Chapter 1: Structure and Function of Body Systems Flashcards
Musculoskeletal System
- Bones, joints, muscle, and tendons
- Allows a great variety of movements
Role of bones and muscle in movement
- Muscles only pull
- Bones act as levers and transmit force on the environment
How many muscles are in the body?
~206 muscles in the body
Skeletal Divisions
- Axial
- Appendicular
Axial Skeleton
- Skull (cranium)
- Vertebral column
- Ribs
- Sternum
Appendicular Skeleton
- Shoulder (pectoral) girdle (left and right scapula and clavicle)
- Bones of the arms, wrists, and hands (Humerus, radius, ulna, carpals, metacarpals, phalanges)
- Pelvic girdle
- Bones of the legs, ankles, and feet (Femur, patella, tibia, fibula, tarsals, metatarsals, phalanges)
Joints
Junctions of bones
Fibrous joints
- Allows almost no movement
- Ex: sutures of the skull
Cartilaginous joints
- Allow limited movement
- Ex: intervertebral discs
Synovial joints
- Allow considerable movement
- Most important features are low friction and large ROM
- Ex: Elbow and knee
Hyaline cartilage
Covers the articulating end of bones
Synovial fluid
Fluid filling the joint capsule
Joint rotation about an axis
Virtually all movement occurs about an axis
Uniaxial joint
- Rotates about only 1 axis
- Ex: elbow
Biaxial joint:
- Rotates about 2 axes
- Ex: Ankle and wrist
Multiaxial joint:
- Allows movement in all 3 perpendicular planes of motion
- Ex: should and hip (ball & socket)
Vertebral Column
- 7 cervical, 12 thoracic, 5 lumbar, 5 sacral (fused), 3-5 coccygeal vertebrae
- Separated by flexible discs allowing movement to occur
Skeletal Muscle
An organ containing muscle and connective tissue, nerves, and blood vessels
Tendon
- Attached to bone periosteum
- Connects muscle to bone
- Contraction of muscle pulls on the tendon and, in turn, the bone
- Connects to all connective tissue
Bone Periosteum
Specialized connective tissue covering all bones
Proximal
Closer to the trunk
Distal
Farther from the trunk
Superior
Closer to the head
Inferior
Away from the head
Sarcoplasm
Contains nuclei, mitochondria, and specialized organelles
Myofibril
Any of the elongated contractile threads known as myofilaments
Myofilament
Actin and myosin
Sarcolemma
Surrounds each muscle fiber and encloses the fiber’s cellular contents
Muscle fiber
- Bundle of myofibrils
- Muscle cell
Endomysium
Wraps each muscle fiber/cell and separates it from neighboring fibers
Fasciculus
A bundle of muscle fibers
Perimysium
Surrounds a bundle of fibers
Epimysium
Surrounds the entire muscle then blends into the intramuscular tissue sheaths to form tendons
Skeletal Muscle Composition (deep to superficial)
- Myofilaments combine to form…
- Myofibrils combine to form…
- Muscle fibers/cells combine to form…
- Fasciculi combine to form…
- Muscles
Skeletal Muscle Connective Tissue Organization
- Myofibrils are surrounded by the sarcoplasm
- Muscle fibers are bound by the sarcolemma
- Muscle fibers are separated by endomysium
- Fasciculi are bound by perimysium
- Muscles are bound by epimysium
Types of myofibrils
- Actin
- Myosin
Actin
2 strands arranged in a double helix
Myosin
- Globular head
- Hinge point
- Fibrous tail
Cross-bridge
A pair of myosin filaments which interact with actin
Sarcomere
Smallest contractile unit of the skeletal muscle
I-band
- Isotropic
- Represents lighter area
- Only actin is visible
- Gets smaller with contraction
A-band
- Anisotropic
- Represents darker area
- Actin and myosin overlap
- Remains the same size during contraction
- H-zone
- M-band
H-zone
- Center of A-band
- Area of A-band that only has myosin
M-band
- Bisects H-zone
- Consists of protein structures that support arrangement of myosin filaments
Z-line
- Bisects I-band
- Adheres to sarcolemma to provide structural stability
Thin Filament
- Actin
- Troponin
- Tropomyosin
Thick Filament
Myosin
Sliding-Filament Theory of Muscular Contraction
Actin filaments at each end of the sarcomere slide inward on myosin filaments, pulling the Z-lines toward the center of the sarcomere
Phases of the Sliding-Filament Theory of Muscular Contraction
- Resting phase
