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Glossary of USMLE Physiology

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In a ventricular pacemaker cell, what phase of the action potential is affected by NE?
Phase 4; NE increases the slope of the prepotential, allowing threshold to be reached sooner, and increases the rate of firing.
Anatomical and alveolar dead spaces together constitute what space?
Physiologic dead space is the total dead space of the respiratory system.
What three organs are necessary for the production of vitamin D3(cholecalciferol)?
Skin, liver, and kidneys
What is the effect of LH on the production of adrenal androgens?
LH has no effect on the production of adrenal androgens; ACTH stimulates adrenal androgen production.
What four conditions result in secondary hyperaldosteronism?
1. CHF
2. Vena caval obstruction or constriction
3. Hepatic cirrhosis
4. Renal artery stenosis
What are the five hormones produced by Sertoli cells?
1. Inhibin
2. Estradiol (E2)
3. Androgen-binding protein
4. Meiosis inhibiting factor (in fetal tissue)
5. Antimüullerian hormone
What is the term for the negative resting membrane potential moving toward threshold?
Depolarization (i.e., Na+ influx)
Does the left or right vagus nerve innervate the SA node?
Right vagus innervates the SA node and the left vagus innervates the AV node
How does ventricular repolarization take place, base to apex or vice versa?
Repolarization is from base to apex and from epicardium to endocardium.
What is the term for any region of the respiratory system that is incapable of gas exchange?
Anatomical dead space, which ends at the level of the terminal bronchioles.
What four factors shift the Hgb-O2 dissociation curve to the right? What is the consequence of this shift?
Increased CO2, H+, temperature, and 2, 3-BPG levels all shift the curve to the right, thereby making the O2 easier to remove (decreased affinity) from the Hgb molecule.
What two factors result in the apex of the lung being hypoperfused?
Decreased pulmonary arterial pressure (low perfusion) and less-distensible vessels (high resistance) result in decreased blood flow at the apex.
What is the ratio of pulmonary to systemic blood flow?
1:1. Remember, the flow through the pulmonary circuit and the systemic circuit are equal.
To differentiate central from nephrogenic diabetes insipidus, after an injection of ADH, which will show a decreased urine flow?
Central. Remember, there is a deficiency in ADH production in the central form.
In what area of the GI tract are water-soluble vitamins absorbed?
Duodenum
What wave is the cause of the following venous pulse deflections?
• The rise in right atrial pressure secondary to blood filling and terminating when the tricuspid valves opens
V wave
What wave is the cause of the following venous pulse deflections?
• The bulging of the tricuspid valve into the right atrium
C wave
What wave is the cause of the following venous pulse deflections?
• The contraction of the right atrium
A wave
What are the four functions of saliva?
1. Provide antibacterial action
2. Lubricate
3. Begin CHO digestion
4. Begin fat digestion
When a person goes from supine to standing, what happens to the following?
• Dependent venous pressure
Increases

Remember, the carotid sinus reflex attempts to compensate by increasing both TPR and heart rate.


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When a person goes from supine to standing, what happens to the following?
• Dependent venous blood volume
Increases

Remember, the carotid sinus reflex attempts to compensate by increasing both TPR and heart rate.


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When a person goes from supine to standing, what happens to the following?
• Cardiac output
Decreases

Remember, the carotid sinus reflex attempts to compensate by increasing both TPR and heart rate.
When a person goes from supine to standing, what happens to the following?
• BP
Decreases

Remember, the carotid sinus reflex attempts to compensate by increasing both TPR and heart rate.


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When does the hydrostatic pressure in Bowman's capsule play a role in opposing filtration?
It normally does not play a role in filtration but becomes important when there is an obstruction downstream.
What happens to intrapleural pressure when the diaphragm is ontracted during inspiration?
Intrapleural pressure decreases (becomes more negative).
What is used as an index of cortisol secretion?
Urinary 17-OH steroids
If the pH is low with increased CO2 levels and decreased HCO3- levels, what is the acid-base disturbance?
Combined metabolic and respiratory acidosis
What is the term that refers to the number of channels open in a cell membrane?
Membrane conductance (think conductance = channels open)
What are the five tissues in which glucose uptake is insulin independent?
1. CNS
2. Renal tubules
3. Beta Islet cells of the pancreas
4. RBCs
5. GI mucosa
Place in order from fastest to slowest the rate of gastric emptying for CHO, fat, liquids, and proteins.
Liquids, CHO, protein, fat
Is most of the coronary artery blood flow during systole or diastole?
Diastole. During systole the left ventricle contracts, resulting in intramyocardial vessel compression and therefore very little blood flow in the coronary circulation.
What modified smooth muscle cells of the kidney monitor BP in the afferent arteriole?
