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