Chapter 1 - Structure and Function of Body Systems Flashcards
Musculoskeletal System
bones, joints, muscles tendons, configured to allow a great variety of movements
Muscles function by _____ against ______ that rotate about _____
muscles function by PULLING against BONES that rotate about JOINTS
Muscles can only pull, but b/c of boney levers, muscle pulling force can be manifested as either ____ or ____
PULL or PUSH
Axial Skeleton
skull (cranium)
vertebral column (C1-coccyx)
ribs
sternum
Appendicular Skeleton
Shoulder girdle (L&R scapula and clavicle)
Bones of arms, wrists, hands (humerus, radius ulna, carpals, metacarpals, phalanges)
Pelvic girdle (coxal and innominate bones)
Bones of legs, ankle, feet (femur, patella, tibia, fibula, tarsals, metatarsals, and phalanges)
Joints (3)
junctions of bones; fibrous, cartilaginous, synovial
Fibrous Joints
allow virtually no movements (skull sutures)
Cartilaginous Joints
limited movements (intervertebral disks)
Synovial Joints
considerable movements due to low friction and large ROM (elbow, knee)
Hyaline Cartilage
cover articulating bone ends
Synovial Fluid
enclose joints in a capsule fluid
Joints # of direction (rotation)
uniaxial, biaxial, multiaxial
Uniaxal
Elbow/Knee
operate as hinges and rotate on 1 axis
Biaxal
Ankle/Wrist
movement about 2 perpendicular axes
Multiaxial
Shoulders/Hip ball and sockets
movement about all 3 perpendicular axes
Vertebral Column
vertebral bones separated by disks. 7 cervical (neck) 12 thoracic (mid/upper back) 5 lumbar ( low back) 5 sacral (rear pelvis) 3-5 coccygeal (vestigial internal tail)
List the number at types of vertebrae
7 cervical (neck) 12 thoracic (mid/upper back) 5 lumbar ( low back) 5 sacral (rear pelvis) 3-5 coccygeal (vestigial internal tail extending down from pelvis)
Factors affecting skeletal growth in adults
Heavy loads: increase bone density and mineral content
Explosive movements w/ impact: similar to heavy loads
High strength and high power movements (gymnastics)
How often the axial skeleton is loaded.
Musculoskeletal Macrostructure and Microstructure
each skeletal muscle contains: muscle tissue connective tissue nerves blood vessels
Epimysium
Fibrous connective tissue that covers skeletal muscle.
Adjoins w/ tendons.
Tendons attached to bone periosteum
Bone Periosteum
specialized connective tissue covering all BONES.
Any muscle contraction pulls tendon, which pulls the bone
Limb muscle attachemnts
proximal (closer to trunk)
distal (further from trunk)
Truck muscle attachments
superior (closer to head)
inferior (closer to feet)
Muscle Cells
i.e. muscle fibers
Long, cylindrical cells 50-100 µm (micrometer).
Have many nuclei situated on the periphery of the cell.
Striated appearance
Fasciculi
bundles of muscle fibers under epimysium.
Consist of up to 150 fibers, w/ bundles covered by perimysium
Perimyium
connective tissue surrounding fasciculi
Endomysium
connective tissue surrounding each muscle fiber
Sarcolemma
fibrous membrane.
encricle endomysium
Connective tissues
epimysium
perimysium
endomysium
Connective tissues are all…
contiguous w/ the tendon, so tension developed in muscle cell is transmitted to tendon and bone it’s attached to
Neuromuscular Junctions
i.e. End Plate
junction between motor neuron (nerve cell) and muscle fibers it innervates.
Each muscle cell has _____ NMJ
Each muscle cell has 1 NMJ, although a motor neuron innervates hundreds or even thousands of muscle fibers
Moto Unit
motor neuron and the muscle fibers it innervates
All muscle fibers of a motor unit contract when stimulated by a ______ _______
motor neuron
Interior Structure of Muscle Fiber (3)
Sarcoplasm
Myofibrils
Myofilament
Sarcoplasm
The cytoplasm of a muscle fiber.
Contains contractile components consisting of:
Protein filaments
Other proteins
Stored glycogen fat
Enzymes
Specialized organelles (mitochondria and sarcoplasmic reticulum)
Myofibrils
hundreds dominate the sarcoplasm.
contain apparatus that contracts muscle cells and contain 2 primary types of myofilament
Myofilament
myosin and actin filaments
thick and thin
Myosin
Thick filament (~16nm diameter, 1/10,000 diameter of hair) contain up to 200 myosin molecules. Consists of globular head, hinge point, and fibrous tail
Myosin Globular Head
Protrude away from myosin filament regularly.
