Hormone Regulation - Physiology Flashcards
Hormone Stimulation - Function
Influences the activity of only certain tissue cells: target cell. Increase or decrease normal cellular processes.
What changes do hormonal stimulus typically produce?
- Alters plasma membrane permeability or membrane potential, or both, by opening or closing ion channels.
- Stimulates synthesis of proteins or enzymes.
- Activates or deactivates enzymes.
- Induces secretory activity.
- Stimulates mitosis.
Mechanisms of Hormone Action - Activation of Protein Kinases
- Hormone binds receptor
- Receptor activates G protein
- Active: GTP
- Inactive: GDP - G protein activates adenylate cyclase
- Adenylate cyclase converts ATP to cyclic AMP
- Cyclic AMP activates protein kinase
- Permit responses of target cells.
Mechanisms of Hormone Action - Protein Synthesis
- Hormone binds to intracellular receptor
- Binded receptor-hormone complex
- Hormone receptor binds to DNA
- Transcription of DNA to produce messenger RNA
- mRNA translated on the cytoplasmic ribosomes to produce specific protein molecules
Control of Hormone Release - Humoral Stimulus
Direct response to changing blood levels of certain critical ions and nutrients.
Target cell activated.
Simplest.
F. ex. insulin from pancreas
Control of Hormone Release - Neural Stimulus
Nerve fibers stimulate hormone release.
F. ex. sympathetic nervous system stimulates adrenal gland to release epinephrine during stress.
Control of Hormone Release - Hormonal Stimulus
Release of hormones in response to hormones produced by other endocrine hormones.
Most complicated. Majority of glands work this way.
Cyclic pathway: not working all the time - menstrual cycle, melatonin at night.
Pineal Gland (Epithalamus)
Major secretory product: melatonin, derived from serotonin.
Peak levels at night, make us drowsy. Lowest levels at noon.
Visual input (day vs night) Retina → pineal gland
Anterior Pituitary Gland and Hypothalamus
Indirect control through release of regulatory hormones. Hormones produced by anterior pituitary: - Growth hormone (GH) - Thyroid-stimulating hormone (TSH) - Adrenocorticotropic hormone (ACTH) - Follicle-stimulating hormone (FSH) - Luteinizing hormone (LH) - Prolactin and beta endorphin
Growth Hormone (Somatotropin)
Promotes protein synthesis and tissue building through direct and indirect mechanisms.
Levels controlled by:
- GHRH: growth hormone releasing hormone
- GHIH: growth hormone inhibiting hormone
Growth Hormone - Glucose Sparing Effect
Switch from glucose to fatty acids - Lypolysis
Growth Hormone - Diabetogenic Effect
Liver stimulation to break down glycogen to glucose, which is then deposited into the blood.
Indirect secondary mechanism: produce IGFs(insulin like growth factors), further stimulating growth effect (bones,muscle,nervous s, immune s)
Thyroid Stimulating Hormone (Thyrotropin)
Stimulates normal development and secretory activity of thyroid gland.
Triggered by thyrotropin-releasing hormone (TRH) from hypothalamus.
Negative feedback.
Adrenocorticotropic Hormone (Corticotropin)
Control stress levels.
Secreted by corticotrophs.
Corticotropin-releasing hormone.
Controls waking up, peak levels in the morning, shortly before awakening.
Gonadotropin - Follicle-Stimulating Hormone
Regulate function of gonads (testes and ovaries) prompted by gonadotropin-releasing hormone (GnRH) in hypothalamus. Stimulates gamete (sperm or egg) production.
Gonadotropin - Luteinizing Hormone
Regulate function of gonads (testes and ovaries) prompted by gonadotropin-releasing hormone (GnRH)
in hypothalamus.
Production of gonadal hormones:
- Triggers ovulation and synthesis and release of ovarian hormones.
- Stimulates production of testosterone.
Prolactin
Produced by lactotrophs. Stimulates milk production.
Primarily controlled by prolactin-inhibiting hormone (dopamine).
Estrogen stimulates prolactin release.
Infant’s suckling stimulates release of prolactin-releasing factor.
Posterior Pituitary Gland and Hypothalamus
No production of hormones, storage and secretion of hormones produced by hypothalamus.
Paraventricular nuclei: Production of oxytocin
Supraoptic nuclei: Production of ADH
Oxytocin and ADH almost identical .