Physiopatho - neuro Flashcards
Which part of a neuron is primarily characterized as the information-receiving component?
a. Axon
b. Presynaptic terminal
c. Cell body
d. Dendrite
e. Myelin
D - dendrite
Almost all neurons have an information-receiving area of the cell membrane, usually composed of radiating dendrites; a cell body, or soma, containing the organelles for most cell metabolic activity; an information-carrying extension of the cell membrane, called an axon; and a presynaptic terminal at the end of the axon to transmit information to other cells. The axon is often covered with a punctuated fatty coating called the myelin sheath that enhances the speed of information (saltatory conduction)
Which of the following is not characteristic of glial cells?
a. Production of action potentials
b. Immune responses of the nervous system
c. Production of the myelin sheaths of axons
d. Modulating the growth of developing or damaged neurons
e. Buffering extracellular concentrations of some ions and neurotransmitters
a - production of action potentials
What’s the value of the resting membrane potential? And what does make it so?
-70 mV
Is the result of the differential separation of charged ions, especially sodium (Na+) and potassium (K+), across the membrane and the resting membrane’s differential permeability to these ions as they attempt to move back down their concentration and electrical gradients. Even though the net concentration of positive and negative charges is similar in both the intracellular and extracellular fluids, an excess of positive charges accumulates immediately outside the cell membrane, and an excess of negative charges accumulates immediately inside the cell membrane, making the resting potential negative.
If the number of IPSPs on the dendritic membrane decreases while the number of EPSPs remains the same, what will happen to the action potentials on that neuron?
a. Probability of triggering action potentials increases.
b. Probability of triggering action potentials decreases.
c. Probability of triggering action potentials remains unchanged. d. Action potentials would be eliminated.
e. Action potentials would be conducted with increased
velocity.
a - Probability of triggering action potentials increases.
During an excitatory postsynaptic potential in a neural mem- brane, which of the following is the most important ion flow?
a. Sodium ions diffuse out of the cell.
b. Sodium ions diffuse into the cell.
c. Potassium ions diffuse out of the cell.+ +
d. Potassium ions pumped in by the Na , K pump. e. None of the above.
b - sodium diffuse into the cell
Describe how the Resting Membrane Potential Can Be Changed by Synaptic Signals From a Presynaptic Cell:
By summation of postsynaptic potentials - either excitatory (EPSP) or inhibitory (IPSP). Summation of several postsynaptic potentials slowly opens voltage-gated Na+ channels and the consequent influx of Na ions (in case of EPSP) - which would eventually lead to depolarisation if continued.
Summation of IPSP instead open chemically gated K+ channels, then K+ ions diffuse out, moving the membrane potential even closer to the equilibrium potential for K+ (−90 mV). This change from the resting potential to a more negative membrane potential is called hyperpolarization.
At the neuromuscular junction, Ca2+ ions are necessary for:
a - Binding the transmitter with the postsynaptic receptor. b - Facilitating diffusion of the transmitter to the postsynaptic membrane.
c - Splitting the transmitter in the cleft, thus deactivating the transmitter.
d - Fusing the presynaptic vesicle with the presynaptic mem- brane, thus releasing the transmitter.
e - Metabolizing the transmitter within the presynaptic vesicle.
d - Fusing the presynaptic vesicle with the presynaptic mem- brane, thus releasing the transmitter.
Which one of the following is true with regard to the termination of synaptic action at the neuromuscular junction?
a. - The reuptake of intact acetylcholine molecules into the
motor neuron terminal is responsible.
b. - Diffusion of acetylcholine away from the synapse is solely
responsible.
c. - Acetylcholinesterase rapidly breaks down acetylcholine into
choline and acetate.
d. - Dissociation of acetylcholine from the muscarinic receptor,
after binding for several seconds, is solely responsible.
c. - Acetylcholinesterase rapidly breaks down acetylcholine into
choline and acetate.
Troponin and tropomyosin are components of which one of the following structures?
a. Myosin thick filament
b. Sarcolemma
c. T tubule
d. Actin thin filament
e. Sarcoplasmic reticulum
a - myosin filament
Action potentials in skeletal muscle cells trigger the release from the sarcoplasmic reticulum of what ion critical to the muscle’s contractile process?
a. Ca2+
b. Na+
c. K+
d. Cl–
e. HCO3–
a - Ca2+
Which one of the following is not found in smooth muscle?
a. Actin filaments
b. Myosin filaments
c. T tubules
d. Voltage-gated calcium channels e. Sarcoplasmic reticulum
c - T tubules
A gross skeletal muscle belly can be instructed (by the central nervous system) to contract more forcefully by:
a. Causing more of its motor units to contract simultaneously.
