Exam 3: Chapter 12 Flashcards
how is skeletal muscle attached to the bone?
through tendons and connective tissue made of collagen
what is the origin?
end of muscle closest to the trunk (bone)
-immobile
what is the insertion?
distal attachment site
-mobile
what are muscle fibers?
-long, cylindrical
-multi-nucleated
-enclosed in connective tissue
-groups together w/ adjacent muscle fibers called fascicles
what two things make up a muscle?
fiber -> fascicle -> muscle
what is the sarcolemma?
membrane of muscle fiber
what is the sarcoplasm?
cytoplasm of muscle fiber
what is the sarcoplasmic reticulum?
modified smooth ER in muscle fiber
-stores Ca2+
what are myofibrils?
contractile, elastic proteins
-contains sarcomeres
what is the sarcomere?
repeating units, makes muscle striated
what is myosin?
thick filament
-contains a heavy chain and light chaing
-ATPase activity
-has an actin binding site
what are the heavy and light chains of myosin?
heavy: myosin heads, elastic hinge, tail
light: wraps around heads
what is actin?
thin filament
-contains troponin & tropomyosin
-has a myosin binding site
what makes up actin?
G-actin -> F-actin -> 2 F-actins wound together
what are T-tubules?
cavity inside the sarcolemma, close to SR
what are Z-disks?
two of them are present in the sarcomere
-zig-zag shape
-attachment site for actin
what are I-bands?
spans into the next sarcomere
-ACTIN ONLY
-where there is no overlap of myosin
what is the A-band?
entire length of myosin
what is the H-zone?
MYOSIN ONLY
-where there is no overlap of actin
what is the M-line?
middle of H-zone
-attachment for myosin
what is titin?
elastic stretchy fiber
-Z-disk -> M-line
-stabilizes contractile fibers
what is nebulin?
inelastic fiber
-attaches at Z-disk
-stabilizes actin
what are the three main things that happen for muscle contraction?
-neuromuscular junction
-excitation-contraction coupling
-contraction-relaxation cycle
what are the steps at the neuromuscular junction?
- AP goes along a somatic motor neuron
- voltage-gated Ca2+ channels open in axon terminal
- Ca2+ enters & causes exocytosis of vesicles with ACh
- ACh released into neuromuscular junction & binds to nicotinic receptors
- cation ion channels open in sarcolemma, leads to Na+ net entry
what are the steps during excitation-contraction coupling?
- muscle depolarizes & AP travels along sarcolemma
- AP enters T-tubule
- DHP receptors are activated on T-tubule & changes conformation
- opens RyR channels in SR
- Ca2+ is released into sarcoplasm
- Ca2+ bins troponin
- POWERSTROKE
what are the steps during the contraction-relaxation cycle?
- actin & myosin crossbridge forms due to powerstroke
- actin & myosin slide past eachother (I-bands & H-zone get smaller)
- overall sarcomere shortens & muscle contracts
- Ca2+ ATPase pumps Ca2+ back into SR
- tropomyosin covers up myosin binding site
- ACh is degraded or diffuses away
what are the powerstroke steps (crossbridge formation)?
- myosin is bound tightly to actin during rigor state (lots of ATP present)
- ATP binds to myosin, myosin releases actin
- myosin hydrolyzes ATP (ADP + Pi)
- myosin head rotates into the crocked & ready position
- Ca2+ signal causes the myosin head to do its powerstroke swivel, Pi is released
- ADP is released from myosin head once powerstroke is complete
- back to rigor state
what is a twitch?
once cycle of contraction-relaxation
-AP from somatic motor neuron -> AP along skeletal muscle fiber -> TWITCH
what is the latent period?
delay b/w AP skeletal muscle and twitch
-time it takes for Ca2+ signal to bind troponin, tropomyosin to move, and form a crossbridge
what are the three sources of ATP for skeletal muscle contraction?
