Chapter 12 Autonomic Nervous System

Acetylcholine is the correct answer because it is the neurotransmitter that is secreted by cholinergic fibers. Cholinergic fibers are nerve fibers that release acetylcholine as their primary neurotransmitter. Acetylcholine is involved in various physiological processes, including muscle contraction, regulation of heart rate, and memory formation. It is also responsible for transmitting signals in the parasympathetic nervous system, which controls rest and digestion.

The most characteristic feature of the parasympathetic nervous system is its involvement in promoting rest and digestion, also known as "feed and breed" response. Unlike the sympathetic nervous system, which is responsible for the "fight or flight" response, the parasympathetic system helps conserve energy and maintain homeostasis by slowing heart rate, increasing digestion, and promoting relaxation. This response is mediated by the release of neurotransmitter acetylcholine, not adrenergic or norepinephrine.

Postganglionic parasympathetic discharge leads to a slowed heart rate. This is because the parasympathetic nervous system is responsible for rest and digest functions, which include decreasing heart rate to conserve energy. When the parasympathetic nerves release acetylcholine onto the SA node of the heart, it decreases the firing rate of the pacemaker cells, resulting in a slower heart rate.

Skeletal muscle is not an effector organ for the autonomic nerves because it is primarily controlled by the somatic nervous system, which is under voluntary control. The autonomic nervous system, on the other hand, regulates the activity of smooth muscles, glands, and cardiac muscle, which are involuntary and not under conscious control.

Vasomotor tone refers to the continuous low-level firing of sympathetic nerves that causes vasoconstriction in blood vessels. This background firing maintains a baseline level of constriction, which helps regulate blood pressure and blood flow throughout the body. Sympathetic nerves release norepinephrine, which binds to alpha-adrenergic receptors on smooth muscle cells in blood vessel walls, leading to their contraction and subsequent vasoconstriction. This vasoconstrictor effect is crucial in maintaining vascular tone and regulating blood pressure.

The most descriptive option for dual innervation of the autonomic nervous system is "sympathetic and parasympathetic." The autonomic nervous system is responsible for regulating involuntary bodily functions, and it is divided into two branches: the sympathetic and parasympathetic systems. The sympathetic system prepares the body for "fight or flight" responses, while the parasympathetic system promotes relaxation and restorative processes. Together, these two systems work in opposition to maintain homeostasis in the body. The other options mentioned, such as muscarinic and nicotonic or alpha and beta, do not accurately represent the dual innervation of the autonomic nervous system.

The group that is incorrect is "sympathetic responses: decreased blood pressure, decreased heart rate, anxiety." This is incorrect because sympathetic responses typically increase blood pressure and heart rate, and can also lead to anxiety.

Paravertebral ganglia are also called the sympathetic chain ganglia. This means that they are part of the sympathetic nervous system, which is responsible for the "fight or flight" response. These ganglia are located along the spinal cord and play a role in transmitting signals from the central nervous system to various organs in the body. They are not part of the craniosacral outflow or directly involved in driving the vagus nerve. Additionally, they are not located within the organs of innervation.

An adrenergic fiber is one that secretes norepinephrine as its transmitter. Norepinephrine is a neurotransmitter that is released by sympathetic nerves in the body. It plays a role in the "fight or flight" response, increasing heart rate, constricting blood vessels, and mobilizing energy resources. Adrenergic fibers are part of the sympathetic nervous system and are responsible for transmitting signals that activate these physiological responses.

A drug that causes the heart to beat stronger and faster is called sympathomimetic. This term refers to drugs that mimic the effects of the sympathetic nervous system, which is responsible for increasing heart rate and contractility. By activating the receptors in the heart, sympathomimetic drugs can enhance its function and increase its output.

The "feed and breed" system is a term used to describe the parasympathetic nervous system, which is responsible for promoting relaxation, digestion, and reproduction. The cranialsacral outflow is a part of the parasympathetic nervous system that originates in the cranial nerves and sacral spinal cord. This outflow is involved in regulating various bodily functions, including digestion and reproductive processes. Therefore, the cranialsacral outflow is most related to the "feed and breed" system.

The term "muscarinic and nicotine receptors" is least descriptive of thoracolumbar outflow because it refers to specific types of receptors found in the parasympathetic nervous system, not the sympathetic nervous system. The sympathetic nervous system is responsible for the "fight or flight" response and is associated with the thoracolumbar outflow, which includes the paravertebral ganglia.

A beta1 adrenergic agonist is a type of medication that activates beta1 adrenergic receptors in the body. These receptors are primarily located in the heart. When activated, they increase the heart rate by stimulating the heart to beat faster. Therefore, the correct answer is "increases heart rate."

Alpha and beta receptors are activated by norepinephrine. Norepinephrine is a neurotransmitter that is released by the sympathetic nervous system. Alpha and beta receptors are found on the target cells of the sympathetic nervous system and are responsible for mediating the effects of norepinephrine. Activation of alpha receptors leads to vasoconstriction and increased blood pressure, while activation of beta receptors leads to vasodilation and increased heart rate. Therefore, the correct answer is that alpha and beta receptors are activated by norepinephrine.

Muscarinic receptors are activated by acetylcholine (ACh). These receptors are located on the effector organs of the parasympathetic nervous system. When ACh binds to muscarinic receptors, it triggers a response in the target organ or tissue. This activation leads to various physiological effects, such as slowing heart rate, increasing glandular secretions, and stimulating smooth muscle contraction. Norepinephrine and catecholamines like adrenaline and dopamine, on the other hand, primarily activate adrenergic receptors, which are associated with the sympathetic nervous system.

