Lecture 3/4 textbook notes Flashcards
skeletal muscle`structure
- attached to bones & moves parts of the skeleton
- striated
cardiac muscle structure
- forms heart wall
- striated
skeletal muscle regulation
-voluntary movement and subconscious
>regulated by motor neurons of somatic NS
cardiac muscle regulation
-subconscious control >regulated by ANS >hormones: NE and E >K+/Ca2+/Na+ >body temperature
smooth muscle structure
- walls of hollow internal structures (blood vessels … etc)
- non striated
smooth muscle regulation
-involuntary
>regulated by motor neurons ANS & endocrine hormones
skeletal muscle functions
- producing body movements
- stabilizing body position
- generation heat (shivering)
all muscle functions
-moving and storing substances within the body
>sphincters, stomach, urinary bladder, heart, GI tract, lymph and blood flow
muscle properties
-electrical excitability
>action potentials and pace makers
-contractility
>muscle contracts and generates tension on attachment points -> shortens and movement
-extensibility
>stretch without damage (smooth muscle most stretchy)
-elasticity
>muscle returns to original shape after contraction/extension
skeletal muscle fiber components
- muscle fibers
- fascicles
- tendons
muscle fibers
-10-100 muscle fibres
fascicles
connective tissue surrounds 10-100 muscle fibers -> bundles
tendons
connective tissue surrounds entire muscle and attaches muscle to bone with tendons
sarcolemma
plasma membrane of muscle fiber
transverse tubules
invaginations of sarcolemma which tunnel from surface to the center of the fiber
>filled with extracellular fluid
sarcoplasm surrounded by ____
sarcolemma
sarcoplasm is the ____ of the muscle fiber
cytoplasm
sarcoplasm functions
- house mt
- stores glycogen
- has myoglobin to store O2
myofibrils
extend throughout sarcoplasm
>contractile element
>contain filament (thin and thicK)
sarcoplasmic reticulum encircles ____
myofibril
sarcoplasmic reticulum structure
fluid filled sacs (stores Ca2+)
-ends sacs: terminal cisterna
terminal ciserna function
-release Ca2+
>right next to T tubules
triad
transverse tuble and 2 x terminal cisterna
>linked by DHP receptors with voltage gated Ca2+ channels
Z discs
seperate sacromeres
>dense protein
A band
extends length of thick filament
>has some thin filament
>darker
I band
thin filaments
>includes Z disc
> lighter
H zone
-area inside A band with only thick filaments
M line
center of H zone with proteins that hold thick filaments together
contractile proteins function
generate force during contraction
types of contractile proteins
- myosin
- actin
myosin
-motor protein
>make up thick filament
> 2 heavy (myosin tail)
> 4 light chains (ATP and actin binding sites)
actin
many G-actin -> 1 F-actin … + topomyosin + tropnin -> thin filament
tropomyosin
cover myosin-binding site on actin when relaxed
troponin
binds to tropomyesin, actin and Ca2+
Structural proteins function
help with aligment, stability, extensibility and elasticity
types of structural proteins
- titin
- a-actinin
- myomesin
- nebulin
- dystrophin
titin
connects Z disc with M line
>thick filament stability
a-actinin
connects Z disc + actin (thin filaments) + titin
myomesin
binds titin + thick filamnet -> M line
Nebulin
wraps thin filaments (anchors thin filaments and Z discs)
Dystrophin
links thin filaments ( sarcoma) + integral membrane proteins (sarcolemma)/tendons
sliding filament model
skeletal muscle shortens during contraction because thick and thin filaments slide past eachother
>thin filaments move towards M line of each sarcomere
>H and I zone disappear
contraction cycle Stages
- ATP hydrolysis
- attachement of myosin to actin
- power stroke
- detachment of myosin from actin
contraction cycle: ATP hydrolysis
myosin heat (ATP -> ADP) energized to 90 degrees
contraction cycle: attachment of myosin to actin
myosin head + myosin-binding site (actin)
>phosphate leaves
>myosin head -> crossbridge
contraction cycle: power stroke
myosein head at 90 degrees -> 45
>thin filament pulled past thick towards sarcoma
>ADP leaves
contraction cycle: detachment of myosin from actin
-actin-head + ATP -> actin leaves
somatic motor neuron triggers msucle contraction section!!!
excitation-contraction coupling in skeletal muscle
muscle action potential -> T tubules -> releases Ca2+ from SR -> contraction
decreases in [Ca2+]sarcoplasm causes
skeletal muscle relaxation
Calsequesinin
calcium binding protein in SR that stores calcium
motor unit
somatic motor neuron and many muscle fibers
muscle twitch definition
single action pot. -> muscle fibers -> brief contraction
muscle twich record
myogram
latent period -> contraction period (increased tension) -> relaxation period (decreased tension)
Graded contraction can occur in ___
skeletal muscle
muscles tension factors
- frequency of stimulation
- muscle fiber length
- muscle fiber diameter
- motor unit size
- motor unit recruitment
muscle tension: frequency of stimulation
-1 signal immediately after the other -> only responds to 1st stimulus
>1 signal -> contraction -> refractory period -> 2nd signal -> stronger second contraction
>wave summation
wave summation
- unfused tetanus: sustained but wavering contraction
- fused tentanus: smoot, sustained contraction (rare and incredible strenght)
muscle tension: muscle fiber length
-optimal zone of overlap so myosin head can contact thin filaments
muscle tension: muscle fiber diameter
thicker means more myofibrils and greater tension
muscle tensions: motor unit size
relative to task
>ex: larynx -> 2-3 muscle fibers per motor unit vs leg -> 2000-3000
muscle tensions: motor unit recruitment
- increase number of active motor units for greater contraction force
- asynchronous recruitment: smallest -> larger motor unit recruitment (task based)
muscle tone
- established by different motor units that are alternately active and inactive
- flaccid: motor neurons are damaged or cut
muscle attachment site
origin: muslce tendon- stationary base
insertion: muscle- movable bone
muscle actions
- flexion: bending limb at join
- exention: straightening limb at joint
- antagonistic muscles: biceps and tricepts
lever system with muscles
- lever: bone
- joint: fulcrum
- effort: movement
- load: opposes movement
mechanical advantage
load closer to fulcrum than effort
>think wheel borrow
series elastic elements
tendons are elastic and in series with contractile elements of the muscle
isotonic muscle contraction
- constant muscle tension but changing muscle lenght
ex: body movements and object movement
isotonic concentric
tension generated exceeds load -> shortens muscles
>ex: picking book off table
isotonic eccentric
tension exerted resists movement of load -> slows lenghtening of muscle
ex: putting book back on table
isometic contraction
tension generated does not exceed load-> muscle lenght does not change
>ex: trying to left object that is too heavy or holding something steady
cardiac vs skeletal muscle fibers (structure)
cardiac is: shorter in length and diameter, has more branching, less T tubules and smaller SR
cardiac muslce: intercalated discs
-connect the ends of muscle fibers (thickening of sarcolemma)
intercalated discs: desmosomes
cell junction that mechanically binds 2 fibers
helps prevent failing apart
intercalated discs: gap junctions
cell junction that electrically binds 2 fibers
cardiac fibers: functional syncytium
at gap junction action potentials spread throughout fibers
cardiac muscle prevent tetanus with ___
long refractory periods
Sinoatrial (SA) node location
in the wall of the right atrium close to the opening of the superior vena cava.
Atrioventricular (AV) node location
in the interatrial septum
Atrioventricular (AV) bundle location
in the upper part of the interventricular septum.
Right and left bundle branches location
in the interventricular septum.
Purkinje fibers location
in the ventricular wall.
