. The binding of 2 acetylcholine molecules opens a channel that allows both Na+ and K+ passage. Na+ flows in, and K+ flows out. C. The neurotransmitter receptor is separate from the protein that serves as the ion channel. D. Due to electrochemical gradient, more Na+ flows in than K+ out. The inward flow of Na+ depolarizes the cell, creating an EPSP.

C

Which of the following addictions is NOT associated with the mesolimbic dopamine system? a) Nicotine b) Alcohol c) Caffeine d) all of the above

C

Which of the following is false about Muscarinic ACh receptors? A. Can be stimulated by muscarine (from poisonous mushrooms). B. Found in CNS and plasma membrane of smooth and cardiac muscles and glands innervated by autonomic motor neurons. C. Found on the motor end plate of skeletal muscle cells, in autonomic ganglia, and in some parts of the CNS.

C

Which of the following is false about conduction in an unmyelinated neuron? A. action potentials are produced down the entire length of the axon at every patch of membrane B. conduction rate is slow because so many action potentials are generated, each one, an individual event. C. Conduction rate is fast because Nodes of Ranvier allow Na+ and K+ to cross the membrane every 1−2 mm. D. all of the above is true

C

Which of the following is not one of the reasons that CNS axons have very limited ability to regenerate? A. Death receptors form that promote apoptosis of oligodendrocytes. B. Inhibitory proteins in the myelin sheath prevent regeneration. C. Growth factors are not released that stimulate growth of axon sprouts within the tube. D. Glial scars from astrocytes form that also prevent regeneration.

C

Which of the following statement about the conduction in a myelinated neuron is false? A. The myelin provides insulation, preventing loss of ions through the membrane and thus improving the speed of the cable properties. B. Nodes of Ranvier allow Na+ and K+ to cross the membrane every 1−2 mm. C. The conduction rate is slow because so many action potentials are generated, each one, an individual event. D. Na+ ion channels are concentrated at the nodes, and APs occur only at the nodes, "leaping" from node to node which is called saltatory conduction.

C

Which of these is not a characteristic of action potentials? a. They are produced by voltage-regulated gates. b. They are conducted without decrement. c. Na+ and K+ gates open at the same time. d. The membrane potential reverses polarity during depolarization

C

Which of these statements about ACh receptors is false? a. Skeletal muscles contain nicotinic ACh receptors. b. The heart contains muscarinic ACh receptors. c. G-proteins are needed to open ion channels for nicotinic receptors. d. Stimulation of nicotinic receptors results in the production of EPSPs

C

___________ migrate through the CNS and phagocytose foreign and degenerated material; part of immune system A. ependymal cells B.astrocytes C. microglia D. oligodendrocytes

C

A return to resting potential is called _____________. A. depolarization B. polarization C. hyperpolarization D. repolarization

D

As the strength of a depolarizing stimulus to an axon is increased, a .the amplitude of action potentials increases. b. the duration of action potential increases. c. the speed with which action potentials are conducted increases. d. the frequency with which action potentials are produced increases

D

At rest, a neuron is considered _______ when the inside is more negative than the outside; When the membrane potential inside the cell increases (becomes more positive), this is called ____________. A. hyperpolarized; depolarization B. depolarized; polarization C. polarized; hyperpolarization D. polarized; depolarization

D

Myelin sheaths around axons located within the CNS are formed by A)Schwann cells B)microglia C)astrocytes D)oligodendrocytes

D

Put the following in order regarding the release of a neurotransmitter. 1. When the action potential reaches the end of the axon, voltage-gated Ca2+ channels open. 2. Neurotransmitter is enclosed in synaptic vesicles in the axon terminal. 3. Ca2+ stimulates the fusing of synaptic vesicles to the plasma membrane resulting in exocytosis of neurotransmitter. A. 1, 2, 3 B. 3, 2, 1 C. 2, 3, 1 D. 2, 1, 3

D

The conduction of action potentials in a myelinated nerve fiber is A. saltatory. B. without decrement. C. faster than in an unmyelinated fiber. D. all of these.

