BME350 - L23

What analogy is used to describe the function of the Endocrine System?

It functions like a wireless telephone network.

Compared to the nervous system, the endocrine system is relatively _____.

slow

What type of signals does the endocrine system use for communication?

Blood-borne chemical hormone signals.

List three major life processes regulated by the endocrine system.

Growth, development, and reproduction.

What is the primary role of the endocrine system in maintaining the body's internal state?

It contributes to homeostasis through the coordination and integration of bodily functions.

Name two stimuli that the endocrine system helps the body respond to.

Changes to cope with stress and the integration of circulation and digestion/absorption of nutrients. (Also acceptable: organic metabolism, H2O/electrolyte balance, RBC formation).

Endocrine glands are described as _____ glands, meaning they secrete hormones directly into the bloodstream.

ductless

How does an exocrine gland secrete its substance?

It secretes its substance onto a surface, usually through a duct.

How does an endocrine gland secrete its substance?

It secretes its substance directly into the bloodstream.

What type of signaling involves hormones acting on cells of distant target organs via the bloodstream?

Endocrine hormone signaling.

In neuroendocrine signaling, where does the neurohormone originate?

The neurohormone originates in a neuron.

What is the mode of transport for a signal in neuroendocrine signaling?

The signal is transported via the axon into the bloodstream.

What is the term for agents that are secreted locally and act on neighboring cells?

Paracrine agents.

What is the term for peptides that are secreted locally and act on the same cells that synthesized them?

Autocrine peptides.

Steroid hormones are synthesized from what precursor molecule?

Cholesterol.

How are steroid hormones typically transported in the blood?

They bind to plasma carrier proteins.

Where do steroid hormones typically bind to initiate biological responses in target cells?

They bind to intracellular receptors or proteins.

Peptide hormones are synthesized from larger _____.

precursor molecules

How do peptide hormones travel in the blood plasma?

They dissolve directly in the plasma for transport.

Where on a target cell do peptide hormones typically bind?

They bind to cell surface receptors, which are integral membrane proteins.

Binding of a peptide hormone to its receptor activates intracellular _____ signaling cascades.

2nd messenger

What is the precursor molecule for insulin?

Proinsulin.

What is the general relationship between plasma hormone concentration and endocrine response?

Increasing plasma concentrations of a hormone contribute to an increased endocrine response.

In hormone signaling, what is the dose-response relationship?

The magnitude of the response is correlated with the hormone concentration.

What is the definition of 'sensitivity' in the context of hormone action?

It is the hormone concentration that produces 50% of the maximal response.

List three factors that can influence an organism's sensitivity to a hormone.

Receptor number, receptor affinity, and hormone half-life. (Also acceptable: competitive antagonists).

Maximal hormonal response is produced by _____ concentrations of the hormone.

saturating

List three factors that can determine the maximal effectiveness of a hormone.

The number of target cells, the number of receptors, and the concentration of target enzymes. (Also acceptable: non-competitive antagonists).

What is the purpose of receptor up-regulation?

To increase the sensitivity of the target tissue when hormone levels are low for an extended period.

What are the three mechanisms of receptor up-regulation?

Increase the synthesis of new receptors, decrease the degradation of existing receptors, and activate receptors.

Term: Antagonism (Hormonal Effect)

One hormone causes reduced availability of another hormone's receptors, leading to reduced effectiveness of the second hormone.

Term: Synergism (Hormonal Effect)

The combined effect of several complimentary hormones is greater than the sum of their individual effects.

Term: Permissiveness (Hormonal Effect)

One hormone must be present in adequate amounts for the full exertion of another hormone's effect.

What is the synergistic effect of glucagon, cortisol, and epinephrine when combined?

They synergistically elevate blood glucose levels.

What is the result of endocrine dysfunction characterized by insufficient hormone secretion?

Hyposecretion.

What is the result of endocrine dysfunction characterized by excessive hormone secretion?

