Ch 8 The Sensorimotor system Flashcards
the 3 principles of the sensorimotor cortex
- hierarchally organized (high levels is association cortex: goals and planned movements, low levels are muscles)
- lower levels do alot of unconsous stuff to leave higher levels with more resources - motor input is guided by sensory input (sensory feedback) except for ballistic movements (swatting a fly)
- learning can change the nature and locus of sensorimotor control (shift in conscious control to automatic)
the two major areas of the sensorimotor association cortex
Posterior Parietal Association Cortex:
Integrates spatial and sensory information about body position and external objects.
Directs behavior through spatial awareness and attention.
Dorsolateral Prefrontal Association Cortex:
Receives input from the posterior parietal cortex and directs motor areas to initiate voluntary movement.
Interaction with Posterior Parietal Cortex:
Decision-making for movement initiation based on spatial and sensory information.
input and output of Posterior Parietal Association Cortex:
Input Sources:
Visual, auditory, somatosensory.
Output:
Sends info to motor cortex, premotor cortex, and frontal eye field.
input output of Dorsolateral Prefrontal Association Cortex:
- Gets info from the posterior parietal cortex
- Sends info to the secondary and primary motor cortexes, and the frontal eye field
Decisions to initiate voluntary movements, but decisions depend on the interactions with the posterior parietal cortex
- Sends info to the secondary and primary motor cortexes, and the frontal eye field
damage to posterior parietal association cortex
apraxia (trouble moving if asked)
contralateral neglect
areas of the secondary motor cortex
Supplementary Motor Area: Extends into the longitudinal fissure.
Premotor Cortex: Runs laterally from the supplementary motor area.
secondary motor cortex gets input from and sends signals to
association cortex
primary motor cortex
role in movement of the secondary motor cortex
Programs movement patterns after receiving input from higher areas.
where is the primary motor cortex located
precentral gyrus of the frontal lobe
current view of primary motor cortex
More flexible organization than previously thought. Movement is often goal-directed, considering the endpoint, not just direction.
Plasticity of the sensorimotor system, allowing adaptation.
purpose of primary motor cortex
Major point of convergence of cortical sensorimotor signals
Major departure point of sensorimotor signals from the cerebral cortex
lesions to primary motor cortex cause
Disrupt independent movements, reduce speed/accuracy, and impair sensory feedback like stereognosis (identifying objects by touch).
point of basal ganglia in movement
Responsible for execution of all desired movements communicated from the cortex
Modulates motor function and supports habit learning.
Also control inhibition in unwanted movements
point of cerebellum in movement
controls repetitive movements that require aiming and timing
involved in motor learning, especially sequences of movement.
half neurons in brain
neural signals go from PMC to motor neurons in 2 types of descending pathways which are
Dorsolateral Motor Pathways:
Descend to control distal muscles (e.g., fingers).
Ventromedial Motor Pathways:
Descend to control proximal muscles (e.g., shoulder muscles, posture).
similarities in the descending motor pathways
Both have 2 tracts, one axons synapse in the brain stem, one neurons descend to the spinal cord
differences in the descending motor pathways
Ventromedial pathways are diffuse and control whole-body movements, whereas dorsolateral pathways are more focused on fine motor control of limbs.
muscle Receptor Organs:
Golgi Tendon Organs: Respond to muscle tension. protective function
Muscle Spindles: Respond to muscle length.
what NT is released by muscles for them to contract in one direction is
acetylcholine
all of the motor neurons that innervate the fibres of a single muscle are called its
motor pool
fast vs slow muscles
fast contract quicker but get tired faster ass they create great force
slower and weaker but longer lasting
synergistic muscles
antagonistic
contraction produces the same movement
produce opposite movement (extensors and flexors)
isometric vs dynamic contraction
isometric: activation of a muscle can increase the tension that it exerts on two bones without shortening and pulling them together: increase force of pull without shortening
dynamic: shorten and pull together bones from a muscle
muscle spindle feedback circuit
spindles have intrafusal muscles innervated by intrafusal neurons
wihtout the motor input muscle is slack and spindle becomes unresponsive to stretch during contraction
intrafusal motor neurons function to adjust the muscle length, keeping the spindle tense
