Bio 173 Exam 3 Study Questions 6 & 7

Which of the following require an animal to expend energy: Maintenance of cell resting potentials Generation of action potential in electrically excitable cell with resting potential already established Regeneration of resting potential after action potential Sequestration of neurotransmitter from synaptic cleft back into membrane-bound vesicles of the presynaptic neuron Diffusion of sodium into a cell with a normal resting membrane potential

- Maintenance of cell resting potentials - Regeneration of resting potential after action potential Sequestration of neurotransmitter from synaptic cleft back into membrane-bound vesicles of the presynaptic neuron

Describe the steps that take place in the muscle fiber to generate a contraction.

-Action potential travels down motor neuron axon -Voltage gated Ca++ channels open -Ca++ stimulates release of acetylcholine from vesicles into synaptic cleft -Acetylcholine binds receptors, opens Na+ channels -Voltage gated Na+ channels open AP -Action potential travels along t-tubules through sarcoplasmic retiulum -Voltage gated Ca++ channels open -Ca++ binds to troponin, releasing actin binding sites -Myosin binds to actin, contracting muscle fiber

Explain two positive feedback loops involving the hormone oxytocin. Besides regulating milk release and labor in placental mammals, what other role does oxytocin play in mammals?

1.as a baby suckles its mother's nipple, this stimulates the nerves in the breast which communicate with the hypothalamus and secrete oxytocin into the bloodstream which therefor stimulates milk flow 2. Oxytocin also stimulates uterine contractions during labor which help move the baby down and out of the birth canal, as the baby pushes against the mother's cervix and then against tissues in the pelvic floor, this also stimulates oxytocin and contractions Oxytocin also plays a role in maternal behavior and social bonding.

Explain the two mechanisms of pH regulation we have discussed in class. What is the role of CO2 in each of these mechanisms.

1.pH sensors in the brain react to an abundance of CO2 which causes the body to pant to increase ventilation and decrease the acidity in the body which is caused by an overabundance of Co2 2.pH regulation in kidneys is caused by either protons or bicarbonate excreted in the distal tube The role of CO2 is the source of the increase in pH in both cases

Define hormones, and explain how hormonal communication and electrical communication differ in animals' bodies. Do plants use electrical communication?

A hormone is an organic chemical produced by one part of an organism and is transported to another part of the organism where it triggers a specific affect Hormonal communications are delivered from gland secretions whereas electrical communications are delivered by the central nervous system via neurons Plants do use electrical communication

Explain the role of antidiuretic hormone, aquaporins, the hypothalamus, posterior pituitary, and the collecting duct of the kidney in regulating osmolarity in mammals.

ADH is produced by the hypothalamus in the brain and stored in the posterior pituitary gland. Binds to receptors on cells in the collecting duct of the kidney and promotes reabsorption of water back into the circulation. ADH stimulates water absorption by catalyzing the insertion of water channels/ aquaporins into the membranes of kidney tubules. These channels transport solute free water through tubular cells back into the blood, leading to a decrease in plasma osmolarity and increase osmolarity of urine

For each of the following hormones, describe one major effect. State what gland or neuroendocrine organ produces the hormone, and state whether or not it is a tropic hormone and whether or not it is a neurohormone: ADH, oxytocin, growth hormone, glucagon, insulin, ecdysone, juvenile hormone.

ADH: regulates kidney function, produced by posterior pituitary gland, is a neurohormone Oxytocin: causes contraction of mammary gland which force milk from reservoirs in gland, produced by posterior pituitary gland, is a neurohormone Growth Hormone: stimulates growth through both tropic and non tropic effect, secreted by anterior pituitary, is a tropic hormone Glucagon: controls glucose levels in blood from dropping too low, produced by alpha cells in pancreas, is a tropic hormone Insulin: controls glucose levels in blood stream, produced by beta cells in pancreas, is a tropic hormone Ecdysone: controls molting and pupation, produced by prothoracic gland, neurohormone Juvenile hormone: regulates insect metamorphosis and reproduction, produced by corpus allatum, neurohormone

What is the role of each of the following in generating a muscle contraction: actin, myosin, tropomyosin, Ca++, sarcoplasmic reticulum, voltage-gated Ca++ channel, T-tubule, acetylcholine, motor neuron, ATP.

