Endocrine System

What do the endocrine and nervous systems do?

Work in tandem to control and coordinate the functions of the animal body

What is homeostasis?

balance is maintained by chemical messengers that tell the body how to respond to changes in internal and external conditions.

What are the 8 organs of the endocrine system?

pituitary, thyroid, parathyroid, adrenals, endocrine pancreas, kidney, GI tract, and reproductive organs.

What do endocrine glands do?

Secrete hormones

What are hormones and what do they do?

Non-neuronal chemical messengers that meet up with targets near or far to coordinate organ and tissue functions.

Where do the hormones secreted by the endocrine glands go?

Directly into the bloodstream

What is the general function of the endocrine system?

Regulation of body functions to maintain homeostasis

What is the general function of the nervous system?

Regulation of body functions to maintain homeostasis

What is the endocrine systems reaction to stimuli?

slow

What is the nervous systems reaction to stimuli?

fast

What is the endocrine systems duration of effects?

Long

What is the nervous systems duration of effects?

short

What is the endocrine systems target tissues?

Virtually all body cells and tissues

What is the nervous systems target tissues?

Muscle and glandular tissue

What is the endocrine systems chemical messengers?

hormones

What is the nervous systems chemical messengers?

Neurotransmitters

What is the endocrine systems messenger producing cells?

Endocrine gland cells or modified neurons

What is the nervous systems messenger producing cells?

neurons

What is the endocrine systems distance from chemical message?

Long (via bloodstream) production to target

What is the nervous systems distance from chemical message?

Short - across synaptic space

What are the 3 divisions of hormones?

monoamine, peptide, and steroid hormones

Where are monoamine hormones derived from?

Amino acids

What are 2 monoamine hormones?>

catecholamines & thyroid hormones

Where are catecholamines receptors found?

Cell membrane

Are catecholamines hydrophilic or hydrophobic?

hydrophilic ( transported dissolved in plasma)

Where are the receptors located for thyroid hormones?

Nucleus

Are thyroid hormones hydrophilic or hydrophobic?

hydrophobic ( require transport proteins)

Peptide hormones are in….?

chains of a few up to 200 amino acids (pearls on a necklace)

Are peptide hormones hydrophilic or hydrophobic?

Hydrophilic (transported dissolved in plasma)

Where are the receptors for peptide hormones located?

cell membrane of target cells

Steroid hormones are…?

Lipids synthesized from cholesterol

Are steroid hormones hydrophilic or hydrophobic?

Hydrophobic – hydrophilic transport proteins required (bound)

What are the 2 forms of steroid hormones?

bound and free

Bound form

portion attached to transport molecule

Free form

portion not attached to transport molecule; can leave and enter the blood stream

Where are steroid receptors located within the cell?

cytoplasm and nucleus

What are the hypothalamus Important autonomic controls?

Appetite, body temperature, sleep-wake cycles

What does the hypothalamus serve as?

A bridge between the higher centers in the cerebral cortex and lower brain centers as well as the endocrine system

Where is the pituitary gland located?

Ventral to the hypothalamus and is attached to it by a slender stalk

What is the pituitary gland also known as?

Hypophysis, Master endocrine gland

Where does the pituitary gland sit?

In a small pocket created by a depression in the sphenoid bone of the skull (pituitary fossa)

What are the 2 ways control by the brain happens?

Portal system links hypothalamus to the anterior pituitary, or Modified neurons in the hypothalamus produce ADH and Oxytocin.

What happens during brain control?

Transported down axons to the posterior pituitary, and Stored and released when nerve impulses from hypothalamus arrive

How does the anterior pituitary develop?

From glandular tissue

What hormones does the anterior pituitary produce?

TSH, ACTH, GH, prolactin, MSH, FSH, and LH

TSH

thyroid stimulating hormone

ACTH

Adrenocorticotropic hormone

GH

growth hormone

MSH

Melanocyte stimulating hormone

FSH

Follicle stimulating hormone

LH

Luteinizing hormone

What does the thyroid stimulating hormone do?

Stimulates growth and development of the thyroid gland and production of hormones T3 and T4

What does the Adrenocorticotropic Hormone do?

Stimulates the growth and development of the adrenal cortex and the release of some of its hormones

What regulates production of Adrenocorticotropic Hormone?

