ENDOCRINE SYSTEM. Endocrine - General Major Control System of Homeostasis Negative Feedback Ductless...
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Transcript of ENDOCRINE SYSTEM. Endocrine - General Major Control System of Homeostasis Negative Feedback Ductless...
ENDOCRINE SYSTEM
Endocrine - General
Major Control System of HomeostasisNegative FeedbackDuctless Glands; Produce HormonesDiffuse into BloodSlow Initial Effects, but Effects Persist
much longerHormones act on specific Targets
Classification of Glands
Endocrine – ductless glands that secrete hormones into the blood stream
Exocrine – ducted glands that secrete their products onto a surface
Hormones – Definition
Definitions- Literal: To spur on, to set in motion- Physiological: A chemical
messenger that affects another tissue or organ (the target)
Hormones - General Function
Modify activity of target cells
Targets have specific receptors for the particular hormone
Distributed by blood
Location of Receptors
Cell Surface
- cell membraneIntracellular
- Cytoplasm
- Nucleus
Mechanisms of Hormone Action
Steroids (Synthesized from Cholesterol)- Hormone enters cell- Hormone forms complex with receptor- Hormone/receptor complex enters nucleus- Complex binds to DNA- Protein synthesis occurs- Protein alters cell function (i.e. produces the
effect)- E.g. Testosterone
Mechanisms of Hormone Action continued
Non-Steroids (Proteins/Peptides/Amine) Hormones- Hormone does not enter cell- Hormone is 1st messenger- Hormone binds to receptor on cell
membrane- Triggers formation of 2nd messenger (cyclic
AMP)- 2nd messenger alters cellular activities (i.e.
produce the effect)- E.g. Pituitary hormones
Regulation by Receptors
Changeable Number of receptors on target- Up Regulation
* Low hormone levels* Number of receptors increases* Target’s responsiveness increases
- Down Regulation* Excess hormone levels* Number of receptors decreases* Target’s responsiveness decreases
Secretion Stimuli
Hormonal- Tropic hormones regulate activity of
other endocrine glands - Most common
Humoral- Changing levels of ion or nutrients
trigger release of hormonesNeural
- Stimulated by nerve fibers
Hormonal Stimuli Hormonal Stimuli of Endocrine of Endocrine GlandsGlands
Slide 9.11Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Endocrine glands are activated by other hormones
Figure 9.2a
Humoral Stimuli of Humoral Stimuli of Endocrine GlandsEndocrine Glands
Slide 9.12Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 9.2b
Changing blood levels of certain ions or nutrients stimulate hormone release
Neural Stimuli of Neural Stimuli of Endocrine GlandsEndocrine Glands
Slide 9.13Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Nerve impulses stimulate hormone release
Most are under control of the sympathetic nervous system
Figure 9.2c
Endocrine Organs
HypothalamusPituitary
- Anterior
- PosteriorThyroid GlandParathyroid
Glands
Adrenal Glands
- Cortex
- MedullaPancreasPineal GlandThymusGonads
Hypothalamus
Integrates Nervous System & EndocrinePortal Circulation carries hormones to
Anterior PituitaryReleasing Factors (hormones) stimulate
secretion by Anterior PituitaryInhibiting Factors (hormones) are
antagonistic to ReleasingNervous tissue carries hormones to
Posterior Pituitary
Pituitary Gland
Attached to Hypothalamus via infundibulum
Protected by sella turcica of sphenoidDivided into 2 lobes:
- Anterior (glandular)
- Posterior (neuroendocrine)
Anterior Pituitary (Adenohypophysis)
“Master Gland” (makes & secretes various tropic hormones)
Tropic Hormones- Act on other Endocrine Glands- Serve as Hormonal Stimuli- Stimulate release of another hormone
Anterior Pituitary (Adenohypophysis)
- Human Growth Hormone (GH):
*Target: All/Most Body Cells (esp. Bone & Muscle)
*Action: Promotes Growth & Repair,
*Increases Blood Glucose
- Prolactin (PRL):
*Target: Mammary Tissue*Action: Promotes milk secretion
Anterior Pituitary continued
Thyroid Stimulating Hormone (TSH)
- Target: Thyroid Gland
- Action: Stimulates production of Thyroxine
Anterior Pituitary continued
Adrenocorticotropic Hormones (ACTH)- Target: Adrenal Cortex- Action: Controls production/secretion adrenal
cortex hormonesGonadotropic Hormones
- Follicle Stimulating Hormone (FSH)* Target: Gonads (Ovaries/Testes)* Action: Production of gametes & sex
hormones
Anterior Pituitary continued
- Luteinizing Hormone (LH/ICSH)
*Target: Gonads
*Functions: Production of sex hormonesPrepare uterus for implantationDevelop corpus luteum
Hormones of the Anterior PituitaryHormones of the Anterior Pituitary
Slide 9.17Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 9.4
Posterior Pituitary (Neurohypophysis)
Does NOT synthesize HormonesNeural rather than glandularStores & Releases two hormones produced
by hypothalamus
- Oxytocin
*Target: Uterus & Mammary Glands
*Action: Stimulates Contractions to eject fetus & milk
Posterior Pituitary continued
- Antidiuretic Hormone (ADH) also called vasopressin
*Target: Kidneys
*Action: Conserve Water (decrease urine
volume)Increase BP
Hormones of the Posterior PituitaryHormones of the Posterior Pituitary
Slide 9.22b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 9.5
Thyroid Gland
Thyroid Hormone- T3 (Triiodothyronine), T4 (Thyroxine)- Target: Most body cells- Action: Increase metabolic rate, regulate
body temperatureCalcitonin
- Target: Bone/Osteoclast Inhibition- Action: Decrease blood Ca2+
(Hypocalcemia if excessive)
Parathyroid Glands
Parathyroid Hormone
- Target: Bone/Stimulation of Osteoclasts
- Action: Increase blood Ca2+
(Hypercalcemia if excessive)
Parathyroid GlandsParathyroid GlandsSlide 9.26
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Tiny masses on the posterior of the thyroid
Secrete parathyroid hormone (PTH)
Adrenal Glands
Adrenal Cortex (outer/glandular)- Cortisol
* Target: Many tissues* Action: make glucose, decrease
inflammation- Aldosterone
* Target: Kidneys* Action: Maintain Na+/K+ blood levels
Adrenal Glands continued
Adrenal Medulla (inner/nervous)
- Epinephrine/Adrenalin (Fear/Flight)
- Norepinephrine/Noradrenalin (Anger/Fight)
- Targets:Heart, Liver, Muscles, Blood Vessels, etc.
- Functions: Prepare for sudden threat
Pancreas
Endocrine (Islets of Langerhans) & Exocrine
Glucagon (from Alpha Cells)- Target: Liver- Action: Release glucose from glycogen
(increases blood glucose)Insulin (from Beta Cells)
- Target: Most/All Cells- Action: Promotes glucose transport into
cells (decreases blood glucose)
Pineal & Thymus Glands
Pineal Gland (Endocrine & CNS)- Melatonin
* Target: Hypothalamus* Action: Sets Diurnal Clock/Circadian rhythm
& promotes sleepThymus (atrophies at puberty)
- Thymosins* Target: T cells of immune system* Action: T cell maturation
(immunocompetence)
Gonads
Ovaries- Estrogen
* Target: Uterus, Ovaries, other* Action: prepare for fetus, secondary sexual
characteristics - Progesterone
* Target: Uterus* Action: maintains pregnancy, prevents
uterine contractions
Gonads continued
Testes
- Testosterone
*Target: Various body parts
*Action: Secondary sexual characteristics