Chapter 11 Review
antidiuretic hormone (ADH) and oxytocin (OT)
Neurons in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin (OT), which are stored in the posterior pituitary. Impulses from the hypothalamus will release the hormones.
autocrines/paracrines
Other types of cell secretions are paracrines (affect neighboring cells) and autocrines (affect itself).
Parathyroid hormone (PTH)
PTH stimulates bone resorption by osteoclasts, which releases calcium into the blood. PTH also influences the kidneys to conserve calcium PTH causes increased absorption of calcium in the intestines. A negative feedback mechanism involving blood calcium levels regulates release of PTH.
Types of Stress
Physical stress threatens the survival of tissues, such as extreme cold, prolonged exercise, or infections. Psychological stress results from real or perceived dangers, and includes feelings of anger, depression, fear, and grief; sometimes even pleasant stimuli cause stress.
Imbalances of GH
Pituitary dwarfism - deficiency during growing years Gigantism - oversecretion during growing years Acromegaly - oversecretion in adulthood
Control Mechanisms
Release of tropic hormones from the hypothalamus controls secretions of the anterior pituitary. The nervous system influences certain endocrine glands directly. Other glands respond directly to changes in the internal fluid composition.
Cortisol
Stimulates liver cells to make glucose from noncarbohydrates, increasing blood glucose. A negative feedback mechanism involving CRH from the hypothalamus and ACTH from the anterior pituitary controls the release of cortisol. Stress, injury, or disease can also trigger increased release of cortisol.
Hypothalamic control of the pituitary gland
The posterior pituitary stores hormones made by the hypothalamus and releases them into the bloodstream in response to nerve impulses from the hypothalamus.
Structure of the Adrenal Glands
The pyramid-shaped glands consist of an inner adrenal medulla and an outer adrenal cortex.
introduction
There are similarities and differences in how the nervous and endocrine systems communicate with cells. The endocrine system's function is to communicate with cells using chemicals called hormones. Endocrine glands and their hormones regulate a number of metabolic processes within cells, and the whole body. Their actions are precise, they only affect specific target cells.
hypophyseal portal veins
These hormones are carried in the bloodstream directly to the anterior pituitary by hypophyseal portal veins. Specific cells are then stimulated to release or to stop releasing their hormone
Thyroid follicular cells
These hormones are essential for normal growth and development and nervous system maturation. Thyroid hormones are the major factors in determining the basal metabolic rate (BMR). The hypothalamus and pituitary gland control release of thyroid hormones. Iodine is needed by the follicular cells to make thyroid hormones. Both hormones are transported in the blood by plasma proteins.
thyroxine/triiodothyronine
These two hormones increase the rate at which cells release energy from carbohydrates, enhance protein synthesis, and stimulate the breakdown and mobilization of lipids.
Nonsteroid hormones /cyclic AMP
This enzyme removes two phosphates from ATP to produce cyclic AMP (the second messenger), which in turn activates protein enzymes that activate proteins. These activated proteins induce changes in the cell. Not all nonsteroid hormones use cAMP; others use diacylglycerol (DAG) or inositol triphosphate.
Diabetes mellitus
Type 1 diabetes mellitus (IDDM) is an autoimmune disorder where beta cells are destroyed. Type 2 diabetes mellitus (NIDDM) is when insulin is produced but is not recognized by cells. Symptoms - hyperglycemia, glycosuria, polydipsia, polyphagia, acidosis
Hormones of the Adrenal cortex
aldosterone-conserves sodium, cortisol-stress hormone & increases glucose, and the sex hormones.
Prostaglandins
are locally-produced lipids that usually affect the organ in which they are produced.
Steroid hormones
are synthesized from cholesterol, are lipid-soluble, and can pass through cell membranes. They are carried in the blood stream weakly bound to plasma proteins. Receptors for steroid hormones are located in the target cell's nucleus. The hormone-receptor complex binds with the DNA and activates specific genes that, in turn, direct the synthesis of specific proteins.
