BSC 1407 Exam 2

Odor molecule receptors are located on the _________ extending from olfactory receptor cells in the human nose. (C44)

cilia

After reaching the inner ear, the frequency of a sound primarily affects (C44)

the location of the greatest basilar membrane vibration.

When a neuron undergoes a change in membrane potential that is proportional to (i.e., varies depending on) the strength of the stimulus given to that neuron, this is referred to as (C42).

a graded potential

Identify the key feature of the action potential that ensures it will travel only one direction. (C42)

the inactivation state of the voltage-gated Na+ channel

The electrochemical gradient that determines how a charged ion will move through a permeable membrane depends upon (C42).

the combined effects of electrical forces and concentration differences across the membrane.

The transduction of sound waves into electrical signals takes place (C44).

within hair cells, as they are bent against the tectorial membrane, causing them to depolarize and release a neurotransmitter that stimulates sensory neurons.

The tapetum lucidum is a key adaptation for (C44)

visual sensitivity in nocturnally active animals.

The period following an action potential during which a neuron cannot be stimulated to generate another action potential is referred to as (C42).

the refractory period

The glandular secretions involved in digestion that would most likely be released as inactive precursors are (C46).

protein-digesting enzymes

If you touch a hot stove and burn your hand, the pain isn’t actually in your hand—it’s in your head. What evidence can you provide to substantiate this claim? (C41).

Sensory neurons and interneurons carry the heat sensation to the brain where it is interpreted as painful.

Most nutrients are absorbed across the epithelium of the (C46)

small intestine

The class of neurotransmitters that most commonly acts as a modulator of postsynaptic cell response are the (C46)

neuropeptides

A mechanism shared by both extracellular and intracellular digestion is (C41)

the ability to phagocytose food particles.

Otto Loewi performed an experiment in which he first electrically stimulated the vagus nerve connected to a frog heart. He then passed the fluid bathing this heart to a second chamber containing a second frog heart not connected to a nerve. What did Loewi observe? (C41)

The first heart showed a decrease in beat rate and so did the second heart.

In ruminants, cellulose digestion occurs in the (C46)

rumen & reticulum

Pufferfish (Fugu) is a delicacy in Japan but must be cleaned very carefully as their liver contains tetrodotoxin which blocks voltage-gated Na+ channels. Imagine you are testing for the presence of this toxin using a neuron in a dish. You apply an electrical stimulus to the neuron that should produce an action potential. What will you observe if tetrodotoxin levels are high enough to block the neuron's voltage-gated Na+ channels? (C42)

The neuron will show a normal resting potential, but will not exhibit depolarization when the stimulus is applied.

Identify the chemoreceptor(s) important for detecting possible toxic substances (C44)

bitter

A digestive cavity in which food enters an opening at one end and passes through the animal in one direction, as it is digested, is called the (C46)

alimentary canal

The large intestine concentrates undigested material by (C46)

absorption of salts and water across the epithelial surface of the lumen.

Which type of nutrient can pass across epithelial cells without any expenditure of ATP? (C46)

fat

The diarrhea that is a symptom of diseases like cholera is due to problems in the function of the (C46)

large intestine

In the mammalian digestive system, what is the primary site of nutrient absorption? (C46)

small intestine

The critical function of the sodium-potassium pump of neurons is to move (C42)

Na+ out of the cell and K+ into the cell.

You are out at night and hear a sound in the bushes. The electrical signal carrying this information to your brain is carried first by a (C44)

sensory neuron.

Synaptic integration is most accurately described as (C42)

the summing of multiple excitatory or inhibitory influences in a postsynaptic neuron.

Bile is crucial for _________ digestion because of its function in _________ (C46)

fat; emulsification

Graded potentials are particularly important for conveying stimulus intensity in (C42)

sensory neurons

Compare the leakage rates of sodium and potassium into and out of a neuron at rest. How is the relationship between these rates best described? (C42)

Leakage of potassium ions out of the neuron is greater than leakage of sodium ions into the neuron.

Explain the significance of what Loewi observed in his experiment with the two frog hearts. (C41)

It suggests that a chemical substance released from the first heart, when added to the second heart, reproduced the effects of electrical stimulation.

The neuronal pathways behind gustatory reception most closely parallel those of (C44)

olfaction

You turn on the shower and check the water temperature with your hand. Your brain is able to monitor increasing temperature because the thermosensitive neurons in your skin (C42/44)

transmit action potentials at a greater rate when the water warms up.

How do carnivores and herbivores differ? (C46)

Carnivores and herbivores require different enzymes to digest their food.

