Anatomy
Showing posts with label Anatomy. Show all posts
Showing posts with label Anatomy. Show all posts

The muscle weakness of myasthenia gravis results from

The muscle weakness of myasthenia gravis results from





A) inability of the muscle fiber to produce ATP.
B) insufficient acetylcholine release from presynaptic vesicles.
C) the motor neuron action potential being too small to shock the muscle fibers.
D) loss of acetylcholine receptors in the end- plate membrane.
E) excessive acetylcholinesterase that destroys the neurotransmitter.





Answer: D

Which statement about excitation-contraction coupling is incorrect?

Which statement about excitation-contraction coupling is incorrect? 




A) Troponin binds calcium ion and signals tropomyosin to move.
B) Tropomyosin moves to expose myosin binding sites on actin.
C) Relaxation requires uptake of calcium ion by the sarcoplasmic reticulum.
D) Calcium ion is released from the sarcoplasmic reticulum.
E) Calcium ion is released from the transverse tubule.





Answer: E

At rest, active sites on the actin are blocked by

At rest, active sites on the actin are blocked by 




A) ATP molecules.
B) myosin molecules.
C) tropomyosin molecules.
D) calcium ions.
E) troponin molecules.




Answer: C

Which of the following statements about the action potential is false?

Which of the following statements about the action potential is false? 



A) In the after-hyperpolarization phase, membrane potential approaches the potassium equilibrium potential.
B) Repolarization occurs as potassium ions leave the axon.
C) During the repolarization phase, sodium channels close and potassium channels open.
D) During the depolarization phase, membrane potential becomes positive.
E) The rapid depolarization phase is caused by the entry of potassium ions.






Answer: E

Which of the following interactions between electrical and chemical gradients does not lead to the establishment of a neuron's resting potential?

Which of the following interactions between electrical and chemical gradients does not lead to the establishment of a neuron's resting potential?




A) Potassium ions are attracted to the negative charges inside the cell.
B) Chemical and electrical forces both favor sodium ions entering the cell.
C) Potassium ions are repulsed by positive charges outside the cell.
D) Electrical forces push sodium ions out of the cell.
E) Chemical forces tend to drive potassium ions out of the cell.





Answer: D

The postganglionic fibers that connect an autonomic ganglion in the thoracic or lumbar region with the spinal nerve and contain post ganglionic fibers that innervate glands in the body wall or limbs are:

The postganglionic fibers that connect an autonomic ganglion in the thoracic or lumbar region with the spinal nerve and contain post ganglionic fibers that innervate glands in the body wall or limbs are:




A) white rami communicantes.
B) ventral ramus.
C) dorsal ramus.
D) gray rami communicantes.
E) dermatomes.





Answer: D

The preganglionic fibers that connect a spinal nerve with an autonomic ganglion in the thoracic and lumbar region of the spinal cord and carries visceral motor fibers that are myelinated form the

The preganglionic fibers that connect a spinal nerve with an autonomic ganglion in the thoracic and lumbar region of the spinal cord and carries visceral motor fibers that are myelinated form the




A) dorsal ramus.
B) ventral ramus.
C) white rami communicantes.
D) gray rami communicantes.
E) dermatomes.





Answer: C

The white matter of the spinal cord is mainly

The white matter of the spinal cord is mainly



A) nodes of Ranvier.
B) unmyelinated axons.
C) myelinated and unmyelinated axons.
D) neuroglia.
E) Schwann cells.






Answer: C

The subdural space lies between

The subdural space lies between




A) the endosteum and the periosteum.
B) the pia mater and the dura mater.
C) the dura mater and the arachnoid mater.
D) the pia mater and the subarachnoid space.
E) the arachnoid mater and the pia mater.




Answer: C

The ventral root of a spinal nerve contains

The ventral root of a spinal nerve contains 




A) axons of motor neurons.
B) interneurons.
C) cell bodies of sensory neurons.
D) axons of sensory neurons.
E) cell bodies of motor neurons.




Answer: A

The dorsal root of a spinal nerve contains

The dorsal root of a spinal nerve contains 




A ) axons of sensory neurons.
B) cell bodies of motor neurons.
C) cell bodies of sensory neurons.
D) axons of motor neurons.
E) interneurons.





Answer: A

The dorsal root ganglia mainly contain

The dorsal root ganglia mainly contain 




A) axons of motor neurons.
B) synapses.
C) cell bodies of sensory neurons.
D) cell bodies of motor neurons.
E) axons of sensory neurons.





Answer: C
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