muscular and skeletal systems Flashcards
Which muscle types are striated
skeletal and cardiac
tendons
attaches muscle to bone
flexing and extending of skeletal muscle
flexing -reducing angle of joint
extending -increasing angle of joint
origin and insertion of skeletal muscle
origin - where muscle attaches
insertion - where muscle attaches on the bone more distant from the center of the body
fascicles
bundles that allow flexibility within the muscle
How many nerves innervate skeletal muscle
skeletal muscle is innervated by a single nerve ending
sarcolemma
cell membrane of myofiber
actin and myosin function
proteins in the myofibril (smallest unit of skeletal muscle)
actin forms thin filaments and myosin forms thick filaments
They overlap in sarcomeres
What occurs during contraction
thin and thick filaments slide across each other, drawing the Z lines of each sarcomere closer together and shortening the length of the muscle cell
myosin function in movement
enzyme that uses ATP energy to create movement, contains a head and tail
contractile cycle steps
- binding of myosin head to myosin binding site on actin. Myosin has ADP and P bound at this point
- power stroke, myosin head moves to low energy conformation and pulls actin chain towards center of sarcomere, releasing ADP
- binding of new ATP molecule necessary for release of actin by myosin head
- ATP hydrolysis occurs and myosin head is set in high energy conformation (cocked)
troponin tropomyosin complex
part of thin filament, prevents contraction when Ca2+ isn’t present
troponin is bound to tropomyosin and can bind Ca2+, causing myosin heads to be able to attach to actin, since tropomyosin is moved out of the way
neuromuscular junction
synapse between an axon terminus and a myofiber
What occurs when ACh binds to its receptor?
A postsynaptic sodium influx causing depolarization, which leads to an end plate potential.
What is required for contraction to occur in the myofibril
Action potential has to depolarize the entire myofiber
transverse tubules
allow action potential to travel in to thick myofibers.
sarcoplasmic reticulum
membrane in the myofiber that releases Ca2+ upon depolarization
How does the nervous system increase force of contraction
motor unit recruitment and frequency summation
length tension relationship
a muscle contracts most forcefully at an optimum length
creatine phosphate function
intermediate term energy storage molecule thats hydrolysis drives regeneration of ATP from ADP + P
myoglobin
provides an oxygen reserve by taking O2 from hemoglobin and then releasing it as needed
cause of rigor mortis
myosin heads are unable to release actin without ATP and the muscle can neither contract nor relax
slow twitch vs fast twitch muscle
slow twitch have a slow speed of contraction and many mitochondria, are very resistant to fatigue
fast twitch includes two types, IIA and IIB. IIB is known as white fast twitch and has very fast contraction, very few mitochondria, and has low fatigue resistance.
how is cardiac muscle similar to skeletal muscle
- thick and thin filaments are organized into sarcomeres, so both cardiac and skeletal muscle are striated
- t tubules are present and serve the same function
- troponin tropomyosin regulates contraction in the same way
- length tension relationship works the same way and is more significant in cardiac muscle
How is cardiac muscle different from skeletal muscle
- muscle cells of the heart are interconnected by gap junctions known as intercalated disks
- some of the calcium required for cardiac muscle cell contraction comes from the extracellular environment
- cardiac muscle contract doesn’t depend on stimulation by motor neurons
- action potential in cardiac muscle depends also on slow voltage gated calcium channels, resulting in the cardiac action potential having a distinctive plateau
How is smooth muscle similar to skeletal muscle
contraction is accomplished blsliding of actin and myosin filaments and the four step contractile cycle is the same
How is smooth muscle different from skeletal muscle
- Smooth muscles are narrower and shorter
- t tubules aren’t needed
- both smooth and cardiac muscle are connected to neighbors by gap junctions
- thick and thin filaments aren’t organized into sarcomeres in smooth muscle
- contraction regulated by calmodulin and myosin light chain kinase
- Smooth muscle relies heavily on extracellular stores of Ca2+ for contraction
- Action potential of smooth muscles is determined by slow channels only
- smooth muscles have a constantly fluctuating resting potential. These slow waves then reach threshold and undergo an action potential
- smooth muscle are innervated by autonomic motor neurons, while skeletal is innervated by somatic motor neurons
role of endoskeleton
- supports body
- provides framework for movement
- protects vital organs
- stores calcium
- hematopoiesis (synthesizing formed elements of the blood)
axial and appendicular endoskeleton
axial consists of the skull, the vertebral column, and the rib cage
all other bones are part of appendicular skeleton
connective tissue
consists of cells and the materials they secrete, derived from fibroblast
loose vs dense connective tissue
loose - packing tissues
dense - contains large amounts of fibers such as tendons, ligaments, cartilage, and bone
flat vs long bones
flat are the location of hematopoiesis and are important for organ protection
long are important for support and movement
red vs yellow marrow
red marrow is found in spongy bone within flat bones and is the site of hematopoiesis
yellow marrow is found in shafts of long bone and is filled with fat and inactive
osteocyte function in compact bone
found in each lacuna
allows cells to exchange nutrients and waste by extending down into canaliculi and contacting other osteocytes through gap junctions
cartilage
strong but very flexible extracellular tissue secreted by cells called chondrocytes
four types of cartilage
hyaline - strong and somewhat flexible
articular - joints lined by hyaline cartilage
elastic cartilage - provides elasticity
fibrous cartilage - very rigid
synovial fluid function
lubricates movable joints
intramembranous ossification
synthesis of bone from an embryonic tissue called mesenchyme
osteoblasts
make bone by laying down collagen and hydroxyapatite
osteoclasts
destroy bone by dissolving hydroxyapatite crystals, stimulated by parathyroid hormone and inhibited by calcitonin
effect of PTH and calcitriol
increase in blood calcium levels
