Pesyow New-row Flashcards
Which autonomic receptor is blocked by hexamethonium at the ganglia, but
not at the neuromuscular junction?
A) Adrenergic α1 receptors
(B) Adrenergic β1 receptors
(C) Adrenergic β2 receptors
(D) Cholinergic muscarinic receptors
(E) Cholinergic nicotinic receptors
Answer : E
Hexamethonium is a nicotinic blocker, but it acts only at ganglionic (not neuromuscular junction) nicotinic receptors. This pharmacologic distinction emphasizes that nicotinic receptors at these two locations, although similar, are not identical.
A 66-year-old man with chronic hypertension is treated with prazosin by his physician. The treatment successfully decreases his blood pressure to within
the normal range. What is the mechanism of the drug’s action?
Ans :
Inhibition of α1 receptors on vascular smooth muscle
Prazosin is a specific antagonist of α1
receptors, which are present in vascular smooth muscle, but not in the heart.Inhibition of α1 receptors results in vasodilation of the cutaneous and splanchnic vascular beds, decreased total peripheral resistance, and decreased blood
pressure.
Which of the following responses is mediated by parasympathetic muscarinic receptors?
A) Dilation of bronchiolar smooth muscle
(B) Miosis
(C) Ejaculation
(D) Constriction of gastrointestinal (GI) sphincters
(E) Increased cardiac contractility
B) Miosis
Miosis is a parasympathetic muscarinic
response that involves contraction of the circular muscle of the iris. Dilation of
the bronchioles, ejaculation, constriction of the gastrointestinal (GI) sphincters,
and increased cardiac contractility are all sympathetic α or β responses.
Which of the following is a property of C fibers?
(A) Have the slowest conduction velocity of any nerve fiber type
(B) Have the largest diameter of any nerve fiber type
(C) Are afferent nerves from muscle spindles
(D) Are afferent nerves from Golgi tendon organs
(E) Are preganglionic autonomic fibers
(A) Have the slowest conduction velocity of any nerve fiber type
C fibers (slow pain) are the smallest nerve fibers and therefore have the slowest conduction velocity
- When compared with the cones of the retina, the rods
(A) are more sensitive to low-intensity light
(B) adapt to darkness before the cones
(C) are most highly concentrated on the fovea
(D) are primarily involved in color vision
A) are more sensitive to low-intensity light
Of the two types of photoreceptors,
the rods are more sensitive to low-intensity light and therefore are more important than the cones for night vision. They adapt to darkness after the cones.Rods are not present in the fovea. The cones are primarily involved in color vision.
Which of the following statements best describes the basilar membrane of the organ of Corti?
(A) The apex responds better to low frequencies than the base does
(B) The base is wider than the apex
(C) The base is more compliant than the apex
(D) High frequencies produce maximal displacement of the basilar membrane
near the helicotrema
(E) The apex is relatively stiff compared to the base
A. The apex responds better to low frequencies than the base does
- Sound frequencies can be encoded by the organ of
Corti because of differences in properties along the basilar membrane. The base of the basilar membrane is narrow and stiff, and hair cells on it are activated by high frequencies. The apex of the basilar membrane is wide and compliant, and hair cells on it are activated by low frequencies
Which of the following is a feature of the sympathetic, but not the
parasympathetic nervous system?
(A) Ganglia located in the effector organs
(B) Long preganglionic neurons
(C) Preganglionic neurons release norepinephrine
D) Preganglionic neurons release acetylcholine (ACh)
(E) Preganglionic neurons originate in the thoracolumbar spinal cord
(F) Postganglionic neurons synapse on effector organs
(G) Postganglionic neurons release epinephrine
(H) Postganglionic neurons release ACh
E) Preganglionic neurons originate in the thoracolumbar spinal cord
~ Sympathetic preganglionic
neurons originate in spinal cord segments T1–L3. Thus, the designation isthoracolumbar. The sympathetic nervous system is further characterized by short preganglionic neurons that synapse in ganglia located in the paravertebral chain(not in the effector organs) and postganglionic neurons that release norepinephrine (not epinephrine). Common features of the sympathetic and parasympathetic nervous systems are preganglionic neurons that release acetylcholine (ACh) and postganglionic neurons that synapse in effector organs.
8. Which autonomic receptor mediates an increase in heart rate? (A) Adrenergic α1 receptors (B) Adrenergic β1 receptors (C) Adrenergic β2 receptors (D) Cholinergic muscarinic receptors (E) Cholinergic nicotinic receptors
Adrenergic β1 receptors.
Heart rate is increased by the stimulatory effect of
norepinephrine on β1 receptors in the sinoatrial (SA) node. There are also
sympathetic β1 receptors in the heart that regulate contractility
9. Cutting which structure on the left side causes total blindness in the left eye? (A) Optic nerve (B) Optic chiasm (C) Optic tract (D) Geniculocalcarine tract
A) Optic nerve
Which reflex is responsible for monosynaptic excitation of ipsilateral
homonymous muscle?
