Unit One - Neuromuscular Physiology Flashcards
Sarcolemma
plasma membrane covering the muscle cell
myofibrils
a small, string-like structure within a muscle fiber containing the contractile proteins; may be referred to as a fibril
Sarcoplasm
protoplasm, contains, in addition to the contractile material, proteins, fats, glycogen, nuclei, mitochondria, and enzymes
Epimysium
Connective tissue that combines and groups secondary bundles to form tertiary bundles. Tertiary bundles consist of larger structures such as major arteries, veins, and nerves. This connective tissue is usually referred to as fascia
perimysium
Connective tissue that combines and groups the primary bundles to form secondary bundles. Secondary bundles can contain arterioles, venules, nerve branches, and lymph ducts.
Endomysium
Connective tissue that combines 8 to 12 fibers (cells) together in order to form a primary bundle. Primary bundles contain nerve fibers individually innervating muscle fibers and capillaries that run along fibers.
Sarcomere
Functional unit of muscle, go from z-line to z-line (Zweischen line)
Z-line
Separates sarcomeres, or functional unit of muscle. In between sarcomeres and defines the start and end of the muscle unit.
actin
thin filaments attaching to the ends (Z-lines) of the sarcomere (actin is 20%-25% of protein in muscle). Extend from Z-line to H-zone. Double helix.
myosin
thick filaments encompassing the center of the sarcomere, (makes up 50-55% of protein in muscle). Myosin extends the length of the A band -which never changes sizes during contraction. There are two parts:
Light meromyosin - a protein composing the ‘tail’ of the filament
Heavy meromyosin - a protein composing the ‘head’ of the myosin filament
troponin
a small protein on the surface of the actin that regulates the interaction between actin and myosin. Troponin prevents interaction between actin and myosin.
tropomyosin
A long protein structure in the helix of the actin filament that precents interaction between actin and myosin by covering up the active sites for mysoin heads to bind to on the actin filament. Thus, preventing cross-bridges from forming.
cross-bridges
extensions of the heavy meromyosin between the myosin and active filaments.
sarcoplasmic reticulum
The conduction system of the muscle cell. Stores the Ca++ needed for muscle contraction.
synaptic vesicles
packets of transmitter substance (Acetylcholine). vesicles are released into synaptic cleft due to depolarization wave reaching axon terminal. Then, they enter the muscle fiber.
Ca++
Ca++ is released by sarcoplasmic reticulum due to action potential. In the presence of Ca++, troponin causes a confirmational change in tropomyosin, moving it to the helix and thus exposing active binding sites for heavy meromyosin (myosin head) to form cross-bridges with actin and create muscle contraction.
transverse tubules
pass through muscle cell, contact with sarcoplasmic reticulum forms triads which provide contact between the inside of the cell and fluids bathing it.
motor neruons
a neuron located in the spinal cord that innervates muscle fibers.
synapse
a junction between two nerve cells, consisting of a minute gap across which impulses pass by diffusion of a neurotransmitter.
axon
the long threadlike part of a nerve cell along which impulses are conducted from the cell body to other cells. Insulated by myelin sheath. one of the three regions of a motor neruon
dendrites
Another region of motor neuron. short branched extensions of a nerve cell, by the cell body, along which impulses received from other cells at synapses are transmitted to the cell body.
muscle biopsy
A muscle biopsy is a procedure that removes a small sample of tissue for testing in a laboratory. The test can help your doctor to see if you have an infection or disease in your muscles. A muscle biopsy is a relatively simple procedure. This can also distinguish how much type I vs II muscle fiber type you have. The biopsy needle is fairly large but you are numbed before procedure. needle consists of three parts
hypertrophy
Increase in size of existing muscle fibers -therefore muscle gets larger
hyperplasia
Increase in number of muscle fibers - therefore muscle gets larger
atrophy
Muscle atrophy is defined as a decrease in the mass of the muscle; it can be a partial or complete wasting away of muscle, and is most commonly experienced when persons suffer temporary disabling circumstances such as being restricted in movement and/or confined to bed as when hospitalized.
action potential
Progressive polarity change along membrane length. This includes a period of depolarization (the reversal of polarity and repolarization (the re-establishment of polarity)). Sometimes action potential is referred to as depolarization wave.
