Endocrine Sytem Flashcards
consists of several endocrine glands and many hormone-secreting cells in organs
Endocrine System
considered to be ductless; hormone is secreted via the interstitial fluid then into the bloodstream and towards the different target organs
Endocrine glands
In contrast to the nervous system, which controls body activities through the release of neurotransmitters at synapses
Endocrine System
Functions of Hormones (5 items)
EXPLAIN
- Reproduction: can be seen in the function of ovaries and testes
- Growth and development: growth hormones are responsible for growth and development of the body
- Mobilization of body defenses: involves immune activities
- Maintenance of homeostasis
- Regulation of metabolism
T or F
Hormones affect only specific target cells that have the specific protein receptors to bind to a given hormone
Chemically, hormones are either lipid-soluble or water-soluble
True
act on receptors inside the cell which directly activate genes; affect the cell function by altering gene expression (e.g. steroid & thyroid hormones)
Lipid-soluble hormones:
alter cell function by activating the plasma membrane receptors which elicit production of a second messenger that activates various proteins inside the cell (e.g. modified amino acids, proteins, peptides; all amino acid-based hormones except thyroid hormones)
Water-soluble hormones
Mechanism of Action of Lipid-Soluble Hormones
a free lipid-soluble hormone molecule diffuses from the blood, through interstitial fluid, and through the lipid bilayer of the plasma membrane into a cell.
If the cell is a target cell, the hormone binds to and activates receptors located within the cytosol or nucleus. The activated receptor–hormone complex then alters gene expression: It turns specific genes of the nuclear DNA on or off.
As the DNA is transcribed, new messenger RNA (mRNA) forms, leaves the nucleus, and enters the cytosol. There, it directs synthesis of a new protein, often an enzyme, on the ribosomes.
The new proteins alter the cell’s activity and cause the responses typical of that hormone.
Most common stimulus
Endocrine organs are activated by other hormones
Example: Anterior pituitary hormones travel to target glands, such as the thyroid gland, to prompt the release of a particular hormone, such as thyroid hormone
Hormonal
The stimuli that activate endocrine glands fall into three major categories:
Hormonal
Humoral
Neural
Endocrine Gland Stimuli
Changing blood levels of certain ions and nutrients stimulate hormone release (Humoral indicates various body fluids, such as blood and bile)
Example:
Parathyroid hormone and calcitonin are produced in response to changing levels of blood calcium levels
Insulin is produced in response to changing levels of blood glucose levels
Humoral
Nerve impulses stimulate hormone release
Most are under the control of the sympathetic nervous system
Example: The release of norepinephrine and epinephrine by the adrenal medulla
Nerve impulses stimulate hormone release
Most are under the control of the sympathetic nervous system
Example: The release of norepinephrine and epinephrine by the adrenal medulla
secretes at least nine hormones; said to be described as a pea on a stalk; the stalk, infundibulum (pituitary stalk), connects the gland to the hypothalamus; has two major lobes
Pituitary gland (hypophysis)
composed largely of neural tissue such as pituicytes; releases neurohormones received ready-made from the hypothalamus; considered as a hormone-storage area and not a true endocrine gland that manufactures hormones
Posterior pituitary lobe (neurohypophysis)
composed of glandular tissue; manufactures and releases a number of hormones
Hormone release in the anterior pituitary gland is stimulated by releasing hormones and suppressed by inhibiting hormones from the hypothalamus
Anterior pituitary lobe (adenohypophysis)
Anterior Pituitary Gland Hormones (7)
Growth Hormone (Somatotropin)
Prolactin (PRL)’
Adrenocorticotropic Hormone (ACTH)
Thyrotropic Hormone (TH)
Follicle-Stimulating Hormone (FSH)
Luteinizing Hormone (LH)
Melanocyte-Stimulating Hormone (MSH)
Posterior Pituitary Gland Hormones (2)
Oxytocin
ADH (Antidiuretic Hormone or Vasopressin)
It is butterfly-shaped and is located just below the larynx (voice box), conjoined with the thyroid cartilage/adam’s apple
It is butterfly-shaped and is located just below the larynx (voice box), conjoined with the thyroid cartilage/adam’s apple; it secretes the thyroid hormones:
Hormone secreted by the thyroid Gland (3)
EXPLAIN
Thyroxine (T4 or tetraiodothyronine): contains four atoms of iodine
Triiodothyronine (T3): contains 3 atoms of iodine
Calcitonin: secreted by parafollicular cells
It is composed of right and left lateral lobes, one on either side of the trachea that are connected by an isthmus
Thyroid Gland
They regulate oxygen use and metabolic rate, cellular metabolism, and growth and development
Controls the rate of oxidation of glucose
Secretion is controlled by TRH from the hypothalamus and TSH from the anterior pituitary gland
Thyroid Hormones