Chapter 15 Flashcards
Describe the sensory input, control of motor output, motor neuron pathway, neurotransmitters and hormones, effectors, and responses of the somatic nervous system?
Sensory input: from somatic senses and special senses.
Control of motor output: voluntary control from cerebral cortex, with contributions from basal ganglia, cerebellum, brainstem, and spinal cord.
Motor neuron pathway: one-neuron pathway: somatic motor neurons extending from CNS synapse directly with effector.
Neurotransmitters and hormones: releases acetylcholine (ACh) only.
Effectors: Skeletal muscle.
Responses: contraction of skeletal muscle.
Describe the sensory input, control of motor output, motor neuron pathway, neurotransmitters and hormones, effectors, and responses of the autonomic nervous system (ANS)?
Sensory input: mainly from interoceptors; some from somatic senses and special senses.
Control of motor output: involuntary control from hypothalamus, limbic system, brainstem, and spinal cord; limited from cerebral cortex.
Motor neuron pathway: usually two-neuron pathway: preganglionic neurons extending from CNS synapse with postganglionic neurons in autonomic ganglion, and postganglionic neurons extending from ganglion synapse with visceral effector. Alternatively, preganglionic neurons may extend from CNS to synapse with chromaffin cells of adrenal medullae.
Neurotransmitters and hormones: all sympathetic and parasympathetic preganglionic neurons release ACh. Most sympathetic postganglionic neurons release NE; those to most sweat glands release ACh. All parasympathetic postganglionic neurons release ACh. Chromaffin cells of adrenal medullae release epinephrine and norepinephrine (NE).
Effectors: Smooth muscle, cardiac muscle, and glands.
Responses: contraction or relaxation of smooth muscle; increased or decreased rate and force of contraction of cardiac muscle; increased or decreased secretions of glands.
What are the three divisions of the autonomic nervous system (ANS)?
- Sympathetic nervous system
- Parasympathetic nervous system
- Enteric nervous system (ENS)
Sympathetic nervous system
Promotes fight-or-flight response, which prepares body for emergency situations.
Parasympathetic nervous system
Enhances rest-and-digest activities, which conserve and restore body energy during times of rest or digesting a meal.
Enteric nervous system (ENS)
Consists of millions of neurons in plexuses that extend most of the length of the gastrointestinal (GI) tract. Its operation is involuntary. Neurons of the ENS can be regulated by the other divisions of the ANS. Contains sensory neurons, interneurons, and motor neurons. Enteric sensory neurons monitor chemical changes within the GI tract as well as the stretching of its walls. Enteric interneurons integrate information from the sensory neurons and provide input to motor neurons. Enteric motor neurons govern contraction of GI tract smooth muscle and secretion of GI tract glands.
Visceral effectors
Tissues that are associated with the viscera (internal organs) of the body. Tissues of the ANS can be classified as these (Eg. Cardiac muscle, smooth muscle, and glands).
Biofeedback
Monitoring devices that display information about a body function such as heart rate or blood pressure.
Interoceptors
Sensory receptors located in blood vessels, visceral organs, muscles, and the nervous system that monitor conditions in the internal environment (Eg. Chemoreceptors that monitor blood CO2 levels). These sensory signals aren’t consciously perceived most of the time.
Dual innervation
Receiving nerves from both the sympathetic nervous system and the parasympathetic nervous system. In general, one division stimulates the organ to increase its activity (excitation), and the other division decreases the organ’s activity (inhibition) (Eg. Neurons of the sympathetic nervous system increase heart rate, and neurons of the parasympathetic nervous system slow it down).
Chromaffin cells
Specialized cells in the adrenal medullae (inner portion of the adrenal glands). Secrete epinephrine and norepinephrine (NE).
Preganglionic neuron
The first neuron in the autonomic motor pathway. Its cell body is in the brain or spinal cord; its axon exits the CNS as part of a cranial or spinal nerve. It’s axon is a small-diameter, myelinated type B fiber that usually extends to an autonomic ganglion, where it synapses with a postganglionic neuron. Essentially, they convey nerve impulses from the CNS to autonomic ganglia.
In the sympathetic division, the preganglionic neurons have their cell bodies in the lateral horns of the gray matter in the __ thoracic segments and the first __ (and sometimes __) lumbar segments of the spinal cord. For this reason, the sympathetic division is also called the ______, and the axons of the sympathetic preganglionic neurons are known as the ______.
