Upper Motor Neurons

What are the two components of UMN?

Pyradmidal: learned movements (cortex involved)

Extrapyramidal: posture and locomotion

Which is more important extrapyramidal or pyramidal in domestic animals?

Extrapyramidal

Where are the extrapyramidal UMN nuceli located?

brainstem

Where can UMN synapse?

• Directly on a LMN (pyramidal)

• onto an interneuron which synapse onto a LMN (extrapyramidal)

True or False: Interneurons are EITHER inhibitory or excitatory.

TRUE

Where does the cortex control motor activity?

Contralateral side

Where des the brainstem control motor activity?

Ipsilateral side

What are motor systems?

descending spinal tracts

Lateral Funiculus

descending motor tracts that facilitate flexor muscle activity and inhibit extensor muscle activity

Ventral Funiculus

descing motor tracts facilitating extensor muscle activity and inhibit flexor muscles

Posture requires ____ tone

extensor

What is the main motor tract for voluntary movement in dogs?

Rubrospinal Tract

What does the rubrospinal tract facilitatee?

flexor muscles on contralateral side

Ascending Reticular Activating System

sends sensory messages from the reticular formation to cortex and vice versa

• regulates consciousness, RR, chewing, etc

Ddescending Reticular System

transmits signal to and frpm motor neurons of the spinal cord via the reticulospinal tracts

• coordinate movement, modulate tone and balance

Medullary Reticulospinal Tract

feature of DRAS that facilitates flexor muscles

PONTINE rETICULOSPINAL tRACT

• part of the DRAS that facilitates extendor muscles

In the extrapyramidal Motor System, which parts facilitate extensor activity? What inhibits them?

• Pontine Reticulospinal Tract

• Vestibulospinal Tract

• Inhibited by cerbral input

• Travel in ventral funiculus

In the extrapyramidal motor system, which ones faciliatte felxor activity?

• Rubrospinal Tract (contralateral)

• Mediuallary Reticulospinal Tract (Ipslateral)

• Travel via lateral funiculus

• Facilitated by cerebral input

What is the path all pyramidal tracts tske out of the cortex?

corona radiata, internal capsule, crus cerebri

Corticopontine Tract function

communicates with opposite cerebellum to allow for coordination of planned motor functions

Corticonuclear Tract Pathway

mediates voluntary eye movements, mastication, facial expression, swallowing, neck and tongue movement

Corticospinal Tract Function

major pathway providing voluntrary motor function in primate species

Which species dont have a pyramidal system?

birds, reptiles, amphbians, and fish

decerebrate rigidity

lesion in midbrain between rostral and caudal colliculus that causes ONLY exensor tone and can affect consciousness/awareness

Postural Phase

activation of antigravity extensor muscles and inhibition of flexor muscles

Protraction Phase

initation requires activation of flexor muscles and inhibition of extensor muscles

Central Pattern Generators

network of interconnected interneurons in the spinal cord grey matter that modulates motor neuron activity for generation of gait

What is the difference between stepping and walking?

Stepping: movement CPG creates that can be inducde wthout brainstem involvement

Walking: purposeful movements that require brainstem input

Schiff Sherington Posture

special interneuron network which transmit inhibitory signals FORWARD which causes increased tone in the forelimbs when not moving

Clinical Signs of Lesions in the Forebrain

• circling towards the lesion

• seizures

• head pressing

• behavior change