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57 Cards in this Set

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What does the endocrine system do?
Acts as a means of internal communication, coordinating the activities of the organ systems.
What do endocrine glands produce?
Synthesis and secrete chemical substance called hormones directly into the circulatory system.
How are endocrine glands different than exocrine glands?
Endocrine goes directly into the blood stream.

Exocrine is released via ducts.
Name the glands that synthesize and/or secrete hormones:
pituitary
hypothalamus
thyroid
parathyroids
adrenals
pancreas
testes
ovaries
pineal
kidneys
gastrointestinal glands
heart
thymus
What determines the specificity of a hormone?
Specificity is determined by the presence of specific receptors on or in the target cells.
Where are the adrenal glands located and what are their names?
The adrenal glands are located on top of the kidneys.

Two Parts:
Adrenal Cortex
Adrenal Medulla
What does the adrenal cortex do?
In response to stress, ACTH (produced by anterior pituitary) stimulates the adrenal cortex to synthesize and secrete corticosteroids.
What are the different types of corticosteriods that are produced by the adrenal cortex?
Glucocorticoids
Mineralocorticoids
Cortical sex hormones
What are glucocorticoids?
Cortisol or Cortisone

Involved in glucose regulation and protein metabolism.

Glucocorticoids raise blood sugar levels by promoting protein breakdown and gluconeogenesis and decreasing protein synthesis.

Raise plasma glucose levels.

Antagonistic to effects of insulin.
What are mineralocorticoids?
Aldosterone

Regulate plasma levels of sodium and potassium, as a result, total extracellular water volume.

Causes active reabsorption of sodium and passive reabsorption of water in the nephron.

Results in increase in both blood volume and blood pressure.
What are cortical sex hormones?
Adrenal cortex secretes small quantities of androgens (male sex hormones)

Effects are limited in males due to a bulk of androgens produced in testes.

Woman may have excess facial hair however.
What does the Adrenal Medulla do?
Produces epinephrine (adrenaline) and norepinephrine (noradrenaline), both belonging to a class of amino acid-derived compounds called catecholamines.
What does epinephrine and norepinephrine do?
Epinephrine increases the conversion of glycogen to glucose in liver and muscle tissue, causing a rise in blood glucose levels and increase in basal metabolic rate.

Both epinephrine and norepinephrine increase rate and strength of heart beat, and dilate and constrict the blood vessels to increase blood flow to brain, heart, and skeletal muscles while decreasing flow to viscerals.

"fight or flight" response

Both hormones are also neurotransmitters.
How are the adrenal hormones controlled?
Release of adrenal cortical hormones is under the control of adrenocorticotrophic hormone (ACTH), hormone secreted by anterior pituitary gland.

ACTH stimulates production of glucocorticocoids and sex steroids; aldosterone production is controlled by a different mechanism.
Where is the pituitary gland located and what does it look like?
Small, tri-lobed gland lying at the base of the brain.

Two main lobes, anterior and posterior are functionally distint. The third intermediate lobe in humans is rudimentary.
What does the anterior pituitary gland synthesize?
Direct Hormones - Stimulate target organs
Tropic Hormones - Stimulate the release of other endocrine gland hormones.
What are the hormones produced by the anterior pituitary?
F SH
L H
A CTH
T SH

P rolactin
i (gnore)
G H
What are the Tropic hormones?
Follicle-stimulating hormone (FSH)
Luteinizing Hormones (LH)
Adrenocorticotropic hormone (ACTH)
Thyroid-Stimulating hormone (TSH)
What is Follicle-Stimulating Hormone?
Follicle-stimulating hormone (FSH) - In females causes maturation of ovarian follicles which begin secreting estrogen. In males, stimulates maturation of the seminiferous tubules and sperm production.
What are Lutenizing Hormones?
Luteinizing Hormones (LH) - In females, stimulate ovulation and formation of the corpus luteum. In males, stimultes the interstitial cells of tests to synthesize testosterone.
What is Adrenocorticotropic hormone (ACTH)?
Adrenocorticotropic hormone (ACTH) - Stimulates the adrenal cortex to synthesize and secrete glococorticoids and is regulated by the releasing hormone corticotrophin releasing factor (CRF).
What is Thyroid-Stimulating hormone (TSH)?
Thyroid-Stimulating hormone (TSH) - Stimulates the thyroid gland to synthesize and release thyroid hormone including thyroxin.
What does the posterior pituitary gland do?
Does not synthesize hormones.

