CH 11 Assignment 2021-22 Introduction to Physiology. Language of Anatomy PDF

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Summary

This course will introduce students to fundamental concepts connected with the integrated activity of the human body in relation to its environment. Each organ system of the human body is studied from the perspective of structure, processes, and regulation. The course covers an introduction to the s...

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6/23/2021

CH 11 Assignment

CH 11 Assignment Due: 11:59pm on Wednesday, June 30, 2021 You will receive no credit for items you complete after the assignment is due. Grading Policy

Item 1 Label the main divisions of the nervous system.

Part A Drag the appropriate labels to their respective targets. ANSWER: Reset

Central nervous system (CNS)

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Peripheral nervous system (PNS)

Sensory (afferent) division

Motor (efferent) division

Somatic nervous system

Sympathetic division

Autonomic nervous system (ANS)

Parasympathetic division

Correct

Item 2

Part A Drag the appropriate labels to their respective targets. ANSWER:

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Reset

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Sensory input

Integration Motor output

Correct

Item 3

Part A Drag the appropriate labels to their respective targets. ANSWER:

Receptive region

Biosynthetic center and receptive region

Secretory region

Impulse generating and conducting region Impulse direction

Correct

Item 4 Label the parts of a motor neuron.

Part A Drag the appropriate labels to their respective targets. ANSWER:

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Dendrites

Cell body Nucleus

Axon Axon terminals Myelin sheath gap Initial segment of axon

Chromatophilic substance

Axon hillock

Schwann cell

Correct

Item 5 Generating a resting membrane potential depends on (1) differences in

and

concentrations inside and outside cells, and (2) differences in permeability of the plasma membrane to

these ions.Read through Focus Figure 11.1, and then complete the activities and questions below.

Part A - Ion Concentrations in the RMP Drag and drop the correct concentrations and the direction of the concentration gradient in a cell at RMP. Answers may be used more than once or not at all. The appropriate arrow should be placed on the plasma membrane—the targets appear on either side of the pumps.

Hint 1.

-

ATPase pumps

ATPase pumps maintain the gradients of maintaining the ion gradient, where would you expect

and across the cell membrane at rest. The to be more concentrated?

-

ATPase pump deposits 3

outside of the cell. If the pump is

Hint 2. Membrane potentials and basic diffusion A membrane potential is established when there are differing numbers of charged ions on either side of the cell membrane. If ions were allowed to flow freely across the membrane, they would flow from areas of high ion concentration to areas of low ion concentration until equilibrium were reached (i.e., the ion concentration is roughly equal on both sides of the membrane). ATPase pumps embedded in the cell membrane maintain the concentration gradients of and , such that each ion is more abundant on one side of the cell than the other.

ANSWER:

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High

Low

High

Low

High

Low

Correct The

concentration is higher outside of the cell, while the concentration of

is higher inside the cell.

Part B - Potassium (\rm K^+) Leakage Channels Which choice best characterizes

leakage channels?

Hint 1. Direction of movement through a leak channel Leakage channels permit facilitated diffusion across the membrane. This means that substances move across the membrane with their concentration gradients from areas of high concentration to areas of low concentration.

ANSWER:

transmembrane channels that use energy to allow the movement of transmembrane protein channels that are always open to allow

across the membrane to cross the membrane without the additional input of energy

common transmembrane channels that are always open for any ion to move through in the presence of chemically gated

channels that open and close according to the binding of other molecules

Correct

Part C - Sodium (\rm Na^+) Leakage Channels, Part I Assume you have a membrane with only potassium leakage channels. The RMP is –90mV. Predict the RMP if we add __________.

leakage channels.The most likely RMP value of

is

Hint 1. Membrane permeability The membrane is only slightly permeable to

. Thus, when

enters the cell through the leakage channels, it will have a slight effect on the RMP.

Hint 2. Predicting RMP The RMP will become more negative when positive ions leave the cell, or negative ions enter the cell. The RMP will become less negative when positive ions enter the cell, or negative ions leave the cell.

ANSWER:

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Correct

Part D - Sodium (\rm Na^+) Leakage Channels, Part II Imagine that the cell membrane from the previous problem becomes more permeable to

. Predict how this will affect the RMP.

Hint 1. Membrane permeability In a normal cell, the membrane is only slightly permeable to

. Thus, when

enters the cell through the leakage channels, it will have a slight effect on the RMP.

Hint 2. Predicting RMP The RMP will become more negative when positive ions leave the cell, or negative ions enter the cell. The RMP will become less negative when positive ions enter the cell, or negative ions leave the cell.

ANSWER:

The RMP will be unaffected. The RMP will be more negative. The RMP will be more positive. The RMP will be zero.

