3 types of muscular tissue
Characteristics of Muscles (5)
(elaine received constant contractions extensively)
responsiveness to what? (3)
-to chemical signals, stretch, & electrical charges
electrical change triggers a wave of excitation
shortens when stimulated
capable of being stretched
returns to original length after being stretched
striated VOLUNTARY muscle attached to one or more bones
Muscle cell =______
alternating light and dark transverse bands
What do tendons attach specifically?
muscle to bone matrix
connective tissue around muscle cells
connective tissue around muscle fascicles
connective tissue surrounding entire muscle
what is the purpose of collagen? (3)
returns muscle to resting length
protects muscles from excessive stretching
contributes to power output & muscle efficiency
plasma membrane of a muscle fiber
cytoplasm of a muscle fiber
long protein bundles that occupy the main portion of the sarcoplasma
what are the components of myofibrils?what do they store?
glycogen (provide energy for heightened exercise) & myoglobin (stores oxygen)
where are mitochondria packed in muscle fibers?
in spaces between myofibrils
stem cells that fuse to form each muscle fiber
sarcoplasmic reticulum (SR)
smooth ER that forms a network around each myofibril
what is the sarcoplasmic reticulum a reservoir for?
what activates the muscle contraction process?
dilated end sacs of SR which cross the muscle fiber from one side to the other
tubular infoldings of the sarcolemma that penetrate through the cell & emerge on the other side
a T tubule & two terminal cisterns
made of several hundred myosin (golf club)
fibrous actin of 2 intertwined stands
What portion of the actin subunit can bind the head of the myosin molecule?
gobular (G) actin
blocks the active sites of G actin & prevents myosin from binding when muscles are relaxed
small calcium binding protein on each tropomyosin molecule
myosin & actin
tropomyosin & troponin
what happens when calcium is released into the sacroplasm?
Ca binds to troponin which then changes shape and moves tropomyosin from the active site of actin
Z disc to Z disc
functional contractile of muscle fiber
Which myofilament is free floating?
myosin, it is not anchored like actin
dark; overlapping of thick and thin filaments
middle of A band (thick filaments ONLY)= bare zone
middle of H band
light; crosses over 2 sacromeres
provides anchorage for thin filaments and elastic filaments
what myofilaments do muscle fibers contain? (3)
thin, thick, and elastic
which band shortens during contraction
Why do muscle cells shorten?
because their individual sarcomeres shorten (Z disc pulled closer together)
a skeletal muscle never contracts unless stimulated by ______? what happens if this is severed?
a nerve; muscle is paralyzed
somatic motor neurons
nerve cells whose cell bodies are in the brainstem & spinal cord that serve skeletal muscles
what portion of somatic motor fibers lead to the skeletal muscle?
1 nerve fibers= ______ muscle fiber
what does an effective contraction require?
the contraction of several motor units (one nerve fiber + muscle fibers) at once
average motor unit?
200 muscle fibers for each motor unit
small motor units are used for what?
fine degree of control
ex. eye & hand muscles
large motor units are used for what?
more strength than control
point where a nerve fiber meets its target cell
when target cell is a muscle fiber
swollen end of nerve fiber
tiny gap between synaptic knob & muscle sarcolemma
What is the purpose of Schwann cells?
to isolate & insulate all of the NMJ from surrounding tissue fluid
synaptic vesicles undergo ______ releasing ACh into ______
exocytosis; synaptic cleft
Lack of ACh receptors leads to?
paralysis in disease
What separates the Schwann cells & the entire muscle cell from surrounding tissue?
What does the basal lamina contain?
acetylcholinesterase (AChE) to break down ACh after contraction causing relaxation
What helps hold the synaptic knob in place?
Schwann cells & basal lamina
electrical potential; a dif in electrical charge from one point to another
What is the resting membrane potential?How is it maintained?
about -90mV; Na-K pumps
What is happening in an unstimulated resting cell? (3)
- more anions on the inside of the plasma membrane
- plasma membrane is polarized
- excess Na (ECF) and excess K (ICF)
What else is inside the ICF?
proteins, nucleic acids, and phosphates (all which cant penetrate the membrane)
What is happening in a stimulated muscle fiber?
- ion gates open in the plasma membrane
- Na moves inside (down concentration gradient)
- cations override negative charge of ICF (depolarization)
- Na gates close/ K open
What turns the membrane back into its negative state?
loss of positive K ions (repolarization)
quick up & down
polarized(resting)-> depolarization-> repolarization
what type of paralysis is tetanus?
spastic paralysis caused by C. tetani
state in which the muscles are limp & cannot contract
type of food poisoning caused by neuromuscular toxin secreted by C. botulinum (prevent contraction)
What does the RMP shift to when Na is moved into the cell?