b. Increasing the amount of acetylcholine released during each
neuromuscular synaptic transmission.
c. Increasing the frequency of action potentials in the α motor
neuron’s axon.
d. Both a and c.
e. Both b and c.
d - both a and c
Which one of the following is an example of a segmental reflex? a. Quadriceps stretch reflex
b. Cutaneous trunci reflex
c. Vestibulospinal postural reflexes
a
An intersegmental reflex arc is one in which:
a. The course of the arc is restricted to one or a small number
of segments of the CNS.
b. No target organ is present.
c. No receptor is present.
d. The course of the arc traverses several segments of the CNS.
e. Both b and c.
d
Activation of the Golgi tendon organ of a given muscle:
a. Monosynaptically produces EPSPs on the α motor neuron
that returns to that muscle.
b. Is most effectively produced by lengthening of the extrafusal
fibers of that muscle.
c. Polysynaptically produces IPSPs on the α motor neuron
that returns to that muscle.
d. Polysynaptically produces EPSPs on the α motor neuron
that returns to that muscle.
e. Activates motor neurons that return to the Golgi tendon
organ itself.
c
Gamma (γ) motor neurons:
a. Innervate and produce contraction of the equatorial
(middle) region of an intrafusal fiber.
b. Have their cell bodies in the dorsal horn of the spinal cord. c. Are never activated at the same time as α motor neurons. d. Can regulate the sensitivity of the muscle spindle sensory
organ.
e. Innervate and regulate the sensitivity of the Golgi tendon
organ.
d
You examine a dog that is bright, alert, and responsive. She can stand and bear weight on both front legs, but she cannot stand or bear any weight on the back legs. Her knee jerk and toe-pinch withdrawal reflexes are normal in all four legs. There is no atrophy. The proprioceptive positioning response is normal in the front legs but absent in both rear legs. Injecting acetylcholinesterase-inhibiting drugs causes no change in the clinical signs. Where is this dog’s pathological lesion most likely located?
a. Neuromuscular junction
b. Cervical spinal cord (spinal cord of the neck)
c. Spinal cord between the front and rear legs (thoracolumbar
spinal cord)
d. Lower motor neurons to the rear legs e. Brainstem
c
You examine a dog that is bright, alert, and responsive but unable to stand on any of the four legs. Toe-pinch and knee jerk local (segmental) reflexes are normal in all four legs. There is no atrophy. The proprioceptive positioning response is absent in all four legs. Injecting an acetylcholinesterase-inhibiting drug does not change the clinical signs. Where is this dog’s pathological lesion most likely located?
a. Cervical spinal cord (spinal cord in the neck)
b. Spinal cord between the front and rear legs (thoracolumbar
spinal cord)
c. Lower motor neurons to all four legs
d. Neuromuscular junction
a
You are presented with a horse that is unable to stand or support any weight on the hind legs. You electrically stimulate both the sciatic and the femoral nerves with a sufficient stimulus, but neither stimulation results in muscular contraction. However, direct stimulation of both the gastrocnemius and the quadriceps femoris muscles of the rear leg results in muscular contraction. From these observations, what do you logically conclude to be the location of this horse’s pathological lesion?
a. Upper motor neurons controlling the rear legs b. Lower motor neurons to the rear legs
c. Neuromuscular synapses of the rear legs
d. Muscles of the rear legs
e. Either b or c
e
You examine a cat that cannot bear weight on the hind legs. The cat is bright, alert, and responsive. Atrophy is present in the back legs. Cranial nerve reflexes are within normal limits, as are segmental reflexes and the proprioceptive positioning responses of the front legs. Knee jerk and toe-pinch withdrawal reflexes are absent in the hind legs. What is the most likely location for this cat’s pathological lesion?
a. Brainstem
b. Cervical spinal cord (spinal cord in the neck)
c. Thoracolumbar spinal cord (spinal cord between the front
and rear legs)
d. Lower motor neurons to the front legs
e. Lower motor neurons to the hind legs
e
A motor neuron pool located most laterally in the ventral horn of the spinal cord is most likely to operate a muscle controlling movement of the:
a. Proximal limb
b. Neck
c. Distal limb
d. Abdomen
c
Which of the following is true regarding decerebrate rigidity? a. It can result from severe forebrain disease.
b. Disruption of the cortical control of medullary reticulospi-
nal neurons is a major contributor to the condition.
c. It can result in a fixed, rigid, hobbyhorse-like posture in the
quadruped.
d. Removal of normal inhibition to some of the antigravity
muscles contributes to the condition.
e. All of the above are true.
e
Which of the following descending brainstem motor pathways controls distal limb musculature associated with skilled movement?
