Sensorimotor System Flashcards
Reflex
A simple, stereotyped, unlearned response to a particular stimulus
Movement
A single relocation of body part
Act
A complex, sequential behavior
Motor plan
A set of muscle commands that are established before the action occurs
High level of motor control hierarchy
Association and secondary motor cortex establish a goal of movement and the best strategy to accomplish it
Middle level of motor control hierarchy
Primary motor cortex is involved in the sequence of muscle contraction to accomplish a goal, while the basal ganglia and cerebellum modulate activity of organized control systems to make movement more effective and controlled
Lower level of motor control hierarchy
Brain stem integrates motor commands from above and relays back sensory information to the forebrain, while the spinal cord involves the activation of motor neurons that generate movement and adjustments in response to sensory information
Antagonistic muscles
Muscles that oppose the action of another (ex: triceps and biceps)
Synergistic muscles
Muscles that assist in synergy with an antagonistic muscle
Fast-switch muscles
Muscles that contract greater force but fatigue faster because there’s less blood flow to the area (ex: jumping)
Slow-switch muscles
Muscles that contract weaker force but sustains contractions because there’s more blood flow to the area (ex: walking)
Muscle signal pathway
- Lower motor neuron in the ventral spinal cord send their axons out the ventral roots to the periphery
- The axons split into axon collateral branches that come into contact with muscle fibers, allowing an action potential to reach the muscle
- Lower motor neurons connect to a muscle allowing upper motor neurons to connect to lower motor neurons (neuromuscular junction)
- Acetylcholine is released to allow for muscle contraction at axon collaterals
Motor unit
A single motor neuron and all the muscle fibers it innervates
Muscle spindle
A capsule buried in other muscle fibers that contain intramural fibers responding to muscle stretch
Golgi tendon organ
Sensory organs embedded in tendons that are sensitive to muscle tension so that pressure builds in the tendon
When muscles are relaxed, what is the activation of muscle receptors?
No tension so no Golgi tendon organ activity, and no stretch, so no muscle spindle activity
When muscles are lengthened, what is the activation of muscle receptors?
Tension so Golgi tendon organ is activated, and stretch so no muscle spindle activity
When muscles are contracted, what is the activation of muscle receptors?
Tension so Golgi tendon organ is activated, but no stretch so no muscle spindle activity
Reciprocal innervation definition
Activating one muscle by contraction simultaneously inhibits another antagonistic muscle
Reciprocal innervation pathway
- A weight dropped into the hand stretches the bicep muscle
- The stretch excites the muscle spindle, which sends action potentials to the dorsal spinal cord
- The action potential synapse onto motor neurons in the spinal cord that cause the biceps to contract, restoring the arm to its original position
- The muscle spindle also excites interneurons that inhibit triceps motor neurons through GABA, causing the triceps to relax when the biceps contract
Pyramidal system pathway
- Large pyramidal neurons in the primary motor cortex (M1) are upper motor neurons that encode the extent, direction, and speed of movement
- Descending motor pathways connect with the ventral horn of the spinal cord
- Motor pathways synapse on the lower motor neurons
How are the neurons in the primary motor cortex organized?
They’re organized somatopically (like homunculus) and contraleterally
Lateral corticospinal system
Controls distal muscles and individual or fine movements of the arms and legs
Ventral corticospinal system
Controls proximal limb muscles and whole body movements
Supplementary motor cortex
Initiates preplanned movement in the moment before you move
Premotor cortex
Incorporates context and intent to signal the preparation of movement
Posterior parietal association cortex
PPAC; provides spatial representation of the body in space, with multimodal input from visual, auditory, and motor neurons
Apraxia
The inability to perform movements on command so that movements are performed when not conscious of it from damage to PPAC
Neglect
Failing to respond to visual, auditory, and somatosensory stimuli from damage to the PPAC
Prefrontal cortex
Evaluates the consequences of actions and develops strategy to determine which is the best or right approach to movement
Mirror neurons
Neurons activated when an individual makes goal-directed movements and when observing someone doing goal-directed movements
Extrapyramidal systems
Systens regulating and fine-tuning motor commands
Cerebellum functioning in extrapyramidal systems
Integrates and coordinates activity of sensorimotor system structures to correct deviations from intended movements
Basal ganglia functioning in extrapyramidal systems
Modulates conscious and proprioceptive movements
