NEURO: Quiz 3 Flashcards
Sympathetic efferent pathway: T1-L2
Origin: T1-L2 Destination: Body wall (anterior and posterior) -- Erector pili muscles -- Sweat glands -- Blood vessels
Preganglionic:
– Lateral horn – Ventral root – Spinal nerve
– White rami communicantes
– Paravertebral ganglion
Postganglionic:
– Gray rami communicantes – Ventral or dorsal rami
– Anterior or posterior trunk
Autonomic system organization
Sympathetic system:
– “Thoracolumbar system” (T1-L2)
– Function: Fight, flight, and fright
– Structure:
Short preganglionic neurons – Sympathetic ganglia – Long postganglionic neurons
– Innervates:
– Organs above diaphragm (e.g., eye, heart, lungs, lacrimal glands, salivary glands)
– Organs below diaphragm (e.g., liver, pancreas, stomach, kidney, genitalia, bladder)
– Blood vessels, sweat glands, and erector pili muscles of body wall and limbs
Parasympathetic system:
– “Craniocaudal system” (CN 3, 7, 9, 10; S2-4)
– Function: Homeostasis (“Rest and digest”)
– Structure:
Long preganglionic neurons – Short postganglionic neurons (near organ)
– Innervates:
– Organs above diaphragm (e.g., eye, heart, lungs, lacrimal glands, salivary glands)
– Organs below diaphragm (e.g., liver, pancreas, stomach, kidney, genitalia, bladder)
NOTE: No parasympathetics in limbs and body wall (anywhere with sweat gland)
Sympathetic efferent pathways: T1-4
Origin: T1-T4
(1) Destination: Head, neck, and upper limbs (erector pili muscles, sweat glands, blood vessels)
Preganglionic:
– Lateral horn – Ventral root – Spinal nerve – White rami communicantes
– Superior, middle, or inferior cervical ganglion (travel up from T1)
Postganglionic:
– Gray rami communicantes (LATERAL) – Ventral or dorsal rami – Head, neck, limbs
(2) Destination: Organs above diaphragm
(A) Heart and lungs
Preganglionic:
– Lateral horn – Ventral root – Spinal nerve – White rami communicantes
– Superior, middle, or inferior cervical ganglion OR paravertebral ganglion (same level)
Postganglionic:
– Gray rami communicantes (MEDIAL) – Sympathetic nerves – Heart and lungs
(B) Eyes, lacrimal gland, salivary glands, and cranial nerves
Preganglionic:
– Lateral horn – Ventral root – Spinal nerve – White rami communicantes
– Superior cervical ganglion (ONLY)
Postganglionic:
– Gray rami communicantes (MEDIAL) – Arteries – Eyes, glands, cranial vessels
Sympathetic efferent pathway: T5-L2
Origin: T5-L2
Destination: Organs below diaphragm
-- Liver, Kidney, Pancreas
-- Intestines, Stomach
-- Urinary tract and bladder
-- Genitalia
Preganglionic:
-- Lateral horn -- Ventral root -- Spinal nerve -- White rami communicantes
-- PASS THROUGH paravertebral ganglion -- splanchnic nerve
-- Great splanchnic = T5-9
-- Lesser splanchnic = T10-11
-- Least splanchnic = T12
-- Prevertebral ganglion
Postganglionic:
-- Organs below diaphragmSympathetic efferent pathways: T12-L2
Origin: T12-L2
(1) Destination: Pelvis and lower limbs (Erector pili muscles, Sweat glands, Blood vessels)
Preganglionic:
– Lateral horn – Ventral root – Spinal nerve – White rami communicantes
– Lower paravertebral ganglion (sympathetic chain)
Postganglionic:
– Gray rami communicantes – Ventral or dorsal rami – Pelvis and lower limbs
(2) Destination: Organs below diaphragm
– Liver, Kidney, Pancreas, Intestines, Stomach, Urinary tract and bladder, Genitalia
Preganglionic:
– Lateral horn – Ventral root – Spinal nerve – White rami communicantes
– PASS THROUGH paravertebral ganglion (at same OR lower level)
– Lumbar and sacral splanchnic nerves (lower ganglia only)
– Inferior or superior hypogastric plexuses (regions of ganglia)
Postganglionic:
– Organs below diaphragm
NOTE: Two ways to get to organs below diaphragm:
T5-L2 – splanchnic nerves – prevertebral ganglia – organs
T12-L2 – sympathetic chain – lumbar/sacral splanchnic nerves – hypogastric plexus –organs
Lesser and least splanchnic overlap with lumbar and sacral splanchnic (lower levels)
Sympathetic efferent pathway origins: Body wall Head, neck, and upper limbs Lower limbs and pelvis Organs above diaphragm Organs below diaphragm
Body wall (erector pili muscles, sweat glands, blood vessels) -- T1-L2 (via paravertebral ganglion)
Head, neck, and upper limbs (erector pili muscles, sweat glands, blood vessels)
– T1-4 (via cervical ganglia)
Lower limbs and pelvis (erector pili muscles, sweat glands, blood vessels)
– T12-L2 (via lower paravertebral ganglion)
Organs above diaphragm
- T1-4
- Heart and lungs (via cervical or paravertebral ganglia)
- Eyes, glands, and cranial vessels (via superior cervical ganglion)
Organs below diaphragm
- T12-L2 (via splanchnic nerves)
- T5-L2 (via hypogastric plexuses)
Sympathetic afferent pathway
Origin:
– Internal organs and smooth muscles of large vessels in limbs
