Endocrine System Overview

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Questions and Answers

Which of the following best describes the function of an endocrine gland?

They have both endocrine and exocrine functions.

They secrete hormones through ducts.

They only secrete hormones in response to nervous stimulation.

They release hormones directly into the bloodstream. (correct)

What role does the hypothalamus play in the endocrine system?

It regulates the secretion of digestive hormones.

It secretes hormones that directly act on target organs.

It connects the nervous system and the endocrine system. (correct)

It acts as a primary endocrine gland independent of the pituitary.

How do neurohormones from the hypothalamus primarily reach the anterior pituitary?

Through ducts leading directly to the pituitary.

Through specialized portal vascular system. (correct)

By neural impulses transmitted through the spinal cord.

Via general circulation in the bloodstream.

What type of feedback loop is primarily responsible for regulating hormone levels in the endocrine system?

Negative feedback loops that inhibit hormone production. Signup and view all the answers

Which of the following glands is NOT part of the endocrine system?

Salivary gland Signup and view all the answers

What primarily controls the neurosecretory cells of the hypothalamus?

Stimuli from brain areas, hormones, and feedback loops. Signup and view all the answers

What is the function of the hypothalamo-hypophysial tract?

To serve as a nervous connection between the hypothalamus and the posterior pituitary. Signup and view all the answers

What is the role of short feedback loops in the endocrine system?

They provide feedback from anterior pituitary hormones to hypothalamic control. Signup and view all the answers

What is the primary role of growth hormone in the body?

Proliferation of epiphyseal cartilage leading to bone growth Signup and view all the answers

Which hormone is responsible for the regulation of thyroid gland activity?

Thyroid stimulating hormone (TSH) Signup and view all the answers

Which hormone acts as the primary inhibiting factor for prolactin secretion?

Dopamine Signup and view all the answers

What type of hormones do the gonadotropic hormones primarily influence in females?

Maturation of ova and synthesis of female sex hormones Signup and view all the answers

In addition to stimulating bone growth, what other key effect does growth hormone have on metabolism?

Increased protein synthesis Signup and view all the answers

What is the method of action of growth hormone involving IGF-I?

Production of insulin-like growth factor by the liver Signup and view all the answers

How does adrenocorticotropic hormone (ACTH) primarily function within the endocrine system?

Stimulates secretion of adrenal gland hormones Signup and view all the answers

What is the function of thyrotropin releasing hormone (TRH)?

Releases thyroid stimulating hormone (TSH) Signup and view all the answers

Study Notes

Endocrine Glands

Ductless glands that release hormones directly into the bloodstream
Hormones travel to target sites to exert their effects
Consists of:
- Hypothalamus
- Pituitary gland
- Thymus gland
- Thyroid gland
- Pancreas
- Adrenal gland
- Reproductive system

Hypothalamic-Pituitary Unit

Hypothalamus connects the nervous and endocrine systems
Posterior pituitary contains axons from neurons in the hypothalamus
Hormones synthesized in the hypothalamus are transported to the posterior pituitary for release
Neurohormones are synthesized in the hypothalamus and transported to the anterior pituitary via a portal vascular system
Hypothalamic connections with the pituitary gland:
- Vascular connection (hypothalamo-hypophysial portal circulation)
- Nervous connection (hypothalamo-hypophysial tract)

Control of the Endocrine System

Negative feedback loop regulates hormone levels
Hypothalamus secretes releasing and inhibiting hormones that control pituitary hormone secretion
Pituitary hormones control the secretion of hormones from target glands
Long feedback loops: Hormones from target glands feedback to the hypothalamus and pituitary to regulate their own secretion
Short feedback loops: Anterior pituitary hormones feedback to the hypothalamus to regulate their own secretion

Hypothalamic Neurosecretory Cells

Controlled by:
- Signals from brain areas in response to internal and external stimuli, including stress
- Short feedback loops from anterior pituitary hormones
- Long feedback loops from endocrine glands

Anterior Pituitary Hormones and their Regulation

Releasing hormones: Stimulate the release of specific anterior pituitary hormones
Inhibiting hormones: Inhibit the release of specific anterior pituitary hormones
Anterior Pituitary Hormones:
- Growth hormone (GH): Regulated by growth hormone-releasing hormone (GH-RH) and somatostatin
- Prolactin: Regulated by prolactin-releasing hormone (PRH) and dopamine (prolactin-inhibiting hormone, PIH)
- Thyroid stimulating hormone (TSH): Regulated by thyrotropin-releasing hormone (TRH)
- Adrenocorticotropic hormone (ACTH): Regulated by corticotropin-releasing hormone (CRH)
- Gonadotropic hormones (FSH & LH): Regulated by gonadotropin-releasing hormone (GnRH)

Pituitary Gland

Master gland of the endocrine system
Anterior pituitary hormone secretion regulated by:
- Hypophysiotropic releasing and inhibiting hormones
- Long feedback loops from hormones of endocrine glands
Secretes:
- Thyroid stimulating hormone (TSH)
- Adrenocorticotropic hormone (ACTH)
- Gonadotropic hormones (FSH & LH)
- Growth hormone (GH)
- Prolactin hormone
- Oxytocin hormone
- Antidiuretic hormone (ADH)

Anterior Pituitary Hormones and their Functions

Thyroid stimulating hormone (TSH): Stimulates growth and secretion of the thyroid gland
Adrenocorticotropic hormone (ACTH): Stimulates growth and secretion of the adrenal gland
Growth hormone (GH): Stimulates growth of bones and tissues, leading to increased weight and height
Prolactin: Stimulates milk synthesis
Gonadotropic hormones (FSH & LH):
- In females, they stimulate maturation of ova and synthesis of female sex hormones
- In males, they stimulate spermatogenesis and production of male sex hormones

Functions of Growth Hormone

Somatic Growth:
- Growth of long bones: Stimulates proliferation of epiphyseal cartilage
- Growth of soft tissues in muscles and organs
Metabolic Effects:
- Fat metabolism: Lipolysis
- Carbohydrate metabolism: Anti-insulin effect
Mechanism of Action:
- Direct action on cells: Diabetogenic action, lipolysis, increased protein synthesis, production of IGF-I by the liver
- Indirect action: Via production of insulin-like growth factor I (IGF-I) by the liver, which then acts on target tissues

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Description

Explore the functions and components of the endocrine system, focusing on major glands like the hypothalamus and pituitary gland. Understand how hormones are released and regulated through various feedback mechanisms. This quiz will test your knowledge on the intricate connections between the nervous and endocrine systems.