Human Physiology Ch 11
triad
1 transverse tubule and 2 terminal cisternae on each side
aerobic respiration
Respiration that requires oxygen, produces ATP, CO2, H2O, heat
What 2 reactions does aerobic respiration include?
Krebs cycle, ETC
stress-relaxation response
Responds to stretch only briefly, then adapts to new length; Retains ability to contract on demand; Enables organs such as the stomach and bladder to temporarily store contents
unfused (incomplete) tetanus
Some relaxation occurs between contractions. The results are summed
sliding filament mechanism
The explanation of how thick and thin filaments slide relative to one another
calsequestrin
calcium binding protein
hyperplasia
increase in number of fibers
What proteins make up the M line?
myomesin
L-type voltage gated Ca channels
open for a long period of time, allow extra Ca to enter sarcoplasm serve as voltage sensors
neuromuscular junction (NMJ)
the synapse between a somatic motor neuron and a skeletal muscle fiber
smooth muscle components
thick and thin filaments, NO transvere tubules, small amount of SR
transverse (T) tubules
thousands of tiny invaginations of the sarcolemma filled with ECF due to being open to outside of fiber
resting membrane potential of skeletal muscle
-90mV
contraction cycle
1. ATP hydrolysis 2. Attachment of myosin to actin to form cross-bridges 3. Power stroke 4. Detachment of myosin from actin
4 functions of muscle
1. Produce movement 2. stabilize body positions 3. Store and move substances within body 4. Generate heat
3 ways oxygen debt used to restore metabolic conditions
1. convert lactic acid back into glycogen 2. resynthesize creatine phosphate and ATP 3. replace oxygen removed from myoglobin
4 special properties of muscle
1. electrical excitability 2. contractility 3. extensibility 4. elasticity
contraction phase of muscle twitch
10-100msec, Calcium binds to troponin, myosin cross bridges form, peak tension in muscle fiber
latent period of muscle twitch
2 msec, brief delay between application of stimulus and beginning of contraction
tension maximal at a sarcomere length of ____
2.2um
titin
3rd most plentiful protein in skeletal muscle (after actin and myosin) 50x larger than avg protein
inside a myosin molecule
6 polypeptide chains: 2 heavy large chains, 4 small light chains
inside sarcomeres
A band, I bands, H zone, M line
What does the sarcoplasmic reticulum store when relaxed?
Calcium ions
What is more plentiful than ATP in the sarcoplasm of a relaxed muscle fiber?
Creatine phosphate (3-6x more)
What cytoskeletal protein links thin filaments to integral membrane proteins of the sarcolemma?
Dystrophin
F actin
G actin molecules linked together, fibrous
M line
Middle of sarcomere, holds thick filament in place
How does muscle contraction occur?
Myosin heads pull thin filaments toward M line, causes thin filaments to slide inward and meet at center of sarcomere I band and H zone narrow, disappear once contracted width of A band unchanged
creatine
a small amino acid like molecule that is synthesized in the liver, kidneys, and pancreas and then transported to muscle fibers
What type of proteins make up Z discs?
a-actinin
contractility
ability of muscle to contract forcefully when adequately stimulated
Elasticity
ability of muscle to return to its original length and shape after contraction or extension
extensibility
ability of muscle to stretch without being damaged
electrical excitability
ability to respond to stimuli by producing action potentials neurons AND muscle cells
components of thin filament
actin, tropomyosin, troponin
Ca2+ -ATPase pumps
active transport proteins that transport Ca from sarcoplasm in SR
What happens when a somatic motor neuron is activated?
all of its muscle fibers in the motor unit contract in unison
muscular system
all skeletal muscles of the body
glycogen
also inside sarcoplasm, large polysaccharide consisting of thousands of glucose molecules covalently linked together stores glucose
myoglobin
also inside sarcoplasm, red-colored, oxygen-binding protein that is found only in muscle
striations in muscle
alternating light and dark bands (skeletal muscle)
where do tendons attach to bone?
