Neurology - 2 Flashcards
List the vagal nuclei.
- Nucleus solitarius
- Nucleus ambiguus
- Dorsal motor nucleus
What is the function of nucleus solitarius and which CN are involved?
Visceral sensory information (eg, taste, baroreceptors, gut distention) - CN VII, IX, X
What is the function of nucleus ambiguus?
Motor innervation of pharynx, larynx, upper esophagus (eg, swallowing palate elevation) - CN XI, X, XI (cranial portion)
What is the function of the dorsal motor nucleus?
Sends autonomic (parasympathetic) fibers to heart, lungs, upper GI - CN X
List the 5 cranial nerve reflexes.
- Corneal
- Lacrimation
- Jaw jerk
- Pupillary
- Gag
What are the afferent and efferent components of the corneal reflex?
A - V1 ophthalmic (nasociliary branch)
E - VII (temporal branch - orbicularis oculi)
What are the afferent and efferent components of the lacrimation reflex?
A - V1 (loss of reflex does not preclude emotional tears)
E - VII
What are the afferent and efferent components of the jaw jerk?
A - V3 (sensory - muscle spindle from masseter)
E - V3 (motor - masseter)
What are the afferent and efferent components of the pupillary reflex?
A - II
E - III
What are the afferent and efferent components of the gag reflex?
A - IX
E - X
What are the muscles of mastication, their function, and innervation?
3 muscles close the jaw - masseter, temporalis, medial pterygoid (M’s munch)
1 muscle opens the jaw - lateral ptyergoid (lateral lowers)
All are innervated by V3
How many pairs of spinal nerves are there?
31 pairs (8cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal)
Where do the spinal nerves exit?
C1-C7 exit above the corresponding vertebra
C8 exists below C7 and above T1
All others - exit below
Where is a lumbar puncture usually performed and why?
L3-L4 or L4-L5 (level of cauda equina)
Spinal cord ends at lower border of L1-L2; subarachnoid space (contains CSF) extends to lower border of S2
Goal - obtain CSF without damaging the spinal cord
List the ascending tracts of the spinal cord.
- Dorsal column
2. Spinothalamic
List the descending tracts of the spinal cord.
- Corticospinal tract
What is the function of the ascending tracts of the spinal cord?
- Dorsal column - pressure, vibration, fine touch, proprioception
- Spinothalamic tract (lateral) - pain, temperature
- Spinothalamic tract (anterior) - crude touch, pressure
What is the function of the descending tract of the spinal cord?
Voluntary movement
Describe the dorsal column pathway.
- Sensory nerve ending -> bypass pseudounipolar cell body in dorsal root ganglion -> enter spinal cord -> ascend ipsilaterally in the dorsal columns (fasciculus gracilis from the lower body/legs, fasciculus cuneatus from the upper body/arms)
- Synapse #1 in the nucleus gracilis or nucleus cuneatus (ipsilateral medulla)
- Decussates in the medulla -> ascends contralaterally in the medial lemniscus
- Synapse #2 in the VPL (thalamus) -> sensory cortex
Describe the spinothalamic tract.
- Sensory nerve ending (A-delta and C fibers) -> bypass pseudounipolar cell body in dorsal root ganglion -> enter spinal cord
- Synapse #1 in the ipsilateral gray matter (spinal cord)
- Decussates at the anterior white commissure -> ascends contralaterally
- Synapse #2 in the VPL (thalamus) -> sensory cortex
Describe the lateral corticospinal tract.
- UMN: cell body in the primary motor cortex -> descends ipsilaterally through the internal capsule, most fibers decussate at the caudal medulla (pyramidal decussation) -> descend contralaterally
- Synapse #1 - cell body of anterior horn (spinal cord)
- LMN: leaves spinal cord
- Synapse #2 - NMJ -> muscle fibers
List the clinical reflexes and what they test.
- Achilles reflex - S1, S2 (buckle my shoe)
- Patellar reflex - L3, L4 (kick the door)
- Biceps and brachioradialis reflexes - C5, C6 (pick up sticks)
- Triceps reflex - C7, C8 (lay them straight)
- Cremasteric reflex - L1, L2 (testicles move)
- Anal wink reflex - S3, S4 (winks galor)
Why might primitive reflexes re-emerge in adults?
Frontal lobe lesion (frontal lobe normally inhibits them)
What is the moro reflex?
Abduct/extend arms when started, and then draw together (“Han on for life”)
What is the rooting reflex?
Movement of head toward one side if cheek or mouth is stroked (nipple seeking)
What is the sucking reflex?
Sucking response when roof of mouth is touched
What is the palmar reflex?
Curling of fingers if palm is stroked
What is the plantar reflex?
Dorsiflexion of large toe and fanning fo other toes with plantar stimulation (Babinski sign in adult)
What is the galant reflex?
Stroking along one side of the spine while the newborn is in ventral suspension (face down) causes lateral flexion of lower body toward stimulated side
Nerve - posterior half of the skull dermatome
C2
Nerve - high turtleneck shirt dermatome
C3
Nerve - low-collar shirt dermatome
C4
Nerve - includes the thumbs dermatome
C6
Nerve - at the nipple dermatome
T4
Nerve - at the xiphoid process dermatome
T7
Nerve - at the umbilicus dermatome
T10
Nerve - at the inguinal ligament dermatome
L1
Nerve - includes the kneecaps dermatome
L4
Nerve - erection and sensation of penil and anal zones
S2, S3, S4
Diaphragm and gallbladder refer pain to the ___ via the ___ nerves.
