Endocrine System Dr. M. Diamond. Body Control and Messaging Uses chemical messengers (hormones) that...
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Transcript of Endocrine System Dr. M. Diamond. Body Control and Messaging Uses chemical messengers (hormones) that...
![Page 1: Endocrine System Dr. M. Diamond. Body Control and Messaging Uses chemical messengers (hormones) that are released into the blood Hormones control several.](https://reader035.fdocuments.in/reader035/viewer/2022062317/5a4d1b517f8b9ab0599a7bea/html5/thumbnails/1.jpg)
Endocrine System
Dr. M. Diamond
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Body Control and Messaging• Uses chemical
messengers (hormones) that are released into the blood
• Hormones control several major processes– Reproduction– Growth and development– Mobilization of body
defenses– Maintenance of much of
homeostasis– Regulation of metabolism
• Hormones are produced by specialized cells
• Cells secrete hormones into extracellular fluids
• Blood transfers hormones to target sites
• These hormones regulate the activity of other cells
• Work at a distance
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Hormones• Hormones are classified
chemically as– Amino acid–based, including
• Proteins• Peptides• Amines
– Steroids—made from cholesterol– Prostaglandins—made from highly
active lipids• Hormones
– Affect only certain tissues or organs (target cells or target organs)
– Have specific protein receptors on target cells
– Binding alters cellular activity
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Hormone Effects• Changes in plasma
membrane permeability or electrical state
• Synthesis of proteins, such as enzymes
• Activation or inactivation of enzymes
• Stimulation of mitosis• Promotion of secretory
activity
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Hormone Action Mechanisms
• Direct gene activation• Second-messenger
system (signal transduction)
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Steroid Hormones• Direct gene activation• Diffuse through the
plasma membrane of target cells
• Enter the nucleus• Bind to
– a specific protein within the nucleus
– specific sites on the cell’s DNA
• Activate genes that result in synthesis of new proteins
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Protein Hormones• Second messenger system• Hormone binds to a membrane
receptor• Hormone does not enter the
cell• Sets off a series of reactions
that activates an enzyme• Catalyzes a reaction that
produces a second-messenger molecule
• Oversees additional intracellular changes to promote a specific response
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Control of Hormone Release• Hormone levels in the
blood are mostly maintained by negative feedback
• A stimulus or low hormone levels in the blood triggers the release of more hormone
• Hormone release stops once an appropriate level in the blood is reached
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Endocrine Gland Stimuli
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Hormonal Stimulus
• Endocrine gland stimulated by hormone, most notably from:– Hypothalamus– Pituitary
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Neural stimulus• Nerve impulses stimulate
hormone release• Most are under the
control of the sympathetic nervous system
• Examples include the release of norepinephrine and epinephrine by the adrenal medulla
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Neural Stimulus
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Humoral Stimulus• Changing blood levels of
certain ions stimulate hormone release
• Humoral indicates various body fluids such as blood and bile
• Examples:– Parathyroid hormone
(Parathormone)– Calcitonin– Insulin
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Major Endocrine Glands• Hypothalamus• Pituitary gland• Thyroid gland• Parathyroid glands• Adrenal glands• Pineal gland• Thymus gland• Pancreas• Gonads (Ovaries and
Testes)
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Hypothalamus• Neuroendocrine• Neurosecretory cells produce
two hormones– Anti-diuretic hormone (ADH)– Oxytocin– Transported and stored in
posterior pituitary• Produces releasing and
inhibiting hormones that act on the ant. pituitary:– Thryrotropin-releasing hormone– Gonadotropin-releasing
hormone– Growth hormone-releasing
hormone
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Pituitary-Hypothalamus Relationship
• Hormonal release is regulated by releasing and inhibiting hormones produced by the hypothalamus
• Hypothalamus produces two hormones– These hormones are
transported to neurosecretory cells of the posterior pituitary
• Oxytocin• Antidiuretic hormone (also
known as Vasopressin)• The posterior pituitary is not
strictly an endocrine gland, but does release hormones
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Hypothalamus-Pituitary
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Pituitary• Size of a pea• Hangs by a stalk from the
hypothalamus in the brain• Protected by the
sphenoid bone• Has two functional lobes
– Anterior pituitary—glandular tissue
– Posterior pituitary—nervous tissue
• Often called the “master endocrine gland”
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Anterior Pituitary• Six anterior pituitary
hormones– Two affect non-endocrine
targets• Growth hormone• Prolactin
– Four stimulate other endocrine glands (tropic hormones)
• Thyroid-stimulating hormone (thyrotropic hormone)
• Adrenocorticotropic hormone
• Two gonadotropic hormones
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Posterior Pituitary• Oxytocin
– Stimulates contractions of the uterus during labor, sexual relations, and breastfeeding
– Causes milk ejection during nursing
• Antidiuretic hormone (ADH) – Inhibits urine production by
promoting water reabsorption by the kidneys
– In large amounts, causes vasoconstriction leading to increased blood pressure
– Also known as vasopressin
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Pituitary Hormones