Exam Prep

1. Basic Components of a Human Cell

A human cell contains several essential structures that work together to maintain life, energy production, and communication. The plasma membrane surrounds the cell and controls what enters and leaves, maintaining internal conditions. Inside, the cytoplasm holds organelles such as mitochondria, which generate ATP, and the endoplasmic reticulum (ER)—rough ER makes proteins while smooth ER synthesizes lipids and detoxifies chemicals. The Golgi apparatus modifies, sorts, and packages proteins for secretion or internal use. Lysosomes and peroxisomes break down waste and harmful substances. The cytoskeleton—made of microfilaments, microtubules, and intermediate filaments—gives the cell shape and aids in movement. The nucleus, enclosed by a double membrane, stores DNA and directs cellular activities through gene expression, making it the information and control center of the cell.

Fun Summary

• 🧱 Membrane: security gatekeeper.

• ⚡ Mitochondria: ATP power stations.

• 🏭 ER: protein (RER) + lipid (SER) factories.

• 📦 Golgi: packaging & shipping center.

• 🗑 Lysosomes: trash and recycling units.

• 🧬 Nucleus: the boss with the DNA.

• 🕸 Cytoskeleton: cell scaffolding + transport highway.

2. Events at the Neuromuscular Junction and Start of Contraction

At the neuromuscular junction (NMJ), an action potential travels down a motor neuron and depolarizes the axon terminal, opening voltage-gated Ca²⁺ channels. The influx of Ca²⁺ causes synaptic vesicles to fuse with the membrane and release acetylcholine (ACh) into the synaptic cleft. ACh binds to nicotinic receptors on the muscle motor end plate, opening ligand-gated ion channels that allow Na⁺ to enter, producing an end plate potential. If threshold is reached, a muscle action potential spreads across the sarcolemma and into T-tubules, activating the dihydropyridine receptor (DHP), which then triggers the ryanodine receptor (RyR) on the sarcoplasmic reticulum. This releases a large amount of Ca²⁺, which binds to troponin, moves tropomyosin aside, and allows actin–myosin cross-bridge cycling to begin—resulting in muscle contraction.

Fun Summary

• ⚡ Neuron fires → Ca²⁺ rushes in.

• 💬 Vesicles dump ACh into the cleft.

• 🔑 ACh unlocks Na⁺ channels → end plate potential.

• 🔥 Muscle AP races across fiber → T-tubules.

• 📢 DHP says “GO!” → RyR dumps Ca²⁺ from SR.

• 💪 Ca²⁺ hits troponin → contraction begins!

3. Features That Create the Resting Membrane Potential (RMP)

The resting membrane potential is created by an imbalance of ions across the plasma membrane, mainly due to selective permeability and ion pumps. The Na⁺/K⁺ ATPase pump moves 3 Na⁺ out and 2 K⁺ in, creating both a concentration gradient and a net negative internal charge. Because the membrane is far more permeable to K⁺ than Na⁺, K⁺ leaks out through potassium channels, leaving behind negatively charged proteins, further making the inside more negative. This stabilizes the typical RMP (around −70 mV). Cells use changes in membrane potential for communication—for example, neurons generate action potentials when membranes depolarize, allowing rapid long-distance signaling rapidly along axons. These electrical signals coordinate movement, sensation, and thought across the nervous system.

Fun Summary

• 🔋 Na⁺/K⁺ pump: 3 out, 2 in → negativity inside.

• 🚪 K⁺ leak channels: the real MVP for RMP.

• 🧲 Charged proteins stuck inside add negativity.

• ⚡ Neurons flip the charge → action potentials → communication highway.

4. Structure & Function of the Plasma Membrane + Three Junction Types

The plasma membrane of eukaryotic cells is a phospholipid bilayer with embedded proteins, cholesterol, and carbohydrates. Its amphipathic design allows it to form a selective barrier, separating internal and external environments while regulating transport, cell signaling, and cell adhesion. Integral and peripheral proteins serve functional roles such as channels, receptors, enzymes, and structural anchors. Cholesterol helps maintain fluidity, while glycoproteins and glycolipids assist in recognition and communication.

Tight Junctions

These form a continuous seal between neighboring cells, preventing substances from leaking between them. They help maintain polarity by separating apical and basolateral membrane domains, especially in epithelial tissues like the gut.

