Ch 11 - Musckuloskeletal Flashcards
1
Q
Skeletal muscle
A
- voluntary movements, somatic NS
- sarcomeres - actin and myosin repeating units
- striated
- multinucleated
- Red fibers aka slow twitch fibers - high myoglobin content, aerobic primarily
- myoglobin - O2 carrier, red color
- mitochondria for oxidative phosphorylation
- muscles that contract slowly but dont fatigue (posture support)
- White fibers aka fast twitch fibers - low myoglobin
- contract rapidly and fatigue quickly
2
Q
Smooth Muscle
A
- involuntary action, autonomic NS
- single nucleus
- actin and myosin, NO striations
- more sustained contractions
- tonus - constant low level of contraction
- myogenic activity - contraction without NS input
3
Q
Cardiac Muscle
A
- uninucleated AND may have 2 nuclei
- involuntary, autonomic NS
- striated
- connected by intercalated discs with gap junctions
- connect cytoplasm and allow flow of ions to coordinate depolarization and contraction
- myogenic activity - does not require NS input
- SA node, AV node, bundle of His, purkinje fibers
- Vagus nerve - parasympathetic input to slow HR
- Norepi from sympathetic to increase HR
- Epi from adrenal medulla to increase HR, increases Ca2+ levels
4
Q
Sarcomere
A
- contractile unit of skeletal muscle
- myosin - make thick filaments
- actin - make thin filaments
- tropinin and tropomyosin - proteins that are involved in contraction
- titin - anchors actin and myosin together, prevent stretching
- Z line - boundary of sarcomere
- M line - center of sarcomere, middle of myosin
- I band - only thin filament
- H band - only thick filament
- A band - whole thick filament and overlap of thin filament
- All band sizes change except A band when contraction occurs
5
Q
Structure of Myocytes
A
- Sarcomeres are end to end to make myofibrils
- sarcoplasmic reticulum surrounds the myofibrils
- sarcoplasm - just outside of sarcoplasmic reticulum
- sarcolemma - cell membrane of the myocyte, propogates action potential to all sarcomeres
- uses transverse tubules (T - tubules) that are perpendicular to myofibrils
- myocytes are analogous to muscle fibers
- many sarcomeres in a myofibril many myofibrils in a fiber many muscle fibers (myocytes) make up a muscle
6
Q
initiation of muscle contraction
A
- motor neuron to the neuromuscular junction
- at nerve terminal (synaptic bouton) Ach is released into synapse
- called motor end plate when occurs at neuromuscular junction
- motor unit - nerve terminal and myocytes under its control
- Ach binds to sarcolemma and depolarization occurs
- at nerve terminal (synaptic bouton) Ach is released into synapse
-
action potential down sarcolemma to T - tubules
- into muscle tissue to sarcoplasmic reticulum
- Ca 2+ released
- Ca2+ binds to troponin
- conformational change of tropomyosin
- expose myosin binding sites on actin
7
Q
Shortening of Sarcomere
A
- myosin heads move and bind to sites on actin
- actin-myosin cross bridges allow myosin to pull
- actin toward M line and shorten sarcomere
- Myosin with ADP and P bind to myosin binding site on actin
- release ADP and P to provide energy and actin slides over myosin
- ATP binds myosin head and release from actin
- hydrolized to ADP and P
- recock myosin head
- Sliding filament model
- ATP required for releasing myosin head, hydrolysis not required for powerstroke
8
Q
Relaxation of Sarcomere
A
- acetylcholinesterase degrades Ach in the synapse
- sarcolemma repolarizes
- SR uptake Ca2+ from sarcoplasm
- myosin binding sites covered by tropomyosin
9
Q
Muscle response and strength
A
- Nerves control force by number of motor units recruited, NOT by strength of stimuli to single nerve
- all or nothing response from nerve
- action potentials are all or nothing
10
Q
simple twitch
A
- single muscle fiber response
- latent period - time between reaching threshold and the onset of contraction
- Ca2+ must build up and be released from SR
11
Q
Summation and Tetanus in Muscles
A
- frequency summation - contractions combine, stronger and prolonged
- due to frequent and prolonged stimulation
- tetanus - muscle unable to relax due to frequent stimulation
12
Q
Oxygen Debt and Muscle Fatigue
A
- Creatine phosphate - transfers P from ATP to creatine at times of rest
- reversed in times of need
- creatine + ATP = creatine phosphate + ADP
- myoglobin in muscles used as O2 storage
- lactic acid produced in anerobic conditions
- oxygen debt - difference in amount of oxygen needed by muscles and actual amount present
- also equal to amount of oxygen required to recover from exercise
13
Q
Axial and Appendicular Skeleton
A
- axial - skull, spine, ribs, hyoid
- appendicular - limbs, pectoral girdle (scapula, clavicle), pelvis
14
Q
Bone composition
A
- compact bone
- spongy/cancellous bone
- trabeculae - lattice structure in spongy bone
- bone marrow - between lattice structure
- red marrow - hematopoietic cells
- yellow marrow - fat
- epiphysis - ends
- epiphyseal plate
- diaphysis - long shaft
- periosteum - fibrous sheath around bone, muscle attachment
15
Q
Microscopic Bone
A
- bone matrix - collagen, glycoproteins, peptides, calcium, phosphate, hydroxide ions
- form hydroxyapatite crystals
- osteons - polymer unit of bone
- compose the Haversian system
- lamellae are concentric circles that surround a channel
- Haversian canals - longitudinal channels
- Volkmann’s canals - transverse channels, connect Haversian canals
- Both canals contain - blood vessels, nerve fibers, lymph vessels
- Lacunae - house osteocytes between lamellae rings
- exchange with canals using canaliculi
