Introduction to motor control Flashcards
what is the overall structural and functional organisation of the motor system
the motor system is functionally segregated and hierachally organised. Different areas control specific aspects of movement, and the system follows a hierachal structure with the higher brain regions directing movement and lower regions executing comands
what is the functional segregation in the motor system
functional segregation refers to the division of the motor system into distinct areas responsible for controlling different aspects of movement.
what is hierachal organisation in the motor system
hierachal organisiation means that the motor system is structred in levels, where higher centers (such as the cortex) control complex movements and lower centers (such as the spinal cord) execute basic motor commands
what is a motor unit
a motor unit consists of a single motor neuron and all the muscle fibres it innervates. Motor units vary in size and function
how is the force of muscle contractio controlled
force is controlled dby motor unit recruitment and firing rate. Smaller units (S units) are activated first, and as force demands increases, larger and more powerful units (FR and FF) are recruited. This is known as size principle.
what is size principle
the size principle states that motor units ar recruited in an orderly fashion based on the size of thier motor neurons. Smaller motor neurons (innervating slow- twitch fibres) are activated first, followed by larger ones as more force is needed
What are the different types of motor units?
S (Slow): Low force, slow contraction speed, fatigue-resistant (Type I fibers).
FR (Fast Fatigue-Resistant): Intermediate force, fast contraction, fatigue-resistant (Type IIa fibers).
FF (Fast Fatiguable): High force, fast contraction, low fatigue resistance (Type IIb/x fibers).
what is a muscle twitch
a muscle twitch is a single contraction-relaxation cycle triggered by an action potential in a motor neuron
what is tetanus in muscle contraction
tetanus is a sustained muscle contraction resulting from high frequency stimulation, causing individual twitches to fuse
what are spinal reflexes, and why are they important
spinal reflxes are automatic responses generated by the spinal cord to maintain posture and movement. They adjust for environmental changes and support voluntary movement by coordinationg muscle activity at the spinal cord level
what is the muscle spindle
the muscle spindle is a sensory receptor that detects changes in muscle length and mediates the stretch reflex
how does the stretch reflex work
muscle stretch la spindle affernts, which directly excite alpha motor neurons, leading to muscle contraction. Simuiltaneously, inhibitory interneurons suppress anatagonist muscles.
what is the role of gamma motor neurons
gamma motor neurons adjust the sensitivity of muscle spindles by controlling the contraction of intrafusal fibres.
what is the golgi tendon organ, and what does it do
the golgi tendon organ, located at the muscle-tendon junction, senses muscle tension and prevents excessive frce by triggereing autogenic inhibition
what is the golgi tendon reflex (autogenic inhibition)
when muscle force increases, lb afferents activate ib inhibitory interneurons, reducing contraction of the same muscle, preventing over- contraction
what are nociceptors, and what role do they play in reflexes
Nociceptors are sensory receptors that detect harmful stimuli. They trigger the withdrawl reflex, where flexor muscles contract and extensors relax to withraw from painful stimulus
what are the flexor and crossed extensor reflexes
Flexor reflex: Withdrawal from a painful stimulus via flexor activation and extensor inhibition.
Crossed extensor reflex: The opposite limb extends for postural support.
What types of cutaneous mechanoreceptors provide sensory feedback?
Meissner’s corpuscles: Stroking, flutter (RA1).
Pacinian corpuscles: Vibration (RA2).
Merkel disks: Pressure, texture (SA1).
Ruffini endings: Skin stretch (SA2).
how do cutaneous receptors assit in presicion grip
Meissener’s corpuscles detect microslips, triggering reflextive grip force increases to prevent objects from slipping
how is descending control intergrated into reflexes
la inhibitory interneurons reive inputs from descending pathways, allowing the brain to modify reflex responses.
how do CNS lesions affect reflex tone
damage to descending pathways often result in hyperreflexia, due to loss of inhibitory control leading to increased muscle tone and exaggerated relexes
how can the stretch reflex be used clinically
the stretch reflec assesses spinal cord integrity at specific levels, helping diagnose neurological conditions.
