• CNS: motor cortices, basal ganglia, and cerebellum
• PNS: cranial nerves, spinal nerves for respiration

• precentral gyrus
• mostly contralateral
• some bilateral innervation (upper part of face, larynx→back up system)
• homunculus→proportional to level of control, topographically flipped
• received info from Broca, premotor, supplemental, basal ganglia before executing

• receive info from broca's area and association of parietal lobe
• pull info about movement memory
• pass info to pmc and brin stem and spinal cord
• bilateral activation (L & R sharing info, back up)
• initial planning for complex sequences of mvt (more refinement still happening)
• parietal- need sensory info→what environment?
• premotor→postural fixation using environmental cues

• refinement of voluntary motor movement before info transmitted to brain stem and spinal cord
• five components: 1. caudate nucleus, 2. putamen, 3.globus pallidus, 4. subthalamic nuclei, 5. substantia nigra (dopamine production)
• 1 &2 =striatum
• 2&3=lenticular nucleus
• 4&5= communication within
• striatum & lenticular nucleus communicate outside of the basal ganglia

• Regulate muscles tone
• reglate ongoing movements
• inhibits extraneous motor activity (when functioning properly)
• motor learning (implicit-tieing shoes)
• *parkinsons

to striatum from:

• primary motor cortex
• premotor cortex
• supplementary motor area
• thalamus 
• substantia nigra

to globus pallidus from:

• subthalamic nuclei

from striatum to:

• substantia nigra
• globus pallidus

from globus pallidus to

• thalamus (5)
• subthalamic nuclei
• red nucleus
• reticular formation

• Loop 1: cortex→striatum→GP→thalamus→cortex
• Loop 2: striatum→substantia nigra→striatum
• Loop 3:GP→SN→GP
• Loop 4: Thalamus→striatum

• neurophysiological consequence→loss of inhibitory control over motor behaviors
• symptoms:
• dyskinesia→involuntary disordered mvts
• bradykinesia→slow mvt
• hypokinesia→limited mvt
• postural abnormalities→dystonia
• altered muscle tone→typical rigidity

• asthetosis→slow, involuntary writhing mvts
• ballism→violent, forceful flinging mts (jerking)
• chorea→involuntary, rhythmic mvts (head turn)
• tremor→ resting, action, postural (stick arms out straight and hands will shake), intention or terminal

• Parkinsons disease→destruction of dopamine producing cells; some forms are hereditary
• huntington's chorea→degeneration in caudate nucleus, hereditary
• wilson's disease→degeneration in basal ganglia, hereditary

• muscle synergy (muscle groups)→smoothness, coordination 
• muscle tone→helps prepare for next mvt
• range of mvt
• strenght of mvt
• equilibrium (also vestibular system)

• superior cerebellar peduncles→efferent, output to red nucleus, then to thalamus, reticular formation(brainstem)& spinal cord
• middle cerebellar peduncle→afferent, input from brainstem & cortex
• inferior cerebellar peduncle→afferent, input from spinal cord, brainstem & vestibular system

• receives extensive sensory input→but is not involved in sensory discrimination or interpretation
• influences motor function→ but when lesioned does not result in paralysis
• involved in motor learning→by modifyin motor activity based on results of movement

• knows intention and results
• receives from (afferent connections): motor cortex, spinal cord and brainstem
• sends to: (efferent connections): thalamus, brainstem (red nucleus)

• cerebrocerebellum: connections to certex via brainstem & thalamus→for coordination & smooting (synergy); posterior lobe
• spinocerebellum: connections to brainstem & spinal cord→for modifcations in muscle tone; anterior lobe
• vestibulocerebellum: connections to vestibular system→reflexive equilibrium & balance, floccondular lobe

• dyscoordinated muscle activity
• causes: hereditary; autosomal recessive (Friedrich's ataxia-teens); autosomal dominant (spinocerebellar ataxia)
• causes: acquired (tumore, stroke, tbi)
• symptoms: slurred speech (ataxic dysarthria); difficulty walking (feet placed far apart for balance); disruption of motor control (hand/eye coord, writing, eating, swalllowing)-clumsy
• hypotonia

• action (intention)- occurs during movement
• terminal- increases in frequency (gets worse) as limb approaches target
• postural- when limb is held against gravity

• awkward performance of rapid alternating movements (e.g. irregular pa-ta-ka)
• disruption of rhythmic movements (finger tap three times, pause, repeat, pause, etc.)

• impairment judging distance to target in reaching to a stationary or moving target, patient may overshoot (hypermetria) or undershoot (hypometria) the target

• inability of agonist and antagonish muscles to adapt to rapid changes in load
• i.e. patient pushes against doctors hand, hand quickly removed, patient's hand moves beyond point where it would normally stop

• unsteady, lurching gait
• appears drunk
• exaggerated movements of legs (trying to overcompensate)
• tendency to fall 

• upper motor neuron: all the corticospinal and corticobulbar tracts, contained within CNS
• lower motor neuron: motor neurons in the cranial and spinal nerves; second order neurons; final common pathway
• deficits in upper may result in deficits in lower)

• cortex→brainstem (corticobulbar)→PMC→corticobulbar tract→brainstem→cranial nerves→muscles
• cortex→corticospinal (movement of extremeties)

• spastic paralysis (bilateral lesion)
• spastic dysarthria (bilat lesion)
• apraxia (unilat damage)
• hypertonia
• hyperflexia
• clonus (sustained bite)
• babinski sign (under normal conditions goes away at birth→stroke bottom of foot toes go out and up, in adults UMN damage)
• little/no atrophy
• diminished abdominal reflexes

• flaccid paralysis
• hypotonia
• hyporeflexia
• atrophy
• fasciculations (ALS)
• normal abdominal reflexes)

