Muscle Flashcards
Three types of muscles
- skeletal
- cardiac
- smooth
Step 1 of muscular contraction
-nerve stimulation
Step 2 of muscular contraction
-action potential
Action potential
an electrical current that must be generated in the sarcolemma
Step 3
Action must be propegated along sarcolemma
Step 4
intracellular Ca2+ levels must rise briefly
What ACH
-acetycholine, which is the neurotransmitter at neuromuscular junction
Four main characteristics of muscle
- elasticity
- excitability
- elasticity
- contractility
Excitability
ability to receive and respond to a stimuli
Extensability
Ability to be stretched
Elasticity
ability to recoil after stretched
Contractility
ability to shorten forcibly when stimulated
Four movement functions of muscle
- produce movement
- stabalize joints
- generate heat
- maintain posture
Three features of skeletal muscle
- nerve and blood supply
- connective tissue sheaths
- attachments
Sarcolemma
muscle fiber plasma membrane
Sarcoplasm
muscle fiber cytoplasm
Modified organelles
- myofibrils
- sarcoplasm
- t tubules
Myofibrils
- densely packed rod like elements
- account for 80% of the muscle cell volume
Myofibril features
- stirations
- sarcomeres
- myofilaments
- molecular composition of myofilaments
Sarcomere
- smallest contractile unit
- individual sarcomere align end to end and along myofibril, like boxcars of a train
Myofilaments
orderly arrangment of myosin and actin myofilaments within sarcomere
Actin myofilaments
-thin filaments
Myosin filaments
-thick filaments
Molecular composition of thick filaments
- composed of the protein myosin
- during contraction, heads link thin and thick filaments together forming crossbridge
Molecular composition of thin filaments
-composed of protein actin
Troponin and tropomyosin
-regulatory proteins bound to actin
Elastic filament
composed of protein called titin
Titin
- holds thick filaments in place
- helps recoil after stretch
Sarcoplasmic reticulum
- network of smooth endoplasmic reticulum
- functions in regulation of intracellular Ca2+
- stores and releases Ca2+
T-tubules
- tube formed by protusion of sarcolemma deep into cell interior
- increases muscle fiber surface area
- allows electrical signal to reach deep into cell interior of each muscle finer
Sliding filament model of contraction
states that during contraction, thin filaments slide past thick filaments, causing actin and myosin to overlap more
contraction
the activation of cross bridges generate force
How are bridges made possible?
because of calcium release in the sarcoplasmic retiulum
depolarization
reduction of negative membrane potential
Polarization
movement of the membrane potential to the initial resting state
Excitation contraction coupling E-C
-events that transmit AP along sarcolemma (excitation) are coupled to sliding of myofilaments (contraction)
Step 1 of crossbridge cycle
- cross bridge formation
- high energy
Step 2 of crossbridge cycle
Working (power) stroke: myosin head pivots and pulls thin filament towards m line
Step 3 of cross bridge cycle
cross bridge development: ATP attaches yo myosin head, causing cross bridge detach
Step 4 of cross bridge cycle
cocking of myosin head, energy from hydrolysis of ATP “cocks” myosin head into high energy state
Creatine phosphate
Ca2+ re entry into SR-tension declines to zero
Glycolysis
first step in breakdown of glucose
3 factors of glycolysis
- does not require oxygen
- glucose is broken down into 2 pyruvic acid molecules
- 2 ATP’s are generated for each glucose
