TEAS 💪 Muscular System SE

💪 Muscular System

The BIG idea:

MUSCLES = MOVEMENT

Muscles contain special cells called muscle fibers that can contract (shorten/tighten).

When they contract → they create movement.

---

🧠 What are muscle fibers?

Muscle fibers = muscle cells

Think:

💪 Muscle = made of many muscle fibers

And:

Muscle fiber contracts → muscle contracts → movement happens

⭐ Memory:

"Fiber fires → muscle moves."

🦴 How do muscles move your body?

Muscles often attach to bones.

When a muscle contracts, it pulls on the bone.

Example:

💪 Muscle contracts
⬇
🦴 Pulls bone
⬇
🦾 Arm moves

Important:

Muscles pull — they don't push.

That's a good TEAS concept to remember.

---

🫀 Muscles aren't only attached to bones!

Muscles can also attach to:

• 🫀 Internal organs

• 🩸 Blood vessels

• 🦴 Bones

So muscles help control lots of things inside your body too.

🔥 Other jobs of muscles

Besides movement:

1. 🏃 Movement

Muscles contract → body moves.

2. 🧍 Support

Help hold your body up and maintain posture.

3. 🦴 Joint stability

Help keep joints stable.

4. 🌡 Heat

Muscle contractions produce heat.

🧠 Think:

SHIVERING = muscles contracting → HEAT 🔥

💪 How many muscles?

There are 600+ muscles in the human body.

You don't need to memorize every muscle for this section.

Just know:

600+ muscles = movement + support + stability + heat

⭐ TEAS MEMORY TRICK

Remember:

muscles

M-S-S-H

M → Movement
S → Support
S → Stabilize joints
H → Heat

🧠 Phrase:

"Muscles Move, Support, Stabilize, and Heat."

And the most important chain:

MUSCLE FIBER → CONTRACTS → MUSCLE PULLS → MOVEMENT

🔥 Fiber fires → muscle moves.

🦴 Stabilize a joint = keep it steady and in the right position.

A joint is where two bones meet, like your knee, shoulder, or elbow.

Your muscles around the joint help hold the bones in place so the joint doesn't move around too much.

Example: 🦵 Knee

When you're standing:

Muscles around knee → tighten slightly → help keep knee steady → you don't wobble

So:

STABILIZE = KEEP STEADY 🔒

Stabilize = Stop unwanted movement

Muscles don't just help you move — they also help control and steady your joints.

Movement = make it move 🏃
Stability = keep it steady 🔒

💪 THE 3 TYPES OF MUSCLE

There are only 3:

❤ Cardiac🦴 Skeletal🫃 Smooth

The easiest way to learn them is to ask 2 questions:

1. Where is it?

2. Can I control it?

❤ 1. CARDIAC =

HEART

Cardiac muscle is ONLY in the heart.

Its job:

❤ Pump blood

You cannot consciously tell your heart to beat.

So:

Cardiac = INVOLUNTARY

🧠 Memory trick:

CARDIAC → CARDIO → HEART ❤

And:

Heart = automatic

What does it look like?

Cardiac muscle is:

• Striated = has stripes

• Short

• Branched

• Usually 1 nucleus

Don't worry too much about the shape yet.

🦴 2. SKELETAL =

BONES + VOLUNTARY

Skeletal muscle is attached to your bones.

Its job:

🏃 Move your body

You can consciously control it.

Examples:

• Walking

• Raising your hand

• Kicking

• Smiling

So:

Skeletal = VOLUNTARY

🧠 Memory trick:

SKELETAL → SKELETON → BONES

And:

Skeletal = YOU control it

What does it look like?

• Striated = stripes

• Long

• Cylindrical

• Many nuclei

🫃 3. SMOOTH =

ORGANS

Smooth muscle is found in the walls of internal organs.

Examples:

• Stomach

• Bladder

• Intestines

• Blood vessels

It helps move things through your body automatically.

You don't consciously control it.