Destination: Posterior horn of spinal cord (via dorsal root ganglion)
Information: Visceral sensory (pain, discomfort, baroreceptor, chemoreceptor)
Single neuron (NO SYNAPSE):
- Organ – PASS THROUGH ganglia (prevertebral and paravertebral)
- White rami communicantes – Dorsal root ganglion – Posterior horn
Parasympathic efferent and afferent pathways
Efferent:
Origin: CNs 3, 4, 7, 10: S2-4 Path: -- Long preganglionic -- Parasympathetic ganglion (near organ) -- Short postganglionic neuron
Afferent:
Origin: Organs
Path: CN 10 or S2-4
Autonomic disreflexia
= Reaction of autonomic system to overstimulation by noxious stimulus
– In SCI patients (most often above T6)
– Characterized by:
– Vasoconstriction below level of lesion
~ Cold, clammy skin and goose bumps
– Vasodilation above level of lesion
~ Bradychardia, flushed skin, headache, sweating, increased spasticity
– Severe hypertension ~ Seizure, cerebral hemorrhage, MI (life threatening)
Cause:
- Noxious stimuli below lesion triggers sympathetic reflex (visceral afferent)
- Vasoconstriction – Increase BP
- Carotid sinus and aortic receptors detect increased BP – Vasodilation above
- Signal to vasodilate can not travel below lesion – Vasoconsriction below
Common stimuli:
- Full bladder (#1) or rectal distension
- Pressure sores, urinary stones
- Environmental changes, cutaneous irritation (e.g., folded sock)
Treatment: Medical emergency
- DO NOT LAY PERSON DOWN (increases blood flow to brain)
- Remove stimulus (e.g., catheterization)
NOTE: Occurrence decreases over time (rare > 3 years)
Referred pain
= Pain perceived at location other than site of stimulus
Mechanism:
- Visceral afferent carrying info from organ (distortion or inflammation)
- Visceral afferent runs adjacent to somatic afferent when entering posterior horn
- Brain interprets visceral afferent info as coming from somatic afferent dermatome
- Pain is referred to body surface according to spinal level visceral afferent enters
Example:
– Visceral afferent from heart enters at T3-4 – referred pain to T3-4 dermatome
Receptors
Chemoreceptors
- Smell
- Taste
- Metabolic compounds (e.g., O2/CO2 in blood)
Thermoreceptors
– Changes in temperature
Photoreceptors
– Retina (rods and cones)
Mechanoreceptors
– Physical deformation
Nocioceptors
– Pain (also part of other categories, e.g., heat)
General senses
(1) Light touch = awareness and precise location of very delicate stimuli
- - Three types:
- - Two point sense = discriminate between two points on skin
- - Stereognosis = ability to recognize object without visual input (touch only)
- - Graphesthesia = ability to recognize numbers and letters drawn on skin
(2) Crude touch = aware of touch but cannot discriminate
- - Same types of receptors as light touch, just fewer
(3) Pressure = deep touch (compression of subcutaneous tissue beneath dermis)
(4) Vibration = tuning fork over bony prominence felt by subcutaneous tissue
(5) Proprioception = limb position and motion sense (active and passive)
- - Ability to sense location and movement of one part of body in relation to other
(6) Pain
- - Two types:
- - First pain = sharp, pricking, well localized
- - Slow pain = dull, achy, burning, diffuse (usually after first pain)
(7) Temperature = distinguishing hot and cold
Sensory homunculus regions
Postcentral gyrus:
– Lower extremity/foot = Medial
– Trunk = Superior medial
– Upper extremity/hand = Superior lateral
– Face = Lateral
Encapsulated sensory receptors
= Surrounded by mechanical barrier (capsule)
Cutaneous:
- Pacinian corpuscle = Vibration
- Highly adaptive (no longer send signal if constant), but vibratio continuously changing stimulus so still sensed
- Subcutaneous
- Meissner corpuscle = Touch
- Vertical pressure
- Dermis, near border with epidermis
- Ruffini ending = Pressure
- Dermis, deeper than Meissner (requires more compression)
Muscle:
– Muscle spindles = Stretch (none with isometric contraction)
– Annulospiral endings = Onset of stretch
– Spiral around central region of intrafusal fibers
– Speed and change in length of fibers
– Slow rate of firing once muscle in constant stretch
– Flower spray endings = Maintain discharge during stretch (isometric contraction)
– On each side of annulospiral endings
– Less sensitive
Tendon:
– Golgi tendon organ = Tension in tendon
– Higher threshold than muscle spindle
– Stimulus requires greater stretch (near injury)
Nonencapsulated somatosensory receptors
= Surrounded by only thin capsule or none
- Endings around hair = Touch
- Sense movement of hair at base of hair root
- Dermis
- Merkel endings (tactile disc) = Touch
- Dermis (near border of epidermis)
- Free nerve endings = Touch, pain, temperature, itch
- Dermis, deeper
