Term 1 Exam: Skeletal Muscle Tissue from Chapter 10/11 Muscular Tissue Flashcards
Motion is the body is the result of what?
alternating contraction (shortening) and relaxation of muscles
How much of body mass is approximated to be muscular tissue?
~45%
What are four major functions of muscles?
- Producing body movement - with bones providing leverage
- Stabilizing body position
- Storing and moving substances within the body- regulates organ volumes/ move blood, lymph, air, liquids, and nutrients/ store glycogen, protein
- Producing Heat - byproduct of friction/excess energy
What are four major properties of muscle tissue?
- Electrical excitability - capacity of muscle fibers to respond to motor nerve impulses
- Contractility - ability to contract forcefully in response to nerve impusle
- Extensibility - ability of muscle to stretch without being damaged
- Elasticity - ability to return to original shape after contraction or extension
What are three types of muscle tissue?
- Skeletal muscle tissue
- Cardiac Muscle tissue
- Smooth Muscle tissue
What are three functions of skeletal muscle tissue?
- Move bones (some skin and soft tissue)
- Striated (microscopic bands)
- Primarily voluntarily controlled
What are three functions of Cardiac Muscle?
- Forms most of the wall of the heart
- Striated and branched
- Involuntary and some cells are autorhythmic (regulated by ANS)
What are two characteristics about Smooth muscle tissue?
- Found in walls of tubes (blood vessels, GI)
2. Unstriated and involuntary
How is skeletal muscle organized?
Skeletal muscle bundle consists of a body (belly) connected by tendons to the skeleton
What are tendons?
- Composed of dense regular connective tissue (parallel arrangements of collagen fibres)
- Connects muscle belly to bone
What are the three layers of connective tissue covering Skeletal Muscle?
- Endomysium
- Perimysium
- Epimysium
Where is the endomysium found?
Surrounds muscle fibres
-holds muscle fibers together while loose enough for movement
Where is perimysium found?
Surrounds muscle fascicles (bundles)
-Houses blood vessels and nerves within fascicles
Where is epimysium found?
Binds all fascicles together to form the belly
What are three types of fasciae? Brief description of each.
- Superficial fascia - subcutaneous layer of the integument
- Deep fascia :
- Lies interior to the SubQ layer
- Large sheet of dense irregular connective tissue
- binds together muscles of similar functions
- cushions muscle layers - Subserous fascia:
- Separates the deep fascia from membranes that line the thoracic and abdominal cavities
In embryogenic development, how are skeletal muscle fibres formed?
myoblasts fuse lengthwise
What are three important characteristics of Skeletal Muscle fiber?
- Multiple nuclei
- Muscle fiber does not multiply
- Muscle fibers form prior to birth and last a lifetime (muscle growth is from hypertrophy (increased cell size) not hyperplasia (increased number of cells))
What are satellite cells?
Muscle cell that is capable of division
- able to fuse with one another or damaged muscle fiber
- muscle regeneration by satellite cells is limited
What is sarcolemma?
plasma membrane of a skeletal muscle fibre
What are T-Tubules?
3
- Extensions of the sarcolemma that tunnel throughout the muscle fiber
- open to the outside
- filled with interstitial fluid
What is sarcoplasma?
cytoplasm of a skeletal muscle cell
What are Myofibrils (2)?
- nonmembrane-bound organelles
2. extends the entire length of muscle fibre
What is the Sarcoplasmic Reticulum (SR)?
3
- Smooth endoplasmic reticulum of muscle cell
- Stores Calcium
- Calcium release (into sarcoplasm) couples electrical excitation to muscle contraction
What are myofibrils made of?
Thick and thin filaments
What is the sarcomere?
the functional unit of contraction
-compartment of precisely arranged thick and thin filaments
Myofibrils are built from 3 types of protein, what are they?
- Contractile Proteins
- Regulatory Proteins
- Structural Proteins
What is the function of contractile proteins in myofibrils?
- generate force during contraction by sliding past each other - leads to shortening of the fibre
- myosin and actin
What is the function of regulatory proteins in myofibrils?
Help switch the contraction process on or off
-troponin and tropomyosin
What is the function of structural proteins in myofibrils?
Keep think and thin filaments in proper alignment
- supply elasticity and extensibility
- links myofibrils to sarcolemma and extracellular matrix
What are the two main contractile proteins?
- Myosin
2. Actin
What are 2 characteristics of myosin?
- the major component of thick filaments
2. Myosin is a molecular motor protein that converts chemical energy (ATP) into mechanical energy
What are 2 characteristics of actin?
- the major component of thin filaments
2. Binds to myosin at the actin binding site
What two regulatory proteins do the thin filaments contain and what is their function?
- troponin
- tropomyosin
- regulate the interaction between actin and myosin
Most skeletal muscles receive ______ nerve(s) that supply/supplies them with motor and sensory functions
One nerve supplies
as opposed to other muscles (ie sheetlike muscles of body wall) which receive multiple nerves
Where do nerves typically enter a muscle?
With blood vessels as a unit called a “neuromuscular bundle”
-these nerves carry both sensory and motor information
What are somatic motor neurons?
Individual cells (neurons) that innervate skeletal muscle fibres
What is the neuromuscular Junction (NMJ)? (3)
- a point of near-contact between a somatic motor neuron and a skeletal muscle fibre
- each muscle fiber has one NMJ
- The axon of a somatic motor neuron branches out and forms NMJ’s with many different muscle fibres
What is a Motor unit?
One somatic motor neuron plus all the skeletal muscle fibres it stimulates
