Spinal Cord 3 Flashcards
Dorsal column-medial lemniscal system
Discriminative touch, proprioception, vibration sense
Corticospinal tract
Part of the pyramidal system,
Volitional motor
Anterolateral system
Pain, temperature, crude touch
Spinoreticular, spinothalamic, spinomesencephalic, and other tracts.
Spinocrebellar tract
Unconscious proprioception, information from muscle (spindles and Golgi tendon organs), to the cerebellum
Hypothalamospinal tract
Central control of pre ganglionic autonomic neurons of the spinl cord
Pyramidal system
Major Volitional motor control
Neurons originate in the cerebral cortex, primary motor complexioned frontal lobe
Sends projections to the brain stem(corticobulbar) and spinal cord (corticospinal)
Upper motor neurons
Cortical neurons of the pyramidal tract
Have origin and termination in the CNS
Lower motor neurons
Spinal crd and braistem neurons that directly Innervate muscles are lower motor neurons
Originate in CNS and terminate in the periphery
Lateral corticospinal tract
80-90 % of fibers cross at the pyramidal decussation
Anterior corticospinal tract
Descends ipsilaterlly as they do not decussate, Innervate motor neurons and interneurons that primarily are axial muscles, some fibers cross at level of Innervation of inter or motor neurons
Lesions do not oresnt significant clinical problems
CS tract Innervation
CS axons Innervate some alpha neurons directly but the majority Innervate interneurons that supply alpha neurons, can be excitatory or inhibitory, generally CS neurons activate flex or sand inhibit extensors
This is to control fine skilled movements
Other descending tracts that contribute to normal motor fnxn
Reticule spinal, rubrospinal, and vestibulospinal
Rubrospinal tract
Other significant flexor biased tract, crosses near its origin in the red nucleus of the midbrain
Involved in flexor movements of arm and firearm doesn’t descend past cspine.
Has some inhibition of extensors
Vestibulospinal and reticulospinal tracts
Extensor biased
Fnxn in proximal body muscle tone,and postural muscle activity related to balance
Vestibulospinal tract
Vestibular tracts have to main branches that participate in extensor activation and balance special orientation.
Does not receive input from the cerebrum, but from the cerebellum.
The cerebellum maintains posture through sensory input from the soinocerebellar tracts, that convey partly to the vestibulospinal tract to maintain posture.
Preganglionic autonomic neurons
Primarily through the Hypothalamospinal tract, neurons of the Intermediolateral cell column
Constitute upper motor neuron influences of viscera motor activity.
Ascending tracts
Primarily dorsal columns, ALS, ans spinocerebellar tracts
Dorsal columns
Carry fast conducting myelinated axons, t types Ia, Ib, II, A beta, enter the spinal cgord in medial division of the dorsal root entry zone
Carrie info ipsilaterally in the spinal cord in posterior fasiculi, gracilis, and cuneatus.
Fasciculus gracilis
Consists of Axons of DRG neurons below t6
Fasciculus cuneatus
Consists of axons of DRG neurons above t6
Somatotopic arrangement of DC
Information from the legs and feet are found medially while info from the arms and trunk and neck are found laterally.
Medial lemniscus
Formed from axons coming from the nucleus gracilis and cuneatus.
Axons that form medial lemniscus cross at the level of the obex. They continue up to the thalamus, thalamic neurons then continue to sensory areas of the cerebral cortex.
ALS
Collection of tracts carrying pain temperature and crude touch sensory information, contains lightly and unmyelinated axons, type 111, IV, A-delta and C
Enter SC at lat. div. of dorsal root entry zone.
Tracts run Mostly in lat and partly I he ant funiculi
Dorsal root entry zone
Where ALS sensory nerves enter to synapse in the lateral horn of the SC. They then cross over through the ant white commissure to form ALS on the opposite side of entry, these axons also give off collateral nerves
Spinothalamic tracts
Direct connection to thalamus of ALS neurons is the first major connection of spinothalamic tract which provides connection then to the somatosensory cortex.
Spineoreticular fibers
Indirect rout to thalamus through reticular formations, these form poly synaptic pathway that will eventually reach wide areas of cerebral cortex.
ALS resistance to localized lesions
Is occurs as a result of the collateral branches that the ascending ALS tracts give off along the way..
Spinocerebellar tracts
Anterior, posterior, and cuneocerebellar tract, A and P carry info from the spindles, joint capsule receptors and skin of the lower limb while C carry this info from the upper limb
Fibers pass through dorsal root gang to cell nuclei in intermediate zone of the sp. gray matter. P and C carry info ipsilaterally and deal primarily with individual muscle coordination while A ascends contra. And deals with entire lower limb muscles coordination in the cerebellum.