Adhering Junctions (Adherens Junctions)

These junctions link actin filaments between cells through cadherin proteins, providing strong mechanical stability. They help tissues maintain shape and resist tension, important in heart muscle and epithelial layers.

Gap Junctions

These create protein channels (connexons) between adjacent cells, allowing ions and small molecules to pass directly from cell to cell. This is essential for electrical and metabolic coupling—such as synchronized contraction in cardiac muscle.

Fun Summary

• 🧱 Plasma membrane: flexible, selective, lipid-protein fortress.

• 🚫 Tight junctions: “No leaks allowed!”

• 🤝 Adhering junctions: tissue glue + structural support.

• 🔌 Gap junctions: cell-to-cell electrical chat rooms.!

Below are medium-sized paragraphs with expanded, fun, and detailed bullet summaries for each topic.

5. Initiation & Propagation of an Action Potential in an Alpha Motor Neuron and Its Effect on Skeletal Muscle

An action potential in an alpha motor neuron begins when excitatory synaptic inputs depolarize the cell body and axon hillock to threshold, triggering the opening of voltage-gated Na⁺ channels. Rapid Na⁺ influx produces the rising phase of the action potential. As the AP propagates down the axon, Na⁺ channels in adjacent segments open in a wave, while K⁺ channels open later to repolarize the membrane. In myelinated alpha motor neurons, the AP "jumps" between nodes of Ranvier via saltatory conduction, greatly increasing conduction speed. When the AP reaches the neuromuscular junction, it depolarizes the presynaptic terminal, opening voltage-gated Ca²⁺ channels. Ca²⁺ influx triggers acetylcholine (ACh) release, which binds nicotinic receptors on the skeletal muscle motor end plate. This opens ligand-gated Na⁺ channels, generating an end plate potential. If threshold is reached, a muscle fiber action potential is produced, spreading across the sarcolemma and into T-tubules to initiate excitation–contraction coupling.

Fun Summary – Action Potential → Muscle Activation

• ⚡ Neuron hits threshold → Na⁺ channels snap open → AP begins.

• 🌊 Propagation wave: Na⁺ opens the next set, K⁺ repolarizes after—perfect relay team.

• 🧈 Myelin = speed boost: AP leaps node to node like a rapid-fire teleport.

• 🎯 At the NMJ: AP arrives → Ca²⁺ channels open → ACh released.

• 🔑 ACh binds muscle receptors → Na⁺ rushes in → end-plate potential.

• 🔥 If strong enough → muscle AP is triggered → contraction machinery engaged.

6. Sequence of Reactions Leadinggq to Smooth Muscle Contraction After Gq-linked α-Adrenoceptor Activation

Activation of a Gq-linked α₁-adrenoceptor on smooth muscle begins when norepinephrine binds the receptor, causing G-protein activation. The Gq subunit stimulates phospholipase C (PLC), which cleaves PIP₂ into DAG and IP₃. IP₃ binds to IP₃ receptors on the sarcoplasmic reticulum, triggering Ca²⁺ release into the cytosol. Rising Ca²⁺ binds calmodulin, forming a Ca²⁺–calmodulin complex that activates myosin light-chain kinase (MLCK). MLCK phosphorylates the regulatory light chains of myosin, increasing its ATPase activity and enabling cross-bridge interaction with actin. Unlike skeletal muscle, smooth muscle contraction depends on myosin activation, not actin regulation. As long as Ca²⁺ and MLCK activity remain elevated, sustained contraction occurs. Relaxation occurs when Ca²⁺ is pumped out or sequestered and myosin light-chain phosphatase (MLCP) removes phosphate from myosin.

Fun Summary – Gq → PLC → IP₃ → Ca²⁺ → Contraction

• 📞 NE binds α₁ receptor → Gq wakes up.

• 🧪 Gq activates PLC → PIP₂ becomes DAG + IP₃ (the power duo).

• 🚪 IP₃ opens Ca²⁺ channels on the SR → Ca²⁺ floods the cell.

• 🧲 Ca²⁺ hooks up with calmodulin → activates MLCK.

• 🔧 MLCK “switches on” myosin via phosphorylation → actin–myosin interaction begins.

• 💪 Smooth muscle contracts—slow, strong, and energy-efficient.

• 📴 Relaxation: Ca²⁺ pumped away + MLCP dephosphorylates myosin.

