Question 1

Training for long-distance running causes a significant increase in

Accepted Answer

Training for long-distance running primarily targets the slow-twitch muscle fibers, which have a greater capacity for endurance activities. This results in an increase in both the cross-sectional area of these fibers and the number of myofibrils per fiber, leading to an increase in cell size. Therefore, both options A and B are correct. However, there is no evidence to suggest that long-distance running increases the actual number of slow-twitch muscle fibers in the body, so option C is not correct. Thus, the best choice(s) are A and B, making option D the correct answer.

Question 2

What would happen to people exposed to a chemical warfare agent that blocked acetylcholine from binding to muscle receptors?

Accepted Answer

Blocking acetylcholine from binding to muscle receptors would prevent muscle contractions, causing paralysis.

Question 3

A patient is hospitalized with muscle spasms caused by failure of back muscles to relax after contraction.Which of the following would be most likely to help?

Accepted Answer

The answer of A patient is hospitalized with muscle spasms...

Question 4

When an action potential from a motor neuron arrives at the neuromuscular junction (NMJ),a series of events occurs that leads to muscle contraction.Which of the following events will occur last (i.e.,after all of the others)?

Accepted Answer

The conformational change in troponin occurs last in the process of muscle contraction, after ACh release, depolarization of the muscle cell, and release of Ca⁺⁺ from the sarcoplasmic reticulum have all occurred. This conformational change in troponin allows for the binding of myosin to actin, ultimately leading to muscle contraction. Action potential propagation down the T-tubules occurs earlier in the process, as it is necessary to trigger the release of Ca⁺⁺ from the sarcoplasmic reticulum.

Question 5

Which of the following is not a true description of the transduction of a stimulus by sensory receptors into signals in the form of action potentials?

Accepted Answer

Olfactory receptors do not work by bending cilia in hair cells; instead, odorant molecules bind to receptors on the cilia of olfactory sensory neurons, leading to a signal transduction pathway that results in depolarization.

Question 6

Which of the sequence of events below best describes how hair cells (sterocilia)in the rabbit ear provide the brain with information about stimulus intensity?

Accepted Answer

Hair cells in the ear respond to mechanical stimuli by opening K⁺ channels, leading to depolarization. This results in neurotransmitter release and action potentials in the afferent neuron, with intensity reflected in the frequency of action potentials.

Question 7

Compared to human eyes,the eyes of cephalopods (squid and octopus)

Accepted Answer

Cephalopods have an adaptive advantage because their eyes do not have a blind spot, unlike human eyes, which have a blind spot due to the placement of the optic nerve.

Question 8

You have a baby that does not seem to respond to sound.Upon thorough investigation by the doctor,there is nothing visibly wrong with the baby's ears.What internal issue may there be that is causing hearing impairment in your baby?

Accepted Answer

The cochlea is responsible for translating sound vibrations into electrical signals that the brain can interpret. Malformed stereocilia within the cochlea can prevent them from bending and transmitting these signals properly, resulting in hearing impairment. As there is nothing visibly wrong with the baby's ears, the issue is likely to be internal. Options A and B both involve problems with the middle ear or auditory ossicles, which are parts of the outer ear, so they are not the best choices in this scenario.

Question 9

Which sequence of events below best describes how sensory receptors within the lateral line of many fish provide information about stimulus intensity to the brain?

Accepted Answer

Sensory receptors within the lateral line of fish detect water movement and produce a depolarizing signal that leads to a large change in membrane potential. This large change in membrane potential induces a high frequency of action potentials, which are then relayed to the brain to provide information about the intensity of the stimulus. Hyperpolarization, on the other hand, would lead to a decrease in action potential firing and provide less information about stimulus intensity.

Question 10

When a doctor tests your patellar reflex by tapping the tendon on the front of your knee,your lower leg comes forward.Which muscle is activated in this reflex?

