Neurology Exam 2

• Free Nerve Endings
• Encapsulated Nerve Endings
• Separate specialized cells

• Bare dendrites
• Pain, Thermal, Tickle, itch and light touch (non-localizable)

• Dendrites encased in connective tissue capsule
• Pressure, vibration and deep touch
• ex. pacinian corpuscles, meissner"s corpuscles

• Hair cells
• Gustatory cells
• Photoreceptors

• Muscle stretch (measure muscle length)
• Velocity

• Tendon tension
• ex. Knee jerk reflex

Respond to mechanical deformation of the capsule and ligaments

• largest
• fastest
• primary muscle spindles, golgi tendon organs

• 2nd largest, 2nd fastest
• Secondary muscle spindles, skin mechanoreceptors

• 2nd smallest, 2nd slowest
• skin mechanoreceptors, thermal, nociceptors

• smallest
• slowest
• skin mechanoreceptors, thermal, nociceptors

• Largest
• Fastest
• Extrafusal skeletal muscle fibers

Intrafusal muscle fibers

• 2nd smallest
• 2nd slowest
• Pre-ganglionic autonomic fibers

• Smallest
• Slowest
• Postganglionic autonomic fibers

• Conscious Relay Pathways
• Divergent Pathways
• Unconscious Relay Pathways

• Info about location and type of stimulation (modality) to cerebral cortex
• "that's hot" "that hurts"
• Discriminative

• Discriminative touch and conscious proprioception --> DC/ML --> Primary sensory area cerebral cortex
• Discriminative pain and temp --> ST or ALS --> Primary sensory area cerebral cortex

• Conscious (cerebral cortex) and unconscious (Brain stem and cerebellum) levels
• Achy pain

• Slow, achy pain -->Spinomesencephalic -->Midbrain
• '' -->Spinoreticular --> Reticular formation
• '' --> Spinolimbic --> amygdala, basal ganglia, many areas of cerebral cortex

• Unconscious proprioceptive and other movement-related info to cerebellum
• Walking - don't have to think about it

• Movement-related info -->Spinocerebellar -->Cerebellum
• '' -->Cuneocerebellar --> Cerebellum

• Touch and Proprioception = DC/ML
• Pain and Temp = Spinothalamic or ALS

• Rapidly conducting
• Large diameter
• Myelinated
• Discriminative touch - locialization and 2-point test
• Conscious proprioception

• ability to use touch and proprioceptive info to identify an object
• ex. identifying a key in your hand without looking at it

• Recognizes objects by touch
• Controls find movements
• Smooth movements

Muscle spindles Ia and Ib, Golgi Tendon Organs, Pacinian Corpuscles, Merkel's Cells, and Meissner's Corpuscles

Dorsal Root Ganglion --> Fasciculus gracilis (legs) or Fasciculus cuneatus (arms) --> Nucleus gracilis (leg) or Nucleus cuneatus (arm)

Nucleus gracilis/Nucleus cuneatus --> medial lemniscus (leg lateral and arm medial) -->synapse in Thalamus VPL

Thalamus (VPL) -->internal capsule --> Sensory Cortex

Trigeminal ganglion -->Main sensory nucleus in pons

Main sensory nucleus in pons --> Trigeminal Lemniscus --> Thalamus VPM

Thalamus VPM --> Internal capsule --> Sensory cortex

• Lesion to DC/ML
• inability to recognize common objects by touch

• Loss of 2-point discrimination
• Loss of vibratory sense
• Positive Rhomberg Sign

• slow-conducting
• more-diffusely located than DC/ML
• Nociception and temp

• Temperature: hot in A-delta fibers/ cold in A-delta and C fibers
• non-localizable course touch