Actin:structural protein Myosin: motor protein, binds to actin, pulls toward center Tropomyosin: on the actin when cell is at rest, it covers the binding site Ca++: shifts tropomyosin and frees binding site Sarcoplasmic reticulum: regulates calcium concentration in cytosol Voltage gated Ca++ channel: specialized ion channel that opens or closes in response to changes in membrane potential T-tubule: come in and allow action potential to interact with sarcoplasmic reticulum Acetylcholine: neurotransmitter, binds to receptors and alters permeability Motor neuron: transmits signals from brain ATP: releases free energy to drive endergonic reacts

Define an action potential. How does the charge across the neuron's membrane change during an action potential? What is the role of Na+ in generating the action potential? Why is Na+ such a useful ion for this purpose (think about how the resting potential is maintained)?

Action potential is a short lasting event in which the electrical membrane potential of a cell rapidly rises and falls. Following a consistent trajectory, this occurs because of a rush of sodium. Neurons membrane potential increases. The rapid influx of sodium ions causes the polarity of the plasma membrane to reverse, and the ion channels to rapidly inactivate. This then helps to get back to resting potential.

Describe the steps at the motor plate that take place when a motor neuron stimulates a muscle fiber to contract.

Action potential travels down the motor neuron axon. Voltage gated Ca++ channels open. Ca++ stimulates release of acetylcholine from vesicles into synaptic clefts. Acetylcholine binds receptors, opens Na++ channels and action potential is generated.

Describe three functions of astrocytes, a type of glial cell. What is the function of the other glial cells (oligodendrocytes, and Schwann cells).

Astrocytes give structural support to the neuron, help regulate extracellular ion and neurotransmitter concentrations, and cause dilation of nearby blood vessels. And during development facilitate formation of tight junctions. Oligodendrocytes are a part of the central nervous system and produce insulating sheaths of axons. Shwann cells are part of the peripheral nervous system and form myelin sheaths

Why do electrical impulses travel down axons unidirectionally and not back up towards the axon hillock?

Because of the refractory period, sodium ion channels are blocked up toward the axon hillock so action potential cannot be generated.

Gout is a disease of the joints caused by build up of uric acid. Why might consuming a low protein diet reduce the severity of gout?

By consuming a low protein diet they would be reducing their uric acid levels, which is what causes the inflammation and pain. It would also decrease the nitrogen going into the body, which would lower the uric acid.

How do neurons integrate stimuli/information from multiple sources?

By electrical synapses direct movements of Na+ ions through gap junctions, or chemical synapses. Release of direct neurotransmitters opens or closes ligand gated ion channels. Release of indirect neurotransmitters causes ion channels to open or close due to intracellular signaling. Long term potentiation and depression through change in abundance of ion channels making neurons more or less responsive.

What causes release of Ca++ from the sarcoplasmic reticulum?

Ca++ binds to troponin, releasing actin binding sites so myosin binds to actin

Explain the role of Ca++ in contraction of a muscle fiber. Draw a diagram that includes the sarcoplasmic reticulum, actin, myosin, tropomyosin, and troponin. Indicate where Ca++ ions are when the muscle is relaxed and when it is contracting.

Ca++ stimulates release of acetylcholine from vesicles into synaptic clefts. Ca++ is stored in the sarcoplasmic reticulum.

Define and describe chloride epithelial cells. What functions do they serve in the gills of fish? Do they require energy for these functions?

Chloride epithelial cells regulate solute movement, and are essential components of osmotic regulation and metabolic waste disposal. In freshwater fish gills they excrete chloride and facilitate excretion of Na+ & ammonium. In saltwater fish gills they take up Cl- and Na+ from water against the gradient. Yes, it requires energy as in both instances it uses active transport.

What is the function of each of the following components of a neuron: dendrite, cell body, axon hillock, axon terminal, synapse?

