The Endocrine System. INTRODUCTION Endocrine v Nervous Endocrine system Endocrine system Releases...
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Transcript of The Endocrine System. INTRODUCTION Endocrine v Nervous Endocrine system Endocrine system Releases...
The Endocrine System
INTRODUCTION
Endocrine v Nervous
Endocrine system Releases hormones into interstitial fluid blood general circulation
Effectors: virtually any type of body cell; can have widespread effects on diverse aspects of metabolism
Slower, longer-lasting responses as hormones linger in blood
Hormone Action
• Hormones are carried in blood stream • Only certain cells can be affected by
hormones– These target cells have 1000’s of receptors
specific for a particular hormone.– Response determined by target cell:
different cells may respond differently to the same hormone.
Location of Endocrine Glands
HORMONE CHEMISTRY
Lipid-Soluble Hormones
• Steroids, such as testosterone, estrogens• Thyroid hormones: T3 and T4 • Nitric oxide (NO)
Lipid-Soluble Hormones
1Lipid-solublehormonediffuses into cell
Blood capillary
Activatedreceptor-hormonecomplex altersgene expression
NucleusReceptor
mRNANewly formedmRNA directssynthesis ofspecific proteinson ribosomes
DNACytosol
Target cell
Transportprotein
Free hormone
Ribosome
2
3
Water Soluble Hormones
• Amino acid derivatives, such as epinephrine, norepinephrine
• Peptides: antidiuretic hormone (ADH), oxytocin
• Proteins: insulin and growth hormone
Water Soluble Hormones
Water-solublehormoneReceptor
cAMP serves as asecond messengerto activate proteinkinases
G protein
Protein kinases
cAMP
Activatedproteinkinases
Protein—
Second messenger
Phosphodiesteraseinactivates cAMP
Activated adenylatecyclase convertsATP to cAMP
Activated proteinkinasesphosphorylatecellular proteins
Millions of phosphorylatedproteins cause reactions thatproduce physiological responses
Blood capillary
Binding of hormone (first messenger)to its receptor activates G protein,which activates adenylate cyclase
Adenylate cyclase
Target cell
P
ADP
Protein
ATP
ATP
1
2
6
4
3
5
Control of Secretions
Release occurs in short burstsRegulated by• Signals from nervous system
– Example: epinephrine• Chemical changes in blood
– Example: blood Ca2+ affects PTH• Other hormones
– Example: ACTH from pituitary stimulates release of cortisol from adrenal cortex
HYPOTHALAMUS & PITUITARY
Anterior Pituitary
Also called the adenohypophysis; it produces:• hGH (somatotropin)• IGF (Insulinlike Growth Factor)• TSH – Thyroid Stimulating Hormone• FSH – Follicle Stimulating Hormone
Anterior Pituitary
• LH – Luteinizing Hormone• PRL – Prolactin• ACTH – Adrenocorticotropic Hormone• MSH – Melanocyte Stimulating Hormone• These are all regulated by release factors
made in the hypothalamus
Posterior Pituitary
Also called the neurohypophysis; it stores and releases:
• Oxytocin• ADH – Antidiuretic Hormone• These substances are produced by the
hypothalamus
GLANDS OF THE BODY
The Thyroid Gland
Produces thyroxin (T4) and triiodothyronine (T3)
• Actions: Increases BMR (rate of O2 consumption) → body temp
• Body growth and developmentAlso produces calcitonin• Lowers blood levels of Ca, P
The Parathyroid Glands
Produces Parathyroid Hormone (PTH)• Increases blood levels of Ca, P, Mg
The Pancreas
Pancreas is both endocrine and exocrine (digestive enzymes)
Islets of Langerhans produce glucagon and insulin
• Glucagon increases blood levels of glucose• Insulin decreases blood glucose levels
The Adrenal Glands
Adrenal Cortex• Mineralocorticoids such as Aldosterone –
regulates Na+ (reabsorption) and K+ (excretion)• Glucocorticoids such as Cortisol – breaks down
proteins and triglycerides; anti-inflammatory
The Adrenal Glands
Adrenal Medulla• Produces epinephrine and norepinephrine• Stress response;• Fight-or-flight
The Pineal Gland
Produces melatonin• Biological clock• Levels increase in darkness and during sleep• Levels high in infants and young children;
lower in adults