2 myosin form a cross-bridge, which interact w/ actin
Actin
Thin filaments (~6nm diameter) Consists of 2 strands arranged in double helix
Myosin and Actin arrangement
arranged longitudinally in smallest contractile unit of skeletal muscle, the sacromere
Sacromere
avg. ~2.5 µm in length in relaxed fibers
~4,500 per cm of muscle length
Structure and Orientation of Myosin and Actin in Sacromere
Adjacent myosin anchor to each other @ M-bridge in center of sacromere (center of H-zone).
Actin is aligned at both ends of sacromere (anchored @ Z-line)
# of Actin surrounding each Myosin # of Myosin surround each Actin
6 actin surround each Myosin
3 Myosin surround each Actin
Arrangement of myosin and actin filaments + Z-lines of sacromeres =
alternating dark and light pattern of skeletal muscle
A-band
(DARK)
alignment of myosin filaments
I-band
(LIGHT)
2 adjacent sacromeres that contain only actin filaments.
Decreases as Z-lines are pulled toward center of sacromere.
Z-line
(THIN, DARK)
middle of I-band, running longitudinally through I-band
H-zone
center of sacromere where only myosin filaments are present.
During muscle contraction, H-zone decreases as actin slides over myosin toward center of sacromere.
Sarcoplasmic Reticulum (SR)
parallel to each myofibrils.
SR is a intricate system of tubules which ends as vesicles around the Z-lines. Calcium ions are stored in these vesicles.
Regulation of Ca+ ions controls muscle contraction
Transverse tubules (T-tubules)
run perpendicular to SR and end around Z-line between 2 vesicles.
B/c T-tubules run between outlying myofibrils and are contiguous w/ sarcolemma at cell surface, action potential occurs
Action Potential (AP)
Electrical nerve impulse.
Discharge of AP from motor nerve signals release of CA+ from SR into myofibril, causing tension development in muscle (i.e. muscle contraction)
Sliding Filament Theory of Muscle Contraction
Actin at each end of sacromere slide inward on myosin filaments, pulling Z-lines toward center of sacromere, thus shortening the muscle.
Actin slides over myosin, causing H-zone and I-band to shrink.
Myosin cross-bridges pulling actin is responsible for moving actin.
Resting Muscle
little Ca+ is present in myofibril, meaning very few myosin are attached to actin (weak bond)
Excitation-Contraction Coupling Phase
Myosin must attach to actin before myosin cross-bridges can flex
SR stimulation > Ca+ release > Ca binds w/ troponin > shift in tropomyosin > myosin cross-bridge attaches more rapidly to actin, producing more force as actin is pulled toward center of sacromere.
Troponin
protein situated at regular intervals along w/ actin filament and has high affinity for Ca+ ions
Tropomyosin
runs length of actin filament in groove of double helix
Amount of force produced by muscle is directly related to…
the # of myosin cross-bridges bound to actin filaments cross-sectionally at that instant in time.
Power Stroke
energy for pulling action.
Comes from hydrolysis (breakdown) of ATP to ADP + P
Enzyme catalyst during hydrolysis of ATP
myosin adensosine triphosphatase (ATPase)
Contraction Phase
Power Stroke
Another ATP must replace ADP on myosin cross-bridge globular head in order for head to detach from active actin site and return to its original position.
Contraction process continues (if Ca available) or relaxation occurs (if Ca isn’t available).
Recharge Phase (5)
muscle shortening occurs during the repeated sequence of:
Ca binds to troponin.
Myosin cross-bridge couples w/ actin.
Power stroke.
Dissociation (release) or actin and myosin.
Myosin head resets position.
Recharge phase only occurs when… (3)
Ca is available in myofibril.
ATP is available to assist w/ uncoupling myosin from actin.
Sufficient active myosin ATPase is available for catalyzing the breakdown of ATP.
Steps of Muscle Contraction Summarized (5)
1) ATP splitting by myosin ATPase causes myosin head to be energized, allowing the head to move into binding position w/ actin.
2) ATP splitting causes release of phosphate (P), causing myosin head to change shape and shift.
3) This shift pulls actin filament toward center of sacromere (aka Power Stroke), causing ADP release.
4) Once power stroke occurs, myosin head detaches from actin, but only after another ATP binds to myosin head; this binding facilitates detachment.
5) The detached myosin head is ready to bind to another actin (Step 1). Cycle continues as long as ATP and ATPase are present and Ca is bound to troponin.
Motor neuron fires an impulse (AP) causing…
Motor neuron fires an impulse (AP) causing all associated fibers to be activated and develop force.
