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MCAT Bio. Ch. 11

Skeletal Muscle Is Involved In: Support and movement, propulsion of blood in the venous system, and thermoregulation.
Skeletal Muscle Appears: Striated, is under voluntary (somatic) control, is polynucleated, and can be divided into red (slow-twitch) fibers that carry out oxidative phosphorylation and white (fast-twitch) fibers that rely on anaerobic metabolism.
Smooth Muscle Is: In the respiratory, reproductive, cardiovascular, and digestive systems.
Smooth Muscle Appears: Nonstriated, is under involuntary (autonomic) control, and is uninucleated. It can display myogenic activity, or contraction without neural input.
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.
Cardiac Muscles Are Connected With: Intercalated discs that contain gap junctions
Sarcomere: The basic contractile unit of striated muscle
Sarcomeres Are made Of: Thick myosin and thin actin filaments
Troponin And Tropomyosin Are Found: On the thin filament and regulate actin-myosin interactions
Boundaries Of Each Sarcomere Are Defined By: Z-lines
The M-Line Is Located In: The center of the sarcomere
The I-band Contains: Only thin filaments
The H-zone Consists Of: Only thick filaments
The A-band Contains: The thick filaments in their entirety. It is the only part of the sarcomere that maintains a constant size during contraction.
Sacromeres Attach End-To-End To Become: Myofibril. Each Myocyte (muscle cell) contains many muscle fibers
System Of T-Tubules Is Connected To The: Sarcolemma and oriented perpendicularly to the myofibrils, allowing the incoming signal to reach all parts of the muscle
Muscle Contraction Begins At The Neuromuscular Junction, Where (Step 1 Of Muscle Contraction): The motor neuron releases acetylcholine that binds to receptors on the sarcolemma, which causes depolarization
Steps 2-3 Of Muscle Contraction: The depolarization spreads down the sarcolemma to the T-tubules, triggering the release of calcium ions. Calcium binds to troponin, causing a shift in tropomyosin and exposure of the myosin-binding sites on the actin thin filament.
Step 4 Of Muscle Contraction Shortening of the sarcomere occurs as myosin heads bind to the exposed sites on actin, forming cross bridges and pulling the actin filament along the thick filament, resulting in contraction. This is called the sliding filament model.
Step 5 Of Muscle Contraction The muscle relaxes when acetylcholine 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.
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.
Simple Twitches That Occur So Frequent To Not Let The Muscle Relax At All Can Lead To: Tetanus, a more prolonged and stronger contraction
Muscle Cells had Additional Energy Reserves To Reduce: Oxygen debt, which is the difference between the amount of oxygen needed and the amount present as well as forestall fatigue
Creatine Phosphate Can Transfer: A phosphate group to ADP, forming ATP
Myoglobin Is A: Heme-containing protein that is a muscular oxygen reserve
Internal Skeletons Are called: Endoskeletons
External Skeletons (Like Those In Arthropods) Are Called: Exoskeletons
Axial Skeleton: Consists of structures in the midline such as the skull, vertebral column, ribcage, and hyoid bone
Appendicular Skeleton: Consists of the bones of the limbs, the pectoral girdle, and the pelvis
Bone Is Derived From: Embryonic mesoderm and includes both compact and spongy (cancellous) types
Compact Bone: Provides strength and is dense
Spongy Or Cancellous Bone Has: A lattice-like structure consisting of bony spicules known as trabeculae. The cavities are filled with bone marrow.
Long Bones 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
Bone Is Surrounded By: A layer of connective tissue called periosteum
Bones Are Attached To Muscles By: Tendons
Bones Are Attached To Each Other By: Ligaments
Bone Matrix Has Both: Organic components like collagen, glycoproteins, and other peptides. It also has inorganic components like hydroxyapatite.
Bone Is Organized Into Concentric Rings Called: Lamellae around a central Haversian or Volkmann's canal. This structural unit is called an osteon or Haversian system.
Between Lamellar Rings Are: Lacunae where osteocytes reside, which are connected with canaliculi to allow for nutrient and waste transfer.
Bone Remodeling Is Carried Out By: Osteoblasts and osteoclasts.
Osteoblasts: Build bone
Osteoclasts: Resorb bone
Parathyroid Hormone: Increases resorption of bone, increasing calcium and phosphate concentrations in the blood
Vitamin D: Also increases resorption of bone, leading to increased turnover and subsequently, the production of stronger bone.
Calcitonin: Increases bone formation, decreasing calcium concentrations in the blood
Cartilage: Is a firm, elastic material secreted by chondrocytes. Its matrix is called chondrin. It is also avascular and is not innervated.
Cartilage Is Usually Found In: Areas that require more flexibility or cushioning.
In Fetal Life, Bone Forms From Cartilage Through: Endochondral ossification
Some Bones, Especially Those Of the Skull, Form Directly From Undifferentiated Tissue (Mesenchyme) In: Intramembranous ossification
Joints May Be Classified As: Immovable or movable
Immovable Joints Are: Fused together to form sutures or similar fibrous joints
Movable Joitns Are Usually Strengthened By: Ligaments and contain a synovial capsule
Synovial Fluid, Which Is Secreted By The Synovium: Aids in motion by lubricating the joint
Each Bone In The Joint Is Coated With: Articular cartilage to aid in movement and provide cushioning
Muscles That Serve Opposite Functions Come In: Antagonistic pairs. When one muscle contracts, the other lengthens.
Created by: SamB91
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