Hypersecretion.

What are the three primary glands of the central endocrine system?

The pineal gland, the hypothalamus, and the pituitary gland.

The pineal gland secretes melatonin, which is also known as the 'hormone of _____.'

darkness

What is the function of the pineal gland regarding the body's daily cycle?

It helps keep the body's circadian rhythms in synchrony with the light-dark cycle.

Besides circadian rhythms, list two other functions of the pineal gland.

It influences reproductive activity, acts as an antioxidant, enhances immunity, and promotes sleep.

Which brain structure is most involved in directly regulating the body's internal environment?

The hypothalamus.

How does the hypothalamus control the pituitary gland?

It directs changes via chemical neurotransmitter signals to the pituitary gland, controlling its hormone release.

List four functions controlled by the hypothalamus.

Body temperature, thirst and urine output, food intake, and anterior pituitary hormone secretion. (Many others acceptable).

The pituitary gland consists of two lobes; the anterior pituitary is made of _____ tissue.

glandular epithelial

The pituitary gland consists of two lobes; the posterior pituitary is made of _____ tissue.

nervous

Does the posterior pituitary produce its own hormones?

No, it does not produce any hormones; it only stores and releases them.

What are the two peptide hormones released from the posterior pituitary?

Vasopressin (ADH) and oxytocin.

What is the primary function of vasopressin, also known as ADH?

It conserves water during urine formation.

What are the two primary functions of oxytocin?

It stimulates uterine contraction during childbirth and milk ejection during breast-feeding.

Where are vasopressin and oxytocin synthesized?

They are synthesized in special neuronal cell bodies located in hypothalamic nuclei.

Most hormones secreted by the anterior pituitary are known as _____ hormones.

trophic

What does it mean for a hormone to be 'trophic'?

It means other endocrine glands are the targets for these hormones.

What is the function of the Hypothalamic-Hypophyseal Portal System?

It is a unique blood system for hypothalamic hormones to travel to the anterior pituitary.

In complex endocrine reflexes involving the hypothalamic-pituitary axis, what serves as the negative feedback signal?

The hormones themselves provide the negative feedback signal.

What is the most important mechanism for regulating hormone secretion?

Negative feedback.

How does positive feedback affect hormone secretion?

It results in greater hormone secretion and is self-augmenting.

Fetal growth is largely promoted by hormones from what organ?

The placenta.

Post-natal body growth primarily depends on which hormone?

Growth hormone (GH).

Name three factors, besides GH, that influence post-natal growth.

Genetic determination, adequate diet, and normal levels of other growth-influencing hormones (e.g., thyroid, insulin).

Growth Hormone (GH) is what type of hormone secreted by the anterior pituitary?

It is an anabolic protein that acts as a trophic hormone.

How does Growth Hormone (GH) primarily promote growth?

It promotes growth indirectly by stimulating the liver to produce insulin-like growth factors (IGFs).

What are the growth-promoting actions of insulin-like growth factors (IGFs)?

They act directly on bone and soft tissues, stimulating protein synthesis, cell division, and bone lengthening/thickening.

What is a metabolic effect of Growth Hormone (GH) on adipose tissue?

It increases fatty acid levels in the blood by enhancing the breakdown of triglyceride fat.

How does Growth Hormone (GH) affect blood glucose levels?

It increases blood glucose levels by decreasing glucose uptake by muscles.

What are the two hypothalamic hormones that regulate the secretion of Growth Hormone (GH)?

Growth hormone-releasing hormone (GHRH) and growth hormone-inhibiting hormone (GHIH).

What condition can be caused by hyposecretion of GH in children?

Dwarfism.

What is the general cause of Growth Hormone (GH) excess?

It is generally caused by a tumor of GH-producing cells in the anterior pituitary.

What condition results from the overproduction of GH in childhood, before the long bone growth plates close?

Gigantism.

What condition results from GH hypersecretion that occurs after adolescence?

Acromegaly.