Nonsteroid hormones
combine with receptors in target cell membranes; the receptors have a binding site and an activity site. The hormone-receptor complex (as first messenger) triggers a cascade of biological activity through the cell membrane to the inside - called signal transduction. The hormone-receptor complex generally activates a G protein, which then activates the enzyme adenylate cyclase that is bound to the inner cell membrane.
Parathyroid glands
consist of tightly packed secretory cells covered by a thin capsule of connective tissue.
Anterior pituitary (anterior lobe)
consists mostly of glandular epithelial tissue arranged around blood vessels and enclosed in a capsule of collagenous connective tissue.
Posterior pituitary (posterior lobe)
consists of nerve fibers and neuroglial cells that support nerve fibers arising in the hypothalamus.
negative feedback mechanisms
control hormonal releases. In a negative feedback system, a gland is sensitive to the concentration of the substance it regulates or which regulates it. When the concentration of the regulated substance reaches a certain level (high or low), it inhibits the gland from secreting more hormone until the concentration returns to normal.
Adrenocorticotropic hormone (ACTH)
controls the secretion of hormones from the adrenal cortex. It is regulated by corticotropin- releasing hormone from the hypothalamus. Stress can also increase its release
Thyroid-stimulating hormone (TSH)
controls the secretion of hormones from the thyroid gland. (anterior pituitary)
In the resistance stage
cortrotropin releasing hormone (CRH) from the hypothalamus to the anterior pituitary, increases adrenocorticotropic hormone (ACTH) to the adrenal cortex.
Insulin
decreases the blood levels of glucose by stimulating the liver to form glycogen, promotes facilitated diffusion of glucose into cells, increases protein synthesis, and stimulates adipose cells to store fat.
Hormones of the Adrenal Medulla
epinephrine and norephinephrine- raises blood pressure
The ovaries produce
estrogen and progesterone.
Releasing and inhibiting hormones
from the hypothalamus control the secretions of the anterior pituitary.
Thyrotropin-releasing hormone (TRH)
from the hypothalamus regulates the release of TSH. As blood concentrations of thyroid hormones increases, secretions of TRH and TSH decrease. (anterior pituitary)
Parathyroid hormone (PTH)
increases blood calcium ion concentration and decreases phosphate ion concentration.
Glucagon
increases the blood levels of glucose by stimulating the breakdown of glycogen and the conversion of noncarbohydrates into glucose by the liver. The release of glucagon is controlled by a negative feedback system involving low blood glucose levels.
The alarm stage
involves the "fight or flight" responses of the sympathetic nervous system.
The pituitary gland
is attached to the base of the brain by a stalk called the infundibulum that connects the pituitary gland to the hypothalamus (the boss)
The thyroid gland
is located below the larynx and consists of two broad lobes connected by an isthmus. Structure of the Gland--- The thyroid consists of secretory parts called follicles filled with hormone-storing colloid.
The adrenal medulla
is made up of modified postganglionic neurons that are connected to the sympathetic nervous system.
Cortisol, a glucocorticoid,
is produced by cells of the middle layer. It influences the metabolism of glucose, protein, and fat in response to conditions that stress the body and require a greater supply of energy in the bloodstream.
Aldosterone, a mineralocorticoid,
is secreted by cells of the outer layer. It causes the kidneys to conserve sodium ions and thus water, and to excrete potassium ions. Aldosterone is secreted in response to decreasing blood volume and blood pressure as a result of changes detected in the kidney.
The thymus
lying between the lungs under the sternum, secretes thymosins that affect production and differentiation of T lymphocytes that are important in immunity. The gland is the largest in children and shrinks with age.
The adrenal cortex
makes up most of the adrenal glands and consists of epithelial cells in three layers--an outer (glomerulosa), middle (fasciculata), and an inner (reticularis) zone.
Stress
may be physical, psychological, or some combination of the two.
The pineal gland/melatonin/circadian rhythms
near the upper portion of the thalamus, secretes melatonin, which is involved in the regulation of circadian rhythms of the body. It is released at night. May help to regulate female reproductive cycles and puberty.
