ch1 - structure and functions of body system Flashcards
approximately how many bones are in the body?
206
what does the axial skeleton consist of?
skull (cranium), vertebral column (vertebra C1 through the coccyx), ribs, and sternum
what does the appendicular skeleton include?
the shoulder (or pectoral) girdle (left and right scapula and clavicle); bones of the arms, wrists, and hands (left and right humerus, radius, ulna, carpals, metacarpals, and phalanges); the pelvic girdle (left and right coxal or innominate bones); and the bones of the legs, ankles, and feet (left and right femur, patella, tibia, fibula, tarsals, metatarsals, and phalanges)
what are fibrous joints and what kind of movement do they allow?
fibrous joints are e.g. sutures of the skull; they allow virtually no movement
what kind of joints are cartilaginous joints and what kind of movement do they allow?
cartilaginous joints are e.g. intervertebral disks and allow limited movement
what kind of joints are synovial joints and what kind of movement do they allow?
synovial joints are e.g. elbow and knee and they allow considerable movement
in terms of joints, what is the order of least to most movement allowed?
fibrous joints < cartilaginous joints < synovial joints
smooth hyaline cartilage covers what?
articulating bone ends
how does hyaline cartilage differ from other kinds of cartilage?
enclosed in a capsule filled with synovial fluid
how do uniaxial joints operate?
joints such as the elbow operate as hinges, essentially rotating about only one axis
joints such as the elbow are what kind of joint?
uniaxial
how is the knee improperly referred to?
often referred to as a hinge joint, but its axis of rotation actually changes throughout the joint range of motion
ankle and wrists are what kind of joints?
biaxial joints
what range of movements do biaxial joints (such as the ankle and wrist) allow?
movement about two perpendicular axes
shoulder and hip ball-and-socket are what kind of joints?
multiaxial joints
what kind of movement do multiaxial joints allow?
movement about all three perpendicular axes that define space
how are vertebrae grouped?
into 7 cervical vertebrae in the neck region; 12 thoracic vertebrae in the middle to upper back; 5 lumbar vertebrae, which make up the lower back; 5 sacral vertebrae, which are fused together and make up the rear part of the pelvis; and 3 to 5 coccygeal vertebrae, which form a kind of vestigial internal tail extending downward from the pelvis.
what does epimysium cover?
the body’s more than 430 skeletal muscles
what is the relationship of epimysium with tendons?
epimysium is contiguous with the tendons
what are tendons attached to?
tendon is attached to bone periosteum, a specialized connective tissue covering all bones
what is the diameter of muscle cells?
about 50 to 100 µm in diameter (about the diameter of a human hair)
how many fibers are in a fasciculi?
fasciculi may consist of up to 150 fibers
is endomyseum contiguous with skeletal muscle?
not quite, it is contiguous with the fiber’s membrane, or sarcolemma
what contiguity do the connective tissues (endo/peri/epi mysium) have in common?
they are all contiguous with the tendon, therefore tension developed in a muscle cell is transmitted to the tendon and the bone to which it is attached
what does the light I-band correspond with?
the areas in two adjacent sarcomeres that contain only actin filaments
where is the z-line located and what does it run through?
in the middle of the I-band running longitudinally through the I-band
where is the h-zone located?
in the center of the sarcomere
what is the composition of the h-zone?
only myosin filaments
how does the h-zone work during muscle contractions?
the h-zone decreases as the actin slides over the myosin toward the center of the sarcomere
what does the i-band do during contractions?
the I-band also decreases as the Z-lines are pulled toward the center of the sarcomere
where are the tubules sarcoplasmic reticulum located?
parallel to and surrounding each myofibril, and terminates as vesicles in the vicinity of the Z-lines
what is stored in the vesicles of the sarcoplasmic reticulum?
calcium ions; regulation of calcium controls muscular contraction
where are transverse tubules in relation to the sarcoplasmic reticulum?
perpendicular to the sarcoplasmic reticulum and terminate in the vicinity of the Z-line between two vesicles
why do action potentials arrive near-simultaneously from the surface to the depths of the muscle fiber?
because the T-tubules run between outlying myofibrils and are contiguous with the sarcolemma at the surface of the cell (when this happens calcium is released throughout the muscle and produces a coordinated contraction)
how do the actin filaments slide at each end?
inward on myosin filaments, pulling the Z-lines toward the center of the sarcomere and thus shortening the muscle fiber
what happens when actin filaments slide over myosin filaments?
both the H-zone and I-band shrink
why must rapid, repeated flexions must occur in many crossbridges throughout the entire muscle for measurable movement to occur?
because only a very small displacement of the actin filament occurs with each flexion of the myosin crossbridge
how much calcium is present in the myofibril at rest?
little calcium is present in the myofibril at rest, most of it is stored in the sarcoplasmic reticulum, therefore few of the myosin crossbridges are bound to actin (becomes strong when the actin binding site is exposed after release of the stored calcium)
in the excitation-contraction coupling phase, what must happen before myosin crossbridges can flex?
they must first attach to the actin filament
how does troponin affect the sarcoplasmic reticulum?
when the sarcoplasmic reticulum is stimulated to release calcium ions, the calcium binds with troponin, a protein that is situated at regular intervals along the actin filament and has a high affinity for calcium ions
where is tropomyosin?
