Test 2 Chapter 8-Muscular System Flashcards
What is Muscle Tissue?
The most prominent type by weight, in the body
What are the 3 types of muscle
Skeletal muscle
Cardiac muscle
Smooth muscle
Skeletal Muscle characteristics
-Strained (light dark appearance)
-voluntary control (stimulated by somatic division of efferent)
by alpha motor neurons
What is a motor unit?
Alpha motor neurons and muscle fibers
Cardiac Muscle characteristics?
Found in heart
Properties of skeletal and smooth muscle
Striated
Involuntary regulated by ANS
Smooth Muscle characteristics?
- Where is it found?
- Location based on function?
- Why the name?
- Controlled by?
Found everywhere specifically hollow & tubular organs
Found where ever we need to move something involuntarily (besides the heart)
Named due to LACK of STRIATIONS
Involuntary control by the ANS
Skeletal Muscle is attached to bone via what connective tissue?
Tendons; and helps us to create human movement
What are connective tissues made of?
- Elastin
- Fibronectin
- Collagen
- Extracellular matrix
Connective tissue of the tendon continues through muscle structure what are they?
- Epimysium
- Perimysium
- Endomysium
Individual Muscle cell?
Muscle fiber
Connective tissue wrapping individual muscle fibers?
Endomysium
What is a bundle of muscle fibers?
Fasicle
What connective tissue wraps a fasicle?
PERIMYSIUM wraps a fasicle which is a bundle of muscle fibers
What layer surrounds the muscle?
Epimysium-outer most layer
How are muscle cells able to contract and produce force that is transmitted to bones which work through joints to create movement?
Muscle fibers produce force—>transmit to tendon via connective tissue layers
- Endomysium-Deepest
- Perimysium-wraps around
- Epimysium-wraps around the outside
What are the Elastic Components That are in series with muscle components?
Muscle produces force that is transmitted into bone via TENDONS
Series elastic component
What are Series Elastic Compounds
Series=progressively located throughout
-TENDONS
-Z-LINES
Spring like structure/effect on ends of the muscle
What are Parallel Elastic Components with the bone/muscle fiber?
Endomysium
Perimysium
Epimysium
(Wraps around end to end)
What is a muscle fiber?
Single skeletal muscle cell
Muscles are made up of?
Muscle (organ)
Fasicles (bundles of cells)
Muscle fiber (cell)
MYOFIBRIL (specialized intracellular structure
Thick & Think filaments (cytoskeleton elements)
Myofilaments (protein molecules)
Sarcolemma of Skeletal Muscle Cell
Cell Membrane
Sarco/Myo
Muscle
Sarcolemma is made up of
T-Tubules (Transverse Tubules)
Opening/Passageway in cell membrane (Sarcolemma) that allows passage of extracellular fluid. Goes through the fiber & goes out the other side?
T-TUBULES
Organelles?
Sarcoplasmic Reticulum
Nuclei
Mitochondria
Function of sarcoplasmic reticulum?
Modified function-full of calcium pumps that pump calcium into SR.
STORES CALCIUM (sequesters)
Sarcolemma has what in it?
T-Tubules
What stores/sequesters calcium?
Sarcoplasmic Reticulum
Central regions of sarcoplasmic reticulum associated with T-tubules
Lateral Sacs or terminal Cysterinae
What is the organization of the triad?
Lateral Sac
T-tubule
Lateral sac
Describe skeletal muscle fibes nuclei
- Multinucleated
- tiny and long
- lots of nuclei and can add more nuclei to the cell
Mitchondria
ATP supplier
LOTS OF THEM
80% of muscle volume comes from?
MYOFIBRIL
What are myofibrils?
Bundle of proteins
100s-1000s myofibrils in an individual muscle fiber
CONTRACTILE MACHINERY allows it to form work
Explain the why skeletal muscle looks striated?
Stripes due to arrangement IN myofibrils.
-Myofibrils contain MYOFILAMENTS (Actin & Myosin)
Two muscle pre-fixes
Sarc/o=flesh
My/o=muscle
MYOFIBRILS
Made up of Myofilaments
Basic unit of contraction
Function of Myofilaments?
What are the 3 Myofilaments?