Correct

Part E - Leakage Channels and \rm Na^+-\rm K^+ Pumps Complete the following sentence. The operation of the

ATPase pump __________.

Hint 1. Membrane potentials and basic diffusion A membrane potential is established when there are differing amounts of charged ions on either side of the cell membrane. If ions were allowed to flow freely across the membrane, they would flow from areas of high ion concentration to areas of low ion concentration until equilibrium were reached (i.e., the ion concentration is roughly equal on both sides of the membrane). ATPase pumps embedded in the cell membrane maintain the concentration gradients of and , such that each ion remains more abundant on one side of the cell than the other, despite flow through leakage channels. Hint 2. ATPase ATPases are enzymes that hydrolyze ATP. The energy released from ATP's phosphate bonds can be used to do cellular work.

ANSWER:

releases 3 releases 1

to the ECF to the ECF and 1

to the cytoplasm

moves 3

to the ECF and 2

to the cytoplasm

moves 2

to the ECF and 3

to the cytoplasm

Correct The pumps move more

than

, which counteracts the effect of the membrane's being more permeable to

(more

leak channels than

).

Part F - Conclusion/Synthesis: Resting Membrane Potential, Part I

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You are going to record RMP from a cell using an electrode. You place your electrode and record a resting membrane potential every millisecond. You record an initial value of –70mV; however, over time you notice that your recordings become more and more positive until the RMP reaches 0mV. Assuming that and are the major determinants of RMP in this cell, which of the following could best explain your results?

Hint 1. How is the RMP maintained? A cell's RMP is a product of both passive and active processes. There are membrane proteins that facilitate the movement of ions with their gradients, but there are also proteins that actively move ions against their gradients. If the cell's RMP were solely a product of passive processes, then eventually ion concentrations on either side of the membrane would equilibrate.

ANSWER:

The cell's

leakage channels have stopped functioning.

The cell's

-

ATPase pumps have stopped functioning.

The cell's

leakage channels have stopped functioning.

The cell is becoming depleted of The cell is becoming depleted of

. .

Correct Yes! Since the RMP eventually becomes zero, the concentration of ions on either side of the membrane would be roughly equal. Without active processes to maintain concentration gradients, we would expect the concentration of ions on either side of the membrane to equilibrate.

Part G - Conclusion/Synthesis: Resting Membrane Potential, Part II is a common, negatively charged extracellular ion. Predict the effect on the RMP if many

gated channels are suddenly opened.

Hint 1. Predicting RMP The RMP will become more negative when positive ions leave the cell, or negative ions enter the cell. The RMP will become less negative when positive ions enter the cell, or negative ions leave the cell.

ANSWER: The membrane would become hypopolarized or have less charge separation across the membrane. There would be no change in the RMP. The RMP would become more positive. A more negative RMP would result.

Correct Correct! is negatively charged and has a higher concentration in the ECF. The opening of channels would allow more negative charge to attempt to enter the cytoplasm. If the cell's normal RMP were –70mV, it would now become more negative. The farther away the RMP is from zero, either in the positive or in the negative direction, the greater the separation of charges is. This is called hyperpolarization. When the RMP moves closer to 0 mV, depolarization occurs.Congratulations! You've successfully examined the construction of the resting membrane potential, an important concept in any human cell.

Item 6 Can you identify synapse structures?To review the structure of a chemical synapse, watch this BioFlix animation: How Synapses Work.

Part A - Structure of a chemical synapse Drag the labels onto the diagram to identify the various synapse structures. ANSWER:

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Vesicle

Neurotransmitter

Calcium channel Synaptic terminal

Synaptic cleft Receptor for neurotransmitter

Correct

Item 7 Watch the A&P Flix Generation of an Action Potential video and then complete the activity and question below.

Part A - Type of Channels Needed to Generate an Action Potential The generation of an action potential in a neuron requires the presence what type of membrane channels? Select the best answer.

Hint 1. Which Channels Change the Neuron’s Permeability to Na+ and K+ Ions? Recall from the beginning of the video: during the action potential, what channels open and close to alter the permeability of the plasma membrane to Na+ and K+ ions?

ANSWER:

chemically gated channels voltage-gated channels  leakage channels membrane channels are not required

Correct

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Part B - Events Involved in Generation of an Action Potential Action potentials (nerve impulses) are changes in the membrane potential that, once started, will affect the entire excitable membrane. The first action potential is usually generated at the initial segment of the neuron’s axon. This activity will test your understanding of the sequence of events that occur at the membrane of the initial segment of the axon during generation of an action potential. Place the events involved in generation of an action potential in the correct order of occurrence from left to right.

Hint 1. What Is Depolarization? Depolarization is when the membrane potential becomes more positive (or less negative); e.g., -70mV to -55mV. It is caused by more Na+ diffusing into the cell than K+ diffusing out of it.

