Performance Objectives.
Describe the structures and processes leading to voluntary movement.
Control of voluntary movement is complex and require the cooperation of many areas of the brain as well as several subcortical areas. The first step in performing a voluntary movement occurs in subcortical and cortical motivational areas, which send signals to the association cortex, which forms a "rough draft" of the planned movement. The movement plan is then sent to both the cerebellum and the basal ganglia. These structures cooperate to convert the "rough draft" into precise temporal and spatial excitation programs. The cerebellum is important for making fast movements, while the basal are more responsible for slow or deliberate movements. From the cerebellum and basal ganglia, the precise program is sent through the thalamus to the motor cortex, which forwards the message down to spinal neurons for "spinal tuning" and finally to skeletal muscle. Feedback to the CNS from the muscle receptors and proprioceptors allows the modification of motor programs, if necessary.
Give examples of response and adaptation. What is the difference between the two?
-Example of response: such as walking, to jogging, then running. Heart rate, respiration, BP, and blood flow increases during these exercises. -Example of adaptation: for specific activities such as training, like for endurance. Hypertrophy, resting heart rate, increase strength, "VO2 max" --The difference between the two is response is physiological changes that occur going from one exercise state to another. While Adaptation is the physiological changes that occur with regular (chronic ) participation in exercise. (Long term changes)
List and define the four different properties of muscles
1. Irritability: Recieve and propagate action potential 2. Contractility: Contract/shorten and exert force 3. Extensibility: Ability to lengthen 4. Elasticity: Return to a pre-contraction length
Show graphically the relationship between the force exerted and velocity of contraction. (shortening)
As the force developed by a muscle (or load lifted) is increased, the velocity of muscle shortening (also limb movement) decreases
Define and list the steps involved in excitation-contraction coupling.
Ca+ binds with troponin, and then topomin moves the tropomyosin molecules off the active sites on the actin filament, opening these sites for binding with the myosin head. Once it binds with the actin active site, the myosin head tilts, pulling on the actin filament so that the two slide across each other. The tilting of the myosin head is the power stroke. Energy is required before the muscle action can occur. The myosin head binds to ATP and ATPase found on the head splits ATP into ADP+P, releasing energy to fuel the contraction.
Describe the movement of ions involved in depolarization and repolarization of the cell
Depolarization: Reversal of polarity; opens Na+ channels and Na+ diffuses into cell; inside becomes more positive Repolarization: RE-establishment of polarity; return to resting membrane potential; K+ leaves the cell rapidly; Na+ channels close
The golgi tendon organ monitors change in muscle length? True or false Explain briefly
False; the GTO monitors changes in tendon tension, while muscle spindles monitor changes in muscle length. If a muscle lengthens sufficiently to apply rapid tension to the tendon however, the GTO will perceive this
Contrast hypertrophy, hyperplasia, and atrophy.
Hypertrophy is the increase in cell size Hyperplasia is the increase in cell number, Atrophy is the degradation or wasting of the cell
Show graphically the relationship between the load and work
If a particular load can be moved a given distance,the mechanical work completed increased in direct proportion (linearly) with increasing load
Diagram a schematic representation of a motor unit and explain innervation ratio.
Innervation ratio is number of muscles innervated per motor neuron. Muscle groups which perform fine movement have a very low innervation ratio, muscle groups which perform large gross movements have a very high innervation ratio.
Differentiated among isometric, isotonic, and isokinetic muscle contraction.
Isometric contractions maintain a constant joint angle through the contraction. Isotonic contractions maintain the same muscle tension throughout the contraction. Isokinetic contractions maintain the same velocity throughout the contraction.
Show graphically the relationship between the length of a muscle and maximal tension exerted
Maximal strength is greatest during eccentric contraction, followed in descending order by isometric and concentric contraction.
Describe the general structure of a muscle spindle and discuss its physiology function
Muscle spindles consist of extrafusal fibers, intrafusal fibers, and annulospiral endings. It allows neural information to be relayed back to the CNS of muscle stretch, muscle length, and the rate of change in muscle length.
If the sarcoplasmic reticulum was removed from a muscle fiber, would that fiber contract in response to an impulse reaching the myoneural junction? Why or why not?
No, because there would be no Ca++ released with which to move the tropomyosin from the active sites.
Describe and diagram an EMG for the different types of muscle contraction at the same load for a fatigued and non-fatigued muscle.