Phosphocreatine
Oxidative Phosphorylation
Anaerobic glycolysis
how does phosphocreatine make ATP?
donates its phosphate to ADP to make ATP (reversible)
-limited supply but makes ATP the quickest
how does oxidative phosphorylation make ATP?
steps of aerobic respiration (glycolysis, CAC, ETC)
-gives the most ATP (1 glucose = 30 ATP)
how does anaerobic glycolysis make ATP?
when O2 is low, 1 glucose = 2 ATP
-unable to exercise long
what is fatigue?
muscle is no longer able to generate or sustain expected power output (not due to lack of ATP)
-Central and Peripheral
what is central fatigue?
psychological (motor cortex) & feeling of wanting to give up
-protective reflexes
-occurs before physiological fatigue
what is peripheral fatigue?
changes that occur from the neuromuscular junction -> myofibrils
what are the speeds Ca2+ ATPase activity and ATP hydrolysis of type 1, 2A, & 2X muscle fibers?
slow-twitch (1): slowest!
oxidative-glycolytic (2A): fast
glycolytic (2X): fast
what are the diameters of type 1, 2A, & 2X muscle fibers?
slow twitch (1): smallest
oxidative-glycolytic (2A): medium
glycolytic (2X): large
what is the duration of time for contraction in type 1, 2A, & 2X muscle fibers?
slow twitch (1): long
oxidative-glycolytic (2A): short
glycolytic (2X): short
what are the levels of capillaries, mitochondria, and myoglobin (O2 storage) for type 1, 2A, & 2X muscle fibers?
slow twitch (1): highest level (dark red)
oxidative-glycolytic (2A): intermediate level (red)
glycolytic (2X): lowest level (pale)
what is the development of tension of type 1, 2A, & 2X muscle fibers?
slow twitch (1): slow
oxidative-glycolytic (2A): intermediate
glycolytic (2X): fast
are type 1, 2A, & 2X muscle fibers fatigue resistant?
slow twitch (1): fatigue resistant
oxidative-glycolytic (2A): fatigue resistant
glycolytic (2X): easily fatigued
what type of metabolism do type 1, 2A, & 2X muscle fibers have?
slow twitch (1): aerobic
oxidative-glycolytic (2A): both aerobic and anaerobic
glycolytic (2X): anaerobic
what are examples of each of the type 1, 2A, & 2X muscle fibers?
slow twitch (1): posture (most used)
oxidative-glycolytic (2A): standing, walking
glycolytic (2X): jumping, sprinting (least used)
what are three things that can impact tension?
sarcomere length
motor unit recruitment
AP frequency
how does sarcomere length impact tension?
must be optimal length (too short or long = little tension)
-resting length is optimal to generate optimal tension
how does motor unit recruitment impact tension?
depends on amount of units activated & type
-more units = more tension
-body regulates!!
what are the motor units for fine movements?
more units with fewer fibers per neuron
what are the motor units for gross movements?
fewer units with more fibers per neuron
do fast units or slow units have more tension?
fast units
what is recruitment of motor units?
process of activating motor units
what is asynchronous recruitment of motor units?
activating different motor units at different times
-allows for longer tension and lessen fatigue
how does AP frequency impact tension?
twitches summate due to increased AP frequency
-releases more Ca2+ = more crossbridges = more tension
-doesn’t allow the muscle to fully relax
what is tetanus?
when maximal tension is reached
-unfused & fused
what is unfused / incomplete tetanus?
little bit of relaxation b/w AP’s
what is fused / complete tetanus?
no relaxation, highest level of summation
what is an isotonic contraction?
creates force & moves a load (movement)
-concentric = muscle shortens (flexion)
-eccentric = muscle lengthens (extension)
what is an isometric contraction?
creates force w/o movement
-muscle remains same length
-EX: plank, holding weights stationary
what is a lever?
rigid rod that pivots around a fulcrum
-BONE
what is a fulcrum?
pivoting point
-JOINT
what is the load-velocity relationship?
speed of contraction (velocity) decreases as load increases
what are the six locations of smooth muscle?
vascular, GI, urinary, respiratory, reproductive, ocular
what are the two contraction patterns of smooth muscle?
