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Endocrine System
- Major Control System
- Ductless glands; produce hormones
- Diffuse into blood
- Slow initial effects, but long persist much longer
- Hormones act on specific targets
- Regulated by negative feedback
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Endocrine system VS Nervous system
- Endocrine:
- Hormones
- Targets cells with receptors
- Changes metabolic activity
- Slower onset
- Widespread effects
- Slow recovery
- Nervous:
- Neurotransmitter
- Targets neurons muscle, glands
- Rapid onset
- Local and specific effects
- Rapid recovery
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Function of Hormone
- Modify activity of target cells
- Targets have specific receptors for specific hormones
- Distributed by blood
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Endocrine glands
Ductless glands that secret hormones directly into blood stream
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Lipid-soluble hormone
- Steroid Hormones
- -Lipid derived from cholesterol
- -eg. testosterone
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Water-soluble Hormones
- Peptide Hormone
- Biogenic amines
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Peptide Hormone
- Chains of amino acids
- Includes protein hormones (longer chains)
- Most hormones
- eg. Growth hormone
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Biogenic Amines
- Modified Amino acids
- eg. thyroid hormone
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Negative vs Positive feedback
- Negative- Occurs when the end product acts to turn off or slow down the pathway
- Positive- Occurs when the end product stimulates further pathway activity
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Location of hormone receptors
- Intracellular- Cytoplasm, nucleus, (Hormone must be lipid-soluble)
- Cell Surface- Cell membrane (Hormone must be water-soluble
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Organs of Endocrine System
- Hypothalamus
- Pituitary (anterior and posterior)
- Thyroid Gland
- Parathyroid Gland
- Adrenal gland (cortex and medulla)
- Pancreas
- Pineal gland
- Thymus
- Gonads
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Hypothalamus
- Controls anterior pituitary
- -Releasing hormones stimulate secretion
- -Antagonistic inhibiting hormones
- Secretes & stores hormones in posterior pituitary
- Neurally stimulates adrenal medulla (Master controller of ANS)
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Anterior Pituitary gland (Adenohypophysis)
- Glandular/derived from epithelial tissue
- Within hypophyseal fossa, sell turcica of sphenoid
- Attached to hypothalamus via infundibulum
- Divided into three regions
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Regions of Anterior Pituitary
- Pars Distalis
- Pars intermedia
- Pars tuberalis
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Pars Distalis
- Large, anterior portion
- Source of most hormones
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Pars intermedia
- Thin, between anterior and posterior pituitary
- Secretes melanocyte-stimulating hormone
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Pars tuberalis
Wraps around infundibulum
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Hormones of Anterior Pituitary
- Human Growth Hormone
- Prolactin
- Thyroid Stimulating Hormone (TSH)
- Adrenocorticotropic Hormones (ACTH)
- Follicle-stimulatin hormone
- Luteinizing hormone
- Melanoctye-stimulating hormone
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Human Growth Hormone (Pituitary)
- Secreted by: Somatotropic cells in pars distalis
- Target: All/most body cells (esp bone and muscle)
- Action: Stimulates liver, muscles, cartilage, bones, other tissues; Promotes growth and repair
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Prolactin (Pituitary)
- Secreted: Mammotropic cells in pars distalis
- Target: Mammary glands
- Action: Initates milk production
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Thyroid Stimulating Hormone (TSH)(Pituitary)
- Secreted: Thyrotropic cells in pars distalis
- Target: Thyroid Gland
- Action: Stimulates production of thyroid Hormone
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Adrenocortropic Hormone (ACTH)(Pituitary)
- Secreted: Corticotropic cells in pars distalis
- Target: Adrenal Cortex
- Action: Controls production/Secretion of adrenal cortex hormones
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Luteinizing hormone (Pituitary)
- Secreted: Gonadotropic cell in pars distalis
- Target: Gonads (ovaries/testes)
- Action: Production of gametes & sex hormones
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Melaoncyte-stimulating hormone (Pituitary)
- Secreted: Corticotropic cells in the pars intermedia
- Action: Appetite suppression
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Posterior Pituitary (Neurophypophysis)
- Neural rather than glandular
- Does NOT synthesize Hormones
- Consists of pas nervosa & infundibulum
- Stores and releases two hormones produced by hypothalamus (transported by hypothalmo-hypophyseal tract)
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Oxytocin
- Target:Uterus, mammary glands, smooth muscle in reproductive tract
- Action: Muscle contraction, milk ejection
- (synthesized by hypothalamus)
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Antidiuretic hormone/Vasopressin
- Target: Kidney and walls of blood vessels
- Action: Conserves water, raises blood pressure
- (synthesized by hypothalamus)
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Thyroid gland
Two lobes, joined by isthmus
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Thyroid Hormone
- Secreted: Follicular cells in thyroid
- Target: Most body cells
- Action: RAISE metabolic rate, influence development
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Calcitonin
- Secreted: Parafollicular cells in thyroid
- Target: Bone, kidney
- Action: LOWER blood calcium, RAISE calcium deposition in bone
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Parathyroid Glands
- Four small nodes
- Posterior thyroid
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Parathyroid Hormone
- Secreted: Chief cells of Parathyroid
- Target: Bone, small intestine, kidney
- Action: Increases blood calcium, increase calcium absorption in small intestines, retuen Ca2 to blood from forming urine
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Adrenal Glands
- Superior kidney surface
- Two regions:
- -Cortex: Outer glandular; 3 zones, each secret different categories of steroid hormones; Helps regulate salt sugar and sex
- -Medulla: inner, neural
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Hormones of Adrenal Cortex
- Mineralocorticoids
- Glucocorticoids
- Gonadocorticoids
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Mineralocorticoids (Adrenal)
- Secreted: Zona Glomerulosa
- Target: Kidneys
- Action: Mineral homeostasis (increase blood Na+ & Water; decrease K+)
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Glucocorticoids (adrenal)
- Secreted: Zona fasciculata
- Target: Liver
- Action: increase lipid & protein metabolism, increase blood glucose, reduce inflammation
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Gonadocorticoids (Adrenal)
- Secreted: Zona reticularis
- Target: gonads (testes and ovaries)
- Action: Assist in growth of axillars and pubic hair; contributes to libido in females
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Epinephrine&Norepinephrine (Adrenal Medulla)
- Secreted: Chromaffin cells
- Target: Many body cells, various organs
- Action: Intensify sympathetic responses
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Glucagon
- Secreted: Alpha Cells of Pancreas
- Target: Liver
- Action: Glycogen breakdown, raising blood glucose
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Insulin
- Secreted: Beta cell of Pancreas
- Target: Liver, body cells
- Action: Promotes glucose transport into cells, decreasin blood glucose
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Somatostatin
- Secreted: Delta Cells in Pancreas
- Target: Alpha & Beta cells of pancreas
- Action: Inhibits release of glucagon & insulin
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Pancreatic Polypeptide
- Secreted: F cells
- Target: Pancreas, gallbladder
- Action: Inhibits digestive secretion
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Melatonin
- Secreted: Pinealocytes of pineal gland
- Target:Hypothalamus
- Action: Promotes sleepiness; may slow sexual maturation
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Thymus Gland
- Deep to sternum; within mediastinum, superior to heart
- Bilobed
- Larger in infants & children, atrophied in adults
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Thymosins & Thymopoeitin
- Secretion: Thymus gland
- Target: T cells of immune system
- Action: Promotes development & immunocompetence
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