Week 4 // Muscular Tissue Flashcards
What are the 3 types of muscular tissue?
Skeletal muscle
Cardiac muscle
Smooth muscle
What is the function and location of skeletal muscles?
Skeletal, function is to move bones.
What is the function and location of cardiac muscles?
In heart, function is to pump blood.
What is the function and location of visceral (smooth) muscles?
various organs, various functions (ex. paristalsis)
What is the appearance of skeletal, cardiac and smooth muscle tissue?
skeletal: multi-nucleated and striated
cardiac: one nucleus, striated, intercalated disks
What are the functions of muscular tissue?
- Generating heat
- Producing body movements
- Stabilizing body positions
- Storing and mobilizing substances within the body
(In a less known but critically important role, muscle influences energy andprotein metabolismthroughout the body. Muscle is a primary site forglucose uptakeand storage, and it is also a reservoir of amino acids stored as protein.)
Properties of muscular tissue?
- Electrical excitability
- Contractility
- Extensibility
- Elasticity
How are muscles formed?
Myoblasts
How do skeletal muscles produce movements?
Skeletal muscles produce movements by exerting force on tendons
Tendons attach to and pull on bones, and movement occurs
What are Muscular Hypertrophy and Atrophy
Muscular Hypertrophy
Enlargement of existing muscle fibers
Due to increased production of myofibrils, mitochondria, sarcoplasmic reticulum and other organelles
Muscular Atrophy
Decrease in size of muscle fibers due to loss of myofibrils
Occurs as a result of aging or disuse
3 categories of muscle proteins
Contractile, Regulatory, Structural
Muscle Protein: Contractile
(ex: Myosin Actin)
Proteins that generate force during muscle contractions
Muscle Protein: Regulatory
(ex. Troponin and Tropomyosin)
Proteins that help switch muscle contraction process on and off.
Muscle Protein: Structural
(ex. Titin, Nebulin, Alpha-actin, Myomesin)
Proteins that keep thick and thin filaments of myofibrils in proper alignment, give myofibrils elasticity and extensibility, and link myofibrils to sarcolemma and extracellular matrix.
The Sliding Filament Mechanism
is a theory describing how muscles contract.
- Myosin pulls on actin, causing the thin filament to slide inward
- Consequently, Z discs move toward each other and the sarcomere shortens
- Thanks to the structural proteins, there is a transmission of force throughout the entire muscle, resulting in whole muscle contraction
Excitation-contraction coupling
Excitation-contraction coupling refers to the sequence of events by which an AP (an electrical event) in the sarcolemma of the muscle cell initiates the sliding of the myofilaments, resulting in contraction (a mechanical event).
Even at rest, the skeletal muscle exhibits a small amount of tension called _____
tone
Isometric and isotonic contractions
Isometric: A muscular contraction in which the length of the muscle does not change.
Isotonic: A muscular contraction in which the length of the muscle changes.
Types of skeletal muscle fibres
Slow Oxidative (SO) Fibers (Slow twitch) Fast Oxidative–Glycolytic (FOG) Fibers (Fast twitch) Fast Glycolytic (FG) Fibers
Slow oxidative
slow twitch / slow contraction (break ATP down slowly)
aerobic
red
high fatigue resistance (running a marathon)
high mitochondria, myoglobin, capillaries
Primary functions of fibers:
Maintaining posture and aerobic endurance activities.
Fast-Oxidative-Glcolytic
fast-twitch / fast contraction (break ATP down quickly)
aerobic
pink
intermediate fatigue resistance
Primary functions of fibers:
Walking, sprinting.
Fast Glycolytic (FG) Fibers
Low ATP, energy by anaerobic glycolysis high glycogen stores white anaerobic fast contraction
Primary function of fibres:
Rapid, intense movements of short duration.
Skeletal vs cardiac vs. smooth location (not in ppt)
Cardiac muscle cells are located in the walls of the heart, appear striated, and are under involuntary control. Smooth muscle fibers are located in walls of hollow visceral organs, except the heart, appear spindle-shaped, and are also under involuntary control.
Cardiac muscles have the same arrangement as skeletal muscles but they also have _____ _______
intercalated discs
Intercalated discs contain _____ and ________ that allow muscle action potentials to spread from one muscle fibre to another
desmosomes and gap junctions
Cardiac cells contain more
mitochondria
Cardiac cells’ contractions last ____ longer than skeletal muscle contraction
10 to 15 times longer
Smooth muscle cells look different from cardiac cells i this way
Smooth muscle looks quite different than cardiac and skeletal muscle. It is thick in the middle, tapered on the ends, and is not striated. It can be arranged as either single-unit or multi-unit fibers.
Location of skeletal muscle
Most commonly attached by tendons to bones.
Location of cardiac muscle
Heart
Location of smooth muscle
Walls of hollow viscera, airways, blood vessels, iris and ciliary body of eye, arrector muscles of the hair.
Aging and Muscle Tissue
Between 30–50 years of age, about 10% of our muscle tissue is replaced by fibrous connective tissue and adipose tissue. Between 50–80 years of age another 40% of our muscle tissue is replaced. Consequences are:
Muscle strength and flexibility decreases
Reflexes slow
Slow oxidative fiber numbers increase
