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47 Cards in this Set
- Front
- Back
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What 3 things does the ANS control?
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Smooth muscle
Cardiac muscle Glands |
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How does ANS compare to somatic in number of neurons?
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Somatic - LMN projects directly from CNS to striated muscle
ANS - 2 neurons system to reach target cells (preganglionic and postganglionic neurons) |
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Describe the ANS and somatic nervous system neurons.
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Somatic - large diameter, thickly myelinated alpha motor fibers
Preganglionic ANS - small diameter, lightly myelinated beta fibers Postganglionic - unmyelinated C fibers |
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SNS neurons: location? length of neurons?
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IML region of T1 to L2
Pre = Short Post = long |
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PNS neurons: location? length?
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Arise from the brainstem (III, VII, IX, X) and cells in spinal cord gray matter from levels S2-S4
Pre = long Post = short |
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Describe the neurotransmitters of the ANS.
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Both systems use ACh as preganglinic NT
PNS uses ACh as the postganglionic NT SNS uses NE as the postganglionic NT except when innervating sweat glands, where ACh binds muscarinic receptors |
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SNS: pathway?
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Posterior hypothalamus
Travel laterally in brainstem, close to spinothalamic tract Synapse in IML from T1 and L2 Project out via ventral root Leave via white communicating rami to enter the paravertebral sympathetic chain ganglia Synapse in paravertebral ganglia, prevertebral ganglia, and adrenal medulla. |
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What happens after synapse in paravertebral ganglia?
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Can synapse at the level the exit or travel up or down. Exit via gray communicating rami to innervate heart, heart, lungs, peripheral spinal nerves.
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What happens after synapse in prevertebral ganglia?
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Preganglionic neuron axons pass through the sympathetic chain without synapsing and travel out as sympathetic splanchnic nerves that synapse in the celiac, superior mesengeric, or inferior mesenteric prevertebral ganglia. Innervate abdominal and pelvis viscera.
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What can chromaffin cells of the adrenal medulla be thought of?
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Modified postganglionic sympathetic neurons that have lost their axons. Release NE and epi into circulation.
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How can Horner's syndrome be pharmacologically confirmed? Why?
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By applying drops of a solution containing cocaine, which inputs NE reuptake. When applied to a normal eye, there will be a pupillary dilation. In the setting of any lesion that disrupts the sympathetic pathway from the hypothalamus to the pupil, the pupil will fail to dilate as there is no NE being released in the synaptic cleft.
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How do you distinguish the location of the lesion once a Horner's syndrome is established?
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3rd order vs. 1st or 2nd order differentiated with hydroxyamphetamine, which causes a release of NE from intact 3rd order nerve terminals. The response in 3rd order neurons lesions the response is absent or greatly attenuated.
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What results with extensive loss of pre- and/or postganglionic sympathetic neurons?
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Orthostatic hypotension
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Describe the pathway for sympathetic innervation of the eye/face.
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In cervical region at C1-C4, top four paravertebral chain gangli fuse to form the SCG. From the SCG, postganglionic fibers ascend along the internal and external carotic arteries en route to target cells, including pupillary dilators, tarsal muscles of the eyelids, and sweat glands of the head.
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Give the general pathway of the parasympathetic nervous center.
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Anterior hypothalamus
Projects to brainstem nuclei, then project to ganglia near the target organ Short postganglionic neurons then innervate target cells in the immediate vicinity |
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What else is the PNS known as and why?
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Craniosacral division, as the fibers exit the CNS via III, VII, IX, and X and the sacral spinal cord (S2-S4)
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What is the function of the parasympathetic component of CN VII?
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Submandibular and sublingual glands
lacrimal glands Mucous glands of nose, paranasal sinuses, and hard and soft palates |
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What is the parasympathetic nucleus of CN VII and where is it located?
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Superior salivatory nucleus
Loosely arranged in the mid-pons, adjacent to motor VII nucleus |
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What is the input to the superior salivatory nucleus?
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Limbic and olfactory systems via the hypothalamus
Pain fibers in corna via spinal trigeminal tract Taste fibers via rostral nucleus solitarius |
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Give the pathway of CN VII after superior salivatory nucleus.
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Exit the pons
Travel in nervus intermedius Genicultae ganglion (no synapse) Divide and travel in... Greater petrosal nerve to pterygopalatine ganglion to lacrimal glands and mucous glands Chorda tympani to submandibular ganglion to salivary glands |
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What is the superior salivatory nucleus near and what does this result in?
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Adjacent to motor VII nuclei, so a lesion of the motor VII nucleus or its efferent fibers may result in ipsilateral loss of salivation and tearing.
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Inferior salivatory nucleus: location? pathway?
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Adjacent to nucleus ambiguus
Fibers exit the lateral medulla and travel toward parotid gland via the lesser petrosal nerve before synapsing in the otic ganglion. Travel to parotid gland |
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Dorsal motor nucleus of the vagus: contents?
