Exam 3: Ch. 10-15 Flashcards
Fascia
A band or sheet of connective tissue beneath the skin that attaches, stabilizes, encloses, and separates muscles and other internal organs
Made primarily of collagen
Muscle Fascicle
A bundle of skeletal muscle fibers surrounded by perimysium
What are the three types of interstitial connective tissues found in muscles
Epimysium - Surrounds the entire muscle
Perimysium - Surrounds bundles of muscle fibers
Endomysium - Surrounds individual muscle fibers
Organization of muscle fibers (different types of muscles)
Fusiform - Spindle-shaped muscles that are tapering on both ends
Parallel - Characterized by fascicles that run parallel to one another. The contraction of a parallel muscle is similar to the contraction of a single muscle fiber
Triangular - A flat muscle with a broadband origin and a narrow point of insertion. Shaped like a paper fan
Unipennate - A pennate muscle in which the muscle fibers or fascicles are all on one side of the tendon
Bipennate - A pennate muscle with two rows of muscle fibers facing in opposite diagonal directions with a central tendon, similar to a feather. Allows for lots of power but less ROM
Multipennate - A pennate muscle with fibers arranged at many different angles in relation to the axis of force generation
Circular - Muscles that typically encircle an orifice or object
What is an example of a fusiform muscle?
Biceps Brachii
What is an example of a parallel muscle?
Rectus Abdominis
What is an example of a triangular muscle?
Pectoralis Major
What is an example of a unipennate muscle?
Palmar Interosseous
What is an example of a bipennate muscle?
Rectus Femoris
What is an example of a multipennate muscle?
Deltoid
What is an example of a circular muscle?
Orbicularis Oculi
Beyond movement, what benefits do humans get from facial muscles?
Non-verbal communication (facial expressions)
Emil Heinrich Du Bois-Reymond
Founder of modern electrophysiology in muscle and nervous tissue
Developed a way to demonstrate the Neuromuscular Junction
Controversy with “Frankenstein” because of the electrical current used to manipulate muscles
Within a muscle cell (fiber) what are the two types of fibers that compose the cell and give it striations?
Actin Fibers - Thin filaments
Myosin Fibers - Thick filaments
What is a unique feature of muscle cells?
Multiple nuclei are present because individual precursor cells have fused together. The existence of multiple nuclei, however, is very beneficial because it enhances protein organization and production within the cell.
Within a muscle cell, what is the function of Dystrophin?
Dystrophin is a protein that connects the border of the thick and thin filaments with the PLB to allow contraction of the entire cell rather than just the filaments.
Muscular Dystrophy
People with muscular dystrophy have developed deficits related to dystrophin protein development, presence, or function.
It causes weakness in the ability to contract muscle tissue, if the ability is present at all
H-Zone
The space between columns of actin fibers
Z-disc
The space where two columns of actin fibers connect
I-band
The space between columns of myosin fibers
A-band
The region that represents the span of a myosin fiber columns
M-line
Represents architectural fibers that position and arrange the myosin fibers
Titin Filaments
Elastic filaments that allow the distal ends of the myosin to connect to the Z-disc
Level of Organization for Muscles (Large - Small Structures)
Largest
- Muscle
- Muscle Fascicles
- Muscle Fibers
- Myofibril
- Muscle Filaments
Smallest
Components of Myosin Filaments
Head - Each myosin molecule has two heads
Flexible Hinge Region - Each tail has a flexible region just before the head that allows the heads to bend and reach toward the actin filament
Tail - Each myosin molecule has two tail regions that twist together
Components of Actin Filament
Actin Beads - Two separate strands of actin beads wrap around each other to form a strand of the actin filament.
Tropomyosin - Spaghetti-like strands of binding protein that organize actin beads into a strand
Troponin Complex - Molecules that hold the position and integrity of both the actin beads and the tropomyosin.
What happens to the H-zone during muscle contraction?
The H-zone is eliminated as the columns of myosin and actin filaments are brought closer together
Neuromuscular Junction (NMJ)
A living tissue connection between the nervous system and the muscular system
Structure of the NMJ
The distal ends of a neuron called the AXON TERMINALS, come into contact with a muscle fiber and release a chemical signal called a NEUROTRANSMITTER that chemically stimulates action at the site of contact.
Acetylcholine
The primary neurotransmitter for NMJs formed with skeletal muscle
Sarcoplasmic Reticulum
The membranes that surround myofibrils
Structures of the Sarcoplasmic Reticulum
T-tubule & Terminal Cistern - Both structures are important in regard to the effects of the neurotransmitters released by the NMJ. The T-tubule is a thinner band running perpendicular to the myofibrils and the Terminal Cisterns are the tissues surrounding the T-tubules.
Process of chemical stimulation by the NMJ
- Action potential arrives at the axon terminal
- Voltage-gated Calcium channels open, allowing Ca2+ to enter the axon terminal
- Ca2+ entry causes Acetylcholine (ACh) to be released from synaptic vesicles via exocytosis
- ACh diffuses across the synaptic cleft and binds to receptors on the sarcolemma
- ACh binding opens ion channels in the receptors that allow both Na+ ions to enter and K+ ions to exit the muscle fibers.
- ACh effects are terminated once it breaks down in the synaptic cleft and diffuses away from the NMJ
Latent Period
The period of time between when the stimulus is received and when the muscle begins to generate tension.
How does Ca2+ affect muscle fibers & contraction?
Ca2+ binds to the Troponin Complex on the actin filament, causing it to move out of the way so that the Head of the myosin fiber can latch onto the myosin binding site of the actin bead