7. Structure & Contractile Elements of Smooth Muscle + Example Organ & Stimuli

Smooth muscle cells are spindle-shaped, non-striated cells with a single central nucleus. Unlike skeletal muscle, they lack sarcomeres and instead contain a network of thin (actin) and thick (myosin) filaments anchored to dense bodies in the cytoplasm and dense plaques on the membrane. These structures act like “mini Z-discs,” enabling force transmission throughout the cell. Myosin is regulated by phosphorylation rather than troponin; smooth muscle contraction is controlled by Ca²⁺–calmodulin activation of MLCK.

Smooth muscle is found throughout the body, such as in the gastrointestinal tract, airways, and blood vessels. In a blood vessel, for example, smooth muscle helps regulate vascular tone and blood pressure. Its activity is controlled by numerous stimuli, including autonomic neurotransmitters (sympathetic/parasympathetic), hormones (e.g., angiotensin II), local metabolites, stretch, and intrinsic pacemaker activity.

Fun Summary – Smooth Muscle Essentials

• 🔍 Spindle-shaped cells, single nucleus, no stripes, lots of flexibility.

• 🧵 Actin + myosin anchored to dense bodies/plaques → pull from many directions.

• 🎛 Myosin-regulated, not actin-regulated—needs phosphorylation to activate.

• 🫀 In blood vessels: controls tone + blood pressure.

• 🎮 Stimuli include:

  • Autonomic nerves (ACh, NE)

  • Hormones (angiotensin II, oxytocin)

  • Stretch responses

  • Local chemical signals

  • Pacemaker cells in some organs

• 🐢 Slow but strong → perfect for long-term tension.

8. Basic Structure of a Motor Neuron and How Each Region Contributes to AP Generation/Conduction

A motor neuron consists of dendrites, a cell body (soma), an axon hillock, a long myelinated axon, and axon terminals. Dendrites receive synaptic inputs from other neurons and conduct graded potentials toward the soma. The soma integrates these signals and determines whether they reach threshold. The axon hillock is the trigger zone where action potentials are initiated because it contains a high density of voltage-gated Na⁺ channels. Once triggered, the action potential travels down the axon, with myelin sheaths formed by Schwann cells enabling saltatory conduction between nodes of Ranvier. This ensures rapid, efficient transmission to the axon terminals. At the terminals, the AP triggers Ca²⁺ influx and neurotransmitter (ACh) release, allowing the neuron to communicate with muscle fibers at the neuromuscular junction.

Fun Summary – Motor Neuron Regions & Their Jobs

• 🌲 Dendrites: receive signals → the neuron’s antenna network.

• 🧠 Soma: decision center → sums up excitatory + inhibitory inputs.

• 🎯 Axon hillock: high-voltage zone → AP birthplace when threshold is hit.

• 🚄 Axon: long-distance highway → myelin boosts speed with saltatory jumps.

• 🧈 Nodes of Ranvier: ion channel hubs → recharge stations for APs.

• 📦 Axon terminals: AP arrives → Ca²⁺ enters → neurotransmitter released.

• 🔗 Outcome: neuron talks to muscle → contraction begins.

Below are medium-sized paragraphs with expanded, detailed, fun bullet-style summaries for each topic—matching your previous format.

9. Extracellular Matrix (ECM): Definition, Cell Interaction & Functional Effects

The extracellular matrix (ECM) is a complex network of proteins, glycoproteins, and polysaccharides that surrounds cells and provides structural support, mechanical strength, and biochemical cues. Major components include collagen (tensile strength), elastin (elasticity), proteoglycans (hydration and compression resistance), and adhesive proteins like fibronectin and laminin. Cells attach to the ECM primarily through integrins, transmembrane receptors that connect extracellular molecules to the intracellular cytoskeleton. When integrins bind the ECM, they trigger intracellular signaling pathways that influence cell survival, gene expression, proliferation, and migration. These interactions can determine how cells differentiate, how tissues repair after injury, and how cancer cells invade new areas. For example, fibroblasts use ECM cues to guide wound healing, while muscle cells rely on ECM attachments to transmit contractile force.

Fun Summary – ECM & Cell Interaction

• 🌐 ECM = protein “scaffolding” around cells (collagen, elastin, proteoglycans).

• 🧲 Integrins = cell hooks that grab ECM and link it to the cytoskeleton.

• 🧬 ECM talks to cells: signals survival, division, or movement.

