ZA

Lecture Review Flashcards

Cell Communication Pathways

  • After passing through pathways, signals reach targets, leading to a response.

  • Protein channels connect cells; there are approximately 20 different types.

Cell Adhesion Molecules (CAMs)

  • Gap junctions are present in almost all cell types.

  • Cell adhesion molecules (CAMs) act as receptors for cell-to-cell signaling, with specific matching shapes.

Localized Communication

  • Two types:

    • Autocrine: signals affect the cell that produces them.

Inflammation

  • Allergic reactions (e.g., hives) are examples of advanced inflammation.

  • Mast cells function in tissues, and loss of function can occur due to damage (e.g., a cut).

Long Distance Communication

  • Involves endocrine and neurohormones.

Endocrine

  • Hormones are released from endocrine cells and travel through the bloodstream.

  • Receptor blockers can inhibit reactions by preventing signal binding, easier than removing the initial signal.

Nervous System and Endocrine

  • Use a combination of chemical and electrical signaling.

  • Hormones are chemical signals transported in the blood throughout the body.

  • The nervous system is rapid and specific, while the endocrine system takes longer but effects last longer.

  • Proteins are harder to break down compared to neurotransmitters like acetylcholine, which are broken down by enzymes.

Neurocrines

  • Include neurotransmitters, neuromodulators (autocrine or paracrine), and neurohormones.

Neurotransmitters

  • Signals travel through, reaching target cells to elicit a response.

Neurohormones

  • Chemical messengers with deeper, more specific functions.

Cytokines

  • Diverse types like interferons and interleukins, producing a wide range of responses.

Erythropoietin (EPO)

  • A hormone that also acts as a cytokine, triggering red cell production.

Receptors

  • Cells respond to signals only if they have the appropriate receptor.

  • Receptors can be blocked to control or prevent responses.

  • Most are proteins.

  • Binding can occur on the cell surface or inside the cell.

  • Lipophilic molecules can pass through the phospholipid membrane, binding to intracellular receptors.

  • Lipophobic molecules bind to surface receptors.

  • Intracellular binding leads to slower responses (hours), especially if it involves the nucleus.

Clinical Example: Diabetes

  • A patient with uncontrolled diabetes had a glucose level greater than 900 on a glucometer.

  • Treatment involved an insulin drip, taking a while to stabilize glucose levels.

Lipophobic Signals

  • Example: ferritin.

  • Bind to receptors on the cell membrane surface because they cannot diffuse through it.

  • This process triggers a receptor, leading to a faster intracellular response.

Types of Receptors

  • Receptor channel

  • Receptor enzyme

  • G proteins

  • Intracellular receptors

Receptor Channels

  • Ligand binding changes the protein's conformation, opening a gate for molecule movement.

G Proteins

  • Linked to a cytoplasmic tail that connects the receptor.

Integrin Receptors

  • Attach to the cytoskeleton, causing changes inside the cell.

Signal Transduction Pathways

  • Use a key to pass signals through the membrane.

  • Phosphorylation (adding a phosphate group) triggers enzymes.

  • Responses include:

    • Muscle contraction

    • Control of gene activity and protein synthesis

    • Effects on transport

    • Effects on proteins

Secondary Messengers

  • Examples include cyclic AMP.

G Coupled Proteins

  • A large group with hundreds of different types of protein receptors or G proteins.

  • Ligands that bind include hormones and growth factors.

Ligand Gated Ion Channels

  • Neurotransmitters are a good example.

  • Trigger the initial response.

Calcium

  • Acts as a secondary messenger.

  • Can alter enzymes and affect potassium channels.

Nitric Oxide

  • Small amounts can help smooth muscle and cause vasodilation, lowering blood pressure.

  • Large amounts can be damaging.

Hydrogen Sulfide

  • Can trigger cardiovascular benefits.

  • Found in garlic, which can vasodilate blood vessels.

Eicosanoids

  • Resemble prostaglandins.

  • Affect sleep and modulate pathways.

Receptor Subtypes

  • Examples:

    • alpha one

    • alpha two

  • Drugs can be used to block specific receptors.

  • Competing agonists turn something on, while antagonists block receptors.

  • Birth control pills use these mechanisms.

Modulation of Pathways

  • Down regulation: Decreasing the number of receptors (exocytosis).

  • Desensitization: Changes in receptor response (drug tolerance).

  • Upregulation: Adding more receptors (exocytosis).

Termination of Signals

  • Breaking down neurotransmitters using enzymes (e.g., acetylcholinesterase for acetylcholine).

Clinical Example: Diabetes Insipidus

  • Patients lack receptors to pull water back in, leading to dehydration and excessive thirst/urination (PUPD).

Hormone Examples

  • Parathyroid hormone: Can lead to too much calcium.

Rhodopsin

  • A protein in rods (eye cells) that helps us see in low light.

Toxins

  • Bordetella pertussis (whooping cough) can also affect.

Epinephrine

  • Breaks down glycogen to increase blood sugar.

Signal Effects

  • Can vary based on the receptor; epinephrine can vasodilate depending on the receptor.

Specialized Senses

  • Vision, hearing, taste, and smell.

Vision

  • Light triggers photoreceptors, depolarizing tissue and sending a signal to the optic nerve.

Hearing

  • Sound vibrates fluid, signaling hair cells and sending a signal to the temporal lobe.

Taste

  • Relies on cranial nerves and different receptors (thermoreceptors, chemoreceptors, osmoreceptors).

  • 80% of taste is smell; loss of smell affects taste.

Reflex Arcs

  • Neuro and endocrine control.

  • The nervous system is rapid, while the endocrine system is slower.

Excitable Tissues

  • Muscles and nervous tissue can conduct electrical currents.

Nerve Cells

  • Neurons transmit signals to other neurons, muscles, or glands.

  • Myelin sheath is made by Schwann cells (neuroglia).

Neural Pathways

  • Pathway: input, integration, output.

Membrane Potential

  • Influenced by the gradient of ions and membrane permeability.

  • To depolarize tissue, a stimulus is required.

Action Potentials

  • Occur when a stimulus depolarizes the membrane to threshold.

Graded Potentials

  • Not as strong as action potentials but can be added together.

  • If enough stimuli are received, the axon hillock can trigger an action potential.

  • Graded Potentials and Action potentials