Muscular and skeletal systems Flashcards
endoskeleton
serves as the framework within all vertebrate organisms
cartilage
connective tissues that is softer and more flexible than bone. external ear, nose, wall of the larynx, skeletal joints.
Chronddrocytes
cells responsible for synthesizing cartilage
Bone
mineralized connective tissue with the ability to withstand physical stress
Compact bone
dense bone that does not appear to have any cavities when observed with the naked eye. Osteons, Haversian Canals, lammellae
osteons
the bony matrix is deposited in these structural units
Haversian Canals
central microscopic channel in an osteon
Lamellae
Concentric circles of bony matrix that surround the haversian canal
Spongy Bone
less dense and consists of an interconnecting lattice of bony spicules (trabeculae). space between spicules filled with bone marrow
red marrow
involved in blood cell formation
yellow marrow
inactive and infiltrated by adipose tissue
osteoblasts
synthesize and secrete the organic constituents of the bone matrix. Once they have become surrounded by their matrix they mature into osteocytes
osteoclasts
large, multinucleated cells involved in bone reabsorption, when bone is broken down and minerals are released back into the blood.
Two types of bone formation
endochondral ossification and intramembranous ossification
endochondral ossification
existing cartilage is replaced by bone. Long bones arise from this
intramembrnaous ossification
mesenchymal (embryonic or undifferentiated) connective tissue is transformed into and replaced by bone.
what is the basic framework of the body?
axial skeleton
axial skeleton
skull, vertebral column, rib cage
appendicular skeleton
points of attachment to the axial skeleton. pectoral and pelvic girdles, and bones of the appendages
what holds the joints of the skull together
sutures or immovable joints
What holds different bones together at a joint?
ligaments
Tendons
attach bone to muscles and bend the skeleton at the moveable joint
origin of muscle
the point of attachment of a muscle to a stationary bone. (proximal end)
insertion of muscle
the point of attachment of a muscle to the bone that moves. (distal end in limb muscle)
three types of muscles
skeletal, smooth, cardiac
pyramidal system (muscles)
rapid commands to skeletal muscles and various other organs because there is no intervening synapses.
extrapyramidal system
somatic motor commands as a result of processing performed at the unconscious, involuntary level.
What is responsible for the control of muscle tone?
the red nucleus of the mesencephalon. extrapyramidal
skeletal muscles are innervated by the
somatic nervous system
myofibrils
filaments embedded in the muscle fibers. lots of mitochondria
myofibrils are divided into these contractile units
sarcomeres
sarcoplasmic reticulum
myofibrils are enveloped by this modified endoplasmic reticulum that stores calcium ions.
sarcoplasm
cytoplasm of a muscle fiber
sarcolemma
cell membrane of a muscle fiber. capable of propogating action potentials and is connected to a system of T Tubules oriented perpendicularly to the myofibrils.
The T system of the muscle
provides channels for ion flow throughout the muscle fibers and can also propagate an action potential.
Striated muscle
Skeletal muscle. striations of light and dark bands.
sarcomeres
composed of thin and thick filaments.
What are the thin filaments composed of?
actin
what are the thick filaments composed of?
myosin
Boundaries of a single sarcomere and anchor the thin filaments.
Z line
Runs down the center of the sarcomere
M line
The region containing thick filaments only
H zone
spans the entire length of the thick filaments and any overlapping portions of the thin filament
A band
neuromuscular junction
link between the nerve terminal and the sarcolemma
Contraction
Action potential is generated via depolarization of nerve cell and conducted along the sarcomere and the T system and into the interior of the muscle fiber. Sarcoplasmic reticulum releases Ca ions that initiate the contraction of the sarcomere by binding to troponin C on the actin filaments. Allosteric changes in the protein allow myosin heads to bind to these sites on the actin. Use of energy allows a power stroke to occur, pulling Z bands closer together. Actin and myosin slide past each other and the sarcomere contracts.
rigor mortis
rigidity caused by absense of ATP which is required for the myosin heads to be released from the actin filaments. Rigid for 12-24 hours after death
Isotonic Muscle Contraction
muscle shortens against a fixed load while the tension on that muscle remains constant.
Dynamic muscle contraction
includes both concentric and eccentric types of contraction. Results in the change in length of the muscle with a corresponding change in tension on that muscle
Concentric contraction
dynamic contraction where the muscle fibers shorten and the tension on the muscle increases
eccentric muscle contraction
dynamic contraction where the muscle fiber lengthens and the tension on the muscle increases.
isometric contraction
both ends of the muscle are fixed and no change in length occurs, but tension increases.
Strength of a muscle fiber contraction
Can not be increased, all or none. The strength of the entire muscle contraction can be increased by recruiting more muscle fibers.
simple twitch
response of a single muscle fiber to a brief stimulus at or above the threshold stimulus and consists of a latent period, a contraction period, and a relaxation period.
What happens during the latent period of a simple twitch
Time between the stimulation and the onset of the contraction. Action potential spreads along the sarcolemma and Ca2+ ions are released.
absolute refractory period
muscle is unresponsive to stimulus during this brief relaxation.
Temporal summation
when the fibers of a muscle are exposed to very frequent stimuli, the muscle cannot fully relax. Contractions begin to combine, becoming stronger and more prolonged.
Tetanus
When the contractions from temporal summation become continuous because it is so frequent that the muscle cannot relax. stronger than a simple twitch of a single fiber. Muscle will fatigue and contraction will weaken
Tonus
state of partial contraction
What allows skeletal muscles to continue contracting in the absence of oxygen?
muscles convert glucose to pyruvic acid through glycolysis, Lactic acid is generated when pyruvic acid reacts with the enzyme lactate dehydrogenase. this allows the pyruvate to enter Krebs cycle
Cori Cycle during periods of strenuous activity
converts lactic acid in the liver to glucose for discharge in the blood stream.. Muscles are then able to uses the glucose as an immediate source of energy or to rebuild their glycogen stores.
What is necessary for the creation of ATP during periods of strenuous exercise?
Conversion of glucose to pyruvate in the muscle cells. Does not involve Cori Cycle.
smooth muscle
involuntary. innervated by autonomic NS. digestive tract, bladder, uterus, blood vessels. one centrally located nucleus and lack striations of skeletal muscles
cardiac muscles
heart. characteristics of both smooth and skeletal. actin and myosin filametns are arranged in sarcomeres. striated. one or two centrally located nuclei
Energy reserves
creatine phosphate
myoglobin
Hemoglobin like protein found in muscle tissue. high oxygen affinity and maintains the oxygen supply in muscles by tightly binding to oxygen.