a. Medial vestibulospinal tract
b. Rubrospinal tract
c. Pontine reticulospinal tract
d. Tectospinal tract
e. All of the above play a major role in such control
b
The corticospinal (pyramidal) tract, in general, initiates what form of movement?
a. Antigravity movement
b. Postural adjustment
c. Skilled, voluntary, mostly flexor movement
d. Tremulous, jerky movement
e. None of the above
c
You are presented with a dog with a weakness, and proprioceptive placing reaction deficit, of his left front and left back legs. A single pathological site could cause these signs if it were located in the:
a. Left side of the cervical spinal cord b. Left cerebral cortex
c. Right cerebral cortex
d. Either a or b
e. Either a or c
e
The Reticulospinal and Vestibulospinal Tracts Are Medial Brainstem Motor Pathways Important for Keeping the Body Upright Against the Pull of Gravity: true or false?
True
Medial and Lateral Descending Brainstem Motor Pathways Respectively Control Proximal Muscles of Posture and More Distal Muscles of Skilled Movement: true or false?
True
The Rubrospinal Tract Is a Lateral Brainstem Motor Pathway That Can Control Distal Limb Musculature Associated With Skilled Movement: true or false?
true
The Corticospinal (Pyramidal) Tract Is a Direct Projection From Cerebral Cortex to Spinal Cord Responsible for the Most Skilled Voluntary Movements of Mammals. True or false?
True
You are presented with a dog with a head tilt, compulsive circling, and spontaneous nystagmus. The most likely site of this dog’s pathological lesion is the:
a. Oculomotor nucleus
b. Cerebral cortex
c. Vestibular system
d. Cervical spinal cord
e. Spinal accessory (eleventh cranial) nerve
c
Which one of the following statements is false?
a. In a given utricle, the cilia of all of the hair cells are oriented
in the same horizontal direction.
b. In a single vestibular hair cell, displacement of the cilia
toward the largest cilium increases the firing rate of the hair
cell’s associated sensory neuron.
c. The axons of sensory neurons synaptically associated with
vestibular hair cells form the eighth cranial nerve.
d. A gelatinous layer is associated with the vestibular macula. e. The vestibular nuclear complex is located in the brainstem.
a - Utricular macula (horizontally oriented but different directions), and saccular macula (vertically orientated in different directions)
If a normal dog is sitting on a piano stool and I start to spin (accelerate) the stool to the right, which two of the following will be false regarding the observed nystagmus?
a. The pattern of nystagmus observed at the start of rotation
will be seen in reverse briefly after the spinning is abruptly
stopped.
b. An intact medial longitudinal fasciculus (MLF) is important for producing the nystagmus.
c. The nystagmus will continue long after constant velocity is achieved.
d. The eyes will drift slowly to the left, as far as they can go, and then flip rapidly back to the right.
e. Nystagmus will often be observed long after the spinning has stopped, while the dog is stationary.
c and e
C - nystagmus stops after constant velocity is achieved.
Answer “A” explains the transient postrotatory nystagmus, with the converse eye movement pattern to that just noted, can be seen if a spinning animal or person is suddenly stopped. Inertia of the endolymph causes it to continue rotating in the semicircular duct, pushing on the crista ampullaris, even though the head and duct have stopped moving. It is very brief/transient
Which of the following is principally involved in planning ahead for the next appropriate movement?
a. Vestibulocerebellum
b. Spinocerebellum
c. Cerebrocerebellum d. Archicerebellum
e. Both a and b
c - Cerebrocerebellum Helps With Planning Coordinated, Properly Timed Movement Sequences - (located in the lateral hemispheres)
Vestibulocerebellum coordinate Balance and Eye Movements - (located in ventral position)
Spinocerebellum Coordinate Muscle Tone as Well as Limb Movement (located in a central position)
With regard to symptoms of cerebellar dysfunction, movements that continue either too long, or not long enough, are most correctly referred to as which one of the following?
a. Ataxia
b. Asynergia
c. Hypoplasia
d. Dysmetria
d - dysmetria - too long or not long enough movements. Often manifested as difficulty in bringing the muzzle to a fixed point in space, such as a food dish, and as exaggerated “goose stepping” walking movements
Ataxia is when animals often place their paws far apart (wide-based gait) and walk in an uncoordinated manner
Asynergia failure of the components of a complex, multiple-joint movement to occur in a coordinated fashion, may also be seen. It is particularly characteristic of damage to the cerebrocerebellum.
