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HOMEOSTASIS & TRANSPORT

1) Homeostasis

  • a. Define the term homeostasis.
    Homeostasis is your body’s way of keeping things stable inside (like temperature or pH), even when the outside changes.

  • b. Why is homeostasis important?
    It keeps your body working properly. Without it, things can go too far out of balance and make you sick.

  • c. Understand homeostatic reflex: set point, integrating/control center, afferent/efferent signals and effectors.

    • Set point: Normal target (like 98.6°F for body temp).

    • Control Center: Usually brain or spinal cord — decides what action to take.

    • Afferent signal: Info going to control center.

    • Efferent signal: Commands going from control center to the body.

    • Effectors: Muscles or glands that make the change (e.g., sweat glands).

  • d. What is positive and negative feedback? Know specific examples.

    • Negative feedback: Reverses change (e.g., sweating to cool down when hot).

    • Positive feedback: Increases the change (e.g., contractions in childbirth or blood clotting).

    • Difference: Negative stabilizes; positive amplifies.

2) Transport

  • a. Define and differentiate between passive and active mechanisms of transport.

    • Passive: No energy used, moves from high to low concentration (e.g., diffusion).

    • Active: Uses energy (ATP), moves from low to high (against the gradient).

  • b. Describe what drives the direction of simple diffusion.
    The difference in concentration — molecules move from high to low concentration.

  • c. What factors influence the rate of diffusion?
    Bigger gradient, higher temperature, smaller size, and more surface area all make diffusion faster.

  • d. How does active transport differ from passive? What are the 2 types of active transport? Bulk transport?

    • Active: Uses energy; moves things against the gradient.

    • Primary active: Direct use of ATP.

    • Secondary active: Uses the energy from another gradient.

    • Bulk transport: Moves large stuff in or out of the cell (endocytosis, exocytosis).

  • e. Define endocytosis and exocytosis. Know examples of each type of transport.

    • Endocytosis: Cell takes in material (e.g., white blood cell eating bacteria).

    • Exocytosis: Cell releases material (e.g., neuron releasing neurotransmitters).

3) Osmosis

  • a. Define the terms osmosis and osmolarity.

    • Osmosis: Water moving through a membrane from less salty to more salty area.

    • Osmolarity: Total amount of solutes in a solution.

  • b. Know how to calculate osmolarity of a solution.
    Multiply molarity × number of particles (e.g., 1M NaCl = 2 Osm because Na+ and Cl- split).

  • c. How do you determine tonicity (hypertonic, isotonic, hypotonic) and the role of non-penetrating solute?

    • Tonicity depends on non-penetrating solutes.

    • Hypertonic: More solutes outside → water leaves cell.

    • Hypotonic: More solutes inside → water enters cell.

    • Isotonic: Equal solutes → no water movement.
      Non-penetrating solutes (like Na+) stay outside and draw water.

  • d. What happens to a cell in hypertonic, isotonic, and hypotonic solutions?

    • Hypertonic: Cell shrinks.

    • Isotonic: No change.

    • Hypotonic: Cell swells or bursts.

NEURON, ACTION POTENTIAL, NEUROTRANSMITTERS

1) Neuronal Communication

  • a. Explain how dendrites, axons, axon terminals, Nodes of Ranvier are involved in communication.

    • Dendrites receive signals.

    • Axon sends signal.

    • Nodes of Ranvier help signal move faster.

    • Axon terminals release neurotransmitters.

  • b. Define synapse, synaptic cleft, presynaptic cell, postsynaptic cell, and neurotransmitter.

    • Synapse: The space between neurons.

    • Synaptic cleft: The actual gap.

    • Presynaptic cell: Sends the message.

    • Postsynaptic cell: Receives the message.

    • Neurotransmitter: Chemical that sends the signal across.

2) Resting Membrane Potential

  • a. Define resting membrane potential and its typical value.
    About -70 mV. It's the “charged” state when the neuron is ready to fire.

  • b. What creates this resting potential?
    Unequal distribution of ions (more Na+ outside, more K+ inside) and the Na+/K+ pump.

  • c. Which ions are greater outside and inside the cell?

