15 - Sensorimotor System 1 Flashcards
What are the two other types of motor control apart from voluntary and involuntary?
goal-directed and habit
Where do lower and upper motor neurons meet/connect?
upper originates from higher centres and projects down to meet lower MN
lower projects from brainstem/spinal cord to muscle
thus at brainstem/spinal cord
Where is the soma of the lower motor neuron MN located?
brainstem/spinal cord
What motor control information does the basal ganglia and the cerebellum process?
basal ganglia - WHAT movement to do
cerebellum - HOW to do it
Is the sensorimotor system a descending or ascending control system?
descending control
What is the role of sensory system in the descending sensorimotor system?
to give ASCENDING SENSORY feedback
What is the general pathway of the descending sensorimotor system?
association cortex -> motor cortex -> brainstem motor nuclei -> spinal motor circuits -> motor unit -> effect
What are three types of muscle tissue?
skeletal, smooth, cardiac
How can we achieve fine tuned muscle control when the activation/contraction of muscle is by a all-or-nothing threshold?
(two ways)
by
antagonistic arrangement
recruitment of muscle fibres
What does a tendon connect?
skeletal muscle to bone
How are (skeletal) muscles arranged?
What is a muscle fibre comprised of?
What myofilaments do myofibrils contain?
made up of many muscle fasciculus which hold lots of muscle fibres
myofibrils
actin and myosin
Which NT causes muscle contraction?
This NT release triggers what in muscles?
-acetylcholine
-intracellular Ca2+ store release
-> myosin head changes shape and is now able to bind to actin filament
What does Ca2+ release trigger in muscles?
What molecule breaks bond between actin filament and myosin head?
ATP is required
What is included in a motor unit?
lower motor neuron (alpha) and all the muscle fibres it innervates
As the number of fibres a motor neuron innervates (in motor unit) deceases, does the movement resolution increase or decrease?
What is the size principle? What is it an example of?
movement resolution increases as no. of fibres decreases
-motor units are recruited in order of size (smallest first). This is an example of mediating motor control
Which neuron’s depolarisation causes contraction of muscle fibres?
How is the all-or-none concept applicable to the motor unit?
alpha lower motor neuron
all the fibres in the unit contract when alpha activates them
What are the three types of muscle fibres and what movements are they used in?
-fast fatigable (jump)
-fast fatigue resistant (run, walk)
-slow (stand)
How does training and exercises affect muscle fibres composition?
thickness of muscle fibres changes and proportion of the type of muscle fibres changes
Where are motor pools located?
What does the motor pool consist of?
spinal cord
alpha and gamma MNs
Where are the soma of sensory afferents located?
Where do sensory neurons synapse? (send info to next neuron)
dorsal root ganglia
synapse with lower motor neuron at ventral horn OR via interneuron and then alpha
What information do lower motor neurons receive at ventral horn? (ascending and descending)
ascending sensory afferent info from periphery muscles
descending information from brain
describe how antagonistic muscles work
as one contracts, the other relaxes
How do you know experimentally from quadrupeds dogs/cows that muscle reflex arcs are not controlled by higher brain powers?
because even with damage to thoracic spinal cord, quadrupeds are able to adapt to changes in speed on a treadmill
