Class 8: Endocrine, Cardiovascular, Immunology

Cardiac autorhythmic cells (and to some extent cardiac muscle cells) have the ability to trigger their own action potential independent of any neural input or other stimulation. Which of the following is responsible for this autorhythmic property? A. K+ leak channels B. Na+ leak channels C. Na+/K+ ATPase D. Slow voltage-gated Na+ channels

B. Na+ leak channels Cardiac autorhythmic cells contain Na+ leak channels that allow Na+ to enter the cell according to its gradient. As Na+ enters, the cell potential rises (depolarizes) until it reaches the threshold for slow voltage-gated Na+channels; this triggers the action potential itself (choice D is wrong). K+ leak channels allow K+ to leave the cell, making it more negative (hyperpolarizing it) and less likely to fire an action potential (choice A is wrong). The Na+/K+ ATPase establishes the Na+ and K+ gradients necessary for heart function, but do not themselves trigger action potentials (choice C is wrong).

Voltage-gated sodium channels inactivate via a "ball-and-chain" mechanism, where a peptide "ball" tethered to the channel blocks the channel, preventing sodium influx. Increasing the length of the tether on the inactivation peptide increases the time required for inactivation. Which of the following would be observed? A. Decreased time required between action potentials B. Decreased maximal rate (frequency) of firing C. Increased maximal sodium conductance rate D. Increased maximal rate (frequency) of firing

B. Decreased maximal rate (frequency) of firing B. Increased time required for inactivation would result in a lengthened absolute refractory period which could decrease the maximal rate, or frequency, of firing (choice B is correct and choices A and D are wrong). Increasing the time required for inactivation would not alter the maximal sodium conductance rate (choice C is wrong). Note that answer choices A and D are identical and both cannot be correct.

A patient presents with an accelerated heart rate, excessive sweating, and heat intolerance. He is subsequently diagnosed with acute toxicity of an iodide-containing hormone present in a weight-loss supplement he recently began taking. Which of the following lab results matches the described scenario? A. Increased T4 (thyroid hormone), increased TSH B. Increased T4 (thyroid hormone), decreased TSH C. Decreased T4 (thyroid hormone), increased TSH D. Decreased T4 (thyroid hormone), decreased TSH

B. Increased T4 (thyroid hormone), decreased TSH B. This patient is suffering from acute thyroid hormone toxicity and is experiencing symptoms of hyperthyroidism including accelerated heart rate, excessive sweating, and heat intolerance. The elevated levels of T4 (choices C and D are wrong) will result in feedback to the hypothalamus and anterior pituitary, causing a decrease in TSH (choice B is correct and choice A is wrong). Note that these symptoms could also be explained if the patient were ingesting TSH, however the stem of the question informs us that the substance being ingested contained iodide, indicating he was consuming thyroid hormone directly.

Follicle stimulating hormone (FSH) and luteinizing hormone (LH) have what comparable effect in both males and females? A. FSH and LH directly contribute to the development of secondary sex characteristics in both sexes. B. FSH and LH feed back to the testes and ovaries to downregulate testosterone and estrogen release in males and females, respectively. C. Both FSH and LH are involved in oogenesis, spermatogenesis, and the secretion of sex steroids. D. Both FSH and LH directly trigger the formation of external genitalia in fetuses of either sex.

C. Both FSH and LH are involved in oogenesis, spermatogenesis, and the secretion of sex steroids. FSH stimulates the development of ovarian follicles and estrogen release, and LH triggers ovulation and progesterone release, making them a part of oogenesis and sex steroid secretion. They are also responsible for stimulating sperm production and testosterone secretion in the testes. However, these hormones do not directly affect the formation of external genitalia or secondary sex traits, and it is testosterone and estrogen that feed back to the pituitary to down regulate the release of FSH and LH, not the other way around.

The major cell type involved in the humoral immune response is the: A. killer T cell. B. erythrocyte. C. macrophage. D. B cell.

D. B cell. The "humoral immune response" refers to the production and secretion of antibodies by B cells when stimulated by antigen and by helper T cells. Killer T cells are involved in the cell-mediated immune response and macrophages are involved in both non-specific phagocytosis as well as phagocytosis of structures tagged for destruction by antibodies (note that this is related to the humoral immune response, but the macrophage is not the major cell type involved). Erythrocytes are red blood cells and do not participate in immunity.

An infant born with a congenital defect in the ventricular septum that causes a mixing of blood between the right and left ventricles is most likely to suffer from: I. poor tissue oxygenation. II. increased blood pressure in the pulmonary circuit. III. higher blood pH.

- I and II only Item I is true: If blood between the left and right ventricles is mixed, then some deoxygenated blood from the right ventricle will mix with oxygenated blood from the left ventricle and be returned to the body. This blood, with its lower-than-normal level of oxygenation, will result in poorer tissue oxygenation. Item II is true: The left ventricle generates higher pressures than the right ventricle. If the two ventricles are essentially connected via a defect in the septum, the higher pressures from the left ventricle will translate to the right ventricle and into the pulmonary circuit. Item III is false: If blood from the right ventricle (on its way to the lungs) mixes with blood from the left ventricle (on its way to the body), the blood from the right ventricle never makes it to the lungs to get rid of its carbon dioxide (or pick up oxygen, this again is why Statement I is true). The blood with have a higher overall CO2content, and therefore a lower pH.

An increase in heart rate will have what effect on cardiac output and blood pressure? A. Increase cardiac output and increase blood pressure. B. Increase cardiac output and decrease blood pressure C. Decrease cardiac output and increase blood pressure D. Decrease cardiac output and decrease blood pressure

A. Increase cardiac output and increase blood pressure. A. Cardiac output is the volume of blood pumped out of the heart in one minute, and is the product of the stroke volume (volume pumped in one beat) and the heart rate (beats per minute). Increases in either of these two values will increase cardiac output (choices C and D are wrong). Cardiac output and blood pressure are directly proportional; if cardiac output increases, blood pressure will increase (choice A is correct and choice B is wrong).

Helper T-cells can be distinguished from cytotoxic T-cells in that: I. helper T cells recognize antigen complexed with MHC II. II. cytotoxic T cells recognize antigen complexed with MHC I. III. cytotoxic T cells stimulate the B cell immune response.

- I and II only Item I is true: helper T cells recognize antigen presented on MHC II (choice "II and III only" can be eliminated). Item II is also true: cytotoxic T cells recognize antigen presented on MHC I (choice "I only" can be eliminated). Item III is false: it is the helper T cells that stimulate the B cell response (choice "I, II, and III" can be eliminated).

POMC is a precursor peptide generated in the anterior pituitary gland that is subject to proteolytic cleavage to generate several functional hormone derivatives. Which of the following pairs of hormones are likely derived from POMC? A. ACTH and MSH B. ACTH and oxytocin C. TSH and ADH D. FSH and ADH

A. ACTH and MSH A. The pituitary gland, a commonly discussed endocrine gland, is responsible for producing numerous hormones including FSH, LH, ACTH, TSH, prolactin, GH, and MSH (choice A is correct). ADH and oxytocin are produced in the hypothalamus (choices B, C, and D are not correct). Note: to answer this question, you must know that ACTH is produced in the anterior pituitary and that oxytocin and ADH are not.

Which of the following is involved in both innate (non-specific) and specific immunity? A. Macrophages B. MHC I C. Memory cells D. Lysozyme

A. Macrophages Macrophages can act as non-specific phagocytes as well as specific phagocytes for antibody-coated antigen. Memory cells and MHC I are involved only in specific immunity, and lysozyme is involved in non-specific defense only (non-specific antibacterial enzyme).

Which of the following represents the correct order of structures through which a red blood cell, starting in the lungs, would travel? A. Pulmonary veins -> left atrium -> bicuspid valve -> left ventricle -> aorta B. Pulmonary veins -> left atrium -> tricuspid valve -> left ventricle -> aorta C. Pulmonary arteries -> left atrium -> bicuspid valve -> left ventricle -> aorta D. Pulmonary arteries -> left atrium tricuspid valve -> left ventricle -> aorta

A. Pulmonary veins -> left atrium -> bicuspid valve -> left ventricle -> aorta A. Pulmonary veins carry the blood from the lungs back to the heart (choices C and D can be eliminated). The bicuspid valve is found on the left side of the heart, and the tricuspid valve is on the right (choice B can be eliminated and choice A is correct).

Which of the following is involved in the body's first line of defense against infection? A. Several nonspecific antimicrobial chemicals such as acids B. Several nonspecific T cells C. Several nonspecific antibodies D. Several nonspecific B cells

A. Several nonspecific antimicrobial chemicals such as acids Antimicrobial chemicals such as acids, lysozyme, etc. are non-specific and help with the first line of defense against infection. Antibodies, B cells and T cells are all involved in specific immunity and are not part of the first (non-specific) line of defense.