(A) Stretch reflex (myotatic)
(B) Golgi tendon reflex (inverse myotatic)
(C) Flexor withdrawal reflex
(D) Subliminal occlusion reflex
A) Stretch reflex (myotatic)
The stretch reflex is the monosynaptic response
to stretching of a muscle. The reflex produces contraction and then shortening of
the muscle that was originally stretched (homonymous muscle)
Which type of cell in the visual cortex responds best to a moving bar of light? (A) Simple (B) Complex (C) Hypercomplex (D) Bipolar (E) Ganglion
Complex
-Complex cells respond to moving bars or
edges with the correct orientation. Simple cells respond to stationary bars, and
hypercomplex cells respond to lines, curves, and angles. Bipolar and ganglion
cells are found in the retina, not in the visual cortex.
Administration of which of the following drugs is contraindicated in a 10- year-old child with a history of asthma? (A) Albuterol (B) Epinephrine (C) Isoproterenol (D) Norepinephrine (E) Propranolol
E) Propranolol
Asthma, a disease involving increased
resistance of the upper airways, is treated by administering drugs that produce bronchiolar dilation (i.e., β2 agonists). β2 Agonists include isoproterenol,albuterol, epinephrine, and, to a lesser extent, norepinephrine. β2 Antagonists,
such as propranolol,
Which adrenergic receptor produces its stimulatory effects by the formation of inositol 1,4,5-triphosphate (IP3) and an increase in intracellular [Ca2+]? (A) α1 Receptors (B) α2 Receptors (C) β1 Receptors (D) β2 Receptors (E) Muscarinic receptors (F) Nicotinic receptors
α1 Receptors.
Adrenergic α1 receptors produce physiologic actions by stimulating the formation of inositol 1,4,5-triphosphate (IP3) and causing a subsequent increase in intracellular [Ca2+]. Both β1 and β2 receptors act by stimulating adenylate cyclase and increasing the production of cyclic adenosine monophosphate (cAMP). α2 Receptors inhibit adenylate cyclase and decrease cAMP levels. Muscarinic and nicotinic receptors are cholinergic
- The excessive muscle tone produced in decerebrate rigidity can be reversed
by
(A) stimulation of group Ia afferents
(B) cutting the dorsal roots
(C) transection of cerebellar connections to the lateral vestibular nucleus
(D) stimulation of α-motoneurons
(E) stimulation of γ-motoneurons
B) cutting the dorsal roots.
Decerebrate rigidity is caused by increased reflex muscle spindle activity. Stimulation of group Ia afferents would enhance,not diminish, this reflex activity. Cutting the dorsal roots would block the reflexes. Stimulation of α- and γ-motoneurons would stimulate muscles directly
- Which of the following parts of the body has cortical motoneurons with the
largest representation on the primary motor cortex (area 4)?
(A) Shoulder
(B) Ankle
(C) Fingers
(D) Elbow
(E) Knee
Representation on the motor homunculus is
greatest for those structures that are involved in the most complicated
movements—the fingers, hands, and face.
Which autonomic receptor mediates secretion of epinephrine by the
adrenal medulla?
Cholinergic nicotinic receptors
- Preganglionic sympathetic fibers
synapse on the chromaffin cells of the adrenal medulla at a nicotinic receptor.Epinephrine and, to a lesser extent, norepinephrine are released into the circulation.
Cutting which structure on the right side causes blindness in the temporal field of the left eye and the nasal field of the right eye?
Optic tract
A ballet dancer spins to the left. During the spin, her eyes snap quickly to
the left. This fast eye movement is
nystagmus.
-The fast eye movement that occurs during a spin
is nystagmus. It occurs in the same direction as the rotation. After the spin,
postrotatory nystagmus occurs in the opposite direction.
Which of the following has a much lower concentration in the cerebrospinal fluid (CSF) than in cerebral capillary blood?
Protein
Cerebrospinal fluid (CSF) is similar in
composition to the interstitial fluid of the brain. Therefore, it is similar to an
ultrafiltrate of plasma and has a very low protein concentration because large
protein molecules cannot cross the blood–brain barrier. There are other
differences in composition between CSF and blood that are created by
transporters in the choroid plexus, but the low protein concentration of CSF is
the most dramatic difference
Which of the following autonomic drugs acts by stimulating adenylate
cyclase?
Norepinephrine
Among the autonomic drugs, only
β1 and β2 adrenergic agonists act by stimulating adenylate cyclase.
Norepinephrine is a β1agonist. Atropine is a muscarinic cholinergic antagonist.
Clonidine is an α2 adrenergic agonist. Curare is a nicotinic cholinergic
antagonist. Phentolamine is an α1 adrenergic antagonist. Phenylephrine is an α1
adrenergic agonist. Propranolol is a β1 and β2 adrenergic antagonist
Which of the following is a step in photoreception in the rods?