So:

Smooth = INVOLUNTARY

🧠 Memory trick:

SMOOTH = organs work automatically

And it looks:

• Not striated = NO stripes

• Spindle-shaped

• Usually 1 nucleus

Muscle	Where?	Control	Stripes?
❤ Cardiac	Heart	Involuntary	✅ Yes
🦴 Skeletal	Attached to bones	Voluntary	✅ Yes
🫃 Smooth	Internal organs	Involuntary	❌ No

❤ CARDIAC = HEART = AUTOMATIC

🦴 SKELETAL = SKELETON = YOU CONTROL

🫃 SMOOTH = ORGANS = AUTOMATIC

---

🧠 STRIPES TRICK

Cardiac + Skeletal = STRIPED

Smooth = NO STRIPES

Think:

“Cardiac and skeletal wear STRIPES. Smooth is SMOOTH.” 😂

🔬 What does "striated" mean?

Don't let this word scare you.

Striated = striped

That's it!

If you see:

Striated muscle

Think:

🟰 STRIPES

🧠 What does "involuntary" mean?

you DON'T control it consciously.

Your heart beats without you thinking:

"Okay heart, beat now." 😂

Your stomach also moves food without you telling it to.

So:

INvoluntary = NOT under your conscious control

Voluntary = YOU control it.

Skeletal = voluntary

🔥 NOW THE 4 MUSCLE PROPERTIES

All three types of muscle have these four abilities.

Don't memorize the giant words first. Learn what they DO.

1. ⚡ Excitability

Muscle can respond to a signal/stimulation.

Think:

EXCITABILITY = responds

---

2. 💪 Contractility

Muscle can shorten/tighten.

Think:

CONTRACT = SHORTEN

---

3. 🧘 Extensibility

Muscle can stretch/lengthen.

Think:

EXTEND = STRETCH

---

4. 🪀 Elasticity

Muscle can return to its original shape after being stretched.

Think:

ELASTIC = BOUNCE BACK

⭐ EASY MEMORY FOR THE 4E-C-E-E

Excitability → respond ⚡
Contractility → shorten 💪
Extensibility → stretch 🧘
Elasticity → bounce back 🪀

Think of a rubber band:

Signal → responds → stretches → contracts → returns

🎯 TEAS RAPID REVIEW

If you see:

Heart?
➡ ❤ Cardiac

Attached to bones?
➡ 🦴 Skeletal

Stomach/bladder/intestines?
➡ 🫃 Smooth

Voluntary?
➡ 🦴 Skeletal

Involuntary?
➡ ❤ Cardiac + 🫃 Smooth

Striated?
➡ ❤ Cardiac + 🦴 Skeletal

Not striated?
➡ 🫃 Smooth

Muscle shortens?
➡ Contractility

Muscle stretches?
➡ Extensibility

Returns to original shape?
➡ Elasticity

Responds to stimulation?
➡ Excitability

🔥 ONE LINE TO MEMORIZE

❤ Cardiac = heart + automatic | 🦴 Skeletal = bones + YOU control | 🫃 Smooth = organs + automatic

First: What is skeletal muscle doing?

Nervous system → tells muscle to contract → muscle shortens → pulls bone → bone moves

Think:

🧠 Brain/nerves = boss
💪 Muscle = worker
🦴 Bone = thing being moved

Important:

Muscles PULL, they don't push.

When a skeletal muscle contracts (shortens) → it pulls on a bone → movement happens.

🧠 Now the confusing part: Endomysium →

Perimysium → Epimysium

Think of a bunch of straws inside a bundle.

🥤 Imagine a muscle like a bundle of straws:

1 straw = muscle fiber
A bunch of straws = fascicle
The whole bundle = muscle

And each level gets its own wrapping.

From SMALLEST → BIGGEST:

Muscle fiber
⬇ wrapped by ENDOMYSIUM
⬇ fibers grouped together
Fascicle (bundle)
⬇ wrapped by PERIMYSIUM
⬇ many fascicles grouped together
Whole muscle
⬇ wrapped by EPIMYSIUM

---

🔥 THE BIG 3 TO MEMORIZE

Layer	What does it wrap?	EASY TRICK
Endomysium	1 muscle fiber	ENDO = individual
Perimysium	Fascicle/bundle	PERI = package
Epimysium	Whole muscle	EPI = entire muscle

ENDO → PERI → EPI

Think:

Individual → Package → Entire

Or:

🧵 Fiber → Bundle → Muscle

💡 What is a fascicle?