All of the following hormones are released by the anterior pituitary gland EXCEPT: A. ACTH. B. ADH. C. growth hormone. D. prolactin.

B. ADH. Prolactin, growth hormone, and ACTH are from the anterior pituitary, but ADH is from the posterior pituitary.

Which of the following blood components is responsible for coagulation? A. Leukocytes B. Platelets C. Erythrocytes D. Lymphocytes

B. Platelets Platelets are small pieces of large cells called megakaryocytes. When a wound occurs, platelets can be activated to stick to the edge of the wound site and release their contents, stimulating the clotting reaction.

How are steroid hormones stored in cells? A. Steroid hormones are stored in vesicles. B. Steroid hormones are not stored; they are synthesized as needed. C. Steroid hormones are stored in lysosomes. D. Steroid hormones are stored in the smooth endoplasmic reticulum.

B. Steroid hormones are not stored; they are synthesized as needed.

A bipolar neuron could be composed of which of the following? A. A neuron with a soma and a single dendrite B. A neuron with a soma and a single axon C. A neuron with a soma, a single dendrite, and a single axon D. A neuron with a soma, multiple dendrites, and a single axon

C. A neuron with a soma, a single dendrite, and a single axon Bipolar neurons possess two extensions from the cell body (or soma); one dendrite and one axon (choice C is correct). Unipolar neurons possess only a single extension from the cell body (choices A and B are wrong), while multipolar neurons have multiple dendrites (or a dendritic arbor) extending from the cell body, but only a single axon (choice D is wrong).

A professional body builder purchases recombinant HGH (human growth hormone) online and proceeds to mix it into a morning energy shake each day. After four months, he still is not seeing the results he wanted. What was the likely cause in the failure of the body builder to build more muscle? A. HGH does not increase muscle mass. B. HGH cannot enter the cell to bind to its intracellular receptor. C. Increased levels of the functional hormone have not been achieved in the blood. D. Steroid hormones cannot be administered orally.

C. Increased levels of the functional hormone have not been achieved in the blood. C. The body builder is attempting to use human growth hormone to increase muscle mass by taking the hormone orally. Growth hormone, which is produced in the pituitary gland, is a peptide hormone that binds to extracellular receptors (choices B and D are wrong) and would be subject to degradation in the stomach and small intestine. This degradation could explain the observed lack of effect as the hormone is not absorbed in a functional form (choice C is correct). Growth hormone has numerous effects including increasing height in children/adolescents, increasing calcium retention, and increasing muscle mass (choice A is not correct).

Where in the heart does its electrical signal originate? A. Atrioventricular node B. Left atrium C. Sinoatrial node D. Coronary sinus

C. Sinoatrial node

Which of the following is not a component of the Bohr effect? A. Low serum pH B. High serum PCO2 C. High metabolic rate D. High serum PO2

D. High serum PO2 The Bohr effect states that hemoglobin's affinity for oxygen is inversely proportional to the acidity of the blood, the concentration of carbon dioxide within the blood and the metabolic rate of the tissues in question. For example, when serum pH is low or serum PCO2 is high (findings seen in metabolically active tissues) hemoglobin will have a low affinity for oxygen. High serum PO2 would not be expected in the vicinity of highly metabolically active tissues, as these tissues would be consuming all available oxygen and generating high levels of CO2.

If a woman has been walking through the desert all day without food or water, what hormones will most likely be found in elevated levels in her blood? I. Vasopressin II. Aldosterone III. Insulin

- I and II only Items I and II are true: The woman will be dehydrated, with low extracellular fluid volume. Vasopressin (ADH) and aldosterone both help to prevent water loss in urine. Item III is false: Since she has not eaten, her plasma glucose is likely to be low and, thus, her insulin as well, since insulin is stimulated by high glucose to increase glucose uptake.

Which of the following occurs in response to low blood pressure? I. Increased blood osmolarity due to aldosterone release from the pituitary gland II. Increased water retention due to ADH release from the pituitary gland III. Systemic vasoconstriction

- II and III only Item I is false: In response to low blood pressure, angiotensin II stimulates aldosterone release from the adrenal cortex, not the pituitary gland (I and II and I, II and III can be eliminated). Item II is true: The increased blood osmolarity due to aldosterone release leads to ADH release from the posterior pituitary and subsequent water retention (III only can be eliminated). Item III is also true: Angiotensin II causes systemic vasoconstriction.

Which of the following is/are true about the relationship between heart contractions and the autonomic nervous system? I. The heart requires signals from the sympathetic nervous system in order to contract. II. The vagus nerve releases acetylcholine and slows the heart rate. III. The heart is capable of contracting in the complete absence of nervous system input.

- II and III only Item I is false: the heart does not require input by the sympathetic nervous system in order to contract, it has its own pacemaker in the SA node (choices including Item I can be eliminated). Note that Item II is in both of the remaining answer choices so it must be true, and only Item III needs to be evaluated. Item III is true: The heart has its own pacemaker system in the SA node (autorhythmic cells), so it is capable of operating without any nervous system input. (Note that Item II is also true: the vagus nerve is a parasympathetic nerve; it uses acetylcholine as its neurotransmitter and reduces the heart rate.)

A 24-year-old female is diagnosed with a tumor in the adrenal cortex that is hypersecreting hormones. Which of the following symptoms could be expected in this woman? I. Elevated blood pressure II. Decreased levels of ACTH III. Facial hair growth

- all of them Item I is true: the primary hormones of the adrenal cortex include cortisol, aldosterone, and sex steroids. Increased aldosterone levels would increase the amount of Na+reabsorbed at the kidneys; this would increase the osmolarity of the blood, promote the retention of water, and increase blood pressure ("II and III only" can be eliminated). Item II is true: increased cortisol levels due to the tumor would feed back to the anterior pituitary and hypothalamus to decrease the secretion of ACTH ("I only" can be eliminated). Item III is true: increased levels of sex steroids would have a masculinizing effect on a woman; the increased levels of testosterone would promote male secondary sex characteristics including facial hair growth ("I and II only" can be eliminated).

Which of the following vessels carry oxygen-rich blood? I. Aorta II. Umbilical vein III. Pulmonary vein

- all of them The aorta carries oxygenated blood from the left ventricle into the systemic circulation (Item I is true). The umbilical vein returns oxygenated blood from the placenta to the fetal heart (Item II is true). The pulmonary veins return oxygenated blood from the lungs to the left atrium (Item III is true). Note that the terms "artery" and "vein" only denote direction of flow and not oxygen content; arteries always carry blood away from the heart and veins carry blood toward the heart.

Which of the following methods does carbon dioxide employ in order to be transported through the blood? I. Converted into bicarbonate and dissolved in the plasma II. Directly dissolved in the plasma III. Bound to hemoglobin

- all of them Item I is true: the majority of carbon dioxide in the blood (about 73%) is found as bicarbonate ion. Carbon dioxide and water combine to form carbonic acid (H2CO3), which then dissociates into H+ and bicarbonate (HCO3-, choice B can be eliminated). Item II is true: some carbon dioxide, about 7%, dissolves directly in the plasma (choices A and C can be eliminated and choice D is correct). Item III is true: about 20% of the carbon dioxide in the blood is bound to hemoglobin to form carbaminohemoglobin.

By which of the following mechanisms is the release of insulin primarily controlled? A. Humoral B. Hormonal C. Neural D. Mechanical

A. Humoral The release of insulin is controlled primarily by the presence or absence of glucose in the blood plasma (humorally). There is limited control of insulin release by the autonomic nervous system at the onset of food ingestion, but this is not the primary means by which the release of insulin is controlled. The release of insulin is not controlled via mechanical processes, nor is it controlled by another hormone (a tropic hormone).

Which of the following neurotransmitters stimulates autonomic postganglionic neurons? A. Acetylcholine B. Norepinephrine C. Epinephrine D. Serotonin

A. Acetylcholine A. Acetylcholine is used as the neurotransmitter at the ganglia in both the sympathetic and parasympathetic divisions of the autonomic nervous system (choice A is correct). The sympathetic division then utilizes norepinephrine at its effector organs (choice B is wrong) and the parasympathetic division continues to use acetylcholine. Epinephrine is a hormone; its release is triggered by activation of the sympathetic nervous system and it can stimulate similar receptors as norepinephrine (choice C is wrong). Serotonin is a neurotransmitter used in the brain; it is not found at autonomic ganglia (choice D is wrong).

