Midterm Questions

Question 1

Question 1
Adaptation can change the genetic composition of a population because

a. environmental stressors favor survival of certain genotypes

b. individuals possessing favorable genes tend to produce more offspring

c. genes are passed on only if offspring are produced

d. all of the above

Answer 1

d. all of the above.

Question 2

Metabotropic receptors typically generate a response by

a. both B and C

b. activating gene transcription

c. opening an ion channel via signaling from a second messenger cascade

d. becoming an open channel as soon as the ligand binds

Answer 2

c. opening an ion channel via signaling from a second messenger cascade

Question 3

When a stimulus is continually applied but the action potential frequency declines, this is called

a. receptor acclimation

b. receptor accommodation

c. receptor attenuation

d. receptor adaptation

Answer 3

c. receptor attenuation

Question 4

Action potentials are able to travel over long distances without decaying because

a. one action potential generates the next one in an adjacent area of membrane

b. the axons are perfectly insulated, so no current is able to leak out

c. the action potential uses completely different ions than graded potentials

d. once the electrical signal has passed threshold, it is impossible for the signal to decay

Answer 4

a. one action potential generates the next one in an adjacent area of membrane

Question 5

The term adaptation most commonly refers to

a. changes within an individual that are irreversible

b. changes within an individual that are reversible

c. changes within an individual that cannot be inherited

d. changes within a population seen over time

Answer 5

d. changes within a population seen over time

Question 6

What mechanism causes the voltage-gated Na+ channels to close during an action potential?

a. The inactivation gate is voltage sensitive and closes close to the equilibrium potential for Na+

b. The activation gate is sensitive to K+ and closes when its intracellular concentrations drop

c. The inactivation gate has a time-dependent closure

d. The activation gate is voltage sensitive and closes close to the equilibrium potential for Na+

Answer 6

d. The activation gate is voltage sensitive and closes close to the equilibrium potential for Na+

Question 7

Which structure is important for the formation of long-term memory in mammals?

a. hippocampus

b. hypothalamus

c. medulla oblongata

d. cortex

Answer 7

a. hippocampus

Question 8

The __________ nervous system is most active during periods of stress or physical activity, while the __________ nervous system is most active during periods of rest.

a. voluntary; involuntary

b. parasympathetic; enteric

c. parasympathetic; sympathetic

d. sympathetic; parasympathetic

Answer 8

d. sympathetic; parasympathetic

Question 9

Question 10
Which of the following structures is NOT included in the limbic system?

a. amygdala

b. hypothalamus

c. olfactory bulb

d. cerebellum

Answer 9

d. cerebellum

Limbic system is involved in memory, emotions, etc. all of the other things are part of that.

Question 9

Myelination increases the speed of conduction by decreasing the time constant and increasing the length constant. It achieves this by

a. decreasing both membrane resistance and capacitance

b. increasing both membrane resistance and capacitance

c. increasing membrane resistance and decreasing capacitance

d. decreasing membrane resistance and increasing capacitance

Answer 9

d. decreasing membrane resistance and increasing capacitance

Question 10

Question 1
The hair cells of the mammalian cochlea are contained in the

a. organ of Corti

b. tympanic membrane

c. round window

d. vestibular duct

Answer 10

a. organ of Corti

Question 11

Without a proprioceptive sense, you would NOT be able to

a. feel grains of sand on your fingertips

b. sense changes in temperature

c. clap your hands behind your back

d. autonomically control blood pressure

Answer 11

c. clap your hands behind your back

Question 12

With regards to hair cells involved in vertebrate hearing organs, we know that

a. the 9 + 2 arrangement of stereocilia allow for free bending to improve sound resolution

b. stereocilia are connected to each other by small fibers

c. their bending always causes an increase in firing in the primary afferent

d. mechanosensitive ion channels at the tips of stereocilia are all closed at rest

Answer 12

b. stereocilia are connected to each other by small fibers

Question 13

You are riding your bicycle over a very bumpy road, reading a street sign far ahead of you. Which sensory inputs are NOT required to accomplish this task?

a. proprioceptors

b. visual inputs

c. inner ear

d. All of the above are required

Answer 13

d. All of the above are required

Question 14

Mechanoreceptors translate mechanical signals into electrical signals when pressure on the cell

a. induces a conformational change in ion channels, allowing ions to flow

b. induces a change in cell volume that disrupts ion balance

c. activates a G protein signal transduction cascade

d. disrupts stability of the lipid bilayer, causing ions to flow

Answer 14

a. induces a conformational change in ion channels, allowing ions to flow

Question 15

Which eye structure constricts or dilates to control the amount of light that enters the eye?

