Regulatory molecules secreted by the endocrine glands. The blood carries the Regulatory molecules to target cells that contain specific receptor proteins for the Regulatory molecules and therefore can respond to them in a specific fashion. It affect the metabolism of their target organs and, by this means, help regulate total body metabolism, growth, and reproduction.

Regulatory molecules secreted by the endocrine glands. The blood carries the Regulatory molecules to target cells that contain specific receptor proteins for the Regulatory molecules and therefore can respond to them in a specific fashion. It affect the metabolism of their target organs and, by this means, help regulate total body metabolism, growth, and reproduction.

Chemical messengers secreted by specialized neurons (particularly in the hypothalamus) secreted into the blood rather than into the synaptic cleft.

Regulatory molecules that do not travel in the bloodstream.

Regardless, in order for both (hormones and neurotransmitter) to function in physiological regulation:

Hormone Classification:

derived from tyrosine and tryptophan.

Hormone Classification:

Divided into catecholamines and thyroid hormones.

Hormone Classification:

Large polypeptides

Hormone Classification:

proteins bound to one or more carbohydrate groups.

Hormone Classification:

Derived from cholesterol after an enzyme cleaves off the side chain attached to the five-carbon “D”-ring.

Hormone Classification:

Secreted by only 2 adrenal glands: the adrenal cortex and the gonads

determine the means by which it is synthesized, stored, and secreted; how it is transported in the blood; the mechanism by which it exerts its effects at the target cell, and typically, the type of processes regulated (rapid versus long-term) and their halflives (turnover) in the circulation.

Non-polar, lipid-soluble hormones that can gain entry into their target cells

All steroid hormones and the thyroid hormones.

Polar, water-soluble hormones

polypeptides, glycoproteins, and the catecholamine hormones secreted by the adrenal medulla, epinephrine and norepinephrine.

Hormone molecules that affect the metabolism of target cells are often derived from less active “parent,” or precursor, molecules.

Refers to molecules that are secreted by endocrine glands but are inactive until they are converted within their target cells into the active forms of the hormones

Thyroxine and Testosterone specifically

1. Ribosomes on the RER synthesize preprohormones (large precursor proteins). These migrate to the Golgi complex in membrane-enclosed vesicles that pinch off from the SER.

2. During the journey through the SER and the Golgi complex the preprohormone molecules are pruned into prohormones and finally to hormones.

3. The Golgi complex concentrates the finished hormones and stores them in secretory vesicles. 4. On appropriate stimulation, the secretory vesicles fuse with the plasma membrane and release their contents to the outside by the process of exocytosis.

1. Cholesterol is the common precursor of all these hormones.

2. Synthesis of the various hormones from cholesterol involves a series of enzymatic reactions that modify the type and position of side groups attached to the cholesterol framework or the degree of saturation within the rings.

3. Steroid hormones cannot be stored after their formation. Accordingly, the rate of this hormone secretion is controlled entirely by the rate of hormone synthesis.

4. After their secretion into the circulation, some hormones undergo further interconversions within the blood or other organs, where they are converted into more potent or different hormones.

1. They are derived from the amino acid tyrosine.

2. Both types are stored until secreted.

3. Thyroid hormone also undergoes further processing once in the peripheral circulation.

When two or more hormones work together to produce a particular result, their effects are said to be

These effects may be additive or complementary

A hormone is said to have this effect on the action of a second hormone when it enhances the responsiveness of a target organ to the second hormone, or when it increases the activity of the second hormone.

In some situations, the actions of one hormone oppose the effects of another.

Ex. Insulin and glucagon

The concentration of hormones in the blood primarily reflects the rate of secretion by the endocrine glands. Hormones do not generally accumulate in the blood because they are rapidly removed by target organs and by the liver.

Normal tissue responses are produced only when the hormones are present within their normal, or physiological, range of concentrations. When some hormones are taken in abnormally high, or pharmacological, concentrations (as when they are taken as drugs), their effects may be different from those produced by the lower physiological concentrations.

Variations in hormone concentration within the normal, physiological range can affect the responsiveness of target cells. More receptors may be formed in the target cells in response to particular hormones. It caused in large part by the upregulation of receptors.

Prolonged exposure to high concentrations of polypeptide hormones has been found to desensitize the target cells. Subsequent exposure to the same concentration of the same hormone thus produces less of a target tissue response

Located in the inferior aspect of the brain. - Approximately pea-sized, it is attached to the hypothalamus via a structure called the infundibulum.

Structurally and functionally divided into 2 parts:

1. The anterior lobe or adenohypophysis

2. posterior lobe or neurohypophysis.

Two parts in adults:

Pars distalis (Anterior pituitary) – the major endocrine part of the gland.

Pars tuberalis – sheathe of tissue that partially wraps around the infundibulum.

In the fetus a pars intermedia exists between the anterior and posterior lobes

Two parts in adults:

Pars distalis (Anterior pituitary) – the major endocrine part of the gland.

Pars tuberalis – sheathe of tissue that partially wraps around the infundibulum.

In the fetus a pars intermedia exists between the anterior and posterior lobes

Hormones of the Adenohypophysis (Trophic hormones):

promotes the movement of amino acids into cells and their incorporation into proteins, promoting overall tissue and organ growth.

Hormones of the Adenohypophysis (Trophic hormones):

somatotropin

Hormones of the Adenohypophysis (Trophic hormones):

stimulates the thyroid gland to produce and secrete thyroxine (T4) and triiodothyronine (T3).