A fascicle = bundle of muscle fibers.

Think of a bundle of pencils ✏

• 1 pencil = muscle fiber

• bunch of pencils = fascicle

• lots of bundles = whole muscle

So:

Muscle fiber → Fascicle → Muscle

⭐ TEAS FAVORITE ORDER

Memorize this:

Fiber → Fascicle → Muscle

And the coverings:

Endo → Peri → Epi

Put them together:

ENDO wraps FIBERS
⬇
PERI wraps FASCICLES
⬇
EPI wraps the ENTIRE muscle

🧠 One sentence to memorize:

“ENDO = fiber, PERI = bundle, EPI = entire muscle.”

🚨 30-SECOND TEAS REVIEW

Know these:

• Skeletal muscle contracts → shortens → pulls bone → movement

• Muscles pull, not push

• Muscle fiber = individual muscle cell

• Fascicle = bundle of muscle fibers

• Endomysium = wraps individual fibers

• Perimysium = wraps fascicles

• Epimysium = wraps entire muscle

🔥 FINAL MEMORY TRICK:

“ENDO = ONE, PERI = BUNDLE, EPI = EVERYTHING.”

If you remember that + Fiber → Fascicle → Muscle, you're in really good shape for this topic.

⚡ What about cardiac and smooth muscle?

Your first sentence is basically saying:

• 💪 Skeletal muscle: nervous system / excitatory stimulates it → usually voluntary

• ❤ Cardiac muscle: nervous system + hormones can influence it → involuntary

• 🫃 Smooth muscle: nervous system + hormones can influence it → involuntary

Quick memory:

Skeletal = YOU control it
Cardiac = HEART controls it
Smooth = ORGANS control it

💪 Skeletal Muscle: From BIG → SMALL

Think of a muscle like a building made of smaller and smaller parts:

Whole muscle → Fascicle → Muscle fiber → Myofibril → Sarcomere → Myofilaments

🧠 Think of it like this:

🏢 Whole muscle
→ 📦 Fascicle = bundle of muscle fibers
→ 🧵 Muscle fiber = one muscle cell
→ 🪢 Myofibril = long structures inside the fiber
→ ⚙ Sarcomere = smallest contractile unit
→ 🧶 Myofilaments = proteins inside the sarcomere

1⃣ Sarcolemma =

muscle cell membrane

The sarcolemma is simply the cell membrane of a muscle fiber.

Normal cell = cell membrane
Muscle cell = sarcolemma

🧠 Trick:

SARCO = muscle

So:

Sarcolemma = muscle cell membrane

2⃣ Sarcoplasm = muscle cell cytoplasm

The sarcoplasm is the cytoplasm inside the muscle fiber.

Normal cell = cytoplasm
Muscle cell = sarcoplasm

🧠 Trick:

SARCO = muscle

So:

Sarcoplasm = muscle cytoplasm

🔥 Easy pair:

SarcoLEMMA = membrane
SarcoPLASM = cytoplasm

3-5

3⃣ Myofibrils = long structures inside the muscle fiber

A muscle fiber contains many long structures called myofibrils.

Think of them like long strings inside the muscle cell.

🧠 Trick:

MYO = muscle

Myofibrils = long muscle structures that help it contract

4⃣ Sarcomere = smallest contractile unit ⭐

This is VERY important for the TEAS.

A sarcomere is the smallest unit that actually contracts.

Think:

🪢 Sarcomere = tiny section that shortens

🧠 Trick:

SARCOMERE = muscle's contraction unit

If you see:

"smallest contractile unit of skeletal muscle"

🚨 SARCOMERE

5⃣ Myofilaments = proteins inside the myofibril

There are two major types:

🔵 Thick = MYOSIN🟢 Thin = ACTIN

That's it!