The JG cells
What are the three functions of surfactant?
1. Increase compliance
2. Decrease surface tension
3. Decrease probability of pulmonary edema formation
Name the hormone—glucagon, insulin, or epinephrine:
• Glycogenolytic, gluconeogenic, lipolytic, glycolytic, and stimulated by hypoglycemia
Epinephrine
Name the hormone—glucagon, insulin, or epinephrine:
• Glycogenolytic, gluconeogenic, lipolytic, glycolytic, proteolytic, and stimulated by hypoglycemia and AAs
Glucagon
Name the hormone—glucagon, insulin, or epinephrine:
• Glycogenic, gluconeogenic, lipogenic, proteogenic, glycolytic, and stimulated by hyperglycemia, AAs, fatty acids, ketosis, ACh, GH, and Beta-agonist
Insulin
Is the hydrophobic or hydrophilic end of the phospholipids of the cell membrane facing the aqueous environment?
Hydrophilic (water-soluble) end faces the aqueous environment and the hydrophobic (water-insoluble) end faces the interior of the cell.
What type of muscle is characterized by no myoglobin, anaerobic glycolysis, high ATPase activity, and large muscle mass?
White muscle; short term too
What percentage of CO2 is carried in the plasma as HCO3- ?
90% as HCO3-, 5% as carbamino compounds, and 5% as dissolved CO2
What is the most potent male sex hormone?
Dihydrotestosterone
With a decrease in arterial diastolic pressure, what happens to
• Stroke volume?
Decreases
With a decrease in arterial diastolic pressure, what happens to
• TPR?
Decreases
With a decrease in arterial diastolic pressure, what happens to
• Heart rate?
Decreases
What linkage of complex CHOs does pancreatic amylase hydrolyze? What three complexes are formed?
Amylase hydrolyzes alpha-1, 4-glucoside linkages, forming alpha-limit dextrins, maltotriose, and maltose.
Does the heart rate determine the diastolic or systolic interval?
Heart rate determines the diastolic interval, and contractility determines the systolic interval.
On a graphical representation of filtration, reabsorption, and excretion, when does glucose first appear in the urine?
At the beginning of splay is when the renal threshold for glucose occurs and the excess begins to spill over into the urine.
What is the relationship between preload and the passive tension in a muscle?
They are directly related; the greater the preload, the greater the passive tension in the muscle and the greater the prestretch of a sarcomere.
What is the rate-limiting step in the synthetic pathway of NE at the adrenergic nerve terminal?
The conversion of tyrosine to dopamine in the cytoplasm
How many days prior to ovulation does LH surge occur in the menstrual cycle?
1 day prior to ovulation
How are flow through the loop of Henle and concentration of urine related?
As flow increases, the urine becomes more dilute because of decreased time for H2O reabsorption.
What is the PO2 of aortic blood in fetal circulation?
60%
How do elevated blood glucose levels decrease GH secretion? (Hint: what inhibitory hypothalamic hormone is stimulated by IGF-1?)
Somatotrophins are stimulated by IGF-1, and they inhibit GH secretion. GHRH stimulates GH secretion.
What segment of the nephron has the highest concentration of inulin? Lowest concentration of inulin?
Terminal collecting duct has the highest concentration and Bowman's capsule has the lowest concentration of inulin.
What type of resistance system, high or low, is formed when resistors are added in a series?
A high-resistance system is formed when resistors are added in a series.
What hormones, secreted in proportion to the size of the placenta, are an index of fetal well-being?
hCS and serum estriol, which are produced by the fetal liver and placenta, respectively, are used as estimates of fetal well-being.
What primary acid-base disturbance is caused by an increase in alveolar ventilation (decreasing CO2 levels) resulting in the reaction shifting to the left and decreasing both H+ and HCO3- levels?
Respiratory alkalosis (summary: low CO2, low H+, slightly low HCO3-)
What respiratory center in the caudal pons is the center for rhythm promoting prolonged inspirations?
Apneustic center (deep breathing place)
What area of the GI tract has the highest activity of brush border enzymes?
Jejunum (upper)
What is the term to describe the increased rate of secretion of adrenal androgens at the onset of puberty?
Adrenarche
What period is described when a larger-than-normal stimulus is needed to produce an action potential?
Relative refractory period
Does T3 or T4 have a greater affinity for its nuclear receptor?
T3 has a greater affinity for the nuclear receptor and therefore is considered the active form.
What are the three main functions of surfactant?
1. Lowers surface tension, so it decreases recoil and increases compliance
2. Reduces capillary filtration
3. Promotes stability in small alveoli by lowering surface tension
What is the only important physiological signal regulating the release of PTH?