runs along the length of the actin filament in the groove of the double helix
what occurs when calcium binds with troponin?
myosin crossbridge now attaches much more rapidly to the actin filament, allowing force to be produced as the actin filaments are pulled toward the center of the sarcomere
what is the amount of force produced by a muscle at any instant contingent on?
the number of myosin crossbridges bound to actin filaments cross-sectionally at that instant in time (to reiterate: the number of crossbridges that are formed between actin and myosin at any instant in time dictates the force production of a muscle.)
in the contraction phase of the excitation-contraction coupling phase, where does the energy for the power stroke come from?
from hydrolysis (breakdown) of adenosine triphosphate (ATP) to adenosine diphosphate (ADP) and phosphate, a reaction catalyzed by the enzyme myosin adenosine triphosphatase (ATPase)
what must occur for the head to detach from the active actin site and return to its original position?
another molecule of ATP must replace the ADP on the myosin crossbridge globular head; this allows the contraction process to continue (if calcium is available to bind to troponin) or relaxation to occur (if calcium is not available)
what other events in skeletal muscle besides contraction does calcium regulate?
glycolytic and oxidative energy metabolism, as well as protein synthesis and degradation
in the recharge phase, how does muscle shortening occur?
only when this sequence of events—binding of calcium to troponin, coupling of the myosin crossbridge with actin, power stroke, dissociation of actin and myosin, and resetting of the myosin head position—is repeated over and over again throughout the muscle fiber muscle
shortening can occur as long as what conditions are satisfied?
as long as calcium is available in the myofibril, ATP is available to assist in uncoupling the myosin from the actin, and sufficient active myosin ATPase is available for catalyzing the breakdown of ATP.
when does the relaxation phase occur?
when the stimulation of the motor nerve stops
what occurs chemically during the relaxation phase?
calcium is pumped back into the sarcoplasmic reticulum, which prevents the link between the actin and myosin filaments. relaxation is brought about by the return of the actin and myosin filaments to their unbound state.
what is the origin of the “twitch” in fast/slow twitch muscle fibers?
relaxation time
chemically, how are fast/slow twitch determined?
histochemical staining for myosin ATPase content; another more specific method is to quantify the amount of myosin heavy chain (MHC) protein; the nomenclature for this is similar to that with the myosin ATPase methodology
what makes type I/II fibers able to act that way?
difference in the ability of the fibers to demand and supply energy for contraction and thus to withstand fatigue
why do type I fibers have low force production?
low myosin ATPase activity; reverse for type II
how do type IIa and type IIx fibers differ?
mainly in their capacity for aerobic-oxidative energy supply; type IIa fibers have greater capacity for aerobic metabolism and more capillaries surrounding them than Type IIx and therefore show greater resistance to fatigue
how can muscular force be graded?
(1) through variation in the frequency at which motor units are activated, if a motor unit is activated once, the twitch that arises does not produce a great deal of force. (however, if the frequency of activation is increased so that the forces of the twitches begin to overlap or summate, the resulting force developed by the motor unit is much greater. This method of varying force output is especially important in small muscles, such as those of the hand.) (2) an increase in force through varying the number of motor units activated, a process known as recruitment. in large muscles, such as those in the thigh, motor units are activated at near-tetanic frequency when called on.
can fast twitch fibers be used for slow twitch purposes?
if additional force is needed, as in a sprint at the end of a race, the fast-twitch motor units are called into play to increase the pace; unfortunately, exercise at such intensity cannot be maintained very long
where are proprioceptors located?
within joints, muscles, and tendons
what does the sensitivity to pressure and tension do?
relay information concerning muscle dynamics to the conscious and subconscious parts of the CNS
what is the kinesthetic sense?
conscious appreciation of the position of body parts with respect to gravity
is proprioception more conscious or unconscious?
unconscious so we do not have to dedicate conscious activity toward tasks such as maintaining posture or position of body parts.
what is the word for normal muscle fibers?
extrafusal fibers
what are muscle spindles?
proprioceptors that consist of several modified muscle fibers enclosed in a sheath of connective tissue
what are intrafusal fibers?
modified proprioceptive muscle fibers that run parallel to the normal, or extrafusal, fibers.
what do muscle spindles do?
provide information concerning muscle length and the rate of change in length; when the muscle lengthens, spindles are stretched
how is the sensory neuron of muscle spindles activated?
through deformation; the activation sends an impulse to the spinal cord, where it synapses (connects) with motor neurons, which results in the activation of motor neurons that innervate the same muscle
in another sense, what do muscles indicate?
the degree to which the muscle must be activated in order to overcome a given resistance – as a load increases, the muscle is stretched to a greater extent, and engagement of muscle spindles results in greater activation of the muscle
how do muscles for precise movements deal with spindles?
they have many spindles per unit of mass to help ensure exact control of their contractile activity
where to tap for knee jerk reflex?
the tendon of the knee extensor muscle group below the patella stretches the muscle spindle fibers
how does the kneejerk tap work?
causes activation of extrafusal muscle fibers in the same muscle, and a knee jerk occurs as these fibers actively shorten, which then shortens the intrafusal fibers and causes their discharge to cease
where are GTOs located?
in tendons near the myotendinous junction
how are GTOs arranged?
in series – attached end to end with extrafusal muscle fibers