-90mV to +75mV
length tension relationship
amount of tension generated by a muscle & the force of contraction depends on how stretched/contracted it was before stimulated
What does the optimum resting length produce?
greatest force when muscle contracts
monitored by the nervous system that adjusts the length of the resting muscle & maintains a state of partial contraction
What does overly contraction cause?
crick in your neck
What does overly stretched cause?
actin filament have no myosin heads to attach to
hardening of muscles & stiffening of body beginning 3 to 4 hours after death
muscle relaxation requires _____, which is no longer produced after death
chart of the timing & strength of a muscle contraction
_____, subthreshold electrical stimulus cause ___ contraction
min voltage necessary to generate an action potential in the muscle fiber & produce contraction
quick cycle of contraction when stimulus is at threshold or higher
Twitches vary depending on?
- stimulus frequency
- concentration of Ca in sarcoplasma
- how stretched the muscle was
- temp of muscle
If the pH of the sarcoplasma is lower than normal, what happens?
When stimulus intensity remains _____ twitch strength_____?
constant; vary with the stimulus frequency
10-20 stimuli per second produces what type of twitch? (staircase) describe
treppe; the muscle still recovers fully between twitches, but each twitch develops more tension than the one before
20-40 stimuli per second produces what? describe
incomplete tetanus (piggy back); each new stimulus arrived before the previous twitch is over
40-50 stimuli per second produces what? describe
complete tetanus; muscle has no time to relax between stimuli
producing internal tension; but external resistance causes it to stay at the same length or become longer (NO MOVEMENT)
muscle shortens as it maintains tension
muscle lengthens as it maintains tension
ATP supply depends on availability of: (2)
organic energy sources (glucose & fatty acids)
2 pathways of ATP synthesis? which yields the most ATP?
aerobic respiration (use oxygen) yields more ATP (36 per molecule) anaerobic fermentation (without the presence of oxygen)
For short intense exercises how is oxygen supplied?
via myoglobin for limited aerobic respiration
What enzymes are used by muscles for transfer of phosphate? (2)
myokinase (makes cyclic AMP) creatine kinase (uses creatine phosphate)
What system is used for nearly all energy used for short bursts of intense activity?
After the phosphagen system-> a muscle enters ___ ____ which uses ___ to produce _____. How many ATPs are gained?
Anaerobic fermentation; glucose ; lactic acid
2 ATPs per molecule
long term energy uses which synthesis pathway?
What happens during fatigue? (4)
- ATP synthesis decline as glycogen consumed
- ATP shortage; slows down Na-K pumps
- lactic acid lowers pH of sarcoplasm
- motor nerve fibers use up ACh
endurance? how is it determined?
ability to maintain high intensity exercise for more than 4-5 minutes; by one’s max oxygen uptake
How can you “beat” fatigue? (2)
- taking oral creatine (increases level of creatine phosphate in tissue: increase speed of ATP regeneration)
- carbohydrate overload (extra glycogen packed in)
slow oxidative muscle fibers (3)
- slow twitch, red, type I fibers
- abundant in mitochondria, myoglobin
- adapted for aerobic respiration & fatigue resistance
fast glycolytic muscle fiber
- fast twitch, white, type II fiber
- quick response, but not fatigue resistance
properties of cardiac muscle? (5)
- contraction w/ regular rhythm
- must contract in unison
- contractions must last long to expel blood
- must work in sleep
- tightly resistant to fatigue
Cardiac muscles are _____ and contain _____
in cardiac muscle, myocytes are joined at notched linkages called what?
Cardiac muscles contain _____, so they can contract without need for nervous stimulation
built in pacemaker
How are damaged cardiac muscle cells repaired?
via fibrosis (not capable of mitosis-very little)
which synthesis is used almost exclusively by cardiac muscle?
Smooth muscle does not contain?
t-tubule or sarcomere structure
characteristics of smooth muscle (3)
- capable of mitosis & hyperplasia
- injured muscle can regenerate well
- some lack nerve supply
Describe myocyte structure in smooth muscle?
- fusiform shape
- no visible striations
- Z discs are replaced by dense bodies
Which type of smooth muscle is more widespread? does it require a nerve supply?what does it use
single unit smooth muscle; NO; gap junctions
Smooth muscle can contract in response to ____. Such as (3)
- hormones, CO2, stretch, oxygen deficiency
Does stimulation mean contraction in smooth muscle?
NO; relax arteries or contract bronchiles
What do the smooth single units contain?
autonomic nerve fibers varicosities
What are varicosities?
beadlike swellings that contain synaptic vesicles & few mitochondria
How is contraction different in smooth vs skeletal muscle?
- calcium binds calmodulin on thick filaments
- calcium enters from the cell EC
- very slow due to arrangement (Ca must be actively removed)
- smooth contract forcefully when greatly stretched
the ______ ______ is resistant to fatigue
latch bridge mechanism
stress relaxation response
helps hollow organs gradually fill (bladder)