Competency standard : 3. Explain the structure and function of human and certain animal organ, anomally and disease that can be occurred and its implication to social, religion, environtment, technology and society.
Basic competency : 3.6. Explain relatedness among of structure , function , process and anomally /disease that can be occurred on the human regulation system.
The endocrine system is a system of glands, each of which secretes a type of hormone to regulate the body. The endocrine system is an information signal system much like the nervous system
Endocrine glands are sometimes called ductless glands in contrast to exocrine glands such as sweat glands and glands producing digestive juices. This is because the products of endocrine glands “ Hormons “ are released into the blood without having to pass through ducts.
figure 1. Tipe pensinyalan endokrin
Hormons produced in response to either an environmental or a physiological stimulus, a hormone may come into contact with all the tissues in the body but only cells with specific receptors for that hormone are affected by it. these are known as the target cells.
Some hormones bring about long term and irreversible changes such as those initiate and bring about puberty. Other hormones are needed for day to day activities such as helping the body maintain homeostasis. These involve temporary and reversible changes.
For hormoene to be usefull to the body , there must be some way of controlling its concentration in the blood. In animals , this usually involeves a negative feedback mechanism where the secretion of a hormone stimulates a response in target cells which inhibit further secretion of the hormone.
figure 2. shows the major endocrine glands of the male body
The major centres in the body for coordinating the nervous and endocrine systems are the hypothalamus and the pituitary gland .
HYPOTHALAMUS
figure 4. shows the location of hypothalamus
The hypothalamus is a region of the brain. It contains several types of neurons responsible for secreting different hormones.
Thyrotropin-releasing hormone (TRH)
Gonadotropin-releasing hormone (GnRH)
Growth hormone-releasing hormone (GHRH)
Corticotropin-releasing hormone (CRH)
Somatostatin
Dopamine
All of these are released
Thyrotropin-releasing hormone (TRH)
TRH is a tripeptide (GluHisPro).
When it reaches the anterior lobe of the pituitary it stimulates the release there of thyroid-stimulating hormone (TSH)
prolactin (PRL)
Gonadotropin-releasing hormone (GnRH)
GnRH is a peptide of 10 amino acids. Its secretion at the onset of puberty triggers sexual development and from then on it is essential for normal sexual physiology of both males and females.
Primary Effects : FSH and LH Up
Secondary Effects : estrogen and progesterone Up (in females) testosterone Up (in males)
Growth hormone-releasing hormone (GHRH)
GHRH is a mixture of two peptides, one containing 40 amino acids, the other 44. As its name indicates, GHRH stimulates cells in the anterior lobe of the pituitary to secrete growth hormone (GH).
Corticotropin-releasing hormone (CRH)
CRH is a peptide of 41 amino acids. As its name indicates, its acts on cells in the anterior lobe of the pituitary to release adrenocorticotropic hormone (ACTH)
Somatostatin
Somatostatin is a mixture of two peptides, one of 14 amino acids, the other of 28.
Somatostatin acts on the anterior lobe of the pituitary to
inhibit the release of growth hormone (GH)
inhibit the release of thyroid-stimulating hormone (TSH)
Dopamine
Dopamine is a derivative of the amino acid tyrosine. Its principal function in the hypothalamus is to inhibit the release of prolactin (PRL) from the anterior lobe of the pituitary.
PITUITARY GLAND
- Pituitary gland: a small gland located on a stalk hanging from the base of the brain .
- “The Master Gland”
– Produces many hormones.
– Secretion is controlled by the hypothalamus in the base of the brain.
- The Pituitary Gland is divided into 2 areas, which differ
– each area has separate types of hormone production
figure 5. shows the areas of pituitary gland
The two segments are:
– Posterior Pituitary:
- produces oxytocin (stimulates gravid uterus and causes “let down” of milk from the breast.
- and antidiuretic hormone (ADH) , also known as vasopressin (this hormone not only stimulates reabsorption of water by the kidney tubules , but also raises arterial blood pressure by constricting the arterioles).
- produces thyroid-stimulating hormone (TSH) (TSH stimulates the thyroid gland to release thyroxine hormones , thus raises metabolic rate of most body cells and stimulates the synthesis of enzymes which break down glucose to provide energy)
- growth hormone (GH) (¯ glucose usage and consumption of fats as an energy source), Over – or under – secretion of this hormone result in gigantism and dwarfism respectively.
- adrenocorticotropin (ACTH) (ACTH stimulates the adrenal cortex to release its hormones)
- follicle-stimulating hormone (FSH) and luteinizing hormone (LH) (stimulates maturation & release of eggs from ovary)
- prolactin (lactation)
figure 6. shows the thyroid gland
The thyroid is one of the largest endocrine glands in the body. This gland is found in theneck, inferior to (below) the thyroid cartilage and at approximately the same level as thecricoid cartilage. The thyroid controls how quickly the body uses energy, makes proteins, and controls how sensitive the body should be to other hormones.
The thyroid participates in these processes by producing thyroid hormones, principallythyroxine (T4) and triiodothyronine (T3). These hormones regulate the rate of metabolismand affect the growth and rate of function of many other systems in the body. Iodine andtyrosine are used to form both T3 and T4. The thyroid also produces the hormonecalcitonin, which plays a role in calcium homeostasis (triggers precipitate of calcium in bone so cause decreasing calcium concentration in extracelluler liquid.
Hyperthyroidism (overactive thyroid) and hypothyroidism/myxedema (underactive thyroid) are the most common problems of the thyroid gland.- Increased thyroid hormone release causes hyperthyroidism, commonly calledGraves’ disease.
- insomnia, fatigue
- tachycardia
- hypertension
- heat intolerance
- weight loss
Figure 7; hyperthyroidism,
Myxedema symptoms:
– Facial bloating
– weakness
– cold intolerance
– lethargy
– altered mental status
– oily skin and hair
– TX: replacement of thyroid hormone.
Figure 8; myxedema
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