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Chemical and electrical synapses are similar in that __________. (a) communication is often bidirectional (b) there is a physical connection between cells (c) the signal can be depolarizing or hyperpolarizing (d) second messenger molecules may be involved Answers a, b, and d are correct. Answers c and d are correct.
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Page 1: chp 8

Chemical and electrical synapses are similar in that __________.

  (a) communication is often bidirectional

(b) there is a physical connection between cells(c) the signal can be depolarizing or hyperpolarizing(d) second messenger molecules may be involvedAnswers a, b, and d are correct.

Answers c and d are correct.

  Neurotransmitters at chemical synapses can bind receptors that trigger the production of second messengers. Second-messenger molecules can also travel through gap junctions at electrical synapses. Postsynaptic potentials at chemical synapses and the

Page 2: chp 8

membrane potential changes communicated through electrical synapses can be depolarizing or hyperpolarizing.

Put the events of synaptic transmission in the correct order: neurotransmitter binds to postsynaptic receptors action potential invades the presynaptic terminal calcium enters the presynaptic terminal exocytosis of neurotransmitter

   

b, c, d, a

  a, b, c, d

  d, b, c, a

  b, d, a, c

The events of synaptic transmission begin when an action potential invades a presynaptic terminal, which opens voltage gated calcium channels. The rise in calcium concentration in the terminal triggers the processes that result in transmitter release. The transmitter then binds to receptors on the postsynaptic cell.

Once neurotransmitter has bound to postsynaptic receptors, it may __________.

   

(a) remain there for several seconds

  (b) be degraded by enzymes

  (c) be taken up by the presynaptic terminal

  (d) diffuse out of the synaptic cleft

  Answers b, c, and d are correct.

  All of the above are correct.

Neurotransmitter molecules stay in the synaptic cleft only briefly, as they are either broken down, taken up by the presynaptic terminal, or diffuse away.

Metabotropic receptors __________.

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(a) are linked to G proteins

  (b) always act through second messengers

  (c) are linked directly to ion channels

  (d) can trigger the opening or closing of ion channels

  Answers a and d are correct.

  Answers a, b, and d are correct.

Metabotropic receptors are linked to G proteins, which may interact directly with a channel, or may act on a channel through second messengers.

The Vm of a postsynaptic neuron = -75 mV. The threshold for firing an action potential = -56 mV. An 8 mV PSP that is due to the closing of potassium channels and a 12 mV PSP due to the opening of sodium channels arrive simultaneously at the cell. The neuron __________.

   

fires an action potential

  remains at its resting potential

  hyperpolarizes

  None of the above are true.

The closure of potassium channels depolarizes the postsynaptic neuron by 8 mV. The opening of sodium channels depolarizes the neuron by 12 mV. -75 + 8 + 12 = -55 mV, which is 1 mV more depolarized than the threshold, so the postsynaptic cell will fire an action potential.

The most common type of neurotransmitters in the central nervous system are the __________.

   

neuropeptides

  amino acids

  biogenic amines

  catecholamines

Which of the following neurotransmitters do not bind to receptors on the postsynaptic cell?

   

nitric oxide

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  GABA

  serotonin

  acetylcholine

Nitric oxide is actually a gas, and diffuses directly through cell membranes-it does not bind to a receptor.

Which of the following statements about summation is(are) true? 

  Temporal summation involves more than one synapse.

  Spatial summation involves only one synapse.

  Summation is necessary because a single EPSP is unlikely to bring a postsynaptic neuron to threshold.

  None of the above are true.

Consider neuron D, which is postsynaptic to neurons A and B. In addition, neuron C forms an axo-axonic synapse with neuron B only. When neurons A and B are both active, neuron D fires an action potential. When neurons A, B, and C are all active, neuron D does not fire an action potential. Which of the following statements is(are) true about these synapses?

   

The interaction between neurons C and B is termed presynaptic facilitation.

  The synapses between neurons A, B, and D must both be excitatory.

  The interaction between neurons A, B, and D is an example of temporal summation.

  None of the above are true.

It would be helpful to make a drawing of these four neurons showing how they interact with each other. Because more than one synapse is involved, this is an example of spatial summation. Neuron C must inhibit neuron B, since neuron D stops firing when neuron C is active. However, from the information provided in the question, we can't know for sure if the synapse of neuron A onto neuron D is excitatory or inhibitory.

The neurotransmitter acetylcholine is broken down into choline and acetate in the synaptic cleft by the enzyme __________.

