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You have a neuron with the following conditions. Internal sodium concentration is 20 mM/L while the external concentration is 130 mM/L. The external potassium concentration is 6 mM/L and the equilibrium potential for potassium is -85 mV. The relative conduction for potassium is 12 times that of sodium. Body temperature is 98.6oF. Assume chloride diffusion is negligible.

What is the resting potential of this cell?

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Deanna Hettinger
Deanna HettingerLv2
28 Sep 2019

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2. Some people have low levels of calcium circulating in the blood, a condition known as hypocalcemia. While for many this disorder has little to no effect, for some it can be life-threatening. How could low levels of calcium harm an individual?
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3. Cephalization is: the
All of these choices are correct.
development of a brain within the head of an animal.
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It results from voltage-gated sodium channels remaining open for long periods of time.
It results from K+ ions diffusing out of the cell.
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5. Afferent and efferent neurons differ in:
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the directionality of the information they send.
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motor neuron.
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stimulating a muscle to contract
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Case 2 (7.5 pts)

R. S., a 55-year-old man, has been admitted to the hospital for treatment of acute gastrointestinal bleed. He is well known to the medical community for his chronic alcohol abuse and encephalopathy.

Past History: R. S. has been hospitalized four times in the past 24 months; most recently he was discharged 12 weeks ago for treatment of upper gastrointestinal bleeding. He has a 40-year history of smoking and drinks an unknown quantity of liquor daily. On previous admissions he has been treated for pancreatitis, alcohol withdrawal seizures, cirrhosis and associated ascites, coagulopathy, esophageal varices, anemia, gastrointestinal bleed, and gastritis.

Current Status: His current problems include hepatic encephalopathy, gastrointestinal bleed, coagulopathy, jaundice, history of tuberculosis (age 15 with treatment), and hypoxia; all present were on previous admission. Medications at last discharge included spironolactone (25 mg twice a day), ranitidine (150 mg twice a day), antacid (Maalox), and multivitamins.

R. S. was found unconscious in a pool of blood and vomitus. He was taken to the hospital and admitted to the medical intensive care unit. Initial vital signs were as follows: blood pressure 90/60, heart rate 112, and respirations 12. Intravenous infusion with normal saline was begun through a central line; oxygen was started at 3 L by nasal cannula. Physical examination revealed icteric sclera, clear lungs, grade Ill/TV systolic ejection murmur, and abdomen soft and without masses, liver percussed at 12 cm below the costal margin, and skin markedly jaundiced. Deep tendon reflexes were brisk and equal bilaterally.
Lab tests revealed the following: sodium 137 mEq/L, potassium 4.8 mEq/L, chloride 102 mEq/L, carbon dioxide 23 mEq/L, blood urea nitrogen 132 mg/dl, creatinine 1.3 mg/dl, glucose 115 mg/dl, hematocrit 27.7%, hemoglobin 9.3 g, white blood cell count 17,800 mm3, platelets 259,000 mm3, direct bilirubin 7.8 mg/dl, total bilirubin 16.4 mg/dl, amylase 42 somogyi units/dl, alkaline phosphatase 127 mu/dl, ammonia level 200 mg. Blood gases were as follows: Po.2 85 mm Hg, PCO2 30 mm Hg, pH 7.35, prothrombin time (PT) patient 17 sec., prothrombin time (PT) control 12.3 sec., partial prothrombin time (PIT) 46/36 sec.
Treatment with blood replacement was initiated; it included transfusion of 6 units fresh frozen plasma and 5 units packed red blood cells, with antacids, ranitidine, vitamin K, thiamine, and lactulose by nasogastric tube.
On the following day R. S.’s mental status was improved and his laboratory studies were as follows: sodium 133 mEq/L. potassium 3.5 mEq/L, chloride 105 mEq/L, blood urea nitrogen 15 mg/dl, creatinine 0.7 mg/dl, glucose 114 mg/dl, hematocrit 38.7%, white blood cell count 5200 mm3, PT 15.7/12 sec., ammonia 93 mg, alkaline phosphatase 92 m/dl. Vital signs were as follows: blood pressure 116/72, heart rate 72, respirations 15, afebrile.
On day 2 he was oriented X3 and was transferred from the intensive care unit. During the course of his hospitalization his total bilirubin ranged from 16.4 mg/dl down to 10.7 mg/dl at discharge.

What is the physiological benefit of having a hepatic portal system?

Does R.S have elevated bilirubin? If yes, does the portion of the total bilirubin that is direct indicate pre hepatic, post hepatic or an intrahepatic problem?

What is ascites? How do hypoalbuminemia and increased serum aldosterone levels contribute to the development of ascites?

Explain the cause of the patients’ clotting defects.

The sclera of R. S.’s eyes are icteric and his skin yellowed. What is the cause of

these discolorations, and what do they indicate about his pathophysiology?

