Question

9.

What is FALSE about somatic division?

Select one:

a. The somatic division is made of somatic motor neurons that target only the skeletal muscle cells or muscle fibers.

b. A motor unit is one somatic motor neuron and all of the muscle fibers it innervates.

c. The somatic motor neuron secrets acetylcholine (ACh) from the axon terminal.

d. If ACh binds to the nicotinic receptor at the motor end plate of the muscle fiber, the responds is excitatory.

e. If ACh binds to acetylcholine esterase at the motor end plate of the muscle fiber, the responds is inhibitory because acetylcholine esterase will break up ACh into acetyl and choline.

f. All of the above

g. None of the above

10.

The synapse between somatic motor neuron and muscle fiber is at the neuromuscular junction that is composed of the axon terminal of the somatic motor neuron and the motor-end-plate of the muscle fiber.

Select one:

a. True

b. False

11.

What is TRUE about the autonomic division? There may be more than one answer.

Select one or more:

a. The autonomic division consists of the parasympathetic and sympathetic divisions that target the cardiac cells, smooth muscle cells, and glands.

b. The parasympathetic and sympathetic divisions are made of pre-ganglionic neuron that synapses with the post-ganglionic neuron at the neuromuscular junction.

c. The pre-ganglionic neuron of both parasympathetic and sympathetic would secrete acetylcholine at the axon terminal and it would bind to the nicotinic receptor at the dendrites/cell body of the post-ganglionic neuron.

d. The post-ganglionic neuron of the parasympathetic would secrete acetylcholine to the target cells. At the target cells, the acetylcholine would bind to the nicotinic receptor.

e. The post-ganglionic neuron of the sympathetic would secrete norepinephrine and epinephrine. At the target cells, the norepinephrine and epinephrine would bind to the adrenergic receptors (alpha 1, alpha 2, beta 1, beta 2, or beta 3).

12.

What is the CORRECT statement about the parasympathetic division? There may be more than one answer.

Select one or more:

a. Only acetylcholine is secreted from the post-ganglionic neuron to the target cells.

b. Nicotinic receptors are at the heart, GI tract, and bronchioles.

c. In the gastrointestinal tract (GI tract), parasympathetic neurons will cause the smooth muscle cells to relax, causing the walls of the intestines to dilate.

d. In the blood vessels, parasympathetic neurons will cause the smooth muscle cells to contract, causing the blood vessels to vasoconstrict.

e. In the bronchioles, parasympathetic neurons will cause bronchoconstriction.

Answer 1

9. The Somatic neural system is a part of Peripheral nervous system (PNS) which relays impulses from the CNS to skeletal muscles. The somatic nueral system consist of somatic division that consists of somatic motor neurons that relays impulses from the  CNS to the axons of skeletal muscle cells and skeletal muscle fibers. So it is directly controls all voluntary muscular systems within the body. Somatic neurons contain alpha efferent neurons, beta efferent neurons and gamma efferent neurons that projects their axons to skeletal muscles. A somatic motor neuron can innervate many muscle fibers. Hence the motor neuron and all of the muscle fibers to which it connects is a motor unit. The somatic neurons secrete Acetylcholine (ACh) from their axon terminal knobs and received by postsynaptic receptors (nicotinic acetylcholine receptors) of muscles. The binding of ACh to the nicotinic receptor at the motor end plate of the muscle fiber, it stimulates an excitatory response, resulting in ther initiation of muscle contraction. Again if ACh binds to acetylcholine esterase at the motor end plate of the muscle fiber, the response is inhibitory as acetylcholinesterase rapidly breaks down the ACh already present in the synaptic cleft into acetyl and choline, resulting in relaxation of muscle fiber. So the correct option is (g).

10. The junction between the nerve fiber and muscle fiber is called neuromuscular junction. The feature of the synaptic junction at the neuromuscular junction between somatic motor neuron and muscle fiber is composed of the axon terminal of the somatic motor neuron and the motor end plate of the muscle fiber. So the statement is true.

11. The autonomic neural division transmits impulses from CNS to the involuntary organs and smooth muscles of the body. The autonomic neural system consists of the parasympathetic and sympathetic divisions that target the cardiac cells, smooth muscle cells and glands. Both the parasympathetic and sympathetic divisions are made of pre-ganglionic neurons that synapses with the post-ganglionic neuron at the neuromuscular junction. Sympathetic divisions receives preganglionic sympathetic fibers from the spinal cord which makes their exit alongwith thoracic and lumbar nerves and constititute thoraco-lumbar outflow. These fibers synapse with the neurons present in the sympathetic ganglia. From the sympathetic ganglia arise post ganglionic fibers which terminate on the viscera. Each sympathetic ganglion is connected to the spinal cord by a white communicans and the spinal nerve by a gray communicans. Parasympathetic divisions consists of preganglionic parasympathetic fibers, parasympathetic ganglia and postganglionic parasympathetic fibers. Preganglionic parasympathetic fibers consists the cranio-sacral outflow. The parasympathetic ganglia do not form any chains and instead lie on or near the viscera.

The neurotransmitter within the ganglion (preganglionic) is acetylcholine for both sympathetic and parasympathetic nerves. The preganglionic neuron of both sympathetic and parasympathetic would secrete acetylcholine at the axon terminal and bind to the nicotinic receptor at the dendrires/cell body of the postganglionic neuron. However, the neurotransmitter between the terminal autonomic neurons axon and the target organ is different in the two antagonistic autonomic nervous system. In the parasympsthetic system, the neurotransmitter at the postganglionic neuron is acetylcholine that would bind to nicotinic receptor, just as it is in the ganglion. In the sympathetic system, the neurotransmitter at the postganglionic neurons is either adrenaline or noradrenaline, both of which have an effect opposite to that of acetylcholine. These neurotransmitter of post ganglionic neurons of symapathetic divisions bind to adrenergic receptors (alpha 1, alpha 2, beta 1, beta 2 or beta 3).

So the all the options are correct.

12. Parasympathetic nerve fibers have only acetylcholine that is secreted from the postganglionic neuron to the target cells. These neurotransmitters bind to the nicotinic receptors present in the heart, GI tract and brionchioles. The parasympathetic nerves increases the intestinal gland activity and relaxes the smooth sphincter muscles in the GI tract, causing the walls of intestines to dilate. In brionchioles, parasympathetic nerves cause bronchoconstriction, i.e narrows air passages, hindering breathing. In blood vessels, parasympathetic neurons causes the smooth muscle cells to relax, resulting in widening of the blood vessels, i.e act as a vasodilator. So the correct options are (a), (b), (c) and (e).