Filament	Protein	Think
Thick	Myosin	Myo = thick
Thin	Actin	Actin = thin

MYOSIN = THICK
ACTIN = THIN

Or:

Myosin = MIGHTY thick 💪
Actin = thinner

6⃣ Z-disk = boundary/anchor

The Z-disk is where the thin actin filaments attach.

Think of the Z-disks as the ends of a sarcomere.

🧠 Trick:

Z = Zero/Zone boundary

Actin attaches to the Z-disk.

The Z-disc is the boundary/end of a sarcomere.

Think of a sarcomere like a tiny room:

Z-disc | ← sarcomere → | Z-disc

The actin (thin filament) is attached to the Z-disc and extends inward.

🧠 Memory trick:
“Z = the ends of the Zone.”

So if TEAS asks “Where does actin attach?” → Z-disc.

🧠 PUT IT ALL TOGETHER

Here's the whole story:

💪 Muscle

⬇
Fascicle = bundle of muscle fibers
⬇
Muscle fiber = one muscle cell
⬇
Myofibrils = long structures inside the fiber
⬇
Sarcomeres = smallest contraction units
⬇
Myofilaments = actin + myosin

⭐ THE 6 WORDS YOU REALLY NEEDSarcolemma

= muscle cell membrane

Sarcoplasm

= muscle cytoplasm

Myofibril

= long structures inside muscle fiber

Sarcomere

= smallest contractile unit

Myosin

= THICK filament

Actin

= THIN filament

🚨 SUPER EASY MEMORY STORY

Imagine a muscle factory:

🏭 Muscle
→ 📦 Fascicles
→ 🧵 Muscle fibers
→ 🪢 Myofibrils
→ ⚙ Sarcomeres
→ 🧶 Actin + Myosin

And remember:

“Sarco = muscle, Sarcomere = contracts, Myosin = thick, Actin = thin.”

🔥 TEAS rapid-fire

Q: Muscle cell membrane? → Sarcolemma
Q: Muscle cell cytoplasm? → Sarcoplasm
Q: Smallest contractile unit? → Sarcomere
Q: Thick filament? → Myosin
Q: Thin filament? → Actin
Q: Actin attaches to? → Z-disk

💪 Muscle order

BIG → SMALL

Memorize:

Muscle → Fascicle → Fiber → Myofibril → Sarcomere → Myofilaments

🔥 COOL TRICK:

“My Friend Found My Smallest Muscles”

• M = Muscle

• F = Fascicle

• F = Fiber

• M = Myofibril

• S = Sarcomere

• M = Myofilament

Even easier:

Think “Bundle → Cell → Strings → Tiny units → Proteins”

Muscle
⬇ bundles = Fascicle
⬇ cells = Fiber
⬇ strings = Myofibril
⬇ tiny contraction units = Sarcomere
⬇ proteins = Myofilaments (actin + myosin)

🚨 TEAS must-know:

Sarcomere = smallest contractile unit
Z-disc = sarcomere boundary + actin attaches there
Myosin = thick
Actin = thin

💪 Sarcomere Bands

1-2

First remember the layout:

Z | I | A | H | M | H | A | I | Z

Think of it like a mirror 🪞 — everything is centered around the M line.

---

🟨 1. Z-line = THE ENDS

The Z-line/Z-disc marks the boundary of a sarcomere.

It is also where actin attaches.

🧠 Trick:

Z = Zero point / Zone boundary

So:

Z = END + ACTIN ATTACHES

🟩 2. I-band = THIN ONLY

The I-band contains actin (thin filaments) only.

🧠 Trick:

I = “I only see thin.”

So:

I-band = thin ACTIN only

sarcomere 3-5

🟥 3. A-band = ALL

The A-band contains both thick AND thin filaments where they overlap.

🧠 BEST TRICK:

A = ALL

A-band = Actin + myosin

So:

A = ALL → thick + thin

---

🟦 4. H-zone = HEAVY ONLY

The H-zone is the middle part of the A-band and contains thick myosin only.

