Flashcards in Exam 2 Part one Deck (102):
Skeletal muscle cells are referred to as muscle fibers because of their length. All muscle tissue is composed of muscle cells & exhibits certain common properties: excitability, contractility, elasticity, extensibility
Each skeletal muscle is composed of fascicles, which are bundles of muscle fibers
The innermost connective tissue layer. It surrounds & electrically insulates each muscle fiber. Has reticular fibers to help bind together neigboring muscle fibers
Surrounds the fascicles. Dense irregular connective tissue sheath. It contains arrays of blood vessels & nerves that branch to supply each individual fascicle
A layer of dense irregular connective tissue that surrounds the whole skeletal muscle
Connective tissue layers merge to form fibrous tendon at the ends of the muscle, which attaches the muscle to bone, skin or another muscle. Usually have a thick cordlike structure
When tendons form a thin, flattened sheet
Upon contraction, one muscle moves, while the other remains fixed. The less mobile attachment of a muscle is called it's origin
The more mobile attachment of a muscle
Usually the insertion of a muscle is pulled towards?
Plasma membrane of a muscle fiber. Surrounds muscle fiber and regulates entry and exit of materials
Transverse (T) Tubules are
Deep invaginations of the sarcolemma that extend into the sarcoplasm a of the skeletal muscle fibers as a network of narrow membranous tubules. Quickly transport a muscle impulse from the sarcolemma throughout the entire muscle fiber
Internal membrane complex. Smooth endoplasmic reticulum. Stores calcium ions needed for muscle contraction
Expanded ends of the sarcoplasmic reticulum that are in contact with the transverse tubules. Site of calcium ion release to promote muscle contraction
Together, the two terminal cisternae and the centrally placed T-tubule form a structure called a triad
When some myoblasts do not fuse with muscle fibers during development, they remain in adult skeletal muscle tissue as satellite cells
When are satellite cells useful?
If a skeletal muscle is injured, some satellite cells may be stimulated to differentiate & assist in its repair & regeneration
Myofibrils consists of bundles of short myofilaments. It takes many successive groupings of myofilaments to run the entire length of a myofibril
The bundles of myofilaments are classified as?
Thin myofilaments (thin filaments) & thick myofilaments (thick filaments)
Thick filaments are
Fine protein myofilament composed of bundles of myosin. They bind to thin filament & cause contraction
Thin filaments are
Fine protein myofilament composed of actin, troponin, & tropomyosin. The thick filaments bind to it & cause contraction
A double-stranded contractile protein. Binding site for myosin to shorten a sarcomere
Double stranded regulatory protein. Covers the active sites on actin, preventing myosin from binding to actin when muscle fiber is at rest
Regulatory protein that holds tropomyosin in place & anchors to actin. When calcium ions bind to one of its subunits, troponin changes shape, causing the tropomyosin to move off the actin active site, this permits myosin binding to actin
Thick filaments are assembled from bundles of the protein myosin. Each myosin molecule in a thick filament consists of 2 strands; each strand has a free globular head & an attached, elongated tail. The myosin molecules are oriented on either end of the thick filament so the long tails point toward the center of the filament & the heads toward the edges & project outward toward the surrounding thin filaments
Cross-bridges are formed when?
During a contraction, myosin heads form cross bridges by binding thick filaments to actin in the thin filaments
A bands are
Dark bands. Contain the entire thick filament.
At either end of a thick filament is?
A light band region occupied by thin filaments that extend into the A band between the stacked thick filaments
I bands are
Light bands. Contain thin filaments but no thick filaments. They have protein filaments called titin
Also called Z disc. A thin transverse protein structure in the center of the I band that serves as an attachment site for thin filament ends
H zoned is
Also called the h band. A light, central region in the A band. Lighter shaded because only thick filaments are present. At maximal contraction, the thin filaments are pulled into this zone, and the H zone disappears
Called the A bands
Called the I bands
The functional contractile unit of a skeletal muscle fiber. Defined as the distance from one z disc to the next adjacent z disc
Sliding filament theory is
When a muscle contracts, thick and thin filaments slide past each other, and the sarcomere shortens
Neuromuscular junction is
The point where a motor neuron meets a skeletal muscle fiber
Motor neuron activity stimulates what?
Skeletal muscle contraction
What are the components of a neuromuscular junction?
1) Synaptic knob
2) Synaptic vesicle
3) Acetylcholine (ACh)
4) Motor end plate
5) Synaptic cleft
6) ACh receptors
7) Acetylcholinesterase (AChE)
Motor end plate is
Specialized region of the sarcolemma. Has folds & indentations to increase membrane surface area covered by the synaptic knob
Synaptic knob is
Of the neuron is an expanded tip of an axon. When it nears the sarcolemma of a muscle fiber, it expands further to cover a large surface area of the sarcolemma. A nerve impulse travels through the axon to the synaptic knob
Synaptic cleft is
A narrow space separating the synaptic knob & the motor end plate
Acetylcholine (ACh) is
Molecules of the neurotransmitter that are housed within synaptic vesicles (small membrane sacs) that are housed in the synaptic knob cytoplasm
Acetylcholinesterase (AChE) is
An enzyme which resides in the synaptic cleft. It rapidly breaks down molecules of ACh that are released into the synaptic cleft
AChE is need so that?