Metarhodopsin II activates transducin
-Photoreception involves the following steps. Light
converts 11-cis retinal to all-trans retinal, which is converted to such
intermediates as metarhodopsin II. Metarhodopsin II activates a stimulatory G
protein (transducin), which activates a phosphodiesterase. Phosphodiesterase
breaks down cyclic guanosine monophosphate (cGMP), so intracellular cGMP
levels decrease, causing closure of Na+ channels in the photoreceptor cell
membrane and hyperpolarization. Hyperpolarization of the photoreceptor cell
membrane inhibits release of the neurotransmitter, glutamate. If the decreased
release of glutamate interacts with ionotropic receptors on bipolar cells, there
will be inhibition (decreased excitation). If the decreased release of glutamate
interacts with metabotropic receptors on bipolar cells, there will be excitation
(decreased inhibition).
Pathogens that produce fever cause
shivering
-Pathogens release interleukin-1 (IL-1) from
phagocytic cells. IL-1 then acts to increase the production of prostaglandins,
ultimately raising the temperature set point in the anterior hypothalamus. The
hypothalamus now “thinks” that the body temperature is too low (because the
core temperature is lower than the new set-point temperature) and initiates
mechanisms for generating heat—shivering, vasoconstriction, and shunting of
blood away from the venous plexus near the skin surface.
Which of the following statements about the olfactory system is true?
(A) The receptor cells are neurons
(B) The receptor cells are sloughed off and are not replaced
(C) Axons of cranial nerve (CN) I are A-delta fibers
(D) Axons from receptor cells synapse in the prepiriform cortex
(E) Fractures of the cribriform plate can cause inability to detect ammonia
A. The receptor cells are neurons
A lesion of the chorda tympani nerve would most likely result in
D) impaired taste function
Which of the following would produce maximum excitation of the hair
cells in the right horizontal semicircular canal?
D) Rotating the head to the right
The inability to perform rapidly alternating movements
(dysdiadochokinesia) is associated with lesions of the
cerebellum
Which autonomic receptor is activated by low concentrations of
epinephrine released from the adrenal medulla and causes vasodilation?
Adrenergic β2 receptors
Complete transection of the spinal cord at the level of T1 would most likely result in
temporary loss of stretch reflexes below the lesion
Sensory receptor potentials
are graded in size, depending on stimulus intensity
-Receptor potentials are graded potentials that
may bring the membrane potential of the receptor cell either toward
(depolarizing) or away from (hyperpolarizing) threshold. Receptor potentials are not action potentials, although action potentials (which are all-or-none) may
result if the membrane potential reaches threshold
Cutting which structure causes blindness in the temporal fields of the left and right eyes?
B) Optic chiasm
Optic nerve fibers from both temporal receptor
fields cross at the optic chiasm
Which of the following structures has a primary function to coordinate
rate, range, force, and direction of movement?
Cerebellum
-Output of Purkinje cells from the cerebellar
cortex to deep cerebellar nuclei is inhibitory. This output modulates movement
and is responsible for the coordination that allows one to “catch a fly.”
Which reflex is responsible for polysynaptic excitation of contralateral
extensors?
(C) Flexor withdrawal reflex
-Flexor withdrawal is a polysynaptic reflex that is
used when a person touches a hot stove or steps on a tack. On the ipsilateral side
of the painful stimulus, there is flexion (withdrawal); on the contralateral side,
there is extension to maintain balance.
Which of the following is a characteristic of nuclear bag fibers?
They detect dynamic changes in muscle length
Nuclear bag fibers are one type of intrafusal
muscle fiber that make up muscle spindles. They detect dynamic changes in
muscle length, give rise to group Ia afferent fibers, and are innervated by γ-
motoneurons. The other type of intrafusal fiber, the nuclear chain fiber, detects
static changes in muscle length.
Muscle stretch leads to a direct increase in firing rate of which type of
nerve?
C) Group Ia fibers
-Group Ia afferent fibers innervate intrafusal
fibers of the muscle spindle. When the intrafusal fibers are stretched, the group
Ia fibers fire and activate the stretch reflex, which causes the muscle to return to
its resting length
A 42-year-old woman with elevated blood pressure, visual disturbances,
and vomiting has increased urinary excretion of 3-methoxy-4-
hydroxymandelic acid (VMA). A computerized tomographic scan shows an
adrenal mass that is consistent with a diagnosis of pheochromocytoma.
While awaiting surgery to remove the tumor, she is treated with
phenoxybenzamine to lower her blood pressure. What is the mechanism of
this action of the drug?
D) Decreasing IP3/Ca2+
Pheochromocytoma is a tumor of
the adrenal medulla that secretes excessive amounts of norepinephrine and
epinephrine. Increased blood pressure is due to activation of α1 receptors on
vascular smooth muscle and activation of β1 receptors in the heart.
Phenoxybenzamine decreases blood pressure by acting as an α1 receptor
antagonist, thus decreasing intracellular IP3/Ca2+
.
Patients are enrolled in trials of a new atropine analogue. Which of the
following would be expected?
A) Increased AV node conduction velocity.
An atropine analogue would block muscarinic
receptors and thus block actions that are mediated by muscarinic receptors.
Muscarinic receptors slow AV node conduction velocity; thus, muscarinic
blocking agents would increase AV node conduction velocity. Muscarinic
receptors increase gastric acid secretion, constrict the pupils, mediate erection,
and cause sweating (via sympathetic cholinergic innervation of sweat glands);
thus, blocking muscarinic receptors will inhibit all of those actions