The characteristic of the sympathetic nervous system that is described in the given answer is paravertebral ganglia. Paravertebral ganglia are a series of ganglia that are located on either side of the spinal cord and are involved in the sympathetic division of the autonomic nervous system. They play a crucial role in the transmission of signals between the central nervous system and the target organs.

The characteristic of the parasympathetic nervous system is that the postganglionic fiber is cholinergic. This means that the neurotransmitter released by the postganglionic fiber is acetylcholine.

An adrenergic fiber refers to a nerve fiber that releases the neurotransmitter norepinephrine. The sympathetic nervous system is responsible for the "fight or flight" response in the body, and norepinephrine is the main neurotransmitter involved in this response. The postganglionic sympathetic fibers are the nerve fibers that carry the signals from the ganglia (clusters of nerve cell bodies) to the target organs or tissues. Therefore, the correct answer is postganglionic sympathetic.

The sympathetic and parasympathetic nerves innervate the viscera, which means they supply the autonomic nervous system that controls the involuntary functions of the body's organs. These nerves regulate processes such as heart rate, digestion, and respiration. Unlike somatic motor neurons that control voluntary skeletal muscles, the sympathetic and parasympathetic nerves are responsible for involuntary actions. Examples of these nerves include the phrenic, sciatic, and brachial nerves.

After receiving an antimuscarinic drug like atropine, the patient is likely to experience difficult urination as a postoperative consequence. Antimuscarinic drugs inhibit the action of acetylcholine, a neurotransmitter responsible for stimulating the contraction of the bladder muscles. By blocking this action, atropine can lead to urinary retention and difficulty in emptying the bladder.

The vagus nerve is known to have cholinergic effects, meaning it releases acetylcholine (ACh) as its transmitter. These cholinergic effects include slowing down the heart rate. However, the statement that its effect on the heart is eliminated by a beta1 adrenergic blocker is least true. Beta1 adrenergic blockers primarily block the effects of norepinephrine and epinephrine, not acetylcholine. Therefore, the effect of the vagus nerve on the heart would not be eliminated by a beta1 adrenergic blocker.

Vagal discharge refers to the activation of the vagus nerve, which is responsible for the parasympathetic nervous system. Muscarinic receptors are a type of receptor that is activated by the neurotransmitter acetylcholine, which is released by the vagus nerve. Therefore, when vagal discharge occurs, it activates muscarinic receptors.

Sympathetic nerve stimulation activates the beta2 adrenergic receptors, which leads to bronchodilation or relaxation of the breathing passages. Therefore, a drug that acts as a beta2 adrenergic agonist would achieve this effect by directly stimulating these receptors and causing bronchodilation. Alpha1 adrenergic blockers, vagomimetics, and parasympathomimetics do not directly cause bronchodilation and are not specifically targeted towards the sympathetic nerve stimulation pathway.

The effects of adrenal medullary secretion most resemble sympathetic nerve discharge because both involve the release of adrenaline and noradrenaline. Adrenal medullary secretion is the release of these hormones from the adrenal medulla, which is part of the sympathetic nervous system. Sympathetic nerve discharge also involves the release of these hormones from sympathetic nerve endings. Both processes result in similar physiological responses, such as increased heart rate, dilation of blood vessels, and increased blood sugar levels. Therefore, the effects of adrenal medullary secretion closely resemble sympathetic nerve discharge.

The correct answer is "found within all cholinergic nerve terminals." This is because monoamine oxidase (MAO) is primarily associated with the degradation of norepinephrine, which is a neurotransmitter found within adrenergic nerve terminals. Cholinergic nerve terminals, on the other hand, release acetylcholine as a neurotransmitter, which is not directly affected by MAO. Therefore, MAO is least associated with cholinergic nerve terminals.

Atropine is classified as a vagolytic because it acts as an antagonist or blocker of muscarinic receptors. Vagolytic drugs inhibit the actions of the parasympathetic nervous system, specifically the vagus nerve, which is responsible for regulating various bodily functions. By blocking the effects of acetylcholine on muscarinic receptors, atropine prevents the parasympathetic nervous system from being stimulated, resulting in an overall increase in sympathetic activity. This leads to a range of effects, including increased heart rate, dilation of the pupils, and relaxation of smooth muscles in the airways.

Sympatholytic drugs lower blood pressure by inhibiting the actions of the sympathetic nervous system. The sympathetic nervous system is responsible for stimulating vasoconstriction, which increases blood pressure. By blocking or reducing the activity of the sympathetic nervous system, sympatholytic drugs allow blood vessels to relax and dilate, leading to a decrease in blood pressure.

The thoracolumbar outflow, also recognized as the sympathetic nervous system, involves neurons whose axons exit the spinal cord through ventral roots. These axons then form synapses either on sympathetic ganglion cells or on specialized cells known as chromaffin cells in the adrenal gland.

A muscarinic antagonist will relieve the bradycardia because it blocks the effects of acetylcholine on muscarinic receptors in the heart. Acetylcholine, released by the vagus nerve, slows down the heart rate by activating muscarinic receptors. By blocking these receptors, a muscarinic antagonist will prevent the inhibitory effects of acetylcholine, leading to an increase in heart rate and relieving the bradycardia.