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
when are GTOs activated?
when the tendon attached to an active muscle is stretched
what occurs during discharge of GTOs?
sensory neuron of the GTO synapses with an inhibitory interneuron in the spinal cord, which in turn synapses with and inhibits a motor neuron that serves the same muscle
what is the result of GTO synapsing?
a reduction in tension within the muscle and tendon
what is the difference between spindles and GTOs?
whereas spindles facilitate activation of the muscle, neural input from GTOs inhibits muscle activation
what can override GTOs?
the motor cortex
does the cardiovascular systen regulate acid-base functions?
yes
composition of heart?
two interconnected but separate pumps; the right side of the heart pumps blood through the lungs, and the left side pumps blood through the rest of the body. Each pump has two chambers: an atrium and a ventricle
functions of atria?
the right and left atria deliver blood into the right and left ventricles
functions of ventricles?
the right and left ventricles supply the main force for moving blood through the pulmonary and peripheral circulations, respectively
what are the tricuspid and mitral/bicuspid valves called?
atrioventricular [AV] valves
what do atrioventricular valves do?
prevent the flow of blood from the ventricles back into the atria during ventricular contraction (systole)
what are the semilunar valves?
the aortic and pulmonary vlave
what do the semilunar valves do?
prevent backflow from the aorta and pulmonary arteries into the ventricles during ventricular relaxation (diastole)
how do the semilunar valves open?
passively when a backward pressure gradient pushes blood back against it, and opening when a forward pressure gradient forces blood in the forward direction
what is the composition of the heart?
- the sinoatrial (SA) node—the intrinsic pacemaker—where rhythmic electrical impulses are normally initiated; 2. the internodal pathways that conduct the impulse from the SA node to the atrioventricular node; 3. the atrioventricular (AV) node, where the impulse is delayed slightly before passing into the ventricles; 4. the atrioventricular (AV) bundle, which conducts the impulse to the ventricles; and 5. the left bundle branch and right bundle branch, which further divide into the Purkinje fibers and conduct impulses to all parts of the ventricles
where are electrical impulses initiated in the heart?
sinoatrial node
where are impulses conducted in the heart?
internodal pathways, from the SA node
what conducts impulses to all parts of the ventricles?
left bundle branch and right bundle branch
where are impulses delayed in the heart?
atrioventricular node, before passing into ventricles
what conducts the impulse into ventricles?
atrioventricular bundle
what divides into the purkinje fibers?
left bundle branch and right bundle branch
where is the SA located?
in the upper lateral wall of the right atrium
why does each electrical impulse that begins in the SA node normally spread immediately into the atria?
the fibers of the node are contiguous with the muscle fibers of the atrium
why do the atria have time to contract and empty blood into the ventricles before ventricular contraction begins?
because the conductive system is organized so that the impulse does not travel into the ventricles too rapidly
where is AV node located?
in the posterior septal (dividing wall between the right and left sides) wall of the right atrium
do the left and right bundle branches penetrate the AV barrier?
only in their initial portion
is the function of bundle branches similar or different to AV nodal fibers?
opposite; they are large and transmit impulses at much higher velocity than AV nodal fibers
what kind of fibers more completely penetrate ventricles?
purkinje fibers
why do impulses travel so quickly throughout the ventricular system, allowing both ventricles to contract?
the penetration of purkinje fibers
what is the discharge rate of the SA node?
60-80 times per minute
what is the discharge rate of AV node?
40-60 times per minute
what is the discharge rate of ventricular fibers?
15-40 times per minute
AV node, ventricular fibers, SA node: least to most discharges?
ventricular fibers, AV node, SA node
what normally controls heart rhythmicity and why?
SA node, due to discharge rate
what happens each time the SA node discharges?
the impulse is conducted into the AV node and the ventricular fibers, discharging their excitable membranes, and self-excitatory tissues are discharged before self-excitation can actually occur
central is to peripheral as?
arterial is to venous Arteries
what are the functions of the capillaries?
to facilitate exchange of oxygen, fluid, nutrients, electrolytes, hormones, and other substances between the blood and the interstitial fluid in the various tissues of the body
are capillary walls permeable to nutrients, electrolytes, and hormones?
yes, but not all, substances
what is the function of venules?
to collect blood from the capillaries and gradually converge into the progressively larger veins, which transport blood back to the heart
why are the venous walls thin and muscular?
because the pressure in the venous system is very low
what does the low pressure / thin walls of venules allow?