Non-fatigues:More electrical activity for concentractions Fatigued: Electrical activity increases in eccentric contractions and begins to look similar to electrical activity produced by concentric contractions
Show graphically the relationship between the load and power output
Power increases with load only to a certain point and then it decreases (inverted-U)
List the important components of the muscle cell and diagram a schematic representation of the sarcomere
Satellite cell Skeletal muscle fiber sarcomere A-band I-band H-Zone M-line Z-line Myofibril Myofilaments: Actin and myosin
List three functional characteristics that differentiated slow motor units from fast motor units.
Slow units do not fatigue easily, fast motor units utilize a glycolytic metabolism as opposed to an oxidative metabolism, and fast motor units generate more power.
Compare and contrast slow and fast- twitch skeletal muscle with respect to biochemical and contractile characteristics.
Slow-twitch: Type 1, oxidative, dark in color, slow contraction speed, endurance performance, many mitchondria, high myoglobin, small fiber, low anaerobic enzyme. Fast-twitch: TypeII, glycolytic, lighter in color, fasst contraction speed, poor endurance, few mitochondria, low myoglobin, large fiber, high anaerobic enzyme.
Describe and draw a schematic of the withdrawal and crossed-extensor reflex.
Stimulation causes you to push away on the contralateral side. Related to withdrawal reflex (pull away)
Discuss the function of the Golgi tendon organs in the monitoring tension.
The GTO monitors tendon tension, the action potentials of which are directed to the spinal cord. Synapse on an inhibitory interneuron, which inhibits A-motor neuron
Describe how the force/tension developed within a skeletal muscle can be regulated (increased or decreased)
The amount of force generated during muscular contraction is dependent on types and number of motor units recruited, the initial muscle length, and the nature of the motor unit's neural stimulation. The addition of muscle twitches is termed summation. When the frequency of neural stimulation to a motor unit is increased, individual contractions are fused together in a sustained contraction called tetanus. The peak force generated by muscle decreased as the speed of movement increase. however, in general, the amount of power generated by a muscle group increases as a function of movement velocity.
Describe the action potential of the cell.
The depolarization wave that travels across a muscle cell which elicits contraction. Na+ is released into the muscle and causes the charge to become positive. Na+ channels close and K- is released, causing the charge to become a negative again
Describe the all-or-none principle with regards to the motor unit.
The force speed of contraction is controlled at the spinal cord level by the number and frequency of motor units recruited.
Describe the resting membrane potential of the cell
The magnitude of the negative charge of the muscle cell, which is a measure of possible action potential
Describe the events involved in muscle contraction beginning with the nerve impulse at the myoneural junction and ending with relaxation of the muscle.
The motor nerve releases, ACH, which opens ion gates in the muscle cell membrane and allows NA+ to enter the muscle cell. Action potential travels along the sarcolemma, then through the tubule system. Ca+ is released from the SR. Ca+ binds to troponin, causing tropomyosin to roll away which exposes the active site on actin. Myosin cross-bridges attach to active sites on actin, pivot, and pull on thin filaments. ATP replaces the ADP+P, allowing myosin and actin to detach and reposition. When Ca+ is actively pumped back into the SR, tropomyosin re-covers actin sites.
Describe and give an example of the stretch reflex
The stretch reflex is important in controlling muscle length. Results in immediate contraction of related muscle groups upon presentation of rapid stretching. Best example is the striking of the patellar tendon with a rubber mallet, resulting in contraction of the quadriceps
What does Exercise Physiology mean?
The study of the physiological response and adaptation of exercise
Describe the importance of muscle fiber type and performance of various physical activities.
Type I is important for participation in activities that require the athlete to be light and perform for long duration's such as cycling, distance running, and swimming. Type II is important for participation in activities that require the athlete to generate both force and power for short duration's, such as weightlifting and swinging a baseball bat.
Contrast muscle fiber response to weight training and endurance training.
Weight training: Hypertrophy, new myosin and actin filaments develop, possible conversion from type IIa to type IIb fibers, increased glycogen storage capacity, increased motor recruitment. Endurance training: Increase in oxidative effciency, possible conversion from type IIb to type IIa fibers, increased in number of mitochondria.
Describe the role of the sarcoplasmic reticulum in muscle contraction and relaxation
When the SR is stimulated, it releases Ca+ which leads to muscle contraction. When the SR ends the supply of Ca+, it leads to muscle relaxation.
Contrast temporal and spatial summation at a motor neuron.
temporal summation is the increase in frequency at which muscle units contract, whereas spatial summation is the increase in the number of muscle units contracting. Both increase force output and improve the efficiency of the nervous system