LMN + group of muscle fiber=motor unit

redundancy of innervations

-temporal summations: fast firing

-spatial summation: a lot more motor neuron innervating muscle group

innervation ratios

-limbs: 500 muscle fibers: 1MN gross motor

-larynx: 25: 1MN fine motor

• stretch receptors: spindles, embedded within each muscle (intrafusal fibers)
• tension receptors: golgi tendon organs, within tendons
• changes in bone position- joint receptors, within moveable joints

information is relayed to CNS and alpha motor neuron; feedback, tell you info about positioning in space, adjust

skeletal muscles

• exert force on muscle, tendon or joint
• relax, contract or stretch

• contractile elements
• under direct control of LMN

send/receive info (gamma neurons→proprioreceptors)

alpha & gamma→work together=ability to maintain static position

Intrafusal Fibers(gamma motor neurons)

motor functioning

• muscle spindles
• influenced by cerebellum, basal ganglia and extrapyramidal system

renshaw cells= interneurons

• muscle tone and stretch reflex
• sensory input to spinal cord and brainstem
• static postures
• extrapyramidal system

muscle conditions

• paresis: weakness
• paralysis: complete loss of mvt
• atrophy: deterioration
• fasciculations: rhythmic, bumbly, wobbly mvts
• fibrillations: can't see but are ~to fasciculations seen on EMG

Voluntary Pathway

corticobulbar(corticonuclear), corticospinal

CNS, UMN

involuntary pathway

autonomic nervous system(heart rate, breathing, digestion)

reflex loops

dont really require cortical activity

originates in multiple cortical areas

• primary motor cortex
• primary somatosensory cortex
• premotor area
• supplementary motor area
• parietal association area

pyramidal fibers descend as the corona radiata

converge to pass through the internal capsule (infarct here is devasting)

• 70% of the motor fibers for entire system
• synapse with cranial nerve nuclei in brainstem
• innervates LMN which go on to cocntrol muscles of head and neck
• many originate in lower 1/3 of primary motor cortex (speech)
• majority of innervation is bilateral 
• decussation: anterior surface of medulla

aka cortico-rubrospinal tract

• 30% of the motor fibers
• synapse with interneurons or cell bodies of spinal nerves
• contralateral and unilateral to cortical origin
• 90% decussate at caudal medulla (damage above this level results in contralateral symptoms; ipsilateral if below decussation)
• innervates LMN which go on to control upper and lower trunk and limbs
• after decussation, axons form spinal white matter of the lateral corticospinal tract
• 10% of corticospinal fibers remained ipsilateral and form anterior corticospinal tract (innervates the trunk)

• unilateral, corticospinal→spastic hemiplegia (flexion in limbs, turn head to weak side)
• bilateral corticalbulbar→pseudobulbar palsy→spastic dysarthria (likely to have had multiple strokes; bilateral innervation so unilateral damage may not be so bad)
• unilateral, corticobulbar, lt hemisphere→apraxia

• involved in coordination, modulation and regulation of movement
• extrapyramidal pathways:

• basal ganglia loops
• reticulospinal tract
• rubrospinal tract
• vestibulospinal tract

reticulospinal tract

(reticular activating system=brainstem)

• influences muscle tone
• medial reticulospinal tract→extensor muscles
• lateral reticulospinal tract→flexor muscles

• influences muscle tone
• facilitates activity in extensor muscles
• inhibits activity of flexor muscles

5 senses:

1. visual system
2. olfactory system
3. auditory system
4. gustatory system
5. somasthetic- touch and proprioception

• ears, eyes, touch receptors, olfactory bulbs, taste buds
• transducers→change one form of energy for another (neural)
• respond to specific energy (sorta kinda)

nerves, nuclei, ganglia and tracts

(sensory→everything going to cortex)

first order sensory neurons:

• innervates the sense organ, in PNS, ipsilateral

Second order sensory neurons 

• projection neurons, located in brainstem or spinal cord, point of decussation, to thalamus 

Third order sensory neurons 

• project to cerebral cortex from thalamus, ipsilateral, to primary sensory cortex 

*becomes CNS in between second and third order

primary cortex(recognition)

• primary motor cortex
• primary somatosensory
• primary auditory
• primary visual
• primary olfactory

Association cortex (interpretation→agnosia)

• frontal
• parietal
• temporal
• parieto-occipital

• first order: from the eye→light→retina→rods→and cones convert to chemical response

• second order: optic nerve→half of the retina crosses midline at optic chiasm and half remains ipsilateral
• third order→lateral geniculate body in the thalamus→information is then transmitted to the primary visual cortex (cuneus) and association areas

monocular blindness

tunnel vision(optic chiasm)

homonymous hemianopsia

cortical blindess(cortex)

visual agnosia (association areas)

organ (the ear as transducer)

• external- collects sound
• middle ear- impediance matching, air-fluid interface
• inner ear- cochlea converts fluid vibration to neural

Neural Pathways (VIII Acoustic Nerve)

Cerebral cortex→primary auditory cortex and temporal association cortex

conductive hearing loss (ME)

sensory hearing loss (IE)

Auditory agnosia (cortical)

• tactile system→receptors within the skin→light touch, discriminative touch; pain, cold and heat
• free nerve endings
• hypersensitivity and tactile defensivenss→autism, cp, premature babies
• proprioception and kinesthesia→awareness of limb position and motion of muscles and joints→encapsulated endings, muscle spindles, golgi tendon organ
• phantom limb syndrome

neural pathways

• spinal nerves and cranial nerves (trigeminal, glossopharyngeal)
• cross midline at thalamus
• tracts up to postcentral gyrus of the brain

cerebrum 

• primary somatosensory and association