Low interstitial free Ca2+ concentrations
What endocrine abnormality is characterized by the following changes in PTH, Ca2+, and inorganic phosphate (Pi)?
• PTH decreased, Ca2+ increased, Pi increased
Secondary hypoparathyroidism (vitamin D toxicity)
What endocrine abnormality is characterized by the following changes in PTH, Ca2+, and inorganic phosphate (Pi)?
• PTH increased, Ca2+ decreased, Pi decreased
Secondary hyperparathyroidism (vitamin D deficiency, renal disease)
What endocrine abnormality is characterized by the following changes in PTH, Ca2+, and inorganic phosphate (Pi)?
• PTH decreased, Ca2+ decreased, Pi increased
Primary hypoparathyroidism
What endocrine abnormality is characterized by the following changes in PTH, Ca2+, and inorganic phosphate (Pi)?
• PTH increased, Ca2+ increased, Pi decreased
Primary hyperparathyroidism
What is the amount in liters and percent body weight for the following compartments?
• ECF
14 L, 33% of body weight
What is the amount in liters and percent body weight for the following compartments?
• Interstitial fluid
9.3 L, 15% of body weight
What is the amount in liters and percent body weight for the following compartments?
• ICF
28 L, 40% of body weight
What is the amount in liters and percent body weight for the following compartments?
• Vascular fluid
4.7 L, 5% of body weight
What is the amount in liters and percent body weight for the following compartments?
• Total body water
42 L, 67% of body weight
What hormone is secreted by the placenta late in pregnancy, stimulates mammary growth during pregnancy, mobilizes energy stores from the mother so that the fetus can use them, and has an amino acid sequence like GH?
Human chorionic somatomammotropin (hCS) or human placental lactogen (hPL)
What thyroid abnormality has the following?
• TRH decreased, TSH decreased, T4 increased
Secondary hyperthyroidism (Increased TSH results in increased T4 production and increased negative feedback on to hypothalamus and decreased release of TRH.)
What thyroid abnormality has the following?
• TRH increased, TSH decreased, T4 decreased
Secondary hypothyroidism/pituitary (Low TSH results in low T4 and increased TRH because of lack of a negative feedback loop.)
What thyroid abnormality has the following?
• TRH decreased, TSH decreased, T4 decreased
Tertiary hypothyroidism/hypothalamic (Low TRH causes all the rest to be decreased because of decreased stimulation.)
What thyroid abnormality has the following?
• TRH increased, TSH increased, T4 decreased
Primary hypothyroidism (Low T4 has a decreased negative feedback loop, resulting in both the hypothalamus and the anterior pituitary gland to increase TRH and TSH release, respectively.)
What two stress hormones are under the permissive action of cortisol?
Glucagon and epinephrine
If the radius of a vessel doubles, what happens to resistance?
The resistance will decrease one-sixteenth of the original resistance.
What prevents the down-regulation of the receptors on the gonadotrophs of the anterior pituitary gland?
The pulsatile release of GnRH
True or false? Epinephrine has proteolytic metabolic effects.
False. It has glycogenolytic and lipolytic actions but not proteolytic.
What is the only 17-hydroxysteroid with hormonal activity?
Cortisol, a 21-carbon steroid, has a -OH group at position 17.
Does the oncotic pressure of plasma promote filtration or reabsorption?
The oncotic pressure of plasma promotes reabsorption and is directly proportional to the filtration fraction.
Why is the base of the lung hyperventilated when a person is standing upright?
The alveoli at the base are small and very compliant, so there is a large change in their size and volume and therefore a high level of alveolar ventilation.
By removing Na+ from the renal tubule and pumping it back into the ECF compartment, what does aldosterone do to the body's acid-base stores?
The removal of Na+ results in the renal tubule becoming negatively charged. The negative luminal charge attracts both K+ and H+ into the renal tubule and promotes HCO3- to enter the ECF and results in hypokalemic alkalosis.
What hormone causes contractions of smooth muscle, regulates interdigestive motility, and prepares the intestine for the next meal?
Motilin
What two vessels in fetal circulation have the highest PO2 levels?
Umbilical vein and ductus venosus (80%)
How many days prior to ovulation does estradiol peak in the menstrual cycle?
2 days prior to ovulation
What serves as a marker of endogenous insulin secretion?
C-peptide levels
What is the term for the total volume of air moved in and out of the respiratory system per minute?
Total ventilation (minute ventilation or minute volume)
What is the renal compensation mechanism for alkalosis?
Increase in urinary excretion of HCO3-, shifting the reaction to the right and increasing H+
What is a sign of a Sertoli cell tumor in a man?
Excess estradiol in the blood
In the systemic circulation, what blood vessels have the largest pressure drop? Smallest pressure drop?
