Muscles Flashcards
Special characteristics of muscle tissue
- excitability
- Contractility
- Extensibility
- Elasticity
4 functions of muscle
- Produces movement
- Maintains posture
- Stabilizes Joints
- Generates heat
Excitability
Also called responsiveness, ability to receive and respond to stimulus
Contractility
Ability to shorten forcibly, sets muscle apart from other tissue types
Extensibility
Ability to extend or stretch
Elasticity
Ability of muscle cell to recoil and resume it’s resting length after stretching
3 types of muscle tissues and there similarities and differences
- Skeletal muscle: cells called muscle fibers, have striations, voluntary
- Cardiac muscle: striated, involuntary
- Smooth muscle: no striations, visceral, involuntary
Name of the plasma membrane of a muscle cell
Sarcolemma (muscle husk)
Muscle cell cytoplasm
Sarcoplasm
Connective tissue sheaths of a muscle
- Epimysium
- Perimysium and fascicles
- Endomysium
Epimysium
Overcoat of DICT surrounding the whole muscle
Perimysium
Surrounds each fascicle, made of fibrous connective tissue
Endomysium
CT that surrounds each muscle fiber
Parts of a muscle
- epimysium
- Perimysium
- Endomysium
- Tendons
- Fascicles
- Nerves and blood vessels in the muscle
When a muscle contracts, the movable bone
The insertion moves towards the orgin
Insertion
Movable part of the muscle
Origin
Less movable part of the muscle
Direct attachment
(Fleshy attachment) the epimysium of the muscle is fused with a periosteum or perichondrium
Indirect attachment
Extends bruin muscle as a tendon or aponeurosis
Aponeurosis
Sheet like ct that connects muscles to a bone, cartilage or other muscles
Why are muscle fibers multinucleate?
The muscle cells fuse together
Myofibrils
Individual fiber in the muscle cell made up of sarcomeres
A bands
A dark band on a myofibril
I band
Light band on a myofibril
Saracomere
The smallest contractile unit of a muscle, myofibril a are made up of sarcomeres. A sarcomere is a section of a myofibril
Organizational and structure level of a muscle from organ to molecular structure
- Muscle
- Fascicle
- Muscle Fiber (cell)
- Myofibril
- Sarcomere
- Myofilament
Myofibril
Organelle of the muscle fiber made up of sarcomeres which contract; an organelle
Types of filaments in a sarcomere
- Myosin (thick filaments)
- Actin (thin filaments)
- Titin (elastic filaments)
Sarcolemma
Plasma membrane of a muscle fiber
Sarcoplasm
Cytoplasm of a muscle cell
Difference between fibers, myofibrils, and filaments
Fibers= cells, myofibrils= organelle, filaments= extended macromolecular structure
Z disc
Boundary of each sarcomere
A band
Width of myosin
I band
Area with NO myosin, overlaps 2 neighboring sarcomeres
H zone
Middle of the band that doesn’t have actin
M line
Very center of the myosin
Titin
Helps muscle cell to spring back to shape after stretching. Stiffens as it uncoils to prevent the sarcomeres from being pulled apart
Two sets of intracellular tubules
Sarcoplasmic reticulum and T tubules
Sarcoplasmic reticulum
Modified smooth endoplasmic reticulum that stores calcium ions and releases them on demand when the muscle fiber is stimulated to contract
Muscle contraction
- Nerve impulse travels down neuron
- Axon terminal releases a neurotransmitter
- NT diffuses through synaptic cleft (little gap) and binds to sarcolemma
- Sarcoplasmic reticulum releases calcium ions which causes the myosin heads to to bind to the actin, ATP is then used to bend the myosin heads inwards
- these two things cause actin to get pulled towards the center of the sarcomere
- A band has not changed
- I band shrinks to the size of Z disc
- Hzone disappears
Sliding filament mechanism/ theory
Myosin and actin do not get shorter, they are just sliding over each other. Shortening the sarcomere
Muscle extension
Muscles do not forcibly lengthen. Gravity can pull a muscle back to its original length
- contracting a muscle on the opposite side of a joint can pull a muscle back to its original length
Motor unit
A neuron and all the muscle fibers that it innervates
- a muscle produces more or less force by using more or fewer motor units
- an individual motor unit can be very large (lots of muscle fibers per neuron) or very small (vice versa) nuance movements of facial muscles
Large motor units
Produce big movement and lots of force