Dendrite: pass information that is gathered from other neurons Cell body: production of proteins for dendrites and axons Axon hillock: initiates the propagation of the action potential down the axon, determines rate Axon terminal:have a role in ending nerve signals to different parts of the body, contain synapses where neurotransmitters are unconfined for communication purposes with other neurons Synapse: neuron communicates with the next neuron in the network

Define each of the following: epithelium, tight junction, osmolarity, hypoosmotic, hyperosmotic, aquaporin

Epithelium: tissue that covers surfaces therefore has one free surface. Functions as selective barrier and forms half of basement membranes Tight Junctions: a type of cell junction where the membranes of neighboring cells join to form a barrier to a larger molecule and water that pass between the cells. As a barrier, tight junctions help maintain the polarity of cells and the osmotic balance Osmolarity: The measure of solute concentration defined as the number of osmoles of solute per liter of solute Hypoosmotic: characterized by having lower osmotic pressure than a surrounding fluid under comparison Hyperosmotic: characterized by having higher osmotic pressure than a surrounding fluid under comparison Aquaporin: a membrane protein, specifically a transport protein, that is shaped like a channel to facilitate the passage of water through channel proteins

What THREE hormones (that we learned about in class) control blood glucose levels? What are the effects of each of these hormones?

Glucagon: promotes the breakdown and release of glucose by the liver Insulin: promotes the uptake of glucose by most body cells and the synthesis and storage of glycogen in the liver Growth Hormone: causes liver to release insulin like growth factors which directly stimulate bone and cartilage growth

How does the relative development of the circulatory system in flatworms, insects and mammals affect the structure & function of their excretory system?

Flatworms: gas exchange by direct diffusion across surface membranes is efficient for organisms less than 1mm in diameter Nephridium: tubule onto the exterior which acts as an organ of excretion or osmoregulation. It typically has ciliated or flagellated calls and absorptive walls, uses a lot of energy Insects: consists of a network of small tubes that carry oxygen to entire body for gas exchange via diffusion Malphigian tubules: function by collecting water and uric acid from the surrounding blood. Urine is then formed by a process of secretion and emptied into the rectum to be excreted from the insects body Mammals: inhale air into lungs, capillary gas exchange with air and blood Kidney: waste is filtered from the blood and collected as urine in each kidney. Urine leaves the kidneys by ureters, and collects in the bladder. The bladder can distend to store urine that eventually leaves through urethra.

Why is it particularly useful for freshwater animals to have a mechanism for filtration?

Freshwater animals are in a constant state of uptaking lots of water, so to regulate water concentrations effectively they must expel lots of water by generating and excreting lots of urine.

Define each of the following: gland, secretion, paracrine, endocrine, exocrine, pheromone, neurohormone, tropic hormone.

Gland: aggregation of cells specialized for secretion Secretion: the discharge of molecules synthesized by a cell Paracrine: secretions affecting neighboring cells Endocrine: secretions are released into blood Exocrine: secretions are released to the outside of the body, or into the gut, lumen of kidney, etc. Pheromone: exocrine secretions that are used to communicate with other individuals Neurohormone: produced by nervous system, act as hormone Tropic hormone: specifically stimulate release of other hormones

Several psychoactive drugs (for example selective serotonin reuptake inhibitors (SSRIs) used to treat depression) inhibit clearing of specific neurotransmitters from the synaptic gap by the presynaptic cell and other accessory cells. If such a drug acts on a fast, direct, excitatory neurotransmitter, how is this likely to affect the postsynaptic cell? How might the membrane potential of the postsynaptic cell change as a result?

If neurotransmitters are not cleared from synaptic gap, Na+ channels wouldn't open and action potential wouldn't be generated.

Why is osmoregulation energetically expensive? Think of an experiment you could perform to measure the cost of osmoregulation in an aquatic animal.

It is energetically expensive because it requires a lot of active transport to do different things, which requires a lot of energy. For example turning ammonia into urea or uric acid. You could compare a species of animal that lives in both freshwater and marine water and compare the osmoregulation/metabolism cost to the animal between the two different environments.

Why is the nose an osmoregulatory organ? Is it most effective in hot or cool conditions? Warm or dry conditions? Explain how the nose helps terrestrial mammals conserve water. How would its function be affected if it did not stick out away from the body.