Stores and releases peptide hormones oxytocin and ADH, both produced by hypothalamus.

Hormone secretion is stimulated by action potential from hypothalamus.
What does oxytocin do?
During childbirth, increases strength and frequency of uterine contractions.

Oxytocin secretion is also induced by suckling and stimulates milk production in mammary glands.
What does Antidiuretic Hormone (ADH, vasopressin) do?
Increases permeability of nephron's collecting duct to water, thereby promoting water reabsorption and increasing blood volume.

Secreted when plasma osmolarity increases, as sensed by hypothalamus; or when blood volume decreases, as sensed by circulatory system.
Where is the hypothalamus located and what does it do?
Part of forebrain and located directly above the pituitary gland.

Receives neural transmissions from brain and rest of body that triggers specific response of secretory cells.

Hypothalamus regulates pituitary glands via negative feedback and through the actions of inhibiting and releasing hormones.
How does the hypothalamus control the Anterior Pituitary?
Control occurs via portal vein that connects the two parts, communication is very quick this way.
How does the hypothalamus control the Posterior Pituitary?
Neurosecretory cells in the hypothalamus synthesis oxytocin and ADH and transport to posterior pituitary for storage and secretion.
Where is the thyroid located and what does it do?
Bi-lobed structure located on the ventral surface of the trachea.

It produces Thyroid Hormones (Thyroxine and Triiodothyronine) and calcitonin.
What do the thyroid hormones (Thyroxine and Triiodothyronine) do?
Thyroxine and Triiodothyronine are derived from the iodination of the amino acid Tyrosine.

Thyroid hormones are necessary for growth and neurological development in children.

They increase the rate of metabolism throughout the body.
What happens and is the result of hypothyroidism?
Thyroid hormones are undersecreted or not secreted at all.

Symptoms - Slowed heart rate and respiratory rate, fatigue, cold intolerance, weight gain.

In infants (cretinism) characterized by mental retardation and short stature.
What happens and is the result of hyperthyroidism?
Thyroid is overstimulated

Symptoms: increased metabolic rate, feelings of excessive warmth, profuse sweating, palpitations, weight loss, protruding eyes.
What does thyroid hormone calcitonin do?
Calcitonin decreases Ca2+ concentration by inhibiting release of Ca2+ from the bone.

Regulated by plasma Ca2+ levels.

Antagonistic to parathyroid hormone.
Where are the parathyroid glands located and what do they do?
Four small pea-shaped structures located on posterior side of Thyroid gland.

Synthesize and secrete parathyroid hormone (PTH).

PTH raises Ca2+ concentration in blood by breaking down bone.

Bone contains phosphate and calcium and PTH releases both.

PTH compensates by having kidney excrete phosphate.
Where is the Pancreas and what does it do?
Pancreas lies mid body horizontal (shaped like seven).

Pancreas is exocrine (cells secrete digestive enzymes to small intestine via ducts) and endocrine (smaller glandular structures called islets of Langerhans that secrete glucagon and insulin).
What does glucagon do?
Stimulates:
protein and fat degradation,
conversion of glycogen to glucose,
gluconeogenesis.

All serve to increase blood glucose levels.
What does insulin do?
Stimulates:
Uptake of glucose by cells and muscles,
storage of glycogen in muscle and liver cells,
synthesis of fats from glucose,
uptake of amino acids.

Antagonist to glucagon and glucocorticoids.

Underproduction of insulin leads to diabetes mellitus, hyperglycemia
Plasma Glucose in a Nutshell
Insulin decreases plasma glucose.
Glucagon increases plasma glucose.

