Do the movement yourself
Move your own joint the way the prompt describes. Feel which side of the joint tightens.Lab 9 takes the muscles you identified in Lab 8 and asks what each one does. You will demonstrate movements on yourself, name the prime mover and its antagonist, and read a muscle's action from where it attaches. This review teaches the roles, the joint-by-joint action tables, and the antagonistic pairs, then lets you practice on pull-line diagrams and in a timed practical.
Your lab manual wins. Lab sections vary in which models, slides, and terms they use. If anything here differs from your lab handout or what your instructor emphasized, go with your lab material and tell your tutor so this review can be updated.
Concept Review
Lab 8 asked where a muscle is. Lab 9 asks what it does. Every answer comes from one rule: a muscle can only pull, and when it shortens it pulls its insertion toward its origin. If you know where the two ends attach and which joint lies between them, you can work out the action.
| Term | Meaning | Elbow example (lifting a cup) |
|---|---|---|
| Origin | The attachment that stays fixed during the movement; usually proximal | Biceps brachii: scapula (supraglenoid tubercle and coracoid process) |
| Insertion | The attachment that moves; usually distal | Biceps brachii: radial tuberosity |
| Action | The movement produced when the muscle contracts | Flexes the elbow; supinates the forearm |
| Agonist (prime mover) | The muscle most responsible for the movement | Brachialis and biceps brachii |
| Antagonist | Opposes the agonist; relaxes and stretches during the movement, then reverses it | Triceps brachii |
| Synergist | Assists the prime mover or cancels an unwanted motion | Brachioradialis |
| Fixator | A synergist that holds the origin bone still so the prime mover has a stable base | Rotator cuff and scapular muscles steadying the scapula |
Roles depend on the movement. No muscle is permanently an agonist. When you flex the elbow, biceps is the agonist and triceps is the antagonist. When you extend it (pushing up from a chair), the roles swap. On a practical, always ask: "Which movement are we talking about?"
Naming note: some courses call biceps brachii the prime mover of elbow flexion; others give that title to brachialis, because it flexes the elbow in every forearm position. Accept either, and know that both are prime movers in most texts, with brachioradialis as the synergist.
Concept Review
You cannot name a prime mover until you can name the movement. This is the Chapter 9 vocabulary you will use in every Lab 9 station. All movements are described from anatomical position.
| Movement pair | What happens | Where you will be asked about it |
|---|---|---|
| Flexion / extension | Decrease / increase the angle between bones, in the sagittal plane. Hyperextension goes past anatomical position. | Shoulder, elbow, wrist, fingers, hip, knee, trunk, neck |
| Abduction / adduction | Move away from / toward the midline, in the frontal plane | Shoulder (arm), hip (thigh), wrist, fingers |
| Medial (internal) / lateral (external) rotation | Turn a bone around its long axis, toward / away from the midline | Shoulder, hip; head rotation at the atlas |
| Circumduction | Flexion, abduction, extension, and adduction in sequence; traces a cone | Shoulder, hip |
| Pronation / supination | Palm turns posterior (down) / anterior (up); the radius crosses over and back | Forearm (radioulnar joints) |
| Dorsiflexion / plantar flexion | Toes up toward the shin / toes point down (standing on tiptoe) | Ankle |
| Inversion / eversion | Sole turns medially / laterally | Intertarsal joints of the foot |
| Elevation / depression | Lift up / lower down | Scapula (shrug), mandible (close / open mouth) |
| Protraction / retraction | Move forward / backward in a horizontal plane | Scapula (reaching forward / squeezing shoulder blades), mandible |
| Opposition | Thumb pad touches a fingertip | Carpometacarpal joint of the thumb |
💭 Use the joint position rule. A muscle that lies on the anterior side of the shoulder, elbow, wrist, or hip usually flexes it; a muscle on the posterior side usually extends it. The knee and ankle are the exceptions you must memorize: the anterior thigh (quadriceps) extends the knee, the posterior thigh (hamstrings) flexes it, and the anterior leg dorsiflexes while the calf plantar flexes.