Explain why esophageal varices are the leading cause of death in patients with cirrhosis

Tetraethylammonium (TEA) is a drug that blocks voltage-gated potassium channels. What effect would this have on an action potential?

(a)Prevent the rising phase

(b)Prevent the cell from reaching the threshold to trigger an action potential

(c)Prevent or prolong the falling phase

(d)None of the above

The hyperpolarization phase of the action potential is due to:

(a)The opening of voltage-gated Cl- channels

(b)Prolonged opening of voltage gated K+ channels

(c)The closure of resting Na+ channels

(d)Rapid inactivation of voltage-gated K+ channels

The period when it is difficult to initiate another action potential for several milliseconds due to voltage-gated sodium channel inactivation is referred to as the:

(a)Relative refractory period

(b)Absolute refractory period

(c)Resting period

(d)Hyperpolarization period

In the human central nervous system, Gap junctions are found:

(a)Only between neurons

(b)Only between astrocytes

(c)In both neurons and astrocytes

(d)In all cells

Small molecule transmitters such as acetylcholine are synthesized in:

(a)The nerve terminal

B) The cell body and transported to the nerve terminal

C) Synaptic vesicles

D) Endoplasmic reticulum

Prior to Otto Loewi’s classical experiment, which of the following was not known:

(a)stimulation of the vagus nerve slows the heart

(b)extracts of frog heart, made following vagal nerve stimulation, slow the heart

(c)some acetylcholine effects are similar to those produced by muscarine

(d)vagal nerve stimulation releases a substance which slows the heart

Which of the following is most important in determining if neurotransmission is excitatory or inhibitory?

(a)The structure of the synapse

(b)The neurotransmitter released by the presynaptic neuron

(c)The neurotransmitter receptor

(d)The strength of the stimulus

Benzodiazepines such as Valium allosterically regulate GABA receptors by:

(a)Binding at receptor sites other than the transmitter binding site

(b)Binding at the transmitter (GABA) binding site on the receptor

(c)Blocking the action of the endogenous transmitter

(d)Mimicking the action of the endogenous transmitter

GABA-A receptors are ligand-gated Cl- channels. The equilibrium potential of Cl- is -65 mV. At the neuronal resting membrane potential of -65 mV, GABA binding to the GABA-A receptor would result in the opening the Cl- channel, resulting in:

(a)no net flow of Cl- ions

(b)Cl- inflow and hyperpolarization

(c)Cl- outflow and depolarization

(d)Cl- outflow and hyperpolarization

At the mammalian neuromuscular junction, the released neurotransmitter acts on:

(a)muscarinic receptors

(b)nicotinic receptors

(c)adrenergic receptors

(d)Beta receptors

Neurotransmitters are packaged into synaptic vesicles by:

(a)endocytosis following transmitter release

(b)presynaptic membrane transporters

(c)vesicular transporters

(d)all of the above

. Which of the following are NOT types of ion channels?

Voltage-gated

(a)Ligand-gated

(b)G protein coupled receptor (GPCR)-gated

(c)Leak channels

(d)NONE of the above

NMDA receptors are unique in that their ion channel is:

(a)Ligand-gated

(b)Voltage-gated

(c)Ligand- and voltage-gated ion channels

(d)GPCR-gated

. Which of the following is INCORRECT regarding Catecholamine neurotransmitters

(a)Includes Dopamine, Norepinerphrine, and Epinephrine

(b)Contain a Catechol Ring

(c)Synthesized from Tryptophan

(d)Are produced by neurons whose cell bodies are located in the upper brainstem

The largest and most diverse group of receptors in eukaryotes is:

(a)Ligand gated receptors

(b)Glutamate receptors

(c)G-Protein coupled receptors

(d)Allosteric receptors

The most abundant G-protein coupled receptor in the brain is:

(a)Glutamate receptors

(b)Acetylcholine receptors

(c)Cannabinoid receptors

(d)Dopamine receptors

Which of the following drugs DOES NOT block voltage-gated Na+ channels

(a)Lidocaine

(b)Riluzole

(c)Reserpine

(d)Tetrodotoxin

Sarin, a nerve gas, exerts its toxicity by:

(a)blocking nicotinic receptors

(b)inhibiting choline acetyltransferase

(c)inhibiting acetylcholinesterase

(d)inhibiting voltage-gated Na+ channels

Botulinum Toxin (BoTox) interferes with transmitter release by:

(a)cleaving protein(s) involved in transmitter release

(b)blocking voltage-gated Ca2+ channels

(c)blocking voltage-gated Na+ channels

(d)blocking voltage-gated K+ channels

Atropine is:

(a)An agonist of the acetylcholine ionotropic receptor

(b)An antagonist of the acetylcholine ionotropic receptor

(c)An agonist of the acetylcholine metabotropic receptor

(d)An antagonist of the acetylcholine metabotropic receptor

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