Phasic: no contraction -> contraction-relaxation pattern
Tonic: always some level of contraction / tension
what is single-unit communication?
gap junctions, electrical signal, contract as a unit
-majority!
what is multi-unit contraction?
each unit functions independently, no gap junctions
do smooth muscles contract and relax slower or faster than skeletal muscle?
slower
-slowest twitch time
what does actin attach to instead of Z-disks in smooth muscle?
dense bodies
what is the contraction pathway for smooth muscle?
- AP is generated from autonomic NS, a hormone, a paracrine, or stretch in the plasma MB
- Ca2+ channels open, Ca2+ enters from ECF
- causes Ca2+ release from SR
- Ca2+ binds calmodulin
- Ca2+ / calmodulin complex activates myosin light chain kinase
- MLCK phosphorylates myosin light chains
- crossbridge forms & powerstroke cycle occurs (moves dense bodies)
- smooth muscle contracts
what is the relaxation pathway for smooth muscle?
- Ca2+ ATPase pumps Ca2+ back into ECF and SR
- Myosin light chain phosphatase (MLCP) dephosphorylates myosin heads
what happens to contraction when there is high amounts of MLCP in the cell
takes more of Ca2+ to get same force of contraction
-decreased sensitivity to Ca2+
what happens to contraction when there is low amounts of MLCP in the cell?
takes less Ca2+ to get same force of contraction
-increases sensitivity to Ca2+
what is pharmacomechanical coupling?
initiates Ca2+ release to contract the smooth muscle w/o changing MB potential
-uses a chemical signal (hormones, paracrines, NTs)
-no AP generated
what are the two ways Ca2+ is released from the SR?
Ca2+ induced Ca2+ release
-Ca2+ from ECF opens RyR channels on SR
IP3 mediated Ca2+ release
-IP3 opens RyR channels
what are the three ways ECF Ca2+ entry is initiated?
Voltage-gated Ca2+ channels in MB
-opens due to depolarization
Ligand Ca2+ channels (NT, hormone, paracrine)
Stretch activated Ca2+ channels
-as vessels stretch, they do myogenic contraction
-causes a mechanical release of Ca2+
what are two types of unstable MB potentials in smooth muscles?
slow wave potentials
-resting MB varies, can depolarize & repolarize but doesn’t always reach threshold
pacemaker potentials
-autorhythmic, always reaches threshold
how do alpha receptors impact smooth muscle?
contraction!
-IP3 pathways (GPCR)
-sympathetic
how do beta receptors impact smooth muscle?
relaxes!
-cAMP pathways
-bronchioles & cardiac tissue
-sympathetic
how does histamine impact smooth muscle?
constricts bronchioles
how does NO impact smooth muscle?
relaxes vascular smooth muscle
which of the three types of muscle, lacks sacromeres?
smooth muscle
which of the three types of muscle, is striated?
skeletal & cardiac
what is the tissue morphology of the three types of muscles?
skeletal: multinucleate, long & cylindrical
smooth: uninucleate, spindle shaped
cardiac: uninucleate, branching
which of the three types of muscle only contains tropomyosin and lacks troponin?
smooth muscle
what does Ca2+ for each of the three types of muscle bind to?
skeletal: troponin
smooth: calmodulin
cardiac: troponin
where does Ca2+ come from for each of the three types of muscles?
skeletal: SR
smooth: ECF & SR
cardiac: ECF & SR
what is the contraction speed for each of the three types of muscles?
skeletal: fast
smooth: slow
cardiac: intermediate
what initiates contractions for each of the three types of muscles?
skeletal: ACh
smooth: stretch, chemical, autorhythmic
cardiac: autorhythmic
what hormones influence each of the three types of muscles?
skeletal: none
smooth: multiple hormones
cardiac: epinephrine