Label It · Elbow
Anterior is to the right in this lateral view. Pins mark the muscles that move the elbow and the bones they pull. Click a pin, choose, then press Check answers.
Action Tables
| Movement | Prime mover(s) | Synergists | Antagonists |
|---|---|---|---|
| Flexion (arm forward) | Pectoralis major (clavicular part), deltoid (anterior fibers) | Coracobrachialis, biceps brachii | Latissimus dorsi, posterior deltoid |
| Extension (arm back) | Latissimus dorsi, deltoid (posterior fibers) | Teres major, triceps (long head) | Pectoralis major, anterior deltoid |
| Abduction (arm out to side) | Deltoid (middle fibers) | Supraspinatus (starts the movement) | Pectoralis major, latissimus dorsi |
| Adduction (arm to side) | Pectoralis major, latissimus dorsi | Teres major | Deltoid, supraspinatus |
| Medial rotation | Subscapularis | Pectoralis major, latissimus dorsi, teres major | Infraspinatus, teres minor |
| Lateral rotation | Infraspinatus | Teres minor, posterior deltoid | Subscapularis |
| Scapula: elevation (shrug) | Trapezius (upper fibers), levator scapulae | Rhomboids | Lower trapezius, pectoralis minor |
| Scapula: retraction | Rhomboids, trapezius (middle fibers) | Serratus anterior | |
| Scapula: protraction (punch, reach) | Serratus anterior | Pectoralis minor | Rhomboids, trapezius |
| Movement | Prime mover(s) | Synergists | Antagonists |
|---|---|---|---|
| Elbow flexion | Brachialis, biceps brachii | Brachioradialis | Triceps brachii |
| Elbow extension | Triceps brachii | Anconeus | Brachialis, biceps brachii |
| Supination (palm up) | Supinator, biceps brachii | Pronator teres, pronator quadratus | |
| Pronation (palm down) | Pronator quadratus, pronator teres | Supinator, biceps brachii | |
| Wrist flexion | Flexor carpi radialis, flexor carpi ulnaris | Palmaris longus | Wrist extensors |
| Wrist extension | Extensor carpi radialis longus and brevis, extensor carpi ulnaris | Extensor digitorum | Wrist flexors |
| Wrist abduction (radial deviation) | Flexor carpi radialis + extensor carpi radialis longus | FCU + ECU | |
| Wrist adduction (ulnar deviation) | Flexor carpi ulnaris + extensor carpi ulnaris | FCR + ECRL | |
| Finger flexion / extension | Flexor digitorum superficialis and profundus / extensor digitorum | Each other |
Read the name: "flexor carpi radialis" flexes the wrist and, working with a radial extensor, tilts the hand toward the radius (abduction). "Extensor carpi ulnaris" extends the wrist and, with FCU, tilts it toward the ulna (adduction). Most forearm actions are written right into the name.
Label It · Shoulder
This is the model's right side seen from the front, so the midline (sternum) is on your right and the arm is slightly abducted. Click a pin, choose, then press Check answers.
Action Tables
| Movement | Prime mover(s) | Synergists | Antagonists |
|---|---|---|---|
| Flexion (knee toward chest) | Iliopsoas (iliacus + psoas major) | Rectus femoris, sartorius, tensor fasciae latae, adductors | Gluteus maximus, hamstrings |
| Extension | Gluteus maximus (forceful: climbing, rising from a squat) | Hamstrings (walking) | Iliopsoas, rectus femoris |
| Abduction | Gluteus medius | Gluteus minimus, tensor fasciae latae | Adductor group |
| Adduction | Adductor longus, brevis, magnus | Gracilis, pectineus | Gluteus medius |
| Lateral rotation | Gluteus maximus, deep lateral rotators (e.g., piriformis) | Sartorius | Gluteus medius and minimus (anterior fibers) |
| Movement | Prime mover(s) | Synergists | Antagonists |
|---|---|---|---|
| Knee extension (kick) | Quadriceps femoris (rectus femoris + three vasti) | Hamstrings | |
| Knee flexion (heel to buttock) | Hamstrings (biceps femoris, semitendinosus, semimembranosus) | Gastrocnemius, sartorius, gracilis | Quadriceps femoris |
| Dorsiflexion (toes up) | Tibialis anterior | Extensor digitorum longus | Gastrocnemius, soleus |
| Plantar flexion (tiptoe) | Gastrocnemius, soleus (triceps surae) | Fibularis longus, tibialis posterior | Tibialis anterior |
| Inversion (sole in) | Tibialis anterior, tibialis posterior | Fibularis longus and brevis | |
| Eversion (sole out) | Fibularis (peroneus) longus and brevis | Tibialis anterior and posterior | |
| Toe extension | Extensor digitorum longus | Toe flexors |
Two-joint muscles. Rectus femoris crosses the hip and the knee, so it flexes the hip and extends the knee. The hamstrings cross both too: they extend the hip and flex the knee. Gastrocnemius crosses the knee and ankle: it plantar flexes the ankle and helps flex the knee. Soleus crosses only the ankle, so it is a pure plantar flexor. Expect at least one practical question on this.
