Motor control Flashcards
Via what motorneurones is voluntary brain control of muscles?
alpha motoneurones in spina cord
What are the 4 systems for controlling movement?
descending control pathways, basal ganglia, cerebellum and local spinal cord/ brain stem circuits
What is the spatial map of musculature in the spinal cord?
medio-laterally
How does the spinal cord receive descending infor?
via the brainstem and direct cortical input via the corticospinal tract
Where does sensory input enter?
at the spinal cord in form of proprioceptors, touch and pain
at the brainstem- the vestibular system informs about balance
at cortical level- movements in reponse to visual, olfactory, auditory, emotional and intellectual cues
How does the stretch reflex work?
tap to inelastic tendon causing force to be transmitted to muscle fibres which stretch, stretch activates the sensory nerves in the muscle spindle, increasing the number of APs in afferent nerves projecting through the dorsal horn into the spinal cord
What are the 3 types of connections that spindle senosry afferents divide and make in a stretch reflex?
1) Directly activate the motoneurones to the stretched muscle causing rapid contraction of the agonist muscle- Monosynaptic
2) Sensory fibres from stretched spindle connect indirectly with antagonsit muscle- reciprocal inhibition
3) spindle afferent info also ascends in the dorsal columns and make connections in the somatosensory cortex to tell brain length of muscles
What is the golgi-tendon organ reflex?
afferent nerves from GTO monitor muscle tension, 1b sensory nerves from GTO fire AP when muscles contracts and shortens.
Causing activation of inhibitory interneurons to the agonist muscle, decreasing contraction strength and activation of excitatory interneurons to antagonist muscles.
This info ascends in dorsal columns to somatosensory cortex
What is the purpose of the GTO reflex?
prevents muscles contracting so hard that the tendon insertion is torn away from the bone.
This reflex is polysynaptic
What is the flexor reflex?
uses info from pain receptors in skin, muscles and joints, they are polysynaptic, they flex the affected body part.
is an ipsilateral flexion in response to pain
What also happens in the flexor reflex to the contralateral limb?
severa excitatory interneurones cross the spinal cord and excite the contralateral extensors and at the same time there is inhibition of the contralateral flexors.
Sensory info ascends to the brain in the contralateral spinothalamic tract
This helps maintain balance.
What is faster the flexor and crossed extensor reflex or the stretch reflex
the stretch reflex because nociceptive sensory fibres have smaller diameter than muscle spindle afferents and so conduct more slowly
How can the GTO reflex be over-ridden?
by voluntary input from the CNS via descending excitation of motoneurons
How can the stretch reflex be overridden?
via strong descendin inhibition hyperpolarizes alpha motoneurones.
What are the 3 levels of motor control, what are their functions and what are the structures involved?
level high, function strategy and association neocortex, basal ganglion involved.
Level middle, function tactics and motor cortex, cerebellum involved.
Level low, execution function, brain stem and spinal cord involved.
Label the pathways of the spinal cord
on sheet
What is the function of the lateral pathways?
control voluntary movements of distal muscles, under direct cortical control
What is the function of ventromedial pathways?
Control posture and locomotion and are under brainstem control
Is the corticospinal tract motor or sensory?
2/3 of the corticospinal tract originates in areas 4 and 6 of the frontal motor cortex, the rest of somatosensory
What is the function of the corticospinal and rubrospinal tracts?
they are the 2 lateral pathways that control voluntary movements.