   

catechol-O-methyltransferase

Page 5: chp 8

  choline acetyl transferase

  acetylcholinesterase

  monoamine oxidase

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Postsynaptic potentials __________.

  (a) are graded potentials

(b) require the activation of second messenger systems

(c) must be excitatory to move the membrane potential of the postsynaptic cell closer to thresholdAnswers a and c are correct.

Answers b and c are correct.

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The amount of neurotransmitter released depends on __________.

   

the level of membrane depolarization in the presynaptic terminal

  the amount of transmitter packaged into each synaptic vesicle

  the concentration of calcium in the presynaptic terminal

  the frequency of action potentials invading the presynaptic terminals

  All of the above are correct.

An inhibitory postsynaptic potential (IPSP) may __________.

   

open chloride channels

  stabilize the membrane potential of the postsynaptic neuron at the resting potential

  move the membrane potential of the postsynaptic neuron away from threshold

  All of the above are correct.

Nicotinic acetylcholine receptors are located in the __________.

   

(a) central nervous system

  (b) synapses between neurons and muscle cells

  (c) autonomic nervous system

  Answers a and c are correct.

  All of the above are correct.

Channels that allow both sodium and potassium ions to move through them will ___________ a cell's membrane potential.

   

not change

  hyperpolarize

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  depolarize

  repolarize

A postsynaptic response that closes potassium channels usually __________.

   

(a) is excitatory

  (b) is inhibitory

  (c) involves phosphorylation of the channel

  (d) is a slow response

  Answers a, c, and d are correct.

  Answers b, c, and d are correct.

The Vm of a postsynaptic cell equals -70 mV. ECl- equals -80 mV. Which of the following is true?

   

Chloride is actively transported into the cell.

  Opening chloride channels will not change the membrane potential.

  A neurotransmitter that closes chloride channels will be excitatory.

  None of the above.

The Vm of a postsynaptic neuron is -70 mV, and EK+ = -75 mV. If a neurotransmitter closes potassium channels in this neuron __________.

   

(a) the synapse is excitatory

  (b) the synapse is inhibitory

  (c) the membrane will depolarize

  (d) the membrane will hyperpolarize

  Answers a and c are correct.

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  Answers b and d are correct.

Catecholamines ___________.

   

(a) often act through fast ionotropic receptors

  (b) can modulate their own release by acting through autoreceptors

  (c) include histamine

  Answers a and c are correct.

  Answers b and c are correct.

Combining the anti-anxiety drug benzodiazepine or the sleep inducing drug zolpidem with alcohol can be deadly because __________.

   

(a) all these drugs act at the same GABAergic synapses

  (b) these drugs can act synergistically

  (c) all these drugs are sedatives

  Answers a and b are correct.

  All of the above are correct.

Consider a neuron with Vm = -70 mV. Enough IPSPs arrive at this neuron simultaneously to open all the potassium channels in the membrane. EK+ = -94 mV. The postsynaptic membrane potential will __________.

   

hyperpolarize to a membrane potential more negative than -94 mV

  move toward -94 mV but not reach it

  depolarize due to the opening of sodium leak channels

  hyperpolarize to a membrane potential equal to -94 mV

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Neurons A and B synapse on a postsynaptic cell (Vm = -70 mV, threshold = -65 mV). Neuron A produces a 6 mV PSP due to the closing of potassium channels. Neuron B produces an 8 mV PSP due to the opening of chloride channels (ECl- = -78 mV). Neuron B's synapse is closer to the axon hillock than neuron A's. If the PSPs from neurons A and B arrive simultaneously, the postsynaptic cell will __________.

   

hyperpolarize

  not change its membrane potential

  depolarize but not fire an action potential

  fire an action potential

Which of the following is true about cholinergic receptors?

   

Nicotinic receptors always produce EPSPs.

  Nicotinic receptors are linked to G proteins.

  Muscarinic receptors are ionotropic.

  Muscarinic receptors are the most plentiful type of cholinergic receptor in the CNS.

Which of the following is a biogenic amine?

   

dopamine

  histamine

  serotonin

  all of the above

Which of the following neurotransmitters are synthesized in the axon terminal?

   

(a) substance P

  (b) dopamine

Page 11: chp 8

  (c) acetylcholine

  (d) vasopressin

  Answers a and b are correct.

  Answers b and c are correct.

Which of the following are neurotransmitters?

   

ATP

  ADP

  GTP

  all of the above

  none of the above

Antidepressants (depending on the type of drug) may modulate the function of which of the following types of synapses?

   

(a) noradrenergic

  (b) cholinergic

  (c) serotonergic

  (d) dopaminergic

  Answers a and b are correct.