ACh will not continuously stimulate the muscle
Motor unit is
Composed of a single motor neuron and all of the muscle fibers it controls. Typically controls only some of the muscle fibers in an entire muscle
All or none principle
States that a muscle fiber either contracts completely or does not contract at all.
Red pigment. A globular, oxygen binding, reddish-appearing protein that is structurally related to hemoglobin
The oxygen binding protein in erythrocytes
A metabolic reaction that does NOT require oxygen
What is required for the production of the maximum amount of ATP?
What happens during muscle atrophy?
A wasting of tissue that results in a reduction in muscle size, tone, & power
What happens during hypertrophy?
An increase in muscle fiber size. An increase in the number of myofibrils per fiber in fast fibers
Why might atrophy be permanent?
When extreme atrophy occurs, the loss of gross muscle function is permanent
The muscle fibers are concentrically arranged around an opening or recess. Called a sphincter because contraction of the muscle closes off the opening
Parallel muscle (shape)
The fascicles run parallel to its long axis. Each muscle fiber exhibits the functional characteristics of the entire parallel muscle. They have central body called the belly or gaster
Transmits motor information
Motor nervous system
Makes myelin sheaths in CNS
Stain darkly with basic dyes
Side branches of axons
Respond to CNS infection
Neurons with multiple dendrites
Sensory to motor neuron communication
Uses a neurotransmittter
Neuron part that usually receives incoming impulses
Skeletal muscle fiber
The cell body of a mature neuron does not contain
Neurons that have only two processes attached to the cell body are called?
Which neurons are located ONLY within the CNS?
A structure or cell that collects sensory information is a?
The glial cells that help produce CSF in the CNS are?
Is the neurolemmocyte a part of the CNS?
Which of these cells transmits, transfers, & processes a nerve impulse?
1) Small in diameter
2) Contract slowly
3) Specialized to continue contracting for extended periods of time
4) Vascular supply more extensive than network of capillaries around fast fibers
5) Supply of nutrients & O2 increased
6) Called red fibers because they contain red pigmented myoglobin
7) Resting slow fibers contain O2 reserves that can be used during contraction to provide needed ATP
8) Large # of mitochondria which permits them to produce more ATP than fast fibers while contracting, making it less dependent on anaerobic metabolism
9) Requires O2 to produce ATP
10) Metabolic reactions termed aerobic
1) Exhibit properties that are between slow & fast fibers
2) Contract faster than slow & slower than fast fibers
3) Resemble fast fibers
4) Greater resistance to fatigue
5) Require O2 to produce ATP
1) Large in diameter
2) Contain large glycogen reserves
3) Densely packed myofibrils
4) Few mitochondria
5) Called white fibers because they are pale in color due to lack of myogloblin
6) Majority of skeletal muscle fibers in the body are fast
7) Fast because of their contraction
8) Produce powerful contractions because of the large amount of sarcomeres
9) Contractions uses vast quantity of ATP
10) Primary activity supported by Anaerobic metabolic reactions
11) Fatigue rapidly
Considering "the all-or-none" rule of muscle contraction, how is it that we are able to have smooth and refined body movements?
What are the various functions of the muscular system?
1) Body Movement
2) Maintenance of Posture
3) Temperature Regulation
4) Storage and movement of Materials
6) Respiration due to movements of the muscles of the thorax
7) Heartbeat (muscle contraction)
Decreased levels of Ach
What stimulates skeletal muscle contraction?
The motor neuron activity
When does muscle contraction begin?
Begins when a nerve impulse stimulates an impulse in a muscle fiber
Each muscle fiber is controlled by?
One motor neuron
The motor neuron transmits the effect of a nerve impulse to the muscle fiber at a?
Thin filaments are
1) Primarily composed of two strands of the protein actin
2) Two regulatory proteins, tropomyosin & troponin
The tropomyosin (protein) molecule in the thin filaments are
A short, thin, twisted filament that covers small sections of the actin strands
The troponin protein in the thin filament of the sarcomere has 3 functions
1) Structurally, it attaches to actin to anchor itself in place
2) Attaches to tropomyosin to hold it in place over the surface of the actin
3) Functionally, it provides a binding site for calcium ions
Thick filaments are
1) Twice size as thin filaments
2) Assembled from bundles of the protein myosin
Myosin in the thick filament of a sarcomere consists of?
Two strands; each strand has a free, globular head & an attached, elongated tail. The tails point toward the center of the filament & the head toward the edge & project outward. During contraction the heads form cross bridges by binding thick filaments to actin in the thin filaments
A bands are
Dark bands, contain entire thick filament
I bands are
Light region, contain thin filaments (no thick). Also contain protein filaments called titin
Titin found in the I band of a sarcomere plays a role in...
Muscle elasticity & control of thick filament assembly, & passive stiffness generated in the muscle
What are the 3 types of skeletal muscle fiber
1) Slow (Type I slow oxidative)
2) Intermediate (type II-A, fast aerobic)
3) Fast (Type I-B, fast anaerobic)
The epineurium is
A thick, dense irregular connective tissue layer enclosing the nerve
Has nuclei for CN III & CN IV
Autonomic centers for heart rate & respiration
Dura mater fold between cerebral hemispheres
Innervates most thoracic/abdominal organs
Contains the motor speech area
Contains the primary auditory cortex
Innervates lateral rectus
Responsible for involuntary arm swinging
Visual reflex centers