Supraspinal Motor Neurons

Front 1

lower motor neurons are _______ to the mm they innervate

Back 1

ipsilateral

Front 2

lower motor neurons are _______ and _______ motor neurons in spinal chrd

Back 2

alpha and gamma

Front 3

What does alpha motor neuron look like

Back 3

very large, long, heavy branches, multipolar

Front 4

motor nerves

Back 4

stimulate activity in other cells. In corticospinal tract we are talking only about skeletal mm.

Front 5

alpha motor neurons

Back 5

nn in spinal cord, axons are found in peripheral nn. Synapse and cause contraction of skeletal mm

Front 6

gamma motor nn

Back 6

axons stimulate small mm, called 'intrafusa' mm, inside mm spindles.

Front 7

muscle spindles

Back 7

measure stretch of mm therby giving information about proprioception to brain.

Front 8

Lower motor neurons
Definition

Back 8

cause skeletal mm to contract e.g. ALPHA MOTOR

Counterparts in brainstem will be discussed separately.

Front 9

Organization of alpha motor neurons in spinal cord

Back 9

Founed in Rexed lamina IX.

Can be for single mm w/in one spinal level or more commonly among several.

Proximal and extensor mm are more medial in cord.
Distal and flexor mm are more lateral in position.

Front 10

Spinal reflexes often involve _________ and proproception

Back 10

muscle spindles

Front 11

__________________ is caused by damage to or death of alpha motor neuron injury

Back 11

lower motor neuron injury

Front 12

Upper motor Neurons
Definition

Back 12

Nerve cells whse axons directly affect the lower motor nerves causing either exitation or inhibition

Front 13

Orginization of Upper Motor Neurons

Back 13

Tracts that originate in brainstem

These include CORTICOSPINAL TRACT (MOST IMPORTANT), RUBEROSPINAL TRACT, RETICULOSPINAL TRACT, VESTIBULOSPINAL TRACT, AND TECTOSPINAL TRACT

Front 14

Corticospinal Tract
Origin

Back 14

entire precentral gyrus
Motor humunculus
Pyramidal cells in precentral gyrus send out axons to spinal cord (imputs from premotor cortex, basal ganglia and cerebellum will be discussed later)

Front 15

Corticospinal tract: Brain to spinal cord

Back 15

Axons originating rom precentral gyrus pyramidal cells continue down to POSTERIOR LIMB OF INTERNAL CAPSULE to middle third of the BASIS PEDUNCULUS in midbrain to BASILAR PONS to PYRAMIDS OF MEDULLA (hense common name for CST--pyramidal tract).
{LEGS LATERAL , ARMS MEDIAL}
At the DESUCATTION OF THE PYRAMIDS (85%) of motor axons cross over ipsilateral to the mm they innervate to the LATERAL CORTICOSPINAL TRACT. A minority of fibers (15%) remain contralateral and travel in the ANTERIOR CORTICOSPINAL TRACT. They decussate at the point where they need to innervate an alpha motor neuron.

Front 16

Corticospinal tract is more important in _______ and _______ muscles.

Back 16

flexor and fine movement

Front 17

Postural muscles are innervated by _________ systems

Back 17

extrapyramidal

Front 18

Reticulospinal pathway
origin? contralateral, ipsilateral, bilateral?
Function?

Back 18

From reticular formation of pons and medulla (central nuclei. Axons predominantly bilateral, may elicit delayed movement in proximal and/ or prexial limbs. -- helps in balance if someone pushes you from behind.

Front 19

Vestibulospinal Pathwas

Back 19

from lateral vestibular nucleus
Arise and descend ipsilaterally to affect postural mm, particularly deep back mmm but some proximal limb extensors.

Front 20

Ruberospinal pathway

Back 20

Input from cerebellum and cerebral cortex. With some fibers to cerebellum and inferior olivary nucleus, project contralaterally to spinal cord controlling upper limb

Front 21

Tectospinal tract

Back 21

arising superior colliculus
end in cervical region
fx in coordination of eye, neck mvmt

Front 22

UMN injury

Back 22

loss of consious motor control
leaves reflex intact
Initial shock will create FLACID PARALYSIS then SPASTIC PARALYSIS (exaggerated reflex activity present)
SIGNS:
Babinsky sign
Spacicity
Paresis