MB Quiz 3 Flashcards
What are the three types of muscle
Skeletal
Cardiac
Smooth
Perimysium
Connective tissue that surrounds fascicles of muscle fibers
Endomysium
Connective tissue that surrounds skeletal muscle cells
How are skeletal muscle cells grouped within the perimysium?
In Fascicles
Epimysium
Connective tissue where all Fascicles are grouped together forming the muscle
Describe the gross structure of a skeletal muscle in terms of connective tissue.
Skeletal muscle cells are surrounded by a connective tissue sheath called the Endomysium
Cells are grouped in fascicles surrounded by Perimysium
Fascicles are grouped together to form the muscle which is surrounded by Epimysium
What are tendons
Tendons are tissues that connect muscle to bone
List the connective components of the skeletal muscle organ from the single muscle cell until the organ
Muscle fiber/cell -> Endomysium -> Fascicle-> Perimysium -> Group of Fascicles -> Epimysium
Are Skeletal muscle cells mono-nucleated or multinucleated?
Multinucleated
Sarcomere
Unit of a myofibril contained between two Z lines
Describe the structure of a sarcomere
A sarcomere is the unit of a myofibril contained between two z lines
The Z line/disk separates two sarcomeres
The I band is the area where there are only thin filaments
The H zone is the area where are only thick filaments
The M line is in the center where thick filaments are linked with accessory proteins
The A band goes along the length of the thick filaments.
The Z line bisects the I band
The H zone bisects the A band
The M line bisects the H zone
The outer edge of the A band has A) Thick filaments only B) Thin Filaments only C) No Filaments D) Thick and Thin Filaments E) Connective Tissue F) Filaments linked with accessory proteins
D
What is the main function of accessory proteins in the sarcomere?
Maintenance of structure
What is the function of alpha actinin?
Maintains the actin lattice
What is the function of dystrophin
Anchors actin filaments to the Sarcolemma
Sarcolemma
Specialized membrane which surrounds striated muscle fiber cells
Give two accessory proteins in the sarcomere along with their functions
Alpha actinin Maintains actin lattice
Dystrophin anchors actin filaments to the Sarcolemma
What is the sarcoplasmic reticulum
Modified smooth ER
What are T-tubules
Inwards extensions of the Sarcolemma.
What are myofibrils composed of?
Myofibril is composed of overlapping myosin (thick), actin (thin), and accessory proteins.
Muscle fibers contain a large amount of which organelle?
Mitochondria
Where are triads located?
how many are found per sarcomere?
Junction of the A and I bands
Two
What are the components of each filament and how are the filaments associated with each other.
The myosin (thick filament) consists of a large number of individual myosin molecules. It is made up of a myosin tail which makes up the filament itself, a hinge region which allows the molecule to move and swivel and a myosin head which forms the cross bridge where it binds to the thin filaments (actin)
The thin filament consists of actin (G-actin molecules) aggregated together forming the fiber. Tropomyosin is a protein that goes along the length of the thin filament forming a complex with Troponin which attaches to the myosin head
What are the two globular sites of the Myosin Head and how does it bind to Troponin?
The myosin head contains two globular sites:
- Myosin ATPase Site (energy)
- Actin binding site (To bind with Troponin)
Troponin binds to Ca2+ causing conformational changes which move tropomyosin relative to actin exposing sites on actin allowing myosin heads to bind
Describe the interactions between actin and myosin in muscle contraction
- Action potential in T tubule activates voltage-sensitive receptors which trigger Ca2+ release into cytosol
- Calcium ions bind to Troponin changing its shape, exposing actin active sites
- Myosin head attaches to the actin myofilament, forming a cross bridge
- Myosin Head executes power stroke
- Removal of Ca2+ by active transport into the sarcoplasmic reticulum (SR) after action potential ends
- Tropomyosin blockage restored blocking myosin binding sites on actin relaxing the muscle by breaking the cross-bridge link