D

The opening of K+ or Cl− channels results in a graded hyperpolarization called an ____________. A. action potential B. excitatory postsynaptic potential (EPSP) C. graded potential D. inhibitory postsynaptic potential (IPSP)

D

What are the two types of glia in the PNS? A. Schwann cells form myelin sheaths around peripheral axons. B. Satellite cells support neuron cell bodies within the ganglia of the PNS. C. Astrocytes D. Both A and B

D

What is the major excitatory neurotransmitter in the brain? a) GABA b) Dopamine c) Serotonin d) Glutamate (glutamic acid)

D

What is the most common neurotransmitter in the brain, is used by 1/3 of the brains neurons, and is inhibitory? a) Glutamate b) Dopamine c) Serotonin d) GABA

D

Which of the following about EPSP's and IPSP's is false? A. EPSPs move the membrane potential closer to threshold; may require EPSPs from several neurons to actually produce an action potential. B. IPSPs move the membrane potential farther from threshold. C. The summation of EPSPs and IPSPs at the initial segment of the axon (next to the axon hillock) determines whether an action potential occurs. D. The opening of Na+ or Ca2+ channels results in a graded depolarization called an inhibitory postsynaptic potential (IPSP)

D

Which of the following is false in G-coupled protein channels? A. The neurotransmitter receptor is separate from the protein that serves as the ion channel. B. Binding at the receptor opens ion channels indirectly by using a G-protein. C. Muscarinic ACh receptors interact with ion channels in this way and so do dopamine and norepinephrine receptors. D. Binding of 2 acetylcholine molecules opens a channel that allows both Na+ and K+ passage.

D

Which of the following is not a type of glia cell in the CNS? A. ependymal cell B. oligodendrocyte C. astrocyte D. Schwann Cell E. microglia

D

Which type of receptors serve as ion channels and are named according to the molecules they bind? a) GABA receptors b) Dopamine receptors c) Serotonin receptors d) Glutamate receptors

D

________ are cells that support neurons and do not conduct impulses. A. dendrite B. axon C. Neurilemma D. glia

D

____________ form myelin sheaths around the axons of CNS neurons. A. ependymal cells B.astrocytes C. microglia D. oligodendrocytes

D

Describe in detail the events of an action potential. Include the important channels, ions, changes in membrane potential, and feedback loops.

Depolarization that leads to threshold (-55mV) Voltage-gated Na+ channels open and Na+ enters = depolarization; positive feedback loop Voltage-gated K+ channels open later and K+ exits = repolarization; negative feedback loop Na+/K+ pump resets ion concentrations

saltatory conduction

Na+ ion channels are concentrated at the nodes of ranvier, and APs occur only at the nodes, "leaping" from node to node. (conduction in a myelinated neuron)

Two types of acetylcholine receptors:

Nicotinic ACh receptors and Muscarinic ACh receptors

Compare and contrast the regeneration of a cut axon in the peripheral and central nervous systems. Include inhibitory/stimulatory components in your answer.

PNS can regenerate because Schwann cells form a regeneration tube and secrete growth factors CNS cannot regenerate because when the axon is cut, oligodendrocytes die and release inhibitory molecules; also glia form a physical barrier to regeneration

conducted without decrement

The amplitude of each action potential all the way to the end of the axon is the same

In regards to ligand gated channels, is the receptor protein also an ion channel? Yes or no

Yes

Acetylcholine (Ach)

a neurotransmitter that directly opens ion channels when it binds to its receptor. In some cases, it is excitatory, and in other cases it is inhibitory, depending on the organ involved.

Once threshold has been reached, an action potential will happen, and a maximum potential change is produced, therefore the amplitude of action potentials is _______-___-_____

all-or-none

G proteins have three subunits:

alpha, beta, gamma

Agonists

are drugs that can bind to and activate a receptor. Examples: -Nicotine for nicotinic ACh receptors. -Muscarine for muscarinic ACh receptors.

Antagonists -Atropine is an antagonist for muscarinic receptors. -Curare is an antagonist for nicotinic receptors.

are drugs that reduce the activity of a receptor. Examples: -Atropine is an antagonist for muscarinic receptors. -Curare is an antagonist for nicotinic receptors.

true or false: Synaptic plasticity involves enlargement or shrinkage of dendritic spines.

true

true or false: Neurons can depend on cable properties to move an impulse down the length of an axon.

false

true or false: PNS axons have a very limited ability to regenerate.

false

true or false: Schizophrenia is associated with too little dopamine

false

true or false: action potentials do not all have the same amplitude.

false

true or false: dendrites conduct impulses

false

true or false: glia conduct impulses.

false

What is the net effect of g protein coupled channel on membrane potential: muscarinic acetylcholine receptor

hyperpolarization in heart; depolarization in stomach

Synaptic plasticity

is the ability of synapses to change in response to activity.

When repeated high frequency stimulation enhances excitability of a synapse, it is called:

long-term potentiation (LTP).

Long-term depression (LTD)

occurs with prolonged periods of low-frequency stimulation of glutamate-releasing presynaptic neurons that stimulate the release of endocannibinoids. -This suppresses the further release of neurotransmitter.

At rest, when the inside of a neuron is more negative than the outside it is ______.

polarized

As the intensity of stimulation increases, more and more axons will become activated. This is called ___________.

recruitment.