a. Iris

b. Pupil

c. Lens

d. Retina

Answer 15

a. Iris

Question 16

In animals with binocular vision, it is true that

a. neurons responding to the right visual fields project to the left lateral geniculate nucleus

b. neurons from the retina of the right eye project to the left lateral geniculate nucleus

c. neurons of the nasal retina project to the left lateral geniculate nucleus

d. neurons of the temporal retina project to the left lateral geniculate nucleus

Answer 16

a. neurons responding to the right visual fields project to the left lateral geniculate nucleus

Question 17

Which of the following choices is FALSE? The chromophore

a. is covalently linked to a member of the opsin gene family

b. absorbs energy from photons

c. plays a role in photoreceptor sensitivity to different colors

d. is a derivative of vitamin D

Answer 17

d. is a derivative of vitamin D

Question 17

If the orientation of your ears were changed so that your right ear still faced forward but your left ear faced backward, how would your ability to locate the direction of an auditory stimulus change?

a. improved ability to distinguish above from below

b. There would be no improved ability at all

c. improved ability to distinguish left from right

d. improved ability to distinguish front from back

Answer 17

d. improved ability to distinguish front from back

Question 18

Mechanoreceptors are important for

a. touch

b. proprioception

c. hearing

d. all of the above

Answer 18

d. all of the above

Question 19

Vertebrate striated muscles composed of twitch fibers are able to produce a graded contraction by

a. summing EPSPs in the motor end-plate region

b. recruiting different numbers of motor units

c. having excitatory and inhibitory input to a single muscle

d. Vertebrate muscles are unable to produce graded contractions

Answer 19

b. recruiting different numbers of motor units

Question 20

Which myosin isoform is found in fast-twitch muscle?

a. perinatal

b. extraoccular

c. type I

d. type IIb

Answer 20

d. type IIb

Question 21

Which of the following pumps is specifically used to return Ca2+ to the sarcoplasmic reticulum?

a. NaCaX

b. SERCA

c. Ca2+ATPase

d. parvalbumin

Answer 21

b. SERCA

Question 22

During which phase of an excitation-contraction cycle does depolarization occur?

a. contraction

b. inhibition

c. excitation

d. relaxation

Answer 22

c. excitation

Question 23

What accounts for the differences in metabolic rates of animals?

a. body size

b. activity level

c. temperature

d. all of the above

Answer 23

d. all of the above

Question 24

The portion of the transmembrane receptor that binds to hydrophilic messengers is termed the

a. ligand-binding domain

b. transmembrane domain

c. intracellular domain

d. receptor-binding domain

Answer 24

a. ligand-binding domain

Question 25

Which of the following statements is inaccurate with respect to sonic muscles?

a. Sonic muscles must have fast Ca2+ transport

b. Rattlesnakes, cicadas, and toadfish are examples of animals with sonic muscles

c. Animals can modify their muscles to operate some 10 times faster than the fastest locomotor muscles in that animal

d. The fast speed can be attributed to some muscles being able to lengthen sarcomeres

Answer 25

d. The fast speed can be attributed to some muscles being able to lengthen sarcomeres

Sarcomeres can NEVER be lengthened. They can only be shortened, because muscles shorten when they contract.

Question 26

The __________ of the myosin is where ATP is broken down, providing energy for movement

a. light chains

b. head

c. neck

d. tail

Answer 26

b. head

Question 26

What is the function of capping proteins?

a. to stabilize the microfilament, allowing for increases in length

b. to prevent increased growth of microfilaments

c. allow the microfilament to bind to the cell membrane

d. to attach microfilaments together at a common point

Answer 26

a. to stabilize the microfilament, allowing for increases in length

Question 26

Which of the following compounds are endocrine disruptors?

a. polychlorinated biphynels and tyramine

b. anabolic steroids, polychlorinated biphenyls, and tyramine

c. anabolic steroids, tributyltin, and polychlorinated biphenyls

d. tributyltin, polychlorinated biphenyls, tyramine, and anabolic steroids

Answer 26

c. anabolic steroids, tributyltin, and polychlorinated biphenyls

Question 27

In striated muscle, Ca2+ regulates contraction by interacting with troponin and tropomyosin. Explain how Ca2+ is able to regulate the timing of contraction as well as affecting the kinetics of contraction.

Answer 27

An action potential reaches a muscle cell, and this electrical signal travels along the sarcolemma and into the cell via T-tubules.

the action potential triggers Ca2+ release from the sarcoplasmic reticulum.

Ca2+ binds to troponin which causes tropomyosin to expose the myosin binding sites on the actin.

the cross bridge forms when myosin attaches to actin, and then it will do its Power Stroke head pivot and pull the actin in to the centre of the muscle.

when calcium is removed, then the muscle will relax again. this is why it controls the timing too, because it’s calcium that has to leave before the muscle stops contracting.

Question 28

Actin and myosin interactions are utilized in many types of movement, including the movement generated by muscles. Explain how the movement of myosin down an actin filament can generate contraction of a muscle.