to constrict or dilate to a great degree and thereby act as a reservoir for blood, either in small or in large amounts
what is the function of one-way valves?
to help maintain venous return by preventing retrograde blood flow.
what is the function of the cardiovascular system?
transports nutrients and removes waste products while helping to maintain the environment for all the body’s functions
what is the function of blood?
the blood transports oxygen from the lungs to the tissues for use in cellular metabolism; and it transports carbon dioxide, the most abundant by-product of metabolism, from the tissues to the lungs, where it is removed from the body
what is the most abundant by-product of metabolism?
carbon dioxide
how does blood transport of oxygen?
by hemoglobin, the iron-protein molecule carried by the red blood cells
how does hemoglobin affect the rates of chemical reactions in cells?
by acting as an acid-base buffer and a regulator of hydrogen ion concentration
how do red blood cells facilitate carbon dioxide removal?
by containing a large quantity of carbonic anhydrase which catalyzes the reaction between carbon dioxide and water
how is air distributed to the lungs?
by way of the trachea, bronchi, and bronchioles
what is another name for the trachea?
the first-generation respiratory passage
what is considered a second-generation passage for air?
the right and left main bronchi
what are third-generation respiratory passageways?
bronchioles
how many generations of respiratory passageways are there?
approximately 23 generations before the air finally reaches the alveoli, where gases are exchanged in respiration
what is the primary function of the respiratory system?
the basic exchange of oxygen and carbon dioxide.
how does the skeletal muscle pump assist contracting muscles providing blood to the circulatory system?
by working with the venous system, which contains the one-way valves for blood return to the heart; the contracting muscle compresses the veins, but since the blood can flow only in the direction of the valves, it is returned to the heart.
how might athletes use knowledge of the skeletal muscle pump?
the one-way flow of blood is one of the reasons that individuals are told to keep moving around after exercise to avoid blood pooling in the lower extremities; on the other hand, it is important to periodically squeeze muscles during prolonged sitting to facilitate blood return to the heart
what is the partial pressure of oxygen in the alveoli at rest?
about 60 mmHg greater than that in the pulmonary capillaries
what does the pressure disparity between pulmonary capillaries and alveoli entail?
oxygen diffuses into the pulmonary capillary blood, and carbon dioxide diffuses in the opposite direction
how fast does O2/CO2 diffuse through capillaries?
nearly instantly
the medulla influences what?
the inherent rhythmicity and conduction properties of myocardium
what does the medulla transmit signals through?
parasympathetic and sympathetic nervous system
what kind of nervous supply does the atria have?
parasympathetic and sympathetic neurons
what kind of nervous supply do the ventricles have?
sympathetic fibers almost exclusively
stimulation of the sympathetic nerves does what?
accelerates depolarization of the SA node (the chronotropic effect), which causes the heart to beat faster
what kind of stimulation will make the heart beat faster?
stimulating the sympathetic nerves
what slows the rate of SA node discharge, which slows the heart rate?
stimulation of the parasympathetic nervous system
where are ECGs recorded?
the surface of the body
what is an ECG composed of?
a P-wave, a QRS complex, and a T-wave
what are P wave and QRS complex recordings of?
electrical stimulus that leads to mechanical contraction
what is depolarization?
reversal of the membrane electrical potential, whereby the normally negative potential inside the membrane becomes slightly positive and the outside becomes slightly negative
how is the atria depolarized to result in atrial contraction?
when changes in the electrical potential of cardiac muscle cells generate a P-wave
how is the QRS complex generated?
by the electrical potential that depolarizes the ventricles and results in ventricular contraction
when electrical potential is generated as the ventricles recover from the state of depolarization, what is this called?
repolarization
how is the T-wave generated?
by electrical potential generated as the ventricles recover from the state of depolarization
where does repolarization occur?
in ventricular muscle shortly after depolarization
summarize the P wave, QRS, and T wave?
The P-wave is generated by the changes in the electrical potential of cardiac muscle cells that depolarize the atria and result in atrial contraction. The QRS complex is generated by the electrical potential that depolarizes the ventricles and results in ventricular contraction. In contrast, the T-wave is caused by the electrical potential generated as the ventricles recover from the state of depolarization; this process, called repolarization, occurs in ventricular muscle shortly after depolarization. Although atrial repolarization occurs as well, its wave formation usually occurs during the time of ventricular depolarization and is thus masked by the QRS complex.
does atrial repolarization occur after the atria is depolarized?
yes, but its wave formation usually occurs during the time of ventricular depolarization and is thus masked by the QRS complex
why do the arteries have strong muscular walls?
because blood pumped from the heart is under relatively high pressure
what is the function of arteries?
rapidly transport heart blood
what is the control vessel through which blood enters the capillaries?
arterioles (small branches of arteries)
how can arterioles alter blood flow to the capillaries in response to tissue needs?
by dilating to many times their size or closing completely, done by strong muscular walls
what mechanism does the lung use to control air?
recoil and expansion
what are the two methods of lung action?