A return to resting potential is called

repolarization

All cells in the body maintain a potential difference (voltage) across the membrane called the ______ ________ _________ in which the inside of the cell is negatively charged compared to the outside (-70 mV in neurons). •This potential difference is the result of: -Large negatively charged molecules inside the cell. -Na+/K+ pumps. -Permeability of the membrane to positively charged, inorganic ions. •At rest, there is a high concentration of K+ inside the cell and Na+ outside the cell.

resting membrane potential (rmp)

True or false: For ion channels that are ligand-gated, the receptor protein is also an ion channel; binding of the neurotransmitter directly opens the ion channel.

true

True or false: In an unmyelinated axon, potentials are produced down the entire length of the axon at every patch of membrane. Because of this the conduction rate is slow because so many action potentials are generated, each one, an individual event.

true

True or false: Neurons that use dopamine (dopaminergic neurons) are highly concentrated in the midbrain in two main areas: -Nigrostriatal dopamine system - involved in motor control. -Mesolimbic dopamine system - involved in emotional reward.

true

True or false: Repeated use of a neuronal pathway may strengthen or reduce synaptic transmission in that pathway.

true

True or false: Schwann cells form myelin sheaths around peripheral axons.

true

True or false: The changes in membrane potential can be measured using microelectrodes.

true

True or false: action potential conduction speed in an increased diameter of a neuron reduces resistance to the spread of charges via cable properties.

true

True or false: the neuron at the resting membrane potential is much more permeable to K+ than to Na+

true

true or false: A greater frequency of action potentials results in more stimulation of the postsynaptic neuron.

true

true or false: A stronger stimulus will make action potentials occur more frequently (frequency modulated).

true

true or false: All glutamate receptors also serve as ion channels and are named according to the molecules they bind: NMDA receptors AMPA receptors Kainate receptors

true

true or false: Any greater stimulus does not produce greater amplitude of action potentials. Thus, action potentials are not graded (varied); they are all-or-none.

true

true or false: Both LTP and LTD require a rise in calcium ion concentration within the postsynaptic neuron. -A rapid rise leads to LTP. -A smaller but prolonged rise leads to LTD.

true

true or false: Dendrites extend from the cell body; receive impulses and conduct graded impulse toward the cell body.

true

true or false: Drugs that treat schizophrenia are dopamine antagonists.

true

true or false: Each action potential remains a separate, all-or-none event.

true

true or false: In G protein coupled channels, either the alpha or the beta-gamma diffuses through the membrane to the ion channel which opens (or closes) the channel for short period of time. The G-protein subunits dissociate from the channel and it closes (or opens).

true

true or false: In the Nigrostriatal Dopamine System, Neurons from the substantia nigra (part of the basal nuclei) of the brain send dopaminergic neurons to the corpus striatum. This system is an important step in the control and initiation of voluntary movements.

true

true or false: In the conduction of a nerve impulse, the action potential is produced at all regions of the axon.

true

true or false: Myelinated axons conduct the action potential faster than unmyelinated axons because myelinated axons have voltage-gated channels only at the nodes of Ranvier, which are about 1 mm apart, whereas unmyelinated axons have these channels along their entire length.

true

true or false: Satellite cells support neuron cell bodies within the ganglia of the PNS.

true

true or false: Since action potentials are all-or-none events, a stronger stimulus cannot produce an AP of greater amplitude.

true

true or false: The amplitude (size) of action potentials is all-or-none. When depolarization is below a threshold value, the voltage-regulated gates are closed. When depolarization reaches threshold, a maximum potential change (the action potential) is produced.

true

true or false: The changes in membrane potential —depolarization, repolarization, and hyperpolarization—are caused by changes in the flow of ions through channels in the membrane.

true

true or false: When an axon in the PNS is cut, growth factors are released that stimulate growth of axon sprouts within the tube and the new axon eventually connects to the undamaged axon or the effector.

true

true or false: When it comes to ion gating in axons, Na+ has only voltage-gated channels that are closed at rest; the membrane is less permeable to Na+ at rest.

true

true or false: according to the all or none law, due to Na+ channel inactivation, voltage-gated K+ channel opening, and the concentration gradient for Na+, the amplitudes of all action potentials are about equal size (+30mV) and duration (3msec).

true

true or false: action potential conduction speed is faster in myelinated than unmyelinated because of insulation and saltatory conduction.

true

true or false: conduction rate of action potentials in myelinated axons are much faster than the conduction rate of an action potential in an unmylenated axon.

true

true or false: dendrites receive impulses and conduct graded impulses toward the cell body.

true

true or false: satellite cells and schwann cells which form myelin surrounds neurons in the PNS.

true