Chapter 1: Structure and Function of Body Systems Flashcards
Describe the axial skeleton.
Skull (cranium)
Vertebral column (C1 through coccyx)
Sternum
Rib cage
Describe the appendicular skeleton.
Shoulder (pectoral girdle): scapulae, clavicles
Arm and wrist bones: humerus, radius, ulna, carpals, metacarpals, phalanges
Pelvic girdle (coxal or innominate bones)
Leg and ankle bones: femur, patella, fibula, tibia, tarsals, metatarsals, phalanges
Joints
Articulations between bones
Fibrous joints
Joints that allow no movement (e.g. sutures of the skull)
Cartilaginous joints
Joints that allow for limited movement (e.g. intervertebral disks)
Synovial joints
Joints that allow for considerable movement (e.g. elbow, knee)
Hyaline cartilage
Cartilage that covers articulating bone ends
Synovial fliud
Viscous fluid that lubricates a joint
Uniaxial joints
Joints that rotate around a single axis (e.g. elbow)
Biaxial joints
Joints that rotate around two perpendicular axes (e.g. wrist, ankle)
Multiaxial
Joints that rotate around all three perpendicular axes that define space (e.g. ball-and-socket joints - hip, shoulder)
Vertebral column
Cervical spine: C1-C7
Thoracic spine: T1-T12
Lumbar spine: L1-L5
Sacral spine: S1-S5 (fused together, form rear of pelvis)
+ 3-5 coccygeal vertebrae
Epimysium
sheath of connective tissue surrounding the outside of a muscle
Perimysium
sheath of connective tissue surrounding a bundle of muscle fibers
Endomysium
sheath of connective tissue surrounding a single muscle fiber
Tendon
Strong, fibrous connective tissues that attaches muscle to bone
Bone periosteum
Connective tissue that covers all bones, except at the surface of the joints
Proximal
Denotes a limb muscle attachment closer the the trunk
Distal
Denotes a limb muscle attachment further from the trunk
Superior
Denotes a trunk muscle attachment closer to the head
Inferior
Denotes a trunk muscle attachment further from the head
Muscle fiber
Muscle cells; long and cylindrical with a diameter similar to that of a human hair (50-100 micrometers); multinucleate with striated appearance under magnification
Fasciculi
A bundle of muscle fibers
Sarcolemma
Membrane of a muscle cell
Motor neuron
Nerve cell
Neuromuscular junction
The junction between a motor neuron and the muscle fiber(s) it innervates
Motor unit
Motor neuron + muscle fiber(s) it innervates
Sarcoplasm
Cytoplasm of a muscle fiber
Myofibrils
Bundles of contractile protein filaments (actin and myosin)
Myosin
Thick filaments; globular head + hinge point + tail fibrous tail
Actin
Thin filaments; two strands arranged in a double helix
Crossbridge
Sarcomere
The smallest contractile unit of skeletal muscle
A-band
Area in the center of the sarcomere where myosin and actin overlap; length never changes length during contraction
I-band
Actin only; shortens during contraction
H-zone
Myosin only; shortens during contraction
M-line
Center of the sarcomere (and center of the A-band) and attachment site for myosin
Z-line
Defines the boundary of a sarcomere; bisects the I-band of neighboring sarcomeres
Sarcoplasmic reticulum
Specialized endoplasmic reticulum in muscle cells dedicated to storage of calcium
T-tubules
Invaginations in the sarcoplasmic reticulum that conduct impulses (action potentials) from the sarcolemma deeper into the cell
Action potential
An electrical nerve impulse that signals the release of calcium from the sarcoplasmic reticulum into the myofibril and causes tension development in a muscle
Sliding filament theory
Actin filaments at each end of the sarcomere slide inward on myosin filaments, pulling the Z-lines closer to the center of the sarcomere and shortening the muscle fiber
Troponin
Tropomyosin
Power stroke
Explain the steps of muscle contraction
- Action potential travels from the motor neuron via neurotransmitter acetylcholine, which stimulates the release of calcium into the myofibril once it reaches the muscle.
- Calcium binds to troponin, which causes tropomyosin to shift and expose protein-binding sites on actin filaments.
- Myosin binds to actin to form a cross-bridge.
- ATP on myosin is broken down via ATPase into ADP and phosphate, which provides energy for the power stroke (pulling action). Sarcomeres are shortened (I-band and H-zone)
- Another molecule of ATP replaces ADP on myosin cross-bridge globular head, which detaches from active actin site and returns to its original position.
- Stimulation of motor neuron stops, calcium is pumped back into the SR, and actin and myosin return to unbound sites.
Acetylcholine
Neurotransmitter that diffuses across the neuromuscular junction and causes excitation of the sarcolemma
All-or-none principle
All muscle fibers in the motor unit contract and develop force at the same time. It’s all or none!
Twitch
