Motor Unit Flashcards
Lower motor neurons
efferent
alpha motor neurons
The motor neurons that are attached to muscle cells
Motor unit
One alpha motor neuron with all of the skeletal muscle cells it attaches to. Basically how many axon terminals it has influences how many muscles cells it attaches to and they all receive the same response and move the same.
The size of the motor neuron correlates with
the function of it. For example, muscles involved in fine motor movement like fingers have small, 3-5 axon terminal neurons whereas muscles in out legs and back can have thousands of muscle fibers per unit.
Muscle twitch
The contraction generated by a single action potential
Three components of a muscle twitch
Latent period, contraction phase, and relaxation phase
Latent period
muscle cell has relieved action potential, the time it takes for calcium to diffuse out of the SR to bind to troponin. Tension is present
Contraction phase
associated with cycling of cross bridges
Relaxation phase
when the muscle comes to it normal length again
How does the muscle move so smoothly?
The motor units contract asynchronously meaning they do not all fire at once
Muscle tone
the random, sporadic firing of motor units when at rest. It keeps the muscle a little bit contracted at all times.
-The benefits of muscle tone is it takes up the slack for when the muscle is to contract and it deters atrophy
What happens when a motor neuron is cut?
The muscle cells do not receive signals and they get flaccid paralysis
Isometric contraction
Tension is increased but length is not, same length, maintaining posture
Isotonic contraction
muscle length increases but muscle tension does not. Tonic = tension.
Concentric contraction
type of isotonic contraction, muscle generates tension and the whole muscle contracts. Curling a weight from your waist to your shoulder. Cause more damage, tearing, of muscle than eccentric contractions
Eccentric contraction
type of isotonic contraction, The tension remains but the muscle is lengthening. Weight going from the shoulder down to the waist. Can generate more force than concentric contractions can.
Muscle size is determined by what
the number of myofibrils present and thus more myofilament proteins. Strength training produces more proteins
Heterotrophy
The increasing of size of muscle through the extra production of myofilament protein. This happens because micro-tears happen to the myofibrils. Muscle soreness. an increase in muscle size is often accompanied by more connective tissue building up
How do you increase the force of a muscle?
By increasing the number of motor units that fire at one time. This is called recruitment
Wave summation
When action potentials are received at a rapid and increasing rate. There is no refractory period with muscle tissue so they can be stimulated at any time.
The four ways that our bodies get ATP
cytosolic, creatine phosphate, glycolysis, aerobic or oxidative respiration
Cytosolic
anaerobic, freely floating in the cytoplasm, can be used to fuel 3-4 seconds
Creatine phosphate
gives away its phosphate freely to ADP, also anaerobic , requires enzyme. Extends muscle contraction to 10 seconds just from ATP from the pool
Central fatigue
The feeling of being tired in the brain. Training helps us get over this physiological fatigue, to recognize the feeling and continue to perform even when it is uncomfortable