🧠 Trick:

H = Heavy → thick

So:

H-zone = thick/myosin only

---

🟪 5. M-line = MIDDLE

The M-line is right in the center of the sarcomere.

🧠 Easy:

M = Middle

🔥 THE FASTEST WAY TO MEMORIZE

You really only need these:

Z = ends I = thin only

A = ALL

H = thick only

M = middle

Put it together:

Z → I → A → H → M → H → A → I → Z

🧠 Think:

“Zebra Is Always Hungry, Man!” 😂

Z = Z-line
I = I-band
A = A-band
H = H-zone
M = M-line

Then it repeats backward:

H → A → I → Z

Part	What's there?	Memory
Z-line	Actin attaches	Z = ends
I-band	Thin/actin only	I = only thin
A-band	Thick + thin	A = ALL
H-zone	Thick/myosin only	H = Heavy
M-line	Center	M = Middle

“Z ends it, I is thin, A has ALL, H is heavy, M is middle.”

💪 Muscle Contraction

Think of myosin as little arms pulling on actin.

🟢 Actin = the rope🔵 Myosin = little arms⚡ ATP = energy🟡 Calcium = the “GO” signal

---

1⃣ Actin = thin filament

Actin proteins link together to make a long, thin chain.

Think:

🟢🟢🟢🟢🟢🟢🟢

Actin = the rope being pulled

---

2⃣ Myosin = thick filament

Myosin has little heads that stick outward.

Think of them like:

🏌🏌🏌🏌

Those heads grab onto actin.

🧠 Trick:

MYOSIN = little MUSCLE arms

3⃣ What happens during contraction?

Here's the important part:

⚡ ATP gives myosin energy

⬇
🔵 Myosin head grabs actin
⬇
🤝 Crossbridge forms
⬇
💪 Myosin pulls actin toward the M-line
⬇
📏 Sarcomere gets shorter
⬇
💪 Muscle contracts

🧠 Think:

GRAB → PULL → SHORTEN

🔄 Why does ATP matter?

After myosin pulls actin, the myosin head needs another ATP to reset/re-energize so it can grab and pull again.

Think of a hand pulling a rope:

✋ Grab → pull → release/reset → grab → pull → repeat

🔥 Memory:

ATP = energy to RESET the myosin head

🟡 What does calcium do?

This is REALLY important.

Calcium is stored in the:

Sarcoplasmic reticulum (SR)

Think of the SR as a calcium storage tank surrounding the myofibrils.

When calcium is released:

🟡 Calcium = GO!

It allows the myosin heads to access actin's binding sites so contraction can happen.

Calcium makes the actin binding sites available so myosin can grab actin.

⚡ ATP = gives myosin the energy to work

ATP helps the myosin head get energized/reset so it can grab and pull.

Think of it like a car 🚗:

Calcium = turns the green light on 🟢
ATP = gasoline/energy ⛽
Myosin = car doing the work
Actin = what gets pulled

So the basic idea is:

Calcium → binding site becomes available → ATP powers myosin → myosin grabs actin → pulls → contraction

🧠 THE WHOLE STORY

Memorize this:

CALCIUM → ATP → GRAB → PULL → SHORTEN

More simply:

🟡 Calcium says GO
⚡ ATP gives energy
🤝 Myosin grabs actin
💪 Myosin pulls actin
📏 Sarcomere shortens

---

🚨 TEAS MUST-KNOW

Actin = thin filament
Myosin = thick filament
Myosin heads = grab/pull actin
Crossbridge = myosin attached to actin
ATP = energy for myosin
Calcium = helps start contraction
Sarcoplasmic reticulum = stores calcium
M line = actin is pulled toward the center

🔥 BEST MEMORY TRICK:

“Calcium GO, ATP POWER, Myosin PULLS, Sarcomere SHORTENS.”

If you know that sentence, you understand the basic sliding-filament mechanism the TEAS is looking for.

🔥 Super important correction to my earlier shortcut

I said, “Calcium → ATP → grab → pull.” That's okay as a simplified memory, but calcium isn't simply the first chemical step and ATP isn't simply second. They have different roles.