By feedback from hormones of the adrenal cortex (cortex = glandular tissue)

What does the growth hormone do?

promotes growth, regulates metabolism, encourages synthesis, drives up blood sugar, encourages lipid metabolism

What does prolactin do?

Helps trigger and maintain lactation

What does melanocyte stimulating hormone do?

Associated with control of color changes in pigment cells of reptiles, fish, and amphibians – animals that can rapidly change colors

What is melanocyte stimulating hormone considered to be?

A type of chromatophore

What does follicle stimulating hormone do in the female?

Stimulates the growth and development of follicles in the ovaries (oogenesis), and the lining cells of the follicles to produce and secrete estrogens

What does follicle stimulating hormone do in the male?

Stimulates spermatogenesis in the testes

What does luteinizing hormone do in the female?

Completes the process of follicle development in the ovary started by FSH, Once the follicle ruptures, high LH levels stimulate development of the corpus luteum which produces progesterone

What does progesterone promote?

Gestation

What does luteinizing hormone do in the male?

Stimulates interstitial cells in the testes to develop and produce testosterone

What does the posterior pituitary gland develop from and is involved in?

Develops from neural tissue and is involved in the storage and release of two hormones

What are the 2 hormones the posterior pituitary gland is involved in releasing?

oxytocin and antidiuretic hormone

What are the 2 targets of oxytocin in the female?

uterus and mammary glands

What does oxytocin cause during breeding?

contraction of the myometrium that aid in the transport of spermatozoa up to the oviducts

What does oxytocin cause during parturition?

contractions aid in expulsion of the fetus and placenta

What does oxytocin cause in the mammary glands?

Causes milk ”let down”

What does the antidiuretic hormone do?

Prevents diuresis and helps conserve water

What is diuresis?

Producing and passing large quantities of water in the urine

What can a deficiency of the antidiuretic hormone cause?

Diabetes Insipidus

What does the thyroid gland consist of on either side of the larynx?

two lobes

What is the thyroid gland microscopically composed of?

 Follicles where thyroid hormone is produced

What does the thyroid gland have?

“Cruise control” like mechanism for overall body metabolic rate

What 2 hormones does the thyroid gland produce?

thyroid hormone and calcitonin

How is thyroid hormone produced?

Produced when TSH from the anterior pituitary stimulates the thyroid gland

What are the actual 2 hormones of the thyroid hormones?

T4 (tetraiodothyronine) the prohormone, and T3 (triiodothyronine) the active hormone

T4

tetraiodothyronine

T3

triiodothyronine

What does the thyroid hormone produce more of?

T4

What is the more biologically active form of thyroid hormone?

T3

Where are parathyroid glands located?

In, on, or near the thyroid gland depending on species (much variation)

What does the parathyroid gland produce?

Parathyroid hormone

What does the parathyroid hormone do?

controls calcium reabsorption by the kidney – causing serum calcium to rise

What controls parathyroid hormone secretion?

Blood calcium levels

What is an example of negative feedback?

If Serum calcium is LOW – PTH will be secreted from the Parathyroid, the kidneys will absorb Calcium back into the bloodstream – causing serum Calcium levels to rise. When levels return to normal – Parathyroid hormone is no longer secreted and no more calcium is added to the bloodstream. 

What has the opposite effect of parathyroid hormones?

Calcitonin

What does Calcitonin do?

Lower calcium levels

When is Calcitonin released?

released when serum calcium levels are too high to prevent hypercalcemia

What activity does Calcitonin decrease?

osteoclast activity

What does Calcitonin also facilitate?

deposition of calcium and phosphorus into bone (where it is stored)

Where is the pancreas located?

 in the cranial abdomen.

What is the right lobe of the pancreas associated with?

descending duodenum

What is the left lobe of the pancreas associated with?

the stomach

The endocrine portion of the pancreas only makes up….?

a small percentage of the organ.

The endocrine pancreas is organized into….?

 thousands of tiny clumps of cells scattered throughout the organ.

What are the clumps of cells scattered throughout the pancreas called?

Pancreatic islets or Islets of Langerhans

What do alpha cells of the pancreas do?

secrete glucagon

What do beta cells of the pancreas do?

secrete insulin