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Chapter 6

Muscular System

The ability of skeletal muscle to shorten with force Contractility
The capacity of skeletal muscle to respond to a stimulus Excitability
Ability to be stretched Extensibility
Ability to recoil to their resting length Elasticity
Connective tissue that surrounds skeletal muscle Epimysium
Connective tissue located outside epimysium Fascia
Numerous visible bundles found in muscle Fasciculi
Loose connective tissue that surrounds fasciculi Perimysium
Muscle cells Muscle fibers
Connective tissue that surrounds each fiber Endomysium
The cytoplasm of each fiber is filled with Myofibrils
2 major kinds of protein fibers found in myofibrils Actin myofilament & Myosin myofilament
Thin myofilaments Actin
Thick myofilaments Myosin
Basic structural & functional unity of the muscle Sarcomere
Z line to Z line Sarcomere
Contains actin & is light I band
Extends length of myosin & is darker A band
Center of sarcomere that consists of only myosin H zone
Dark staining band in center M line
Outside the cell membranes is what charge? Positive
Inside of cell membranes is what charge? Negative
The brief reversal back of the charge is Action potential
Nerve cells that carry action potentials to skeletal muscle fibers Motor neurons
Neuromusclular junction Synapse
Raises the eyebrow Occipitofrontalis
Closes the eyelids & causes "crows feet" Orbicularis oculi
Flattens the cheeks Buccinator
Kissing muscles Orbicularis oris & buccinator
Smiling muscle Zygomaticus
Sneering Levator labii superioris
Frowning Depressor anguli oris
Chewing Mastication
4 pairs of chewing muscles 2 pterygoids, temporalis, masseter
Changes shape of tongue Intrinsic tongue
Moves the tongue Extrinsic tongue
Lateral neck muscle & prime mover; rotates & abducts the head Sternocleidomastoid
The space between the presynaptic terminal & postsynaptic terminal (muscle fiber) is Synaptic cleft
Neurotransmitter Acetylcholine
Enzyme breaks down Acetylcholinesterase
Muscular system produces Heat
Attaches muscle to bone Tendons
Sliding of actin past myosin during contraction Sliding filament mechanism
Sarcomeres shorten causes Muscles to shorten
Contraction of an entire muscle in response to a stimulus that causes action potential in one or more muscle fibers Muscle twitch
Muscle fiber will contract maximally All-or-nothing response
Time between application of stimulus to motor neuron and beginning of contraction is called Lag phase
ATP Adenosine triphosphate
Needed for energy for muscle contraction ATP
ATP is produced in the Mitochondria
ATP cannot stock pile, so it stores another Creatine phosphate
Without oxygen Anaerobic respiration
With oxygen (more efficient) Aerobic respiration
When ATP is used during muscle contraction faster than it can be produced Muscle fatigue
2 types of muscle contractions Isometric & Isotonic
Length doesn't change, tension increases Ex: holding a ball Isometric
Tension is constant, length changes Ex: throwing a ball Isotonic
Contract quickly & fatigue quickly; well for anaerobic Fast-twitch fibers
Contract slowly & more resistant to fatigue; aerobic Slow-twitch fibers
Points of attachment on each muscle Origin & insertion
Most stationary end of muscle (Head) Origin
End of muscle undergoing greatest movement Insertion
Portion between origin & insertion Belly
Bicep attaches at scaplua Origin
Bicep attaches at radius Insertion
Muscles that work together to accomplish specific movements Synergists
Muscles work in opposition to one another Antagonists
Plays major role in a group of synergists Prime mover
Muscles are named according to Location & size
3 types of muscle in the body Skeletal, cardiac, smooth
Union between a nerve fiber & a muscle fiber Neuromuscular junction
What does the muscular system do Permits movement of the body, maintains posture, & circulates blood throughout the body
Group of muscles on each side of back; responsible for keeping the back straight & body erect Erector spinae
Accomplishes quiet breathing; dome-shaped muscle; aids in breathing Diaphragm
Tendinous area of the abdominal wall; consists of white connective tissue Linea alba
On each side of the lines alba Rectus abdominis
Cross the rectus abdominis at 3 or more locations, causing a person to look segmented Tendinous inscriptions
Abdominis layers of muscle from superficial to deep External abdominal oblique, internal abdominal oblique, & transverses abdominal muscles
Rotates scapula Trapezius
Elevates the ribs during inspiration External intercostals
Adducts & flexes the arm Pectoralis major
Medially rotates, adducts, & powerfully extends the arm; "Swimmer muscles" Latissimus dorsi
Most involved in breathing External intercostals & internal intercostals
Attaches the humerus to the scapula & clavicle & is major abductor of upper limb Deltoid
Extends the forearm Triceps brachii (posterior)
Flexes the forearm Biceps brachii (anterior)
Also flexes the forearm Brachialis
Flexes and supinates the forearm Brachioradialis
Flexes the wrist Flexor carpi
Extends the wrist Extensor carpi
Flexes the fingers Flexor digitorum
Extends the fingers Extensor digitorum
19 hand muscles located within hand Intrinsic hand muscles
Contract during forced expiration Internal intercostals
Buttocks Gluteus maximus
Hip muscle & common injection site Gluteus medius
Extends the leg Quadriceps femoris (anterior)
Flexes the thigh Sartorius "Tailors muscle"
Flexes leg & extends thigh Hamstrings (posterior)
Form the calf muscle; flexes foot & toes Gastrocnemius & soleus (Calcaneal tendon)
Lateral muscles of leg; turns foot outward & plantar flexion Peroneus muscles
20 muscles within foot Intrinsic foot
Created by: paymorrone12