Muscular System Flashcards
What are the three types of muscular tissue in the body?
- Cardiac
- Smooth
- Skeletal
Describe skeletal muscle.
- striated or voluntary muscle
- skeletal muscle contractions can be voluntarily controlled
Describe cardiac muscle.
- composes the bulk of the heart
- muscle fibers are branched
- dark bands called intercalated disks
- interconnections of cardiac muscle fibers allow the hear to contract efficiently as a unit
Describe smooth muscle.
- involuntary, smooth, or visceral muscle
- lacks striations
- found in the walls of hollow structures, such as digestive tract, blood vessels, etc.
- contractions are not voluntary
Describe the structure of skeletal muscle.
- striated
- connective tissue forms ‘wrappers’ around each muscle fiber, around fascicles (groups) of muscle fibers, and around the entire muscle
- most skeletal muscles extend from on bone across a joint to another bone
What are the three regions of a skeletal muscle?
- Origin - attachment to the bone that remains relatively stationary or fixed when movement at the joint occurs
- Insertion - point of attachment to the bone that moves when a muscle contracts
- Body - main part of the muscle
How are muscles attached to bones?
Muscles are attached to bone by tendons - strong cords or sheets of fibrous connective tissues that extend from the muscle organ
What is synovial fluid?
Synovial fluid, also known as joint fluid, is a thick liquid located between your joints. The fluid cushions and protects the ends of bones and reduces friction during movement.
What is a bursae?
Small synovial-lined sacs containing small amounts of synovial fluid; located between some tendons and underlying bones.
What are the two main types of myofiliments?
- Thick myofilaments (contain myosin)
- Thin myofilaments (contain actin)
What is a sarcomere?
A sarcomere is the basic contractile unit of muscle fiber (separated from each other by dark bands called Z-lines)
Describe the sliding filament model.
- Thick and thin myofilaments slide past each other to contract
- contraction requires calcium and energy-rich ATP molecules.
What is the prime mover?
The main muscle responsible for producing a given movement.
What is the synergist?
Muscle that helps the prime mover produce a given movement.
What is the antagonist?
Muscle that opposes the action of a prime mover in any given movement.
What are the three functions of skeletal muscle?
- Movement - muscles produce movement by pulling on bones as a muscle contracts
- Posture - a continuous low-strength muscle contraction called tonic contraction (muscle tone) enables us to maintain body position
- Heat production - contraction of muscle fibers produces most of the heat required to maintain normal body temperature
What is fatigue as it relates to muscle?
- Reduced strength of muscle contraction caused by repeated muscle stimulation without adequate periods of rest.
What is lactic acid?
Produced by contractions in the absence of adequate oxygen. Contributes to muscle soreness.
What is oxygen debt?
Describes the extra oxygen needed to support the metabolic effort required to burn excess lactic acid (laboured breathing after strenuous exercise is required to “pay the debt”).
What is a motor unit?
A motor neuron plus all the muscle fibers it controls.
What is a motor neuron?
A nerve cell that transmits an impulse to a muscle causing contraction.
What is the neuromuscular junction (NMJ)?
- The place where a motor neuron communicates with a muscle fiber
- chemicals called neurotransmitters cross the NMJ to trigger muscle contraction
- Acetylcholine (ACh) is the neurotransmitter operating at each NMJ.
What is the threshold stimulus?
The minimal level of stimulation required to cause a muscle fiber to contract.
Describe the “all-or-none” response.
If stimulated by a threshold stimulus, a muscle fiber will contract completely; if the muscle fiber does not reach the threshold stimulus, it will not contract (different motor units responding to different threshold stimuli permit a muscle as a whole to execute contractions of graded force).
What are the four major types of skeletal muscle contractions?
- Twitch contractions
- Tetanic contractions
- Isotonic contractions
- Isometric contractions
What is a twitch contraction?
Laboratory phenomena, not normal muscle activity; each is a single contraction of muscle fibers caused by a single threshold stimulus.
What is a tetanic contraction?
Sustained muscular contractions caused by threshold stimuli hitting a muscle in rapid succession.
What are the two types of isotonic contractions?
- Concentric contraction - causes a muscle to shorten, so that the insertion end of the muscle moves toward the point of origin.
- Eccentric contraction - causes a muscle to lengthen under tension, this moving the insertion away from the origin.
What are isometric contractions?
- Do NOT produce movement; the muscle as a whole does not shorten; although no movement occurs, tension within the muscle increases.
What is disuse atrophy?
Breakdown of muscle due to prolonged inactivity.
What is hypertrophy?
Increase in muscle size, due to regular exercise.
What is strength training?
Exercise involving contraction of muscles against heavy resistance; increases the numbers of myofilaments in each muscle fiber.
What is endurance training?
Exercise that increases a muscle’s ability to sustain moderate exercise over a long period; sometimes called aerobic training.
What are the four angular movements produced by skeletal muscle contractions?
- Flexion - decreasing an angle
- Extension - increasing an angle
- Abduction - moving away from the midline of the body
- Adduction - moving towards the midline of the body
What are the three circular movements produced by skeletal muscle contractions?
- Rotation - moving around an axis
- Circumduction - moving the distal end of a part in a circle
- Supination and pronation - hand positions that result from rotation of the forearm
What are the two special movements produced by skeletal muscle contractions?
- Dorsiflexion and plantar flexion - foot movements (upward and downward ankle movement)
- Inversion and eversion - foot movements (sideways)