Macrophages express both classes of MHC molecules (type I and type II) on their plasma membranes. Upon infection of a macrophage with adenovirus, a viral protein is generated that binds specifically to MHC type 1 molecules. As a result, these MHC molecules are retained in the endoplasmic reticulum and not transported to the plasma membrane. Which of the following is the most likely consequence of adenoviral infection? A. Decreased likelihood of cytotoxic T-cell destruction of an infected macrophage B. Increased ability of an infected macrophage to generate and secrete antibodies C. Increased ability of an infected macrophage to process and present antigen to cytotoxic T-cells D. Decreased ability of an infected macrophage to internalize, process, and present extracellular antigen to helper T-cells

A. Decreased likelihood of cytotoxic T-cell destruction of an infected macrophage Any cell infected with a virus will process viral antigens and present them in the context of an MHC type I molecule on the cell surface. Cytotoxic T cells will recognize "non-self" viral antigen complexed with "self" MHC type I and will destroy the cell. If the infected macrophage's MHC type I molecules are prevented from moving to the cell surface by the virus, the macrophage cannot communicate its state of infection to cytotoxic T cells and will be spared ("decreased likelihood of cytotoxic T-cell destruction of an infected macrophage" is correct and "increased ability of an infected macrophage to process and present antigen to cytotoxic T-cells" is wrong; note that this is beneficial for the virus!). Macrophages do not secrete antibodies, activated B cells do ("increased ability of an infected macrophage to generate and secrete antibodies" is wrong). It is a macrophage's MHC type II that is involved in presenting internalized antigen to helper T cells. Since adenovirus infection affects MHC I function, there should be no problem with MHC II function ("decreased ability of an infected macrophage to internalize, process, and present extracellular antigen to helper T-cells" is wrong).

Coarctation of the aorta, a congenital defect in which the aorta is narrowed, would cause which of the following if left untreated? A. Decreased pressure in the lower limbs B. Decreased pressure in the pulmonic circuit C. Increased pulse pressure D. Decreased venous valve function

A. Decreased pressure in the lower limbs Since the aorta is the first vessel to receive fully pressurized blood in the systemic circuit, if it was narrowed, blood flow (and thus pressure) would be reduced to the rest of the body. The narrowed vessel would have an increased resistance, backing up blood and increasing pressures prior to that vessel (such as the pulmonic circuit). Pulse pressure is the difference between the systolic pressure and the diastolic pressure, and since all systemic blood pressure is decreased, pulse pressure would also be decreased. There is no reason to assume an impairment of the venous valves.

Action potentials can involve voltage-gated calcium channels. Intracellular Ca2+ concentration is typically several fold below extracellular Ca2+ concentration. In which of the following processes might calcium play a role? A. Depolarization B. Repolarization C. Polarization D. Hyperpolarization

A. Depolarization A. From the stem of the question, voltage-gated calcium channels are similar to voltage-gated sodium channels. When membrane potential reaches the threshold for a voltage-gated channel, the channel opens. In this case, calcium would flow into the cell (down its concentration gradient) causing membrane potential to move in the positive direction, i.e., depolarization (choice A is correct). Repolarization is a return to rest potential (choice B is wrong) and hyperpolarization is a movement from rest potential to more negative values (choice D is wrong). Polarization simply describes the cell at rest potential, i.e., negative inside with respect to the outside (choice C is wrong).

Which of the following hormones increases blood glucose and is released from the pancreatic islets of Langerhans? A. Glucagon B. Insulin C. Epinephrine D. Cortisol

A. Glucagon A. Glucagon is made by the α cells within the islets of Langerhans and stimulates the breakdown of glycogen stores in the liver to increase circulating glucose levels (choice A is correct). Insulin is made by the β cells of the pancreas, but it decreases the circulating levels of glucose (choice B is wrong). Epinephrine and cortisol both increase glucose, but they are released by the adrenal medulla and adrenal cortex, respectively (choices C and D are wrong).

A woman with blood type A+ has four children. The blood types of her children are O+, AB-, A+, and AB+. Which of the following statements is true? A. Her husband cannot have type AB blood. B. Her husband must have type B- blood. C. Her husband is homozygous for the IB allele. D. Her husband must be heterozygous for the Rh allele.

A. Her husband cannot have type AB blood. A. In order to produce children with blood type O, both parents must donate a recessive i allele, thus the husband cannot have type AB blood (choice A is true), and he cannot be homozygous for IB (choice C is wrong). In order to produce children that are Rh-, both parents must donate the recessive r allele. Since she is A+, then she must be heterozygous for the Rh factor (Rr), but the husband could be Rh- (homozygous recessive rr) or Rh+ and heterozygous (Rr, choices B and D are wrong).

Which of the following features is NOT characteristic of polypeptide hormone activity? A. Hormones pass through the target cell membrane and enter the nucleus. B. Target organ is often distant from site of release. C. Transmission is via blood circulation. D. Cellular effects often require protein kinase activity.

A. Hormones pass through the target cell membrane and enter the nucleus. Polypeptide hormones are large and hydrophilic and therefore cannot pass through a cell membrane, so that statement is false and thus the correct response here. "Transmission is via blood circulation" and "target organ is often distant from site of release" are true of all hormones, and "cellular effects often require protein kinase activity" is true of polypeptide hormones.

Conn syndrome is characterized by the overproduction of aldosterone by the adrenal glands. In most cases, the syndrome is due to the presence of an aldosterone-secreting adrenal adenoma (a benign tumor). A patient with Conn syndrome is most likely to experience which of the following symptoms? A. Hypertension resulting from increased reabsorption of Na+ at the distal convoluted tubule. B. Hypertension resulting from increased ACTH secretion by the anterior pituitary gland. C. Hypotension resulting from increased water reabsorption at the distal convoluted tubule. D. Hypertension resulting from increased renin secretion by the juxtaglomerular apparatus.

A. Hypertension resulting from increased reabsorption of Na+ at the distal convoluted tubule. Aldosterone leads to increased reabsorption of Na+ and water at the distal convoluted tubule; this would increase blood volume and pressure. Renin and ACTH ultimately result in aldosterone secretion, not the other way around.

Which of the following statements is true about oxytocin? A. It is released from the posterior pituitary and one of its functions is to induce uterine contractions during labor. B. It is released from the anterior pituitary and one of its functions is to induce uterine contractions during labor. C. It is released from the posterior pituitary and one of its functions is to induce milk production and ejection during lactation. D. It is released from the anterior pituitary and one of its functions is to induce milk production and ejection during lactation.

A. It is released from the posterior pituitary and one of its functions is to induce uterine contractions during labor. Oxytocin is released from the posterior pituitary (choices B and D are wrong), and its functions include inducing uterine contractions during labor (choice A is correct) and milk ejection during lactation. The actual production of milk is triggered by prolactin (choice C is wrong).

Which of the following features of the skin should NOT be classified as part of the body's innate immune system? A. Langerhans cells located in the epidermis and dermis serve as antigen presenting cells, causing the clonal expansion of T cells. B. The skin acts as a physical barrier that blocks the entry of microbes. C. Sweat and sebaceous glands secretions include substances that slow the growth of bacteria. D. Healthy skin hosts populations of benign bacteria that compete with potentially disease-causing bacteria for space and nutrients.

A. Langerhans cells located in the epidermis and dermis serve as antigen presenting cells, causing the clonal expansion of T cells. "Innate immunity" is relatively non-specific protection against pathogens and antigens. It includes barriers, (like the skin and mucus), non-specific antibacterial enzymes (like lysozyme in sweat and tears), symbiotic relationships with benign bacteria (like skin and colonic flora), non-specific phagocytosis (macrophages and neutrophils), and the complement system. This constitutes a valuable first-line of defense. Specific (adaptive acquired) immunity involves antigen specificity and memory. B cells produce antibodies against specific antigen that marks the antigen for destruction. Antigen is presented to T-cells via MHC I or II to trigger cytotoxic activity or clonal expansion. Of the answer choices, the interactions between Langerhans cells and T cells meet these criteria.

Damage to which chamber of the heart would be most evident in the measurement of systolic blood pressure by a standard sphygmomanometer? A. Left ventricle B. Right atrium C. Left atrium D. Right ventricle

A. Left ventricle Damage to the left ventricle would be most evident in the measurement of systolic blood pressure by a standard sphygmomanometer. A sphygmomanometer, or blood pressure cuff, measures systemic arterial pressure. Systolic blood pressure is measured during the contraction of the ventricles, and diastolic blood pressure is measured during relaxation. The left side of the heart is responsible for systemic circulation while the right side is responsible for pulmonic circulation, and specifically, the left ventricle provides the force for blood to be propelled from the heart into the systemic circulatory system. If this chamber were damaged and not providing the same amount of force, the difference would be seen in standard systolic blood pressure measurements. Changes to other chambers of the heart would not have as significant an impact.

Which of the following is NOT associated with the function of helper T cells? A. MHC I B. CD4 receptor C. MHC II D. cytokines

A. MHC I MHC I is recognized by killer T cells and does not play a role in the function of helper T cells. Helper T cells have a CD4 receptor which recognizes MHC II on antigen presenting cells. This helps activate the helper T cell (MHC II and CD4 receptors are associated with helper T cell function and can be eliminated). Helper T cells also secrete cytokines to stimulate proliferation of B cells and killer T cells; this is in fact their primary function (cytokines are associated with helper T cell function and can be eliminated). This helps activate the helper T cell (MHC II and CD4 receptors are associated with helper T cell function and can be eliminated). Helper T cells also secrete cytokines to stimulate proliferation of B cells and killer T cells; this is in fact their primary function (cytokines are associated with helper T cell function and can be eliminated).