Muscle controls depends on the…
Muscle control depends on the # of muscle fibers within each motor unit.
Muscles that require great precision may have…
Muscles that require great precision may have motor units w/ as few as 1 muscle fiber per motor neuron.
ex. eye muscles
Muscles that require less precision may have…
Muscles that require less precision may have several hundred fibers per motor neuron
ex. quads
AP flow along motor neuron can’t directly excite _____ _____
muscle fibers.
Instead, the motor neuron excites the muscle fibers it innervates by chemical transmission.
AP arrives at nerve terminal, causing release of acetylcholine
Acetylcholine
neurotransmitter;
diffuses across NMJ causing excitation of sarcolemma resulting in fiber contraction
All-or-none principle
All (never some) muscle fibers contract at same time.
Stronger AP cannot produce stronger contractions.
Twitch (contraction)
the brief contraction of muscle fibers within motor unit as each AP travels downs motor neuron.
Sarcolemma is activated which releases CA within fiber
Single Twitch
Ca released before max force of fiber; muscle relaxes
Second Twitch
if elicited before fibers relax, force from both twitches combine. This results in greater force produced by a single twitch.
Time & Twitch (Tetanus)
Decreasing time between twitches results in greater cross-bridge and force production.
Stimuli may be delivered so fast that twitches begin to merge and eventually fuse (i.e. twitch summation).
Tetanus
max amount of force the motor unit can develop
Muscle Fiber Classifications
Fast twitch
Slow Twitch
Fast Twitch Muscle Fibers
develops force quickly
relaxes rapidly
short twitch time
Slow Twitch Muscle Fibers
develops force slowly
relaxes slowly
long twitch time
Type I Fibers
slow twitch
efficient and fatigue resistant
high capacity for aerobic energy supply
limited/low force development (low myosin ATPase activity and low anaerobic power)
Type II (IIa or IIx)
inefficient and fatigable low aerobic power rapid force development high myosin ATPase activity high anaerobic power
Type IIa compared to Type IIx
greater aerobic metabolism
more capillaries surrounding them
greater resistance to fatgue
Muscle force can be graded in 2 ways:
1) variation of the frequency at which motor units are activated
2) motor unit recruitment
Variation of the frequency at which motor units are activated
if a motor unit is activated once, the twitch that arises doesn’t produce a great deal of force (single twitch)
if a motor unit is activated more frequently, force generated begins to overlap (summate), resulting in greater force (tetanus)
Motor Unit Recruitment
increasing force by varying the # of motor units activated. large muscles (thigh), motor units are activated at near-tetanic frequency. increases in force output is achieved through recruitment of additional motor units
Complete activation of available motor neuron pool is probably not possible in untrained individuals, although…
although large fast twitch units may be recruited if effort is substantial, it’s probably not possible to activate them at a high frequency for max force.
Proprioceptors
Specialized sensory receptors located within joints, muscles, and tendons that provide the CNS w/ information needed to maintain muscle tone and perform complex coordinated movements.
Relay info about muscle dynamics to conscious and subconscious parts of the CNS.
Muscle Spindles
proprioceptors that consist of several modified muscle fibers (extrafusal and intrafusal) enclosed in a shealth of connective tissues
Extrafusal Muscle Fibers
normal muscle contracting fibers
Intrafusal Muscle Fibers
muscle spindles; run parallel to extrafusal fibers.
When muscle lengthens, ______ stretch. The process that follows
spindles;
this stretch activates the sensory neuron of the spindle > sends impulse to spinal cord > impulse synapses (connects) w/ motor unit > activation of motor neurons innervating same muscle.
Spindles indicate degree to which _____ must be activated in order to overcome a given ________
muscle, resistance.
as load increases, muscle is stretched to greater extent, causing muscle spindles to be emerged and result in greater muscle activation.
Muscle performing _______ movements have more muscle spindles per per uint of mass
precise.
ex. knee jerk reflex; tap tendon of knee extensor > knee extensors stretch > extrafusal fibers activate > knee jerk occurs as the extensor muscles shorten > intrafusal fibers discharge to cease the stretch.
Golgi Tendon Organs (GTO)
Proprioceptors located in tendons near myotendinous junction and are in series (attached from end to end) wi/ extrafusal muscle fibers.
Activated when tendon attached to muscle is stretched; as tension increases, discharge of GTO increases.
Sensory neuron of GTO
Synapses w/ inhibitory interneuron in spinal cord, which then synapses w/ and inhibits a motor neuron that serves the same muscle.
This results in less tension within muscle and tendon.
