Biology Chapter 11: The Musculoskeletal System (2 Stars) Flashcards
There are three main types of muscle: skeletal muscle, smooth muscle, and _____ muscle.
cardiac
Skeletal muscle is involved in support and movement, propulsion of blood in the venous system, and thermoregulation. It appears striated, is under voluntary (somatic) control, is _______, and can be divided into red (slow-twitch) fibers that carry out oxidative phosphorylation and white (fast-twitch) fibers that rely on anaerobic metabolism.
polynucleated
Smooth muscle is in the respiratory, reproductive, cardiovascular, and digestive systems. It appears ______, is under involuntary (autonomic) control, and is uninucleated. It can display myogenic activity, or contraction without neural input.
nonstriated
Cardiac muscle comprises the contractile tissue of the heart. It appears striated, is under involuntary (autonomic) control, and is uninucleated (sometimes binucleated). It can also display myogenic activity. Cells are connected with intercalated discs that contain _______
gap junctions
The ______ is the basic contractile unit of striated muscle.
sarcomere
Sarcomeres are made of thick (_____) and thin (____) filaments.
(myosin)
actin
____ and tropomyosin are found on the thin filament and regulate actin–myosin interactions.
Troponin
The _______ can be divided into different lines, zones, and bands.
sarcomere
The boundaries of each sarcomere are defined by _______
Z-lines.
The _____ is located in the middle of the sarcomere.
M-line
The I-band contains only ____ filaments.
thin filaments.
The _____ consists of only thick filaments.
H-zone
The _____ contains the thick filaments in their entirety. It is the only part of the sarcomere that maintains a constant size during contraction.
A-band
Sarcomeres attach end-to-end to become myofibrils, and each myocyte (muscle cell or muscle fiber) contains many ______
myofibrils.
Myofibrils are surrounded by the______ , a calcium containing modified endoplasmic reticulum, and the cell membrane of a myocyte is known as the sarcolemma.
sarcoplasmic reticulum
A system of ______ is connected to the sarcolemma and oriented perpendicularly to the myofibrils, allowing the incoming signal to reach all parts of the muscle.
T-tubules
Muscle contraction begins at the ______ , where the motor neuron releases acetylcholine that binds to receptors on the sarcolemma, causing depolarization.
neuromuscular junction
This depolarization spreads down the sarcolemma to the _______, triggering the release of calcium ions.
T-tubules
____ binds to troponin, causing a shift in tropomyosin and exposure of the myosin-binding sites on the actin thin filament.
Calcium
Shortening of the sarcomere occurs as _____ heads bind to the exposed sites on ____, forming cross bridges and pulling the actin filament along the thick filament, resulting in contraction. This is known as the sliding filament model.
myosin heads
actin
The muscle relaxes when ______ is degraded by acetylcholinesterase, terminating the signal and allowing calcium to be brought back into the SR. ATP binds to the myosin head, allowing it to release from actin.
acetylcholine
Muscle cells exhibit an all-or-nothing response called a ________
simple twitch.
Addition of multiple simple twitches before the muscle has an opportunity to fully relax is called _______
frequency summation.
______ that occur so frequently as to not let the muscle relax at all can lead to tetanus, a more prolonged and stronger contraction.
Simple twitches
_____ have additional energy reserves to reduce oxygen debt (the difference between the amount of oxygen needed and the amount present) and forestall fatigue.
Muscle cells
__________ can transfer a phosphate group to ADP, forming ATP.
Creatine phosphate
______ is a heme-containing protein that is a muscular oxygen reserve.
Myoglobin
Internal skeletons (like those in humans) are called ______; external skeletons (like those in arthropods) are called exoskeletons.
endoskeletons
The human skeletal system can be divided into_____ and _________
axial and appendicular skeletons.
The ______ skeleton consists of structures in the midline such as the skull, vertebral column, ribcage, and hyoid bone.
axial
The ______ skeleton consists of the bones of the limbs, the pectoral girdle, and the pelvis.
appendicular
Bone is derived from embryonic ______ and includes both compact and spongy (cancellous) types.
mesoderm
Compact bone provides strength and is _____
dense.
Spongy or cancellous bone has a lattice-like structure consisting of bony spicules known as _____. The cavities are filled with bone marrow.
trabeculae.
_____ contain shafts called diaphyses that flare to form metaphyses and that terminate in epiphyses. The epiphysis contains an epiphyseal (growth) plate that causes linear growth of the bone.
Long bones
Bone is surrounded by a layer of connective tissue called ______
periosteum.
____ are attached to muscles by tendons and to each other by ligaments.
Bones
______ has both organic components, like collagen, glycoproteins, and other peptides, and inorganic components, like hydroxyapatite.
Bone matrix
Bone is organized into concentric rings called _____ around a central Haversian or Volkmann’s canal. This structural unit is called an osteon or Haversian system.
lamellae
Between lamellar rings are ______, where osteocytes reside, which are connected with canaliculi to allow for nutrient and waste transfer.
lacunae
Bone remodeling is carried out by _____ and osteoclasts.
osteoblasts
Osteoblasts build bone, while osteoclasts resorb bone.
______ increases resorption of bone, increasing calcium and phosphate concentrations in the blood.
Parathyroid hormone
_______ also increases resorption of bone, leading to increased turnover and, subsequently, the production of stronger bone.
Vitamin D
Calcitonin _____ bone formation, decreasing calcium concentrations in the blood.
increases
Cartilage is a firm, elastic material secreted by chondrocytes. Its matrix is called ______
chondrin.
_____ is usually found in areas that require more flexibility or cushioning.
Cartilage
_____ is avascular and is not innervated.
Cartilage
In fetal life, bone forms from cartilage through ______ ossification. Some bones, especially those of the skull, form directly from undifferentiated tissue (mesenchyme) in intramembranous ossification.
endochondral
_____ may be classified as immovable or movable.
Joints
Immovable joints are fused together to form sutures or similar ______ joints.
fibrous
Movable joints are usually strengthened by ligaments and contain a ______ capsule.
synovial
______, secreted by the synovium, aids in motion by lubricating the joint.
Synovial fluid
Each bone in the joint is coated with ______ cartilage to aid in movement and provide cushioning.
articular
Muscles that serve opposite functions come in _______ pairs; when one muscle contracts, the other lengthens
antagonistic