Which of the following statements about MHC I and MHC II is NOT true? A. MHC II is found on all nucleated cells. B. MHC II presents peptide fragments to helper T cells via the CD4 receptor. C. MHC I is found on antigen presenting cells. D. MHC I presents peptide fragments to cytotoxic T cells via the CD8 receptor.

A. MHC II is found on all nucleated cells. MHC I is found on all nucleated cells, including antigen presenting cells. MHC I presents peptide fragments to cytotoxic T cells via the CD8 receptor. MHC II presents peptide fragments to helper T cells via the CD4 receptor. However, MHC II is found only on antigen presenting cells, such as macrophages and B cells.

A decrease in blood pH can lead to a decrease in CSF pH, which can trigger an increase in ventilation rate. Which region of the brain contains the respiratory center that can alter the rate of ventilation? A. Medulla oblongata B. Hypothalamus C. Cerebellum D. Corpus callosum

A. Medulla oblongata A. The medulla contains the main respiratory rhythmicity centers that control ventilation rate, and also contains the central chemoreceptors that would monitor CSF pH (choice A is correct). The hypothalamus maintains body homeostasis, including body temperature, ion balance, hunger/thirst, etc., primarily by controlling the pituitary gland (choice B is wrong). The cerebellum helps to smooth and coordinate body movement (choice C is wrong), and the corpus callosum is the bridge between the two hemispheres of the brain (choice D is wrong).

A mutation in hemoglobin is identified that decreases the degree of cooperativity of binding of oxygen to nH = 1.4 (for normal hemoglobin, nH = 2.8). What is true of this mutant form of hemoglobin? A. Oxygen release from hemoglobin will occur over a larger range of partial pressures of oxygen. B. Hemoglobin will carry an increased quantity of oxygen. C. Hemoglobin will display the same degree of cooperativity as myoglobin. D. Hemoglobin will carry a decreased quantity of oxygen.

A. Oxygen release from hemoglobin will occur over a larger range of partial pressures of oxygen. The greater the degree of cooperativity of hemoglobin, the more concerted the oxygen binding and release from hemoglobin. The quantity of oxygen that can be carried by hemoglobin is unlikely to change given four oxygen binding sites still exist per hemoglobin and there is no information presented here to explain why this would have changed. Myoglobin, with only a single oxygen binding site, does not display cooperativity (nH = 1). Therefore this mutant form of hemoglobin still maintains a greater degree of cooperativity than myoglobin.

During ventricular contraction, which of the following valves is open? A. The valve between the left ventricle and the aorta B. The valve between the left ventricle and the pulmonary artery C. The valve between the left ventricle and right ventricle D. The valve between the left ventricle and left atrium

A. The valve between the left ventricle and the aorta When the ventricles contract, the blood from the left ventricle is forced through the aortic semilunar valve and into the aorta, and the blood from the right ventricle is forced through the pulmonary semilunar valve and into the pulmonary vasculature. In a normal heart, there is no valve between the right and left ventricles or between the left ventricle and the pulmonary artery. While there is a valve between the left ventricle and left atrium, this bicuspid (mitral) valve is closed during ventricular contraction (systole) to prevent the backflow of blood into the atrium.

The hemoglobin dissociation curve is "shifted to the left" by all of the following EXCEPT: A. decreased pH. B. fetal hemoglobin. C. decreased temperature. D. decreased carbon dioxide.

A. decreased pH. A left-shifted curve is representative of hemoglobin with a higher oxygen affinity (i.e., it binds oxygen more tightly and does not release it as readily). In contrast, a right-shifted curve represents hemoglobin with a lower affinity for oxygen, making it easier to release that oxygen to the tissues. Fetal hemoglobin has a higher affinity for oxygen compared to adult hemoglobin; this way it can "steal" oxygen off of Mom's hemoglobin (fetal hemoglobin would display a left-shifted curve and can be eliminated). Decreased CO2 and decreased temperatures are consistent with situations when the body is in a state of rest; under these conditions oxygen demand in the tissues is not as high and the hemoglobin can have a higher O2 affinity (decreased carbon dioxide and decreased temperature would display a left-shifted curve and can be eliminated). However, a decrease in pH is indicative of an increase in activity (due to lactic acid production and increased CO2 from aerobic respiration); in high-activity situations the tissue's need for oxygen increases, thus the hemoglobin dissociation curve shifts to the right, allowing for oxygen to be released to the tissues more readily (decreased pH would lead to a right-shifted curve and is the correct answer here).

Antibody light chains are: A. not specific for each class of antibody. B. the constant region of the protein. C. the regions of the antibody that bind to antigen. D. only composed of carbohydrate.

A. not specific for each class of antibody. First, do not get confused between the variable region and the light chain. Remember that the light chain and the heavy chain have both variable and constant domains. Further, it is the heavy chain constant domain that is specific for each class of antibody; the light chain has no class specificity. The variable domains of the chains are specific for (and bind to) antigen, not the light chain as a whole. Antibodies are protein molecules, not carbohydrates.

The hypothalamus modulates pituitary activity by producing releasing and inhibiting factors. Disruption of the hypothalamic-pituitary portal system would most likely result in: A. widespread endocrine malfunction. B. only moderately impaired endocrine function, due to the fact that hypothalamic hormones would remain free to affect target cells directly. C. overproduction of all pituitary hormones. D. underproduction of all pituitary hormones.

A. widespread endocrine malfunction. The hypothalamic-pituitary portal system is used to deliver hypothalamic releasing and inhibiting factors to the anterior pituitary, which in turn responds by releasing or not releasing one of the seven different hormones it produces. If this system were disrupted, the anterior pituitary would not be properly controlled; some anterior pituitary hormones would be underproduced (those regulated by releasing factors) and some would be overproduced (those regulated by inhibiting factors). Because the anterior pituitary hormones control other endocrine glands, widespread malfunction of the endocrine system would ensue. The only target for the hypothalamic hormones is the anterior pituitary, so these hormones could not affect the body in general.

Which of the following is the first event in transduction of light by rod cells? A. A sodium channel opens and the cell depolarizes. B. A sodium channel closes and the cell hyperpolarizes. C. A potassium channel opens and the cell hyperpolarizes. D. A potassium channel closes and the cell depolarizes.

B. A sodium channel closes and the cell hyperpolarizes. B. Rod cells are unique in that they are depolarized at rest by the constant influx of Na+. Stimulation by light causes the Na+ channel to close (choices C and D are wrong) and the rod cell to hyperpolarize (choice B is correct and choice A is wrong).

Atropine is a medication sometimes used to treat symptomatic bradycardia (slow heart rate). What is the most likely mechanism of action of atropine? A. Partial inhibition of slow sodium leak channels B. Acetylcholine antagonist C. Prevent Ca2+ binding to troponin in cardiac sarcomeres D. Acetylcholine agonist

B. Acetylcholine antagonist Drugs used to treat bradycardia must act to increase heart rate. Acetylcholine has inhibitory effects on cardiac pacemaker activity, thus any drug that inhibits acetylcholine (i.e., an antagonist) will increase heart rate and a drug that mimics acetylcholine (i.e. an agonist) would lower heart rate. Preventing the binding of Ca2+ to troponin would prevent cardiac muscle contraction altogether; this is required to shift the position of tropomyosin such that the myosin binding sites on actin are exposed. Remember that cardiac muscle is organized in the same way that skeletal muscle is and contracts via the sliding filament theory. Finally, heart rate is determined by the slow-influx of sodium through leak channels in the cells of the SA node; inhibiting these would further decrease heart rate since the cells would reach threshold less often.

Which of the following antibody components does NOT contribute to its antigen specificity? A. Light chain B. Disulfide bonds C. Heavy chain D. Variable region

B. Disulfide bonds The variable region is what composes the antigen binding site and it contains both a portion of the heavy chain and the light chain. The disulfide bonds connect the heavy chains to each other as well as connecting the light chains to the heavy chains, but they do not inherently contribute to an antibody's antigen specificity.

Auditory transduction occurs inside the cochlea. Pitch and loudness are determined by the location of maximal vibration and amplitude of vibration of the basilar membrane, respectively. Which of the following is a true statement? A. Loud, high-pitched sounds would produce large amplitude vibrations near the flexible apex of the basilar membrane. B. Loud, low-pitched sounds would produce large amplitude vibrations near the flexible apex of the basilar membrane. C. Loud, high-pitched sounds would produce small amplitude vibrations near the stiffer region of the basilar membrane near the oval window. D. Loud, low-pitched sounds would produce small amplitude vibrations near the stiffer region of the basilar membrane near the oval window.

