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BIO304H5 Lecture Notes - Lecture 3: Resting Potential, Resistor, Cell Membrane

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whitelouse363
10 Feb 2018
School
UTM
Department
Biology
Course
BIO304H5
Professor
Adriano Senatore

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Document Summary

Slide 27: battery is a source of voltage, resistor is a poor conductor, capacitor. Slide 28: the battery that plays out across the cell is spread out across all the cell membranes and all the regions of the ns, based on the difference in concentration. If the wall is too thick, they wont be able to interact. Slide 32: cell membrane is a really good capacitor because there are good electrostatic charges, most of our cells are the same in terms of their capacitance. For a small period of time, the ion are very concentrated at the channel. Slide 34: only 1/100,000 of all of the ions in a solution are required to generate the voltages that we see. Slide 39: when calcium rushes into the cell, they will find proteins and change their function (muscle contraction) Leaving calcium in the cell for too long can kill the cell.

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Related Questions

1. The plasma membrane of liver cells contains a glucose uniportthat transports glucose by facilitated diffusion. When the[glucose] is higher inside the liver cell than the [glucose]outside the liver cell, the glucose uniport will

A. couple the transport of glucose out of the cell to thehydrolysis of ATP

B. couple the transport of glucose into the cell to thehydrolysis of ATP

C. switch to a closed conformation, allowing no transport ofglucose

D. transport glucose out of the cell by passive transport

E. transport glucose in of the cell by passive transport

2. Unlike the positive charged ion shown in the middle diagramof figure 11-4B, K+ is higher in concentration inside the cell. Howwill the membrane potential of a cell at rest (shown in both themiddle and right-hand diagrams of Figure 11-4B) affect theelectrochemical gradient for K+?

A. The membrane potential will increase the electrochemicalgradient

B. The membrane potential will decrease the electrochemicalgradient

C. The membrane potential will have no effect on theelectrochemical gradient

3. Which of the following proteins carries out activetransport?

A. gluclose symport

B. Bacteriorhodopsin

C. ABC transporter

D. NA K pump

E. All of the above

4. Aquaporin will not transport Na+ ions because

A. Two asparagine residues in the channel prevent the passage ofNa+ ions by binding the oxygen of each water molecule as it passesby

B. Na+ ions are repelled by the positive charges at the entranceto the channel

C. Na+ ions cannot make contact with the carbonyl (C=O) groupson all four sides of the channel

D. The passage of Na+ ions is energetically unfavorable becauseone side of the channel is hydrophobic in nature

5. The acetylcholine receptor is different from other channelproteins we have discussed, such as the K+ leak channel,because

A. The acetylcholine channel is composed of a single polypeptiderather than multiple subunits

B. The acetylcholine channel transports Na+ ions against theconcentration gradient for sodium

C. The acetylcholine channel has a much smaller diameter thanother channel proteins

D. The acetylcholine channel transports ions with theirassociated shell of water molecules

E. The acetylcholine channel is always open, and never switchesto a closed conformation

6. After opening briefly along the axon of a neuron,voltage-gated ion channels switch to an inactivated conformationthat slowly returns to the original closed conformation of theprotein. This slow change in conformation, requiring about amillisecond, is important because

A. all of the ions that were transported across the membranewhen the ion channels were open must be actively transported backto the other side of the membrane, restoring the originalconcentration gradient, before the ion channels can open again

B. ATP hydrolysis is necessary to drive this energeticallyunfavorable change in conformation

C. it prevents the action potential from reversing direction andtraveling back toward the cell body of the neuron

D. the channel protein must be dephosphorylated in order tocomplete the transport process and return to the originalnonphosphorylated conformation

