Motor Control and Plasticity Flashcards
Muscle fibers are made up of ____________, which are made up of ___________.
- Sacromeres; myofibrils
- Sacromeres; myosin
- Myosin; myofibrils
- Myofibrils; sacromeres
Myofibrils; sacromeres
(The correct answer is ‘myofibrils; sacromeres’ - muscles are made up of muscle fibers, which in turn are made up of smaller units called myofibrils. Within myofibrils are many sarcomeres - the units containing actin/myosin that will slide past each other during muscle contraction.)
Motor neurons make up the final common pathway because…
- If activated, they will release enough acetylcholine at the NMJ to guarantee muscle contraction
- If activated, they will release enough acetylcholine at the NMJ to guarantee muscle relaxation
- If activated, they will release enough glutamate at the NMJ to guarantee muscle relaxation
- If activated, they will release enough glutamate at the NMJ to guarantee muscle contraction
If activated, they will release enough acetylcholine at the NMJ to guarantee muscle contraction
(The correct answer is ‘If activated, they will release enough acetylcholine at the NMJ to guarantee muscle contraction’ - this is the final decision point for whether muscle contraction will occur, because once activated, these motor neurons will cause muscle contraction due to their release of acetylcholine at the NMJ.)
At Starbuck’s the barista places your mocha-awesome-double-shot-soy-latte on the counter. Your ___________________, is the motor planning region that will be activated as you plan to grab your drink. To actually grab your drink, you will activate the ________________________ which is the executive controller of voluntary movement.
- supplementary motor area; primary motor cortex
- premotor cortex; basal ganglia
- supplementary motor area; basal ganglia
- premotor cortex; primary motor cortex
premotor cortex; primary motor cortex
(The correct answer is ‘premotor cortex; primary motor cortex’ - your coffee is an external stimulus, so the motor planning region involved is the premotor cortex. To execute a voluntary action, the primary cortex must be activated.)
The ion most critical of initiating muscle contraction is _____________.
- Acetylcholine
- K+
- Ca2+
- Na+
Ca2+
(The correct answer is ‘Ca2+’ - calcium - released from the sacroplasmic reticulum - causes a conformational change in actin, allowing the myosin head to bind and pull the filaments into increased overlap)
John is a ballet dancer. When he sees someone doing a dance he knows how to do, we would expect to see:
- activation in his premotor cortex
- activation in his visual cortex
- Both A and B
- Neither A nor B
Both A and B
(The correct answer is ‘Both (a) & (b)’ - anyone will show activation of the visual cortex while seeing someone dance, but John will also show premotor cortex activation because of his history of dancing ballet.)
Nonprimary motor areas are especially active
- during the preparation of reflexes.
- following the completion of movements
- following the completion of reflexes
- during the preparation of movements.
During the preparation of movements.
(The correct answer is ‘during the preparation of movements.’ - non primary areas are involved in movement planning. Reflexes will occur without the input of the brain.)
Rotation of the myosin head after conformational change in actin causes muscle the actin (thin) and myosin (thick) filaments to
- Move further apart
- Slide past one another
- Shrink
- Produce new filaments
Slide past one another
(The correct answer is ‘slide past one another.’ - After a conformational change in actin that reveals a binding site for the myosin head, we see an increase in overlap between the thin and thick filaments, caused by them sliding past one another.)
Which of the following would send information via the corticospinal tract?
- Primary motor cortex
- Basal ganglia
- Supplementary motor area
- both (a) & (C)
- both (b) & (C)
both (a) & (C)
The primary motor cortex and SMA are cortical areas that will send signals via this tract.
A motor unit with a high innervation ratio will control
- movements associated with sudden actions
- fine movements in small muscles
- coarse/large movements in large muscles
- Slow fibers
Coarse/large movements in large muscles
(The correct answer is ‘coarse/large movements in large muscles’ - high innervation ratios mean there are many branches of the axon that innervate the muscle within a motor unit. This is necessary for control of large movements because these muscles are large and you need a coordinated contraction across the muscle fibers.)
If the golgi tendon organ is activated, it will lead to ____________ of the associated muscle.
- Stretching
- Contraction
- Relaxation
- Supination
Relaxation
(The correct answer is ‘relaxation’ - the Golgi tendon organ responds when there is too much tension on a muscle, and signals for relaxation, by inhibiting APs that would cause muscle contraction)
What question do sensory systems concern?
How do we take in information from the outside world?
What questions do motor systems concern?
How do we act on the world (and react)?
What makes up skeletal muscles?
Muscle fibers
Muscles contain hundreds to millions of muscle fibers
Muscle fibers are made up of _______.
Myofibrils
Myofibrils contain thick and thin filaments which are known as ____ and ______.
Thick: myosin filaments
Thin: actin filaments
In a muscle contraction, thick and thin filaments…
side past each other
This is initiated through an action potential.
We have to be able to _____ from our brain to our muscles to move.
signal
We have to be able to receive __________ from our muscles, tendons, and joints to monitor movement.
sensory feedback
The spine and brain control our muscles through __________.
motor neurons
Motor neurons are the _____ ________ _______.
final common pathway
What is the final common pathway?
Information-processing pathway consisting of ALL motor neurons in the body
(Receive and integrate motor signals –> direct movement)
Motor neurons meet muscle fibers at the ______________.
Neuromuscular Junction (NMJ)
Instead of a neuron synapsing on a neuron, here a neuron synapses on a muscle fiber.
How does the brain signal muscles to move?
- Motor neurons integrate signals from hundreds to thousands of synapses.
- If EPSPs outweigh IPSPs, AP initiated
- AP travels down myelinated axon.
- Axons split into branches near target muscle
- At axon terminal, ACh released
What is so special about excitation at the NMJ?
If AP reaches terminal, almost 100% guarantee that a muscle fiber will respond by contracting.
(This happens because A TON of ACh is released at the terminal.)
What is a motor neuron?
A single motor neuron and all the muscle fibers it innervates, via axonal branches
True or False:
ALL muscle fibers will respond to an AP sent down the motor neuron.
True
What is the innervation ratio?
The number of muscle fibers innervated by one motor neuron
Muscles involved in fine movements have a ____ innervation ratio.
low
Muscles involved in gross movements have a _____ innervation ratio.
high
