exam review 3

Opening all of the sodium channels on an otherwise typical neuron, with all other ion channels closed (which is an admittedly artificial setting), should move its membrane potential

) +62 mV

Single-celled Paramecium live in pond water (a hypotonic environment). They have a structural feature, a contractile vacuole, which enables them to osmoregulate. If you observed them in the following solutions, at which sucrose concentration (in millimolars, mM) would you expect the contractile vacuole to be most active?

) 0.0 mM sucrose

Which of the following is the correct sequence that describes the excitation and contraction of a skeletal muscle fiber? 1.Tropomyosin shifts and unblocks the cross-bridge binding sites. 2. Calcium is released and binds to the troponin complex. 3. Transverse tubules depolarize the sarcoplasmic reticulum. 4. The thin filaments are ratcheted across the thick filaments by the heads of the myosin molecules using energy from ATP. 5. An action potential in a motor neuron causes the axon to release acetylcholine, which depolarizes the muscle cell membrane.

) 5 → 3 → 2 → 1 → 4

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

) Muscle contractions would be prevented, causing paralysis.

Neurotransmitters are released from axon terminals via

) exocytosis

Marine cone snails from the genus Conus are estimated to consist of up to 700 species. These predatory molluscs have devised an efficient venom apparatus that allows them to successfully capture polychaete worms, other molluscs, or in some cases fish as their primary food sources. ... conotoxins from Australian species of Conus ... have the capacity to inhibit specifically the nicotinic acetylcholine receptors in higher animals." (B. G. Livett, K. R. Gayler, and Z. Khalil. 2004. Drugs from the sea: Conopeptides as potential therapeutics. Current Medicinal Chemistry Refer to the paragraph above on the venom of marine core snails. What is the adaptive value of this toxin? I) It would cause muscle spasms in the prey. II) It would result in paralysis of the skeletal muscle of the prey. III)It would stimulate digestive tract smooth muscle to cause nausea and vomiting of the prey

) only II

Which of the following are present in high densities in both smooth and skeletal muscle cells? I) cilia II) mitochondria III) nuclei

) only II and IV

The following steps refer to various stages in transmission at a chemical synapse. 1. Neurotransmitter binds with receptors associated with the postsynaptic membrane. 2. Calcium ions rush into neuron's cytoplasm. 3. An action potential depolarizes the membrane of the presynaptic axon terminal. 4. The ligand-gated ion channels open.

3 → 2 → 5 → 1 → 4

The muscles of a recently deceased human can remain in a contracted state, termed rigor mortis, for several hours, due to the lack of _____.

ATP needed to break actin-myosin bonds

How could you increase the magnitude of inhibitory postsynaptic potentials (IPSPs) generated at a synapse?

B) increase K+ permeability

The point of connection between two communicating neurons is called the _____.

C) synapse

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?

Induce tropomycin and troponin to bind to the myosin binding sites on actin.

In a resting potential, an example of a cation that is more abundant as a solute in the cytosol of a neuron than it is in the interstitial fluid outside the neuron is _____.

K+

Through studies of insect Malpighian tubules, researchers found that K+ accumulated on the inner face of the tubule, against its concentration gradient. What can you infer about the mechanism of transport?

Movement of potassium into the lumen of the Malpighian tubules is an energy-requiring process.

What happens if twice as many inhibitory postsynaptic potentials (IPSPs) as excitatory postsynaptic potentials (EPSPs) arrive at a postsynaptic neuron in close proximity?

No action potential results.

Why are the renal artery and vein critical to the process of osmoregulation in vertebrates?

The renal artery delivers blood with nitrogenous waste to the kidney and the renal vein brings blood with less nitrogenous wastes away from the kidneys.

A potassium ion gradient is set up in insect Malpighian tubules through an active transport process. As a result, potassium concentration is higher in the lumen of the tubules than in hemolymph. How would the potassium gradient affect water movement?

There would be a net movement of water into the lumen of the tubules

Which of the following is a direct result of depolarizing the presynaptic membrane of an axon terminal?

Voltage-gated calcium channels in the membrane open.

