1. Spinal cord, reflex, voluntary movement
Several useful schemes mostly from a textbook
Essential Medical Physiology, ed. L.R. Johnson, Elsevier, 2003.
Dr. Valoušková

2. Function of spinal cord
Basic reflexis (monosynaptic, polysynaptic, nociceptive, extensor/flexor, crossed extensor refl.)
Communication between CNS and periphery (motor tracts – vestibulospinal ( inhib N-ns to neck, back), tectospinal from colliculus sup. – visual and auditory orientation – eye movement
these tracts cooperate - orientation response
pontine ret/spin tr. – ipsilat – innervation of gamma and alpha motoN-ons (limbs) - increase muscle tone
medullary reticulospinal – balance the excitatory drive from pontine reticulospinal tr. (inhib. motoN-ons, decrease axial and extensor muscle tone)
Integration control between spinal segments

3. Pyramidal (extrapyramidal) tract
½ cells within primary motor c-x
Fibers leave the main bundle at all levels of brainstem and SC
conscious control over cranial n-v motor nucl. and motor segments of the SC
Role - to initiate voluntary movement
Cerebellum, basal ganglia (before extrapyramidal tr.) – now part of the corticospinal and pyramidal tract / direct-indirect input to spin motoN-ns, through projections involving motor c-x

4. Driving forces to lower motor neurons

5. Organization of muscle spindle and Golgi tendon organ
speed of contraction and stretch
tension of contraction and passive relaxation

6. Innervation of muscle spindle Gamma system
– allows spindle to maintain high sensitivity during contraction and relaxation
Motor centers
tension
strech sensitive channels
Gamma activation -> contraction of intrafusal fibers -> increased tension on the rings => higher sensitivity to changes in length caused by contraction or stretching of extrafusal muscle fibers

7. Golgi tendon organ - GTO
Function – to signal amount of tension generated by muscle tissue (muscle and its insertion)
Muscle contraction –> stretch capsula of GTO –> Ib afferents
–> interN-on –> inhibition of a-motoneuron –> relaxation

8. Extensor patellar reflex
Activation of muscle spindle =>
activation of sensory neuron =>
1) activation of extensor motor neuron (contraction of extensor)
2) simultaneous activation of interneuron => inhibition of activity of flexor motor neuron (relaxation of flexor)
reflex arch + -

9. Polysynaptic flexor reflex (pain)
Parallel aktivaion of flexor and inhibition of extensor + -

10. Flexor and crossed extensor reflexes
Afferent (sensory) axons send collaterals also into contralateral motor nucleus of spinal cord + -
Coordination of 4 limb movement - analogous – principle - ipsi- and contralateral excitation and inhibition of flexors and extensors (ipsi- and contralateral connections between spinal segments, e.g. a walk)

11. Voluntary control / c-x

12. Basal ganglia

13. BG- connections + + -

14. Organization of voluntary movement – basal ganglia
Direct path
Indirect path
Organization of voluntary movement – basal ganglia
Overall role of BG – inhibitory control of the feedback connection thalamus – motor area
Direct path – excitatory - increases thalamic activity
Indirect path – inhibitory – decreases thalamic activity
DA – dopamine (different receptors in neostriatum)
Inhibitory path
Excitatory path

15. Parkinson`s disease Huntington`s disease
Slow movement, tremor
Huntington`s
disease
quick jerky movements
Reduced inhibition of thalamic activity => increased stimulation of motor area
Amplified inhibition of thalamic activity => lower stimulation of motor area