For the TEAS, remember:

🟡 CALCIUM = UNLOCKS
⚡ ATP = POWERS
🔵 MYOSIN = PULLS
🟢 ACTIN = GETS PULLED

🦴 Joints

First, what's a joint?

A joint = where two bones meet.

Think:

🦴 + 🦴 = JOINT

And:

Ligament = bone → bone

🧠 Trick:

Ligaments LINK bones.

---

⭐ The 3 Types of Joints

The easiest way to memorize them is:

🚫 Immovable → 🤏 Partly movable → 🏃 Synovial

No movement → Some movement → LOTS of movement

1⃣ Immovable = 🚫 NO movement

The bones are held tightly together by connective tissue.

Example:

💀 Skull

Your skull bones aren't supposed to freely move around.

🧠 Memory:

IMMOVABLE = “I'M MOVING? NO.” 😂

Think skull = stuck

---

2⃣ Partly movable = 🤏 SOME movement

Bones are connected by cartilage.

Example:

🦴 Spine

The vertebrae can move a little, but they're not freely moving like your shoulder.

🧠 Memory:

CARTILAGE = SOME movement

Think of the spine as flexible but not loose.

3⃣ Synovial = 🏃 LOTS of movement

These joints have a joint cavity, giving the bones lots of freedom to move.

Examples:

🦵 Hip
💪 Shoulder

🧠 Memory:

SYNOVIAL = SWING!

Your shoulder and hip can move in many directions.

🔥 BEST TEAS MEMORY TRICK

Remember the movement scale:

I → P → S

Immovable = 🚫 NONE
Partly movable = 🤏 SOME
Synovial = 🏃 LOTS

Think:

“I Put Shoes” 👟
I → P → S

Then remember:

Joint	Movement	Example
Immovable	🚫 None	Skull
Partly movable	🤏 Some	Spine
Synovial	🏃 Lots	Hip, shoulder

🚨 One more important trick:

Ligament = bone to bone 🦴↔🦴

Joint = where bones meet 🦴 + 🦴

So if TEAS asks:

“What connects bone to bone?”

🔥 LIGAMENT

“Where do two bones meet?”

🔥 JOINT

“Which joint allows the most movement?”

🔥 SYNOVIAL

🦴 6 Synovial Joints

1-3

1⃣ Pivot joint 🔄

Turns/rotates around one axis.

📍 Example: neck

Think: PIVOT = TURN

🧠 “Pivot = swivel.”

---

2⃣ Hinge joint 🚪

Moves back and forth like a door.

📍 Examples: elbow, knee

Think: 🚪 DOOR HINGE

🧠 “Hinge = door.”

---

3⃣ Ball-and-socket joint ⚽

Moves almost every direction and can rotate.

📍 Examples: shoulder, hip

Think: ⚽ ball sitting in a socket

🧠 “Ball = ALL directions.”

Synovial joints

4-6

4⃣ Saddle joint 🐴

Moves back/forth + side/side.

📍 Example: thumb

Think: 🐴 a saddle lets you move in different directions.

🧠 “Saddle = thumb.”

---

5⃣ Condyloid joint ↔↕

Moves side-to-side and back-and-forth, but doesn't freely rotate like a ball-and-socket.

📍 Example: wrist

Think: wrist = wave 👋

🧠 “Condyloid = wrist.”

---

6⃣ Plane joint ↔

Bones slide/glide against each other.

📍 Examples: some wrist/ankle joints

Think: 🧊 two flat surfaces sliding

🧠 “Plane = slide.”

🔥 FASTEST TEAS MEMORY TABLE

joints

Joint	Movement	Memory
Pivot	🔄 Rotate	PIVOT = TURN
Hinge	↕ Back/forth	HINGE = DOOR
Ball & socket	🔄 All directions	BALL = ALL
Saddle	↔ + ↕	SADDLE = THUMB
Condyloid	↔ + ↕, limited rotation	WRIST = WAVE
Plane	↔ Slide	PLANE = SLIDE

🧠 THE CRAZY-EASY 6 WORDS

Just memorize:

PIVOT = TURN

HINGE = DOOR

BALL = ALL

SADDLE = THUMB

CONDYLOID = WRIST

PLANE = SLIDE

💪 1. Tendon =

muscle → bone

A tendon connects muscle to bone.