Arterioles have the largest drop, whereas the vena cava has the smallest pressure drop in systemic circulation.
What is the major stimulus for cell division in chondroblasts?
IGF-1
What are two causes of diffusion impairment in the lungs?
Decrease in surface area and increase in membrane thickness (Palv O2 > PaO2)
What are the four effects of suckling on the mother?
1. Increased synthesis and secretion of oxytocin
2. Increased release of PIF by the hypothalamus
3. Inhibition of GnRH (suppressing FSH/LH)
4. Milk secretion
A migrating myoelectric complex is a propulsive movement of undigested material of undigested material from the stomach to the small intestine to the colon. During a fast, what is the time interval of its repeats?
It repeats every 90 to 120 minutes and correlates with elevated levels of motilin.
With an increase in arterial systolic pressure, what happens to
• Stroke volume?
Increases
With an increase in arterial systolic pressure, what happens to
• Vessel compliance?
Decreases
With an increase in arterial systolic pressure, what happens to
• Heart rate?
Decreases
What enzyme is needed to activate the following reactions?
• Trypsinogen to trypsin
Enterokinase
What enzyme is needed to activate the following reactions?
• Chymotrypsinogen to chymotrypsin
Trypsin
What enzyme is needed to activate the following reactions?
• Procarboxypeptidase to carboxypeptidase
Trypsin
In a ventricular pacemaker cell, what phase of the action potential is affected by ACh?
Phase 4; ACh hyperpolarizes the cell via increasing potassium conductance, taking longer to reach threshold and slowing the rate of firing.
What is the most potent stimulus for glucagon secretion? Inhibition?
Hypoglycemia for secretion and hyperglycemia for inhibition
What is the term for the summation of mechanical stimuli due to the skeletal muscle contractile unit becoming saturated with calcium?
Tetany
What form of renal tubular reabsorption is characterized by low back leaks, high affinity of a substance, and easy saturation? It is surmised that the entire filtered load is reabsorbed until the carriers are saturated, and then the rest is excreted.
A transport maximum (Tm) system
In an adrenergic nerve terminal, where is dopamine converted to NE? By what enzyme?
Dopamine is converted into NE in the vesicle via the enzyme dopamine-Beta-hydroxylase.
Is the clearance for a substance greater than or less than for inulin if it is freely filtered and secreted? If it is freely filtered and reabsorbed?
Filtered and secreted: Cx > Cin (i.e., PAH). Filtered and reabsorbed: Cx < Cin (i.e., glucose), where Cx = clearance of a substance and Cin = clearance of inulin.
What is the term for the load on a muscle in the relaxed state?
Preload. It is the load on a muscle Prior to contraction.
The surge of what hormone induces ovulation?
LH
What are the two best indices of left ventricular preload?
LVEDV and LVEDP (left ventricular end-diastolic volume and end-diastolic pressure, respectively)
What stage of male development is characterized by the following LH and testosterone levels?
• LH pulsatile amplitude and levels increase, with increased testosterone production.
Puberty
What stage of male development is characterized by the following LH and testosterone levels?
• Both LH and testosterone levels drop and remain low.
Childhood
What stage of male development is characterized by the following LH and testosterone levels?
• LH secretion drives testosterone production, with both levels paralleling each other.
Adulthood
What stage of male development is characterized by the following LH and testosterone levels?
• Decreased testosterone production is accompanied by an increase in LH production.
Aged adult
What primary acid-base disturbance is caused by a loss in fixed acid forcing the reaction to shift to the right, thereby increasing HCO3- levels?
Metabolic alkalosis (summary: high pH, low H+ and high HCO3-)
When referring to a series circuit, what happens to resistance when a resistor is added?
Resistance increases as resistors are added to the circuit.
Why is there an increase in prolactin if the hypothalamic-pituitary axis was severed?
Because the chronic inhibition of dopamine (PIF) on the release of prolactin from the anterior pituitary gland is removed, thereby increasing the secretion of prolactin.
Why is the clearance of creatinine always slightly greater than the clearance of inulin and GFR?
Because creatinine is filtered and a small amount is secreted
What acid form of H+ in the urine cannot be titrated?
NH4+(ammonium)
Regarding the venous system, what happens to blood volume if there is a small change in pressure?
Because the venous system is more compliant than the arterial vessels, small changes in pressure result in large changes in blood volume.
In what stage of sleep is GH secreted?
Stages 3 and 4 (NREM)
Where does the conversion of CO2 into HCO3- take place?
In the RBC; remember, you need carbonic anhydrase for the conversion, and plasma does not have this enzyme.
From the fourth month of fetal life to term, what secretes the progesterone and estrogen to maintains the uterus?
