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Lectures 22 & 23: Signaling within Organisms I: Chemical Signals (Six…
Lectures 22 & 23: Signaling within Organisms I: Chemical Signals
Steps toward multicellularity
Intercellular Communication within Cluster
Specialization of some cells within cluster
Aggregation of Cells into Clusters
Organization of specialized cells into groups (Tissues)
Types of Chemical Signaling
Paracrine Signals bind to receptors on nearby cells
Autocrine signals bind to receptors on same cell that secretes them
Juxtacrine Signaling: binds to adjacent cells
Animal Hormone Terminology
Target Cells: Have receptors for chemical signals
Endocrine Cells: Secrete chemical signals
Endocrine Glands: Secretory Organs composed of aggregations in endocrine cells
Exocrine Glands: Have ducts that carry their products to the outside of the body
Six events in hormone signaling
Transport of Hormone to target cells
Reception of hormone when hormone binds to receptor
Storage & Secretion of hormone
Relay & Amplification of signal via signal transduction
Biosynthesis of hormone
Cellular response
One hormone can elicit different responses in different target cells
Blood Glucose Level Control
Insulin: increases uptake of glucose into cells
Glucagon: Stimulates liver to break down glycogen into glucose
Pituitary Gland, attached to hypothalamus, connects nervous & endocrine systems
Posterior Pituitary releases neurohormones (Oxytocin & ADH)
Anterior Pituitary is controlled by hypothalamus
Plant Hormones
Cytokinins
Gibberellins
trigger a cascade of events leading to mobilization of reserves in geminating seeds
Auxin
Differential Growth- responses to light & gravity
Induces loosening of the cell wall by activating a proton pump that reduces pH in the cell wall.
Brassinosteroids
Ethylene
Involved in response to mechanical stress; fruit ripening
Abscisic Acid