Parasympathetic Nervous Division

Parasympathetic Division

The parasympathetic nervous systemThe organ system that controls body functions using electrical and chemical signals. is also known as the rest and digest system or the cranial sacral division. The terms cranial sacral indicate the use of cranial nervesNerves that arise from the brain and control head and neck functions. and sacral nerves as routes output to target organsOrgans affected by specific hormones..   What’s nice about the parasympathetic divisionPart of the autonomic nervous system that conserves energy and promotes rest-and-digest functions. is that both neuronsThe functional cells of the nervous system that transmit signals. are cholinergic and both neurons secrete only acetylcholinealso know as ACh A neurotransmitter that stimulates muscle contraction..

Cranial Preganglionic Fibers

There are 4 cranial nerves. They are used by the parasympathetic nervous system. They innervateTo invade a tissue with nervous tissue is to innervate it. mostly the glands in your face and headRounded proximal end that fits into the acetabulum of the hip bone..  This would include your salivary glands and your lacrimalSmall, thin bones on the medial wall of each orbit; contain a groove for tear drainage. or tear glands. The four cranial nerves are cranial nerve #3 ocular motor. Cranial nerve #7 is facial. Cranial nerve #9 is glossopharyngeal. Cranial nerve 10 is the vagus nerve. The vagus nerve is an exception. It innervates digestive target organs rather than target organs in the head and neckNarrow region just below the head; common fracture site.. However it mostly innervates glandular structures and encourages secretions much like the tear ducts and salivary glands do. Preganglionic fibers originate and travel through the cranial nerves. All synapseThe junction between two neurons where communication occurs. in collateral ganglia. This makes neck surgery a disaster. It makes neck surgeons close to gods.

Cranial Postganglionic Fibers

The post ganglionic fibers that emerge from these collateral ganglia then travel to the target organ. Most of the time, it is not just one post ganglionic nerve neuron. Many postganglionic neurons arise from one preganglionic neuron. The postganglionic neuron has nicotinic receptorsCholinergic receptors found on postganglionic neurons and skeletal muscle; they respond to acetylcho in the cell bodyThe central part of a neuron containing the nucleus and organelles.. These receptorsProteins located on the surface or inside cells that bind specific molecules (e.g., neurotransmitter allow it to generate action potentials when connected with acetylcholine. Therefore the preganglionic neuron is exciting the postganglionic neuron with acetylcholine. The postganglionic neuron then releases its own acetylcholine because it’s a cool energetic neuron. However this time the acetylcholine that the postganglionic neuron releases connects with the muscarinic receptorA structure that detects stimuli. that’s on the target organ. Muscarinic receptors can have both excitatory and inhibitory effects. It depends more upon the neuron then it does upon the receptor in this case.

Sacral Preganglionic Fibers

The sacral division of the parasympathetic division exits the spinal cordThe central nervous system structure that relays signals between the brain and body. using nerves. These nerves arise from spinal levels S2, S3, and S4. Once these nerves leave the spinal cord, they travel through the ventralRelating to the front or belly side of the body. route. They pass through the spinal nerve, then the ventral raymus. Finally, they become nerves called splanchnic nerves. These specifically are the pelvic splanchnic nerves that arise from the sacral section A cut or slice of the body or an organ for study. of the spinal cord. These pelvic splanchnic nerves innervate your colon your ****** your bladderA muscular organ that stores urine before excretion. and your choice of reproductive organs. As these are parasympathetic fibers they are concerned with activating these organs.

Sacral Postganglionic fibers

The preganglionic fibers that arise from the sacral section of your spinal cord form the pelvic splanchnic nerves. These nerves travel all the way to their target organ. They enter the target organ and release acetylcholine. The post ganglionic neuron is embedded completely within the target organ. It has nicotinic receptors in the cell body that allow it to respond to the acetylcholine and be excited. In turn, it releases its own acetylcholine. This acetylcholine connects with muscarinic receptorsCholinergic receptors found on the effector organs of the parasympathetic nervous system; they media on the smooth muscle of the target organ. It can cause inhibition or excitation. In this example here with the bladder, we are trying to make the bladder contract. This effort to urinate is a parasympathetic response. Drugs like Detrol treat overactive bladder. They block muscarinic receptors embedded in the bladder muscle, which is called the detrusor muscleThe smooth muscle layer of the bladder that contracts to expel urine.. By blocking these muscarinic receptors it prevents the bladder from contracting or being overactive. These drugs are called anticholinergic drugs.