It is osmoregulatory because incoming air is warmed and humidified which cools the nose and outgoing air is cooled and loses water, wetting the nose. Depends on the fact that cool air holds less water than warm air. Most effective in hot, warm conditions. It helps retain water because as the air is cooled it extracts water from it as we exhale keeping the water in. It would be less effective if it didn't stick away from the body.

What osmoregulatory problem would an albatross that rarely returned to land and lacked access to fresh water face?

It would have a high concentration of salt in its bloodstream, without taking in water to dilute it.

Does hyperpolarization make a neuron more or less likely to generate an action potential?

Less likely, depolarization is what helps generate an action potential

Define membrane potential. What is the role of each of the following in creating a resting membrane potential in cells: Na+, K+, sodium-potassium pump, ion channel, diffusion, Cl-. Does the maintenance of a cellular membrane potential require energy? Why or why not?

Membrane Potential: the potential difference between the interior of a cell and the interstitial fluid beyond the membrane Charged ions diffuse slowly across the membrane, and can't dissolve in lipid bilayer. This allows cells to maintain gradient, uses energy Resting potential is maintained by -Na+/K+ pump keeping more Na outside and more K inside -K+ diffuse out of cell through ion channels in response to concentration gradient -Loss of K+ ions leaves negative charge inside cell membrane, + charge outside

For each of the following, what is the motor protein and what is the structural protein: Movement of flagella Movement of cilia Contraction of muscle fiber

Movement of flagella Motor: dynein Structure: axoneme Movement of cilia Motor: dynein Structure: axoneme Contraction of muscle fiber Motor: myosin Structure: actin and myosin

What would be the effect of using a drug to block ligand-gated ion channels of the postsynaptic neuron at an electrical synapse?

Neurotransmitters bind to ligand gated ion channels. This drug would reduce this communication, and make it less likely to generate action potential.

Define osmoregulation in your own words, and explain the difference between osmotic regulators and conformers.

Osmoregulation is the regulation of osmotic pressure controlled by solute concentration and water. An osmotic regulator would depend on external factors in order to maintain osmolarity while a conformer would be able to maintain internal osmolarity regardless.

How would each of the following affect a muscle cell's ability to contract? Oubain, Tetrodotoxin, poison that prevents breakdown of acetylcholine within neuromusclular synapses

Ouabain: neuron couldn't generate action potential, or membrane resting potential. Will affect other cells in body Tetrodotoxin: prevents action potentials which are going to be generated, which will make the animal very sick and possibly die because the nervous system cannot function Poison that prevents breakdown of acetylcholine within neuromuscular synapses (motor plate): excitatory postsynaptic potential would not stop being produced because acetylcholine, while in exitatory state, produces this after binding with the ligand gated ion channel

Which two hormones are released by the posterior pituitary? Are they tropic hormones? Are they neurohormones?

Oxytocin and antidiuretic hormone (ADH) are released. Both of them are neurohormones.

Which of these 3 components of urine generation - filtration, secretion and reabsorption- are found in protonephridia? Which are found in malpighian tubules?

Protonephridia: Filtration: beating of cilia draws water and solutes from the interstitial fluid through the fame bulb, releasing into tubule network Secretion: balance the osmotic uptake of water from environment Malpighian tubules: Secretion: certain solutes (nitrogenous waste) from the hemolymph into the lumen of the tubule, then passes into rectum Reabsorption: from rectum, pumped back to hemolymph, water reabsorption by osmosis occurs

Diagram a mammalian juxtamedullary nephron and indicate the major function for each section

Proximal Tubules: uptake & secretion Distal Tubules: pH regulation Glomerulus & Bowman's capsule: filtration Loop of Henle descending: concentration due to water loss Loop of Henle ascending: thin: NaCl diffusion Loop of Henle thick: NaCl uptake

Describe the roles of the hormones thyroid-releasing hormone, thyroid stimulating hormone, and thyroxine. Which gland produces each of these? Which of these are neurohormones? Which of these are tropic hormones? Draw or describe the negative loop regulating production of thyroid hormone and the role of each of these hormones in that loop. What are some of the symptoms of thyroxine deficiency? What are some of the symptoms of excess thyroxine?

