Chapter 10 Part 2 Flashcards
what does it mean when there is no zone of overlap?
something is broken or torn
what does the number of pivoting cross bridges depend on?
amount of overlap b/w thick and thin filaments
define optimal overlap
produces the most amount of tension
define a twitch
a single neural stimulation to a single muscle cell causes a single contraction/ twitch
what are 3 phases of a twitch
- latent period
- contraction period
- relaxation period
latent period
a few milliseconds b/w the arrival of the nerve signal & the generation; an action potential is generated, travels on t-tubules, Ca2+ release, etc.
contraction phase
sliding filaments model and tension builds to a peak
relaxation phase
active sites get covered; tension falls to resting levels
why is the tension increasing w/ each new signal that arrives?
building up Ca2+ w/ not enough time in between the signals. Ca2+ builds up because they can’t all go back into storage. More Ca2+building= more exposed- active sites = more pivoting cross bridge= more tension
Treppe
a star step increase in twitch tension
wave summation
repeated stimulations before the end of the relaxation period of the twitches
stimulation > 50 ksecond
even less time to pump ca2+ back into storage- tension rising faster
define complete tetanus
smooth, sustained movements; high stimulation= muscle never relaxes, continuous contraction
motor unit
consists of a motor neuron & all the skeletal muscle fibers that it contracts
- all the muscle cells in the motor unit contract at the same time
small motor unit
good for precise movements;
e.g. moving your eyeballs, moving fingertips for surgery
large motor unit
where movements don’t need to be as precise
e.g. calf and back
recruitment
activating additional motor units to make a muscle contraction
Muscle tone
the normal tension & firmness of a muscle cell at rest
effect on increasing muscle tone on metabolism during rest
increases it
Isotonic contraction
muscle length changes; usual muscle contraction
concentric contraction
muscle get shorter
tension in muscle> resistance
eccentric contraction
muscle get longer
describe eccentric contraction
myosin is attached & pivoting
generating tension even though muscle is lengthening
e.g. on the back down in a bicep curl
tension< resistance
define isometric
muscle develops tension but is prevented from changing length
define creatine phosphate
molecule that stores excess energy in resting skeletal muscle cells
Recharging ATP to CP
energy that stored in CP can be used to recharge ADP to ATP through creatine phosphokinase (CPK)
what are the 3 things that occur at peak exertion?
- lack O2 to support mitochondria
- muscles rely on glycolysis for ATP
- Lactic Acid builds up
what are 4 results of muscle fatigue
- depletion of energy reserves (ATP, CP, glycogen)
- low pH of lactic acid; cells w/ low pH–> sick, enzymes don’t work the way they should
- damage to organelles, SR, sarcolemma–> lactic acid
- muscle exhaustion and pain
why does heavy breathing occur even after exercise?
repayment of oxygen debt - after exercise the body needs more O2 then usual to go back to normal levels
How does the cells return back to normal?
restoring supplies of ATP, glycogen and CP
liver breaks down lactic acid
also, homeostasis of bp, blood flow, sweat glands, etc..
define the cori cycle
removal of lactic acid from bloodstream carrying waste products to the liver to be recycled into glucose then it is released back into the blood stream to recharge muscle’s glycogen reserve
how is heat produced or lost?
energy could be lost as heat when one molecule is converted into the other –> 70% is lost to raise body temperature
define power
amount of tension a muscle can produce
define endurance
the amount of time an activity can be sustained
What does power and endurance both depend on?
the type of muscle fiber involved
physical conditioning
3 type of muscle fibers
- fast fibers
- slow fibers
- intermmediate fibers
what are fast fibers
fibers that contract very quickly
e.g. muscles in eyes
characteristics of fast fibers
strong contractions but fatigue quickly
large diameter with large glycogen reserves; usually for anaerobic respiration
what are slow fibers
slower to contract
characteristics of slow fibers
slower to fatigue
capillaries to supply blood, O2 and mitochondria and myoglobin
define myoglobin
red pigment that binds O2, similar to hemoglobin in RBCs; own supply of O2
what are intermmediate fibers
they are medium sized compared to fast fibers and slow fibers
characteristics of intermediate fibers
have some myoglobin; lower compared to slow fibers
better blood supply than fast fibers
slower to fatigue than fast fibers but faster to fatigue than slow fibers
what type of fibers are in white muscle and give e.g.
fast fibers; chicken breast
what type of fibers are in red muscle
mostly slow fibers; e.g. chicken legs
what types of fibers do humans have?
mixed; appears pink
define muscle hypertrophy
muscles get larger from heavy training bc diameter of individual muscle fibers increases
Characteristics of muscle hypertrophy
of mitochondria increa
of myofibrils increase
# of mitochondria increase
# of glycogen reserves
Define muscle atrophy
lack of muscle activity reduces muscle size, tone and power
what does excercise improve
power and endurance
How is anaerobic endurance improved by
intense tiring sets one after the other
Define aerobic endurance
prolonged activities that elevate heart rate & breathing
- muscle are not switching to glycogen & glycolysis- energy is from mitochondria
how is aerobic endurance improved by
cardiovascular training, doing aerobic activities for prolonged periods= growth of new capillaries to supply better flow to muscle cells
How are cardiocytes different from skeletal muscle fibers
-normal size for a cell
- single nucleus
- have intercolated discs
- branched structure
- aerobic (very high in myoglobin and mitochondria)
define intercolated discs
connects cardiocytes together; specialized contact points b/w cardiocytes ( the cell membrane)
functions of intercalated discs
- maintain the structure of the heart
- enhance molecular & electrical connections b/w cardiocytes
- conduct action potentials from cell to cell w/in the heart
define functional syncytium
term for the idea of cells functioning as one
4 functional characteristics of cardiac muscle tissue
- Automaticity
- variable heart rate and contraction tension
- longer contractions than skeletal muscle contractions
- prevention of summation and no tetanus
what is automaticity
heart contracts without neural stimulation; contractions conducted by pacemaker cells (generate impulses)
where does smooth muscle tissue form around
around other tissues
What are 4 e.g.s of what smooth muscle tissue does?
- regulates bp & flow in muscle tissue
- moves secretions, egg and sperm in repro sustem
- causes peristalsis (rhythmic contractions in gastric systems)
- arrector pili muscles –> goosebumps
characteristics of smooth muscle tissue
- non-striated
- thin with tapering ends (spindle shaped)
- single, central nucleus
- no t-tubules, no myofibrils or sarcomeres
- no tendons or aponeuroses
- scattered myosin fibers
- thin filaments are attached to dense bodies
what are dense bodies
anchor strongly into cell structure
how do contractions occur in smooth muscle cells?
whe myosin pulls on the thin filaments, the dense bodies get dragged toward the middle of the cell and the cell scrunches up
dense bodies are also attached to adjacent cells so when one cell contracts, other cells contract as well
other ways to stimulate contraction or relaxation of smooth muscles
hormones
local concentrations of O2 or Co2
stretching
irritation
signals from motor neurons
signals from pace setters
electrical impulses spread from smooth to smooth muscle through gap junctions
Fast fibers eg.
sprinting, weightlifting
anaerobic respiration