Make up myofibrils
Actual proteins that FUNCTION to allow muscle to produce force
ACTIN
MYOSIN
TITIN (bigger than myosin)
What is Actin?
Where does it attach?
Thin filament
Attaches to Z-line
What is Myosin
Thick filament
Arrangement of Actin and myosin in a myofibril?
Muscle—>Fasicle—>individual fibers—>myofibrils—>actin and myosin
Z-Line (Z-disc)
Z-line to z-line is…
Actin filaments attaches
Boundary of the sarcomere
What is THE FUNCTIONAL UNIT OF CONTRACTION?!
SARCOMERE
A-BAND
Overlap of actin and myosin
Darker
(Anisotropic)
I-Band
Actin (lighter)
Actin
Lighter area
(Isotropic-only 1 thing)
Light Dark regions which make up STRIATIONS appearance
Light=I-Band actin only
Dark=A-band=both actin and myosin
M-Line
Very center of sarcomere
Where Myosin filaments are held in place
H-Zone
Center region of A band
MYOSIN ONLY
What Structures make up the Sarcomere?
- Z-line-z-line = 1 sarcomere
Z-line is the boundary - M-Line center of sarcomere where myosin filaments are held in place
- I-band- contains actin (ACT-THIN) only attached to z-line
- H-Zone center region of A-band ONLY MYOSIN (between the ends of actin)
- A-BAND-is the overlap of actin and myosin
Lateral Sac and T-Tubule are closely associated with eachother. How do they communicate? (What receptor is on the surface?)
T-TUbule has dihydropyradine receptors
Lateral Sacs have Ryanodine Receptors
What receptor is on the T-Tubule?
What is it stimulated by?
Dihydropyradine receptors are on the surface of T-Tubules and stimulated by an electrical stimulus
Which receptors are on the surface of lateral Sacs?
What is the function?
Ryanodine Receptors on the lateral sacs
RR is a calcium channel that pumps calcium into SR
T-Tubule is an extension of what?
Sarcolemma (cell membrane) which is able to get electrically excited.
Ryanodine Receptors are triggered by what?
Dihydropyradine receptors
What does the Ryanodine Receptor do?
It is a CALCIUM CHANNEL
Pumps calcium into SR (stores calcium) and out of SR into cytosol
MYOFILAMENTS make up what?
What are the two major Myofilaments?
MYOFIBRILS;
Actin and myosin
How many proteins make up a myofilament?
About 300 myosin proteins make up a myosin myofilament
The myosin molecule has what structure?
Long Tail section (2 wrapped around)
all tails bind up together to make up filament
Head Unit with 2 heads (project out)= functional part that forms cross bridges
What binding sites are on the Myosin heads?
Actin binding site
Myosin ATPase site
What are cross-bridges?
Neck and head part of myosin molecule that allows myosin to link up with other molecules
What is the Actin Binding site?
What is the Myosin ATPase site?
ACTIN BINDING SITE on myosin head-BINDS ACTIN
MYOSIN ATPase-ENZYME that breaks down ATP to store energy
How is energy stored in the Myosin molecule?
ATP split by myosin ATPase
ADP and Pi remain attached to myosin
Energy stored in cross bridge (ENERGY COCKS cross bridge
Actin is what type of filament?
Thin
When myosin heads split ATP putting the heads in a __ __ ___ and ___ position.
High Energy State and cocked position
Takes 1 molecule of ATP to cock heads so how many molecules of ATP required to cock all myosin heads?
300 Myofilaments x 2 heads=600 molecules of ATP
What is G-Actin
What is F-Actin
G-Actin-individual globular molecules with Myosin binding site
F-Actin-Double helical strand filament of g-actin strung together (2 strings of pearls)
What are the 2 regulatory Proteins?
Tropomyosin
Troponin
Tropomyosin
Thin filament protein.
Sits on surface of actin filament and COVERS MYOSIN BINDING SITES
When covered-actin and myosin do not interact
Uncovered-actin and myosin have the potential to interact
What do the 3 subunits of Troponin attach to?
What is the function of troponin?
1 binds to tropomyosin
1 binds to actin
1 binds to calcium
Holds tropomyosin molecule in place
What happens when troponin interacts with calcium?
Troponin has a conformational change
Since attached to tropomyosin, tropomyosin will have a conformational change
Sliding Filament Theory?
