Chapter 1 - Structure and Function of Body Systems Flashcards
A-band
Region of a sarcomere where thick (myosin) and thin (actin) filaments overlap; maintains constant length during muscle contraction
Atrium
Heart chamber that receives blood and pumps it to the ventricles; right atrium handles deoxygenated blood, left atrium handles oxygenated blood
Acetylcholine
Neurotransmitter released at the neuromuscular junction to initiate muscle contraction
Action Potential
Electrical impulse that travels along the nerve and muscle membranes, triggering muscle contraction
All-or-none principle
Motor units contract maximally when stimulated, or not at all
Alveolar Pressure
Air pressure within the alveoli; decreases during inhalation, increases during exhalation
Alveoli
Tiny air sacs in the lungs where gas exchange occurs between air and blood
Aortic Valve
Valve between the left ventricle and the aorta; prevents backflow of blood into the heart
Appendicular skeleton
Includes bones of the limbs and girdles (shoulder and pelvis) that attach them to the axial skeleton
Arterial system
Network of arteries carrying oxygen-rich blood from the heart to body tissues
Artery
Blood vessel carrying oxygenated blood away from the heart, except for the pulmonary artery
Atrioventricular (AV) Bundle
Specialized muscle fibers that conduct electrical impulses from the AV node to the ventricles
Atrioventricular (AV) Node
Electrical relay station between the atria and ventricles; delays the impulse to ensure proper ventricular filling
Atrioventricular (AV) Valves
Valves that prevent backflow of blood into the atria during ventricular contraction; includes tricuspid and mitral valves
Axial skeleton
Central part of the skeleton, consisting of the skull, vertebral column, and rib cage
Biaxial joints
Joints that allow movement in two planes, such as the wrist (flexion/extension and radial/ulnar deviation).
Bone periosteum
Dense connective tissue covering the outer surface of bones, providing attachment for tendons and ligaments and housing bone-forming cells.
Bradycardia
A resting heart rate below 60 beats per minute; common in well-trained athletes.
Bronchi
The primary passageways for air entering the lungs; branch off the trachea into each lung.
Bronchiole
Smaller airways in the lungs that branch off the bronchi and lead to alveoli.
Capillary
The smallest blood vessels where gas, nutrient, and waste exchange occurs between blood and tissues.
Cartilaginous Joints
Joints connected by cartilage, allowing limited movement, such as intervertebral discs.
Crossbridge
The connection formed between actin and myosin filaments during muscle contraction, allowing for force generation.
Depolarization
The process by which a cell membrane’s electrical charge becomes less negative, initiating an action potential in muscle or nerve cells.
Diastole
The phase of the cardiac cycle when the heart relaxes and fills with blood.
Diffusion
The movement of molecules from an area of higher concentration to an area of lower concentration, such as oxygen moving from alveoli to blood.
Distal
Anatomical term indicating a position farther away from the trunk or point of origin (e.g., fingers are distal to the shoulder).
Electrocadiogram (ECG)
A recording of the electrical activity of the heart used to assess heart function.
Endomysium
Connective tissue surrounding each individual muscle fiber, providing structural support.
Epimysium
Outer layer of connective tissue surrounding an entire muscle, protecting and maintaining its structure.
Extrafusal fibers
Skeletal muscle fibers responsible for generating force; innervated by alpha motor neurons.
Fasciculi
Bundles of muscle fibers surrounded by perimysium.
Fast-twitch muscle fiber
Muscle fibers that contract quickly, generate high force, and fatigue rapidly (Type IIa and Type IIx fibers).
Fibrous Joints
Joints connected by dense connective tissue, allowing little to no movement (e.g., sutures in the skull).
Golgi Tendon Organ (GTO)
Proprioceptor located in tendons that detects tension and inhibits muscle contraction to prevent injury.
Hemoglobin
Protein in red blood cells that binds oxygen and transports it throughout the body.
Hyaline Cartilage
Smooth, glass-like cartilage that covers the ends of bones in synovial joints to reduce friction.
H-zone
The central region of the A band in a sarcomere where only thick filaments (myosin) are present; shortens during contraction.
