The Endocrine System Overview

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Questions and Answers

What type of hormone may be taken orally due to its lipid-soluble nature?

Adrenal cortex hormones (correct)

Neuropeptides

Protein hormones

Peptide hormones

What is the term for the specific cells that respond to hormone action?

Stimulating cells

Receptor cells

Hormonal units

Target cells (correct)

Which mechanism controls hormone secretion based on the concentration of the substance that it regulates?

Tropic Hormones

Positive Feedback Mechanism

Negative Feedback Mechanism (correct)

Nervous Stimulation

What type of hormones stimulate the secretion of other hormones?

Tropic Hormones Signup and view all the answers

How do protein hormones differ in their administration compared to steroid hormones?

They must be injected due to stomach inactivation. Signup and view all the answers

What is the primary function of Growth Hormone (GH)?

Promotes protein synthesis for growth of bones and muscles Signup and view all the answers

What condition results from hyposecretion of Growth Hormone in children?

Pituitary Dwarfism Signup and view all the answers

Which hormone is responsible for stimulating the thyroid gland to secrete thyroid hormones?

Thyroid Stimulating Hormone (TSH) Signup and view all the answers

What is the outcome of hypersecretion of Thyroid Stimulating Hormone (TSH)?

Hyperthyroidism due to thyroid enlargement Signup and view all the answers

What effect does Adrenocorticotropic Hormone (ACTH) have on skin pigmentation?

Stimulates melanocytes to increase skin pigmentation Signup and view all the answers

What is the primary role of glucagon in the body?

Increases blood glucose levels Signup and view all the answers

Which hormones are produced by the adrenal medulla?

Epinephrine and norepinephrine Signup and view all the answers

What hormone does the pineal gland secrete?

Melatonin Signup and view all the answers

What is the primary function of estrogen and progesterone in the ovaries?

Regulate reproductive changes during puberty Signup and view all the answers

What is the main effect of cholestokinin (CCK) on the digestive system?

Causes contraction of the gall bladder Signup and view all the answers

In which organ are insulin and glucagon produced?

Pancreas Signup and view all the answers

Which hormone produced by the heart helps to decrease blood pressure?

Atrial natriuretic peptide (ANP) Signup and view all the answers

What function does thymosin primarily serve in the body?

Stimulates immune function Signup and view all the answers

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

Stimulates testosterone production Signup and view all the answers

What hormone is responsible for milk production?

Prolactin Signup and view all the answers

Which hormone is secreted by parafollicular cells and lowers blood calcium levels?

Calcitonin Signup and view all the answers

What condition is caused by iodine deficiency?

Simple goiter Signup and view all the answers

Which hormone is produced by the adrenal cortex and helps to regulate blood glucose levels?

Cortisol Signup and view all the answers

Hyperparathyroidism is characterized by which condition?

Hypercalcemia Signup and view all the answers

Antidiuretic Hormone (ADH) is also known as?

Vasopressin Signup and view all the answers

What is the primary role of aldosterone?

Regulate sodium and potassium balance Signup and view all the answers

Which hormone has no effect on milk ejection?

Prolactin Signup and view all the answers

Study Notes

Overview of the Endocrine System

Comprises glands that secrete hormones (chemical messengers) directly into the bloodstream.
Functions of hormones include regulating growth, development, and metabolic activities.

Hormones: Nature and Action

Steroid hormones (e.g., adrenal cortex and sex hormones) are lipid-soluble and can be taken orally.
Protein hormones (made of amino acids) cannot be administered orally due to stomach inactivation.
Target cells respond to hormones at specific receptor sites.

Control of Hormone Secretion

Negative Feedback Mechanism: Regulates hormone levels based on the concentration of specific substances (e.g., insulin and glucose).
Tropic Hormones: Stimulate secretion from other glands (e.g., ACTH and TSH).
Nervous Stimulation: Sympathetic nervous system triggers adrenaline secretion from adrenal medulla.
Releasing and Inhibiting Hormones: Produced by the hypothalamus to influence pituitary gland activity.

Pituitary Gland

Also known as hypophysis, it measures about 1 centimeter in diameter, located in the sella turcica of the sphenoid bone.
Divided into anterior lobe (adenohypophysis) and posterior lobe (neurohypophysis).

Hormones of the Anterior Lobe

Growth Hormone (GH): Stimulates growth and protein synthesis; hyposecretion causes dwarfism, hypersecretion causes giantism and acromegaly in adults.
Thyroid Stimulating Hormone (TSH): Stimulates thyroid hormone secretion; hypersecretion leads to hyperthyroidism, hyposecretion leads to hypothyroidism.
Adrenocorticotropic Hormone (ACTH): Stimulates adrenal cortex to release cortisol and increases skin pigmentation.
Gonadotropic Hormones (FSH & LH): FSH promotes egg and sperm development; LH triggers ovulation and stimulates testosterone production.

Hormones of the Adrenal Medulla

Secretes epinephrine (80%) and norepinephrine (20%).
These hormones stimulate the heart and raise blood pressure during stress (fight or flight response).

The Pancreas

Functions as both exocrine and endocrine organ, with islets of Langerhans secreting glucagon (raises blood glucose) and insulin (lowers blood glucose).
Insulin hyposecretion results in diabetes mellitus characterized by high blood sugar levels.

Gonads (Testes & Ovaries)

Testes produce sperm and testosterone, influencing male puberty.
Ovaries produce ova and hormones like estrogen and progesterone, influencing female puberty.
Sex hormone levels are regulated by negative feedback mechanisms.

Pineal Gland

Secretes melatonin, regulating reproductive development and circadian rhythms such as sleep and mood patterns.

Thymus Gland

Located in the thoracic cavity, produces thymosin which supports immune function; most active during childhood.

Other Organs with Endocrine Functions

Stomach: Produces gastrin, stimulating acid and enzyme production.
Small Intestine: Secretes secretin (increases pancreatic bicarbonate secretion) and cholecystokinin (inducing gallbladder contraction).
Heart: Produces atrial natriuretic peptide (ANP), regulating blood volume and pressure.
Placenta: Produces human chorionic gonadotropin (hCG) to maintain pregnancy.
Kidney: Produces erythropoietin (increases red blood cell formation) and renin (increases blood pressure).

Thyroid Gland

Vascular gland with two lobes connected by an isthmus.
Contains follicles that secrete thyroxine (T4) and triiodothyronine (T3), both requiring iodine for synthesis.
Hypothyroidism leads to cretinism in infants and myxedema in adults; hyperthyroidism causes thyrotoxicosis.

Calcitonin and Parathyroid Glands

Calcitonin: Secreted in response to elevated calcium levels, reduces blood calcium by decreasing bone release, intestinal absorption, and renal absorption.
Parathyroid Glands: Four small glands secreting parathyroid hormone (PTH) to increase blood calcium levels; hypoparathyroidism can lead to tetany.

Adrenal Glands

Positioned atop kidneys, composed of an outer adrenal cortex (essential for life) and inner adrenal medulla (not essential).
Cortical Hormones:
- Mineralocorticoids (e.g., aldosterone): Regulate blood volume and electrolyte balance.
- Glucocorticoids (e.g., cortisol): Increase blood glucose and counter inflammation.

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Description

This quiz covers the fundamental aspects of the endocrine system, focusing on the glands that secrete hormones and their roles in growth, development, and metabolism. Learn about the nature and action of various hormones, including steroid and protein hormones. Test your knowledge of this essential biological system.