  Answers a and c are correct.

Which of the following is true about neuropeptide transmitters?

   

They often act through G proteins.

  They often act as hormones in the endocrine system.

  They are usually colocalized with other neurotransmitters.

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  All of the above are correct.

In axoaxonic synapses, the presynaptic neuron may __________.

   

(a) alter the membrane potential of the postsynaptic neuron

  (b) decrease transmitter release from the postsynaptic neuron

  (c) enhance transmitter release from the postsynaptic neuron

  Answers b and c are correct.

  All of the above are correct.

A synapse may be __________.

  (a) axosomatic

(b) axodendritic

(c) dendrodendritic

(d) axoaxonic

Answers a, b, and c are correct.

All of the above are correct.

Neurons and glial cells communicate with each other via   synapses.

 

Postsynaptic receptors that are linked to channels are also called   receptors.

 

electrical

ionotropic

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 postsynaptic potentials often involve the opening of potassium or chloride channels.

 

 summation is a type of neural integration involving more than one synapse.

 

Increasing the strength of the suprathreshold stimulus increases the frequency of action potentials,

an effect called  (2 words). Frequency coding

 

In   (2 words), a modulatory neuron increases the amount of transmitter released from the axon terminals of a neuron. presynaptic facilitation

 

 cholinergic receptors are metabotropic and operate through the action of a G protein.

 

inhibitory

spatial

frequency co

Muscarinic

Page 14: chp 8

 is a neurotransmitter that is derived from the excitatory amino acid glutamate, but its effects are inhibitory.

 

Many neuropeptide transmitters such as TRH and oxytocin also function as  .

 

Dopamine, norepinephrine, and epinephrine are known as  , biogenic amines that all have a six-carbon ring structure with two hydroxyl groups. catecholamines

 

Postsynaptic potentials __________.

  (a) are graded potentials

(b) require the activation of second messenger systems

(c) must be excitatory to move the membrane potential of the postsynaptic cell closer to thresholdAnswers a and c are correct.

Answers b and c are correct.

GABA

hormones

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Which of the following is true about cholinergic receptors?

   

Nicotinic receptors are linked to G proteins.

  Muscarinic receptors are the most plentiful type of cholinergic receptor in the CNS.

  Muscarinic receptors are ionotropic.

  Nicotinic receptors always produce EPSPs.

Antidepressants (depending on the type of drug) may modulate the function of which of the following types of synapses?

   

(a) noradrenergic

  (b) cholinergic

  (c) serotonergic

  (d) dopaminergic

  Answers a and b are correct.

  Answers a and c are correct.

In axoaxonic synapses, the presynaptic neuron may __________.

   

(a) alter the membrane potential of the postsynaptic neuron

  (b) decrease transmitter release from the postsynaptic neuron

  (c) enhance transmitter release from the postsynaptic neuron

  Answers b and c are correct.

  All of the above are correct.

Page 16: chp 8

Synaptic delay is primarily due to the time it takes for transmitter molecules to diffuse across the synaptic cleft.

  True

 False

Presynaptic modulation affects transmission to the postsynaptic cell at one synapse only.

  True

 False

1

Presynaptic modulation affects transmission to the postsynaptic cell at one synapse only.

Your Answer: True

9. The mechanism of action of many drugs prescribed today is unknown.

Your Answer:

True

10. The molecule ATP functions as a neurotransmitter at some synapses.

Your Answer:

True

The Nervous System II: Anatomy Review

1. The somatic nervous system stimulates _skeletal___________ muscle.

Page 17: chp 8

The autonomic nervous system stimulates __smooth_________ muscle, _____cardiac_______

muscle, and ________glands___.

2. The autonomic nervous system (ANS) consists two divisions, each innervating the effector

organs. The sympathetic nervous system (SNS) generally speeds up everything except digestion.

The parasympathetic nervous system (PNS) generally slows down everything but digestion.

Signals from the SNS cause the heart rate to _________, while signals from the PNS cause the

heart rate to ___________.

Signals from the SNS cause smooth muscles of the intestine to _________ contractions, while

signals from the PNS cause these muscles to _________ contractions.

Signals from the SNS also cause the adrenal gland to _________ epinephrine and

norepinephrine.

3. Neurons can excite or inhibit another neuron.

Exciting another neuron will increase the chances of a/an ___________________ in the second

neuron.

Inhibiting another neuron will make the chances of a/an __________________ less likely.