B. Loud, low-pitched sounds would produce large amplitude vibrations near the flexible apex of the basilar membrane. B. Loud sounds produce large amplitude vibrations (choices C and D can be eliminated). High pitched (high frequency) sounds vibrate the stiffer region of the basilar membrane near the oval window, while low pitched (low frequency) sounds vibrate the more flexible apex of the basilar membrane (choice B is correct and choice A is wrong).

Non-specific defense systems include barriers to pathogen entry, chemicals that kill pathogens or destroy antigen, and phagocytic cells that ingest pathogens and antigens. Which of the following non-specific defense mechanisms is LEAST likely to be classified as a chemical method of defense? A. Complement B. Mucus C. Lysozyme D. Stomach acid

B. Mucus B. Mucus is best classified as a barrier; it is a sticky fluid that traps pathogens, dust, etc. and keeps them from entering the body (choice B is least likely to be classified as a chemical method of defense and is the correct answer choice). Complement is a set of proteins (effectively chemicals) that interacts with pathogens to destroy them (choice A can be classified as a chemical method and can be eliminated). Lysozyme is an enzyme in saliva and tears that kills bacteria non-specifically (choice C can be classified as a chemical method and can be eliminated). Stomach acid is a chemical that kills many swallowed pathogens (choice D can be classified as a chemical method and can be eliminated).

Irregular electrical activity is observed in one cardiac ventricle, but not the other. This defect in transmission is most likely found in which component of the cardiac conduction system? A. Atrioventricular node B. Purkinje fibers C. Sinoatrial node D. Internodal pathway

B. Purkinje fibers The sinoatrial node supplies electrical signal to the atria and the atrioventricular node (via the intermodal pathway) and functions as the pacemaker of the heart. The internodal pathway carries impulses between the heart's two signaling nodes. A defect in the intermodal pathway or in either node would result in symmetrical changes to both ventricles. The right and left bundle branches bifurcate after the AV node and ramify to form the Purkinje fibers in the two ventricles, with each ventricle having its own separate set of Purkinje fibers. Electrical irregularities that are seen in one ventricle but not the other would most likely be linked to transmission issues in a component that is specific to one ventricle over the other.

Antibodies are made of two heavy chains and two light chains. There are five classes of antibody that differ in their tail (non-antigen binding) region. Which of the following statements about antibodies is true? A. The antigen-binding region is made only of light chains and the tail region is made only of heavy chains. B. The antigen-binding region is made of both heavy and light chains, but the tail region is made only of heavy chains. C. The antigen-binding region is made of only light chains, but the tail region is made of both heavy and light chains. D. The antigen-binding region is made only of heavy chains and the tail region is made only of light chains.

B. The antigen-binding region is made of both heavy and light chains, but the tail region is made only of heavy chains. The tail region of the antibody molecule is known as the FC region. It determines the class of antibody (IgG, IgA, IgM, IgE, or IgD) and is made only of heavy chains (choices C and D are wrong). The antigen-binding region is the variable portion of the antibody molecule and is made of both heavy and light chains (choice A is wrong and choice B is correct).

Patients with Marfan syndrome experience increased elasticity in connective tissues, including those found in blood vessels. These patients often experience progressive aortic dilation, particularly through the ascending aorta and the aortic arch. Such dilation would be expected to have which of the following effects? A. The aortic semilunar valve would be expected to leak as the expansion of the aorta pulled on it resulting in changes to the first heart sound. B. The aortic semilunar valve would be expected to leak as the expansion of the aorta pulled on it resulting in changes to the second heart sound. C. The mitral valve would be expected to leak as the expansion of the aorta pulled on it resulting in changes to the second heart sound. D. The mitral valve would be expected to leak as the expansion of the aorta pulled on it resulting in changes to the first heart sound.

B. The aortic semilunar valve would be expected to leak as the expansion of the aorta pulled on it resulting in changes to the second heart sound. The aorta is directly connected to the aortic semilunar valve; while the mitral valve is also on the left side of the heart, it is positioned between the atrium and the ventricle. The aortic dilation would eventually cause the position of the flaps in the semilunar valve to shift such that they did not seal as effectively, thus allowing for leakage through the valve. The closure of the semilunar valves produces the second heart sound, so leakage in a semilunar valve would change that sound and produce a heart murmur. Note that first heart sound is linked to the closure of the atrioventricular valves (tricuspid and mitral).

A neuroscientist develops a chemical that increases the permeability of neuron membranes to potassium. After administering this drug, she attempts to elicit action potentials, but notes the rates of firing have changed dramatically. Which of the following best explains this observation? A. The resting membrane potential shifted in a more positive direction. B. The resting membrane potential shifted in a more negative direction. C. The Na+/K+ ATPase is unable to maintain concentration gradients. D. The rapid depolarization phase of the action potential was most significantly impacted.

B. The resting membrane potential shifted in a more negative direction. By increasing the permeability of the neuron membrane to potassium, the researcher shifted the resting membrane potential in a more negative direction. This pushes the neuron further from threshold and it would require more stimulation in order to generate action potentials, resulting in a probable decrease in firing rate (choice B is correct and choice A is wrong). The Na+/K+ ATPase is an active transporter, using ATP to move Na+ ions out of the cell and K+ ions into the cell; its action would be unaffected by an increase in membrane potassium permeability (choice C is wrong). The rapid depolarization seen in an action potential is due to the opening of voltage-gated sodium channels. Assuming the cell could get to threshold, the opening of these channels should not be affected by an increase in potassium permeability (choice D is wrong).

The brain contributes to sex hormone secretion in males by: A. secreting FSH and LH from the posterior pituitary, in response to GnRH. B. secreting LH (which affects interstitial cells in the testes), and FSH (which stimulates sustentacular cells). C. inhibiting FSH and LH production in the testes, thereby increasing systemic testosterone. D. increasing testosterone secretion, primarily from sustentacular cells in the testes.

B. secreting LH (which affects interstitial cells in the testes), and FSH (which stimulates sustentacular cells). B. GnRH is released from the hypothalamus and induces FSH and LH secretion from the anterior pituitary (choices A and C are wrong). FSH stimulates the sustentacular (Sertoli) cells in the testes to produce many secretions that affect spermatogenesis (primarily). LH stimulates interstitial (Leydig) cells to produce testosterone (choice B is correct and choice D is wrong).

Blood pressure is increased when: A. antidiuretic hormone increases sodium reabsorption in nephrons. B. sympathetic activation decreases the diameter of arterioles systemically. C. aldosterone increases water permeability in the collecting ducts of nephrons. D. parasympathetic innervation increases the flow of blood to digestive organs.

B. sympathetic activation decreases the diameter of arterioles systemically. Activation of the sympathetic division of the ANS triggers systemic vasoconstriction (decrease in diameter) in arterioles, leading to an increase in systemic blood pressure. The choices "aldosterone increases water permeability in the collecting ducts of nephrons" and "antidiuretic hormone increases sodium reabsorption in nephrons" have the functions of the hormones backwards (and thus are wrong): aldosterone increases sodium reabsorption in nephrons and antidiuretic hormone increases water permeability. (Note that the two hormones working together would lead to an increase in total body salt and consequently, total body water, followed by an increase in blood pressure.) While it is true that blood flow to digestive organs is increased when the body is under parasympathetic control, this is not due to the direct action of the parasympathetic division on the blood vessels to those organs. The parasympathetic division actually does not innervate the blood vessels at all; the increased blood flow under these conditions is due to the withdrawal of sympathetic stimulation. Even if the parasympathetic division DID increase vessel diameter, this would not lead to an increase in blood pressure.

Heart murmurs are extra, abnormal sounds (beyond the normal closure of the valves) produced during the cardiac cycle. They can be caused by stenotic (stiffened) valves, or by valves that do not close properly and allow regurgitation. Murmurs are classified as diastolic or systolic depending on when the additional sound is produced. A heart murmur caused by a failure of the AV valves to close properly would most likely be classified as a: A. diastolic murmur, because this would allow flow from the atria to the ventricles during diastole. B. systolic murmur, because this would allow regurgitation of blood from the ventricles to the atria during systole. C. diastolic murmur, because this would allow regurgitation of blood from the arteries to the ventricles during diastole. D. systolic murmur, because this would allow additional blood to flow from the atria to the ventricles during systole.

B. systolic murmur, because this would allow regurgitation of blood from the ventricles to the atria during systole. B. The AV valves close at the beginning of systole to prevent regurgitation of blood into the atria while the ventricles are contracting. If the AV valves failed to close properly, blood from the high-pressure ventricles would flow back into the low-pressure atria during systole and would produce an abnormal murmur (choice B is correct). Flow from the atria to the ventricles during systole would be prevented by the pressure gradient (choice D is wrong). Blood normally flows from the atria to the ventricles during diastole, through the open AV valves; this would not produce a murmur (choice A is wrong), and these valves do not separate the ventricles and the arteries so this would not affect blood flow between those regions (choice C is wrong).