Which of the following is true regarding cerebellar Purkinje cells?
a. They are located in the cerebellar cortex.
b. They have large cell bodies.
c. They have an extensive dendritic tree.
d. When active, they inhibit the activity of cells in deep cer-
ebellar nuclei, whose axons leave the cerebellum.
e. All the above.
e - all the above
Choose the incorrect statement below:
a. A ganglion is a collection of nerve cell bodies outside the
CNS.
b. Acetylcholine is a chemical transmitter at the parasympa-
thetic postganglionic–to–target organ synapse.
c. Sympathetic postganglionic neurons are usually longer than
those of the parasympathetic system.
d. The adrenal medulla secretes mostly norepinephrine and
relatively little epinephrine.
e. Muscarinic acetylcholine receptors are found on peripheral
targets of parasympathetic postganglionic neurons.
d - secretes both in equal manner
A chemical neurotransmitter between preganglionic and postganglionic neurons of the parasympathetic component of the autonomic nervous system is:
a. Norepinephrine
b. Acetylcholine
c. Epinephrine
d. Serotonin
e. γ-Aminobutyric acid
b - ACH mostly released in parasympathetic stimulation
A neurotransmitter most often found at the synapse between sympathetic postganglionic neurons and their targets is:
a. Norepinephrine
b. Epinephrine
c. Acetylcholine
d. Dopamine
e. γ-Aminobutyric acid
a - noradrenaline mostly released in sympathetic stem from the POSTganglionic neuron. Between pre- and post ganglion, the neurotrasmit is ACH
Which of the following is true regarding sympathetic pregan- glionic neurons?
a. Their cell bodies are located in thoracic and lumbar regions
of the spinal cord.
b. Their axons synapse within the sympathetic ganglion chain.
c. Their axons form splanchnic nerves.
d. Their axons travel in the ventral root.
e. All the above are true.
e
Horner’s syndrome is caused by the loss of:
a. Sympathetic innervation to the eye.
b. Parasympathetic postganglionic innervation to the eye. c. Peripheral muscarinic receptors.
d. Vagus nerve fibers.
e. Smooth muscle of the iris.
a
Which of the following is true regarding interactions between the autonomic nervous system and the immune system?
a. Lymphocytes can possess β-adrenergic receptors.
b. The hypothalamus can indirectly modulate neuroinflam-
mation.
c. Postganglionic sympathetic neurons innervate lymph nodes.
d. Activating parasympathetic axons of the vagus nerve can
modulate cytokine release from immune cells.
e. All the above are true.
e
You examine a patient’s pupillary light reflexes. Shining a light into the left eye produces both a positive direct and a positive consensual pupillary response. However, shining the light into the right eye produces neither a direct nor an indirect pupillary response. This patient’s pathological lesion is located in which one of the following structures?
a. Left optic nerve
b. Left oculomotor nerve
c. Right optic nerve
d. Right oculomotor nerve e. Left primary visual cortex
C - must be pre-chiasma, and located in optic nerve
A patient whose left pupil diameter is smaller than normal, whose left upper eyelid droops, and whose left “third eyelid” is abnormally displaced likely has a lesion of which of the following structures?
a. Left oculomotor nerve
b. Left vagosympathetic nerve trunk
c. Right oculomotor nerve
d. Right vagosympathetic nerve trunk e. Left optic tract
B - sympathetic stimulation (Horner) issue due affect same side
In the veterinarian’s waiting room, your friend, a member of the soccer team, is trying without much success to explain the cause for the team’s recent losing trend. A variety of implausible explanations are proposed until she mentions that she is progres- sively losing vision, but only in her left visual field, and has frequent headaches. You recommend that she see a neurologist because she likely has a lesion in her:
a. Left optic tract
b. Right optic nerve
c. Right optic tract
d. Optic chiasm
e. Left optic radiations
c - because lack is from left visual field, the right optic tract (after chiasma) must be affected (see picture that explains)
Which two of the following are false regarding the blood-brain barrier (
Which two of the following are false regarding the blood-brain barrier (BBB)?
a. The BBB is very effective at the circumventricular organs
of the brain.
b. Astrocytic end-feet are part of the neurovascular unit.
c. Brain capillaries generally have a high number of endothe-
lial tight junctions.
d. Many dyes injected into the blood can typically penetrate
most tissues of the body but usually not the brain.
e. Small, uncharged, lipid-soluble molecules do not generally
pass through the BBB.
a and e
As a general rule, molecules that are small, uncharged, lipid-soluble, and unbound to plasma proteins (e.g., O2, CO2, ethanol, nicotine) can easily pass across the capillary endothelium of the BBB. Some molecules that do not fit this profile (e.g., glucose, some amino acids) are able to pass through the BBB by specific, carrier-mediated transport mechanisms
CSF is principally formed at the:
a. Arachnoid villi
b. Aqueduct of Sylvius
c. Choroid plexuses
d. Subarachnoid space e. Dorsal sagittal sinus
c