Accepted Answer

The patellar reflex, also known as the knee-jerk reflex, is a reflex arc that involves the activation of the quadriceps muscle, which causes the lower leg to extend or come forward in response to the tap on the patellar tendon. The hamstring muscle, located in the back of the thigh, is not involved in this reflex.

Question 11

Rhodopsins are light-sensitive molecules composed of a protein (opsin)and a pigment (retinal).The opsin portion of rhodopsin is an example of a

Accepted Answer

The opsin portion of rhodopsin spans the membrane several times, making it a polytopic integral membrane protein. This allows it to interact with the retinal pigment embedded in the membrane, allowing for light sensing. Peripheral proteins and phospholipids are not embedded in the membrane, and monotopic membrane proteins span the membrane only once.

Question 12

What effect would this conotoxin have on the prey?

Accepted Answer

Conotoxins are known to target and block ion channels on the neurons, leading to paralysis of the skeletal muscle. Therefore, choice B is the correct option. Choice A is incorrect as muscle spasms are not a typical effect of conotoxins. Choice C is also incorrect as conotoxins do not typically affect the digestive tract smooth muscle, and this would not be a useful adaptation for a predatory snail like the cone snail.

Question 13

Acidic amino acids will taste sour.

Accepted Answer

Acidic amino acids such as aspartic acid and glutamic acid have a sour taste. Therefore, the statement is true.

Question 14

What is the function of the sarcoplasmic reticulum?

Accepted Answer

The sarcoplasmic reticulum (SR) is a specialized type of smooth endoplasmic reticulum found in muscle cells. Its main function is to store and release calcium ions (Ca²⁺) in a controlled manner, which is essential for muscle contraction. When the muscle is stimulated, calcium ions are released from the SR into the cytoplasm of the muscle fiber, where they bind to the protein troponin, causing a conformational change that leads to muscle contraction.

Question 15

Mammals have a family of 500 and 1000 genes that encode receptor proteins on the surface of odor-receptor neurons.If all mammals have these genes,why do some mammals have a better sense of smell than others do?

Accepted Answer

Some of the genes may have been mutated and rendered inactive in some species but not in others. This can result in some species having a better sense of smell than others due to differences in the number and activity of odor-receptor genes.

Question 16

What causes rigor mortis?

Accepted Answer

The answer of What causes rigor mortis?
...

Question 17

Two students studying physiology taste a known "bitter" substance,and both report sensing bitterness.They then sample another substance.Student A reports sensing both a bitter taste and a salty taste,but student B reports only a salty taste.What is the most logical explanation?

Accepted Answer

Student A's perception of both a bitter and salty taste suggests that they have taste buds capable of detecting both tastes present in the substance. Student B's report of only a salty taste suggests a lack of sensitivity to the bitter taste, which could be due to the absence of the specific protein receptor required for detecting the bitter molecule. The other answer choices are less plausible explanations and do not fit with the given information.

Question 18

How do citrus fruits such as lemons cause the basic taste of sour?

Accepted Answer

Citrus fruits contain citric acid which releases protons (H⁺ ions) that directly flow into taste cells through H⁺ channels in the plasma membrane. The influx of positively charged protons into the taste cells triggers a response that is interpreted by the brain as sour taste.

Question 19

This particular conotoxin inhibits acetylcholine receptors that are located

Accepted Answer

The conotoxin inhibits acetylcholine receptors, which are primarily located on the postsynaptic membrane of the muscle cell at the neuromuscular junction. While acetylcholine receptors can also be found on the presynaptic membrane of the neuromuscular junction (where they play a role in regulating neurotransmitter release), this is not the primary target of this particular conotoxin. Acetylcholine receptors are not typically found on the dendrites of motor neurons, nor are they located along the axon itself. Therefore, Option D is the most accurate choice.

Question 20

What would be the effect on muscle contraction if troponin were experimentally altered to no longer interact with tropomyosin,so the complex could no longer bind to actin?

Accepted Answer

The answer of What would be the effect on muscle...

Quiz 46: Animal Sensory Systems and Movement