• 🛠 Wound healing: fibroblasts follow ECM “breadcrumbs” to repair tissue.

• 💪 Muscle fibers pull against ECM to transfer force to tendons.

• 🦠 Cancer cells misuse ECM signals to invade and spread.

10. Arrangement of Filaments in Skeletal Muscle & How Contraction Occurs

Skeletal muscle fibers are highly organized, containing repeating units called sarcomeres, which are bounded by Z-lines. Within each sarcomere, thin filaments (actin, along with troponin and tropomyosin) extend from the Z-line, while thick filaments (myosin) occupy the center. These filaments partially overlap, creating striations characteristic of skeletal muscle. During contraction, Ca²⁺ released from the sarcoplasmic reticulum binds troponin, causing tropomyosin to shift and expose actin’s myosin-binding sites. Myosin heads attach to actin and perform a power stroke fueled by ATP hydrolysis, pulling actin filaments toward the M-line. This shortens the sarcomere, and when repeated across millions of sarcomeres, the entire muscle fiber shortens. The coordinated sliding of actin past myosin—known as the sliding filament mechanism—is the basis of skeletal muscle contraction.

Fun Summary – Sarcomere Structure & Sliding Filament Mechanism

• 🧵 Actin = thin filament (attached to Z-lines).

• 🚀 Myosin = thick filament (centered at the M-line).

• 🎞 Sarcomere = repeating contractile unit → stripes/striations.

• 🔓 Ca²⁺ unlocks troponin → tropomyosin moves → actin exposed.

• 🦾 Myosin grabs actin → power stroke → sarcomere shortens.

• 🔁 ATP resets myosin → repeat cycle = muscle contraction.

11. Shape of a Nerve/Muscle Action Potential & Ion Permeability Changes

The action potential in a skeletal muscle or peripheral nerve cell has a characteristic shape consisting of a rapid depolarization, followed by repolarization, and sometimes a brief after-hyperpolarization. It begins with a small depolarization that reaches threshold, causing voltage-gated Na⁺ channels to open. Na⁺ rushes into the cell, producing the steep upstroke (rising phase) of the action potential. After a millisecond, Na⁺ channels inactivate while voltage-gated K⁺ channels open, allowing K⁺ to flow out and drive repolarization. This brings the membrane back toward resting potential, and K⁺ channels may remain open long enough to cause a slight hyperpolarization before returning to baseline. Action potentials are all-or-none events, rely on rapid changes in membrane permeability to Na⁺ and K⁺, and propagate without loss due to the sequential opening of voltage-gated channels along the membrane.

Fun Summary – Action Potential Shape & Ion Movements

• 🎚 Threshold hit → voltage-gated Na⁺ channels burst open.

• 📈 Depolarization spike: Na⁺ floods in → rapid upward phase.

• 🚫 Na⁺ inactivation stops further influx like a built-in safety switch.

• 📉 Repolarization: K⁺ channels open → K⁺ exits → voltage falls.

• ⬇ After-hyperpolarization: extra K⁺ leaving pushes voltage slightly below rest.

• 🔁 Return to RMP: K⁺ channels close → membrane stabilizes.

• 🔥 Result: fast, all-or-none signal → perfect for nerve and muscle communication.

📘 Condensed Exam Revision Sheet: Muscle Physiology, Cell Biology & Neurophysiology

1. Basic Components of a Human Cell

Key Structures & Functions

• Plasma membrane – selective barrier; regulates transport & communication.

• Cytoplasm – contains organelles and cytoskeleton for structure/transport.

• Nucleus – stores DNA; controls gene expression.

• Mitochondria – ATP synthesis.

• ER – RER: protein synthesis; SER: lipid synthesis + detox.

• Golgi – modifies/packages proteins.

• Lysosomes/Peroxisomes – waste breakdown.

2. Events at the Neuromuscular Junction → Muscle AP

• Motor neuron AP reaches terminal → Ca²⁺ entry → ACh release.

• ACh binds nicotinic receptors → Na⁺ entry → end-plate potential.

• If threshold: muscle AP spreads via sarcolemma & T-tubules.

• DHP (voltage sensor) activates RyR → Ca²⁺ release from SR → contraction.

3. Resting Membrane Potential (RMP)

• Set by Na⁺/K⁺ pump (3 Na⁺ out, 2 K⁺ in) + K⁺ leak channels.

