Endocrine System
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Transcript of Endocrine System
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Endocrine System
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ENDOCRINE GLANDS• Secrete hormones directly into
bloodstream• DuctlessEXOCRINE GLANDSsecrete substances through a duct (sweat,
salivary, lacrimal and pancreas)
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Function of the Endocrine System – to secrete hormones – chemical messengers
that coordinate and direct target cells and organs.
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Hormonal Control
NEGATIVE FEEDBACK• Drop in hormone level triggers a chainreaction to increase secretion, for example 1. Blood level of hormone falls 2. Brain gets message and sends out hormone to stimulate gland 3. Gland stimulates more hormone 4. When blood levels of hormone increase, the brain hormones stop
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Nervous Control – in some cases, sympathetic
nervous system causes direct release of hormone
from gland (for example, when stress causes the
adrenal medulla to secrete adrenalin)
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Hormone Transport in Blood
• Water-soluble hormones are transported dissolved in blood plasma.
• Others circulate in blood, bound to plasma proteins.
• The free hormone diffuses across capillary walls to encounter its target cells.
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The Endocrine System Consists of several glands located in various parts of
the body Specific Glands
Hypothalamus Pituitary Thyroid Parathyroid Adrenal Kidneys Pancreatic Islets Ovaries Testes
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Hypothalamus Produces several releasing and inhibiting factors
that stimulate or inhibit anterior pituitary’s secretion of hormones.
Produces hormones that are stored in and released from posterior pituitary.
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Hypothalamus Also responsible for:
Regulation of water balanceEsophageal swallowingBody temperature regulation (shivering)Food/water intake (appetite)Sleep-wake cycleAutonomic functions
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PITUITARY GLAND• Tiny structure the size of a grape
• Located at the base of the brain
• Connected to the hypothalamus
• Divided into anterior and posterior lobes• The “Master Gland”
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Pituitary Gland Two areas
Anterior PituitaryPosterior Pituitary
Structurally, functionally different
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Anterior Pituitary Lobe• GROWTH HORMONE – GH(SOMATOTROPIN)
- responsible for growth and development
• PROLACTIN – develops breast tissue,stimulates production of milk after childbirth• THYROID-STIMULATING HORMONE – TSH -stimulates thyroxine• ADRENOCORTICOTROPIC HORMONE
(ACTH) – stimulates adrenal cortex
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Anterior Pituitary Lobe (cont)
• FOLLICLE-STIMULATING HORMONE (FSH) -stimulates growth of graafian follicle
andproduction of estrogen in females, sperm in males
• LUTEINIZING HORMONE – LH – stimulatesovulation and formation of corpus luteum,
which produces progesterone in females
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Posterior Pituitary Lobe
• VASOPRESSIN – converts to ADH(antidiuretic hormone) in the bloodstream,
acts on kidney to concentrate urine and preserve H2O in the body
• OXYTOCIN – released during childbirthcausing contractions of the uterus
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THYROID GLAND• Butterfly-shaped mass of tissue• On either side of larynx, over trachea• H-shaped
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Thyroid Hormones
• Main hormone – THYROXINE – is controlled
by the secretion of TSH• Thyroxine controls the rate of metabolism• CALCITONIN – controls calcium ion
concentration in the body, prevents hypercalcemia
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PARATHYROID GLANDS• Four glands, each the size of a grain of rice• Attached to posterior thyroid• Produce PARATHORMONE which helpscontrol blood calcium level, preventshypocalcemia
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THYMUS• Endocrine gland and lymphatic organ• Located behind the sternum, above and infront of the heart• Begins to disappear at puberty
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ADRENAL GLANDS• Located on top of each kidney• Adrenal cortex secretes hormones known atcorticoids – they are anti-inflammatory• They are: mineralcorticoids, glucocorticoids,and sex hormones
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Adrenal Hormones
• ANDROGENS are male sex hormones• Adrenal medulla secretes epinephrine(adrenalin) and norepinephrine
• ADRENALIN is a powerful cardiac stimulent –
“fight or flight” hormones that prepare the body
for an emergency situation
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GONADS• Ovary in female• Testes in male• Estrogen – development of female reproductive
organs, secondary sex characteristics• Progesterone – plays a part in the menstrualcycle• Testosterone – male reproductive organs andsecondary sex characteristics
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PANCREAS• Located behind the stomach• Endocrine and exocrine functions• Involved in production of INSULIN by ISLETSOF LANGERHANS• Insulin – promotes utilization of glucose by thecells, fatty acid and amino acid transport, andfacilitates protein synthesis
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Other HormonesPROSTAGLANDINS – tissue hormones, cancause constriction of blood vessels, musclecontractions. Can be used to induce labor.