Chapter 17 Endocrine

Term: Endocrinology

The scientific study of hormones and the endocrine organs.

Term: Hormone

A mediator molecule released in one part of the body that regulates activity in other parts.

How do exocrine glands release their secretions?

They secrete products into ducts that carry them into body cavities, organ lumens, or the body surface.

Give three examples of secretions released by exocrine glands.

Sweat, oil, and mucous.

Where do endocrine glands secrete their products (hormones) initially?

Into the interstitial fluid surrounding the secretory cells.

How do hormones reach their target tissues after entering the interstitial fluid?

They diffuse into the bloodstream, which carries them throughout the body.

What is the primary mediator molecule used by the nervous system?

Neurotransmitters.

What is the primary mediator molecule used by the endocrine system?

Hormones.

whats different in the site of action between the nervous and endocrine systems.

The nervous system acts locally at a synapse, while the endocrine system acts at distant target cells.

Which system typically has a faster 'time to action': nervous or endocrine?

The nervous system (within milliseconds).

Compare the 'duration of action' between the nervous and endocrine systems.

The nervous system's action is brief, whereas the endocrine system's action lasts seconds to days.

What are the four general functions of the endocrine system?

Regulating growth/metabolism, maintaining blood homeostasis, controlling digestion, and controlling reproduction.

List the five 'pure' endocrine glands.

Pineal, pituitary, thyroid, parathyroid, and adrenal glands.

Name three organs that are not strictly endocrine glands but contain hormone-secreting cells.

Hypothalamus, pancreas, and ovaries (or testes/thymus/heart/stomach).

Hormone release is regulated by _____ to stimuli.

reflexes

Define hormonal stimulation of hormone release.

A gland cell releases its hormone in response to another hormone binding to it.

Define humoral stimulation of hormone release.

A gland cell releases its hormone in response to changes in blood levels of a nutrient or ion.

Define nervous stimulation of hormone release.

A gland cell releases its hormone in response to stimulation by a neuron.

An example of _____ stimulation is when TSH binds to the thyroid gland to trigger the release of thyroid hormone.

hormonal

An example of _____ stimulation is when high blood glucose levels trigger the pancreas to release insulin.

humoral

An example of _____ stimulation is when sympathetic preganglionic axons trigger the adrenal medulla to release epinephrine.

nervous

What characterizes circulating hormones compared to local hormones?

They enter the bloodstream to act on distant target tissues.

How are circulating hormones eventually removed from the body?

They are inactivated by the liver and excreted by the kidneys.

Define paracrine hormones.

Local hormones that act on neighboring cells without entering the bloodstream.

Define autocrine hormones.

Local hormones that act on the same cell that secreted them.

How long do local hormones typically last compared to circulating hormones?

They inactivate very quickly.

What is the primary requirement for a hormone to affect a specific cell?

The cell must have specific receptors for that hormone.

Approximately how many specific receptors does a typical target cell have for a single hormone?

2,000 to 100,000.

A decrease in the number of receptors when a hormone is present in excess, making the cell less sensitive.

Define down-regulation in target cells.

Define up-regulation in target cells.

An increase in the number of receptors when hormone levels are low, making the cell more sensitive.

What are three factors that determine how a target cell responds to a hormone?

Hormone concentration, abundance of receptors, and influences from other hormones.

Define the permissive effect of hormone interaction.

A second hormone is required to strengthen the effect of the first hormone.

Define the synergistic effect of hormone interaction.

Two hormones acting together produce a much stronger effect than the sum of their individual effects.

Define the antagonistic effect of hormone interaction.

One hormone opposes the action of another hormone.

Most hormone regulatory systems work via a _____ feedback system.

negative

Which hormone's release during childbirth is an example of a positive feedback system?

Oxytocin.

Where is the hypothalamus located?

Below the thalamus.

The hypothalamus is considered the 'true master' because it links which two systems?

The nervous system and the endocrine system.