• Inside negative (~ −70 mV).

• Used for communication:

  • Neurons depolarize → action potentials.

4. Plasma Membrane + Junctions

Membrane structure: phospholipid bilayer + proteins + cholesterol.
Tight junctions – barrier, prevent leakage.
Adherens junctions – link actin → structural stability.
Gap junctions – ion channels between cells → electrical coupling.

5. AP in Motor Neuron → AP in Muscle

• Inputs depolarize soma → axon hillock reaches threshold.

• Na⁺ channels open → AP propagates (saltatory conduction).

• Terminal depolarization → Ca²⁺ entry → ACh release.

• Muscle fiber receptors activate → muscle AP generated.

6. Smooth Muscle Contraction via Gq (α₁-Adrenoceptor)

• NE binds α₁ receptor → Gq → PLC activation.

• PIP₂ → IP₃ + DAG.

• IP₃ → Ca²⁺ release from SR.

• Ca²⁺–calmodulin → MLCK activation.

• MLCK phosphorylates myosin → cross-bridge cycling → contraction.

7. Structure & Contractile Elements of Smooth Muscle

• Spindle-shaped cells, no striations.

• Actin + myosin anchored to dense bodies/plaques.

• Myosin regulated by phosphorylation (MLCK).

• Example: blood vessels (control diameter).

• Controlled by: autonomic input, hormones, stretch, local signals.

8. Structure of a Motor Neuron

• Dendrites – receive input.

• Soma – integrates signals.

• Axon hillock – AP initiation site.

• Myelinated axon – rapid conduction.

• Terminals – neurotransmitter release (ACh).

9. Extracellular Matrix (ECM)

• Network of collagen, elastin, proteoglycans, fibronectin.

• Cells attach via integrins, linking ECM ↔ cytoskeleton.

• Controls: cell survival, migration, differentiation, wound healing.

10. Filament Arrangement in Skeletal Muscle

• Sarcomere: Z-line → M-line.

• Actin (thin) attached to Z-lines.

• Myosin (thick) in center.

• Ca²⁺ binds troponin → tropomyosin shifts → myosin binds actin.

• Sliding filament mechanism shortens sarcomere → contraction.

11. Action Potential Shape & Ion Permeability

Phases:

1. Depolarization – Na⁺ channels open → Na⁺ influx.

2. Repolarization – Na⁺ inactivation; K⁺ channels open → K⁺ efflux.

3. After-hyperpolarization – continued K⁺ outflow.

• AP = all-or-none, rapid, propagated without decay.

🔥 Ultra-Condensed One-Line Summaries (Exam Speed Round)

• Cell components: membrane controls entry; nucleus directs; mitochondria power.

• NMJ: motor AP → ACh release → muscle AP → Ca²⁺ → contraction.

• RMP: Na⁺/K⁺ pump + K⁺ leaks set negativity.

• Membrane/junctions: tight = barrier; adherens = strength; gap = communication.

• Neuron→muscle: Na⁺ AP travels, ACh released, muscle fires AP.

• Smooth muscle Gq: α₁ → Gq → PLC → IP₃ → Ca²⁺ → MLCK → contraction.

• Smooth muscle structure: dense bodies, slow sustained force; controlled by many stimuli.

• Motor neuron layout: dendrites receive, hillock fires, axon conducts, terminals release.

• ECM: structural net + signaling platform.

• Sarcomeres: actin + myosin sliding.

• AP shape: Na⁺ in → K⁺ out → spike and recovery.

Below are small–medium paragraphs for each topic, followed by fun, detailed bullet-style summaries to help with fast revision.

1. Main Constituents of Blood (Cells & Plasma)

Blood is a specialized connective tissue composed of cells suspended in plasma. The cellular portion includes red blood cells (erythrocytes), which transport oxygen and carbon dioxide; white blood cells (leukocytes), which provide immune defense; and platelets, which are essential for clotting. Plasma, the fluid matrix of blood, is mostly water (≈90%) and contains proteins such as albumin, fibrinogen, and immunoglobulins. It also carries electrolytes, nutrients, hormones, metabolic waste, and dissolved gases. Together, these components allow blood to transport materials, regulate homeostasis, and defend the body against pathogens.

Fun Summary – What’s in Blood?

• ❤ RBCs: oxygen taxis; carry O₂/CO₂.

• 🛡 WBCs: bodyguard squad; fight infections.

