Neuroanatomy and Movement Disorders Overview

Somatosensory cortex

Frontal gyrus of the parietal lobe

Outer/temporal part of retina

Looks at opposite field

Nasal/medial part of retina

Sees the same field

Spinothalamic

Ascending pain and temperature pathway

Retinotectal pathway

Pathway from retina to superior colliculus

Hypothalamus

Brain region involved in thirst and hunger

Thalamus

Substructure of diencephalon

Prostaglandins

Block K+ increase depolarization, reduced by NSAIDs

Corticobulbar

Head and neck movement, doesn't leave spinal cord via pons

Medulla oblongata

Used to get to spinal cord

Direct pathway

Disinhibition of thalamus and activation of motor areas = pro-movement; disruption leads to decreased movement = hypokinetic

Indirect pathway

Disinhibition of subthalamic nucleus (STN) resulting in inhibition of thalamus and motor areas = anti-movement; disruption leads to increased movement = hyperkinetic

Alpha motor neurons

Innervate extrafusal muscle fibers

Gamma motor neurons

Innervate intrafusal muscle fibers

Posterior (dorsal) column

Perception of fine-touch, two-point discrimination, vibration, sense of self-movement and body positioning (proprioception)

Dorsal column

Carries the sensory modalities of proprioception, fine touch and vibration; decussates in brain stem

Spinocerebellar

Nonconscious proprioception; decussates in spinal cord

First-order neuron

Delivers sensations to the CNS; cell body is in the dorsal root ganglion; axon projects to the dorsal horn of spinal cord

Second-order neuron

Neuron with cell body in the spinal cord or brainstem that projects to the thalamus

Third-order neuron

Transmits information from the thalamus to the cerebral cortex

Arachidonic acid

Released during tissue damage and metabolized into prostaglandins and leukotrienes

Leukotrienes

Signal using G proteins to stimulate NMDA receptors - excitatory

Histamine

Released by mast cells during tissue damage; excites nociceptors

Substance P (SP)

Released by injury; excites nociceptors

Potassium (K)

Most tissue damage results in an increase in extracellular K; correlates with pain intensity

Serotonin (5-HT)

Released with tissue damage

Aβ fiber

Fastest; largest; muscle spindles & mechanoreceptors in skin (balance & pressure)

Aδ fiber

Medium speed and size; nociceptors & free nerve endings of touch/pressure & cold thermoreceptors (pain & touch & cold)

C fiber

Slowest; smallest; nociceptors of spinothalamic tract & warmth thermoreceptors (pain & warmth)

Chorea

Very repetitive movements; brief/episodic

Bradykinesia

Slowing or slowness of movements; difficulty initiating movements; loss of facial expressions

Huntington's disease

Irregular jerking movements; slowed saccadic eye movements; lack of impulse control

Parkinson's disease

Progressive bradykinesia; rigidity; resting tremor

Tardive Dyskinesia

Repetitive involuntary movements of the face; often caused by chronic use of certain psychiatric drugs (e.g. dopamine blockers)

Ataxia

Altered balance, speech, or limb movements; affected brain regions responsible for movement coordination

Dystonia

Sustained involuntary movements; rigidity and muscle contracture; whole body or isolated to limb/area

Tremor

Rhythmic shaking of body parts - typically limbs/extremities