4. Axons from one neuron can synapse with the dendrites or soma of another axon.

These synapses are called ______________________ (on dendrites) and

_________________________ (on soma). They carry input signals to the other neuron.

Page 18: chp 8

Axons from one neuron can synapse with the axon terminal of another neuron. These synapses

are called ________________________, and they regulate the amount of

________________________ released by the other neuron.

5. The electrical synapse:

Electrical current flows from one neuron to another through _________________.

These synapses are always (excitatory or inhibitory).

Advantages of the electrical synapses:

1. _______ signal conduction

2. _____________ activity for a group of neurons.

6. The chemical synapse:

Chemical synapses are not as fast as electrical but are the most common type of synapse.

A chemical, called a ______________________, is released from the sending neuron and travels

across the ___________________(a gap between the neurons) to the receiving neuron.

Advantages of the chemical synapse:

1. The signal can be either ____________ or ____________.

2. The signal can be ______________ as it passes from one neuron to the next.

7. The neuron conducting the impulse toward the synapse is called the __________________

neuron. The axon terminal contains ___________ ____________ filled with

______________________.

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An action potential in the axon terminal of the _____________neuron causes the chemical

transmitter ____________________ to be released. It diffuses across the synaptic cleft and

binds to receptors on the ________________ membrane.

These receptors open __________________. The movement of the charged particles causes an

electrical signal called a _______________________.

HUMAN PHYSIOLOGY CHAPTER EIGHTNeed to Know Concepts

Neuron/s

Key Concepts that will be part of Exam 2 Part 1 & 2 from lecture:

1. Neural synapse. Lecture2. Types of ion channels Lecture3. Types of myelination Lecture4. Factors affecting probagation Lecture5. Action potential Lecture

Make sure to use the CD that comes with the book to look at the animations this will be very helpful.

Use the study guide given in class to make your study focus sheet. Use this to further get depth in understanding function.

1. Identify the structure/s2. Define the purpose3. How’s, where’s and what’s (mechanisms)

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a. How does the neuron get information to the next neuron

b. Where is it happening – the key structures – ionic movement, etc…

c. What is happening in order for each neuron to get information from one to the next specifically (ionic exchange, myelinated/unmyelinated, etc…)

4. Order of Progressiona. Synaptic transmissionb. Action potential

PRACTICE QUESTIONS CHAPTER 8

Electrical synapses depolarize and generate action potentials simultaneously. When one neuron forms a gap junction with another neuron, an _________ _________ is made.

a. chemical synapse b. electrical synapse

Electrical current cannot flow directly from one neuron to the other. A chemical, called a ____________, is released from the sending axon and carries the signal to the next neuron.

a. synapse b. ion c. neurotransmitter

The axon terminal of the presynaptic neuron contains membranous sacs called _________ ________ which are filled with ______________.

a. axon terminal, synaptic vesicles b. synaptic vesicles, neurotransmitter

An action potential that reaches the axon terminal causes synaptic vesicles, to fuse with it, releasing ____________ into the _________ _________.

a. acetyl choline, postsynaptic neuron b. neurotransmitter, synaptic cleft

Page 21: chp 8

Voltage-gated channels are responsible for generation and propagation of the _______ _______.

a. action potentials b. synaptic potentials c. resting membrane potentials

Electrical synapses operate by allowing electrical signals to be transmitted from one neuron to another through:

A.ion channels.

B.chemical synapses.

C.gap junctions.

D.leak channels.

E.all of the above.

The entrance of calcium ions into the axon terminal stimulates the:

A.reuptake of neurotransmitter from the synaptic cleft.

B.inactivation of the neurotransmitter.

C.release of the neurotransmitter by exocytosis.

D.blockage of postsynaptic receptors.

E.propagation of the action potential along the postsynaptic membrane.

If synaptic activity hyperpolarizes the membrane, the potential produced would be a/an:

A.resting potential.

B.action potential.

C.ESPS

D.IPSP

Page 22: chp 8

Graded potentials:

A.demonstrate “all-or-none.”

B.are always excitatory.

C.cannot be summated.

D.dissipate with distance.

E.are always inhibitory.

In order to be spatially summated, a neuron must be stimulated:

A.by one synapse in rapid succession.

B.with a hyperpolarizing stimulus.

C.by an axoaxonic synapse.

D.by two or more synapses at the same time.

E.at the cell body near the axon hillock.

Which of the following would require the greatest number of impulses in order to generate an action potential by temporal summation?

A.a synapse closest to the cell body

B.a synapse midway between the cell body and dendrites

C.a synapse on the most distal of dendrites

D.a synapse on the axon hillock

E.an axoaxonic synapse