If you are hiking through the desert for several days, one would pack which of the following to ensure proper hydration?

a drink with a combination of water and electrolytes

Acetylcholine released into the junction between a motor neuron and a skeletal muscle binds to a sodium channel and opens it. This is an example of

a ligand-gated sodium channel

Which of the following animals generally has the lowest volume of urine production?

a marine bony fish

) Myasthenia gravis is a form of muscle paralysis in which _____.

acetylcholine receptors are destroyed by an overactive immune system

Self-propagation and refractory periods (states) are typical of

action potentials

One of the waste products that accumulates during cellular functions is carbon dioxide. It is removed via the respiratory system. What is another waste product that accumulates during normal physiological functions in vertebrates?

ammonia uric acid urea

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 (that is, after all of the others)?

conformational change in troponin

The activity of acetylcholine in a synapse is terminated by its

degradation on the postsynaptic membrane

The loop of Henle dips into the renal cortex. This is an important feature of osmoregulation in terrestrial vertebrates because

differential permeabilities of ascending and descending limbs of the loop of Henle are important in establishing an osmotic gradient

Action potentials in the heart move from one contractile cell to the next via

electrical synapses using gap junctions

A skeletal muscle deprived of adequate ATP supplies will

enter a state where actin and myosin are unable to separate

To maintain homeostasis freshwater fish must

excrete large quantities of water

Which process in the nephron is LEAST selective?

filtration

Low selectivity of solute movement is a characteristic of _____.

filtration from the glomerular capillaries

For a neuron with an initial membrane potential at -70 mV, an increase in the movement of potassium ions out of that neuron's cytoplasm would result in the _____.

hyperpolarization of the neuron

A simple nervous system _____.

includes sensory information, an integrating center, and effectors

A graded hyperpolarization of a membrane can be induced by _____.

increasing its membrane's permeability to K+

After drinking alcoholic beverages, increased urine excretion is the result of

inhibited secretion of antidiuretic hormone (ADH)

Most of the neurons in the human brain are

interneurons

The motor (somatic nervous) system can alter the activities of its targets, the skeletal muscle fibers, because _____.

its signals bind to receptor proteins on the muscles

Compared to oxidative skeletal muscle fibers, those classified as glycolytic typically have

less resistance to fatigue

Ionotropic receptors found at synapses are operated via

ligand-gated ion channels

Urea is produced in the _____.

liver from NH3 and carbon dioxide

The necropsy (postmortem analysis) of a freshwater fish that died after being placed accidentally in saltwater would likely show that

loss of water by osmosis from cells in vital organs resulted in cell death and organ failure

The contraction of skeletal muscles is based on _____.

myosin cross-bridges binding to actin and transitioning from a high-energy to a low-energy state

Marine cone snails from the genus Conus are estimated to consist of up to 700 species. These predatory molluscs have devised an efficient venom apparatus that allows them to successfully capture polychaete worms, other molluscs, or in some cases fish as their primary food sources. ... conotoxins from Australian species of Conus ... have the capacity to inhibit specifically the nicotinic acetylcholine receptors in higher animals." (B. G. Livett, K. R. Gayler, and Z. Khalil. 2004. Drugs from the sea: Conopeptides as potential therapeutics. Current Medicinal Chemistry 11:1715-23.) 54) Refer to the paragraph above on the venom of marine core snails. This particular conotoxin inhibits acetylcholine receptors that are located _____.

on the postsynaptic membrane, on the muscle cell

The "motor unit" in vertebrate skeletal muscle refers to _____.

one motor neuron and all of the muscle fibers on which it has synapses

Most of the ATP supplies for a skeletal muscle undergoing one hour of sustained exercise come from _____.

oxidative phosphorylation

After blood flow is artificially reduced at one kidney, you would expect that kidney to secrete more of the hormone known as _____.

renin

Osmoregulatory adjustment via the renin-angiotensin-aldosterone system can be triggered by

severe sweating on a hot day

Although the membrane of a "resting" neuron is highly permeable to potassium ions, its membrane potential does not exactly match the equilibrium potential for potassium because the neuronal membrane is also _____.

slightly permeable to sodium ions

The operation of the sodium-potassium "pump" moves _____.

sodium ions out of the cell and potassium ions into the cell

Increased antidiuretic hormone (ADH) secretion is likely after

sweating-induced dehydration increases plasma osmolarity

The force driving simple diffusion is _____, while the energy source for active transport is

the concentration gradient; ATP

What is the function of the osmotic gradient found in the kidney? The osmotic gradient allows for _____.

the precise control of the retention of water and electrolytes

Urea is

the primary nitrogenous waste product of humans

A primary reason that the kidneys have one of the highest metabolic rates of all body organs is that _____.

they operate an extensive set of active-transport ion pumps

21) Which nitrogenous waste has the greatest number of nitrogen atoms?

uric acid