Ch 10 Muscle Phsiology Flashcards
Triad
Terminal cisternae(2) + T Tubule
Terminal cisternae
Infoldings of SR run perpendicular to the myofibrils
Triad works as
A voltage sensor for the muscle fiber
Sarcomere
Functional unit, approx. 10,000 sarcomeres in one myofibril,
Myofilaments
Thick and thin
Thin filaments
Composed of actin protein, toward ends of the sarcomere
Thick filaments
Composed of myosin protein, toward the middle of the sarcoma
M line
Middle, where thick filaments interconnect
Z line
Zig zag proteins actinin at ends of sarcomere
A band
Dark in appearance, thick filaments, includes zone of overlap
J band
Light in appearance, where thin filaments are- include Z line
H zone
No overlap between thin and thick
Thin filaments
- composed of twisted actin protein
- active sites along chain
- A rest, tropomyosin covers the active site to prevent binding
- tropinin- sits atop tropomyosin to ensure active site covering
Thick filaments
Composed of myosin proteins
Consists of a head and tail
The heads point away from M line
Forming a crossbridge
1st step in a muscle contraction
Ca+2 ion released by terminal cisternae
2nd step of a muscle contraction
Ca2+ attached to tropinin
3rd step of muscle contraction
Tropinin-tropomyosin complex swings away from the actin is exposed
5th step
Myosin heads attach to active site cross bridge forms
6th step
Myosin pivots, pulling the actin toward the M line
7th step
Myosin detaches and thin slides back into place
Summary of muscle contraction
Attach Cross-bridge Pivot Detach Return
Rigor Mortis
Rigidity of death
What is rigor Mortis
After seat, cell membranes become leaky, so Ca2+ leaks of SR. Myosin heads attah to actin, but no ATP is being made, so can’t detach
When does rigor Mortis begin
3/4 hours after death and muscles remain stuff for 15-24 hours
What happens 24 hours later?
Lysozyme will destroy all cross-bridge
NMJ=
Neuromuscular junction
Where is NMJ located
Connection between a motor neuron and muscle fiber exists
Synaptic cleft
Small gap between the cells
Acetylcholine
Communication between the cells occurs through a chemical neurotransmitter
Where is ACH stored?
Neuron in synaptic vesicles
Motorend plate
Has ACH receptors
1st step that occurs at NMJ
Action potential arrives at end of motor neuron
2nd step at NMJ
ACH released from synaptic vehicle by exocytosis
3rd steps that occurs at NMJ
ACH wanders through synaptic cleft
Step of 5 of NMJ
Influx of NA+ ions from extra cellular fluid across the servile a
Step 6 NMJ
Muscle a.p. Generated along t tubule
Step 7 of NMJ
Ca2+ ions released from t cisternae as a.p. Passes
Step 8 of NMJ
Contraction begins, A chase breaks down ACH bound to motor end plate receptors
step 9 NMJ A
ACH receptors occurs at motor neuron
Black widow venom
Blocks a.p. From neuron
Tetanus
40%-60% mortality rate “lock jaw”
Botulinus toxin
Blocks exocytosis of ACH, Botox injections
Myasthenia gravis
Loss of ACH receptors at m.e.p. Genetic tendency with autoimmune response
Curare
Plant toxin poison darts used by South American tribes, binds to ACH receptors, blocking the real ACH FROM BINDING
Tension
The amount of force exerted by the myosin head
Minimal tension
Initial stimulation causes only the myosin heads in the zone of overlap to attach
Twitch
One contraction once relaxation
Latent phase
A.p. Process sarcolemma, ca2+ ions released
Contraction phase
Ca2+ binds active sites exposed myosin heads bind
Recovery phase
Ca2+ re absorbed active sites covered
Twitch
Single contraction
Summation of twitches
Repeated stimulation. After contraction.
Incomplete tetanus
Rapid stimulation with partial relaxation can occur
Tone
Number of myosin heads that are blind to actin at a given time
Active muscles use..
600 trillion ATP molecules
Where does ATP come from?
