Biology Chapter 11: The Musculoskeletal System Flashcards
Three main types of muscle
skeletal muscle
smooth muscle
cardiac muscle
Skeletal muscle
involved in support and movement, propulsion of blood in the venous system, and thermoregulation. It appears striated, is under voluntary (somatic) control, is polynucleated and can be divided into red fibers and white fibers
Red fibers
slow-twitch fibers that carry out oxidative phosphorylation
White fibers
fast-twitch fibers that rely on anaerobic metabolism
Smooth muscle
the respiratory, reproductive, cardiovascular and digestive systems. It appears nonstriated, is under involuntary (autonomic control and is uninucleated. It can display myogenic activity, or contraction without neural input.
Cardiac muscle
comprised the contractile tissue of the heart, appears striated and is under involuntary (autonomic) control.
- uninucleated
- myogenic activity
- cells are connected with intercalated discs that contain gap junctions.
Sacromere
the basic contractile unit of striated muscle - made of thick (myosin) and thin (actin) filaments
Where are troponin and tropomyosin found?
on the thin filament - they regulated actin myosin interactions
What are the lines, zones and bands of the sacromere?
Z-lines (defines boundaries) M-line (middle) I-band (only thin filaments) H-zone (only thick filaments) A-band (thick filaments in their entirety)
Sacromeres end to end =
myofibrils
Myocyte
Muscle cell/muscle fiber - contains many myofibrils
Sarcoplasmic reticulum
A calcium-containing modified ER that surrounds myofibrils.
Sarcolemma
the cell membrane of myocytes
T-tubules
a system connected to the sarcolemma and oriented perpendicular to the myofibrils, allowing the incoming signal to reach all parts of the muscle.
Where does the muscle contraction begin?
the neuromuscular junction
What are the steps of a muscle contraction
- acetylcholine released at nueromuscular junction - causes depolarization of the sarcolemma
- Depolarization spreads from sarcolemma to the T-tubules, triggering the release of calcium ions.
- Ca binds to troponin, causing a shift in tropomyosin, exposing the myosin-binding site on actin.
- myosin heads bind to actin
- form cross bridges and pull –> contraction
- Muscle relaxes when acetylcholine is degraded.
- ATP binds to myosin head, releases it from actin.
Simple twitch
all or nothing response by muscle cells
Frequency stimulation
addition of multiple simple twitches before the muscle has an opportunity to relax.
Tetanus
simple twitches that occur so frequently as to not let the muscle relax at all – a more prolonged and stronger contraction.
oxygen debt
the difference between the amount of oxygen needed and the amount present
What are two ways muscle cells can reduce oxygen debt?
- 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
endoskeletons (like in humans)
External skeletons
exoskeletons (like those in arthopods
what are the two divisions of the skeletal system?
Axial (midline, such as skull, vertebrae, ribcage, etc.)
Appendicular (all other, including pelvis)
What is bone derived from?
mesoderm
What are the two types of bone?
compact and spongy or cancellous bone.
What is the main structure of the spongy bone?
trabeculae - lattice-like structure
What are the cavities of bone filled with?
bone marrow
What are the three parts of the bone from middle to the outside?
diaphyses - long bone shafts
metaphyses
Epiphyses - contain an epiphyseal (growth) plate that causes linear growth of the bone
Periosteum
Layer of connective tissue that surrounds bone
Tendons
Attaches bones to muscles
Ligaments
attach bones to other bones
Lamellae
concentric rings that bones are organized into
Haversian or Volkmann’s canal
central canal in bones
Structural unit of bones
osteon
Lacunae
space between lamellar rings where osteocytes reside - connected with canaliculi to allow for nutrient and waste transfer.
Osteoblasts
build bone
Osteoclasts
resorb bone
Parathyroid hormone
increases resorption of bone, increasing calcium and phosphate concentrations in the blood.
Vitamin D
increases resorption of the bone, leading to increased turnover and subsequently, the production of stronger bone.
Calcitonin
increases bone formation, decreasing calcium concentrations in the blood.
Cartilage
a firm elastic material secreted by chondrocytes
- matrix is called chondrin
- usually found in areas that require more flexibility or cushioning.
- avascular and not innervated
How do bones form in fetal life?
endochondral ossification. Some bones, especially of the skull, form directly from undifferentiated tissue (mesenchyme) in intramembranous ossification.
Immovable joints
fused together to form sutures or similar fibrous joints.
Movable joints
usually strengthened by ligaments and contrain a synovial capsule.
Synovial fluid
secreted by synovium, aids in motion by lubricating the joint.
Articular cartilage
coats bones in joints to aid in movement and provide cushioning.
Antagonistic pairs
muscles that serve opposite functions - when one contracts, the other lengthens.
