Muscle Tissue Flashcards
What are the functions of muscle tissue?
Movement of body and fluids, maintain posture and position, maintain body temperature, support soft tissues and sphincters
What are the three types of muscle?
Skeletal, cardiac, smooth
Which muscle types have voluntary control?
Skeletal muscle
Which muscle types have involuntary control?
Cardiac and smooth muscle
Which muscle types appear striated?
Skeletal and cardiac
Which muscle types appear non-striated?
Smooth
What is the purpose of skeletal muscle?
Body movements and maintain posture
What is the purpose of cardiac muscle?
Pump blood through cardiovascular system
What is the purpose of smooth muscle?
Maintain visceral organ tone and movement; vasodilation and vasocontraction
What are the names for a single muscle cell?
Myocyte, myofiber, muscle fiber
What surrounds a single myofiber?
Endomysium - loose CT
What surrounds a fasicle?
Perimysium
What surrounds a collection of fasicles?
Epimysium - dense irregular CT
Describe the organization into a muscle?
Myofiber surrounded with endomysium then congregate to form fasicles (multiple myofibers) surrounded by perimysium and then multiple fasicles create a muscle that is surrounded by epimysium
What is the purpose of the CT in muscle?
CT sheaths are continuous with muscle tendons in order to transmit their contractile force to bone and they allow for passage of blood and nerves to the myofibers
Within a myofiber, the nuclei are located in the periphery of the cell, what houses the majority of the cytoplasm?
Myofibrils - contain actin and myosin filaments known as sarcomeres
What is the plasma membrane that surrounds the myofiber called and what is unique about it?
Sarcolemma, it has invaginations known as T-tubules that run between myofibrils in the cell
What sleeves cover each myofibril?
Sarcoplasmic reticulum that houses calcium
What forms the triad?
One T-tubule and 2 terminal cisternae that will cause muscle contraction
What is the terminal cisternae?
Dilated ends of the sarcoplasmic reticulum that release calcium in order for muscle to contract
What is a sarcomere?
Basic contractile unit consisting of thin actin microfilaments and thick myosin filaments
Z line to Z line
1 sarcomere
M line
Attachment site for thick myosin filaments ( in between z lines)
Z line
Attachment site for thin actin microfilaments
I band
Space containing only actin microfilaments
H zone
Space containing only myosin filaments
A band
Space where thin actin microfilaments overlap the thick myosin filaments and includes the H zone in between
Do thick and thin filaments change length?
NO!! Only change degree of overlap!
Describe the process of a sarcomere contracting
- Calcium comes in and binds troponin C, which causes tropomyosin to move the troponin complex (specifically troponin I off of myosin binding site)
- Myosin head binds the binding site on actin and power stroke invoked
- ATP binds myosin and hydrolyzes to release energy for myosin to release from actin and recock head
- Myosin binds actin, powerstroke, releases ADP and Pi
What is the power stroke?
When the myosin head moves actin filament toward M line and releases ADP & Pi
Rigor Mortis
When ATP source is lost, myosin cannot bind it, thus it is stuck bound to the actin filament and muscle is locked in place
What neurotransmitter is released from the axon terminal at the neuromuscular junction?
Acetylcholine
Describe how a myofiber releases calcium to the myofibrils
Motor neuron fires, the axon terminal releases vesicles containing acetylcholine across the synaptic cleft where they will bind to receptors on the sarcolemma and travel down the t-tubules. This will cause the terminal cisternae of the sarcoplasmic reticulum to release calcium to the myofibrils and cause muscle contraction
What is different about cardiac muscle?
One nucleus in center of cytoplasm, involuntary, straited but has intercalated discs, cells branch, not innervated, can be under hormonal control
What are the three types of intercalated discs?
Fascia adheren, desmosomes, gap (nexus) junctions
Which intercalated discs runs perpendicular to the striations?
Fascia adheren, desmosomes
What replaces the triad in cardiac muscle?
Diad - 1 t tubule and 1 terminal cisternae
What is different about smooth muscle?
Involuntary, non-striated, under control of ANS and hormones, one elliptical shaped nucleus
Which muscle type has a slow and sustained contraction/relaxation and is resistant to fatigue?
Smooth muscle
What anchors smooth muscle?
Dense bodies made of desmin and vimentin intermediate filaments
Cells communicate via gap junctions
