Endocrine System: Hormones, Glands, and Regulation Mechanisms

What are the two main control systems of the body?

The nervous system and the endocrine system.

How do hormones function in the body?

Hormones are chemical messengers produced by ductless glands that travel through the bloodstream to target cells, influencing cell metabolism and function.

What is the primary role of the endocrine system?

To help maintain homeostasis under negative feedback control.

What is the difference between autocrine and paracrine signaling?

Autocrine signaling affects the same cell type, while paracrine signaling affects nearby cells.

What are the two types of glands in the endocrine system?

Endocrine glands (ductless) and exocrine glands (have ducts).

What is a tropic hormone?

A hormone that stimulates other glands to release their hormones.

What is the time course for the nervous system compared to the endocrine system?

Nervous system responses are measured in milliseconds/seconds, while endocrine system responses can take minutes/days.

What are the types of intracellular messengers?

Neurotransmitters, hormones, neurohormones, neuromodulators, paracrines, autocrines, and pheromones.

What are the three chemical natures of hormones?

Proteins, steroid derivatives, and amino acid derivatives.

What factors can affect hormone secretion?

Metabolites, the nervous system, and other hormones (tropic).

How do hormones travel in the bloodstream?

Hormones can be free or bound to plasma proteins.

What is the half-life of a hormone?

The length of time it takes for half of a dose of a substance to be eliminated from the circulatory system.

What must hormones do once they arrive at target cells?

They must bind to receptors on the cell membrane or pass through the cell membrane.

What is the role of the endocrine system in metabolism?

It regulates metabolism and tissue maturation, affecting the rate of nutrient utilization and energy production.

What is the significance of negative feedback in the endocrine system?

Negative feedback helps maintain homeostasis by regulating hormone levels.

What is the difference between endocrine and exocrine glands?

Endocrine glands release hormones directly into the bloodstream, while exocrine glands release substances through ducts.

What is the role of target cells in the endocrine system?

Target cells are the specific cells that hormones affect, binding to hormone receptors to elicit a response.

What is the function of neurohormones?

Neurohormones are hormones released from neurons that act on distant target cells.

What is the impact of hormones on cell metabolism?

Hormones influence all aspects of cell metabolism and function.

What is the primary function of the hypothalamus in the endocrine system?

The hypothalamus regulates the release of hormones from the pituitary gland and coordinates the endocrine system.

What is the primary function of the hypothalamus?

To act as a bridge between the nervous system and the endocrine system, maintaining homeostasis.

What hormones are produced by the hypothalamus?

Antidiuretic hormone (ADH) and oxytocin.

What is the role of the anterior pituitary?

It is known as the 'master gland' and produces hormones that regulate various body functions and other endocrine glands.

What are the main hormones secreted by the anterior pituitary?

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

What is the posterior pituitary also known as?

Neurohypophysis.

How does the posterior pituitary function?

It releases hormones (ADH and oxytocin) that are produced in the hypothalamus.

What is the function of calcitonin?

To stabilize osteoclast activity and increase osteoblast activity, lowering blood calcium levels.

What is the role of T3 and T4 hormones?

They regulate metabolic rate and are involved in protein synthesis and ATP production.

What condition results from a lack of thyroid hormone in children?

Cretinism.

What is myxedema?

A condition caused by hypothyroidism in adults.

What is Graves's disease?

A condition resulting from hypersecretion of thyroid hormones, leading to goiter.

What is the difference between down regulation and up regulation of hormone receptors?

Down regulation decreases receptor sensitivity by removing receptors, while up regulation increases sensitivity by increasing receptor numbers.

How are hormones removed from circulation?

Through excretion by the kidneys or liver, and metabolism by enzymes.

What are membrane-bound receptors?

Receptors for protein hormones that interact with hormones that cannot pass through the plasma membrane.

What is the role of second messengers in hormone action?

They are produced in response to the binding of a hormone to a receptor and facilitate rapid cellular responses.

What is the significance of the infundibulum?

It connects the hypothalamus to the posterior pituitary.

What is the function of neurosecretory cells?

They produce hormones that are released into the bloodstream from the hypothalamus.

What is the role of TRH in the endocrine system?

Thyrotropin-releasing hormone (TRH) stimulates the release of TSH from the anterior pituitary.

What is the primary effect of T3/T4 on the body?

To increase metabolic rate and act as a synergist for growth hormone (GH).

What is the relationship between T3 and T4?

T4 is converted to T3, which is the more potent hormone at target cells.

What is the function of the anterior pituitary's tropic hormones?

They regulate the activity of other endocrine glands.

What is the role of the thyroid gland in the endocrine system?

To produce T3 and T4 hormones that regulate metabolism and body temperature.

What is the role of G proteins in hormone signaling?

G proteins amplify signals by opening calcium channels and producing second messengers like cAMP and cGMP.

What happens when epinephrine binds to β-adrenergic receptors in the heart?

It increases calcium permeability, leading to a rise in intracellular calcium levels and enhanced cardiac contractions.

How does glucagon affect liver cells?

Glucagon binds to liver cell membranes, activating adenylyl cyclase to increase cAMP levels, which activates glycogenolysis.

What are DAG and IP3, and what is their role in smooth muscle contraction?

DAG (diacylglycerol) and IP3 (inositol triphosphate) are produced by G protein activation, leading to calcium release from the endoplasmic reticulum and smooth muscle contraction.

What distinguishes intracellular receptors from membrane-bound receptors?

Intracellular receptors are located within the cell and bind to lipid-soluble hormones that can cross the cell membrane.

What is the latent period in hormonal signaling?

The latent period is the time it takes for a hormone to bind to its receptor and initiate a response, which can take minutes to days.

What is the function of oxytocin in breastfeeding?

Oxytocin is released in response to the baby's sucking, stimulating mammary glands to secrete milk.

What triggers the release of ADH (antidiuretic hormone)?

ADH is released in response to increased osmolarity and blood pressure changes.

What is diabetes insipidus and its relation to ADH?

Diabetes insipidus is caused by a lack of ADH production, leading to excessive urine output and decreased blood volume.

How does alcohol affect ADH production?

Alcohol inhibits ADH production, leading to increased urine output and potential dehydration.

What are the effects of growth hormone (GH) on the body?

GH stimulates growth in tissues, promotes protein synthesis, and aids in fat breakdown while sparing glucose usage.

What is the result of GH hyposecretion in children?

Hyposecretion of GH in children can lead to dwarfism, characterized by short stature and normal body proportions.

What condition results from hypersecretion of GH during childhood?

Hypersecretion of GH during childhood leads to gigantism, characterized by excessive growth.

What is acromegaly?

Acromegaly is caused by hypersecretion of GH in adulthood, resulting in enlarged bones and tissues.

What is the role of GHRH and GHIH in growth hormone regulation?

GHRH stimulates GH release, while GHIH inhibits it, helping to regulate growth hormone levels.

What is the function of prolactin?

Prolactin stimulates milk production in mammary glands.

What hormones are produced by the anterior pituitary?

The anterior pituitary produces GH, prolactin, LH, FSH, TSH, ACTH, and MSH.

What is the role of osmoreceptors in hormone regulation?

Osmoreceptors detect changes in osmolarity and trigger the release of hormones like ADH to regulate water balance.

How does stress affect growth hormone levels?

Stress can increase GH levels, which may contribute to the body's response to stress and exercise.