Direct Sensory-Motor connection

• Stimulation of sensory nerve ending
•  Afferent signal travels through dorsal root into dorsal horn
• Synapses on motor nerve
• Efferent signal travels through ventral root out to muscle
• Reciprocal inhibition

Motor Tracts:

Extrapyramidal Tracts

General info.

Connections/networds in brainstem and cerebellum

Indirect pathway

Functions:

1. Smooth, coordinated movement
2. Upright, balanced posture

Regulate coordinated movement and muscle tone

• Reticular formation

Neck and body twisting

• Superior colliculus

Regulate muscle tone; support body against gravity

• Red nucleus

Reflexive adjustments of head/body

• Vestibular input to LMNs

Indirect connection to muscles

Multiple synapses in basal ganglia and/or cerebellum

Coordinate and refine movement

Regulate motor functions, muscle tone, action execution and cognition

1. Caudate nucleus
2. putamen
3. globus pallidus
1. internal
2. external
4. substantia nigra
5. subthalamic nucleus

1. Caudate nucleus
2. Putamen

1. Putamen
2. Globus Pallidus

• NO initiation of movment
• suppress competing movements
• Facilitate associated automatic movements

1. Does the basal ganglia contain UMNs?

2. Does the basal ganglia contain LMNs?

3. Where is input received from?

1. NO
2. NO
3. motor cortex (BA 4 and 6)

Basal Ganglia:Direct Circuit

Function

Basal Ganglia: Direct Circuit

Sequence

1. Cortex: excites Caudate
2. Caudate inhibits GP (globus pallidus)
3. GP does not inhibit Thalamus
4. Thalamus excites cortex

Basal Ganglia: Indirect Circuit

Function

Basal Ganglia: Indirect Circuit

Sequence

1. Cortex excites caudate
2. Caudate inhibits GP
3. GP fails to inhibit StN (Subthalamic nucleus)
4. StN excites GP
5. GP inhibits thalamus
6. Thalamus cannot excitte cortex

Cerebellum

Function pertaining to movement

• Ongoing modifications of movement
• Error control
• Rapid movments (AMR/SMR)
• Motor learning
• NO initiation of movement

Cerebellum:

How does it modify movement?

• Monitors cortical motor output
• Compares sensory input with motor output
• Discrepencies
• Ascending feedback (modify movement)
• Descending feedback (alter muscle tone/reflexes)
• Rubrospinal/reticulospinal tracts to LMNs

Cerebellum:

What does it monitor?

• Body position
• muscle preparedness
• muscle tone
• equilibrium
• distance and duration of movements

• Enters through middle/inferior cerebellar peduncles
• some in superior

• Enters through superior cerebellar peduncle

• Purkinje cells
• Mossy Fibers
• Climbing fibers

• Extensive dendritic branches
• Inhibitory effect on cerebellar nuclei
• Nuclei also receive excitatory afferent input
• Connected via parallel fibers

• Red nucleus
• Cranial nerve nuclei
• Reticular formation

Reticular formation

Function

• Aids in muscle tone
• Intrinsically excited (no external stimulation needed)
• Controlled by descending inhibition from basal ganglia and motor cortex
• Decerebrate rigidity
• Loss of inhibition from upper levels -> extensor postureing

UMN Lesions:

Types

1. Unilateral: UMN syndrome
2. Bilateral: Pseudobulbar palsy

UMN Lesions:

Unilateral

• UMN Syndrome
• Contralateral symptoms
• Spasticity (minimal)
• Mild spastic dysarthria (resolves quickly)
• Loss of discrete muscle control
• muscle weakness
• brisk reflexes

• Pseudobulbar palsy
• Pseudo = not due to brianstem injury, but input to brainstem
• Symptoms
• Hypertonia
• Loss of discrete motor control
• reduced motor control of head/neck
• little to no volitional facial expression
• spastic dysarthria
• inappropriate laughter/crying

• Ipsilateral to damage
• Flaccid paralysis (low muscle tone)
• Reduced reflexes
• Muscle fibrillation and atrophy

1. Complete transection
2. Spinal Hemisection (Brown-Sequard syndrome)

• Brown-Sequard Syndrome
• Damage to 1 side of spinal cord (left or right)
• Ipsilateral paralysis
• Ipsilateral loss of touch sensation
• Contralateral loss of pain and temperature

• Parkinson's Disease
• Huntington's Chorea

Basal Ganglia Damage:

Parkinson's Disease

• Loss of DA from substantia nigra
• Symptoms
• Resting tremor
• dysarthria
• masked face
• festinating gait

Basal Ganglia damage:

Huntington's Chorea

• Damage to caudate nucleus
• Symptoms
• Writhing movements
• Dysarthria

• Ipsilateral effects
• Motor function affected
• Motor coordination; no paralysis
• Sensory function is OK
• Gradual recovery
• except with large lesions or degerative conditions

1. Ataxia
2. Dysdiadochokinesis
3. Dysmetria
4. Ataxic Dysarthria
5. Intention tremor
6. Hypotonia
7. Rebounding
8. Disequilibrium

• Misjudgement of range of motion
• overshoot
• undershoot

• Bilateral pontine damage
• Quadriplegia
• Loss of all motor speech functions
• Vertical eye movement preserved (CN III)

Patient awake; sensation OK, audition and comprehension OK

• Lou Gherig's Disease
• ALS
• Degeneration of motor neurons (LMN and UMN)

• Presence of BOTH UMN and LMN signs
• Spasticity, hyperreflexia, slowed movements
• Flaccidity, atrophy, weakness

1. Insula
2. Tail of caudate nucleus
3. Hippocampus
4. Subthalamic nucleus
5. Internal capsule
6. Thalamus
7. Third Ventricle
8. Substantia nigra

1. Putamen
2. Globus Pallidus - Lateral
3. Globus Pallidus - Medial
4. Amygdala
5. Substantia Nigra
6. Subthalamic Nucleus
7. Thalamus
8. Caudate Nucleus

1. Caudate Nucleus
2. Putamen
3. Striatum
4. Globus Pallidus
5. Lateral/Medial
6. Subthalamic Nucleus
7. Basal Ganglia
8. Substantia Nigra
9. Thalamus

1. Anterior nucleus
2. Intralaminar nuclei
3. centromedian
4. Reticular (covers thalamus)
5. Internal medullary lamina
1. band of myelinated fibers

• Mediates endocrine/metabolic states
• Epithalamus
• Diurnal/autonomic body functions

• Motor functions