Suggests filaments slide over each other in the way they interact in muscle contraction
3 Phases of Sliding Filament Theory?
- Excitation
- Coupling
- Contraction
(Excitation, contraction coupling–>doesn’t like this as much)
Excitation (Sliding Filament Theory 1st Stage)
- stimulate muscle fiber (produce AP in NMJ due to End plate potential that reaches threshold)–>action potential on sarcolemma
- AP propagates over surface of sarcolemma (muscle fiber not myelinated so contiguous conduction)
- Also Propagates through the muscle via T-TUBULES
- AP stimulates Dihydropyradine receptors on T-Tubule
- RYANODINE RECEPTORS ARE STIMULATED( DHP receptors are next to lateral sacs w/ Ryanodine Receptors )
- Ryanodine Receptors on Calcium channels–>allows calcium channels to open
- Calcium diffuses out of Sarcoplasmic Reticulum (SR) into sarcoplasm (cytplasm of muscle fiber)
- Ca binds to troponin causing a conformational change
- Troponin changes shape–>moves tropomyosin –> exposes myosin binding sites on actin filaments
Coupling (2nd stage of Sliding Filament Theory)
Calcium binds to troponin
Troponin changes shape moving tropomyosin out of the way
Exposes Myosin binding sites
Allowing Actin and myosin to bind to each other (COUPLE)
Contraction (3rd Stage Sliding Filament Theory)
Begin to see shortening occur.
CONTRACTION= POWER STROKE
1. Power Stroke (1st event) 1% shortening of sarcomere
- Happens over and over (40%)
- Need new ATP molecule to add to ATPase (on each of the myosin heads)
- Allows for detaching of actin and myosin= THEY SEPARATE
- take ATP and reload myosin back to high energy state
What are the Events at an NMJ?
- AP propagates down myelinated alpha motor neuron via saltatory conduction
- Reaches Terminal Button
- TB Has Calcium Ion channels which open up
- Increase permeability of calcium
- Influx of Ca –> stimulates exocytosis of vesicles
- vesicles fuse & release NT (Ach into the cleft)
- ACh diffuses across cleft and binds CHOLINERGIC NICOTINIC receptors on motor end plate
- Produces changes in Na/K ion channels
- Produce a graded potential but it ALWAYS REACHES THRESHOLD
- Action Potential moves out of motor end plate
- AP Stimulates normal channels on sarcolemma
- Opens up Na/K channels resulting in an AP
- Cholinesterase removes Acetylcholine
When calcium diffuses into sarcoplasm what does it bind to and do?
Calcium binds to troponin
Troponin conformational change–>Tromomyosin conformational change–> myosin binding sites on actin filament are exposed
Coupling step is 1 step…what happens?
form actomyosin cross bridge. Actin and myosin are linked together. Heads of MYOSIN MOLECULES FORM CROSS BRIDGE
Cross bridge is formed via what?
Myosin heads form cross bridge (link to actin filament) Currently Myosin is in its high energy state
End of coupling
What is the trigger of the myosin molecule?
-Coupling. At the actomyosin cross bridge formation it drops down to low energy (POWERSTROKE)
What is Power Stroke?
1st event of contraction
Myosin molecule drops into low energy state
What happens to Z line during power stroke?
sarcomere pulls into itself (shortens) about 1%
What is the functional unit of contraction?
sarcomere
how much can muscle shorten?
40% of resting length
Excitation involves the
neuromuscular junction
Coupling involves
Actomyosin cross bridge formation
Cross bridge cycle
Contraction involves what?
POWER STROKE
In Muscle Relaxation what happens?
-Getting the cross bridge cycled stopped.
**1. Pumping Calcium back into sarcoplasmic reticulum
- Troponin regains normal shape–causing tropomyosin covers myosin binding site
- Actin and myosin can’t interact any more so muscle relaxes
Relaxation requires what?
pumping calcium back into the sarcoplasmic reticulum
When contraction ends what state is myosin in?
myosin is in cock loaded high energy state (stays ready)
What is Rigor Mortis?
when someone dies muscle gets stiff
Why does Rigor Mortis happen?
- metabolism stops, can’t make atp to run calcium pumps
- power stroke occurs but need atp to release power stroke
- muscle is stuck actin and myosin is stuck together