Which of the following statements is TRUE regarding sea anemones?
None of the answer options is correct.
Sponges—not sea anemones—possess what is considered to be the “simplest” nervous system found in animals.
Because sea anemones are “simple” organisms, these animals only possess motor neurons; sensory neurons or interneurons are never found in sea anemones.
Although sea anemones possess “net-like” nervous systems, these animals have brains located at their bases (near where they would attach to rocks).
Although sea anemones lack definitive brains, they do possess ganglia that serve a similar function to the paired ganglia of flatworms.
2. Some people have low levels of calcium circulating in the blood, a condition known as hypocalcemia. While for many this disorder has little to no effect, for some it can be life-threatening. How could low levels of calcium harm an individual?
Low levels of calcium would not have any effect on synaptic transmission.
Low levels of calcium would cause sustained depolarization of the presynaptic cell.
Low levels of calcium would result in fewer signals sent between the pre- and postsynaptic cell.
3. Cephalization is: the
All of these choices are correct.
development of a brain within the head of an animal.
concentration of sensory organs within the head end of an animal.
development of a “head end” in an organism.
4. Which of the following are TRUE about the resting membrane potential? (Select all that apply.)
It results from voltage-gated sodium channels remaining open for long periods of time.
It results from K+ ions diffusing out of the cell.
It results from the sodium-potassium pump moving more Na+ ions out of the cell than K+ ions into the cell.
5. Afferent and efferent neurons differ in:
their size.
the directionality of the information they send.
their pattern of myelination.
6. A neuron that responds to the environment is a(n):
interneuron.
homeostatic neuron.
motor neuron.
sensory neuron.
7. Which of the following is NOT the role of an interneuron?
stimulating a muscle to contract
conveying information from the internal environment of an animal
relaying information from sensory to motor neurons
maintaining homeostasis
8. Where are postsynaptic cell receptor proteins synthesized?
the Golgi apparatus
the lysosome
the cytoplasm
the rough endoplasmic reticulum
9. Inhibition of the flexor muscle during the knee-extension reflex is an example of:
homeostasis.
reciprocal inhibition.
negative feedback.
All of these choices are correct.
10. What type of cells produce myelin for sensory neurons?
pyramidal neurons
glial cells
melanocytes
astrocytes

Bad Fish: The Case of Tetrodotoxin

Part I – Poisoned!

One evening during a trip to Indonesia to study the recent sightings of a coelacanth, Dr. Marshall Westwood from the Montana Technical Institute sat down to a meal of pufferfish and rice. Within an hour of returning to his hotel room, he felt numbness in his lips and tongue, which quickly spread to his face and neck. Before he could call the front desk, he began to feel pains in his stomach and throat, which produced feelings of nausea and eventually severe vomiting.

Fearing he had eaten some “bad fish” for dinner, Dr. Westwood called a local hospital to describe his condition. The numbness in his lips and face made it almost impossible for him to communicate, but the hospital staff managed to at least understand the address he gave them and they sent an ambulance in response. As Dr. Westwood was rushed to the hospital, his breathing became increasingly difficult. In addition, he began to show signs of paralysis in his upper body and arms.

By the time the ambulance reached the hospital, Dr. Westwood’s face and mouth were completely paralyzed and he had an irregular heartbeat. The physicians helped by keeping his airway open, administering drugs to bring his heart back to a normal rhythm, and putting a mixture of charcoal into his stomach, which would help absorb any chemicals that might still be left there.

Within a few hours, Dr. Westwood’s condition improved and he was on his way to a full recovery. After discussing his case with his physician, he learned that he had probably been the victim of a pufferfish poisoning.

The active toxin in the tissues of this fish is a chemical called tetrodotoxin. Tetrodotoxin or (TTX) is in a class of chemicals known as neurotoxins due to the fact that it has its effects on nerve cells (neurons). Specifically, tetrodotoxin blocks voltage-gated sodium ion channels.

What follows is a series of questions relating to the basic biology of this case.

Answer the following questions about the case study:

1. How many different elements are contained in a molecule of tetrodotoxin? What are the names of these elements?

2. What is a voltage-gated sodium ion channel? What is it made of? What is its function?

3. Why do sodium ions need channels in order to move into and out of cells?

4. Describe the process involved in the movement of ions through these channels.

5. When nerve cells are at rest, there is an unequal amount of positive and negative charges on either side of a nerve cell membrane. This charge difference is called an electrical potential. Describe this “potential” when the neuron is at rest (resting potential).

6. What is happening to the electrical potential of a neuron when it generates an action potential? What is the function of the action potential in neurons?

7. Describe the role of sodium ions and sodium channels in the action potential.

8. What would happen to a neuron if it were exposed to tetrodotoxin? Be specific regarding its effect on the ability of a neuron to communicate.

9. Now that you have addressed some of the basic biology of this case, explain why Dr. Westwood experienced numbness after eating the pufferfish meal.

10. Paralysis is a term used to describe the loss of function of muscle. If tetrodotoxin’s effect is on neurons, why did Dr. Westwood experience paralysis?