When the muscle contracts:

Muscle shortens → tendon pulls bone → bone moves

🧠 BEST TRICK:

TENdon = connects muscle to bone

Don't mix it up with a ligament:

• Tendon = muscle → bone 💪➡🦴

• Ligament = bone → bone 🦴➡🦴

🔥 Tendon = TIES muscle to bone

💪 2. Muscles work in PAIRS

Muscles can only pull, so you need opposite muscles to move a joint in opposite directions.

Think of two people pulling a rope from opposite sides.

One contracts → the other relaxes/lengthens.

flexor vs extensor

🦾 3. Flexor = BENDS

A flexor muscle contracts to bend a joint.

Example: Biceps

When your biceps contracts:

💪 Biceps shortens
⬇
🦴 pulls forearm
⬇
💪 Elbow bends

🧠 FLEX = FLEX your arm → BEND

---

🦾 4. Extensor = STRAIGHTENS

An extensor contracts to straighten a joint.

Example: Triceps

When your triceps contracts:

💪 Triceps shortens
⬇
🦴 pulls forearm
⬇
➡ Elbow straightens

🧠 EXTEND = make it LONGER/STRAIGHTER

🔥 BICEPS vs TRICEPS

Muscle	What happens when it contracts?	Job
Biceps	Elbow bends	Flexor
Triceps	Elbow straightens	Extensor

BIceps = BEND 💪
TRIceps = TRIes to STRAIGHTEN

Or even simpler:

FLEX = BEND

EXTEND = STRAIGHT

🔄 The most important idea

When biceps contracts, the triceps relaxes.

When triceps contracts, the biceps relaxes.

They switch jobs.

Think:

🔵 Biceps ON → Triceps OFF → bend
🔴 Triceps ON → Biceps OFF → straighten

🚨 TEAS CHEAT CODE

Memorize these 4:

TENDON = muscle → bone

LIGAMENT = bone → bone

FLEXOR = bends

EXTENSOR = straightens

And the classic example:

Biceps = flexor = bends elbow
Triceps = extensor = straightens elbow

🔥 If you see “muscle attaches to bone” → TENDON.
🔥 If you see “bone attaches to bone” → LIGAMENT.

💪 MUSCULAR SYSTEM — TEAS CHEAT SHEET1⃣ What does muscle do?

Muscles have 3 big jobs:

• 💪 Move the body

• 🧍 Support the body/posture

• 🔥 Make heat

🧠 Trick: “Muscles MOVE, SUPPORT, HEAT.”

---

2⃣ The 3 muscle types

Muscle	Where?	Control	Stripes?
💪 Skeletal	Bones	Voluntary	✅ Yes
❤ Cardiac	Heart	Involuntary	✅ Yes
🫃 Smooth	Organs	Involuntary	❌ No

🔥 SUPER EASY TRICK:

Skeletal = Skeleton = YOU control it

Cardiac = Cardio = Heart = automatic

Smooth = organs = automatic

Stripes:

Skeletal + Cardiac = STRIPES
Smooth = NO stripes

3⃣ Skeletal muscle coverings

but it's just 3 wrapping layers:

Endomysium → Perimysium → Epimysium

Think:

Fiber → Bundle → Whole muscle

• Endomysium → wraps one muscle fiber

• Perimysium → wraps a fascicle/bundle

• Epimysium → wraps the whole muscle

🧠 🔥 Trick:

ENDO = ONE
PERI = PACKAGE
EPI = ENTIRE

4⃣ What's inside a muscle fiber?

Muscle fiber

⬇
contains myofibrils
⬇
myofibrils contain actin + myosin

Think:

🧵 Fiber = big container
🪢 Myofibrils = strings inside
🟢 Actin + 🔵 Myosin = proteins that contract

5⃣ How does muscle contraction happen?

This is the sliding filament theory.