    • Na+ greater outside.

    • K+ greater inside.

  • d. Why is the Na+/K+ pump important?
    It maintains the ion balance and resting potential by pushing Na+ out and K+ in (3 Na+ out, 2 K+ in).

  • e. Define depolarization, repolarization, and hyperpolarization. What happens with ions?

    • Depolarization: Na+ enters → inside becomes positive.

    • Repolarization: K+ leaves → inside becomes negative again.

    • Hyperpolarization: Extra K+ leaves → cell becomes more negative than usual.

3) Action Potential

  • a. Differentiate between an action potential and a graded potential.

    • Action potential: All-or-nothing.

    • Graded potential: Small and varies in size.

  • b. Events in action potential:

    • Starts with a ligand-gated channel opening from a signal.

    • If threshold reached, voltage-gated Na+ channels open → Na+ in → depolarization.

    • Na+ channels close; K+ channels open → K+ out → repolarization.

4) Propagation of AP

  • a. What is myelination and how does it affect conduction?
    Myelin is a fat layer that insulates axons, speeding up signals.

  • b. Saltatory vs. non-saltatory conduction?

    • Saltatory: Jumps from node to node (faster).

    • Non-saltatory: Moves step-by-step (slower).

  • c. Which nerve types are fastest: A, B, or C?

    • A fibers are fastest (large and myelinated).

    • Then B, then C (small, unmyelinated).

5) Presynaptic Events

  • a. What triggers a neurotransmitter to be released?
    Action potential reaches end → voltage-gated Ca++ channels open → Ca++ enters → triggers release.

  • b. How is calcium involved?
    Ca++ causes vesicles holding neurotransmitters to fuse with the membrane and release them.

6) Postsynaptic Events

  • a. What is a ligand-gated channel and where is it?
    A channel that opens when a neurotransmitter binds. Found on the postsynaptic membrane.

  • b. What happens after NT binds to it?
    The channel opens → ions move → signal continues or is blocked.

  • c. Excitatory vs. Inhibitory response?

    • Excitatory: Na+ enters → more likely to fire.

    • Inhibitory: Cl- enters or K+ leaves → less likely to fire.

  • d. Define EPSP and IPSP.

    • EPSP: Excitatory postsynaptic potential (pushes toward action potential).

    • IPSP: Inhibitory postsynaptic potential (pushes away from action potential).

NEUROTRANSMITTERS

  • 1) Define agonist, antagonist, reuptake inhibitor, enzyme inhibitor.

    • Agonist: Activates receptor.

    • Antagonist: Blocks receptor.

    • Reuptake inhibitor: Stops recycling of NT.

    • Enzyme inhibitor: Stops NT from being broken down.

  • 2) What receptors does ACh bind to?

    • Nicotinic (excitatory).

    • Muscarinic (can be excitatory or inhibitory depending on organ).

  • 3) Nicotinic vs. Muscarinic receptors?

    • Nicotinic: Found in skeletal muscle; always excitatory.

    • Muscarinic: Found in heart/smooth muscle; variable effect.

  • 4) Describe adrenergic receptors.

    • Binds epinephrine/norepinephrine.

    • Alpha receptors: Constrict blood vessels.

    • Beta receptors: Affect heart/lungs (increase HR or relax bronchi).

  • 5) Role of major neurotransmitters:

    • Serotonin: Mood, sleep.

    • Dopamine: Reward, movement.

    • Glutamate: Excitatory.

    • GABA: Inhibitory.

    • Substance P: Pain.

    • Endorphins: Natural painkiller.

  • 6) NTs in disease:

    • Alzheimer’s: ↓ ACh.

    • Parkinson’s: ↓ Dopamine.

    • Runner’s high: ↑ Endorphins.

    • Cobra venom: Blocks ACh.

    • High BP: Too much norepinephrine.

  • 7) NTs in depression treatment?
    Serotonin, dopamine, norepinephrine.

  • 8) Excitatory vs Inhibitory NTs?

    • Excitatory: Glutamate, ACh (nicotinic), dopamine (some).

    • Inhibitory: GABA, glycine, ACh (some muscarinic).