motor endplate
The nerve and muscle fiber areas that permit transfer of a nerve impulse from the nerve to the muscle
myoneural junction
A neuromuscular junction (or myoneural junction) is a chemical synapse formed by the contact between a motor neuron and a muscle fiber. It is at the neuromuscular junction that a motor neuron is able to transmit a signal to the muscle fiber, causing muscle contraction. Interface between muscle and nerve
motor unit
A functional unit of muscle contraction. Consists of the motor neuron and the muscle fibers that it innervates
proprioceptor
a sensory receptor that receives stimuli from within the body, especially one that responds to position and movement. In order to detect body’s relative position to space/objects around the body. General state of body awareness in the resting state.
muscle spindle
main skeletal muscle receptor and is responsible for the stretch reflex. It continually provides info to the central nervous system regarding muscle strength muscle length, rate of change of muscle length.
monosynaptic reflex
When a muscle is stretched, the annulospiral endings are elongated which sends a signal via action potential to spinal cord to directly stimulate motor neuron pool, thus causing contraction. This contraction is a protective mechanism of muscle to prevent damage from stretching. Ex. knee jerk during reflex test. Also, walking on sidewalk and ankle twisting off curb and then righting yourself.
golgi tendon organ
receptive to tension generated in the tendon. Sensitive to stress (in opposition to stretch). If there is too much stress in tendon, than there is an increase rate of action potential from golgi tendon organ which stimulates inhibitory internueron in order to stop action potential from motor neruon pool to relax muscle.
joint receptors
Mechanoreceptors (also along with golgi tendon organ, and muscle spindle), receptors sensitive to metabolites from metabolism. May elicit increases in cardiovascular parameters.
temporal summation
Increase in stimulation frequency at which motor units contract in order to increase the force.
spatial summation
Increase in the number of motor units contracting to increase force.
mechanical work
Defined as a force multiplied by a distance. For example, someone can push on a brick wall, exert a force, and wall will never move, thus no work is ever done.
isometric contraction
A contraction during which muscle generates force while maintaining a constant length.
isotonic contraction
In which muscle applies a force while the segment moves through its full range of motion or part of it. There are two types:
concentric - muscle shortens
eccentric - muscle lengthens while resisting an outside force. These can generate the greatest amount of force.
isokinetic contraction
muscle contracts moving the limb at a single velocity. Thus, velocity of shortening remains constant. These may be concentric or eccentric. These are not natural contractions and therefore require special equipment (biodex) to be performed.
inhibition
the golgi tendon organ is a mechanoreceptor that detects stress. In order to prevent muscle from being damaged, when there is a lot of stress, GTO will increase rate of action potential to stimulate an INHIBITORY internueron to reduce or stop action potential from motor neuron pool in order to relax muscle. When first lifting weights, the GTO will be hard at work to protect muscles. However, as a lifter becomes more experienced, the GTO will learn to inhibit its inhibitor to allow a larger contraction, more stress, to lift weight safely.
somatic nervous system
Voluntary nervous system. Ex. nerves that innervate skeletal muscle for voluntary control.
autonomic nervous system
Involuntary nervous system (autonomic NS). Body uses these nerves to regulate cellular, tissue, and organ functions. This is split up into the parasympatheic and sympathetic nervous system.
length-tension relationship
Force of a maximal concentric contraction depends on the length of the muscle. Muscle length influences tension development because excessive stretch and inadequate length decrease actin and myosin interaction
force-velocity relationship
Skeletal muscle tension development is also known to vary with the velocity of the shortening. Greatest tension development occurs at zero shortening velocity (isometric) contractions. Force during maximal isometric contractions is called maximal voluntary contraction (MVC) force. As contraction velocity increases, maximal tension development decreases
Type I
Also known as type A or a slow twitch oxidative muscle.
Type II
Also known as type B or a fast twitch glycolytic
Slow-twitch
oxidative. aerobic. slow to fatigue. red fiber color
Fast-twitch
glycolytic. anaerobic. quick to fatigue. white fiber color
cerebellum
Essential for coordination and correction of rapid motor patterns, prepares future motor patterns, stores correct movement sequences.
basal ganglia
Also helps execute motor plan. While cerebellum is excitatory, basal ganglia is inhibitory. Secretes neurotransmitters for inhibiting. When there is a disorder than you cannot sit still and be quiet. I.e. parkinsons.
