The Muscular System Flashcards by Ava Thompson

Skeletal muscle cell shape and appearance

Single, very long, cylindrical, multinucleate cells with very obvious striations

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Cardiac muscle cell shape and appearance

Branching chains of cells; uninucleate, striations; intercalated discs

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Smooth muscle cell shape and appearance

Single, fusiform (bulge in the middle), uninucleate; no striations

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Circular Muscle Arrangement

Fascicles arranged in concentric rings

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Convergent Muscle Arrangement

Fascicles converge toward central insertion tendon

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Parallel Muscle Arrangement

Fascicles run parallel to the long axis of the muscle
- Fusiform: type of parallel arrangement in which muscle bulges at the middle

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Pennate Muscle Arrangement

“Feather” pattern - short fascicles attach obliquely to a central tendon

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Def. Motor Unit

One neuron and all the skeletal muscle fibers it stimulates

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Properties of Muscle Fiber

Responsiveness: ability to receive and respond to stimulus
Contractility: ability to produce force and shorten
Extensibility: ability to stretch
Elasticity: ability to resume resting length after being stretched

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Name the 5 “Golden Rules” of Skeletal Muscle Activity

Almost all skeletal muscles cross at least one joint
Bulk of skeletal muscles lies proximal to the joint crossed
All skeletal muscles have at least 2 attachments: the origin and insertion
Can only pull - they never push
During contraction, a skeletal muscle insertion moves towards the origin

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Origin

End of muscle attached to immovable or less movable bone

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Insertion

End of muscle attached to the moveable bone

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Lever

A simple machine consisting of a rigid beam that pivots at a fixed hinge (fulcrum)

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Mechanical Advantage

The ratio of output force to the input force (Load/Effort)

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Class I Lever

Fulcrum between the effort and load
- Can either amplify force or increase range of motion
- Ex: Nodding head

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Class II Lever

Load between the effort and fulcrum
- Force multiplier lever
- Mech. Advantage > 1
- Ex: Raising to balls of feet

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Class III Lever

Effort between the fulcrum and load
- Range of motion/speed multiplier lever
- Mech. Advantage < 1
- Ex: Bending Elbow

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Flexion

Decreases the angle of the joint, brings two bones closer together, generally in the sagittal plane
Ex: Bending the knee or elbow

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Extension

Increases the angle of joint, brings two bones farther apart (Opp. of flexion)
Ex: Straightening the knee or elbow

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Hyperextension

Extension more than 180 degrees

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Rotation

Movement of bone around the longitudinal axis

Ex: Shaking head “no”

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Abduction

Moving a limb away from the midline

Ex: Spreading fingers apart

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Adduction

Moving a limb towards the midline (Opp. of abduction)

Ex: Bringing arms toward the body

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Circumduction

Proximal end of limb is stationary while distal end moves in a circle
- common in ball and socket joints
- Ex: shoulder, hip

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Dorsiflexion and plantar flexion

Up and down movement of the foot and ankle - Dorsiflexion: pointing toe toward head (flex foot) - Plantar flexion: pointing toe away from head (point foot)

Inversion and eversion

Medial/lateral movements of the foot - Inversion: movement of sole in medial direction - Eversion: movement of sole in lateral direction

Supination and pronation

Movements of radius around the ulna - Supination: forearm rotation so that palm faces anteriorly - Pronation: forearm rotation so that palm faces posteriorly

Opposition

Movement of thumb to touch tips of other fingers

Agonist

A muscle that produces a given movement - Prime mover: muscle that has the primarily responsibility for causing a particular movement

Antagonist

Muscles that oppose or reverse a movement - Typically stretched when the agonist is contracted

Synergist

Help prime movers by producing the same movement or reducing undesirable movements

Fixator

Specialized synergist - Hold the origin bone of prime mover still so that all muscle force goes toward moving insertion bone

A muscle that crosses on the anterior side of a joint produces _____.

Flexion

A muscle that crosses on the posterior side of a joint produces _____.

Extension

A muscle that crosses on the lateral side of a joint produces _____.

Abduction

A muscle that crosses on the medial side of a joint produces ______.

Adduction

Frontalis (function)

Raise eyebrows, wrinkle forehead

Orbicularis oculi (location, function)

Circular muscle around eye; Closes eye, squinting, blinking

Zygomaticus (function)

Smiling muscle

Masseter (function)

Closes jaw

Sternocleidomastoid (location, function)

One on each side of the neck; Neck flexion (bowing the head)

Intercostal muscles (location, function)

Between ribs; Important for respiration - External intercostals: elevate and expand rib cage (help w/ inhalation) - Intern intercostals: compress rib cage (help w/ exhalation)

Rectus abdominus (location, function)

Flex vertebral column; most superficial abdominal muscle

External and internal oblique (location, function)

External is outermost abdominal muscle, internal is right under external oblique; flex vertebral column, rotation and lateral bending of trunk

Transverse abdominis (location, function)

Deepest abdominal muscle; compress abdominal contents

Deltoid (function)

Abducts arm

Pectoralis major (function)

Adducts and flexes humerus

Trapezius (function)

Raises, retracts, and rotates the scapula

Latissimus dorsi (function)

Extends and adducts humerus

Biceps brachii (function)

Flexes elbow and supinates forearm

Brachialis (function)

Flexes elbow

Brachioradialis (function)

Flexes elbow

Triceps brachii (function)

Extends elbow

Flexor carpi radialis (function)

Flexes wrist and abducts hand

Flexor carpi ulnaris (function)

Flexes wrist and adducts hand

Flexor digitorum superficials (function)

Flexes wrist and fingers

Extensor carpi radialis (function)

Extends wrist and abducts hand

Extensor digitorum (function)

Extends fingers

Gluteus maximus (function)

Extends hip

Gluteus medius (function)

Abducts thigh

Iliopsoas (function)

Flexes hip

Adductor muscles (function)

Adduct and medially rotate thigh

Hamstring group (function)

Flex knee and extend hip

Sartorius (function)

Flexes hip and knee

Quadriceps group (function)

Extends knee

Tibialis anterior (function)

Dorsiflexes and inverts foot

Extensor digitorum longus (function)

Extends toes

Fibularis muscles (function)

Plantar flex and evert foot

Gastrocnemius (function)

Flexes knee, plantar flexes foot

Soleus (function)

Plantar flexes foot

Orbicularis Oris (location, function)

Circular muscle around lips; closes mouth, protrudes lips