Lezione3_Fisiatri

8/8/2019 Lezione3_Fisiatri

1/31

Il controllo nervoso

delle unit motorie

Marsilio SaccaviniUOC Degenza di Medicina

RiabilitativaTREVISO


2/31

The hierarchical structure of

central motor systems


3/31

Descending pathways frommotor cortex and brainstem


4/31

Final common pathway

The -motoneurone is the final point of

summation for all descending and reflex

input: the final common pathway(Sherrington 1857-1952)


5/31

Motor cortex of right hemisphere


6/31

The motor cortex Premotor cortex (PMC): in humans 6 times larger than

primary motor cortex (MI), in monkeys 1:1Involved in preparation of movement, postural contol,

visual guidance and rapid correction of movements

following sensory input

Supplementary motor area (SMA): medial to PMC, receivesafferent input from basal ganglia. Important for initiation of

voluntary movement.

The PMC and SMA, plus other association areas of cortex, are

responsible for motor programming.

Primary motor cortex (MI):synthesises input from other parts

of the CNS and generates and transmits the central command

to the brainstem and spinal cord neurons to initiate and

modulatemovement


7/31


8/31

The cerebellum A neural network containg ~50% of all the

neurones in brain

Involved in learning and execution of all motor

programmes

Receives two excitatory inputs: themossy fibresand theclimbing fibres.

Both fibres have a direct excitatory input on the

deep cerebellar nuclei and an indirect inhibitory

input via stimulation of the Purkinje cells. They

are able to modulate output of the motor centre

according to sensory input


9/31

Cerebellar pathways


10/31

Adaptive control system of

cerebellumThe cerebellar cortex is the site where the

main adaptive control of the motor system

resides. This function is achieved bycomparison of information about the intended

motor plan and the actual performance of the

movement. (through the integration of information fromthe mossy fibres and the climbing fibres).


11/31

Cerebellar network


12/31

The basal ganglia

5 basal ganglia nuclei: caudatum,

putamen, globus pallidus, nucleussubtalamicus and substantianigra.

The caudatum and putamen receive

information from almost all cortical

areas. Both nuclei are involved in a

motor loop and a cognitive loop.

The basal ganglia are involved in the

release of motor programmes for

goal-directed movements following

external and internal stimuli. Theyselect these stimuli and initiate the

preparation and execution

movements by sending commands to

the PMC and brainstem

Cau

d.


13/31

The spinal cord

Together with the brainstem, is the site

where all motoneurones are located

Main function: integration of descendingcommands with peripheral inputs.

Processing and transmission of afferent

information to higher motor centres

Interneurones in SC are capable of

modulating the output of motoneurones and

gain of spinal reflexes


14/31

Integration of information in SC


15/31

Reflex pathways

18/18


16/31

Motor Units


17/31

The motor unit


18/31

Main features of a motor unit


19/31

Number of musclefibres/motor unit


20/31

Contraction time of different

motor units


21/31

Effect of frequency of firing on

muscle force

1 Hz

50 Hz


22/31

Contraction properties of the three

types of motor units (FF, FR, S)


23/31

Fibre type classification


24/31

Recruitment of motor units:Hennemans size principle


25/31

MUs recruitment indifferent motor activities

Hi h th h ld MU


26/31

High-threshold MUs aredifficult to recruit


27/31

The evaluation of

muscle activation


28/31

Deviations from Hennemans

size principle Paw shaking

Stimulation of cutaneous nerves

Preparatory movements

Ballistic contractions (? c.f. Grimby & Hannerz, J Physiol

264, 1977)

Eccentric contractions


29/31

Paw shaking (cats)

High-treshold M.U.s can be activated

without firing of small low-threshold units


30/31

Cutaneous nerves stimulation

THRESHOLD OF ACTIVATION OF M.U. CHANGES

DURING CUTANEOUS STIMULATION

Slow M.U.s are recruited at higher forcesduring cutaneous nerve stimulation

Fast M.U.s are recruited at lower forces

during cutaneous nerve stimulation (Garnett &

Stephens J Physiol 311, 1981)


31/31

Preparatory movements

High treshold motor units are recruited

before the expected movement (Nardone et al. J

Physiol 409, 1989)

Lezione3_Fisiatri

Documents

Transcript of Lezione3_Fisiatri