Week 129 Autonomic Nervous System

Parasympathetic activation = "Rest and Digest". Obviously these are simplified classifications, but they are fairly useful.

Acetylcholine is the correct answer because it is released by the preganglionic neurons of the parasympathetic system. Acetylcholine is a neurotransmitter that plays a crucial role in the parasympathetic nervous system, which is responsible for rest and digest functions. It is released by the preganglionic neurons to transmit signals to the postganglionic neurons, allowing for communication between nerve cells and facilitating the parasympathetic response.

Noradrenaline is the correct answer because it is released by the postganglionic neurons of the sympathetic system. The sympathetic system is responsible for the "fight or flight" response in the body, and noradrenaline is one of the key neurotransmitters involved in this response. It helps to activate various physiological processes such as increasing heart rate, constricting blood vessels, and increasing blood pressure. Acetylcholine, on the other hand, is primarily released by the postganglionic neurons of the parasympathetic system, which is responsible for rest and digestion.

The vagus nerve is perhaps the most important source of parasympathetic preganglionic neurones.

Acetylcholine is the correct answer because it is released by the postganglionic neurons of the parasympathetic system. Acetylcholine is a neurotransmitter that plays a crucial role in the parasympathetic nervous system, which is responsible for rest and digest functions in the body. It is released by the postganglionic neurons to transmit signals to target organs and tissues, leading to various physiological responses such as increased digestion, decreased heart rate, and relaxed muscles. Noradrenaline, on the other hand, is predominantly released by the postganglionic neurons of the sympathetic system, which is responsible for the fight or flight response.

The enteric division of the autonomic nervous system is responsible for controlling gastrointestinal motility and secretion. It consists of a complex network of nerves that are located within the walls of the digestive tract. This division operates independently of the central nervous system, allowing it to regulate digestion and other gastrointestinal functions without conscious control. The enteric division plays a crucial role in coordinating the movement of food through the digestive system and in regulating the release of digestive enzymes and hormones.

The sympathetic innervation of the viscera is carried via the splanchnic nerves. These nerves are responsible for transmitting sympathetic signals to the organs located in the abdominal and pelvic regions. The splanchnic nerves originate from the sympathetic chain ganglia and travel to the target organs, where they synapse with postganglionic neurons. This sympathetic innervation plays a crucial role in regulating various visceral functions, including blood flow, digestion, and organ activity.

Acetylcholine is the correct answer because it is released by the preganglionic neurons of the sympathetic system. Acetylcholine is a neurotransmitter that is involved in the transmission of nerve impulses in the autonomic nervous system. It is released by the preganglionic neurons to activate the postganglionic neurons in the sympathetic system. This release of acetylcholine helps in the transmission of signals and coordination of various physiological responses in the body. Noradrenaline, on the other hand, is released by the postganglionic neurons and is involved in the activation of target organs in the sympathetic system.

The cells of the adrenal medulla are basically modified postganglionic neurones that release noradrenaline (and other catecholamines) into the circulation

Activation of the sympathetic system leads to the release of norepinephrine, which causes the pupils to dilate. It also stimulates the release of epinephrine and norepinephrine from the adrenal medulla, resulting in an increase in heart rate and force of contraction. This activation of the sympathetic system also leads to the inhibition of salivation, so there is a decrease in saliva production. Additionally, the sympathetic system stimulates the release of renin, which leads to vasoconstriction and a decrease in urine production. Therefore, the correct answers are pupil dilation, increase in heart rate and force, and increased adrenaline production by the adrenal medulla.

Referred pain occurs when pain is felt in a site that is not actually injured, but is innervated by the same spinal cord level as the injured site. This happens because the sensory nerves from both sites converge on the same spinal cord level, leading to a confusion in the brain about the source of the pain. This phenomenon is commonly seen in conditions such as heart attacks, where pain is felt in the left arm or jaw instead of the chest.

Propanolol is an antagonist of beta-adrenergic receptors. This means that it blocks the action of beta-adrenergic receptors in the body. Beta-adrenergic receptors are responsible for responding to adrenaline and noradrenaline, which are hormones involved in the "fight or flight" response. By blocking these receptors, propanolol can reduce the effects of these hormones, such as reducing heart rate and blood pressure. It is commonly used to treat conditions such as high blood pressure, angina, and certain heart rhythm disorders.

The sympathetic postganglionic neurons innervating the structures of the face arise from the superior cervical ganglion. This ganglion is located in the neck, at the level of the second and third cervical vertebrae. It receives preganglionic fibers from the thoracic spinal cord via the sympathetic chain and sends postganglionic fibers to various structures in the face, including the blood vessels, sweat glands, and smooth muscles.

Preganglionic sources of the parasympathetic system "top and tail" those of the sympathetic system, which arises from spinal segments T1-L2.

Clonidine is an agonist of alpha-2 adrenergic receptors. This means that it binds to and activates these receptors, leading to a decrease in sympathetic outflow from the central nervous system. By stimulating alpha-2 receptors, clonidine reduces the release of norepinephrine, resulting in decreased blood pressure and heart rate. It is commonly used to treat hypertension, attention deficit hyperactivity disorder (ADHD), and withdrawal symptoms from opioids or nicotine.

Some sympathetic ganglia are located outside the sympathetic chains. Those of you paying attention may remember that preganglionic sympathetic neurones do terminate on the adrenal medulla, so don't feel too bad if you checked option 4!

Activation of the parasympathetic system stimulates the release of acetylcholine, which increases the production of gastric juices in the stomach. It also causes contraction of the bronchial muscles, leading to bronchoconstriction. Additionally, activation of the parasympathetic system increases mucus production from the nasal mucosa, helping to moisten and protect the respiratory tract. However, the parasympathetic system does not directly affect the relaxation of the bladder wall or decrease intestinal motility.

Muscarinic receptors are pretty good pharmacological targets because the different subtypes (M1-M5) show tissue-specific distribution. However there are not currently any good subtype-specific drugs.

Orthostatic hypotension is a condition characterized by a drop in blood pressure when transitioning from a sitting or lying position to a standing position. It is more prevalent in the elderly, possibly due to age-related changes in the autonomic nervous system. It can also be a side effect of drugs that block the alpha-1 adrenergic receptor, which can affect blood vessel constriction. The condition occurs because the autonomic system does not react quickly enough to maintain blood pressure when standing up.

The parasympathetic postganglionic neurons innervating the lacrimal gland arise from the pterygopalatine ganglion. This ganglion is located in the pterygopalatine fossa, which is a small space in the skull. From this ganglion, the postganglionic fibers travel to the lacrimal gland to stimulate tear production.

The nicotinic acetylcholine receptors are located on postganglionic neurons of both the sympathetic and parasympathetic systems. These receptors are ionotropic, meaning they allow the flow of ions across the cell membrane when activated. They are specifically activated by nicotine, which binds to these receptors and triggers a response. However, they are not blocked by propranolol, which is a non-selective beta blocker. Additionally, they are not directly stimulated by clonidine, which is an alpha-2 adrenergic agonist.