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73 terms

A&P Chapter 6 - Muscles

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Sarcolemma
Specialized plasma membrane that surrounds myofibrils and nuclei
Myofibrils
Contractile organelles found in cytoplasm of muscle cells; have 2 bands
Actin
Thin band of muscle protein that joins other bands at z-disc; helical shape
Myosin
Thick band of muscle protein that joins other bands at H zone; contains ATPase enzymes
Sarcomere
Smallest contractile unit of muscle from one z-disc to the next
Cross bridges
Myosin heads that link thick and thin bands during muscle contraction
Sarcoplasmic reticulum
Muscle fiber organelle that surrounds each myofibril; stores calcium and releases when muscle is signaled to contract
Excitability
Muscle's ability to receive and respond to a stimulus
Contractility
Muscle's ability to shorten with an adequate stimulus
Extensibility
Muscle's ability to lengthen
Elasticity
Muscle's ability to recoil and resume resting length
Motor unit
One motor neuron and all the skeletal muscle cells stimulated by that neuron
Neuromuscular junction
Association site of the axon terminal of the motor neuron and muscle
Action potential
An electrical event occurring when a stimulus of sufficient intensity is applied to a neuron or muscle cell, allowing sodium ions to move into the cell and reverse polarity
Direct phosphorylation of ADP by CP
When ATP is depleted, it leaves ADP. CP transfers a phosphate group to ADP, regenerating more ATP; exhausted in ~15 sec.
Aerobic respiration
Respiration where oxygen is consumed and glucose is broken down into water, carbon dioxide, and 32 ATP; occurs in the mitochondria by a series of metabolic pathways that use oxygen. The reaction overall is slow and requires continuous oxygen
Anaerobic glycosis and lactic acid formation
Glucose breaks down in cytosol without oxygen, resulting in pyruvic acid that converts to lactic acid; creates 2 ATP per 1 glucose. Process is 2x faster than aerobic respiration
Isotonic contraction
When myofilaments are able to slide past each other during contractions; muscle shortens and movement occurs
Isometric contraction
When tension in the muscle increases but the muscle is unable to shorten or produce movement
Origin
Muscle attachment to an immovable bone
Insertion
Muscle attachment to a moveable bone
Flexion
Decreases the angle of a joint that brings 2 bones closer together
Extension
Increases the angle of a joint
Hyperextension
Extension beyond 180 degrees
Rotation
Movement of a bone around a longitudinal axis
Abduction
Moving a limb away from the midline
Adduction
Moving a limb toward the midline
Circumduction
A combination of flexion, extension, abduction, and adduction; proximal end is stationary and distal end is in motion
Prime mover
Muscle with the major responsibility for a certain movement
Antagonist
Muscle that opposes or reverses a prime mover
Synergist
Muscle that aids a prime mover in a movement and helps prevent unnecessary movement
Fixator
A specialized synergist that stabilizes the origin of a prime mover
Circular muscle
When the fascicles are arranged in concentric rings
Convergent muscle
The fascicles converge toward a single insertion tendon
Parallel muscle
Fascicles run parallel to the long axis of the muscle
Fusiform muscle
Fascicles run parallel to the long axis of the muscle, but have an enlarged belly; football shaped
Pennate
Short fascicles attach obliquely to a central tendon
Frontalis
Unpaired muscle that covers the frontal bone, allows eyebrows to raise
Orbicularis oculi
Circular muscle around the eyes, allowing for blinks, winks, and squints
Orbicularis oris
Unpaired circular muscle around the mouth, allowing for puckering and kissing
Buccinator
Muscle on the face just inferior to the zygomaticus; allows for cheek flattening and chewing
Zygomaticus
Muscle on the face that allows for smiling
Masseter
Muscle on the face that allows for the jaw to close
Temporalis
Muscle that covers the temporal bone and synergizes with the masseter to close the jaw
Platysma
Unpaired muscle that covers the anterior surface of the neck, allowing for frowning
Sternocleidomastoid
2-headed muscle found on either side of the neck; allows for neck flexion and lateral rotation
Pectoralis major
Convergent muscle covering the upper part of the chest; flexes and adducts the humerus
External intercostals
Muscles that lie between the ribs; allow rib cage to raise during inhalation
Internal intercostals
Muscles that lie deep between the ribs; allow rib cage to depress and exhale
Rectus abdominis
Paired, strap-like muscles most superficial on the abdomen; allows for flexion of vertebral column, compresses abdominal contents, and aids in childbirth, defecation, and forced breathing
External obliques
Muscles that make up the lateral wall of abdomen; flexes vertebral column, rotates trunk, allows for lateral bending
Internal obliques
Deep muscles with fibers running adjacent to and function with external obliques
Transverse abdominis
Deepest muscle of the abdominal wall; compresses abdominal contents
Trapezius
Most superficial muscles of the posterior upper trunk; extends the head, and moves the scapula
Latissimus dorsi
Large flat muscles that cover the lower back; extend and adduct the humerus
Erector spinae
Deep muscle group that is the prime mover of back extension; also stabilizes spine when bending over
Quadratus lumborum
Muscle that forms a small part of the posterior abdominal wall; flexes the spine laterally and together extend the lumbar spine
Deltoid
Prime mover of arm abduction
Biceps brachii
Prime mover of elbow flexion; also allows for supination of the forearm
Brachialis
Muscle that lies deep to biceps brachii; flexes elbow
Brachiordialis
Weak muscle in the brachial region
Triceps brachii
Prime mover of elbow extension, antagonist to biceps brachii
Gluteus maximus
Largest muscle; very powerful hip extensor
Gluteus medius
Lies deep to gluteus maximus; allows for thigh abduction and steadies pelvis when walking
Ilipsoas
Fused muscles on the lower limb; prime mover of hip flexion, keeps upper body from falling back when standing
Adductor muscles
Muscle group found on medial thigh; allows for thigh adduction and medial rotation
Hamstring group
Muscle group forming the mass of posterior thigh; prime movers of thigh extension and knee flexion
Sartorius
Thin strap-like muscle; weak hip flexor
Quadriceps group
Muscle group that forms the mass of the anterior thigh; extends knee, helps to flex hip
Tibialis anterior
Superficial muscle on anterior leg; allows for dorsiflexion and inversion
Fibularis muscles
Muscle group found on the lateral part of the leg; allows for plantar flexion and eversion
Gastrocnemius
Muscle that forms the calf; prime mover for plantar flexion
Soleus
Muscle deep to the gastrocnemius; helps in plantar flexion