Answer 28

Ca2+ binds to troponin which moves tropomyosin out of the way of the myosin binding site, allowing the myosin heads to attach to the actin filament. the myosin heads will essentially walk along the actin filament, pulling it in close to the centre of the sarcomere. Since actin filaments are attached to the z discs of the muscle cell membrane, the muscle cell will shorten.
The process ocurring for all/many of the muscle cells is what shortens the entire muscle.
The sections of dark bands get larger, as the overlap between actin and myosin gets larger, and the light bands get thinner.

A muscle cannot actively lengthen because this is the only process it can do, which always shortens it.

Question 29

Hormones are chemicals that are released into the blood and travel all over the body where they can have effects on their target cells. Discuss the mechanisms that allow only the target cells to respond AND how target cells may have very different responses to the same hormone.

Answer 29

Hormones are released into the body by endocrine glands. In terms of paracrine hormones, they will act locally, affecting organs in the region where they’re manufactured. So, in those situations, it will be organs that are proximal to the gland that can be affected by the hormone.

But in terms of endocrine hormones which will be transported throughout the body via the circulatory system, firstly, they will be transported to the desired organs through the blood stream. Once they reach the cell, the way they interact with it will depend on if the hormone is hydrophobic or hydrophilic:

If it is hydrophilic, it will bind to a membrane receptor that is specific to this hormone. This is one of the ways a hormone can only affect a target cell - other cells will not have the receptors for these hormones to bind to. Once a hormone has bound to a receptor, the following sequence of events that occurs within the cell will be what differentiates its response from another cell’s. A cell may have a different pathway that is triggered as a result of the hormone, and the cell’s physiological conformation and connections will determine how it can respond.

For hydrophobic (lipid-soluble) hormones, they can diffuse right into the target cell. But once they diffuse, they still have to bind to a ligand receptor, and then this receptor must change shape before making its way to the nucleus. So, if a cell is not the target for this hormone, then the hormone will not be able to successfully bind to any receptors, and they will not change to make the proper conformation.

Once the receptor and ligand travel to the nucleus, then the rest of their pathway can take place. This is where the response to the same hormone can differ between cells, because from here, it depends on what pathway is triggered for them by this hormone and receptor.

Question 30

Compare and contrast positive and negative feedback loops.

Answer 30

POSITIVE FEEDBACK: it works to amplify an event. An initial stimulus is enhanced, leading to a greater response.
This type of feedback tends to move a system away from it’s regular/initial state.
ex: childbirth, blood clotting
–> Often leads to a ‘snowballing’ effect.
–>Not used for homeostasis.

NEGATIVE FEEDBACK: Surpress changes or keep system within a desired range for homeostasis.
A change in the system causes the system to OPPOSE it. crucial for homeostatic regulation.
Important to stabilize the system.

Question 31

Define hormones and explain the 4 characteristics that a substance must exhibit to be classified as a hormone. Briefly summarize the function of hormones and provide an example to support your answer.

Answer 31

Hormones are chemical messengers that are secreted by glands into the bloodstream. they regulate bodily processes.

The 4 characteristics to be a hormone are:

1. Chemical - a hormone has to be a chemical.
2. Secreted by a gland - hormones must be secreted by a gland or specialized cell, into the bloodstream.
3. Target specificity: Hormones must have a specific target cell, whose receptors they will bind to.
4. Regulation: Hormones must be regulated by positive or negative feedback loops.

Question 32

List the four necessary steps that are required for sensory reception. Different receptors are used to detect different stimuli: Briefly describe two examples of stimulus modality

Answer 32

1. Stimulus Detection: Sensory receptor detects the stimulus.
2. Transduction: This means that we traduce the signal into membrane potential energy, allowing an action potential to propogate.
3. Transmission: we transmit the signal to subsequent neurons along the pathway until we reach the brain.
4. Interpretation: the brain will interpret the stimulus that has been detected.

Question 33

How does the mammalian eye focus an image? In your description, name the important physical structures in image formation, define the focal point, and explain what accommodation is and why it is important.

Answer 33

The mammalian eye focuses an image using a combination of its primary optical elements: the cornea and the lens. The cornea, which is the transparent front layer of the eye, initiates the refraction of incoming light. The lens, located behind the iris, further adjusts the focus, a process known as accommodation.

Accommodation involves changing the shape of the lens via the ciliary muscles to adjust the focal length, ensuring that light rays precisely converge on the retina’s photoreceptive surface.

The focal point is the specific point at which light rays entering the eye converge to form a clear image.

This ability to dynamically focus on objects at various distances is crucial because it allows us to maintain clear vision across a range of conditions and distances.

Question 34

Why is it so difficult to localize sound with only one ear? How does having two ears help to localize sound?

