Autonomic nervous system Flashcards
(30 cards)
Autonomic nervous system
Sympathetic and parasympathetic
What does the autonomic nervous system control?
Autonomic functions such as; heart rate, peristalsis, sweating, smooth muscle contraction in blood vessels, bronchi, sex organs, the pupils
What are the ANS control centers?
neural clusters throughout the body (ganglia)
What does the ANS interact with?
CNS in the brainstem and hypothalamus
What is the enteric nervous system?
- The enteric nervous system is considered a third autonomic division.
- Consists of ~600 million neurons in two neural plexuses (myenteric, submucous) lying within the walls of the gut.
- Involved in releasing a multitude of neurotransmitters to facilitate the motor, sensory, absorptive, and secretory functions of the gastrointestinal tract.
what it the flow chart of the ANS with the enteric included?
What is the importance of the ANS?
- Autonomic dysfunction can cause serious medical issues including:
- cardiac arrhythmias, high or low blood pressure, disturbances of gastrointestinal function
- Many commonly used medications (e.g., medications for treating high blood pressure, for regulating gastrointestinal function, or for maintaining a regular heartbeat) act on neurons within these systems.
What is the autonomic efferent (motor)?
- Organized more diffusely than in the somatic motor system; more slowly conducting, two neuron chain
- Postganglionic fibers outnumber the preganglionic neurons by 32:1; a single preganglionic neuron may control the autonomic functions of an extensive terminal area.
What are the two divisions of the ANS?
- sympathetic
- parasympathetic
two divisions are anatomically distinct and are different in terms of their pharamacological properties
Where does the sympathtic and parasympathetic arise?
Sympathetic : T1-L3
Parasympathetic: CN III, VII, IX, X and sacral levels S2-S4
Everything to do with the sympathetic division
- Arises from T1 to L3.
- Preganglionic fibers are short & myelinated.
- Postganglionic fibers are long and generally unmyelinated.
- Releases norepinephrine (NE) onto end organs.
- End organs include smooth muscle, cardiac muscle, glandular structures, parenchymal organs.
- Functions include increased heart rate, increased blood pressure, bronchodilation and increased pupil size.
- Ventral root to spinal nerve to white communicating ramus to sympathetic ganglion
- From here fibers may:
- synapse with ganglion cells, pass up or down the sympathetic trunk to synapse with ganglion cells at a higher or lower level
- Pass through the trunk ganglia and out to one of the collateral sympathetic ganglia (e.g., the celiac and mesenteric ganglia).
fight or flight
everything with the parasympathetic division
- Arises from the cranial nerves (III, VII, IX, X) and sacral spinal levels S2 -S4.
- Preganglionic fibers are long; postganglionic fibers are short.
- The dorsal motor nucleus of the vagus sends preganglionic fibers to innervate all organ systems within the chest, abdomen, and pelvic regions. (important)
- Releases acetylcholine (Ach) onto end organs
- Functions include increasing gastric secretions and peristalsis, slowing heart rate and decreasing pupil size.
rest and digest
Visceral afferent pathways (sensory)
- Visceral afferent fibers have their cell bodies in sensory ganglia of some of the cranial and spinal nerves. Most fibers are unmyelinated and have slow conduction velocities.
- Pain
Visceral afferent pathways (sensory) To the spinal cord
Enter by way of the middle sacral, upper lumbar, and thoracic nerves.
Sacral nerves: carry stimuli from the pelvic organs; nerve fibers are involved in reflexes of the sacral parasympathetic outflow that control various sexual responses, micturition, and defecation.
Thoracic and upper lumbar nerves: carry visceral pain impulses from the heart, upper digestive tract, kidney, and gallbladder; carry sensations such as hunger, nausea
Pain impulses from viscera may converge with pain impulses arising in a particular region of the skin, causing referred pain.
E.g., shoulder pain associated with gallstone attacks / left arm or throat pain associated with myocardial ischemia
Visceral afferent pathways (sensory) to the brainstem
Glossopharyngeal and vagus nerves carry sensations to the brainstem from the heart, great vessels, and respiratory and GI tracts.
Involved in reflexes that regulate blood pressure, respiratory rate and depth, and heart rate through specialized receptors or receptor areas.
Baroreceptors-stimulated by pressure; located in the aortic arch and carotid sinus
Chemoreceptors-sensitive to hypoxia; located in the aorta and carotid bodies.
Thermoreceptors in the skin send temperature signals to autonomic motor neurons that control sweating and shivering and to the hypothalamus.
Hierarchial control of the ANS
- Autonomic reflexes are mediated by the spinal cord, but descending pathways from the brain modify the reflexes.
- Bladder control involves a primitive reflex loop via parasympathetic preganglionic neurons at the S2, S3, and S4.
- When sensory impulses signal that the bladder is dilated, parasympathetic neurons excite the detrusor muscle and inhibit the urinary sphincters, thus emptying the bladder.
- This primitive detrusor reflex accounts for urinary function in infants.
- After early childhood, this reflex is modulated by descending influences, including voluntary sphincter release and suppression of urination.
Control of the ANS brainstem and nuclei
- Autonomic nuclei of the medulla control of cardiac and respiratory function, vasoconstriction and dilation, and reflexes such as swallowing, coughing, sneezing, and vomiting.
- Different brainstem nuclei are associated with sympathetic vs. parasympathetic output.
Control of the ANS Hypothalamus
- ANS projects to the hypothalamus via the brainstem reticular formation.
- Sensory input from the heart and stomach reaches the hypothalamus via projections from the ventrolateral medulla.
- Feeding behavior is controlled by inputs from thenucleus of thesolitary tractin the medulla that communicates taste and visceral inputs associated with feeding.
Horner’s syndrome
Disrupted sympathetic pathways to eye and orbit; decreased pupil size, drooping eyelid; decreased sweating on the affected side of the face.
Holmes-Adie Syndrome
- Damage to neurons in the ciliary ganglion that provides parasympathetic control of eye constriction; pupil is dilated and slow to react in response to direct light.
Raynauds disease
Disorder of the peripheral vascular innervation; affects the toes, the fingers, the edges of the ears, and the tip of the nose; parts are pale and cold, may progress to local asphyxia characterized by a blue gray cyanosis and dry gangrene.
Hirschspurng’s disease (megacolon)
Congenital lack of parasympathetic ganglia and abnormal nerve fibers in a segment of large bowel; consists of marked dilatation of the colon, accompanied by chronic constipation.
Sweat disorders (anhidrosis, hyperhidrosis)
Caused by sympathetic cholinergic failure; lesions can occur anywhere from the level of the cerebral cortex to the eccrine sweat glands. Anhidrosis can lead to hyperthermia, heat stroke, and death. No enough acetylcholine.
Multiple system atrophy
Rare, degenerative neurological disorder affecting your body’s autonomic functions, including blood pressure, breathing, bladder function and motor control; postural hypotension, urinary and bowel dysfunction, sweating abnormalities, sleep disorders, sexual dysfunction, CV proble