Label It · Hip & Knee
Anterior is to the right. Click a pin, choose, then press Check answers.
Label It · Leg & Ankle
Anterior is to the right. The front of the leg dorsiflexes; the calf plantar flexes; the lateral leg everts. Click a pin, choose, then press Check answers.
Action Tables
| Movement | Prime mover(s) | Notes / antagonists |
|---|---|---|
| Trunk flexion (sit-up) | Rectus abdominis | Obliques assist; antagonist: erector spinae |
| Trunk extension, posture | Erector spinae | Antagonist: rectus abdominis |
| Trunk rotation, lateral flexion | External and internal obliques | External oblique of one side works with the internal oblique of the other side |
| Compress abdomen (forced exhale, cough) | Transversus abdominis | With the obliques |
| Inspiration | Diaphragm | External intercostals elevate the ribs |
| Forced expiration | Internal intercostals, abdominal muscles | Quiet expiration is passive recoil |
| Neck flexion | Sternocleidomastoid (both sides) | Antagonist: trapezius and deep neck extensors |
| Head rotation | Sternocleidomastoid (one side) | Turns the face to the opposite side |
| Elevate mandible (close jaw, chew) | Masseter, temporalis | Temporalis also retracts the mandible |
| Depress mandible (open mouth) | Digastric (with gravity) | Platysma assists |
| Expression or movement | Muscle |
|---|---|
| Raise eyebrows, wrinkle forehead (surprise) | Frontalis (epicranius) |
| Close the eye, blink, squint | Orbicularis oculi |
| Close and pucker the lips (kiss, whistle) | Orbicularis oris |
| Smile (pull mouth corner up and out) | Zygomaticus major |
| Compress the cheek (blow, suck, keep food on teeth) | Buccinator |
| Tense the neck skin, pull lower lip down (grimace) | Platysma |
Antagonistic Pairs
Antagonists sit on opposite sides of the same joint. Learn these as pairs; when a station names one, the other is usually the follow-up question.
| Agonist for movement A | Its antagonist | Movement A vs movement B |
|---|---|---|
| Biceps brachii / brachialis | Triceps brachii | Elbow flexion vs extension |
| Quadriceps femoris | Hamstrings | Knee extension vs flexion |
| Tibialis anterior | Gastrocnemius + soleus | Dorsiflexion vs plantar flexion |
| Iliopsoas | Gluteus maximus | Hip flexion vs extension |
| Gluteus medius | Adductor group | Hip abduction vs adduction |
| Deltoid | Pectoralis major + latissimus dorsi | Arm abduction vs adduction |
| Pectoralis major | Latissimus dorsi | Arm flexion vs extension |
| Rectus abdominis | Erector spinae | Trunk flexion vs extension |
| Wrist flexors (FCR, FCU) | Wrist extensors (ECRL, ECRB, ECU) | Wrist flexion vs extension |
| Supinator + biceps | Pronator teres + pronator quadratus | Supination vs pronation |
| Tibialis anterior / posterior | Fibularis longus / brevis | Inversion vs eversion |
| Serratus anterior | Rhomboids | Scapular protraction vs retraction |
Check Yourself
Two tries per question. Red marks the muscle that is contracting.
