L21: Muscle Tissues Flashcards
What are the four main tissue types?
- Epithelial;
- Connective;
- Muscle;
- Nervous.
What is the function of muscle tissues?
Specialised for contraction
Provide an example of muscle tissue.
Cardiac cells
Describe the control, structure and type of somatic muscle tissue.
- Somatic, voluntary;
- Striated;
- Skeletal.
Describe the control, structure and type of autonomic muscle tissues.
Cardiac:
- Autonomic, involuntary;
- Striated;
- Cardiac.
Smooth:
- Autonomic, involuntary;
- Non-striated;
- Smooth.
Describe the structure of skeletal muscle.
- Elongated, unbranched cylindrical cells (muscle fibres);
- Multiple peripheral nuclei;
- Numerous myofibrils;
- Arrangement of myofibrils causes striated appearance.
What structure separates individual muscle fibres of skeletal muscle?
Endomysium
What is the name for a group of skeletal muscle fibres?
Fasciculi
What is the difference between a perimysium and epimysium?
- Perimysium - loose CT - surrounds each fascicule;
- Epimysium - dense CT - surrounds entire muscle.
What is the name of the specialised plasma membrane of skeletal muscle?
Sarcolemma
What separates each myofibril?
A thin layer called the sarcoplasm
How are myofibrils arranged in skeletal muscle?
In parallel, with many mitochondria between them
What repeating unit makes up myofibrils?
Myofilaments
Thick myofilaments are composed of…
myosin
Thin myofilaments are composed of…
actin
Myosin appears…
dark
Actin appears…
light
Light bands are directed by…
Z lines
Z-lines divide each myofibril into…
contractile units called sarcomeres
What is the name of a contractile unit in skeletal muscle?
Sarcomere
What is the process by which sarcomeres, in skeletal muscle, contract?
Sliding filament mechanism
Explain the sliding filament mechanism:
- ATP allows myosin to bind to actin;
- This causes a conformational change which allows the filaments to slide over each other;
- This causes the sarcomere to shorten (contract).
How is skeletal muscle innervated?
Through somatic motor neurones
individual motor neurones innervate multiple muscle fibres, a motor unit
What neurotransmitter is detected on muscle fibres to lead to a contraction?
Acetylcholine
Explain the sarcolemma and sarcoplasmic reticulum.
Sarcolemma:
- Specialised plasma membrane that invaginates into sarcoplasm to form T-tubules
Sarcoplasmic reticulum:
- Network of tubules associated with T-tubules and myofibrils;
- Store and supply Ca2+.
What is myocardium?
Specialised striated muscle tissue, found in the heart
Describe the structure of cardiac muscle.
- Elongated, branched cylindrical cells;
- One or two centrally located nuclei;
- Arrangement of myofibrils causes striated appearance.
What are the three layers of the heart wall?
- Pericardium (P): outer, support layer;
- Myocardium (M): cardiac muscle tissue;
- Endocardium (E): single layer of endothelial cells.
What type of connective tissue surrounds cardiac muscle fibres?
Reticular, supports rich capillary network
In cardiac muscle, intercellular junctions (between cardiac cells) are called…
intercalated discs
What is the process by which sarcomeres, in cardiac muscle, contract?
Sliding filament mechanism
What are the main contraction differences between skeletal and cardiac muscle?
- Cardiac is involuntary, skeletal is voluntary;
- In cardiac muscle, the sarcoplasmic reticulum slowly releases Ca2+ for continuous contraction;
- Modified cardiac cells, conducting system (SA node - pacemaker cells);
- Cardiac cells modulated by autonomic and hormonal stimuli.
Describe the structure of smooth muscle.
- Elongated, small, spindle-shaped fibres;
- Single, centrally located nucleus;
- No sarcomeres, no striations.
Where is smooth muscle found?
Lining hollow organs
Describe the structure of the GI tract.
- 2 muscle layers;
- Circular, inner;
- Longitudinal, outer.
What are the roles of the 2 muscle layers, in the GI tract, during peristalsis?
- Circular, constricts;
- Longitudinal, shortens
What is the process by which smooth muscle contracts?
- Presence of actin and myosin;
- Sliding-filament mechanism.
What is the role of focal densities?
Anchoring of actin and myosin to the cytoplasm and cell membrane in smooth muscle
What initiates contraction of smooth muscle?
Stretch
What modulates contraction of smooth muscle?
Autonomic NS and/or hormonal stimulation