The affinity of hemoglobin for oxygen: A. is low in the lungs and low in the tissues. B. remains constant throughout the body. C. is high in the lungs and low in the tissues. D. is low in the lungs and high in the tissues.

C. is high in the lungs and low in the tissues. The affinity of hemoglobin for oxygen is highest in the lungs (where it needs to pick up oxygen, "is low in the lungs and high in the tissues" and "is low in the lungs and low in the tissues" are wrong) and lowest in the tissues (where it needs to release oxygen, "is high in the lungs and low in the tissues" is correct and "remains constant throughout the body" is wrong).

Which of the following are hormones released by the posterior pituitary? A. Thyroid stimulating hormone and growth hormone B. Follicle stimulating hormone and luteinizing hormone C. Antidiuretic hormone and oxytocin D. Androgens and estrogens

C. Antidiuretic hormone and oxytocin

The removal of MHC I from somatic cells would have the most direct impact on what cell-mediated immune system function? A. CD4 T cells would no longer be able to co-stimulate B cells and promote antibody production. B. CD4 T cells would no longer be checked for autoreactivity in the thymus. C. CD8 T cells would no longer be able to recognize virally infected cells. D. CD8 T cells would no longer be able to interact with macrophages, but would still interact with dendritic cells.

C. CD8 T cells would no longer be able to recognize virally infected cells. Major histocompatibility complex (MHC) I interacts with CD8 killer T cells rather than CD4 helper T cells so B cell stimulation and thymic education would remain unaffected. However, MHC I's display of intracellular peptides allows CD8 T cells to examine other cells for viral infection and without such a display, those T cells would not be able to carry out that immune system function. MHC I is used by both macrophages and dendritic cells to communicate with CD8 T cells so both would be impacted by such a change.

Landmark studies establishing the quantal nature of synaptic transmission utilized curare to block postsynaptic receptors and prevent action potential transmission. Which of the following best explains the impact of curare on the synapse? A. Decreases neurotransmitter release B. Increases calcium influx into the presynaptic terminal C. Decreases cation flow into the postsynaptic neuron D. Blocks voltage-gated calcium channels

C. Decreases cation flow into the postsynaptic neuron C. The stem of the question informs us that curare has an impact on postsynaptic receptors. This makes it unlikely to have any effect presynaptically, such as neurotransmitter release (choice A can be eliminated) or calcium influx into the presynaptic terminal (choice B can be eliminated). Voltage-gated calcium channels are present on the presynaptic neuron and are also not likely to be affected by a compound which blocks postsynaptic receptors (choice D can be eliminated). The only answer choice which clearly has a postsynaptic action is choice C; often neurotransmitter receptors on postsynaptic neurons are linked to ion channels. The opening of these ion channels impacts ion flow into the postsynaptic cell. If curare blocked the receptors from binding neurotransmitter, the ion channels could not be opened, leading to a decrease in cation flow into the postsynaptic neuron and ultimately, prevention of action potential transmission (choice C is correct). Curare is a competitive inhibitor of acetylcholine which is a neurotransmitter that acts, among other places, at the neuromuscular junction. Note that you did not have to know anything about curare specifically to answer this question.

Which of the following physiological responses is LEAST likely to occur upon stimulation of the parasympathetic division of the ANS? A. Increased digestive secretion and motility B. Constricted bronchial tubes C. Enhanced distance vision D. Reduced heart rate

C. Enhanced distance vision C. The parasympathetic division is also known as the "rest and digest" division, and leads to effects in the body such as increased digestive activity (choice A Is likely to occur and can be eliminated), reduced air flow (choice B is likely to occur and can be eliminated), and reduced heart rate (choice D is likely to occur and can be eliminated). However distance vision is a feature of the sympathetic nervous system; the parasympathetic division enhances near-object vision (choice C is least likely to occur and is the correct answer choice).

In diabetes mellitus, insulin is either not made in sufficient quantities or is not responded to appropriately by the body. Though the impact on the kidneys can be significant, which of the following would NOT be expected at noticeable levels in the urine of a diabetic? A. Ketones B. Electrolytes C. Erythrocytes D. Glucose

C. Erythrocytes Since glucose is not being processed properly in diabetics, blood glucose tends to be very high. This means that more glucose will be filtered into the nephrons at the glomeruli, and this higher level of glucose will overwhelm the transporters moving the filtered glucose back into the blood. Not all of the glucose will get transported out of the nephron, thus glucose is expected in the urine of a diabetic. Without glucose to use for energy, diabetics metabolize proteins and fats for energy, producing ketone bodies that are then excreted. Electrolytes would be found in anyone's urine, regardless of whether or not the person had diabetes. However, red blood cells (erythrocytes) in the urine are a sign of infection and/or damage and are not an expected waste in the urine of diabetics.

Which of the following statements concerning thyroid hormone is true? A. It is derived from cholesterol and binds a receptor on the cell surface. B. It is derived from cholesterol and binds a receptor within the cell. C. It is derived from amino acids and binds a receptor within the cell. D. It is derived from amino acids and binds a receptor on the cell surface.

C. It is derived from amino acids and binds a receptor within the cell. This is a two-by-two question: determining one piece of information can eliminate two incorrect answers. Thyroid hormone is derived from tyrosine, an amino acid. Cholesterol is used to produce steroid hormones (choices containing "cholesterol" can be eliminated). Although it is derived from an amino acid, thyroid hormone behaves like a steroid hormone; thyroid hormone receptors are found within cells, and not on their surface.

T cells are involved in cell-mediated immunity, interacting directly with our own cells to help protect us from disease. MHC proteins assist T cells in their function. Which of the following statements is true about T cells? A. Killer T cells bind to antigen displayed on MHC II and directly destroy abnormal cells. B. Helper T cells bind to antigen displayed on MHC I and secrete chemicals to help killer T cells proliferate. C. Killer T cells bind to antigen displayed on MHC I and directly destroy abnormal cells. D. Helper T cells bind to antigen displayed on MHC II and assist killer T cells by directly destroying abnormal cells.

C. Killer T cells bind to antigen displayed on MHC I and directly destroy abnormal cells. MHC proteins display intracellular antigen on the cell surface and interact with T cells. Killer T cells bind to antigen displayed on MHC I (choice A is wrong) and helper T cells bind to antigen displayed on MHC II (choice B is wrong). Killer T cells destroy abnormal cells directly, while helper T cells secrete chemicals (cytokines) to stimulate the proliferation of killer T cells and B cells (choice C is correct and choice D is wrong).

An unconscious patient arrives in the emergency room after being in a car accident. The patient has lost a severe amount of blood and will require a red blood cell transfusion. Which of the following blood types is the safest to transfuse into the patient? A. B- B. AB+ C. O- D. A+

C. O- ABO blood types are determined by specific antigens present on the surface of each red blood cell (RBC). Type A blood has the A antigen, type B has the B antigen, type AB has both the A and B antigens, and type O has no antigen. Rh factor is an additional antigen that may or may not be present on the RBC surface. If a person's red cells display the Rh antigen they are considered to be Rh+, and if they lack that antigen they are considered to be Rh-. The question states that the patient is unconscious and is therefore unable to dictate his blood type. Administration of an incompatible blood type would cause a transfusion reaction. In a transfusion reaction, antibodies in the recipient that are specific for the surface antigens on the donated blood cells bind to and lead to the destruction of the donated cells. The administered blood should therefore have no antigens to trigger a response in the recipient: no ABO group antigens and no Rh factor. The safest blood to administer is O-.

What is the primary contribution of B cells in an adaptive immune response? A. Triggering the complement cascade B. Interaction with MHC I C. Production of antibodies specific to an antigen D. Activating CD8+ T cells

C. Production of antibodies specific to an antigen

The exchange of fluid between the blood in the capillaries and the surrounding tissues is the result of opposing osmotic and hydrostatic pressure differentials. Which of the following accurately describes the relationship between hydrostatic and osmotic pressure differentials in the capillaries? A. The osmotic pressure differential forces fluid out of the capillaries and into the tissues at the venous end. B. The hydrostatic pressure differential forces fluid out of the tissue and into the capillaries at the arterial end. C. The hydrostatic pressure differential causes fluid to move out of the capillaries at the arterial end. D. The osmotic pressure differential causes solutes and fluid to be filtered out of the capillaries at the arterial end.

C. The hydrostatic pressure differential causes fluid to move out of the capillaries at the arterial end. Arterial pressure is higher than the pressure on the venous side of the capillaries. Thus, hydrostatic pressure tends to drive fluids out of the blood and into the tissues on the arterial side and back out of the tissues on the venous side. Osmotic pressure is greater in the plasma than in the interstitial fluid, because plasma has a much higher protein concentration; therefore, osmotic pressure tends to draw fluid into the blood, out of the tissues.