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Preganglionic parasymp fibers that innervate the viscera of the thorax and abdomen
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Lesion of dorsal motor X (heart)
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Tachycardia
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What other parasympathetic neurons besides X are involved in heart rate? Function?
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Parasymp neurons of nucleus ambiguus - when stimulated there is a decrease in HR (cardioinhibitory effect)
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What results from dorsal motor X innervation of the lungs?
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Smooth muscle constriction of bronchioli and increased secretion of the bronchial glands
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What results from dorsal motor X innervation of the gut?
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Increased peristalsis and secretion of gastric and intestinal glands, and relaxation of the sphincters
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Functions of the components of the tractus solitarius
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Rostral - relays taste information
Caudal - relays general viscerosensory information from the body to areas of the brain involved in autonomic control of the viscera |
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Describe the pathway involving the caudal tractus solitarius.
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Most of general visceral afferent information reaches the medulla via sensory afferents of CN X. First order neuron cell bodies in inferior ganglia X. Central processes enter the tractus solitarius and synapse. Then projects to dorsal motor X to elicit a response.
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What are the 2 baroreceptors and what CNs are they associated with?
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Carotic sinus - CN IX
Aortic body - CN X |
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What results from an increase in arterial blood pressure concerning the baroreceptors?
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Central processes synapse in caudal nucleus solitarius, initiating cardioinhibitory and sympathoinhibitory responses.
Cardioinhibitory: neurons project to dorsal motor X and nucleus ambiguus, which subsequently send signals to cardiac plexus that induces decrease in HR Sympatho-inhibitory response: neurons project to and inhibit preganglionic sympathetic neurons in IML, decreasing symp outflow to blood vessels. |
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Chemoreceptors: function?
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Detect changes in arterial oxygen, carbon dioxide, and pH
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Describe the function of chemoreceptors.
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Decrease pO2, increase PCO2, and increase in H ion concentraion will increase afferent firing.
Caudal nucleus solitarius cells then project to respiratory centers in the medulla that increase the depth and rate of breathing. |
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Give the pathway of the sacral spinal cord region of the PNS (S2-S4).
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Reticular formation
Reticulo-spinal tract IML Leave the ventral root as pelvic splanchnic nerves Walls of visceral organs - synapse on ganglion cells |
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What does the sacral region of the PNS innervate?
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Smooth muscle of bladder
Large intestine beyond left colic flexure Rectum Reproductive organs Genitalia |
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What happens when the bladder fills?
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Muscle spindles are stretched and signal the preganglionic parasympathetic cells at S2-S4. These send axons out the ventral roots to synapse in ganglia near the bladder. These innervate the detrusor muscle, contracting the bladder.
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What 2 general categories of things can cause incontinence?
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Dysfunction of sensorimotor neural pathways to bladder or urethral sphincter muscles (neurogenic bladder)
Physical problems with the pelvic floor |
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What results from an UMN lesion to the bladder arc?
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Acute lesion - flaccid bladder and urinary retention, can get overflow incotinence
After recovery, result in spasticity, causing detrusor contraction with a smaller bladder volume. Results in increase urinary frequency as well as urgency. |
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What results from LMN lesions of the bladder arc?
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Weak or absent detrusor activity, resulting in bladder areflexia with overflow incontinence. If sensory afferents are affected, there is no urge to void. If sensation is intact, there is conscious perception of the need to void, but inability to do so.
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Pure Autonomic Failure: define. Most common complaint?
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Degenerative disorder of the symp and parasymp nervous systems without other CNS involvement
Orthostatic hypotension |
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What are other symptoms of pure autonomic failure besides orthostatic hypotension?
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Urinary dysfunction
Blurry vision Hypohydrosis Constipation Sexual dysfunction |
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Treatment of orthostatic hypotension in PAF?
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Behavioral modification
Lower extremity compression stockings Increased water and salt intake Medications |
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Autonomic dysreflexia: define.
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Life-threatening condition that occurs in individuals with spinal cord injuries above the level of symp splachnic outflow and involves a reflex of massive sympathetic discharge
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Describe the pathway after stimulation in autonomic dysreflexia.
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Below the level of the lesion, peripheral sensory nerves transmit impulses toward cortex. At level of injury, ascending pain signals are blocked and reflexively synapse on preganglionic sympathetic neurons in IML, initiating sympathetic hyperactivity in response to noxious stimulus.
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What are the symptoms of autonomic dysreflexia?
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Piloerection
Arterial vasoconstriction below level of injury causing HTN Bradycardia via cardioinhibitory response Vasodilation above the level of injury |
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What are the 2 pharm treatments of organophosphoate poisoning?
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Atropine - anticholinergic
Pralidoxime - cholinesterase reactivating agent |
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What are the symptoms of cholinergic toxicity? Why?
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Parasymp overdrive (due to ACh)
DUMBLS: Diarrhea Urination Miosis Bradycardia/bronchospasm Emesis Lacrimation Salivation |