12; 2; 3; thoracolumbar division; thoracolumbar outflow
Cell bodies of preganglionic neurons of the parasympathetic division are located in the nuclei of __ cranial nerves in the brainstem (__, __, __, and __) and in the lateral gray matter of the ______ through ______ sacral segments of the spinal cord. Hence, the parasympathetic division is also known as the ______, and the axons of the parasympathetic preganglionic neurons are referred to as the ______.
4; III; VII; IX; X; second; fourth; craniosacral division; craniosacral outflow
Postganglionic neuron
The second neuron in the autonomic motor pathway. Lies entirely outside the CNS in the PNS. Its cell body and dendrites are located in an autonomic ganglion, where it forms synapses with one or more preganglionic axons. It’s axon is a small-diameter, unmyelinated type C fiber that terminates in a visceral effector. Essentially, they relay the impulses from autonomic ganglia to visceral effectors.
Autonomic ganglion
Axons from the preganglionic axon extends from the CNS to this autonomic ganglion. Then, axons from the postganglionic axons extend from the autonomic ganglion to the visceral effector.
What are the two major groups of the autonomic ganglion?
- Sympathetic ganglia
- Parasympathetic ganglia
Sympathetic ganglia
Components of the sympathetic division of the ANS. Are the sites of synapses between sympathetic preganglionic and postganglionic neurons.
What are the two major types of sympathetic ganglia?
- Sympathetic trunk ganglia
- Prevertebral (collateral) ganglia
Sympathetic trunk ganglia
AKA vertebral chain ganglia or paravertebral ganglia; lie in a vertical row on either side of the vertebral column. These ganglia extend from the base of the skull to the coccyx. Postganglionic axons from sympathetic trunk ganglia primarily innervate organs above the diaphragm, such as the head, neck, shoulders, and heart.
Prevertebral (collateral) ganglia
Lies anterior to the vertebral column and close to the large abdominal arteries. In general, postganglionic axons from prevertebral ganglia innervate organs below the diaphragm.
Parasympathetic ganglia
Components of the parasympathetic division of the ANS. Preganglionic axons of the parasympathetic division synapse with postganglionic neurons in terminal (intramural) ganglia. Most of these ganglia are located close to or actually within the wall of a visceral organ.
Autonomic plexuses
Tangled networks of sympathetic and parasympathetic neurons in the thorax, abdomen, and pelvis. Many lie along major arteries. May contain sympathetic ganglia and axons of autonomic neurons.
What are the two major autonomic plexuses in the thorax?
- Cardiac plexus
- Pulmonary plexus
Cardiac plexus
Supplies the heart
Pulmonary plexus
Supplies the bronchial tree.
What are the five major autonomic plexuses in the abdomen and pelvis?
- Celiac (solar) plexus
- Superior mesenteric plexus
- Inferior mesenteric plexus
- Hypogastic plexus
- Renal plexus
Celiac (solar) plexus
Is the largest autonomic plexus and surrounds the celiac trunk. Supplies the stomach, spleen, pancreas, liver, gallbladder, kidneys, adrenal medullae, testes, and ovaries.
Superior mesenteric plexus
Contains the superior mesenteric ganglion and supplies the small and large intestines.
Inferior mesenteric plexus
Contains the inferior mesenteric ganglion and supplies the large intestine.
Hypogastic plexus
Is anterior to the fifth lumbar verebra. Contain the inferior mesenteric ganglion and supplies the pelvic viscera.
Renal plexus
Contains the renal ganglion and supplies the renal arteries within the kidneys and ureters.
White ramus
A short pathway that the myelinated preganglionic sympathetic axons pass into before passing to the nearest sympathetic trunk ganglion on the same side.
White rami communicants
What the white rami are collectively called. Structures containing sympathetic preganglionic axons that connect the anterior ramus of the spinal nerve with the ganglia of the sympathetic trunk. They contain myelinated axons. Can only be found in the thoracic and first two or three lumbar nerves.
Sympathetic trunk ganglia
Are arranged anterior and lateral to the vertebral column, one on either side.
Superior cervical ganglion
Postganglionic neurons leaving here serve the head and heart. They are distributed to the sweat glands, smooth muscle of the eye, blood vessels of the face, lacrimal glands, pineal gland, nasal mucosa, salivary glands (which include the submandibular, sublingual, and parotid glands), and heart.
Middle cervical ganglion
Postganglionic neurons leaving here innervate the heart and blood vessels of the neck, shoulder, and upper limb.
Inferior cervical ganglion
Postganglionic neurons leaving here innervate the heart and blood vessels of the neck, shoulder, and upper limb.
