Unit 4_Autonomic Nervous System Flashcards
What nervous system presents as the following:
- Maintains homeostasis
- Vegetative (digestive) & visceral (organs) functions
- Generally, an involuntary system
Minimal voluntary control
Autonomic Nervous System (ANS)
What are the following associated with?
General sensations: Pain, temp, touch
Special senses: vision, auditory, vestibular, etc.
Visceral afferents: through nucleus of solitary tract (CNs IX &X)
Sensory Afferents Stimulate Reactions to the ANS
What do the following make up:
Efferents (the True ANS system)
Two functional systems
1. Sympathetic (SNS)
2. Parasympathetic (PNS)
Innervate smooth muscle, the heart, glands, and organs
*NO direct innervation of skeletal muscle
ANS
What kind of neurons sit within the brainstem and spinal cord inside the cns?
preganglionic
What kind of neurons include cells situated in ganglion outside cns?
postganglionic
What neuron includes:
Sympathetic: T1-L2 or L3 (Lateral Horn)
Parasympathetic: CN nuclei 3,7,9,10 (autonomic nuclei) and sacral spinal cord S2-S4 (lateral horn)
Preganglionic Neurons
What neuron includes:
Sympathetic:
A. Sympathetic trunks
B. three specialized prevertebral areas past the trunk:
1. celiac ganglion
2. superior mesenteric ganglion
3. inferior mesenteric ganglion
Axons go to the organs
Parasympathetic: various ganglions are located very near the target organ; very far from the spinal cord and brainstem
Postganglionic Neurons
What kind of neurotransmitters include the following:
Preganglionic cells release ACH onto postganglionic cell
Postganglionic cells release epinephrine and norepinephrine except on sweat glands where they release ACH
There also co-transmitters
Sympathetic
What kind of neurotransmitters includes the following:
Both pre & postganglionic cells use ACH
There can also be co-transmitters
Parasympathetic
What ANS includes the following:
- AKA thoracolumbar division
- preganglionic neurons located in T1-L3 (Lateral Horn)
- axons exit spinal cord through ventral root
- can do one of 2 things:
1. enter synaptic chain on either side of the cord
*synapses on postganglionic neuron in chain and release ACH
*axon of postganglionic cell travels in peripheral nerves to target organs where it synapses and releases norepinephrine (except sweat glands where they release ACH)
2. go directly to neurons in prevertebral ganglion
*synapse on postganglionic neuron in ganglion and release ACH
*axons from postganglionic neurons go direct to target organ and release norepinephrine
The target tissue or target organ receives norepinephrine from the postganglionic cell (except sweat glands). The receptors on the target organ are divided into 2 classes:
1. alpha adrenergic receptors - when these receive norepinephrine they excite the target tissue except in the GI system where they inhibit the target tissue.
2. beta adrenergic receptors - when these receive norepinephrine they inhibit the target tissue except in the heart where it excites the heart
Sympathetic
What organ has sympathetic innervation only and includes the following:
- There is only one efferent neuron
- When stimulated, this organ releases epinephrine
- This serves as a mechanism to release hormones quickly into the blood; “FIGHT OR FLIGHT”
adrenal medulla
What do the following organs have in common?
- Adrenal medulla
- sweat glands
- piloerector muscles
- peripheral blood vessels (in skin)
sympathetic innervation only
What do most organs contain?
both sympathetic and parasympathetic innervation
What kind of ANS innervation includes the following:
- follows 2 neuron pathway rules
- preganglionic neuron sits in thoracic cord axons, leave the spinal cord, and travel to postganglionic neurons either in the stellate or superior cervical ganglion
- Axons from these cells ascend and go to blood vessels and glands of the face through cranial nerves
- Goes to the eye to dilate the pupil through CN V (ophthalmic division)
- This is controlled via descending axons from the hypothalamus
Sympathetic innervation of face and head
What ANS is involved in catabolic responses (energy expediting)?
Sympathetic
What includes the following:
- aka cranio-sacral division
- cranial division consists of brainstem CN autonomic nuclei and their axons
- sacral division innervates urinary system, the lower colon, anal sphincter, and the reproductive system
Parasympathetic Nervous System
What includes the following:
- located in CN 3,7,9,10 and lateral gray horn of S2-S4
- CN nuclei include Edinger Westphal (III), lacrimal and superior salivatory (VII), inferior salivatory (IX) and dorsal vagal (X)
- axons are long; exit cranial nerves or S2-S4 and travel to synapse on postganglionic neurons where they release ACH
Preganglionic Neurons
What is located in ganglia near target organs and axons leave the ganglia to innervate structures and release ACH?
Postganglionic Neurons
What conserves energy (anabolic system) and features opposite actions of sympathetic?