• Spinothalamic
• sharp pain activate A- delta fibers

• burning pain, slow onset but persistent
• Activate C fibers

Dorsal Root Ganglion --> Dorsolateral tract --> Dorsal horn

Dorsal horn --> Ant. white commissure --> thalamus VPL

Thalamus VPL --> Primary and secondary sensory cortex

Trigeminal ganglion --> Descending tract of trigeminal --> spinal nucleus

Spinal nucleus --> cross in medulla --> Thalamus VPM

Thalamus VPM --> Primary and Secondary sensory cortex

• Nociceptive info to sup. colliculus and PAG
• turn eyes and head toward stimulus

• arousal, attention, sleep/wake cycles
• alert when pain is present

slow pain to thalamus carried by C fibers

• Corticospinal and corticobulbar
• Upper Motor Neurons: Cerebral Cortex --> spinal cord
• Lower Motor Neurons: Cerebral Cortex --> Muscles

• Rubrospinal and vestibulospinal tracts
• Synapses in Brain stem, basal ganglia, thalamus, reticular formation, and cerebellum

Decision --> Motor Planning areas --> Control circuits (cerebellum and basal ganglion) --> Descending motor tracts (pre-central gyrus) --> Lower Motor Neurons (to skeletal muscles)

• Primary Cortex (area 4) in Precentral gyrus
• Right brain controls Left body
• Performance of Muscle movements
• Upper Motor Neurons - Corticospinal tract
• More cortical area needed if more motor neurons
• Ex. vocal cords, tongue, lips, fingers, thumb

• Premotor Area - trunk and girdle muscles; anticipatory postural adjustments
• Supplementary motor area - Initiation of movement; Orientation planning; sequential movements (playing piano)
• Broca's Area (area 44/45) - Programming of speech; Left side
• Right side (like Broca's) - Planning nonverbals; Emotional gestures, tone of voice

• Indirectly innervate skeletal muscle with ACh
• Peripheral and Cranial Nerves
• spinal cord (ventral horn) or brainstem --> skeletal muscles

• Gamma motor neuron - medium sized, myelinated
• Alpha motor neuron - Large, Fast, myelinated

• Flaccid paralysis - Loss of strength and tone
• Areflexia or hyporeflexia - loss of reflexes
• Atrophy
• Denervation hypersensitivity - Fasciulations

Involuntary contractions of muscles reacting to a small amount of ACh because nerves are damaged

• Cerebral cortex or brain stem --> descending tracts --> LMN or interneurons of spinal cord
• Always stay in CNS

• Spastic paralysis - resists passive movements
• Loss of distal extremity strength
• Babinski sign
• Hypertonia
• Hyperreflexia
• Clasp-knife phenomenon

• control posture and proximal movements
• M. coricospinal tract
• M. reticulospinal tract
• M. and L. vesibulospinal tract
• Tectospinal tract

• direct distal limb movements and fine movements
• L. corticospinal tract
• rubrospinal tract
• L. reticulospinal tract

• ability to activate individual muscles (finger)
• Cortex --> post. limb of int. capsule --> cerebral peduncles, ant. pons, pyramids --> cross in pyramids --> LMNs in ventral horns
• cranial nerves will synapse at specific motor nucleus

• controls posture and proximal movments
• don't cross in medulla

• reflexively turns head toward sound or visual stimulus
• superior colliculus of midbrain --> cervial spinal cord

• ipsilateral postural muscles and limb extensors
• Pontine reticular formation --> spinal cord

• Info about head movement and position from vestibular apparatus
• Medial vestibular nucleus --> cervical and thoracic levels to LMNs to back muscles

• gravity info for vestibular apparatus
• ipsilateral extensors and inhibit flexors (keeps us upright)
• Lateral vestibular nucleus --> spinal cord

• Activates flexors and inhibits extensors
• Lateral reticular formation --> spinal cord

• upper limb flexion
• Red nucleus --> cervical and thoracic spinal cord

• located in pons --> dorsal horn of spinal cord
• receive info from PAG
• Reduce pain

• Located in pons
• Produces NE in CNS
• Low NE - sleep
• High NE - stress
• if damaged, behavior or aggression problems