- Excitation-contraction coupling phase
- Contraction phase
- Recharge phase
- Relaxation phase
Resting Phase
- Little calcium is present in the myofibril
- Most calcium is stored in sarcoplasmic reticulum
- Tension occurs when the actin binding site is exposed
Excitation-Contraction Coupling Phase
- Before cross-bridge cycle can occur, myosin needs to attach to the actin filament
Troponin
Binding site for calcium
Tropomyosin
Protein running the length of actin, which covers the binding site for the myosin heads
Contraction Phase
- Energy for pulling comes from the breakdown of ATP –> ADP + P
- Reaction catalyzed by myosin ATPase
- As long as calcium is available to bind to tropinin, ATP will replace ADP to continue the cross-bridge cycle for contraction
- Relaxation occurs when calcium is no longer available
Recharge Phase
Muscle shortening only occurs when calcium is available in the myofibril
Relaxation Phase
- Relaxation occurs when motor nerve stimulation stops
- Calcium is pumped back into the sarcoplasmic reticulum
- Actin and myosin return to their unbound state, inducing relaxation
Steps of Muscle Contraction
1) Binding of myosin to actin (ADP + P)
- Inorganic phosphate is released
2) Power stroke (ADP)
- Actin gets pulled toward the middle of the sarcomere
- ADP is released
3) Rigor (myosin is in low-energy form)
- New ATP binds to myosin head
4) Unbinding of myosin and actin
- ATP is hydrolyzed
5) Cocking of the myosin head (myosin is in high-energy form) (ADP + P)
6) Repeat
Motor Unit
A nerve and all of the muscle fibers it innervates
What kind of actions does a small motor unit perform?
Precise movements
What kind of actions does a large motor unit perform?
Gross, powerful movements
Action Potential
- Electric current flowing along a motor neuron
- Does NOT directly stimulate the muscle
- Muscle excitation occurs via chemical transmission
Acetylcholine
- Neurotransmitter released when action potential reaches neuromuscular junction
- AP excites the sarcolemma –> calcium is released
- When enough ACh is released, an AP is released along the sarcolemma and causes contraction
All-or-None Principle
When an action potential causes a twitch, all muscle fibers innervated by the nerve contract maximally
Twitch
The brief contraction that occurs as a result of an action potential
Tetanus
Phenomenon that occurs when twitches are close enough together that they merge and completely fuse
Slow-Twitch Muscle Fiber
Type I
- Generally efficient
- Fatigue-resistant
- High capacity for aerobic supply
- Limited potential for rapid force development
- Low myosin ATPase activity
- Low anaerobic power
Fast-Twitch Muscle Fiber
- Generally inefficient
- Susceptible to fatigue
- Low capacity for aerobic supply
- High potential for rapid force development
- High myosin ATPase activity
- High anaerobic power
Type IIa Fast-Twitch Muscle Fiber
- Greater capacity for aerobic metabolism
- More capillaries surrounding them –> greater resistance to fatigue
Type IIx Fast-Twitch Muscle Fiber
- Least capable of aerobic metabolism
- Few capillaries surrounding them –> highly susceptible to fatigue
What kind of muscle fibers perform postural function?
Generally type I
What kind of muscle fibers perform locomotor functions?
Mix of type I and II
Proprioceptors
- Specialized sensory receptors located within joints, muscles, and tendons
- Sensitive to pressure and tension
- Relay info to conscious and subconscious areas of the brain
Kinesthetic Sense
Conscious appreciation of bodily position
How is proprioceptive info processed?
Most proprioceptive info is processed subconsciously so we don’t have to dedicate conscious thought to activity such as moving or maintaining posture
Types of proprioceptors
- Muscle spindles
- Golgi tendon organs
Muscle Spindles
- Modified muscle fibers within the body of the muscle
- Provides info regarding muscle length and the rate of change in muscle length
Intrafusal Fibers
- Modified muscle fibers enclosed in a sheath of connective tissue
- Runs parallel to normal fibers
Extrafusal Fibers
Normal muscle fibers
How do muscle spindles work?
