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Anatomy Ch. 6


4 major functional characteristics of skeletal muscle Contractility, excitibility, extensibility, & elasticity
Contractility The ability of skeletal muscle to shorten with force
Excitability The capacity of skeletal muscle to respond to a stimulus
Extensibility The ability to be stretched
Epimysium Connective tissue sheath that surrounds each skeletal muscle
Fascia Another connective tissue located outside the epimysium
Perimysium Loose connective tissue that surrounds the muscle fasciculi
Fibers Single muscle cells
Endomysium Connective tissue sheath that surrounds each fiber
Myofibrils A threadlike structure that extends from one end of the fiber to the other
Actin myofilaments Thin myofilaments
Myosin myofilaments Thick myofilaments
Sarcomeres Highly ordered units which are joined end to end to form the myofibril
Resting membrane potential The charge difference across the membrane
Action potential The brief reversal back of the charge
Motor neurons Nerve cells that carry action potentials to skeletal muscle fibers
Neuromusclular junction/synapse Formed from each branch that connects to the muscle
Motor unit A single motor neuron and all the skeletal muscle fibers it innervates
Presynaptic terminal The enlarged nerve terminal
Synaptic cleft The space between the presynaptic terminal and the muscle cell
Postsynaptic terminal The muscle fiber
Synaptic vesicles Secretes neurotransmitters in the presynaptic terminal
Acetylcholine Diffuses across the synaptic cleft and binds to the postsynaptic terminal causing a change in the postsynaptic cell
Acetylcholinesterase Ensures that one action potential in the neuron yields only one action potential in the skeletal muscle, and only one contraction of the muscle cell
Sliding filament mechanism Sliding of actin myofilaments past myosin myofilaments during contraction
Muscle twitch Contraction of an entire muscle in response to a stimulus that causes action potential
Threshold The maximum a muscle can contract
All-or-none response A muscle fiber will not respond to stimulus until it reaches the threshold
Lag phase Time between application of a stimulus to the beginning of a contraction
Contraction phase Time of contraction
Relaxation phase Time when the muscle relaxes
Tetany Where the muscle remains contracted without relaxing
Recruitment The increase if motor units being activated
ATP Needed for energy for muscle contraction
ADP More stable ATP
Creatine phosphate A high-energy molecule
Anaerobic respiration Without oxygen
Aerobic respiration With oxygen
Oxygen debt Amount of oxygen needed in chemical reactions to convert lactic acid to glucose and to replenish the depleted stores of creating phosphate in muscle cells
Muscle fatigue Results when ATP is used during muscle contraction faster than it can be produced in the muscle cells
Isometric and isotonic 2 types of muscle contractions
Isometric Equal distance
Isotonic Equal tension
Muscle tone Constant tension produced by muscles of the body for long periods of time
Fast-twitch fibers Contract quickly and fatigue quickly
Slow-twitch fibers Contract more slowly and are more resistant to fatigue
Origin The most stationary end of the muscle
Insertion The end of the muscle undergoing the greatest movement
Belly The portion of the muscle between the origin and the insertion
Synergists Muscles that work together to accomplish specific movements
Antagonists Muscles that work in opposition to one another
Prime mover Among a group of synergists, it's the one muscle that plays the major role in accomplishing the desired movement
Occipitofrontalis Raises eyebrows
Orbicularis oculi Closes eyelids
Orbicularis oris Puckers lips
Buccinator Flattens cheeks
Kissing muscles Orbicularis oris and buccinator
Zygomaticus Smiling muscle
Levator labii superioris Sneering
Depressor anguli oris Frowning
Mastication Chewing
Temporalis and masseter 4 pairs of pterygoids, ,and .
Intrinsic Change the shape of the tongue
Extrinsic Move the tongue
Strenocleidomastiod Lateral neck muscle and prime mover. Rotates and abducts the head
Erector spinae Group of muscles on each side of the back. Responsible for keeping the back straight and the body erect.
External intercostals Elevate the ribs during inspiration.
Internal intercostals Contract during forced expiration.
Diaphragm Accomplishes quiet breathing. Dome-shaped muscle. Aids in breathing.
Linea alba This tendinous area of the abdominal wall
Rectus abdominis On each side of the linea alba
Tendinous inscriptions Cross the rectus abdominis at three or more locations, causing the abdominal wall of a well-muscled person to appear segmented
Trapezius Rotates scapula
Serratus anterior Pulls scapula anteriorly
Pectoralis major Adducts and flexes the arm
Latissimus dorsi Medially rotates, adducts, and powerfully extends the arm.“Swimmer muscles”
Deltoid Attaches the humerus to the scapula and clavicle, and is the major abductor of the upper limb.
Triceps brachii Extends the forearm. Occupies the posterior compartment of the arm.
Biceps brachii Flexes the forearm. Occupies the anterior compartment of the arm.
Brachialis Flexes forearm
Brachioradialis Flexes and supinates the forearm.
Retinaculum (bracelet) Strong band of fibrous connective tissue that covers the flexor and extensor tendons and holds them in place around the wrist so that they do not “bowstring” during muscle contraction.
Flexor carpi Flexes the wrist.
Extensor carpi Extends the wrist
Flexor digitorum Flexes the fingers.
Extensor digitorum Extends the fingers.
Intrinsic hand muscles Located within the hand
Interossi Located between the metacarpals, are responsible for abduction and adduction of the fingers.
Gluteus maximus Buttocks. Contributes most of the mass of the buttocks. Gluteus medius,hip muscle and common injection site.
Quadriceps femoris Extends the leg; anterior thigh muscles
Sartorius “Tailors muscle”; flexes the thigh
Hamstring muscles Posterior thigh muscles; flexes the leg and extends the thigh.
Gastrocnemius and soleus Form the calf muscle
Calcaneal tendon (Achilles tendon) Flex the foot and toes
Peroneus Muscles are primarily everters (turning the lateral side of the foot outward) of the foot, but they also aid in plantar flexion.
Intrinsic foot muscles 20 muscles that flex extend, abduct, and adduct the toes.
Created by: meganpreece
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