Lecture 10 - Muscular System Flashcards
Which types of muscle are striated?
-Skeletal
-Cardiac
What type of muscle isn’t striated?
Smooth muscle
Which type of muscle is under voluntary control?
Skeletal
Which type of muscle is under involuntary control?
-Cardiac
-Smooth
What are the functional properties of skeletal muscle?
-Contractility (shorten)
-Excitability (receive/respond to stimuli)
-Extensibility (lengthen)
-Elasticity (return to normal)
What are the functions of skeletal muscle?
-Production of movement
-Maintaining posture
-Stabilizing joints
-Generating heat
What is the epimysium?
Connective tissue surrounding the entire muscle
What is the perimysium?
Connective tissue surround the fascicles (muscle bundles)
What is the endomysium?
Connective tissue surrounding an individual muscle fibre
What are the contractile proteins of a myofibril and what is their function?
Actin and Myosin
–> generates force during contraction
What are the regulatory proteins of a myofibril and what is their function?
Troponin and Tropomyosin
–> Initiate and terminate contraction
What are the structural proteins of a myofibril and what is their function?
Titin, Myomesin, Dystrophin
–> Maintain alignment, elastic and extensible
What are the 3 types of muscle fibres
-Slow oxidative (Type 1)
-Fast oxidative-glycolytic (Type 2A)
-Fast glycolytic (Type 2B)
What are some characteristics of slow oxidative (Type 1) fibres?
-Red colour
-High fatigue resistance
-Aerobic
-High ATP generation
-Low contraction velocity
What are some characteristics of fast oxidative-glycolytic (Type 2A) fibres?
-Red/pink colour
-Intermediate fatigue resistance
-Aerobic & glycolysis
-Intermediate ATP generation
-High contraction velocity
What are some characteristics of fast glycolytic (Type 2B) fibres?
-White colour
-Low fatigue resistance
-Glycolysis
-Low ATP generation
-High contraction velocity
What is Myomensin?
A structural protein within a sarcomere (M Line). Anchors myosin (thick filament).
What makes up the Z Line and what is its function?
Made up of Actinin and Nebulin.
Function: Anchors actin filaments, gets pulled inward during contraction
What is the function of Titin?
Is the skeleton of the sarcomere and provides passive elasticity
What is another name for cross-bridges?
Myosin heads
What steps occur after a muscle fibre receives an action potential?
- Ca2+ is released and binds with troponin
- Pulls troponin-tropomyosin complex away from cross bridge binding site
- Cross-bridge binding occurs and the myosin pulls on the actin
- ATP is hydrolyzed to ADP and the cross-bridge releases. Binding site becomes re-covered by TT complex
What is another name for a muscle fibre
Myocyte
Where is calcium released from?
Sarcoplasmic reticulum
What is responsible for controlling the amount of Calcium available?
Calsequestrin
What is the composition of an actin filament?
-Actin molecules
-Troponin
-Tropomyosin
A myocyte has _______ nuclei
many
What is the functional (contractile) unit of muscle?
Sarcomere
What are A and I bands?
A Band: myosin and actin and M line
I Band: only actin and Z line
What is the H zone?
Area with only myosin
What area of the sarcoplasmic reticulum produces Calsequestrin?
Cisternae
What makes up the triad of the sarcoplasmic reticulum?
2 Terminal cisternae and T-tubule
What is different about cardiac muscle compared to other striated muscle?
-Uninucleated/binucleated
-Branched
-Lots of mitochondria and lipids
How do cardiac muscle cells communicate with each other?
Through gap junctions, where the action potential signal travels through
What is functional syncytium?
Rapid, synchronous contractions
How long is a cardiac action potential?
100-250 msec
How long is the action potential in skeletal muscle?
1-2 msec
Why is the cardiac action potential slower than the skeletal muscle action potential?
Slow calcium channels which bring extracellular Ca2+ to trigger sarcoplasmic reticulum Ca2+ release
What type of organs usually have smooth muscle?
Hollow organs
What shape are the cells in smooth muscle?
Fusiform (spindle shaped)
What DOESN’T smooth muscle have?
-Myofibrils
-T-tubules
What are Caveolae?
Voltage gated Ca2+ channels in the SR of smooth muscle
What are the dense bodies in smooth muscle and what do they do?
Z-lines
-Anchors actin
-In the membrane or cytoplasm
What is multi-unit smooth muscle?
Smooth muscle cells that are separately innervated (neurogenic)
What are examples of multi-unit smooth muscles?
Ciliary body and iris
What is single-unit smooth muscle?
Muscle fibres are connected via gap junctions and the impulse can travel between cells (myogenic)
What are examples of single-unit smooth muscles?
-GI tract
-Respiratory
-Urinary
-Reproductive
-Vasculature
How many nuclei does smooth muscle have?
One (uninucleated)
Which types of muscles have sarcomeres?
-Skeletal
-Cardiac
Which types of muscles have T-tubules and where?
-Skeletal (A and I band junction)
-Cardiac (Z line)
What does smooth muscle have instead of T-tubules?
Caveoli
Where does cardiac muscle have gap junctions?
At the intercalated discs
Which muscle types have individual neuromuscular junctions?
-Skeletal
-Smooth (multi-unit)
What is the source of calcium for skeletal, cardiac, and smooth muscle?
Skeletal: SR
Cardiac: SR and ECF
Smooth: ECF
Where is the site of Ca2+ binding and regulation in skeletal and cardiac muscle?
Troponin on thin filaments
Where is the site of Ca2+ binding and regulation in smooth muscle?
Calmodulin in SR
Which type of muscle can tetanize?
Skeletal and smooth (but not as often)
Which muscles have a slow onset of contraction?
-Cardiac
-Smooth
Where is the nervous input in skeletal muscle?
Nicotinic receptors
Where is the nervous input in cardiac muscle?
Excitation at B1 receptor; inhibition at muscarinic receptors
Where is the nervous input in smooth muscle?
Excitation and inhibition at muscarinic receptors; Excitation at alpha or beta receptors
Are skeletal, cardiac, and smooth muscles aerobic or anaerobic?
Skeletal: aerobic and anaerobic
Cardiac: aerobic
Smooth: mostly aerobic