- downward and upward movement of the diaphragm to lengthen and shorten the chest cavity 2. elevation and depression of the ribs to increase and decrease the back-to-front diameter of the chest cavity
what is the diaphragm?
a sheet of internal skeletal muscle in humans and other mammals that extends across the bottom of the thoracic cavity. the diaphragm separates the thoracic cavity, containing the heart and lungs, from the abdominal cavity and performs an important function in respiration: as the diaphragm contracts, the volume of the thoracic cavity increases, creating a negative pressure there, which draws air into the lungs.
how is normal quiet breathing accomplished?
almost entirely through diaphragm movement
how is air drawn into the lungs during inspiration?
contraction of the diaphragm creates a negative pressure (vacuum) in the chest cavity, and air is drawn into the lungs
what is the action of the diaphragm during expiration?
the diaphragm simply relaxes; the elastic recoil of the lungs, chest wall, and abdominal structures compresses the lungs, and air is expelled
can heavy breathing occur through elastic recoil of the lungs?
no, elastic forces alone are not powerful enough to provide the necessary respiratory response; extra required force is achieved mainly by contraction of the abdominal muscles, which push the abdomen upward against the bottom of the diaphragm
what is the non-diaphragmatic method of lung expansion?
raising the rib cage
how can the rib cage be projected forward so that the sternum can move forward and away from the spine?
by elevating the rib cage
how is the rib cage able to be elevated and projected forward?
because the chest cavity is small and the ribs are slanted downward while in the resting position
what are the muscles of inspiration and what do they do?
external intercostals, the sternocleidomastoids, the anterior serrati, and the scaleni; these elevate the rib cage
what are the muscles of expiration and what do they do?
the abdominal muscles (rectus abdominis, external and internal obliques, and transversus abdominis) and the internal intercostals; these elevate the rib cage
what is pleural pressure?
pressure in the narrow space between the lung pleura and the chest wall pleura (membranes enveloping the lungs and lining the chest walls)
what is normal pleural pressure?
slightly negative
what is alveolar pressure?
the pressure inside the alveoli when the glottis is open and no air is flowing into or out of the lungs (when this occurs the pressure in all parts of the respiratory tree is the same all the way to the alveoli and is equal to the atmospheric pressure)
how can the alveoli cause inward flow of air during inspiration?
during inspiration, the pressure in the alveoli must fall to a value slightly below atmospheric pressure; during expiration, alveolar pressure must rise above atmospheric pressure.
how is inspiration enhanced by lung composition?
the expansion of the chest cage is able to pull on the surface of the lungs and creates a more negative pressure, due to the lung’s elastic structure (this process is reversed in expiration)
what causes inward flow of air during inspiration?
the pressure in the alveoli must fall to a value slightly below atmospheric pressure
when the glottis is open and no air is flowing into or out of the lungs, what is this kind of pressure called?
alveolar pressure
when the glottis is open and no air is flowing into or out of the lungs , what is the state of the pressure?
the pressure in all parts of the respiratory tree is the same all the way to the alveoli and is equal to the atmospheric pressure how must pressure change during expiration?alveolar pressure must rise above atmospheric pressure
how much energy expended by the body is required at rest for normal respiration?
3% to 5% of the total energy
how much energy for respiration and pulmonary ventilation is required during heavy exercise?
as much as 8% to 15% of total body energy expenditure, especially if the person has any degree of increased airway resistance, as occurs with exercise-induced asthma
what occurs during ventilation?
oxygen diffuses from the alveoli into the pulmonary blood, and carbon dioxide diffuses from the blood into the alveoli
what is the process of diffusion?
a simple random motion of molecules moving in opposite directions through the alveolar capillary membrane
how is the energy for diffusion provided?
by the kinetic motion of the molecules themselves
where does net diffusion of the gas occur?
from the region of high concentration to the region of low concentration
what do the rates of diffusion of oxygen and CO2 depend on?
their concentrations in the capillaries and alveoli and the partial pressure of each gas