The placenta
What two factors are required for effective exocytosis?
Calcium and ATP are required for packaged macromolecules to be extruded from the cell.
What is the best measure of total body vitamin D if you suspect a deficiency?
Serum 25-hydroxy-vitamin D (25-OH-D)
What hormone is required for 1, 25-dihydroxy-vitamin D (1, 25-diOH-D) to have bone resorbing effects?
PTH
Is bone deposition or resorption due to increased interstitial Ca2+concentrations?
Bone deposition increases with increased Ca2+ or PO 4- concentrations, whereas resorption (breakdown) is increased when there are low levels of Ca2+ or PO4-.
The opening of what valve indicates the termination of isovolumetric relaxation phase of the cardiac cycle?
Opening of the mitral valve indicates the termination of the isovolumetric relaxation phase and the beginning of the ventricular filling phase.
Why is there a decrease in the production in epinephrine when the anterior pituitary gland is removed?
The enzyme phenyl ethanolamine N-methyltransferase (PNMT), used in the conversion of epinephrine, is regulated by cortisol. Removing the anterior pituitary gland decreases ACTH and therefore cortisol.
Name the period described by the following statement: no matter how strong a stimulus is, no further action potentials can be stimulated.
Absolute refractory period is due to voltage inactivation of sodium channels.
How many carbons do estrogens have?
Estrogens are 18-carbon steroids. (Removal of one carbon from an androgen produces an estrogen.)
True or false? The alveolar PO2 and PCO2 levels match the pulmonary end capillary blood levels.
True. Because of intrapulmonary shunting, there is a slight decrease in PO2 and increase in PCO2 between the pulmonary end capillary blood and the systemic arterial blood.
In high altitudes, what is the main drive for ventilation?
The main drive shifts from central chemoreceptors (CSF H+) to peripheral chemoreceptors monitoring low PO2 levels.
Describe what type of fluid is either gained or lost with the following changes in body hydration for the ECF volume, ICF volume, and body osmolarity, respectively:
• ECF, decrease; ICF, no change; body, no change
Loss of isotonic fluid (diarrhea, vomiting, hemorrhage)
Describe what type of fluid is either gained or lost with the following changes in body hydration for the ECF volume, ICF volume, and body osmolarity, respectively:
• ECF, increase; ICF, increase; body, decrease
Gain of hypotonic fluid (water intoxication or hypotonic saline)
Describe what type of fluid is either gained or lost with the following changes in body hydration for the ECF volume, ICF volume, and body osmolarity, respectively:
• ECF, decrease; ICF, decrease; body: increase
Loss of hypotonic fluid (alcohol, diabetes insipidus, dehydration)
Describe what type of fluid is either gained or lost with the following changes in body hydration for the ECF volume, ICF volume, and body osmolarity, respectively:
• ECF: increase; ICF: no change; body: no change
Gain of isotonic fluid (isotonic saline)
Describe what type of fluid is either gained or lost with the following changes in body hydration for the ECF volume, ICF volume, and body osmolarity, respectively:
• ECF, increase; ICF, decrease; body, increase
Gain of hypertonic fluid (mannitol or hypertonic saline)
What hormone excess produces adrenal hyperplasia?
ACTH
Is there more circulating T3 or T4 in plasma?
T4; because of the greater affinity for the binding protein, T4 has a significantly (nearly fifty times) longer half-life than T3.
Why is the cell's resting membrane potential negative?
The resting membrane potential of the cell is -90 mV because of the intracellular proteins.
True or false? Thyroid size is a measure of its function.
False. Thyroid size is a measure of TSH levels (which are goitrogenic).
If the radius of a vessel is decreased by half, what happens to the resistance?
The resistance increases 16-fold.
What neurotransmitter is essential for maintaining a normal BP when an individual is standing?
NE, via its vasoconstrictive action on blood vessels
What form of diabetes insipidus is due to an insufficient amount of ADH for the renal collecting ducts?
Central/neurogenic diabetes insipidus; in the nephrogenic form there is sufficient ADH available, but the renal collecting ducts are impermeable to its actions.
Name the three methods of vasodilation via the sympathetic nervous system.
1. Decrease alpha-1 activity
2. Increase Beta-2 activity
3. Increase ACh levels
What hormone is characterized by the following renal effects?
• Calcium reabsorption, phosphate excretion
PTH
What hormone is characterized by the following renal effects?
• Calcium excretion, phosphate excretion
Calcitriol
What hormone is characterized by the following renal effects?
• Calcium reabsorption, phosphate reabsorption
Vitamin D3
True or false? Progesterone has thermogenic activities.
True. Elevated plasma levels of progesterone can raise the body temperature 0.5° to 1.0°F.
How long is the transit time through the small intestine?