At rest, neurons exhibit a negative membrane potential. Among the factors that maintain this polarity, which is most DIRECTLY responsible for the difference between intracellular and extracellular ion concentrations? (C42)

Passive leakage of K+ ions across the membrane

The ion that increases its intracellular concentration in order to trigger the release of neurotransmitters is (C42)

Ca+

What is the most accurate description of SPATIAL summation? (C42)

Several inputs from DIFFERENT presynaptic cells create EPSPs that sum together to bring the neuron over the threshold for an action potential.

The part of the axon closest to the cell body is the (C42)

hillock

The surface area of the small intestine is dramatically increased due to the presence of _________blank on the luminal surface. (C46)

villi & microvilli

Cows are able to survive on a diet consisting almost entirely of cellulose because (C46)

cows have cellulose-digesting, symbiotic microorganisms in their rumens.

What explanation can you give for why the sodium-potassium pump does not run out of ions to move in or out of the cell? (C42)

Leak channels are always open, allowing the passage of sodium ions ( Na+ ) and potassium ions ( K+ ) across the membrane.

When the cell is NOT sending signals, the electrical difference between the inside and outside of a neuronal membrane is specifically referred to as the (C42)

resting potential

How does the digestion and absorption of fat differ from that of carbohydrates? (C46)

Most absorbed fat enters the lymphatic system, whereas carbohydrates directly enter the blood.

An individual has a condition in which environmental stimuli are received and converted into electrical signals, but the nervous system is damaged so that there is no awareness within the consciousness of the individual of the stimuli. What can be said of this situation? (C42)

The stimulus was transduced but not perceived.

If you applied a toxin that blocked non-voltage-gated potassium channels (i.e., the potassium "leak channels") in a resting neuron, it would cause the membrane potential to be (C42)

less negative

The correct sequence for a sound (a vibration) traveling into the mammalian ear would be listed as (C44)

pinna, tympanum, ossicles of middle ear, oval window, basilar membrane, hair cell

Birds store food in a modified portion of the lower esophagus called the (C46)

crop

In the avian and mammalian eye, the lens remains stationary but changes shape in order to focus on objects at various distances. This is called "accommodation" and is accomplished through adjusting muscle control of the lens in order to (C44)

bend light rays to varying degrees according to the angle at which light enters the eye.

In a neuron at rest, the membrane is most permeable to (C42)

potassium

Contrary to popular belief, stress is not usually the primary cause of ulcers, and many patients with ulcers do not over-produce acid. What Nobel prize-winning discovery demonstrated a previously unknown cause of ulcers? (C46)

the existence of a bacterial infection in the stomachs of most patients with ulcers

The lacteal, a lymphatic vessel in the center of each intestinal villus, functions in digestion by absorbing (C46)

lipids.

Saltatory conduction is a term applied to what appears to be a "jumping" movement of action potentials (C42)

along myelinated axons

Surgical removal of the pancreas would (C46)

eliminate the ability to store bile in the gallbladder.

If you were building an eye to function primarily in low light, but preserve some ability to perceive color, you would construct it using (C44)

mostly rods w/ some cones

The process of emulsification is crucial to the digestion of (C46)

lipids

What properties would maximize the speed of conduction in an axon? (C42)

Large diameter and myelination

Blockage of the common bile duct would be expected to affect (C46)

lipid digestion

When someone has cataracts, they may be able to have a surgical replacement of their cloudy lens with an artificial lens. The artificial lens implant will be clear, but it is also fixed in shape. Based on your knowledge of vision, would it usually be necessary to get a new prescription for their glasses following this surgery? (C44)

Yes, the artificial lens will be fixed, so it cannot give distance vision one moment and near vision the next.

Mr. Johnson was experiencing some hearing loss. To test his hearing, his doctor held a vibrating tuning fork tightly against Mr. Johnson's jaw. This sent vibrations through the bones of the skull, setting the fluid in the cochlea in motion. Mr. Johnson could hear the tuning fork this way, but not when it was held away from the skull a few inches from his ear. His hearing loss is most likely attributed to the (C44)

tympanum or the bones of the middle ear.

The tough outer covering of the eye is referred to as the (C44)

sclera

What is peristalsis? (C46)

smooth muscle contractions that move food through the alimentary canal

Salivary glands secrete _________blank to start the digestion of _________blank. (C46)

amylase; starch

Increasing the flow of Na+ ions into a neuron at rest (-70 mV initially) would trigger (C42)

depolarization

The giant squid axon has been used extensively in research to determine the mechanisms by which neurons generate electrical signals. Scientists used microelectrodes to measure the resting membrane potential (inside relative to outside) and discovered a difference of (C42)

-70 mV

One function of HCl secreted in the stomach is to convert pepsinogen into the active enzyme pepsin. Why don't stomach cells simply secrete pepsin instead? (C46)

If cells produced active pepsin, they would digest their own cellular proteins.

Humans are susceptible to scurvy because (C46)

they cannot synthesize vitamin C.

The two broad classes of cells in the nervous system include

1. those responsible for information processing, and

2. those providing mechanical and metabolic support.