Varicose veins are swollen, twisted vessels typically found in the legs. They are the result of poorly functioning venous valves combined with increased pressure in the vein that limits blood flow. This causes a pooling of blood in the vessel. Which of the following is the most likely reason that veins become varicose, but not arteries? A. Arterial valves are much stronger than venous valves and are less likely to fail, leading to less pooling of arterial blood. B. The pressure in the arteries never becomes high enough to lead to varicosities. C. The walls of veins are much less elastic than arteries, preventing the vein from regaining its shape after being stretched by the pooled blood. D. The blood in the leg arteries flows downward, while the blood in the leg veins flows upward, against gravity.

C. The walls of veins are much less elastic than arteries, preventing the vein from regaining its shape after being stretched by the pooled blood. C. Veins are far more likely to become swollen and enlarged because they lack the elasticity that arteries have. The elastic walls of the arteries are what allow arteries to stretch and expand, and then regain their shape. When veins expand due to the pooling of blood, they cannot regain their shape as easily. Over time, the vein becomes permanently enlarged (choice C is correct). Arteries do not contain valves (choice A is wrong). The pressure in the arteries is very high; much higher than venous pressure. However, the muscular wall of the artery helps to resist that pressure, plus the elasticity of artery wall ensures that even if it enlarges, it can regain its shape (choice B is wrong). While it is true that blood in the leg generally flows upward against gravity, this fact alone is not enough to explain why veins become varicose and not arteries. There are places in the body where blood in arteries flows upward, against gravity (the carotid arteries) and these do not become varicose (choice D is true but irrelevant).

The anterior pituitary gland produces a wide variety of hormones that influence a range of physiological functions. Which of the following processes is NOT directly mediated by hormones produced in the anterior pituitary? A. Bone growth B. Ovulation C. Water retention D. Milk production

C. Water retention Water retention is mediated by ADH, a hormone produced in the hypothalamus and released by the posterior pituitary. Although a case could be made that ACTH affects water retention indirectly by stimulating the release of aldosterone, the question asks for directlymediated processes. Milk production is influenced by prolactin. Growth hormone stimulates bone growth, and ovulation is mediated by LH. These three processes are all mediated by anterior pituitary hormones.

Hormones are signaling molecules released by cells, which travel through the bloodstream and bind to receptors at target cells in other parts of the body. All of the following hormone receptors contain transmembrane domains EXCEPT: A. calcitonin receptors. B. growth hormone receptors. C. cortisol receptors. D. cholecystokinin receptors.

C. cortisol receptors. Peptide hormones bind to cell surface receptors embedded within the plasma membrane and trigger a cascade of effects within the cell. Steroid hormones cross the plasma membrane and bind to cytoplasmic receptors, which then act as transcription factors to regulate gene expression. Growth hormone, calcitonin, and cholecystokinin are all peptide hormones and would thus bind to cell membrane receptors. Cortisol is a steroid hormone; its receptor would be found in the cytoplasm and would not contain a transmembrane domain.

Addison's disease, or chronic adrenal insufficiency, is due to hypofunction of the adrenal cortex. This condition will make a person have: A. high sex hormone concentrations. B. high plasma cortisol. C. high urinary output. D. increased resistance to stress.

C. high urinary output. The adrenal cortex makes primarily cortisol and aldosterone. Lack of aldosterone will reduce reabsorption of sodium and water from urine as it forms, increasing the volume of urine produced; thus, "high urinary output is true." Loss of cortisol will reduce stress resistance (eliminating "increased resistance to stress" and "high plasma cortisol"), and adrenal sex steroid production is generally not a great portion of the total and would be expected to decrease if it is affected (eliminating "high sex hormone concentrations").

An increase in which of the following increases the O2affinity of hemoglobin? A. Partial pressure of CO2 B. 2,3-BPG (2,3-bisphosphoglycerate) C. pH D. Temperature

C. pH The O2 dissociation curve is shifted to the right (reduced O2 affinity) by an increase in any of the following: H+ concentration (decreased pH), partial pressure of CO2, temperature, and the concentration of 2,3-BPG. An easier way to remember this is to think of the conditions in an exercising muscle (which would benefit from a reduced O2 affinity that allows for easier oxygen unloading): hot, acidic, and hypercarbic (increased CO2). Therefore, the opposite conditions would lead to an increased oxygen affinity, i.e. a decrease in H+ concentration (increased pH), partial pressure of CO2, temperature and the concentration of 2,3-BPG.

A hormone is discovered that rapidly accumulates inside renal cells in the absence of endocytosis when administered to mice intravenously. The hormone is most likely a: A. second messenger. B. polypeptide. C. steroid. D. neurotransmitter.

C. steroid. If the hormone accumulates inside the cell in the absence of endocytosis, the hormone must diffuse through the plasma membrane. Steroid hormones are small and hydrophobic and can freely diffuse through the plasma membrane. Polypeptides, however, cannot diffuse through membranes since they are large hydrophilic molecules. "Second messenger" is incorrect since second messengers carry hormone signals inside the cell but are not themselves hormones, and "neurotransmitter" is wrong since neurotransmitters are charged molecules that work at the cell surface.

All of the following statements regarding antibody structure are true EXCEPT: A. antibodies have a quaternary protein structure. B. genes for antibodies undergo genetic rearrangement to ensure that a very wide variety of antigen-binding regions can be produced. C. the antigen binding region of the antibody is comprised of only heavy chains. D. antibodies can neutralize certain toxins.

C. the antigen binding region of the antibody is comprised of only heavy chains. The antigen binding region of the antibody is comprised of both heavy and light chains. Antibodies are made of several protein subunits held together. The genes for antibodies do undergo rearrangement. This is to ensure that a huge population of antibodies are produced, thus increasing the likelihood of an antigen being recognized. Antibodies can neutralize toxins if they bind to the toxin's active site and cover it.

Lymphatic vessels are most like: A. arteries, because they are very elastic and have muscular walls. B. arteries, because they are large and carry fluid at low pressure. C. veins, because they carry fluid toward the heart and are at low pressure. D. veins, because the fluid they carry is low in oxygen and at low pressure.

C. veins, because they carry fluid toward the heart and are at low pressure. C. Lymphatic vessels are more like veins than arteries. They carry fluid toward the heart, are very thin, non-elastic, and do not have a muscle layer (choice A is wrong), have valves, and are at low pressure (choice C is correct and choice B is wrong). The fluid in lymphatic vessels is low in oxygen, but not all veins carry low-oxygen blood. The pulmonary veins carry blood rich in oxygen toward the heart (choice D is wrong).

The rate of oxidative metabolism is measured using a basal metabolic rate (BMR) test. If a subject has hyperthyroidism, the rate: A. cannot be determined. B. will be normal. C. will be above normal. D. will be below normal.

C. will be above normal. One of the primary activities of thyroid hormone is to increase the basal metabolic rate.

What is the main difference between a primary and secondary immune response? A. Involvement of the thymus and spleen in mediating the response B. Use of innate immune mechanisms as part of the response C. Cells involved in carrying out the response D. Time required to fully activate the response

D. Time required to fully activate the response

A patient presents at a hospital emergency room with a blockage in his left primary bronchus that completely obstructs air flow at that point. Compared to the curve for his right lung, the hemoglobin saturation curve for his left lung would be: A. right-shifted, due to an increase in pH. B. left-shifted, due to an increase in pH. C. left-shifted, due to a decrease in pH. D. right-shifted, due to a decrease in pH.

D. right-shifted, due to a decrease in pH. A blockage that completely obstructs air flow means that no gas exchange will occur in that region. A complete blockage in the left primary bronchus would cause the pH of the blood in the left lung to decrease, due to an accumulation of carbon dioxide ("right-shifted, due to an increase in pH" and "left-shifted, due to an increase in pH" are wrong). A decrease in pH causes the hemoglobin saturation curve to shift to the right (the Bohr shift, "left-shifted, due to a decrease in pH" is wrong).

Seizures, which result from foci of abnormal excessive brain activity, can spread to surrounding areas of the brain. In select patients, this activity can spread beyond the originating hemisphere. Severing which of the following structures would aid in limiting the spread of excessive activity? A. Brainstem B. Cerebral cortex C. Thalamus D. Corpus callosum

D. Corpus callosum D. The corpus callosum connects the left and right hemispheres of the brain and in select patients, severing this connection can decrease the severity of recurrent seizures (choice D is correct). Severing the brain stem, which is critical for numerous basic vital functions (e.g. breathing), would kill the patient (choice A is wrong). The cerebral cortex, which is the outer layer of the brain, is critical for higher level thought and self-awareness (choice B is wrong), and the thalamus is involved in relaying sensory and motor information to and from the brain (choice C is wrong).