2 to 4 hours
Where is the last conducting zone of the lungs?
Terminal bronchioles. (No gas exchange occurs here.)
True or false? Cortisol inhibits glucose uptake in skeletal muscle.
True; cortisol inhibits glucose uptake in most tissue, making it available for neural tissue use.
What percentage of cardiac output flows through the pulmonary circuit?
100%; the percentage of blood flow through the pulmonary and systemic circulations are equal.
Name the Hgb-O2 binding site based on the following information:
• Least affinity for O2; requires the highest PO 2 levels for attachment (approx. 100 mm Hg)
Site 4
Name the Hgb-O2 binding site based on the following information:
• Greatest affinity of the three remaining sites for attachment; requires PO2 levels of 26 mm Hg to remain attached
Site 2
Name the Hgb-O2 binding site based on the following information:
• Remains attached under most physiologic conditions
Site 1
Name the Hgb-O2 binding site based on the following information:
• Requires a PO2 level of 40 mm Hg to remain attached
Site 3
Which three factors cause the release of epinephrine from the adrenal medulla?
1. Exercise
2. Emergencies (stress)
3. Exposure to cold


(The three Es)
How many ATPs are hydrolyzed every time a skeletal muscle cross-bridge completes a single cycle?
One, and it provides the energy for mechanical contraction.
Why would a puncture to a vein above the heart have the potential to introduce air into the vascular system?
Venous pressure above the heart is subatmospheric, so a puncture there has the potential to introduce air into the system.
What type of saliva is produced under parasympathetic stimulation?
High volume, watery solution; sympathetic stimulation results in thick, mucoid saliva.
In what area of the GI tract does iron get absorbed?
Duodenum
Why is the apex of the lung hypoventilated when a person is standing upright?
The alveoli at the apex are almost completely inflated prior to inflation, and although they are large, they receive low levels of alveolar ventilation.
What pancreatic islet cell secretes glucagons?
alpha-Cells; glucagon has stimulatory effects on -cells and inhibitory effects on -cells.
What are the four characteristics of all protein-mediated transportation?
1. Competition for carrier with similar chemical substances
2. Chemical specificity needed for transportation
3. Zero-order saturation kinetics (Transportation is maximal when all transporters are saturated.)
4. Rate of transportation faster than if by simple diffusion
What is secretin's pancreatic action?
Secretin stimulates the pancreas to secrete a HCO3--rich solution to neutralize the acidity of the chyme entering the duodenum.
Why is there an increase in FF if the GFR is decreased under sympathetic stimulation?
Because RPF is markedly decreased, while GFR is only minimally diminished; this results in an increase in FF (remember FF = GFR/RPF).
What triggers phase 3 of the action potential in a ventricular pacemaker cell?
Rapid efflux of potassium
What is the primary target for the action of glucagon?
Liver (hepatocytes)
What is the renal compensation mechanism for acidosis?
Production of HCO3-, shifting the reaction to the left and thereby decreasing H+
What enzyme found in a cholinergic synapse breaks down ACh? What are the byproducts?
Acetylcholinesterase breaks ACh into acetate and choline (which gets resorbed by the presynaptic nerve terminal).
What hormone, produced by Sertoli cells, if absent would result in the formation of internal female structures?
MIF
What happens to the lung if the intrapleural pressure exceeds lung recoil?
The lung will expand; also the opposite is true.
What two factors determine the clearance of a substance?
Plasma concentration and excretion rate
What type of muscle contraction occurs when the muscle shortens and lifts the load placed on it?
Isotonic contraction
What type of potential is characterized as being an all-or-none response, propagated and not summated?
Action potential
What primary acid-base disturbance is caused by a gain in fixed acid forcing the reaction to shift to the left, decreasing HCO3- and slightly increasing CO2?
Metabolic acidosis (summary: low pH, high H+, and low HCO3-)
What two pituitary hormones are produced by acidophils?
GH and prolactin are produced by acidophils; all others are by basophils.
What organ of the body has the smallest AV oxygen difference?
The renal circulation has the smallest AV O2 (high venous PO2) difference in the body because of the overperfusion of the kidneys resulting from filtration.
What is the titratable acid form of H+ in the urine?
H2PO4- (dihydrogen phosphate)
What hypothalamic hormone is synthesized in the preoptic nucleus?
GnRH
What five factors promote turbulent flow?
1. Increased tube radius
2. Increased velocity
3. Decreased viscosity
4. Increased number of branches
5. Narrowing of an orifice
What is the major hormone produced in the following areas of the adrenal cortex?
• Zona glomerulosa
Aldosterone

Remember, from the outer cortex to the inner layer, Salt, Sugar, Sex. The adrenal cortex gets sweeter as you go deeper.
