The Endocrine System Communication and Control. Endocrine System Same general functions as the...
-
Upload
naomi-hunt -
Category
Documents
-
view
254 -
download
0
Transcript of The Endocrine System Communication and Control. Endocrine System Same general functions as the...
The Endocrine System
Communication and Control
Endocrine System
Same general functions as the nervous system:
Nervous system – rapid, brief
Endocrine system – slow, longer-lasting
Intro Words to Know Tropic hormone – hormone that stimulates
another endocrine gland to grow and secrete its hormones
Melanocyte – specialized cells in the pigment layer that produces melanin (brown skin pigment)
Diuretic – substance that promotes or stimulates the production of urine
Antidiuretic hormone – hormone that accelerates reabsorption of water (reduces production of urine)
Objectives
Distinguish between endocrine and exocrine glands.
Define the terms hormone and prostaglandin.
Identify and locate the primary endocrine glands and list the major hormones produced by each gland.
Endocrine and Exocrine Glands
Endocrine – ductless; secrete hormones directly into bloodstream
Component of endocrine system Exocrine – discharge secretions into
ducts; sweat glands, salivary glands
Does not belong to endocrine system
Hormones and Prostaglandins
Hormones – chemicals secreted into intercellular spaces
Intercellular spaces..diffuse directly into
blood…target organ cell (hormone
molecule binds to receptor cell)
Prostaglandins – tissue hormone, diffuses only a short distance
Influence production of cyclic AMP?
Influence respiration, blood pressure, gastrointestinal secretions, and the reproductive system
Primary Endocrine Glands Pituitary 1. Cranial cavity 2. In small depression of sphenoid bone called
the sella turcica 3. Anterior lobe – growth hormone, TSH,
adrenocorticotropic hormone (ACTH), FSH, LH, melanocyte-stimulating hormone, prolactin
4. Posterior lobe – antidiuretic hormone and oxytocin
5. Often called “master gland”, but its secretions are actually controlled by the hypothalamus
Thyroid Gland
Lies in neck, just below the larynx Secretes thyroxine (T4), triiodothyronine
(T3), and calcitonin Increases body’s metabolic rate and helps
maintain homeostasis of blood calcium (decreases calcium concentration)
Parathyroid Glands
Four small glands on the back of the thyroid
Secrete parathyroid hormone Increases calcium concentration in blood
Adrenal Glands
Over the top of each kidney Adrenal cortex – mineralocorticoids,
glucocorticoids, and small amounts of sex hormones
Adrenal medulla – epinephrine and norepinephrine
Plays an essential part in maintaining blood pressure
Islands of Langerhans
Clumps of cells scattered among pancreatic cells
Alpha cells secrete glucagon Beta cells secrete insulin Insulin and glucagon are antagonists
Sex Glands
Ovaries of female (back of pelvic cavity) secrete estrogen and progesterone
Testes of male (in scrotum) secrete testosterone
Thymus
In mediastinum Not regulated by the pituitary gland Secretes thymosin ( a group of several
hormones) Essential role in the development and
function of the immune system
Placenta
Temporary endocrine gland formed during pregnancy
Secretes chorionic gonadotropin
Pineal Gland
Small cone-shaped gland Lies near the roof of the third ventricle of the
brain Secretes melatonin (thought to be involved in
regulating the onset of puberty and menstrual cycle in females)
“Third eye” – receives and responds to sensory information from the optic nerves
Helps regulate the body’s internal clock and sleep cycle
Hypothalamus and Atria
Hypothalamus (brain) – several releasing and inhibiting hormones that affect the hormone secretions of the anterior pituitary
Controls temperature, appetite, and thirst Atria (heart) – secretes atrial natriuretic
hormone (ANH) that regulates fluid and electrolyte homeostasis
Objective
Identify the principal functions of each major endocrine hormone and describe the conditions that may result from hypersecretion of hyposecretion.
Refer to pages 345-347 in text.
Objectives
Describe the mechanisms of steroid and protein hormone action.
Explain how negative and positive feedback mechanisms regulate the secretion of endocrine hormones.
Define diabetes insipidus, diabetes mellitus, gigantism, goiter, cretinism, and glycosuria.
Mechanisms of Hormone Action
Protein hormones (first messengers) bind to receptors on the target cell membrane, triggering second messengers (such as cyclic AMP) to affect the cell’s activities
Steroid hormones bind to receptor cells within the target cell nucleus and influence cell activity by acting on DNA
Negative Feedback Mechanisms
Negative – reverse the reaction of a change
Example: Pancreas releases insulin in response to elevation of sugar level in the blood. Blood sugar levels then decrease, which then causes endocrine cells in the pancreas to cease the production and release of insulin.
Positive Feedback Mechanisms
Positive – amplify the change, uncommon Example: When labor begins, the cervix
becomes distended and stimulates the synthesis of oxytocin, which stimulates the uterus to contract. As the contractions increase, the levels of oxytocin increase.
The cycle is broken by the birth of the baby.
Definitions
Diabetes insipidus – caused by hyposecretion of antidiuretic hormone produced by the posterior lobe of the pituitary gland
1. Eliminate extremely large volumes of water each day
2. Severe thirst, dehydration, electrolyte imbalance
Diabetes mellitus – Islets of Langerhans secrete too little insulin
1. Glucose cannot enter into cells, causing blood glucose to increase greatly
2. Excess sugar is filtered out of the blood into the kidneys to be lost along with urine.
Gigantism – too much growth hormone is produced by the pituitary gland
Goiter – painless enlargement of the thyroid gland caused by low dietary intake of iodine
Iodine is necessary for the synthesis of thyroid hormones
Cretinism – hyposecretion of thyroid hormones during the formative years
Low metabolic rate, retarded growth and sexual development
Frequently, mental retardation
Glycosuria – excess sugar in the urine
Occurs with diabetes mellitus (excess blood sugar is filtered out of the body by the kidneys to be transferred to urine)