I-band
The region of a sarcomere containing only thin filaments (actin); shortens during muscle contraction.
Inferior
Anatomical term indicating a position lower or below another part of the body (e.g., the stomach is inferior to the lungs).
Intrafusal fibers
Specialized muscle fibers within muscle spindles that detect changes in muscle length and help regulate muscle tone.
Left bundle branch
Part of the heart’s conduction system that transmits electrical impulses from the AV node to the left ventricle.
Mitral valve
Valve between the left atrium and left ventricle; prevents backflow of blood into the atrium during ventricular contraction.
Motor Neuron
Nerve cell that transmits impulses from the central nervous system to a muscle to initiate contraction.
Motor unit
A motor neuron and all the muscle fibers it innervates; the basic functional unit of muscle contraction.
Multiaxial Joints
Joints that allow movement in multiple planes (e.g., ball-and-socket joints like the shoulder and hip).
Muscle Fiber
A single muscle cell that contracts in response to stimulation from a motor neuron.
Muscle Spindle
Proprioceptor located in muscle that detects changes in muscle length and initiates the stretch reflex.
Myocardium
The muscular tissue of the heart responsible for pumping blood.
Myofibril
Rod-like structures within a muscle fiber that contain sarcomeres and are responsible for contraction.
Myofilament
The protein filaments (actin and myosin) within myofibrils that interact to produce muscle contraction.
Myosin
Thick filament protein in muscle that forms crossbridges with actin during contraction.
Neuromuscular junction
The synapse where a motor neuron meets a muscle fiber, allowing for transmission of the action potential.
Parasympathetic Nervous System (PNS)
Part of the autonomic nervous system that promotes relaxation, digestion, and recovery.
Perimysium
Connective tissue sheath that surrounds fasciculi (bundles of muscle fibers).
Pleura
Double-layered membrane surrounding the lungs, providing lubrication and protection during respiration.
Pleural Pressure
Pressure in the pleural cavity; helps maintain lung expansion during breathing.
Power stroke
The phase during muscle contraction when myosin pulls actin filaments, resulting in shortening of the sarcomere.
Proprioceptor
Sensory receptor that detects changes in body position, movement, and muscle tension.
Proximal
Anatomical term indicating a position closer to the trunk or point of origin (e.g., the shoulder is proximal to the hand).
Pulmonary Valve
Valve between the right ventricle and pulmonary artery; prevents backflow of blood into the ventricle during diastole.
Purkinje Fibers
Specialized cardiac fibers that transmit electrical impulses to the ventricles, ensuring coordinated contraction.
P-wave
Part of an ECG representing atrial depolarization, which triggers atrial contraction.
QRS Complex
Part of an ECG representing ventricular depolarization, which triggers ventricular contraction.
Red blood cell (RBC)
Cells responsible for carrying oxygen to tissues and removing carbon dioxide via hemoglobin.
Repolarization
Return of the cell membrane’s electrical charge to its resting state after depolarization.
Right bundle branch
Transmits electrical impulses from the AV node to the right ventricle, aiding in synchronized contraction.
Sarcolemma
The cell membrane of a muscle fiber that conducts action potentials.
Sarcomere
The basic contractile unit of a muscle fiber, made up of overlapping actin and myosin filaments.
Sarcoplasm
Cytoplasm of a muscle fiber, containing organelles, glycogen, and myoglobin.
Sarcoplasmic Reticulum
Specialized endoplasmic reticulum in muscle cells that stores and releases calcium for muscle contraction.
Semilunar Valves
Valves in the heart (pulmonary and aortic) that prevent backflow of blood into the ventricles.
Sinoartial (SA) Node
The heart’s natural pacemaker, located in the right atrium, initiating each heartbeat.
Sliding Filament Theory
A theory which explains muscle contraction as actin filaments sliding over myosin filaments, shortening the sarcomere.
Slow-twitch muscle fiber
Muscle fibers that contract slowly, generate less force, and resist fatigue (Type I fibers).
Superior
Anatomical term indicating a position above or higher than another part of the body (e.g., the head is superior to the chest).
Sympathetic Nervous System (SNS)
Part of the autonomic nervous system that increases heart rate, blood pressure, and energy output during stress.
