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Autonomic Nervous System
Terms in this set (30)
What types of processes does the autonomic nervous system (ANS) regulate?
regulates unconscious processes that maintain homeostatis
BP, body temperature, respiratory airflow
innervates smooth muscle, cardiac muscle, glands, and is also called visceral motor system
What are baroreceptors?
arterial stretch receptors that detect high blood pressure. They are found in the heart.
What cranial nerve sends signals to the brains stem from the baroreceptors?
The afferent neuron in glossopharyngeal nerve carries signal to medulla (CNS).
What cranial nerve sends efferent signals to the heart to reduce heart rate?
The vagus nerve (efferent) signals travel to the heart, which causes heart to slow reducing BP
What are the 2 divisions of the ANS?
Sympathetic and Parasympathetic divisions
prepares body for physical activity "fight or flight"
-increases heart rate, BP, pulmonary airflow, blood glucose levels, blood flow to cardiac and skeletal muscles while reducing blood flow to skin and digestive tract
calms many body functions and assists in bodily maintenance "rest and digest" - digestion and waste elimination; Miosis (papillary constriction), bradycardia, bronchoconstriction, lacrimation (tearing), urination, erection, salivation, GI secretions and motility, and defecation
What is meant by autonomic tone?
autonomic tone is the background rate of activity of the ANS
-it is the balance between the sympathetic and parasympathetic tone
-parasympathetic tone maintains smooth muscle tone in the intestines and holds resting heart rate down to about 70-80 beats/minute
-if the parasympathetic Vagus nerves to the heart are cut the heart beats as its own intrinsic rate of about 100 beats/minute
-sympathetic tone keeps most blood vessels partially constricted and this maintains BP; loss of sympathetic tone can cause such a rapid drop in BP that a person goes into shock
Where are sympathetic ganglia located and what neurotransmitter is used here? What type of receptor?
-sympathetic ganglia are located in the paravertebral chain or prevertebral
-sympathetic preganglion neurons use Ach when they synapse in ganglia
-Ach binds to 2 classes of receptors (nicotinic receptors and muscarinic receptors)
-parasympathetic ganglia are located in or near the effector organ
Where do the cell bodies of preganglionic sympathetic axons reside?
in the lateral horns of spinal cord (T1-L2) thoracolumbar
(inner core): is a modified sympathetic ganglion stimulated by preganglionic sympathetic neurons that send fibers that penetrate the cortex of the gland and terminate on the chromatin cells of the adrenal medulla
What do cells of the adrenal medulla release when stimulated?
chromaffin cells of the adrenal medulla secrete neurotransmitters (hormones) into the blood
-catecholamines (85% epinephrine, 15% nor epinephrine, and a trace of dopamine)
What neurotransmitter stimulates sweat glands?
What cranial nerves have parasympathetic axons associated with them?
3, 7, 9, 10
Oculomotor Nerve (III)
CN III sends preganglionic axons to the ciliary ganglion (Ach), postganglionic stimulates via (Ach) the papillary constrictor and the ciliary muscle, which thickens lens for near vision
Facial Nerve (VII)
-Sends axons to the pterygpalatine ganglion (Ach) which send postganglionic axons (Ach) to lacrimal glands (taers) and nasal glands (mucus)
-Sends axons to the submandibular ganlion (Ach) which send postganglionic axons (Ach) to the sublingual and submandibular salivary glands
-Sends axons to the Otic ganglion (Ach) which send postganglionic axons to the parotid salivary gland
Vagus Nerve (X)
-viscera as far as proximal 2/3 of colon
-cardiac pulmonary, and esophageal plexus
Which of these nerves serve the head?
Cranial nerves III, VII, IX: responsible for parasympathetics to the head
Which of these nerves serve the thorax and abdomen?
Cranial nerve X and sacral spinal cord segments to all viscera of the body cavities
Which autonomic ganglia are in or near the target tissue, sympathetic or parasympathetic?
parasympathetic ganglia are located in or near the effector organ
What is the enteric nervous system?
the nervous system of the digestive tract
-composed of 100 million neurons found in the walls of the digestive tract (no components in CNS)
-has its own reflex arcs
-regulates motility of esophagus, stomach, and intestines, and secretion of digestive enzymes and acid (also requiring regulation by the ANS)
Where are alpha 1 adrenergic receptors found?
-found on vascular smooth of the skin and viscera, GI and bladder sphincters, and radial muscle of the iris
-produce excitation (contraction or constriction)
What is the mechanism of action of the alpha 1 adrenergic receptors?
mechanism of action: Inositol triphosphate (IP3) and increase intracellular calcium ion concentration
What drug is an agonist for the alpha 1 adrenergic receptors?
Phenylephrine is an agonist-used as decongestant
most of viscera receive nerve fibers from both parasympathetic and sympathetic divisions; both divisions do not normally innervate an organ equally
enhance sympathetic activity
stimulate receptors or norepinephrine release
Phenylephrine in cold remedies - stimulate alpha 1 receptors dilating bronchioles and constricting nasal blood vessels to reduce swelling in nasal mucosa allowing ease of breathing (decongestant)
suppress sympathetic activity
block receptors or inhibit norepinephrine release
Propranolol is a beta-blocker that reduces hypertension (high blood pressure) by blocking Beta adrenergic receptors on heart and blood vessels
suppress parasympathetic activity
Ganglionic, neuromuscular (nicotinic cholinergic)
M1 thru M5 (muscarinic cholinergic)
Atropine blocks muscarinic receptors and is sometimes used to dilate pupils for eye examination and to dry the mucous membranes of the respiratory tract before inhalation anesthesia
Enhance parasympathathetic activity
-Pilocarpine relieves glaucoma (excessive pressure in the eyeball) by dilating blood
vessels that drain fluid from the eye