Hint 2. What Is Repolarization? Repolarization is when the membrane potential becomes negative again and returns to its resting membrane potential; e.g., 30mV to -70mV. It is caused by K+ diffusing out of the cell after the voltage-gated Na+ channels begin to close.

Hint 3. What Is Hyperpolarization? Hyperpolarization is when the membrane potential becomes more negative, beyond the resting membrane potential. It is caused by K+ continuing to leave the cell for slightly longer than the time required to bring the membrane potential back to its resting level.

Hint 4. What Is a Threshold Stimulus? A threshold stimulus is a stimulus with the minimum current required to reach threshold (about -55mV) and initiate an action potential. Action potentials occur only when the membrane is stimulated enough so that sodium channels open completely.

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ANSWER:

Reset



Threshold stimulus Na+ channels open



Na+ influx Depolarization



Na+ channels close K+ channels open



K+ efflux Repolarization

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

Hyperpolarization K+ channels close

Correct Action potentials are all-or-nothing events. Once an action potential is generated at the initial segment, it will continue to propagate (move) along the entire length of the axon.

Item 8 Watch the A&P Flix Propagation of an Action Potential video and then complete the activities below.

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Part A - Events Involved in Continuous Propagation of an Action Potential The propagation of an action potential (AP) in an unmyelinated axon is called continuous propagation. This activity will test your understanding of the sequence of events that occur during continuous propagation. Place the events involved in the propagation of an action potential in the correct order of occurrence from left to right.

Hint 1. How Are Local Currents Generated? The flow of local currents is due to the movement of Na+ between the cytosol and the extracellular fluid. The local current spreads in all directions, depolarizing adjacent portions of the membrane. Each time a local current develops, the action potential moves down the axon (away from the soma) because the previous axon segment is still insensitive (absolute refractory period) to another depolarizing stimulus.

ANSWER:

Reset

 

Local current flows to axon segment

Axon segment depolarized to threshold





Voltage-gated Na+ channels open

Help



Influx of Na+

AP regenerated in adjacent axon segment

Correct After depolarization, voltage-gated Na+ channels are inactivated and voltage-gated K+ channels open. This renders that segment of the axon temporarily refractory (insensitive) to another depolarizing stimulus and forces the action potential to move down the axon toward the next segment where the voltage-gated Na+ channels are closed and receptive to a depolarizing stimulus.

Part B - Saltatory Conduction Saltatory propagation occurs in _________ axons, in which action potentials _________. Select the best answer.

Hint 1. What Does "Saltatory" Mean? The prefix salta- means "leap." In saltatory propagation, the action potential appears to leap or jump along the axon. Hint 2. Saltatory versus Continuous Propagation Refer to the images of continuous and saltatory propagation shown below. How are the axons different from each other?

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ANSWER:

myelinated; move from one node of Ranvier to another myelinated; move continuously along the axon toward the axon hillock unmyelinated; spread by depolarizing the adjacent region of the axon membrane unmyelinated; move from one node of Ranvier to another

Correct Saltatory propagation is much faster than continuous propagation. The speed of propagation along an axon varies in two ways: 1) myelin sheaths limit the movement of ions across the axon membrane, thereby requiring the action potentials to "leap" from node to node during propagation, thus traveling at a greater speed; and 2) the diameter of the axon directly relates to the speed of propagation (i.e., the larger the diameter of the axon, the faster the speed of propagation).

Item 9 Click the link and study the entire Focus Figure. Complete the following interactive steps to follow the message transmission from one neuron to another cell through a chemical synapse.

Access larger version of Focus Figure 11.3.

Messages travel from one neuron to the next through an extracellular space called a synapse, or synaptic cleft. A chemical message called a neurotransmitter, released by exocytosis from the terminal axon of the first cell, called the presynaptic cell, carries the message to the second cell, the postsynaptic cell, by diffusion. 

In this chemical synapse, conditions favoring diffusion will favor the neurotransmitter's movement.

Neurons

Examine the two neurons shown (one total, and only the axon of another). 

Part A Arrange the parts in order, from left to right, of a successful direct depolarization path within one neuron.

Hint 1. Threshold stimulus location

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CH 11 Assignment

In a typical neuron, the types of ion channels in the membrane vary by location. This means that some parts of the neuron's membrane are more excitable, or better able to generate an action potential. The most excitable part of a neuron is usually the axon hillock, which is where most action potentials are generated. Hint 2. What is the difference between a dendrite and an axon? Dendrites and axons serve different purposes in terms of the flow of information within a neuron, and from one neuron to another. One major difference between them is that they transmit information in opposite directions.In general, which of the following is the best ans...