Hormones and the Endocrine System By Elizabeth Chapman, Alec Smith, and Niki Williams.
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Transcript of Hormones and the Endocrine System By Elizabeth Chapman, Alec Smith, and Niki Williams.
Hormones and the Endocrine System
By Elizabeth Chapman, Alec Smith, and Niki Williams
Hormones and the Endocrine System
Key Points of Focus:
• Nervous system relationship
• Maintenance of homeostasis
• Types of hormones/effects on vertebrates
• Effect on invertebrates
Review and Overview
• The Endocrine System is composed of all of the body's hormone secreting cells
• Hormones are chemical signals carried by the circulatory
system that communicate regulatory messages through the body • One hormone can elicit a variety different responses from
different target cells • There are 3 simple hormonal pathways
1.Simple endocrine2.Simple neurohormone3.Simple neuroendocrine
The Three Simple Pathways
Review of Hormonal Signaling
• Hormonal signaling occurs through the binding of a receptor protein to a target cell:
1.Water-soluble hormones bind to plasma membrane, triggering a signal transduction pathway
2. Lipid-soluble hormones bind to an intracellular receptor (Either the cytoplasm or nucleus), where it acts as a transcription factor
Review of Hormone Signaling
Water-Soluble Hormone
Hormone binds to receptor on plasma
membrane
Triggers signal transduction
pathway; leads to response
Lipid-Soluble Hormone
Signal-receptor complex acts as a transcription factor
Hormone binds to intracellular receptor either in the nucleus (as shown) or the cytoplasm
Anterior and Posterior Pituitary
anterior pituitary:• synthesizes/secretes
hormones;• four are tropic (regulate
function of other endocrine organs)
• others nontropic• growth hormone
posterior pituitary:• stores/secretes two
hormones made by hypothalamus1. ADH2. Oxytocin
Anterior Posterior Hormones
Growth Hormones• release insulin-like growth factors which circulate in the blood
to stimulate bone/cartilage growth
• hypersecretion leads to gigantism
• hyposecretion leads to dwarfism
Thyroid Gland
• Two lobes on trachea
• Maintain homeostasis (blood pressure, heart rate, muscle tone, and digestion)
• Affected by iodine in diet
Control of Blood GlucosePancreas:• produces bicarbonate ions and digestive enzymes• carried to small intestine via pancreatic duct
Exocrine: tissues and glands that discharge secretions into ducts
Islets of Langerhans: clusters of endocrine cells (in exocrine tissue of pancreas
Blood glucose regulated by glucagon and insulin
Glucagon• Raises Blood Glucose Levels
• From alpha cells
• Promotes liver's glycogen breakdown and release of glucose
• Only liver cells are responsive to glucagon
• Fat cells convert sugars to fats
• Skeletal muscles use released glucose for use in exercise
COOKIES
Insulin
• Lowers Blood Glucose Levels
• From beta cells • Slows liver's glycogen breakdown
• Inhibits conversion of amino acids and glycerol to glucose
• Promotes uptake of glucose by most somatic cells and synthesis and storage
Glucose Homeostasis (blood glucose regulation)
When blood glucose is too HIGH insulin is released to lower blood sugar concentration
When blood glucose is too LOW>glucagon is released to increase blood glucose concentration
Diabetes MellitusType 1: Insulin Dependent (usually children)• Immune system destroys pancreas's beta cells which produce insulin
Type 2: Non Insulin Dependent (anyone, yet obese susceptible)• deficiency of insulin or reduced responsiveness of target cells from change in insulin receptors
Calcium Homeostasis
Too much calcium:thyroid gland releases calcitonin which is deposited in bones; reduces kidney absorption
Too little calcium:parathyroid glands (on thyroid) release PTH, take calcium from bones, increase absorption from kidneys
Adrenal Hormones: Response to Stress
Adrenal Cortex: (outer)-made of true endocrine cells Adrenal Medulla: (center)made of secretory cells-secretes catecholamines
Catecholamines: act directly on target tissues for a bioenergetic boost
Catecholamines: Epinephrine and Norepinephrine
Positive or negative stress: catecholamines released by adrenal medulla
Epinephrine(adrenaline)- heart and metabolic rates Norepinephrine(noradrenaline) - sustains blood pressure
Functions: -increase rate of liver's glycogen breakdown -promote glucose release by liver cells -stimulate release of fatty acids from fat cells
Effects on Respiratory and Cardiovascular System -increased rate of heart beat -dilated bronchiloes in lungs, more oxygen to body -smooth muscles contract, other relax, blood goes to heart brain and skeletal muscles
Steroid Hormones from Adrenal Cortex
Adrenal cortex: endocrine signals cause hypothalamus to secrete releasing hormone that stimulates anterior pituitary gland to release tropic hormone ACTH, causes release of steroids
Corticosteroids: Mineralocortecoids-act on salt/water balanceie:aldosteronestimulates kidney cells to reabsorb salt ions and water, raising blood pressure and volume
Glucocortecoids-breakdown of muscle proteins-helps body with longterm environmental changes-anti-inflammatory, supresses immune system-carbon skeletons go to liver and kidneys, converted to glucose, released
Gonadal Sex Hormones
Androgens: (testosterone)-stimulates development of male reproductive system-can determine gender of fetus-PUBERTY
Estrogen:(estradiol)-maintenance of female reproduction system-female secondary sex characteristics
Progestins(progesterone)-prepares and maintains uterus
Melatonin and Biorhythms
Pineal gland: small mass of tissue near center of brain-sometimes has light sensitive cells that control secretory activity-synthesizes and secretes MELATONINMelatonin regulates light/season changing /day length related functions(ie: reproduction)
Invertebrate Regulatory System- Insects
Brain Hormone: made by neurosecretory cells in brain-stimulates release of ecdysone
Ecdysone: promotes molting and development of adult characteristics Balanced out by: Juvenile Hormone: promotes larval characteristics
Overlap of Endocrine and Nervous Systems
• Specialized nerve cells called neurosecretory cells release hormones into the blood via the extracellular fluid
• Some chemicals serve as both
o hormones in the endocrine systemo chemical signals in the nervous system
• Nervous system plays a role in regulating the secretion of certain
endocrine glands in certain sustained responses like the reproductive cycles of many animals
Quick Note About Local Regulators
• Local regulators convey messages between neighboring cells- paracrine signaling
• Elicit quicker responses than long-distance endocrine signaling by hormones
• The binding of a local regulator triggers events within the target cell that are similar to those elicited by hormones
• Includes neurotransmitters, the key local • regulators of the nervous system, growth factors, • prostaglandins, and nitric oxide
Group Activity
• Get one set of notecards
• Use notecards to answer questions asked by Alec, Elizabeth, or Niki
• First person to put up the correct notecard wins a point
• Group that wins gets a random bag of stuff