Week 7 Neuro

Sympathetic Nervous System vs. Parasympathetic Nervous System

• The sympathetic nervous system mobilizes energy and maintains optimal blood supply to organs.
• The parasympathetic nervous system conserves energy and stores it.
• The sympathetic nervous system is often associated with "fight or flight".
• The parasympathetic nervous system is often referred to as "rest and digest".
• Sympathetic cell bodies are located in the thoracic and L1-L2 lumbar regions of the spinal cord.
• Parasympathetic cell bodies are located in the brainstem via cranial nerves 3, 7, 9, and 10, and at sacral levels.

Effects on Specific Organs: Sympathetic vs. Parasympathetic Input

• Sympathetic input opens eyelids, dilates pupils, constricts blood vessels, dilates the trachea and heart vessels.
• Sympathetic input increases heart rate, slows stomach digestion, increases glucose release, decreases GI peristalsis, and decreases bladder emptying and reproductive organ stimulation.
• Parasympathetic input constricts pupils, increases salivary and lacrimal gland secretion.
• Parasympathetic input narrows trachea bronchi, increases tracheal secretion, relaxes and slows the heart.
• Parasympathetic input increases stomach secretion and peristalsis, reduces glucose release and empties the bladder, and increases reproductive organ function.

Two-Order Neuron Pathway

• Both sympathetic and parasympathetic systems use a two-neuron pathway.
• The sympathetic pathway involves a short preganglionic fiber releasing acetylcholine and a long postganglionic fiber releasing norepinephrine.
• The parasympathetic pathway involves a long preganglionic fiber and a short postganglionic fiber, both releasing acetylcholine.

Effects of Cholinergic and Anticholinergic Drugs

• Cholinergic drugs accelerate cholinergic effects.
• Anticholinergic drugs inhibit cholinergic effects, particularly in the parasympathetic system relaxing constricted bronchi.

Autonomic Storming

• Involves the dysregulation of the autonomic nervous system and excessive sympathetic output.
• Acute brain injury disrupting inhibitory centers in the brain, causing the exaggerated sympathetic response is hypothesized.
• Increased heart rate, blood pressure, and respiratory rate are all common autonomic storming signs.

Autonomic Dysreflexia

• It defines an imbalance between the parasympathetic and sympathetic nervous systems.
• It results from a spinal cord lesion at or above T6.
• Noxious stimuli below the lesion trigger an exaggerated sympathetic response, causing vasoconstriction and increased blood pressure.
• The brain attempts to counteract this by initiating parasympathetic activity, resulting in decreased heart rate, facial flushing, and pounding headache.

Autonomic Dysreflexia Causes

• It is an imbalance between the parasympathetic and sympathetic nervous systems, resulting from a lesion in the spinal cord at or above the T6 level.
• Noxious or painful stimuli below the level of the T6 lesion are common causes.
• These stimuli are typically bowel or bladder issues, bowel obstruction or constipation, bladder obstruction, kinked catheter, and overextended bladder.

Neurogenic Orthostatic Hypotension

• It causes a decrease of at least 20 mmHg in systolic blood pressure.
• It causes a decrease of at least 10 mmHg in diastolic blood pressure.
• It causes the heart rate to increase of 20 beats per minute during the first three minutes after moving from supine to sitting.
• A person may have a blood pressure of 210/110 along with a heart rate in the 40-50 beats per minute range in cases of autonomic dysreflexia
• It is caused by a disruption of signaling between the brainstem and the sympathetic preganglionic fibers, which prevents the vasomotor system from triggering vasoconstriction.

Orthostatic Hypotension Treatments

• If a patient feels like they are going to pass out, slide them back down to a supine position.
• In extreme cases, the patient might be put in the Trendelenburg position, where the head is lower than the feet.
• If the patient's blood pressure is fine when standing, increasing activity might be appropriate, such as ankle pumps or leg kicks.
• Encourage fluid intake if dehydration is suspected.
• The nutrition should be observed.