Endocrine System

Questions and Answers

What is the primary function of the endocrine system?

To produce antibodies to fight infections

To transmit nerve impulses throughout the body

To release hormones into circulation for travel to and action on distant targets (correct)

To filter waste and excess fluids from the blood

What type of hormone is adrenocorticotropic hormone (ACTH)?

Steroid hormone

Vitamin-derived hormone

Modified amino acid hormone

Protein/Polypeptide hormone (correct)

What is the function of oxytocin?

To stimulate the release of hormones from the adrenal cortex

To stimulate the release of insulin from the pancreas

To stimulate urine contraction and milk let-down (correct)

To regulate blood pressure

Which gland is responsible for regulating certain metabolic processes and other activities of the autonomic nervous system?

Hypothalamus Signup and view all the answers

What is the function of parathyroid hormone?

To promote an increase in plasma calcium and reduction in plasma phosphate Signup and view all the answers

What type of feedback involves a response that is the reverse of the change detected?

Negative feedback Signup and view all the answers

What is the primary function of the adenohypophysis?

To receive and release hormones through a process involving releasing factors Signup and view all the answers

What is the function of glucocorticoids?

To play essential roles in protein and carbohydrate metabolism Signup and view all the answers

What is the function of antidiuretic hormone (ADH)?

To conserve water and reduce urine volume in the kidneys Signup and view all the answers

What is the primary function of the thyroid gland?

To produce thyroid hormones that regulate metabolic rate Signup and view all the answers

Study Notes

Endocrine System

Encompasses a group of tissues that release hormones into circulation for travel to and action on distant targets.
Endocrine tissue is typically a ductless gland that releases its hormones into capillaries that permeate the tissue.

Hormones

Control or regulate a multitude of biologic processes in virtually all tissues.
Three major classes of hormones:
- Protein/Polypeptide Hormones: act on their target cells by binding to receptors located on the cell surface.
  - Examples: adrenocorticotropic hormone (ACTH) from the pituitary, insulin from the pancreas, and parathyroid hormone (PTH).
- Steroid Hormones: derivatives of cholesterol, including products of the adrenal cortex, ovaries, and testes, as well as vitamin D.
  - Synthesized from cholesterol by enzymatic reactions and stored intracellularly in the tissue of origin.
- Modified Amino Acid Hormones: made by chemical modification of amino acids, mainly tyrosine.

Organs

Hypothalamus

Links the nervous system to the endocrine system via the pituitary gland.
Regulates certain metabolic processes and activities of the autonomic nervous system.

Pituitary Gland

Under adenohypophysis:
- Inhibiting hormone (IH) restrains pituitary hormone.
- Releasing hormone (RH) stimulates pituitary hormone.
Under neurohypophysis:
- Oxytocin stimulates urine contraction, milk let-down for the uterus and mammary gland.
- Antidiuretic hormone (ADH) releases vasopressin, conserves water, reduces urine volume in kidneys, and constricts vessels to raise blood pressure in arterioles.

Adrenal Gland

Under adrenal cortex:
- Glucocorticoids are essential for normal response to stress, play important roles in protein and carbohydrate metabolism in multiple organs, including the liver.
- Mineralocorticoids (aldosterone) conserve Na, eliminate K in the kidney.
Under adrenal medulla:
- Epinephrine and Norepinephrine augment the sympathetic response to stress by actions on several organs.

Thyroid

Thyroid follicular cells produce thyroid hormone.

Parathyroid

Parathyroid hormone promotes an increase in plasma calcium and a reduction in plasma phosphate in bones and kidneys.

Processes

Feedbacks

Negative Feedback: involves a response that is the reverse of the change detected, reducing the change.
Positive Feedback: involves a response that reinforces the change detected, amplifying the change.
Steps of feedback:
1. Detect change in body homeostasis.
2. Produce change in variable.
3. Detected by receptor (sensor).
4. Information sent along afferent/internal pathway to control center.
5. Information sent along efferent/external pathway to effector.
6. Response of effector feeds back to influence magnitude of stimulus, returning variable to homeostasis.