Released by the hypothalamus, when levels of thyroid hormone in the blood drops, thyroid releasing hormone (TRH) causes the anterior pituitary to secrete thyrotropin (thyroid stimulating hormone-TSH). The TSH then stimulates the thyroid gland to secrete thyroid hormone (thyroxine) to increase metabolic rate. All are tropic hormones. The negative feedback is when levels of T3 and T4 rise above a certain level T3 prevents TSH and T3 which prevents THE production. Symptoms of thyroxine deficiency: weight gain, increased sensitivity to cold, slowed heart rate and fatigue Symptoms of excess thyroxine: weight loss, increased sensitivity to heat, rapid heart rate and fatigue

What are the important sources and losses of salt for each of the following: saltwater fish, freshwater fish, human, kangaroo rat?

Saltwater fish: -Source: seawater -Loss: gills and urine Freshwater fish: -Source: uptake through gills -Loss: excretes through gills Human -Source: food -Loss: through urine Kangaroo rat -Source: ingests in good -Loss: excretes through urine

What are the important sources and losses of water for each of the following: saltwater fish, freshwater fish, human, kangaroo rat?

Saltwater fish: tend to lose water and gain salts -Source: food and drinking -Loss: gills (osmosis) & urine Freshwater fish: tend to gain water and lose salts -Source: food and gills (osmosis) -Loss: urine Human -Source: food and mostly drinking -Loss: evaporation (sweat), urine, feces Kangaroo rat -Source: mostly metabolism and food -Loss: evaporation, urine, feces

Explain how tetrodotoxin, which blocks voltage-gated Na+ channels, and ouabain, which disables the Na+/K+ pump would each affect the function of an isolated neuron. What would likely be the effect of each of these toxins on a whole, living animal?

Tetrodotoxin would cause neurons to not be able to generate action potential. So they won't be able to send any kind of electrical signals. Ouabain would paralyze the animal, causing cells to not maintain resting potential so they can't integrate information, using neurons' electrical impulses.

What would be the consequence of a poison that prevented voltage-gated sodium channels to experience a refractory period after opening?

The Na+ channels would stay open

How does Ca++ get back into the sarcoplasmic reticulum?

The action potential tracks along t-tubules through sarcoplasmic reticulum, voltage gated Ca++ channels open.

Why is osmoregulation particularly challenging for vampire bats? How do they adjust their osmoregulation to cope with these challenges?

The bat will either produce very dilute or very concentrated urine, making the bats reduce their body weight rapidly or digest large amounts of protein while conserving water. The ADH increases water reabsorption in the distal tubules and collects ducts of the kidney.

On your diagram of the nephron, add the capillaries that flow along the loop of Henle. Indicate the direction of fluid in these capillaries as well as the nephron. Draw arrows to indicate flows of water among the Loop of Henle, renal medulla, and associated capillaries. What would happen if the flows in these tubes were arranged as a concurrent rather than a countercurrent system.

The countercurrent system expends energy to actively transport NaCl from the upper part of the ascending loop. It expends energy to the concentration gradient. If it was a concurrent system then they would not be taken off the gradient and would not filtrate.

What is the function of the lymph system in mammalian circulation?

The function of the lymphatic system is to return interstitial fluid to the circulatory system, transport fats from food, transport hormones, and plays a role in the immune system.

Explain how gas exchange and osmoregulation are linked in aquatic animals that are not osmoconformers. For example, will the energy required for osmoregulation increase or decrease during exercise for a marine bony fish?

The gills provide for gas exchange and osmoregulation, they excrete salt ions, CO2 and water. The energy required for osmoregulation will decrease during exercise because the muscles contracting and relaxing will promote blood flow, promoting gas exchange and osmoregulation.

In the disease multiple sclerosis, the body's immune system attacks myelin around nerves. Why does loss of myelin disrupt nerve function?

The myelin sheath serves as an insulator and means of conduction. The myelin makes the diameter bigger which makes for faster conduction. When it degrades conduction signals along nerves can be impaired or lost, and nerve withers.