• 🩸 Platelets: tiny repair workers; patch leaks.

• 💧 Plasma = watery highway for proteins, nutrients, hormones, waste, electrolytes.

• 🚚 Whole blood = transport + regulation + defense in one flowing package.

2. Main Functions of Blood (Immune Defense & Transport)

Blood performs essential functions that keep the body alive and responsive. It provides immune defense by circulating leukocytes and antibodies that identify, neutralize, and eliminate pathogens. As a transport medium, blood delivers oxygen from the lungs and CO₂ back for exhalation. It carries nutrients from digestion to tissues, and removes metabolic wastes to the kidneys and liver. Blood also distributes hormones, allowing distant organs to communicate, and transports cells, such as basophils and other leukocytes, to sites where they are needed.

Fun Summary – What Blood Does All Day

• 🦠 Immune defense: patrols for invaders; sends WBC reinforcements.

• 🍎 Nutrients delivered → tissues stay energized.

• 🗑 Waste removed → kidneys/liver clean up.

• 💨 Gas exchange: O₂ in, CO₂ out.

• 📬 Hormone delivery service: long-distance chemical messaging.

• 🚑 Cell transport: moves immune cells (e.g., basophils) to battle zones.

3. White Blood Cells: Basophils, Neutrophils, Lymphocytes, Monocytes

Basophils are large-granule leukocytes (14–16 μm) involved in inflammatory and allergic responses. They release histamine and other mediators that enhance inflammation and amplify allergic reactions, with lifespans lasting months. Neutrophils, though mentioned briefly, are the frontline defenders that phagocytose microbes using specialized granules. Lymphocytes come in small and large forms, serving as the central cells of adaptive immunity, capable of long-term memory and rapid responses upon future exposures. Monocytes circulate briefly before entering tissues to become macrophages, where they phagocytose debris and present antigens to activate adaptive immunity.

Fun Summary – WBC All-Stars

• 🟪 Basophils:

  • Big granules, big drama → histamine release.

  • Masters of allergies & inflammation.

  • Long-lived trouble amplifiers.

• ⚔ Neutrophils:

  • First on the battlefield → eat microbes.

  • Loaded with microbe-killing granules.

• 🧠 Lymphocytes:

  • Adaptive immunity → B cells, T cells, NK cells.

  • Long lifespan; learn, remember, and attack specifically.

• 🧹 Monocytes/Macrophages:

  • Clean-up crew + antigen presenters.

  • Bridge innate → adaptive immunity.

4. Platelets (Thrombocytes) & Haemostasis

Platelets are small (2–4 μm) cytoplasmic fragments derived from megakaryocytes in the bone marrow. They circulate in high numbers and contain granules with clotting factors and repair molecules. Their primary role is haemostasis, the process that prevents blood loss after injury. Haemostasis begins with vasoconstriction, reducing blood flow. Platelets then adhere and activate, forming a temporary platelet plug. This triggers the coagulation cascade, leading to fibrin formation. Fibrin forms a stable network that traps erythrocytes and solidifies the clot, ensuring the vessel is sealed until tissue repair is complete.

Fun Summary – Platelets & Clotting

• 🟡 Tiny but mighty: fragments with powerful granules.

• 🔒 Step 1 – Vasoconstriction: “Tighten the pipes!”

• 🩹 Step 2 – Platelet plug: stick, activate, recruit friends.

• 🕸 Step 3 – Coagulation: fibrin web traps RBCs → strong clot.

• 🧱 Goal: stop bleeding, protect tissue, start repair.

5. Plasma: Function & Role

Plasma is the liquid matrix of blood and forms the majority of its volume. Composed mainly of water, it contains proteins such as albumin (osmotic balance), fibrinogen (clotting), and antibodies (immune defense). Plasma transports nutrients, hormones, metabolic waste, electrolytes, and even circulating cells. It serves as the connective medium that allows materials to move throughout the body efficiently, supporting homeostasis and enabling communication between distant organs.

Fun Summary – Plasma Power

• 🌊 Water highway: carries everything needed for life.

• 🧪 Protein-packed: albumin, antibodies, clotting factors.

• 🚚 Transport vehicle: nutrients, hormones, drugs, wastes.

• ⚡ Maintains balance: fluid, electrolytes, pH.

• 🚑 Carries cells: WBCs, RBCs, platelets all surf in plasma.