Muscle spindles facilitate activation of muscle, whereas GTO neural imput…
inhibits muscle activation
GTO inhibitory process provides a mechanism that protects against…
development of excessive tension.
Low force/load = low GTO activity.
High force/load = reflexive inhibition by GTO causing muscle relaxation.
How can athletes improve force production? (3)
1) training phases that incorporate heavier loads in order to optimize neural recruitment
2) increase cross-sectional area of muscles involved in desired activity.
3) perform explosive multi-muscle and multi-joint exercises to optimize fast-twitch muscle recruitment.
Primary roles of the Cardiovascular System (3)
transport nutrients
remove waste and byproducts
assist w/ maintaining environment for body’s functions
Heart L and R pumps
L: pumps blood through rest of body
R: pumps blood through lungs
Each pump has 2 chambers
Chambers of heart pumps
Atrium
Ventricle
L and R Atria
deliver blood into L and R ventricle
L and R Ventricles
supply main force for moving blood through peripheral (L ventricle) and pulmonary (R ventricle) circulations, respectively.
Atrioventricular (AV) Valves (Heart Valves)
Tricuspid valve Mitral valve (bicuspid valve) AV valves prevent blood flow from ventricles back into the atria during ventricular contraction (systole)
Semilunar Valves (Heart Valves)
Aortic valve
Pulmonary Valve
prevents backflow from aorta and pulmonary arteries into ventricles during ventricular relaxation (diastole)
Opening and closing of valves
each valve opens and closes passively.
Closes when backward pressure gradient pushes blood back against it.
Opens when forward pressure gradient forces blood in forward direction.
Conduction System and what it consists of
specialized electrical conduction system that controls mechanical contraction of heart.
Composed of:
Sinoatrial (SA) node
Internodal pathways that conduct the impulse from the SA node to the AV node.
Atrioventricular (AV) node
Atrioventricular (AV) bundle
L and R bundle branch
Sinoatrial (SA) node
intrinsic pacemaker; rhythmic electrical impulses are normally initiated and spread immediately into atria.
Small area of specialized muscle tissue in upper lateral wall of R. atrium.
Its fibers are continguous w/ muscle fibers of atrium.
Atrioventricular (AV) node
impulse is delayed slightly before passing into ventricle
Prevents impulse from traveling into ventricles too rapidly, allowing time for atria to contract and empty blood into ventricles before ventricular contraction begins.
Located in posterior septal wall of R. atrium
Atrioventricular (AV) bundle
conducts impulse to the ventricles
L and R bundle branch
further divide into the Purkinje fibers and conduct impulses to all parts of the ventricles.
Lead from AV bundle into ventricles, except the initial portion when they penetrate AV barrier.
Purkinje fibers
a
Electrocardiogram
Graphic representation of electrical activity of the heart.
Recorded at surface of body.
P-wave, QRS complex, T-wave.
P-wave and QRS complex
recordings of electrical depolarization.
P-wave = Atria ; QRS = Ventricles
T-wave
Repolarization of ventricles.
Blood Vessels
Operate in closed-circuit system.
Arterial carries blood away from heart.
Venous system returns blood.
Arteries
rapidly transport blood pumped from heart.
Capillaries
change O2, fluid, electrolytes, hormones, and other substances between blood and interstitial fluid in the various tissues of the body.
Veins
collect blood from the capillaries and gradually converge into progressively larger veins which transport blood back to heart.
Blood
hemoglobin transports O2 and serves as an acid-base buffer.
RBC facilitate CO2 removal
General role of Cardiovascular System
transports nutrients and removes waste products while helping to maintain the environment for all the body’s functions. The blood transports O@ from the lungs to the tissues for use in cellular metabolism, and it transports CO2 from the tissues to lungs, where it’s removed form body.
Skeletal Muscle Pump
Contracting muscles compresses veins, pushing blood one-way to return to heart.
Ex. continued movement after exercise to avoid blood pooling.
Respiratory System
Air distributed two lungs by way of trachea, bronchi, and bronchioles, before the air finale reaches alveoli (gas is exchanged).
Exchange of Air
amount and movement of air and expired gases in and out of the lungs are controlled by expansion and recoil of the lungs
Expiration
diaphragm RELAXES.
Elastic recoil of lungs, chest wall, and abdominal structures compress lungs.
Inspiration
diaphragm CONTRACTS creating negative pressure.
Exchange of Respiratory Gases
Primary function is basic exchange of O2 and CO2
Ventilation
O2 diffuses from alveoli into pulmonary blood, and CO@ diffuses from blood into alveoli.
