Neur 241- Exam Two, p.2

Motor plan

Simple movements strung together into a plan

Originates in the prefrontal cortex, PRIOR to the movement

Skeletal muscles

Important for determining which movements are available to us

Antagonistic v. synergistic muscles

Working against each other v. working together

Activation of a muscle must ALSO inhibit the antagonist

Motor unit

Neuron and all the muscle cells/fibers that it innervates

Importance of multiple axon collaterals

Multiple branches of an axon control different fibers of a muscle, allowing the brain to cycle through different fibers in each muscle when fatigued

Neuromuscular junction, neurotransmitter and receptor

Synapse at which neuron innervates muscle, using Acetylcholine and the nicotinic receptors

Proprioception and neurons involved in it, importance

Ability to know where one’s limbs are in a given moment

Muscle spindles and golgi tendon organs

Muscles without sensory neurons for proprioception couldn’t control limbs, unless visual cues were present

Muscle spindles

Sensory receptors that relay information when a muscle is contracted (stretched)

Communicate how bent/extended a limb is

Golgi tendon organs

Sensory receptors located on the tendons (muscle to bone) that sense tension

Precentral gyrus

Also known as the primary motor cortex, or MI

Topographically mapped and plastic

Pyramidal motor system pathway

1. Neurons in motor cortex

2. Synapse and cross over in the medulla

3. Spinal cord

4. Target muscle

Nonprimary motor cortex components

Composed of premotor cortex and supplementary motor area

Supplementary motor area

Important for the initiation of movement, amplitude and direction of movement, and movements performed from memory

Receives projections from the basal ganglia (which is implicated in PD and Huntington’s)

Premotor cortex

Contains cerebellum, which is important for fine-tuning programs for skilled movements (automatic/muscle memory), and gives inhibitory outputs for fine-motor control (precision)

Some plasticity for those born without the cerebellum, although plastic effects are lesser in adulthood

Mirror neurons

Found in nonprimary motor cortex, and same neurons fire for your movement and watching others perform the movement

Discriminatory and only found in specific actions, when brain is imagining itself performing an action