Continuous myelination of the axon would most likely result in which of the following? A. Increased ion flow across the plasma membrane B. Increased membrane depolarization required to fire an action potential C. Decreased membrane resistance D. Decreased reliable signal transduction to the axon terminus

D. Decreased reliable signal transduction to the axon terminus D. Continuous myelination of the axon would decrease the ability of an action potential to reach the axon terminus (choice D is correct). Under normal conditions, myelin surrounds the plasma membrane and prevents ion flow, resulting in an increase in membrane resistance (choices A and C are wrong). Breaks in the myelin sheath along the axon, known as nodes of Ranvier, are where voltage-gated sodium channels exist at high concentrations. These nodes effectively boost the signal as the action potential travels along the axon. Without these nodes, the ability of that initial action potential to reach the axon terminus would be greatly impaired. The threshold of voltage-gated sodium channels is unlikely to change with myelination (choice B is wrong).

Which of the following does NOT describe an effect of parathyroid hormone? A. It increases calcium reabsorption in the kidneys. B. It promotes osteoclast activity, compared to osteoblast activity. C. It increases bone resorption. D. It decreases phosphate excretion in kidneys.

D. It decreases phosphate excretion in kidneys. The primary role of parathyroid hormone (PTH) is to increase free calcium levels in the blood. To achieve this, PTH targets three organ systems. First, PTH fosters bone resorption by promoting osteoclast activity ("increases bone resorption" and "promotes osteoclast activity, compared to osteoblast activity" are effects of PTH and can be eliminated). Osteoclasts (close relatives of macrophages) dissolve bone, releasing calcium and phosphate into the blood. PTH targets the kidneys to increase calcium reabsorption, also increasing blood calcium levels ("increases calcium reabsorption in the kidneys" is an effect of PTH and can be eliminated). Because calcium may re-precipitate with phosphate to lay down new bone, PTH also acts to decrease phosphate levels by INCREASING phosphate excretion in the kidneys. This helps "trap" free calcium in the blood ("decreases phosphate excretion in kidneys" is false and the correct answer choice). Note that you did not have to understand PTH's role in phosphate excretion to answer this question... the correct answer is obtainable simply by process of elimination.

Which of the following does NOT perform endocrine functions? A. Thyroid B. Testes C. Pancreas D. Liver

D. Liver An endocrine gland is a ductless gland whose secretory products, hormones, are picked up by capillaries. This is different than an exocrine gland, which secretes products into ducts to travel to a body cavity or the body surface. The pancreas (secretes insulin and glucagon), testes (secrete testosterone), and thyroid (secretes thyroxine) are all endocrine glands. The liver is an exocrine gland, secreting bile into a duct that travels to the duodenum. Note that the pancreas has exocrine functions in addition to its endocrine role; it synthesizes enzymes and releases them into the duodenum via a duct.

Which of the following does NOT carry oxygenated blood? A. Coronary arteries B. Femoral artery C. Carotid arteries D. Pulmonary artery

D. Pulmonary artery The pulmonary artery carries deoxygenated blood from the right ventricle to the lung to pick up oxygen. The femoral artery carries oxygenated blood in the leg, the coronary arteries branch from the aorta to provide oxygenated blood to the heart muscle cells, and the carotid arteries carry oxygenated blood from the aorta to the brain.

Which of the following correctly describes the path of blood traveling through the pulmonic circuit? A. Pulmonary vein, lungs, pulmonary artery, left atrium B. Pulmonary artery, lungs, pulmonary vein, right atrium C. Pulmonary vein, lungs, pulmonary artery, left ventricle D. Pulmonary artery, lungs, pulmonary vein, left atrium

D. Pulmonary artery, lungs, pulmonary vein, left atrium

A researcher records the membrane potential changes in a neuron in cell culture. Following excitation of a single nearby neuron, the membrane potential increases by 20 mV. If an additional nearby neuron is stimulated at the same time, an increase in membrane voltage of 32 mV is observed. Which of the following best explains this observation? A. Long-term depression B. Neural adaptation C. Temporal summation D. Spatial summation

D. Spatial summation The experiment describes two neurons synapsing with a third neuron from which membrane potential is recorded. When one neuron is excited, a depolarization is recorded, and when the second neuron is excited at the same time, a larger depolarization is recorded. This additive effect (two neurons synapsing on a single neuron and generating a larger response) is known as spatial summation (choice D is correct). Temporal summation involves the additive response due to repeated stimulation of a single neuron (choice C is wrong). Long-term depression is a decrease in neural excitability (choice A is wrong) and neural adaptation is a change in response over time (usually a decrease in firing) with a constant stimulus (choice B is wrong).

Which of the following does NOT act as an antigen to the immune system at any point? A. Bacterial cell wall proteins B. Red blood cell membrane proteins C. Viral capsid proteins D. Viral nucleic acid

D. Viral nucleic acid Antigens are anything that can trigger an immune response (i.e., antibody production, etc.). These are generally proteins on the outer surfaces of pathogens, such as viral capsid proteins (viral capsid proteins can act as an antigen and can be eliminated) or bacterial cell wall proteins (bacterial cell wall proteins can act as an antigen and can be eliminated). Red blood cell membrane proteins can also trigger an immune response if a person that doesn't naturally have them in their system is accidentally exposed to them; for example, a person with type A blood (and hence type A antigen on their red cells) receives type B blood (containing type B antigen on the red cells) on accident (red blood cell membrane proteins can act as an antigen and can be eliminated). However, viral nucleic acid is found inside the viral capsid. As such, it is "hidden" from the immune system and is not generally antigenic (viral nucleic acid does not act as an antigen and is the correct answer choice).

Which of the following is FALSE regarding the pacemaker cells in the sinoatrial node? A. Pacemakers cells are present outside of the sinoatrial node. B. Voltage-gated potassium channels open to repolarize the membrane. C. Voltage-gated calcium channels open to depolarize the membrane. D. Voltage-gated sodium channels open to bring the cells to the threshold membrane potential.

D. Voltage-gated sodium channels open to bring the cells to the threshold membrane potential. Pacemaker cells are present in the SA node, the AV node, and the His-Purkinje tracts and exhibit automaticity, which is the result of an unstable resting potential. The instability is due to a steady influx of sodium ions across the membrane through sodium leak channels (not voltage-gated sodium channels). Once the membrane reaches the threshold potential, voltage-gated calcium channels open, allowing calcium to flow into the cells and the membrane to depolarize, and once the membrane become very positive (around +20 mV), voltage-gated potassium channels open and allow potassium ions to flow out of the cells and the membrane to repolarize.

An atrial septal defect (ASD) allows oxygenated blood to flow from the left atrium into the right atrium through a hole in the heart wall. Surgical repair of pronounced ASD would help to prevent: A. attenuation of signal between the sinoatrial and atrioventricular nodes. B. loss of pressure in pulmonary veins. C. calcification of the aortic semilunar valve. D. additional stress on the pulmonary circuit from increased pressure.

D. additional stress on the pulmonary circuit from increased pressure. The presence of an ASD always means that oxygenated blood is mixing with deoxygenated blood and being returned unnecessarily to the lung; effectively the right and left sides of the heart are connected, so the higher pressure of the left side of the heart is translated to the pulmonary circuit. Abnormal blood flow does not affect the stimulation of the heart, nor does it affects the condition of the valves.

The function of the bicuspid AV (mitral) valve is to prevent reflux from the: A. pulmonary artery to the right ventricle. B. right ventricle to the right atrium. C. aorta to the left ventricle. D. left ventricle to the left atrium.

D. left ventricle to the left atrium. The bicuspid AV valve separates the left atrium and ventricle and closes during systole to prevent reflux into the left atrium (choice D is correct). The tricuspid AV valve does the same thing on the right side of the heart (choice B is wrong). The pulmonary semilunar valve closes during diastole to prevent reflux from the pulmonary artery into the right ventricle (choice A is wrong) and the aortic semilunar valve closes at the same time to prevent reflux from the aorta into the left ventricle (choice C is wrong).

Auditory hair cells would be classified as: A. thermoreceptors. B. nociceptors. C. chemoreceptors. D. mechanoreceptors.

D. mechanoreceptors. Auditory hair cells respond to vibrations of the basilar membrane and bend when vibrations occur. Thus they are classified as mechanoreceptors (choice D is correct). Thermoreceptors respond to temperature (choice A is wrong), nociceptors respond to pain (choice B is wrong), and chemoreceptors respond to chemicals (choices A, B, and C are wrong).

Leukotrienes and prostaglandins are lipid derivatives of arachidonic acid. They bind to G-protein-coupled membrane-bound receptors found on the extracellular side of the membrane. Based on this information, to which of the following hormones would leukotrienes and prostaglandins exhibit the greatest similarity in mechanism of action? A. estrogen B. cortisol C. testosterone D. prolactin

D. prolactin Although leukotrienes and prostaglandins are lipid derivatives, the question text states that they bind to G-protein-coupled membrane receptors to exert their effects (like peptide hormones do), not to intracellular receptors and DNA (like steroid hormones do). Cortisol, testosterone, and estrogen are all steroids, so prolactin, a peptide hormone, is the best choice. (Don't forget to use the "one-of-these-things-is-not-like-the-other" technique!)