Oxytocin (OT)
plays a role in childbirth by contracting muscles in the uterine wall, and in milk-letdown by forcing milk into ducts from the milk glands.
the testes
produce testosterone
The placenta
produces estrogen, progesterone, and gonadotropin.
Antidiuretic hormone (ADH)
produces its effect by causing the kidneys to conserve water.
Prolactin (PRL)
promotes milk production following the birth of an infant. (anterior pituitary)
The hypothalamus
regulates the secretion of ADH based on the amount of water in body fluids. Osmoreceptors sense changes in osmotic pressure in body fluids. Diabetes insipidus - insufficient ADH
The kidneys
secrete erythropoietin for blood cell production.
The heart
secretes atrial natriuretic peptide affecting sodium and water.
The pancreas
secretes hormones as an endocrine gland, and digestive juices to the digestive tract as an exocrine gland.
The adrenal glands
sit atop the kidneys enclosed in a layer of adipose and connective tissues.
Hormones are:
steroids, amines, peptides, proteins, or glycoproteins; they can influence target cells even if they are present only in minute concentrations.
Growth hormone (GH)
stimulates body cells to grow and reproduce; it also speeds the rate at which cells use carbohydrates and fats. Growth hormone-releasing hormone (GHRH) from the hypothalamus increases the amount of GH released, GH release-inhibiting hormone (GHIH) inhibits its release. Nutritional status affects the release of GH; more is released when nutrients are insufficient.
Endocrine glands include
the pituitary gland, thyroid gland, parathyroid glands, adrenal glands, pancreas, pineal gland, reproductive glands (ovaries and testes), thymus gland, and other hormone-secreting tissues.
The endocrine system
works with the nervous system to maintain homeostasis.
Disorders of adrenal hormones
Addison disease - hyposecretion Cushing syndrome - hypersecretion
Cortisol
Cortisol inhibits protein synthesis which increases blood amino acids. It promotes fatty acid release from adipose tissue, increasing use of fatty acids for energy and decreases use of glucose.
Parathyroid hormone disorders
Hypoparathyroidism - blood calcium decrease Hyperparathyroidism - blood calcium increase
Thyroid disorders
Hypothyroidism - under activity Hyperthyroidism - over activity
Actions of cortisol from the adrenal cortex
Increased blood amino acids, fatty acid release, and glucose formation from noncarbohydrates. Decrease in lymphocytes which lowers resistance to infections and some cancers. Long-term risk of high blood pressure, atherosclerosis, and GI ulcers.
hormones
The endocrine system is made up of the cells, tissues, and organs that secrete hormones into body fluids.
calcitonin
Extrafollicular cells of the thyroid secrete calcitonin, which lowers blood levels of calcium and phosphate ions when they are too high.
stressors
Factors that serve as stressors to the body produce stress and threaten homeostasis. Stressors increase the activity of the sympathetic nervous system.
Gonadotropins
Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) affect the male (testes) and female (ovaries) gonads. In males, LH is also known as interstitial-cell stimulating hormone (ICSH).
target cells
Hormones diffuse into the bloodstream to act on target cells some distance away.
epinephrine and norepinephrine
The adrenal medulla secretes epinephrine and norepinephrine into the blood stream.
exocrine/endocrine
The body has two kinds of glands, exocrine (secretes products into ducts) and endocrine (secrete products into body fluids to affect target cells).
Thyroid Hormones
The follicular cells produce two iodine-containing hormones, thyroxine (T4 ) (tetraiodothyronine) and triiodothyronine (T3 - the more potent form), that together regulate energy metabolism.
stress response
The hypothalamus controls the stress response or general adaptation syndrome, which involves the "alarm" stage and the "resistance" stage
structure of the pancreas
The pancreas is an elongated organ posterior to the stomach. Its endocrine portions are the pancreatic islets (islets of Langerhans) that include two cell types - alpha cells that secrete glucagon, and beta cells that secrete insulin. A duct joins the pancreas to the duodenum for digestive juices to enter the intestine.