What is the major hormone produced in the following areas of the adrenal cortex?
• Zona fasciculata
Cortisol

Remember, from the outer cortex to the inner layer, Salt, Sugar, Sex. The adrenal cortex gets sweeter as you go deeper.
What is the major hormone produced in the following areas of the adrenal cortex?
• Zona reticularis
DHEA (androgens)

Remember, from the outer cortex to the inner layer, Salt, Sugar, Sex. The adrenal cortex gets sweeter as you go deeper.
Where is most of the body's Ca2+ stored?
In bone; nearly 99% of Ca2+ is stored in the bone as hydroxyapatite.
What is the relationship between ventilation and PCO2 levels?
They are inversely related. If ventilation increases, there will be a decrease in PCO2 levels and vice versa.
Is T3 or T4 responsible for the negative feedback loop on to the hypothalamus and anterior pituitary gland?
T4, as long as T4 levels remain constant, TSH will be minimally effected by T3.
What is the signal to open the voltage-gated transmembrane potassium channels?
Membrane depolarization is the stimulus to open these slow channels, and if they are prevented from opening, it will slow down the repolarization phase.
Increased urinary excretion of what substance is used to detect excess bone demineralization?
Hydroxyproline
What is the term to describe how easily a vessel stretches?
Compliance (think of it as distensibility)
What is the ratio of T4:T3 secretion from the thyroid gland?
20:1T4T3. There is an increase in the production of T3 when iodine becomes deficient.
Do the PO2 peripheral chemoreceptors of the carotid body contribute to the normal drive for ventilation?
Under normal resting conditions no, but they are strongly stimulated when PO2 arterial levels decrease to 50 to 60 mm Hg, resulting in increased ventilatory drive.
What determines the overall force generated by the ventricular muscle during systole?
The number of cross-bridges cycling during contraction: the greater the number, the greater the force of contraction.
Where does most circulating plasma epinephrine originate?
From the adrenal medulla; NE is mainly derived from the postsynaptic sympathetic neurons.
What causes a skeletal muscle contraction to terminate?
When calcium is removed from troponin and pumped back into the SR, skeletal muscle contraction stops.
What happens to intracellular volume when there is an increase in osmolarity?
ICF volume decreases when there is an increase in osmolarity and vice versa.
Which CHO is independently absorbed from the small intestine?
Fructose; both glucose and galactose are actively absorbed via secondary active transport.
When is the surface tension the greatest in the respiratory cycle?
Surface tension, the force to collapse the lung, is greatest at the end of inspiration.
What adrenal enzyme deficiency results in hypertension, hypernatremia, increased ECF volume, and decreased adrenal androgen production?
17-alpha-Hydroxylase deficiency
In reference to membrane potential (Em) and equilibrium potential (Ex), which way do ions diffuse?
Ions diffuse in the direction to bring the membrane potential toward the equilibrium potential.
Under normal conditions, what is the main factor that determines GFR?
Hydrostatic pressure of the glomerular capillaries (promotes filtration)
The closure of what valve indicates the beginning of the isovolumetric relaxation phase of the cardiac cycle?
Closure of the aortic valve indicates the termination of the ejection phase and the beginning of the isovolumetric relaxation phase of the cardiac cycle.
What vessels in the systemic circulation have the greatest and slowest velocity?
The aorta has the greatest velocity and the capillaries have the slowest velocity.
Thin extremities, fat collection on the upper back and abdomen, hypertension, hypokalemic alkalosis, acne, hirsutism, wide purple striae, osteoporosis, hyperlipidemia, hyperglycemia with insulin resistance, and protein depletion are all characteristics o
Hypercortisolism (Cushing syndrome)
What enzyme is essential for the conversion of CO2 to HCO3-?
Carbonic anhydrase
True or false? The parasympathetic nervous system has very little effect on arteriolar dilation or constriction.
True
What three lung measurements must be calculated because they cannot be measured by simple spirometry?
TLC, FRC, and RV have to be calculated. (Remember, any volume that has RV as a component has be calculated.)
What is the venous and arterial stretch receptors' function regarding the secretion of ADH?
They chronically inhibit ADH secretion; when there is a decrease in the blood volume, the stretch receptors send fewer signals, and ADH is secreted.
What cell converts androgens to estrogens?
Granulosa cell
What hormone acts on Granulosa cells?
FSH
How long is the transit time through the large intestine?
3 to 4 days
Does subatmospheric pressure act to expand or collapse the lung?
Subatmospheric pressure acts to expand the lung; positive pressure acts to collapse the lung.
What hormone constricts afferent and efferent arterioles (efferent more so) in an effort to preserve glomerular capillary pressure as the renal blood flow decreases?