at the origin and insertion
origin
attachment of a muscle's tendon to the more stationary bone
insertion
attachment of the muscle's tendon to the more movable bone
flexion
bending a joint
levers
bones, move around a fixed point
glycolysis
breaks down glucose into two molecules of pyruvate
twitch
brief contraction of a group of muscle fibers within a muscle in response to a single action potential
Autorhythmycity
built in rhythm the heart has to initiate each contraction (pacemaker)
fascicles
bundles of muscle fibers, 10-100
the concentration of ___ is 10,000x higher in SR than in sarcoplasm in a relaxed muscle fiber
calcium
What does sarcoplasmic reticulum release to trigger muscle contraction?
calcium ions are released
cardiac muscle comparison to skeletal muscle
cardiac and skeletal both striated, but cardiac is involuntary
effort (E)
causes movement
isotonic contraction
constant tension while muscle changes length used for moving objects
myofibrils
contractile elements of the skeletal muscle fiber, have filaments inside
actin and myosin
contractile proteins in muscle
3 proteins that make up myofibrils
contractile, regulatory, structural
graded contractions
contractions that vary in strength depending on how much force is needed
tendon
cord of connective tissue that attaches to muscle of bone
slow wave potentials
cycles of alternating depolarization and repolarization that do not necessarily reach threshold
sarcoplasm
cytoplasm of a muscle fiber, mitochondria, glycogen, and myoglobin are inside
A band of sarcomere
dark middle part, extends entire length of thick filaments
hypotonia
decreased or lost muscle tone
thin filaments inside smooth muscle
dense bodies, similar to Z discs in striated muscle fibers
2 phases of skeletal muscle contraction
depolarizing (rising) phase and a repolarizing (falling) phase
Terminal cisternae of sarcoplasmic reticulum
dilated end sacs that butt against a T tubule from both sides
Repeated ____ contractions produce muscle damage and soreness
eccentric isotonic
creatine phosphate
energy rich molecule found in muscle fiber
hypertrophy
enlargement of existing cells
multi unit smooth muscle
fibers that act independently of each other as multiple units
sarcoplasmic reticulum
fluid filled system of membranous sacs that encircle each myofibril
3 ways a skeletal muscle fiber can form ATP
from creatine phosphate by anaerobic glycolysis by aerobic respiration
When tremendous strength is needed, what type of tetanus is used>
fused tetanus
contractile proteins
generate force during contraction
What is used to generate ATP once creatine phosphate is depleted?
glucose
When oxygen is present, what happens?
glycolysis, Krebs cycle, ETC
smooth muscle contraction
happens once myosin head of thick filaments are phosphorylated
regulatory proteins
help switch contraction process on and off
voluntary manner
how skeletal muscle mainly works, activity consciously controlled by motor neurons (somatic motor system) some skeletal muscles controlled subconsciously too
when do skeletal muscles arise?
in embryonic development, from myoblasts # of muscle fibers you have is set before you are born
Ca release channels
in terminal cisternal membrane of SR aka ryanodine receptors
muscle fatigue
inability of a muscle to maintain force of contraction after prolonged activity
hypertonia
increased muscle tone
spasticity
increased muscle tone (stiffness) associated with an increase in tendon reflexes and pathological reflexes
rigidity
increased muscle tone where reflexes not affected
length-tension relationship
indicates how the forcefulness of muscle contraction depends on the length of the sarcomeres within a muscle before contraction begins
functional synctium of heart
interconnected cells that acts as single unit atria, and ventricles of heart two synctiums
load and velocity in concentric isotonic contraction
inversely related
fulcrums
joints, the fixed point
structural proteins
keep the thick and thin filaments in proper alignment and link the myofibrils to the sarcolemma and extracellular matrix
phases of a twitch
latent period, contraction phase, relaxation phase
I band
light area on each side of A band, contains rest of thin filaments
Dihydropyridine receptor (DHP)
links the T tubule and terminal cisternae L-type voltage gated Ca2+ channels
mechanical advantage
load closer to fulcrum than effort
mechanical disadvantage
load farther from fulcrum than the effort
smooth muscle
located in walls of hollow internal structures (blood vessels, airways, stomach, intestines, uterus)
actin
main component of thin filaments aka G actin (globular proteins)
myoblasts
mature skeletal muscle fiber that has multiple nuclei
satellite cells
matured myoblasts, fuse with one another to regenerate functional muscle fibers
What produces large amounts of ATP for muscle contraction?