Synovial fluid
Lubricating fluid in synovial joints, reducing friction and nourishing cartilage.
Synovial joints
Highly movable joints with a synovial cavity, such as the knee, hip, and shoulder.
Systole
Phase of the cardiac cycle when the heart contracts to pump blood out of the chambers.
Tachycardia
A resting heart rate above 100 beats per minute.
Tendon
Dense connective tissue that connects muscle to bone, transmitting force to produce movement.
Tetanus
Sustained muscle contraction resulting from rapid, repeated stimulation without relaxation.
Trachea
The windpipe; a tube that connects the larynx to the bronchi, allowing air to flow to the lungs.
Tricuspid valve
Valve between the right atrium and right ventricle, preventing backflow of blood into the atrium during contraction.
Tropomyosin
Protein that blocks myosin-binding sites on actin filaments, preventing contraction in a relaxed muscle.
Troponin
Protein complex that regulates muscle contraction by binding calcium and moving tropomyosin to expose myosin-binding sites.
T-tubule
Invaginations of the sarcolemma that conduct action potentials deep into muscle fibers.
T-wave
Part of an ECG representing ventricular repolarization.
Twitch
A single, brief contraction of a muscle fiber in response to a single action potential.
Type I Fiber
Slow-twitch muscle fibers; high oxidative capacity, fatigue-resistant, suited for endurance activities.
Type IIa Fiber
Fast-twitch muscle fibers; moderate oxidative and glycolytic capacity, suited for both power and endurance activities.
Type IIx Fiber
Fast-twitch muscle fibers; high glycolytic capacity, fatigue quickly, generate high force, suited for explosive activities.
Uniaxial joints
Joints that allow movement in one plane, such as the hinge joint in the elbow.
Vein
Blood vessel that carries deoxygenated blood toward the heart, except for the pulmonary veins which carry oxygenated blood.
Veinous system
Network of veins that return deoxygenated blood to the heart from various parts of the body.
Ventricle
Lower chambers of the heart that pump blood; right ventricle pumps to the lungs, left ventricle pumps to the body.
Venule
Small blood vessels that collect blood from capillaries and transport it to veins.
Vertebral Column
Bony structure made up of vertebrae that protects the spinal cord and supports the body.
Z-line
Boundary between adjacent sarcomeres in a myofibril; anchors thin filaments (actin) and shortens during contraction.
Which of the following substances regulates muscle actions?
- Potassium
- Calcium
- Troponin
- Tropomyosin
Calcium
Calcium binds to troponin, causing tropomyosin to move and expose the myosin-binding sites on actin, allowing muscle contraction to occur.
Which of the following substances acts at the neuromuscular junction to excite the muscle fibers of a motor unit?
- Acetylcholine
- ATP
- Creatine Phosphate
- Serotonin
Acetylcholine
Acetylcholine is the neurotransmitter released at the neuromuscular junction that binds to receptors on the muscle fiber, triggering an action potential and initiating muscle contraction.
From which of the following is the heart’s electrical impulse typically initiated?
- AV node
- SA node
- the brain
- the sympathetic nervous system
SA node
The sinoatrial (SA) node is the heart’s natural pacemaker, generating electrical impulses that set the rhythm for heartbeats.
When throwing a baseball, an athlete’s arm is rapidly stretched just before throwing the ball. Which of the following structures detects and responds to that stretch by reflexively increasing muscle activity?
- Golgi tendon organ (GTO)
- Muscle spindle
- Extrafusal muscle
- Pacinian corpuscle
Muscle spindle
Muscle spindles detect changes in muscle length and trigger a stretch reflex, which increases muscle activity to prevent overstretching.
Which of the following occurs during the QRS complex of a typical ECG:
I. Depolarization of the atrium
II. Repolarization of the atrium
III. Repolarization of the ventricle
IV. Depolarization of the ventricle
- I & III only
- II & IV only
- I, II, & III only
- II, III, & IV only
II & IV only
The QRS complex represents repolarization of the atrium (II) and depolarization of the ventricle (IV). Atrial depolarization is represented by the P-wave, while ventricular repolarization occurs during the T-wave.