Also, growth hormone, glucocorticoids, epinephrine are also capable of increasing plasma glucose
Ca2+ Levels in a Nutshell
PTH increases Ca2+
CalciTONIN tones down Ca2+
What do the kidneys do?
When blood volume falls, the kidneys produce renin, renin converts plasma protein angiotensinogen to angiotensin I which is converted to angiotensin II, which stimulates adrenal cortex to secrete aldosterone, which helps to restore blood volume by increasing sodium reabsorption at the kidney, leading to an increase in water.

Blood volume falls => kidneys produce renin -> renin converts angiotensinogen to angiotensin I -> angiotensin I converted to angiotensin II -> angiotensin II stimulates adrenal cortex to release aldosterone => increased sodium resorption -> increased water volume
What are the gastrointestinal hormones and what do they do?
Food stimulates the stomach to release the hormone gastrin.

Gastrin - carried to gastric glands and stimultes the gland to secrete HCl in response to food in stomach.

Secretin - Released by small intestine once food enters from stomach. Basic solution to neutralize the chyme from stomach.

Cholecystokinin - Released from small intestine in response to the presence of fats and causes contraction of the gallbladder and release of bile in small intestine. Bile aids in digestion of fats.
What does Bile do?
Aids the small intestine in the digestion of fats.
Where is the pineal gland located and what does it do?
Pineal gland is a tiny structure at the base of the brain that secretes the hormone melatonin.
What is the role of meletonin?
Believed to have a role in circadian rythems

Melatonin secretion is regulated by light and dark cycles of the environment
What two major groups are hormones classified in?
Peptide Hormones
Steroid Hormones
What two ways can hormones affect the activities of their target cells?
Via extracellular receptors, or

Via intracellular receptors
Peptide Hormones
Range from simple short peptides to complex polypeptides

Their binding to specific receptors on the surface of their target cells triggers a series of enzymatic reactions within each cell

Often results in cascade effect
Steroid Hormones
Lipid derived molecules with a characteristic ring structure

Produced by testes, ovaries, placenta, adrenal cortex

Because they are lipid soluble, enter the cell and directly bind with specific receptor proteins in the cytoplasm.

Receptor hormone can then directly enter the nucleus to affect the transcription of specific DNA and protein synthesis
What are plant hormones primarily involved in?
Plant hormones are primarily involved in the regulation of growth

Produced by actively growing portions of the plant such as meristematic tissues in apical region of shoots and roots, or in young, growing leaves, and developing seeds.
Auxins
Important class of plant hormones associated with several types of growth patterns

auxins stimulate the production of new xylem cells

Types:
Phototropism
Geotropism
Inhibition of lateral buds
What is phototropism?
Auxins are responsible for the tendency of shoots of plants to bend towards light sources.

When light strikes the tip of a plant from one side, the auxin supply on that side is REDUCED.

Illuminated side growth is reduced and grows more slowly than shaded side, thus plant bends toward light.
What is geotropism?
Growth of portions of plants towards or away from gravity.

Negative Geotropism - Causes shoots to grow upwards.

A plant placed on its side:
Lower side has increased concentration of auxins compared to top side. Plant growth is greater on bottom and plant will grow upward.

Positive Geotropism - Causes roots to grow towards gravity. Effect is opposite of negative geotropism with greater auxin resulting in lesser growth.
What are gibberellins?
Stimulate rapid stem elongation, particularly in plants that normally do not grow tall (dwarf plants).

Inhibit formation of new roots and stimulate production of new phloem cells by cambium (whereas auxins stimulate the production of new xylem cells)

Terminate the dormancy of seeds and buds.

Induce some biennial plants to flower during their first year of growth.
What are Kinins?
Promote cell division

Important type of cytokinin

Ratio of kinetin to auxin is of particular importance in the determination of the timing of the differentiation of new cells.

Action of kinetin is enhanced when auxin is present.
What does Ethylene do?
Stimulates fruit ripening.

Also induces senescence, or aging.
Plant Growth Inhibitors
Block cell division

Important in maintaining dormancy in buds and seeds of plants during autumn and winter.

Some destroyed by cold so they begin growing in the first growth season.
Anti-Auxins
Help regulate the activity of Auxins.

Increase in one results in the increase of the other.