These two categories of specialized cells are called (C42)

neurons & glial cells

Cats cannot synthesize the amino acid taurine. This means that in cats, taurine (C46)

is an essential amino acid.

In describing the initiation and transmission of action potentials in neurons, it would be INCORRECT to say that (C42)

information about the intensity of a stimulus is conveyed by changes in the size of the action potential generated.

The main class of neurotransmitters involved in regulating mood in vertebrate animals is (C46)

the biogenic amines

Interneurons are responsible for the distribution of sensory information and the coordination of motor activity. They are also involved with all higher functions, such as memory, planning, and learning. The more complex the response to a given stimulus, the greater the number of interneurons involved. Knowing this, what can you predict about the ratio of interneurons to sensory and motor neurons in the nervous system of higher animals? (C44)

Interneurons likely outnumber all other types of neurons combined.

Oral rehydration solutions that contain both salt and glucose are highly effective in treating severe dehydration caused by diarrhea and vomiting. However, glucose or salt alone are not effective. Why? (C46)

Sodium transport and glucose transport are coupled in the small intestine so that glucose accelerates absorption of salt and water.

When light strikes the rod cell, it becomes _________blank and glutamate releases onto bipolar cells _________blank. (C44)

hyperpolarized; decreases

A fish detects vibrations in the water by means of its _________blank, which contains numerous _________blank. (C44)

lateral line; hair cells

Identify the point in time during an action potential when a positive feedback process is occurring in a neuron. (C41/42)

as the neuron is being depolarized and passes the threshold potential

How do sensory cells communicate different types of information to the brain—touch versus light for example? (C44)

by using different neurons for different stimuli (e.g., light and touch)

The vision loss associated with glaucoma is most accurately explained by (C44)

intraocular pressure buildup due to poor drainage of the aqueous humor.

What is the mechanism of action of cocaine? (C42)

Blocks removal of dopamine and norepinephrine from the synaptic cleft by preventing reuptake into the presynaptic terminal.

What is the most accurate description of TEMPORAL summation? (C42)

Several inputs from the SAME presynaptic cell arrive in rapid succession, summing into a larger depolarization that brings the neuron over the threshold for an action potential.

Within the vestibular system of vertebrates, hair cells help detect movement when their cilia are bent by (C44)

otoliths

The receptor potential is most accurately described as (C42)

the membrane potential produced in the receptor cell by sensory transduction.

It is accurate to say that neural transmission across nearly all mammalian synaptic clefts is the result of (C42)

neural impulses causing the release of chemicals that diffuse across the cleft.

Predict the expected consequence(s) of applying a toxin that blocks voltage-gated Ca2+ channels in a neuron. (C42)

Neuron conducts action potentials normally, but would not transmit these potentials across chemical synapses.

What ions are important for establishing the resting potential in neurons? (C42)

Na+, K+ , and intracellular anions are all important.

The electrical difference across a neuronal membrane is measured in (C42)

millivolts

Photoreceptors are sensitive to what general type of sensory information? (C44)

electromagnetic radiation

Propose a valid reason to explain why is it critical that the K+ channel activation gate responds slightly slower to depolarization than the Na+ channel activation gate. (C42)

If both gates showed identical response times, movements of Na+ and K+ ions would cancel out each other's effects on membrane potential changes.

Where do you predict that the highest density of mechanoreceptors in the skin would be located? (C44)

in the hands & ears

In the dark, the Na+ channels in the outer segments of rod cells are (C44)

open

The perception of a certain pitch of sound depends partly on (C44)

which hair cells of the cochlea are stimulated.

After an action potential is triggered, the rapid increase in membrane potential can be attributed to (C42)

the opening of voltage-gated sodium channels.

The neurotransmitter released at neuromuscular junctions in vertebrates is (C46)

acetylcholine

You are explaining the biological basis of depression to a friend. What is the most accurate description? (C46)

Depression stems from decreased activity of synapses that release biogenic amines, such as serotonin.

The two distinct types of neurotransmitter receptors found in postsynaptic membranes are (C46)

metabotropic and ionotropic.

The type of receptor that consists only of a naked nerve fiber ending is called a (C44)

nociceptor

Synaptic vesicles discharge their contents by exocytosis at the (C42)

presynaptic membrane

Assess the merits of each action potential analogy; select the representation that corresponds most accurately. (C42)

An action potential happens like a row of dominoes falling; the signal has constant velocity and constant strength no matter how long the row of dominoes may be. 

Olfactory neurons first transmit their action potential to the central nervous system structure called the (C44)

olfactory bulb

In a reflex arc, the correct sequence of cell types through which an electrical signal would pass would be (C44)

sensory neuron → interneuron in the CNS → motor neuron

Our ability to respond to moderate heat and cold is due to (C44)

thermoreceptors