Don't overthink it:

Myosin grabs Actin → pulls Actin → sarcomere gets shorter → muscle contracts

“GRAB → PULL → SHORTEN.”

Myosin = the puller
Actin = what gets pulled

⚡ ATP = energy
🟡 Calcium = helps turn contraction ON

6⃣ Tendons vs joints

6⃣ TendonsTendon = muscle → bone

Muscle contracts → tendon pulls bone → movement.

🧠 Trick:

TENdon TIES muscle to bone

🚨 Don't mix it up:

Tendon = muscle → bone
Ligament = bone → bone

---

7⃣ JointsJoint = where bones meet

Joints determine how much movement/flexibility you can have.

🧠 Think:

🦴 + 🦴 = JOINT

---

8⃣ Muscles work in pairs

Muscles pull, so they need opposing muscles to move a joint in different directions.

Example:

💪 Biceps contracts → elbow bends

💪 Triceps contracts → elbow straightens

🧠 Remember:

FLEX = BEND
EXTEND = STRAIGHTEN

---

🚨 THE ULTIMATE TEAS MEMORY SHEET

If you're short on time, memorize THIS:

💪 Muscle jobs

MOVE + SUPPORT + HEAT

🧍 Muscle types

Skeletal = voluntary + striped
Cardiac = involuntary + striped
Smooth = involuntary + no stripes

🧵 Muscle layers

ENDO = fiber
PERI = fascicle
EPI = whole muscle

🪢 Contraction

Myosin pulls Actin → Sarcomere shortens → Muscle contracts

🔗 Connections

TENDON = muscle → bone
LIGAMENT = bone → bone

🦴 Movement

Flexor = bends
Extensor = straightens

🔥 One giant memory line:

“Skeletal moves, cardiac beats, smooth organs; endo wraps fiber, peri wraps bundle, epi wraps all; myosin pulls actin; tendon connects muscle to bone; flex bends, extend straightens.”

💪 3 Muscle Types — FAST

Muscle	Stripes?	Shape	Nuclei	Memory
💪 Skeletal	✅ Striped	Long + cylindrical	Many	Skeletal = LONG + MANY
❤ Cardiac	✅ Striped	Short + branched	1	Cardiac = BRANCHED + 1
🫃 Smooth	❌ No stripes	Smooth/spindle-shaped	1	Smooth = NO STRIPES + 1

🔥 EASIEST TRICK:

Skeletal = STRIPES + LONG + MANY

Cardiac = STRIPES + BRANCHES + ONE

Smooth = NO STRIPES + ONE

🧠 Quick visual:

💪 Skeletal: ━━━━━━━━━ → long

❤ Cardiac: Y Y Y → branched

🫃 Smooth: ◇ ◇ ◇ → no stripes

🚨 TEAS MUST-KNOW:

Skeletal = long, striped, many nuclei
Cardiac = short, branched, striped, one nucleus
Smooth = no stripes, one nucleus

Stripe trick:
👉 Skeletal + Cardiac = stripes
👉 Smooth = no stripes

• 💪 Skeletal muscle = muscles attached to bones → move your skeleton → usually voluntary

• ❤ Cardiac muscle = muscle only in the heart → pumps blood → involuntary

• 🫃 Smooth muscle = muscle in the walls of organs and blood vessels → moves/controls things inside your body → involuntary

🧠 Super easy memory:

SKELETAL → SKELETON 🦴
CARDIAC → CARDIO ❤
SMOOTH → STOMACH/ORGANS 🫃

So for the TEAS:

Bones = Skeletal
Heart = Cardiac
Organs/blood vessels = Smooth

Most blood vessels have smooth muscle in their walls.

But the blood vessel is not made entirely of smooth muscle. It has several layers, and the middle layer contains smooth muscle.

🩸 Super easy:

Blood vessel wall → smooth muscle → can tighten or relax

• Smooth muscle contracts → vessel gets narrower (vasoconstriction)

• Smooth muscle relaxes → vessel gets wider (vasodilation)

🧠 TEAS trick:

Smooth muscle = organs + blood vessels

So when you see blood vessels, think SMOOTH muscle.