What are the four possible ways that axons leave the sympathetic trunk?
- Spinal nerves
- Cephalic periarterial nerves
- Sympathetic nerves
- Splanchnic nerves
Gray rami communicants
Structures containing sympathetic postganglionic axons that connect the ganglia of the sympathetic trunk to spinal nerves. They contain unmyelinated axons. Outnumber the white rami because there is a gray ramus leading to each of the 31 pairs of spinal nerves.
Cephalic periarterial nerves
Nerves that extend to the head by wrapping around and following the course of various arteries (such as the carotid arteries) that pass from the neck to the head. Provide sympathetic innervation to visceral effectors in the skin of the face (sweat glands, smooth muscle of blood vessels, and arrector pili muscles of hair follicles), as well as other visceral effectors of the head (smooth muscle of the eye, lacrimal glands, pineal gland, nasal mucosa, and salivary glands).
Sympathetic nerves
Formed by axons of the postganglionic neurons that leave the trunk and extend to visceral effectors in the thoracic cavity. Provide sympathetic innervation to the heart and lungs.
Splanchnic nerves
Nerves which extend to outlying prevertebral ganglia. Provide sympathetic innervation to the abdominopelvic organs and adrenal medulla.
Splanchnic nerves to the adrenal medulla: some sympathetic preganglionic axons pass, without synapsing, through the sympathetic trunk, greater splanchnic nerves, and celiac ganglion, and then extend to ______ in the adrenal medullae of the adrenal glands. Developmentally, the adrenal medullae and sympathetic ganglia are derived from the same tissue, the neural crest. The adrenal medullae are modified sympathetic ganglia, and the ______ are similar to sympathetic postganglionic neurons, except they lack dendrites and axons. Rather than extending to another organ, however, these cells release hormones into the blood. On stimulation by sympathetic preganglionic neurons, the ______ of the adrenal medullae release a mixture of catecholamine hormones – about __% ______, __% ______, and a trace amount of ______. These hormones circulate throughout the body and intensify responses elicited by sympathetic postganglionic neurons.
Chromaffin cells; chromaffin cells; chromaffin cells; 80; epinephrine; 20; norepinephrine; dopamine
What are the four pairs of ganglia associated with the vagus (X) nerve?
- Ciliary ganglia
- Pterygopalatine ganglia
- Submandibular ganglia
- Otic ganglia
Ciliary ganglia
Lie lateral to each optic (II) nerve near the posterior aspect of the orbit. Preganglionic axons pass with the oculomotor (III) nerves to the ciliary ganglia. Postganglionic axons from the ganglia innervate smooth muscle fibers in the eyeball.
Pterygopalatine ganglia
Are located lateral to the sphenopalatine foramen, between the sphenoid and palatine bones. They receive preganglionic axons from the facial (VII) nerve and send postganglionic axons to the nasal mucosa, palate, pharynx, and lacrimal glands.
Submandibular ganglia
Are found near the ducts of the submandibular salivary glands. They receive preganglionic axons from the facial nerves and send postganglionic axons to the submandibular and sublingual salivary glands.
Otic ganglia
Are situated just inferior to each foramen ovale. They receive preganglionic axons from the glossopharyngeal (IX) nerves and send postganglionic axons to the parotid salivary glands.
Pelvic splanchnic nerves
Through these nerves, axons of parasympathetic preganglionic neurons extend to parasympathetic postganglionic neurons in terminal ganglia in the walls of the colon, ureters, urinary bladder, and reproductive organs.
Cholinergic neurons
Release acetylcholine (ACh).
What are the two types of cholinergic receptors?
- Nicotinic receptors
- Muscarinic receptors
What are the three major locations and effects of nicotinic receptors?
- Location: plasma membrane of postganglionic sympathetic and parasympathetic neurons.
Effect: excitation -> impulses in postganglionic neurons. - Location: chromaffin cells of adrenal medullae.
Effect: epinephrine and norepinephrine (NE) secretion. - Location: sarcolemma of skeletal muscle fiber (motor end plate).
Effect: excitiation -> contraction.
What are the three major locations and effects of muscarinic receptors?
- Location: effectors innervated by parasympathetic postganglionic neurons.
Effect: in some receptors, excitation; in others, inhibition. - Location: Sweat glands innervated by cholinergic sympathetic postganglionic neurons.
Effect: Increased sweating. - Location: skeletal muscle blood vessels innervated by cholinergic sympathetic postganglionic neurons.
Effect: Inhibition -> relaxation -> vasodialation
