MUSCULAR SYSTEM Flashcards
Two main aspects to muscle contraction:
electrical component
mechanical component
Electrical Component Structures
Sarcolemma
Transverse tubules
Sarcoplasmic reticulum
Mechanical Component Structures
Myofibrils
Myofilaments
3 Proteins of Actin Myofilament
Actin
Tropomyosin
Troponin
The primary function of skeletal muscle cells is to
generate force by contracting, or shortening.
The parallel arrangement of myofilaments in a sarcomere allows them to
interact, which causes muscle contraction
When sarcomeres shorten, ____, ____, _____, and ____ all shorten to produce muscle contraction
myofibrils
muscle fibers
muscle fascicles
muscles
During muscle relaxation, sarcomeres ____
lengthen
The basis of the electrical properties of skeletal muscle cells is the
movement of ions across the cell membrane
Ions can move across the cell membrane through ion channels. State the two different channels
Leak ion channels
Gated ion channels
the charge difference in unstimulated cell, results of three factors. state them.
Concentration of K+ inside the cell membrane is higher than that outside the cell membrane
Concentration of Na+ outside the cell membrane is higher than that inside the cell membrane
Cell membrane is more permeable to K+ than to Na+
The phospholipid bilayer interior is a _________ environment, which inhibits the movement of charged particles
hydrophobic
Occurs when the excitable cell is stimulated
action potential
When K+ moves out of the cell, the inside of the cell membrane becomes more ______ and the outside becomes more ______.
negative; positive.
Release of ______ at the neuromuscular junction will produce an action potential in the sarcolemma
acetylcholine
Occurs when acetylcholine is no longer released at the neuromuscular junction
muscle relaxation
keeps acetylcholine from accumulating within the synaptic cleft where it would act as a constant stimulus at the motor end-plate, producing continuous contraction in the muscle fiber.
Acetylcholinesterase
the mechanical component of muscle contraction
cause the sarcomeres to shorten and the muscle will contract
Cross-Bridge Movement
Response of a muscle fiber to a single action potential along its motor neuron
Muscle Twitch
the gap between the time of stimulus application to the motor neuron and the beginning of contraction
Lag phase/latent phase
commences once the Ca2+ released from the sarcoplasmic reticulum initiates cross-bridge formation and cross-bridge cycling.
Contraction phase
much longer than the contraction phase, because the concentration of Ca2+ in the sarcoplasm decreases slowly due to active transport into the sarcoplasmic reticulum
Relaxation phase
state the two major types of skeletal muscle fibers
Slow-Twitch Muscle Fibers (Type I)
Fast-Twitch Muscle Fibers (Type II)
contract more slowly, have a better-developed blood supply, have more mitochondria, and are more fatigue-resistant than fast- twitch muscle fibers
Slow-Twitch Muscle Fibers (Type I)
have a less-well-developed blood supply
have very little myoglobin, fewer and smaller mitochondria
contract rapidly for a shorter time and fatigue relatively quickly
Fast-Twitch Muscle Fibers (Type II)
Temporary state of reduced work capacity
Muscle Fatigue
contain less actin and myosin than do skeletal muscle cells
SMOOTH MUSCLE
the most stationary, or fixed, end of the muscle
origin
Muscle is connected to the bone by a ____
tendon
the end of the muscle attached to the bone undergoing the greatest movement
insertion
Members of a group of muscles working together to produce a movement
synergists
plays the major role in accomplishing the desired movement
Prime mover
are muscles that hold one bone in place relative to the body while a usually more distal bone is moved
fixators
effects of aging
Reduction in muscle mass
lower response time for muscle contraction
Reduction in stamina
Increased recovery time
Loss of muscle fibers begins as early as 25 years of age, and by age 80 the muscle mass has been reduced by approximately 50%