The pituitary gland is also known as the _____.

hypophysis

In which bone's structure is the pituitary gland located?

The Sella Turcica of the sphenoid bone.

What is the stalk-like structure that connects the pituitary gland to the hypothalamus?

The infundibulum.

The anterior lobe of the pituitary gland is also called the _____.

adenohypophysis

The posterior lobe of the pituitary gland is also called the _____.

neurohypophysis

No, it only stores and releases hormones produced by the hypothalamus.

Does the posterior pituitary synthesize its own hormones?

Which two hormones are stored and released by the posterior pituitary?

Antidiuretic hormone (ADH) and oxytocin.

What are the two primary triggers for the release of ADH?

A rise in blood electrolyte concentration or a fall in blood volume/pressure.

What is the primary function of ADH in the kidneys?

It decreases the amount of water lost by the kidneys (water retention).

How does alcohol consumption affect ADH levels?

Alcohol blocks the production of ADH, leading to increased urine output.

What are the two primary functions of oxytocin in females?

Stimulating uterine smooth muscle contraction during childbirth and triggering milk ejection from mammary glands.

What is the function of oxytocin in males?

It stimulates smooth muscle contraction in the prostate gland, which is important for ejaculation.

What system carries regulatory hormones from the hypothalamus directly to the anterior pituitary?

The hypophyseal portal system.

Define 'tropins' (tropic hormones).

Pituitary hormones that 'turn on' or stimulate other endocrine glands.

What are the three names for the hormone that stimulates general body growth?

Growth hormone (GH), Human growth hormone (HGH), or somatotropin.

Which anterior pituitary hormone controls the synthesis and secretions of $T_3$ and $T_4$?

Thyroid stimulating hormone (TSH).

What is the function of Follicle stimulating hormone (FSH) in women?

It promotes egg development and stimulates estrogen secretion.

What is the function of FSH in men?

It supports sperm production in the testes.

What are the functions of Luteinizing hormone (LH) in women?

It induces ovulation and promotes the secretion of estrogens and progesterone.

What is the function of Luteinizing Hormone (LH) in men?

It stimulates the testes to produce androgens, specifically testosterone.

Which gland produces Melatonin?

The pineal gland.

What is the primary function of Melatonin?

It helps regulate the body's circadian rhythms (biological clock).

Which hormone is produced by the parathyroid glands to increase blood calcium levels?

Parathyroid hormone (PTH).

What is the function of Thymosin produced by the thymus?

It promotes the maturation of T-lymphocytes (white blood cells).

Which region of the adrenal gland produces Mineralocorticoids like aldosterone?

The adrenal cortex.

What is the primary function of aldosterone?

Regulating blood $Na^+$ and $K^+$ levels by decreasing $Na^+$ and increasing $K^+$ excretion in urine.

Glucocorticoids like cortisol participate in the _____ response and increase nutrient availability in the blood.

stress

Which part of the adrenal gland produces Epinephrine (EPI) and Norepinephrine (NE)?

The adrenal medulla.

Epinephrine (EPI) and norepinephrine (NE) prolong the effects of which division of the autonomic nervous system?

The sympathetic division.

What are the two primary hormones produced by the pancreas to regulate blood glucose?

Insulin and glucagon.

Does insulin increase or decrease blood glucose levels?

It decreases blood glucose levels.

Does glucagon increase or decrease blood glucose levels?

It increases blood glucose levels.

Which hormone, produced by both testes and ovaries, inhibits the release of FSH?

Inhibin.

What hormone is produced by the heart to decrease blood pressure?

Atrial natriuretic peptide (ANP).

Which hormone produced by the kidneys increases the production of red blood cells?

Erythropoietin (EPO).

Which hormone produced by the skin is a precursor to calcitriol and aids calcium absorption?

Vitamin $D_3$.

Which hormone produced by adipose connective tissue helps regulate food intake?

Leptin.