The kidney is responsible for generating a concentration gradient within the body- production of urine that is (usually) hyperosmotic to body fluids (although sometimes it produces the energetic cost of urine concentration. Specifically what conditions are maintained in the medulla of the kidney, and how? How do countercurrents in capillaries through the medulla facilitate urine concentrations.

The structure of the juxtamedullary nephron helps to reduce energy costs in the kidney. The loop structures in the loop of Henle run alongside a flow of capillaries in the opposite direction. This allows one loop to pick up fluid as the loop of Henle loses fluid, working so this part of the kidney can reabsorb water and sodium chloride from the filtrate. This conserves water for the organism, producing highly concentrated urine. In the medulla, high osmolarity is maintained. Maintained because the salt and urea diffuse out of the urine into that area. Countercurrent flow causes the capillaries to draw out water, which assures no dilation in medulla

How do animals without bones or other hard parts generate movement? What is a hydrostatic skeleton? Give an example of an animal with a hydrostatic skeleton.

These animals generate movement with muscle. Hydrostatic skeleton is a stricture of a soft bodied animals consisting of fluid filled cavity surrounded by muscles Ex: earthworm

Organophosphate pesticides interfere with removal of acetylcholine from synaptic clefts through inhibiting the enzyme acetylcholinesterase. How would this affect the postsynaptic neuron? This chemical is used primarily to kill insects on farm fields. Would you expect it to be specific to insects or to be toxic to humans as well?

This would cause a build up making the organism's muscles contract more. And it is both toxic to insects and humans, it may not show short term effects but it will cause long term effects due to being stored in organism fat.

African lungfish, which are often found in small stagnant pools of freshwater, produce nitrogenous waste as urea. What is the advantage of this adaptation compared to releasing nitrogenous waste as ammonium, which most fish do?

Urea is a more concentrated form of nitrogenous waste, which allows for more effective water conservation. But, since they don't have the volume in the small pools to dilute the ammonia they do better releasing as urea.

How do voltage-gated Na+ and K+ channels respond to changes in membrane potential during an action potential? How do they contribute to the depolarization of the membrane during the action potential and the restoration of the resting potential afterward?

Voltage gated ion channels are shut when the membrane potential is near the resting potential of the cell, but they rapidly begin to open if the membrane potential increases to a precisely defined threshold value. When the channels open Na+ flows in, which changes the electrochemical gradient, membrane potential rises. More Na+ channels open, producing a greater electric current across the cell membrane. Then all channels open, Na+ floods in, resulting in a large upswing in membrane potential. Causes the polarity of the plasma membrane to reverse, and the ion channels then rapidly activate. Sodium channels close, sodium ions can no longer enter the neuron. K+ channels are activated and K+ leaves return the electrochemical gradient to the resting state. Refractory period occurs, due to additional K currents. Mechanisms that prevent an action potential from traveling back the way it came

Which of the following require animals to use energy: Excretion of hyperosmotic urine Excretion of hypoosmotic urine Diffusion of ammonia across gill of fish Uptake of salt by gills of freshwater fish Excretion of salt by gills of saltwater fish Conversion of ammonia to urea in mammals Conversion of ammonia to uric acid in insects, reptiles and birds Secretion of salts and wastes in Malpighian tubules of insects Diffusion of water in Malpighian tubules of insects Filtration by protonephridia of a flatworm

Which of the following require animals to use energy: Excretion of hyperosmotic urine requires energy Excretion of hypoosmotic urine Diffusion of ammonia across gill of fish Uptake of salt by gills of freshwater fish requires energy Excretion of salt by gills of saltwater fish requires energy Conversion of ammonia to urea in mammals Conversion of ammonia to uric acid in insects, reptiles and birds requires energy Secretion of salts and wastes in Malpighian tubules of insects Diffusion of water in Malpighian tubules of insects Filtration by protonephridia of a flatworm requires energy

Which of the following would transmit electrical impulses most rapidly: a. narrow, unmyelinated neuron b. wide, unmyelinated neuron c. narrow, myelinated neuron d. wide, myelinated neuron

d. wide, myelinated neuron

What conditions are controlled by osmoregulation?

pH, water concentration, salt concentrations, nitrogenous waste concentrations