ATP styles in muscle
Creatine phosphate
Glycogen
Aerobic respiration
Remember Kreb’s or Citric acid cycle
Anaerobic
Fermentation yields 2 ATP
When muscle becomes active, co reduced back to ATP
Creative phosphokinase
Lack of energy
Seen in long distance runners. Use ATP at slow rate, below normal rate of ATP generation, so they get endurance. Muscles fatigue when they run out of glycogen reserves. pH lowers
Build-iPod lactic acid
Seen in sprinters. Acid build up during recovery period from contraction. PH lowers
Intermediate muscle fiber
Most skeletal muscles are a combo of fast and slow fibers
Can morph to fast or slow with training
Duchenne muscular dystrophy
Sex-linked genetic disease
Muscle cells lacking dystrophin protein
Dystrophin anchors thin filaments to sarcolemma, and regulates channels in sarcolemma
Muscle fiber degenerate into fatty tissue
Atrophy
When muscle wastes away becoming smaller and weaker
Disuse atrophy
Reduced number of nerve impulses, reversible. Ex bedridden, casts
Degeneration atrophy
No nerve impulses to muscle at all. After 2 years irreversible. Muscle tissue will turn into fibrous c.t.
Hypertrophy
Increased diameter of muscle fibers, increased number of mitochondria, myofibrils, Sr… Reversible
Acetylcholine: acetylcholinesterase
Neurotransmitter: enzyme that breaks down the ACH
Action potential: nerve impulse
Action p. Releases neurotransmitters : nerve impulse may not be strong enough to be turned into a.p.
T. Tubule: terminal cisternae
A.p. Travels through here: Ca ions stores here. Together the traid works as a voltage sensor for muscle cell
How would a drug interferes with cross bridge formation affect contraction?
Yes- no contraction occurs, you are paralyzed
What would you expect to happen in resting skeletal muscle if the sarcolemma suddenly became very permeable to ca2+ ions
Sudden violent contraction, like a charley horse
Predict what would happen to a muscle if he motor end plate did not contain acetyl cholinesterase
Muscle would contract one time only- could not be re-stimulated to contact a second time
3 factors that are responsible for duration of muscle contraction
How long stimulation lasts at NMJ
Presence of Ca ions in the sarcoplasm
Availability of ATP
Can a skeltal muscle contract without shortening?
Yes- isometric contraction has occured
Tension rises to peak levels with very brief periods of relaxation
Incomplete tetanus
One contraction one compete relaxation
Twitch
Slightly higher tension results as a string of successive stimuli are received
Summation
Stimulus frequency is so rapid that relaxation is completely eliminated
Complete tetanus
How does a body sustain contractions?
Larger muscles like those of the back are controlled by more than one motor unit. Motor units are rotated so that some parts of the muscle are resting while other parts of the muscle are contracting. This results in a sustained contraction without fatigue of the overall muscle
Acetylcholine
Contraction
Acetylcholinesterase
Paralysis
Anticholinesterase
Contraction
Curare
Paralysis
Botulin toxin
Paralysis
Tetanus infection
Paralysis
Polio infection
Paralysis
The type of contraction in which tension rises, but resistance does not change is?
Isometric contraction
An action potential can travel quickly from one cardiac muscle cell to another due to the presence of?
Intercalated disc
What is a motor unit?
All muscle cells controlled by a single neuron-
What forms of energy reserves do resting skeletal muscle fibers contain
Co, ATP, glycogen
What two mechanisms are used to generate ATP in a muscle cell
Aerobic and anaerobic respiration
Two activities that would require aerobic endurance
Distance sports- cords country and skiing
Two areas of the boy where slow fibers
Eyeballs and muscles of the fingers
Describe the relationship between lactic acid and fatigue
As lactic acid increase, pH of the sarcoplasm drops, enzymes will not work, therefore, muscle is fatigued and can no longer contract until homeostasis is regained
You were orbiting the moon 6 months?
Disuse atrophy
You were in an accident and needed bed rest for 2 months
Disuse atrophy
You have been bulking up by drinking those gross protein shakes with creative
Hypertrophy
What fiber in cheetah
White
Salmon?
Dark
Tilapia
White
Whale
Dark
Seal
White
Bear
Dark
Gastrocnemius muscle
Dark
Spasm
Sudden contraction of single m. In a larger m. group
Cramp
Painful spasm
Twitch
Single involuntary contraction
Tremor
Rhythmic, repeated contraction, produces shaking
Isometric
Building tension but muscle doesn’t shorten
Isotonic
Build tension and he muscle shortens