When the muscle lengthens, spindles are also stretched, causing the activation of motor neurons in the same muscle
Golgi Tendon Organ
- Located in tendons near the myotendinous junction
- Attached in a series with extrafusal fibers
- When GTOs are activated, the same muscle is inhibited
Heart
- 2 pumps, each with 2 chambers
- Atrium
- Ventricle
Atrium
Delivers blood to the ventricle
Ventricle
Provide the main force for moving blood through the pulmonary and peripheral circulations (right and left)
Valves of the heart
- Atrioventricular
- Semilunar
Atrioventricular Valves
- Tricuspid
- Mitral (bicuspid)
- Prevents bloodflow back into the atria during ventricular contraction (systole)
Semilunar Valves
- Aortic
- Pulmonary
- Prevents backflow from the aorta and pulmonary arteries into the ventricles during ventricular relaxation (diastole)
Parts of the conduction system
- Sinoatrial (SA) node
- Internodal pathways
- Atrioventricular (AV) node
- Atrioventricular (AV) bundle
- Left/right bundles
Sinoatrial (SA) Node
- Intrinsic pacemaker
- Rhythmic electrical impulses are normally initiated here
Internodal Pathways
Conducts the impulse from the SA node to the atrioventricular node
Atrioventricular (AV) Node
- Impulse is delayed slightly before passing into the ventricles
- Allows the atria to contract before the ventricles
Atrioventricular (AV) Bundle
Conducts the impulse to the ventricles
Left/Right Bundles
- Divide further into the Purkinje fibers
- Conducts impulses into all parts of the ventricles
Myocardium
Heart muscle
Cardiovascular center of the medulla
- Influences the rhythmicity and conduction properties of the myocardium
- Connected to both the sympathetic and parasympathetic nervous system
Bradycardia
Less than 60 bpm
Tachycardia
More than 100 bpm
Electrocardiogram
Graph depicting the electrical activity of the heart
Parts of an ECG
- P-wave
- QRS complex
- T-wave
What is occurring during the P-wave/QRS complex
Depolarization
What is occurring during the T-wave
Repolarization
Components of the circulatory systems
- Arterial system
- Venous system
Arterial System
Carries blood away from the heart
Venous System
Carries blood to the heart
Types of blood vessels
- Arteries
- Arterioles
- Capillaries
- Venules
- Veins
Arteries
- Transports blood away from the heart
- Have strong muscular walls
Arterioles
Small branches of arteries that act as control vessels through which the blood enters the capillaries
Capillaries
Facilitate the exchange of oxygen, fluid, nutrients, electrolytes, hormones, and other substances
Venules
Collects blood from the capillaries, and gradually converge into veins
Veins
Transports blood back to the heart
Main functions of blood
- Transport oxygen from lungs to the tissues
- Remove carbon dioxide from the tissues to the lungs
Hemoglobin
- An iron-protein molecule carried by red blood cells
- Accomplishes oxygen transportation
- Also acts as an acid-base buffer
Red blood cells
Major component of blood
Primary function of the respiratory system
Exchange of oxygen and carbon dioxide
Function of nasal cavities
Warming, humidifying, and purifying the air
Path of air through the body
Trachea –> bronchi –> bronchioles –> alveoli
Trachea
First generation respiratory passage
Bronchi
- Right and left
- Second generation respiratory passage
Bronchioles
- Additional generations of respiratory passages
- ~23 generations before reaching the alveoli
Alveoli
Where gases are exchanged
Methods by which gases are exchanged
- Diaphragmic breathing
- Chest breathing
Diaphragmic Breathing
- Normal, quiet breathing
- Contraction of the diaphragm creates a negative pressure in the chest cavity, drawing air into the lungs
- During expiration, the diaphragm relaxes
- Abdominal muscles need to contract during heavy breathing to force airflow
Chest Breathing
-
Pleural Pressure
The pressure in the narrow space between the lung pleura and the chest wall
Pleura
Membranes enveloping the lungs and lining the chest walls
Alveolar Pressure
The pressure inside the alveoli when the glottis is open and no air is flowing into or out of the lungs
Diffusion
Simple random motion of molecules moving from high to low concentration
