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.
What are the 2 ventromedial pathways that control posture and locomotion?
Vestibulospinal and tectospinal tracts.
What is the function of the vestibulospinal tract?
stabilises head and neck
What is the function of the tectospinal tracts?
ensure eyes remain stable as the body moves
What 2 ventromedial pathways control trunk and antigravity muscles?
pontine and medullary reticulospinal tract
What is the function of the pontine and medullary reticulospinal tract?
use sensory information about balance, body position and vision, they reflexly maintain balance and body position and innervate trunk and antigravity muscles in limbs.
What is the function of the primary motor cortex and the pre-motor areas?
they plan and control precise voluntary movements.
What is the function of the medial tracts from the spinal cord?
they control posture, balance and orienting mechanisms
What is the function of the lateral tracts from the cortex?
control precise skilled voluntary movements
Label origins, destination and functions of upper and lower motor neurones
on sheet
What number is the area of the brain that is the primary motor cortex?
area 4
What number is the area of the brain that is the premotor and supplementary motor areas?
area 6
What does the supplementary motor area innervate?
SMA innervates distal motor units directly
What does the premotor area innervate?
Innervates the proximal motor units by connecting with reticulospinal neurones
What is the mental image of body in space generated by?
somatosensory, proprioceptive and visual inputs to posterior parietal cortex (areas 5 and 7)
What is the difference in activity of the brain if you think about completing an action rather than doing the action?
Area 6 is active but area 4 is not.
Area 4 is for doing
What is pain?
An unpleasant sensory and emotional experience which we primarily associate with tissue damage or describe in terms of such damage or both
What is nociception?
The detection of tissue damage by specialised transducers connected to A-delta and C fibres
WHat is the difference between lateral and anterior spinothalamic tracts?
lateral STT- conveys fast and slow pain (pain and temperature)
Anterior STT- conveys sensation of simple touch
What is allodynia
decreased threshold for response
What is hyperalgesia?
exaggerated response to normal and supranormal stimuli
What is spontaneous pain
spontaneous activty in nerve fibres
What is wind up sensation
winding up response to input, the homosynaptic activity dependent progressive increase in response of the neurons
What is central sensation- classical
Opening up of new synapses in the dorsal horn, outlast the initial stimuli duration
Difference between acute and chronic pain
acute- <1 month, presence of noxious stimuli, pain resolves upon healing and serves a protective function
Chronic- 3-6 months, pain beyond expected period or healing, degrades health and function
What is nociceptive pain?
a sensory experience that occurs when specific peripheral sensory neurons (nociceptors) responds to noxious stimuli
Describe nociceptive pain?
painful region is localised at site of injury, time limited but can be chronic (eg osteoarthritis), responds to analgesics
What is neuropathic pain?
pain initiated or caused by a primary lesion or dysfunction in the somato-sensory nervous system
Describe neuropathic pain?
may not necessarily be at the same site of injury- as pain occurs in neurological territory of the affected structure, normally a chronic condition and responds poorly to conventional analgesics
Treatment for transduction
NSAIDs, Ice, rest, LA blocks
Treatment for transmission
nerve blocks, drugs- opioids, anticonvulsants, surgery- DREZ, cordotomy
Treatment for perception
education, cognitive behavioural therapy, distraction, relaxation, graded motor imagery, mirror box therapy
Treatment for descending-modulation
placebos, drugs- opioids, antidepressants, surgery-spinal cord stimulation