Rapid Recall
Say the answer out loud, then tap the card to check. Shuffle and go again until every card is automatic.
Practical Simulation
This runs like a real lab practical: name the pinned muscle, its action, or the prime mover for a described movement. You type the answer, with no word bank. For actions, write the movement with its joint when you can (for example, "elbow flexion" or "dorsiflexion"). Your score and every correct answer appear at the end.
20 stations · 50 seconds each · stations come in random order every attempt.
| # | Station | Your answer | Correct |
|---|
Watch Out
| The mistake | The fix |
|---|---|
| Saying the quadriceps "flex" the knee because they are anterior | The knee is the exception: anterior thigh extends the knee, posterior thigh flexes it. |
| Writing "flexion" when the station asks about the ankle | At the ankle use dorsiflexion (toes up) and plantar flexion (toes down). |
| Calling a muscle "the antagonist" without naming the movement | Roles change with the movement. Biceps is the agonist for elbow flexion and the antagonist for elbow extension. |
| Thinking muscles push | Muscles only pull: insertion moves toward origin. The opposite movement needs a muscle on the other side of the joint. |
| Giving only one action for a two-joint muscle | Rectus femoris: hip flexion + knee extension. Hamstrings: hip extension + knee flexion. Gastrocnemius: plantar flexion + knee flexion. |
| Turning the head the wrong way for SCM | One SCM turns the face to the opposite side. |
| Mixing up supination and pronation | Supination = palm up, "holding a bowl of soup." Pronation = palm down. |
| Listing deltoid as an adductor | Deltoid abducts. Pectoralis major and latissimus dorsi adduct. |
Cheat Sheet
Print it or screenshot it for a last look before the lab.
| Topic | Know this |
|---|---|
| Roles | Agonist / prime mover does it; antagonist opposes; synergist helps; fixator stabilizes the origin |
| Origin vs insertion | Origin fixed, usually proximal; insertion moves, usually distal; insertion is pulled toward origin |
| Position rule | Anterior flexes, posterior extends (shoulder, elbow, wrist, hip). Knee is reversed. Ankle: anterior dorsiflexes, calf plantar flexes |
| Shoulder | Flex: pectoralis major, anterior deltoid. Extend: latissimus dorsi. Abduct: deltoid (+ supraspinatus). Adduct: pectoralis major + latissimus dorsi. Medial rot: subscapularis. Lateral rot: infraspinatus, teres minor |
| Scapula | Elevate: trapezius, levator scapulae. Retract: rhomboids. Protract: serratus anterior |
| Elbow / forearm | Flex: brachialis, biceps (brachioradialis). Extend: triceps. Supinate: supinator, biceps. Pronate: pronator teres, quadratus |
| Wrist | Flex: FCR, FCU (palmaris longus). Extend: ECRL, ECRB, ECU. Fingers: FDS/FDP vs extensor digitorum |
| Hip | Flex: iliopsoas. Extend: gluteus maximus (+ hamstrings). Abduct: gluteus medius. Adduct: adductor group, gracilis |
| Knee | Extend: quadriceps femoris. Flex: hamstrings (gastrocnemius, sartorius assist) |
| Ankle / foot | Dorsiflex: tibialis anterior. Plantar flex: gastrocnemius, soleus. Invert: tibialis anterior/posterior. Evert: fibularis longus/brevis |
| Trunk | Flex: rectus abdominis. Extend: erector spinae. Rotate: obliques. Compress: transversus abdominis |
| Breathing | Inspiration: diaphragm, external intercostals. Forced expiration: internal intercostals, abdominals |
| Head / jaw | SCM: one side turns face opposite, both flex neck. Close jaw: masseter, temporalis |
| Face | Frontalis raises brows; orbicularis oculi closes eye; orbicularis oris purses lips; zygomaticus smiles; buccinator compresses cheek |
Debrief
You can now name the prime mover and antagonist for the main movements at every major joint. Next up is Lab 10 and Lab Exam 3: the brain, cranial nerves, reflexes, and autonomic responses.
💭 Before the real thing: run the practical simulation until you score 90% or better twice in a row. Then do it once with the timer on.