AT II
Why is there a minimal change in BP during exercise if there is a large drop in TPR?
Because the large drop in TPR is accompanied by a large increase in cardiac output, resulting in a minimal change in BP.
What is the effect of insulin on protein storage?
Insulin increases total body stores of protein, fat, and CHOs. When you think insulin, you think storage.
What is the term for an inhibitory interneuron?
Renshaw neuron
What triggers phase 0 of the action potential in a ventricular pacemaker cell?
Calcium influx secondary to slow channel opening
What are the following changes seen in the luminal fluid by the time it leaves the PCT of the nephron?
• Percentage of original filtered volume left in the lumen
At the end of the PCT 25% of the original volume is left
What are the following changes seen in the luminal fluid by the time it leaves the PCT of the nephron?
• Percentage of Na+, Cl-, K+ left in the lumen
At the end of the PCT 25% of Na+, Cl-, K+ is left
What are the following changes seen in the luminal fluid by the time it leaves the PCT of the nephron?
• Osmolarity
300 mOsm/L
What are the following changes seen in the luminal fluid by the time it leaves the PCT of the nephron?
• Concentration of CHO, AA, ketones, peptides
No CHO, AA, ketones, or peptides are left in the tubular lumen.
True or false? Enterokinase is a brush border enzyme.
False. It is an enzyme secreted by the lining of the small intestine.
Where does the synthesis of ACh occur?
In the cytoplasm of the presynaptic nerve terminal; it is catalyzed by choline acetyltransferase.
What pancreatic islet cell secretes somatostatin?
delta-Cells; somatostatin has an inhibitory effect on alpha- and Beta-islet cells.
Why is O2 content depressed in anemic patients?
Anemic patients have a depressed O2 content because of the reduced concentration of Hgb in the blood. As for polycythemic patients, their O2 content is increased because of the excess Hgb concentrations.
What term describes the volume of plasma from which a substance is removed over time?
Clearance
If capillary hydrostatic pressure is greater than oncotic pressure, is filtration or reabsorption promoted?
Filtration; if hydrostatic pressure is less than oncotic pressure, reabsorption is promoted.
What cells of the parathyroid gland are simulated in response to hypocalcemia?
The chief cells of the parathyroid gland release PTH in response to hypocalcemia.
At the base of the lung, what is the baseline intrapleural pressure, and what force does it exert on the alveoli?
Intrapleural pressure at the base is -2.5 cm H2O (more positive than the mean), resulting in a force to collapse the alveoli.
What hormone is necessary for normal GH secretion?
Normal thyroid hormones levels in the plasma are necessary for proper secretion of GH. Hypothyroid patients have decreased GH secretions.
What is the signal to open the voltage-gated transmembrane sodium channels?
Membrane depolarization is the stimulus to open these channels, which are closed in resting conditions.
What hormones are produced in the median eminence region of the hypothalamus and the posterior pituitary gland?
None; they are the storage sites for ADH and oxytocin.
What is the most energy-demanding phase of the cardiac cycle?
Isovolumetric contraction
What presynaptic receptor does NE use to terminate further neurotransmitter release?
alpha2-Receptors
Are salivary secretions hypertonic, hypotonic, or isotonic?
Hypotonic, because NaCl is reabsorbed in the salivary ducts
What is the effect of T3 on heart rate and cardiac output?
T3 increases both heart rate and cardiac output by increasing the number of Beta-receptors and their sensitivity to catecholamines.
Why will turbulence first appear in the aorta in patients with anemia?
Because it is the largest vessel and has the highest velocity in systemic circulation
What is the origin of the polyuria if a patient is dehydrated and electrolyte depleted?
If the polyuria begins before the collecting ducts, the patient is dehydrated and electrolyte depleted. If the polyuria originates from the collecting ducts, the patient is dehydrated with normal electrolytes.
What is the physiologically active form of Ca2+?
Free ionized Ca2+
What are the two factors that affect alveolar PCO2 levels?
Metabolic rate and alveolar ventilation (main factor)
Why is spermatogenesis decreased with anabolic steroid therapy?
Exogenous steroids suppress LH release and result in Leydig cell atrophy. Testosterone, produced by Leydig cells, is needed for spermatogenesis.
What type of membrane is characterized as being permeable to water only?
Semipermeable membrane; a selectively permeable membrane allows both water and small solutes to pass through its membrane.
What thyroid enzyme is needed for oxidation of I– to I'?
Peroxidase, which is also needed for iodination and coupling inside the follicular cell
What is the most important stimulus for the secretion of insulin?
An increase in serum glucose levels
What term is described as the prestretch on the ventricular muscle at the end of diastole?
Preload (the load on the muscle in the relaxed state)

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