Motor System Flashcards
Motor = ?
movement
Involuntary movement?
triggered by stimulus and the brain isn’t involved (so it doesn’t require conscious effort)
Voluntary movement?
Requires conscious effort and is all planned out before the action(s) are executed (think MASTERMIND)
Ultimate target of all motor neurons?
The muscles.
How does muscle contraction work?
lower motor neurons synapse directly onto the muscle releasing acetylcholine as their neurotransmitter in the space between the terminal and the muscle (called the neuromuscular junction)
when the signal is recieved the muscle cells are depolarized allowing the flow of calcium into the cell
the calcium starts a chain reaction in the myofibrils causing the thin and thick filaments to slide past each other this shortens the myofibril and causes contractions
this can also happen in reverse if there is an absence of acetylcholine in the lower motor neurons
Where are the cell bodies of lower motor neurons located?
Spinal cord
Where are the cell bodies of upper motor neurons located?
Brain and brainstem.
Where do lower motor neurons mostly get their information from?
The upper motor neurons (likely cause their closer to the brain)
How does the knee jerk (myotatic) reflex happen?
a rubber mallet is hit on the tendon which is connected to the quadriceps muscle. the tendon is pulled therefore pulling the muscle. this triggers action potential in the muscle spindle. the muscle spindle sends the info through its axon (afferent) to the lower motor neurons of the quadriceps muscle in the spinal cord via the dorsal. the lower motor neurons tell the knee to jerk. since the brain isn’t involved in the action, you can’t consciously respond.
What is the primary motor cortex?
works and plans voluntary actions
What is motor planning?
mapping out which muscles and limbs are needed to perform a behavioral goal
What other parts of the brain does the primary motor cortex work with to plan voluntary actions?
Works with the supplementary cortex and the premotor cortex
What do scientists use to predict an organism’s behavior before it occurs?
The cell bodies that are highly active before the act is initiated.
What are the two Lateral Pathways?
Corticospinal tract and the Rubrospinal tract
Describe the Corticospinal tract.
runs from the cerebral cortex to the spine starting in the primary motor cortex
axons from these organs run through the white matter of the brain and brainstem where they form a bump on each side of the medulla (this pathway is also referred to as the pyramidal tract?
at the bottom of the medulla, this pathway crosses to the other side to go down the spinal cord
these axons synapse on lower motor neurons in the central grey matter of the spinal cord
longest neurons in the body because they come from the brain to the targeted muscle
Describe the Rubrospinal Tract.
not as crucial to the human body as it is to other animals
begins in a small region of the brainstem called the red nucleus
crosses over at the midbrain before descending
seems to be in control of muscle tone
What both Lateral Pathways have in common?
most voluntary info is carried
these pathways are found in the white matter on the sides of the spinal cord
sometimes the corticobulbar system is included with the lateral pathways despite not being in the spinal cord. it controls the brainstem nuclei that innervate the cranial muscles that control voluntary facial movements.
What are the three Ventromedial Pathways?
Vestibulospinal Tract, Tectospinal Tract, and Reticulospinal Tract
Describe the Vestibulospinal Tract.
originates in the vestibular
organs of the inner ear
provides info about the direction of gravity, spin, and other forces
most of the axons project up to the brain to make the organism aware of the forces
some of the axons project down to compensate for the changes in force for the neck and head and leg muscles for balance
Describe the Tectospinal Tract.
originates in the roof or tectum of the midbrain
controls the movement of the head in response to auditory and visual stimuli
Describe the Reticulospinal Tract.
originates in the reticular formation found in the pons
targets the torso and legs to go against the forces of gravity and the keep balance
What two regions affect the output of the descending motor pathways?
The Basal Ganglia and the Cerebellum.
Where is the Basal Ganglia located?
it’s a group of structures located deep within the cerebrum
What is the Basal Ganglia associated with?
initiating and executing movements
What does the Basal Ganglia do?
prevent unwanted movements and promotes necessary ones to completing the certain action
Where is the cerebellum located?
in the back of the brain beneath the occipital and temporal lobes
What does the cerebellum do?
feedback control system; constantly adjusting and comparing desired output to the input to get the desired results
always improving
What cool cell does the cerebellum have?
Purkinje cell: almost 2 dimensional with their coral array dendritic branches all the output comes from these cells