Answer 34

it’s difficult to localize sound with one ear because we have no depth perception. When we hear a noise on the right side, it will reach out right ear first. it will also be louder in that right ear. And so, the slight discrepancy between when each ear hears the sound, and the volume of the sound, will let us know what side the sound occurred on.

Question 35

If all sensory signals are eventually transduced into the common action potential, then how do receptors encode stimulus modality? Give an example.

Answer 35

Labeled line coding.
Example: with taste receptors, each different flavour receptor responds to a different chemical stimulus, and then sends its information along a strict pathway, to a specific part of the brain. The pathways do not cross or interfere or get mixed up, which is how we keep information for different things separate.

Question 36

The absolute and relative refractory periods of an action potential determine other parameters of action potentials such as causing unidirectional conduction and limiting their frequency. Describe what is happening during each of the refractory periods. Then use this information to describe how the different periods affect conduction and frequency.

Answer 36

Absolute: This is right after an action potential has JUST occurred, and the ion channels are DEACTIVATED, and there CANNOT be any action potential generated from them, no matter how strong the stimulus is. This occurs so that the action potential never travels backward.

Relative: The relative refractory period happens after the absolute period, and here there CAN be an action potential generated, but it requires a strong stimulus. Some of the ion channels are active and some are not.

Question 37

List the 4 unifying themes of physiology and provide an example for each that is DIFFERENT from the primary examples provided on the lecture powerpoint file

Answer 37

1. Integrative
2. follows chem and physics laws
3. SHaped by evolution
4. Regulated

Question 38

List five ways that efferent motor pathways can be distinguished from autonomic pathways

Answer 38

1. Efferent motor is always Voluntary and Autonomic is involuntary.
2. Efferent motor acts on skeletal muscle and Autonomic acts on glands and smooth muscle.
3. Efferent motor pathway consists of a single neuron from the spinal cord to the muscle.
   Autonomic pathway has two neurons, one that is preganglionic and one that is postganglionic.
4. Efferent motor uses Acetylcholine, and Autonomic uses various neurotransmitters.
5. response: Efferent always leads to a muscle contraction, Autonomic will be either a sympathetic or parasympathetic response.

Question 39

You have isolated two neurons, joined by a synapse, in a Petri dish. You have stimulated the first neuron at the axon hillock and successfully generated an action potential. However, there is no response by the postsynaptic neuron. Describe possible malfunctions in synaptic transmission that would prevent the postsynaptic neuron from responding as it should.

Answer 39

-The neurotransmitters released by the first one might not actually be the correct ones that the following neuron’s receptors respond to.

-The vesicles might not be functioning properly, and maybe neurotransmitter isn’t actually getting delivered to the synaptic cleft.

-maybe the action potential wasn’t sufficient to excite the postsynaptic neuron.

-maybe the postsynaptic neuron’s receptors aren’t functioning properly.

-If the neurotransmitter released is an inhibitory one, then although the action potential itself is a depolarizing, excitatory event, it can indirectly cause inhibition at the postsynaptic neuron, reducing the likelihood of it firing an action potential.

Question 40

Neurons have four functional zones, and each performs a task required for communication. What are these four zones and what structural features found in each allow it to perform its function?

Answer 40

1. Signal Reception: This zone consists of the dendrites and the Soma. this is the zone where a neuron receives the signal, and a graded potential is generated.
2. Signal Integration: The Axon hillock is where the signal (if the graded potential is powerful enough), will be integrated into an action potential.
3. Signal Conduction: The axon conducts the signal down the neuron.
4. Signal Transmission: the signal is transmitted by the axon terminals, to the postsynaptic neuron.

Question 41

Describe the differences between electrical and chemical synapses in terms of mechanisms and functional characteristics of transmission.

Answer 41

ELECTRICAL: Electrical synapses transmit signals directly between neurons through gap junctions. These channels allow the direct passage of ions and small molecules between cells.
–> They’re very fast.
–> They’re bi-directional, so the signal can travel in both directions.
–>They’re simpler than chemichal synapses because they don’t have the whole complexity of neurotransmitter release and receptors.
–> often used in ESCAPE responses because they’re so fast.

CHEMICAL: The classic using neurotransmitters to send signals across a synaptic cleft.
–> Voltage gated ion channels open when
–> Slower than electrical syapses
–> Unidirectional! (as we know)
–> can AMPLIFY signals because a single action potential can produce many neurotransmitters, making a bigger postsynaptic response.

Question 42

Briefly describe lateral inhibition. Why is it useful?

Answer 42

Lateral inhibition is when a an excited neuron inhibits or suppresses the activity of surrounding neurons.
An example is when photoreceptor cells in the Retina detect light, they will send signals to adjacent cells to inhibit them.

Useful because it enhances contrast and detail, narrowing down the location of the stimulus to a specific spot.
It’s also useful for making sure we don’t get too much redundant information sent to the brain.