Parasympathetic Nervous System
What tissue/organ features the following:
Sympathetic Stimulation Causes: Dialation
Parasympathetic Stimulation Causes: Constriction (CN III and Edinger Westphal nucleus in the midbrain)
Pupil of the Eye
What tissue/organ features the following:
Sympathetic Stimulation Causes: Increased sweat production
Parasympathetic Stimulation Causes: NONE
Sweat Glands
What tissue/organ features the following:
Sympathetic Stimulation Causes: Increased heart rate
Parasympathetic Stimulation Causes: Decreased heart rate (CN X and Dorsal vagal nuclei in medulla)
Heart
What tissue/organ features the following:
Sympathetic Stimulation Causes: Stimulation causes constriction and removal of stimulation causes dilation
Parasympathetic Stimulation Causes: NONE
Blood vessels
What tissue/organ features the following:
Sympathetic Stimulation Causes: Relaxation-bronchal dilation
Parasympathetic Stimulation Causes: Constriction (CN X)
Lungs
What tissue/organ features the following:
Sympathetic Stimulation Causes: Little effect
Parasympathetic Stimulation Causes: Contraction (sacral cord)
Bladder: detrusor muscle
What tissue/organ features the following:
Sympathetic Stimulation Causes: Contraction
Parasympathetic Stimulation Causes: Relaxation (sacral cord)
Bladder: Sphinctors
What are critical for normal physiological functions? These include baroreceptor reflex, the micronutrition reflex and the reflexes important for defecation and sexual function.
Autonomic Reflexes
What controls short term blood pressure changes? Increased blood pressure is sensed by visceral afferent nerve fibers in the carotid sinus and aortic arch this sensation is carried back to CN IX (from carotid sinus) and X (from aortic arch).
The information synapse on reticular cells in the medulla responsible for cardiovascular regulation.
These cells send axons down to the presympathetic ganglia cells lateral horns to reduce the stimulation to the smooth muscle of blood vessels and cause them to relax or dilate which will reduce the blood pressure.
Baroreceptor Reflex
What is the effect of autonomic reflexes?
To reduce sympathetic activity
What controls the filling and emptying of the bladder? This reflex comes under our conscious control only up to an extent.
As the bladder fills with urine, the PNS reduces the amount of contraction and the SNS activates the sphincter to keep the urine from flowing out.
As it continues to fill mechanoreceptors in the bladder walls sense the stretch on the bladder and send this to two locations:
1. The micronutrition reflex center in the pons
2. The cerebral cortex sensory area to sense that the bladder is full consciously
The micturition center in the pons then sends descending signals down to cause relaxation of the sphincter (inhibits SNS) and contraction of the bladder detrusor muscle (excites PNS). This microturition center is controlled by the cortex which can inhibit the reflex and stop urination or excite the reflex and allow urination.
Micturition Reflex
Damage to the spinal cord above the sacral cord often damages what and bladder control is lost?
The ascending and descending connections to the micturition center
What are organized from anterior to posterior, and midline to lateral?
Regions of the hypothalamus
What does the (lateral) hypothalamus project to the (lateral) medulla, where the cells that drive autonomic systems are located?
These include the Parasympathetic Vagal Nuclei and a group of cells that descend to the Sympathetic System in the Spinal Cord.
With access to these systems, the hypothalamus can control heart rate, vasoconstriction, digestion, sweating, etc.
Neural signals to the autonomic system
What features magnocellular neurons sending axons directly to the posterior pituitary and secrete oxytocin and vasopressin directly into the bloodstream?
Parvocellular neurons secrete peptides that regulate release of anterior pituitary hormones.
Endocrine signals to/through the pituitary
Where do the descending autonomic pathways originate from?
the hypothalamus and various brain stem nuclei
What is the major hypothalamic nucleus for controlling sympathetic and parasympathetic functions?
the paraventricular nucleus
What other hypothalamic sites contribute axons to the descending visceromotor pathways?
- neurons in the lateral hypothalamic zone
- the dorsomedial hypothalamic nucleus
- the posterior hypothalamus
What is on the lateral horn of spinal cord?
a hypothalamic projection
What have descending inputs the ANS spinal cord? Spinal cord injuries can disrupt that control.
Both the hypothalamus and brainstem areas
What clinical implication of ANS includes visceral afferents coming from the gut through dorsal root ganglion? It sets up reflex connections.
Treatment: heat
Irritated gut
What clinical application of ANS includes the following:
- pain felt at a site distant to the cause of pain
- has to do with visceral afferents (and is related to)
- It is the convergence of somatosensory and visceral afferents on a single pain tract cells that causes referred pain
- distinguish between shoulder pain and referred pain from heart
*reproduction of pain in shoulder
*vital sign
Referred pain
What clinical application of ANS includes sympathetic innervation to the face is interrupted by a lesion in the descending sympathetic innervation to the face?
Ptosis
Anhidrosis
Miosis
Horner’s Syndrome
What clinical application of ANS includes a lesion in high thoracic or cervical cord (SCI) - life threatening?
Autonomic Dysreflexia
