The Endocrine System-Lecture 6 Exam 2 Flashcards
List the Criteria That Make a Chemical Signal a Hormone
– Chemical messengers secreted by a cell, group of cells, or glands
– Secreted into the blood
– Transported to a distant target
– Exert their effects at very low concentrations
– Act by binding to receptors
Explain the Ways the Action of a Hormone Can be Terminated /Inactivated
–Limiting hormone secretion
-Circulating hormones in the blood are degraded/broken down by enzymes
* Rate of hormone breakdown = half-life
-Hormones bound to receptors are engulfed by endocytosis and then degraded by enzymes
Characteristics of Steroid Hormones
-Made by modifying cholesterol
-Lipophilic
-Most activate DNA to enable protein synthesis
-Long half-life
Examples of Steroid Hormones
Cortisol, Estrogen, & Testosterone
Characteristics of Peptide Hormones
-Most common type of hormone
-3 or more amino acids
-Made in advance & stored in vesicles
-Water-soluble
-Lipophobic
-Short Half-Life
Examples of Peptide Hormones
-Pituitary Hormones
-Parathyroid Hormones
-Pancreas Hormones
Characteristics of Amine/Amino Acid-Derived Hormones
-Derived from a single amino acid
-Mostly derived from Tryptophan (amino acid) & Tyrosine (amino acid)
Examples of Amine/Amino Acid-Derived Hormones
-Melatonin (pineal gland)
-Thyroid Hormones (T3 & T4), lipophobic
-Catecholamines (NE, E), lipophobic
How are Steroid Hormones Synthesized, Stored, Released from Endocrine Cells, & Transported in the Blood?
-Synthesized: From cholesterol obtained from food sources or produced internally by the body’s own cells
-Stored: Not stored
-Released from Endocrine Cells: When a stimulus activates the endocrine cell, precursors in the cytoplasm are actively converted to active hormone. The hormone concentration in the cytoplasm rises, and the hormones move out of the cell by simple diffusion
-Transported in the Blood: By being bound to carrier proteins
How are Peptide Hormones Synthesized, Stored, Released from Endocrine Cells, & Transported in the Blood?
-Synthesized: By ribosomes as large
inactive preprohormones
-Stored: Vesicles store peptide prohormones until the cell receives a
signal for secretion
-Released from Endocrine Cells: Vesicles release hormones by exocytosis
-Transported in the Blood: Soluble in plasma, allowing them to circulate freely in the blood without the need for transport proteins
Locations of Target Cell Receptors for Steroid Hormones
Nucleus, Cytosol, & Plasma Membrane
Locations of Target Cell Receptors for Peptide Hormones
Cytoplasm or Nucleus
Simple Endocrine Pathway for Hormone Release & the Role of Negative Feedback in this Pathway
-Endocrine cell acts as both sensor and integrating center
-Endocrine cell directly senses a stimulus and responds by secreting its hormone
-Hormone then leads to a response
-Negative feedback maintains a stable hormone level in the body
Complex Endocrine Pathway vs. Simple Endocrine Pathway
-Complex Endocrine Pathways has multiple hormones that work together to control it
-Simple Endocrine Pathways is controlled by one hormone