Hormones of the Adenohypophysis (Trophic hormones):

thyrotropin

Hormones of the Adenohypophysis (Trophic hormones):

stimulates the adrenal cortex to secrete glucocorticoids

Hormones of the Adenohypophysis (Trophic hormones):

corticotropin

Hormones of the Adenohypophysis (Trophic hormones):

A gonadotropic hormone. Stimulates the growth of ovarian follicles in the female and the production of sperm in the testes of males

Hormones of the Adenohypophysis (Trophic hormones):

folliculotropin

Hormones of the Adenohypophysis (Trophic hormones):

A gonadotropic hormone. Stimulates ovulation in the female. Sometimes called Interstitial cell-stimulating hormone (ICSH) in males because it stimulates the secretion of male sex hormones from the interstitial endocrine cells (Leydig cells) of the testes

Hormones of the Adenohypophysis (Trophic hormones):

luteotropin

Hormones of the Adenohypophysis (Trophic hormones):

stimulates milk production in the female

Hormones of the Adenohypophysis (Trophic hormones):

stimulates milk production in the female

Two parts in adults:

Pars nervosa (Posterior pituitary) – in contact with the adenohypophysis. Stores and releases two hormones, both of which are produced by the hypothalamus: 1. Antidiuretic hormone (ADH) 2. Oxytocin

Infundibulum – nerve fibers extend into the infundibulum along with small neuroglia-like cells called pituicytes

ADH and Oxytocin are both produced in neuron cell bodies of the supraoptic and paraventricular nuclei in the hypothalamus. They are transported along axons of the hypothalamo-hypophyseal tract to the _____ where they are stored.

This reflex control the release of ADH and Oxytocin

Releasing and Inhibiting hormones (produced by the hypothalamus) are transported to axon endings in the median eminence, the basal portion of the hypothalamus. Blood capillaries present here are drained by venules at the stalk of the pituitary. The hypothalamo-hypophyseal portal system downstream of these venules allows the hormones to then activate the cells of the ________:

Thyrotropin-Releasing Hormone (TRH) – secretion of TSH

Corticotropin-Releasing Hormone (CRH) – secretion of ACTH

Gonadotropin-Releasing Hormone (GnRH) – secretion of both gonadotropic hormones (FSH and LH).

Growth-Hormone-Releasing Hormone (GHRH) – secretion of GH

Somatostatin – inhibits GH secretion

Prolactin-inhibiting Hormone (Dopamine) – inhibits prolactin secretion.

Oxytocin

_____ is inhibited by a rise in corticosteroid secretion

____ is inhibited by a rise in the secretion of T4 from the thyroid

Feedback Control Inhibitory Effect

The target gland hormones act on the ________ to inhibit the secretion of releasing hormones

The relationship between the pituitary and its target gland is called a/an ______. Since the hypothalamus receives neural input from the “higher brain centers” it is not surprising that these can be affected by the organisms state of mind (stress, emotions) and even sensory inputs

- Paired organs that cap the superior borders of the kidneys. -

Each consists of an outer cortex and an inner medulla that function as separate glands.

- The adrenal medulla secretes catecholamines (mainly epinephrine, with lesser amounts of norepinephrine).

- The cortex secretes corticosteroids.

Hormones of the Adrenal Cortex (Corticosteroids)

regulate Na+ and K+ balance. Aldosterone is the most potent

Hormones of the Adrenal Cortex (Corticosteroids)

regulates the metabolism of glucose and other organic molecules. Cortisol (Hydrocortisone) is the predominant

Hormones of the Adrenal Cortex (Corticosteroids)

supplement the sex steroids produced by the gonads

Cortisol and other glucocorticoids have many effects on metabolism:

taken as pills, injections, sprays, and topical creams) are used medically to suppress the immune response and inhibit inflammation.

results from chronically high levels of glucocorticoids

caused by inadequate secretion of corticosteroids

The cells of the _____ secrete epinephrine and norepinephrine in an approximate ratio of 4 to 1. These hormones increase the cardiac output and heart rate, dilate coronary blood vessels, increase mental alertness, increase the respiratory rate, and elevate the metabolic rate

Stress causes a rise in the plasma glucocorticoid levels, producing a nonspecific response termed General Adaptation Syndrome (GAS). The following are the stages of stress expect:

In humans located just below the larynx. It is the largest of the purely endocrine glands.

- The interior of the follicle contains colloid, a protein-rich fluid

Composed of thyroid follicles lined with follicular cells which produce thyroxine and parafollicular cells that secrete calcitonin.

It inhibits the activity of osteoclasts and stimulates the urinary excretion of Ca2+ by the kidneys. Both of these actions lower the blood Ca2+ concentration and antagonize the effects of parathyroid hormones

Embedded in the posterior surfaces of the lateral lobes of the thyroid gland. - Usually four pairs, a superior and an inferior pair. - (PTH) is the only hormone secreted by the gland. However, it is the single most important hormone for controlling blood calcium concentration by acting on the bones, kidneys, and intestine

The endocrine portion is consists of scattered clusters of cells called the (islets of Langerhans). - The Islets contain alpha cells that secrete glucagon and beta cells that secrete insulin

allow the facilitated diffusion of glucose into the cell

The endocrine portion is consists of scattered clusters of cells called the (islets of Langerhans). - The Islets contain alpha cells that secrete glucagon and beta cells that secrete insulin

Located on the roof of the third ventricle of the diencephalon, where it is encapsulated in the meninges of the brain. Secretes melatonin. The suprachiasmatic nucleus (SCN) of the hypothalamus regulates this gland's secretion. It is also the primary center for controlling our circadian rhythms

The stomach and small intestine secrete a number of hormones that act on the gastrointestinal tract itself and on the pancreas and gallbladder

secrete sex steroids. These include male sex hormones, or androgens, and female sex hormones—estrogens and progesterone.

the organ responsible for nutrient and waste exchange between the fetus and mother—is also an endocrine gland that secretes large amounts of estrogens and progesterone, as well as other hormones to facilitate placental growth