Right shoulder; phrenic (C3-C5)
Trace sound waves through the ear to the brain stem.
- Outer ear (pinna, auditory canal, eardrum) transfers sound waves via vibration of the eardrum
- Air-filled space of the middle ear contains three bones (ossicles); these conduct and amplify sound from the eardrum to the inner ear
- The inner ear (snail-shaped, fluid-filled cochlea) contains the basilar membrane that vibrates secondary to sound waves. The vibration is transduced via specialized hair cells -> auditory nerve signaling -> brain stem.
Where do low and high frequencies localize to on the basilar membrane (tonotopy)?
Low frequency - apex near helicotrema (wide and flexible)
High frequency - base of cochlea (thin and rigid)
Explain how to diagnose conductive vs. sensorineural hearing loss.
Conductive - abnormal Rinne test, Weber test localizes to affected ear
Sensorineural - normal Rinne test (air > bone), localizes to unaffected ear
Describe the path of aqueous humor through the eye.
- Produced by non-pigmented epithelium on the ciliary body, secreted into posterior eye chamber
- Travels through the pupil to the iridocorneal angle
3a. Uveoscleral outflow (10%) - drainage into uvea and sclera
3b. Trabecular outflow (90%) - drainage through the trabecular network -> canal of Schlemm -> episcleral vasculature
Define miosis.
Pupillary constriction
How is miosis controlled?
Parasympathetics
1st neuron: Edinger-Westphal nucleus to ciliary ganglion via CN III
2nd neuron: short ciliary nerve to sphincter pupillae muscles
Explain the pupillary light reflex.
Light in either retina sends a signal via CN II to the pretectal nuclei in the midbrain that activates bilateral Edinger-Westphal nuclei. The pupils contract bilaterally (consensual reflex)
Define mydriasis.
Dilation
How is mydriasis controlled?
Sympathetic nervous system
1st neuron: hypothalamus to ciliospinal center of Budge (C8-T2)
2nd neuron: exit at T1 to superior cervical ganglion (travels along cervical sympathetic chain near lung apex, subclavian vessels)
3rd neuron: plexus along internal carotid, through cavernous sinus; enters orbit as long ciliary nerve to pupillary dilator muscles. Sympathetic fibers also innervate smooth muscle of eyelids and sweat glands of forehead and face
What is the cavernous sinus?
Collection of venous sinuses on either side of pituitary; blood from eye and superficial cortex -> cavernous sinus -> internal jugular vein
What cranial nerves pass through the cavernous sinus?
III, IV, V1, VI, and occasionally V2 plus postganglionic sympathetic pupillary fibers en route to the orbit
CNS drugs must be ___-soluble or be transported actively across the ___.
Lipid; BBB
Anesthetics with ___ solubility in blood have rapid induction and recovery times.
Decreased
Anesthetics with ___ solubility in lipids have increased potency.
Increased
Minimal alveolar concentration of inhaled asthetic = ?
Minimal alveolar concentration required to prevent 50% of subjects from moving in response to noxious stimulus (eg, skin incision); inversely related to potency
Discuss the solubility of nitrous oxide (N2O).
Decreased blood and lipid solubility -> fast induction and low potency
Discuss the solubility of halothane.
Increased blood and lipid solubility -> slow induction and high potency
What does a high blood/gas partition coefficient indicate?
More soluble in blood -> slower equilibration with brain -> longer onset
Type 1 vs. type 2 muscles - type of twitch, color of fibers
Type 1 - slow twitch, red fibers
Type 2 - fast-twitch, white fibers
Why are type 1 fibers red?
Increased mitochondria and myoglobin concentration (for increased oxidative phosphorylation -> sustained contraction)
The proportion of type ___ muscle increases after endurance training. The proportion of ___ type muscle increases after weight/resistance training and sprinting.
Type 1; type 2
Review smooth muscle contraction.
Page 434
What is endochondral ossification?
Formation of bones of axial skeleton, appendicular skeleton, and base of skull; the cartilaginous model of bone is first made by chondrocytes. Osteoclasts and osteoblasts later replace with woven bone and then remodel to lamellar bone.
What is membranous ossificaiton?
Formation of bones of calvarium, facial bones, clavicle; woven bone formed directly without cartilage, later remodeled to lamellar bone
What are osteoblasts?
Build bone by secreting collagen and catalyzing mineralization in alkaline environment via ALP; differentiates from mesenchymal stem cells in the periosteum and bone marrow.
How is osteoblastic activity measured?
Bone ALP, osteocalcin, propeptides of type I procollagen
What are osteoclasts?
Dissolve bone by secreting H+ and collagenases; differentiates from a fusion of monocyte/macrophage lineage precursors
How can osteoblasts and clasts be differentiated by appearance?
Blasts - single nucleus
Clasts - multinucleated
How does PTH affect bone?
At low, intermittent levels, it exerts anabolic (building) effects on osteoblasts and osteoclasts (indirect). Chronically increased PTH (primary hyperparathyroidism) causes catabolic effects -. osteitis fibrosa cystica
How does estrogen affect bone?
Inhibits apoptosis in bone-forming osteoblasts and induces apoptosis in bone-resorbing osteoclasts; causes closure of epiphyseal plate during puberty. Deficiency leads to increased cycles of remodeling and bone resorption and an increased risk of osteoporosis
