Chapter 1 Flashcards
Epimysium
the connective tissue that surrounds a skeletal muscle
Muscle fibers
combine to create a muscle
fasciculus or fascicle
a bundle of muscle fibers
perimysium
the connective tissue that surrounds a fasciculus
endomysium
connective tissue that separates adjacent fibers
surrounds each muscle fibers
sarcolemma
the plasma membrane that surrounds the muscle fiber . Receives and conducts stimuli in the form of electrical impulses or action potentials
cytoplasm
contains the cell’s energy sources (ATP, phosphoreatine, glycogen, and fat droplets), mitochondria (sites of aerobic ATP), and sacroplasmic reticulum
sacroplasmic reticulum
stores calcium and regulates muscle action by altering the intracellular calcium concentration. transverse tubules (T-tubules)
T-tubules
channels that form openings in the sarcolemma of the muscle cell
Myofibrils
columnar protein structures that run parallel to the length of the muscle fiber.
A bundle of myofilaments (myosin and actin filaments)
Myosin and Actin filaments
Myosin-Thick
Actin-Thin
arranged in a regular pattern along lngth of myofibril, giving it a striped appearance
Tropomyosin
regulatory protein
rod-like protein that spans the length of seven G-actin proteins along the length of the actin filament
*Each end is attached to toponin
Troponin
Causes the movement of the tropomyosin when bound to calcium away from the myosin binding sites on actin, allowing the myosin head to attach and pull on the actin
Sarcomere
basic contractile unit of muscle, extends from z-line to z-line
H-zone
The area of A- band that contains myosin but no actin
M-line
a dark line in Middle of the H-zone that helps align adjacent myosin filaments
I-band
spans the distance between the ends of adjacent myosin filaments, lies partly ni each of two sarcolmeres
G-actin proteins
form the actin filament
*binding site for myosin head
Neuromuscular junction
where communication between the nervous and muscle systems occur
Sliding Filament Theory
Most widely accepted theory: muscle shortens or lengthens when the filaments (actin and myosin) slide past each other, without the filaments themselves changing in length.
- Action potential passes, releasing ACh at neruomuscular junction into the synaptic cleft between the axon terminal and muscle fiber
- ACh goes across synaptic cleft and binds with ACh receptors
- Leads to generation of action potential along the sarcolemma, and through T-tubules which triggers release of stored calcium
- calcium binds with troponin
- causes a change in shape of troponin, and tropomyosin moves
- myosin head attaches and pulls the actin filament toward the center of the sarcomere
- ATP molecule binds, and myosin head detaches from actin and ATPase splits the ATP molecule, energizing myosin head.
Concentric muscle action
when the amount of force produced by a muscle is greater than the external resistance acting in the opposite direction
Eccentric muscle action
When the amount of force produced by a muscle is less than an opposing external resistance, and muscle lengthens even as it attempts to shorten
Isometric (static) muscle action
when force of muscle and external resistance are equal. The muscle neither shortens or lengthens
DOMS
Delayed-Onset muscle soreness that results from a combination of connective tissue and muscle tissue damage followed by an inflammatory reaction that activates pain receptors.
Oxidative capacity
biochemical property of muscle fibers to produce ATP aerobically. Need fibers that have large and numerous mitochondria and are surrounded by a supply of capillaries
Myoglobin
delivers oxygen from muscle cell membrane to mitochondria
specific tension
fibers may differ in the amount of force they produce relative to their size
Type I muscle fibers
Slow fibers: slow oxidative or slow twitch fibers.
*high oxidative capacity and are fatigue resistant, but they contract and relax slowly
Type IIa
fast oxidative glycolytic (FOG
*moderate oxidative and anaerobic capacity which does allow some fatigue resistance
Type IIx
fast glycolytic (FG) *purely anaerobic and highly fatigable
neurons
most basic unit of the nervous system
*nerve cell
motor neurons
conduct impulses from central nervous system to muscle
sensory or afferent neurons
carry impulses from periphery toward central nervous system
synapse
site of communication between two neurons
*neuromuscular junction is a synapse
Dendrites
projections from neuron cell body that receive the excitatory or inhibitory signals
Muscle spindle
specialized to sense changes in muscle length
- contains intrafusal fibers
- myotatic or streth reflex
Golgi Tendon Organ
protects muscle from injury by sending info to the spinal cord which causes relaxation of the acting muscle and stimulation of the antagonist muscle
Motor unit
all fibers of a single motor unit are of the same muscle fiber type. The different muscle fiber types have distinct anatomical and physiological characteristics which determine their functional capacities
Motor unit recruitment
vary the number of motor units and muscle fibers that are activated.
rate coding
increase the firing rate of motor units already activated
size principle of motor unit recruitment
motor units are recruited in a specific order.
First, type 1 is recruited, followed by IIa and then IIx.
Training allows more units to be recruited!
Skeletal System
206 bones
axial: skull, vertebral column, sternum and ribs
appendicular: upper and lower limbs,
Osteoclasts
breakdown bone
Osteoblasts
simulate bone synthesis
Cortical
compact bone
hard and dense found in outer layers of the shafts of the long bones
Cancellous
trabecular bone
spongy bone, found in the interior area of long bones, the vertebrae, and head of the femur.
*Site of hematopoiesis, synthesis of blood cells
Osteoporosis
weakening of bones
exercise and nutrition can help!
Wolff’s law
bone will adapt in response to stresses placed on it
ex: running will increase bone density
Tendons
Connect muscle to bone
Ligaments
connect bones to bone
formed from collagen and elastin