mitochondria
single unit smooth muscle
most common, fibers contract together as a single unit aka visceral smooth muscle
myosin
motor protein and all types of muscle, push/ pull cell structures to achieve movement
the functional contractile unit of a skeletal muscle
motor unit
organization of skeletal muscle
muscle --> muscle fiber --> fascicles --> tendon
H zone
narrow zone in center of each A band, contains thick filaments
What nonelastic protein wraps around thin filaments?
nebulin
asynchronous recruitment
normally, some motor units are contracting while others are relaxed
load (resistance)
opposes movement
2 sources of oxygen for muscle tissue
oxygen diffused into muscle fibers oxygen released by myoglobin
Z disc (line)
passes through each I band, separates sarcomeres
refractory period of muscle fiber
period of lost excitability, time varies with each muscle (skeletal muscle period is short)
sarcolemma
plasma membrane of a muscle fiber
motor unit recruitment
process of increasing the number of active motor units
troponin
protein that consists of 3 globular subunits, one binds to tropomyosin, one binds to actin, one binds to calcium ions
anaerobic glycolysis
pyruvic acid generated during glycolysis is converted to lactic acid 2 lactic acid, 2 ATP
myogram
record of muscle contraction
sarcomeres
repeating units of myofibrils, filled with thin and thick filaments (not entire length)
recruitment of motor units
responsible for producing smooth movements instead of jerks
tropomyosin
rod-shaped protein that joins with other tropomyosin molecules to form 2 long strands that wrap around F actin double helix
excitation-contraction
sequence of events that links muscle action potential to muscle contraction happens at triads of skeletal muscle fiber
muscle tone
small amount of tautness or tension in muscle due to weak, involuntary contractions of motor units
contraction in smooth muscle vs striated muscle
smooth muscle contraction--triggered by calcium induced changes in thick filaments striated muscle contraction--triggered by calcium induced changes in thin filaments
fused (complete) tetanus
smooth, sustained contraction individual twitches cannot be detected
motor unit
somatic motor neuron plus all the muscle fibers it innervates
pacemaker potential
spontaneous depolarization that always reaches threshold, triggers making of action potential
wave summation
stimuli arriving at different times causes contractions with greater tension
extension
straightening a limb at a joint
component of NMJ (3)
synaptic end bulbs, motor end plate, synaptic cleft
eccentric isotonic contraction
tension exerted by myosin crossbridges resists movement of load, slows lengthening process walking downhill
concentric isotonic contraction
tension generated great enough to exceed load, muscle shortens picking book up off table
isometric contraction
tension generated is not enough to exceed load, muscle does not change length lifting objects too heavy to move
oxygen debt
the added oxygen, over and above the resting oxygen consumption, that is taken into the body after exercise used to pay back or restore metabolic conditions
key structural proteins
titin, α-actinin, myomesin, nebulin, and dystrophin
voltage gated channels and calcium release channels
trigger contraction of smooth muscle
When does wave summation and both kinds of tetanus happen?
when more Calcium is coming from SR by more stimuli whiles levels of calcium in the sarcoplasm are still elevated from first stimulus
myosin binding site
where a myosin head can attach
load-velocity relationship
The principle that the velocity of shortening of a muscle during isotonic contraction decreases as load increases.
What triggers a muscle action potential at the NMJ?
Acetylcholine