L35-2

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Questions and Answers

What distinguishes endocrine glands from exocrine glands?

Exocrine glands produce hormones that regulate metabolism.

Endocrine glands have a slower response time than exocrine glands.

Endocrine glands release hormones into the bloodstream. (correct)

Exocrine glands secrete hormones directly into the blood.

How do hormones typically reach their target organs?

Through the bloodstream. (correct)

Via the lymphatic system.

By diffusion through tissue membranes.

Through nerve impulses.

Which class of hormones is made from cholesterol?

Steroid hormones (correct)

Peptide hormones

Amine hormones

Amino acid-based hormones

What is primarily responsible for the action of hormones on target cells?

Hormonal receptors Signup and view all the answers

What type of hormones are derived from proteins and peptides?

Amino acid-based hormones Signup and view all the answers

Which of the following processes is primarily involved in maintaining homeostasis?

Hormonal signaling Signup and view all the answers

Which type of hormone is associated with highly active lipids?

Prostaglandins Signup and view all the answers

Which of the following statements about the response time of hormones is true?

Hormonal responses vary widely but are often slower than neural responses. Signup and view all the answers

What role do specialized cells play in the endocrine system?

They produce and secrete hormones into extracellular fluids. Signup and view all the answers

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

Promotes the growth of skeletal muscles and long bones Signup and view all the answers

Which hormone primarily decreases blood calcium levels?

Calcitonin Signup and view all the answers

Which of the following hormones is known to stimulate milk production after childbirth?

Prolactin (PRL) Signup and view all the answers

What type of feedback regulates hormone levels in the bloodstream?

Negative feedback Signup and view all the answers

Which gland is controlled by other hormones and is considered part of the endocrine system?

Pituitary gland Signup and view all the answers

What is the primary role of glucocorticoids in the adrenal cortex?

Control metabolism and stress response Signup and view all the answers

Which hormone is responsible for maturing white blood cells and is produced by the thymus?

Thymosin Signup and view all the answers

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

Secretes melatonin for sleep regulation Signup and view all the answers

What effect does adrenaline (epinephrine) have on the body?

Enhances the fight-or-flight response Signup and view all the answers

Which hormone is primarily responsible for regulating the activity of the adrenal cortex?

Adrenocorticotropic hormone (ACTH) Signup and view all the answers

Which of the following processes is NOT controlled by hormones in the endocrine system?

Physical strain adaptation Signup and view all the answers

Which of the following is a characteristic of steroid hormones?

Derived from cholesterol Signup and view all the answers

What is the primary role of hormones in the endocrine system?

Regulate the activity of other cells Signup and view all the answers

Which statement best describes the role of target organs in the endocrine system?

They respond to specific hormones released in the bloodstream. Signup and view all the answers

Which of the following describes the response time of hormones in the endocrine system?

Variable and potentially prolonged Signup and view all the answers

What is the main basis for classifying hormones as amino acid-based or steroid-based?

Their chemical structure Signup and view all the answers

Which of these hormone types is involved in mobilizing body defenses?

Adrenaline Signup and view all the answers

What distinguishes exocrine glands from endocrine glands?

They have ducts that carry secretions to their target sites. Signup and view all the answers

In the endocrine system, which component primarily facilitates the transport of hormones to target sites?

The bloodstream Signup and view all the answers

Which of the following best describes the relationship between hormone receptors and their hormones?

Each hormone has an exclusive receptor that determines its action. Signup and view all the answers

What triggers the release of hormones from endocrine glands?

Hormonal and non-hormonal stimuli Signup and view all the answers

What is the primary function of luteinizing hormone (LH) in males?

Stimulating testosterone production Signup and view all the answers

Which hormone is primarily responsible for stimulating the secretion of glucocorticoids from the adrenal cortex?

Adrenocorticotropic hormone (ACTH) Signup and view all the answers

What is one of the roles of calcitonin in the body?

Reducing blood calcium levels by promoting bone deposition Signup and view all the answers

Which type of hormone acts through second-messenger systems?

Peptide and protein hormones Signup and view all the answers

How does the adrenal medulla respond to short-term stress?

By releasing catecholamines such as epinephrine Signup and view all the answers

What hormone produced by the pancreas lowers blood sugar levels?

Insulin Signup and view all the answers

Which of the following hormones plays a key role in establishing sleep cycles?

Melatonin Signup and view all the answers

What is the major metabolic hormone produced by the thyroid gland?

Thyroxine (T4) Signup and view all the answers

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

Promoting growth of skeletal muscles and long bones Signup and view all the answers

Study Notes

Endocrine System Overview

The endocrine system is a second messenger system using chemical messengers (hormones) released into the bloodstream.
Hormones control many bodily processes, including: reproduction, growth and development, mobilization of body defenses, homeostasis, and metabolism.
Hormones are produced by specialized cells and secreted into extracellular fluids, then transported to target cells via the blood.
These hormones regulate the activity of other cells.

Hormone Chemistry

Hormones are categorized into different chemical types: amino acid-based hormones (e.g., proteins, peptides, amines) and steroids, made from cholesterol, and prostaglandins, derived from fatty acids.

Mechanisms of Hormone Action

Hormones act on specific tissues, or target cells/organs.
Target cells must have specific protein receptors for the hormone to bind.
Binding hormones influences the target cell's function.

Hormone Release Control

Hormone levels are regulated by a negative feedback loop.
A stimulus or low hormone levels trigger hormone release.
Hormone release stops once the appropriate blood level is reached.

Hormonal Stimuli of Endocrine Glands

Endocrine glands are activated by other hormones.
Changes in blood levels of certain ions can trigger hormone release.

Pituitary Gland

A small gland, about the size of a grape; suspended from the hypothalamus by a stalk.
Protected by the sphenoid bone.
Has two lobes: anterior (glandular tissue) and posterior (nervous tissue).

Hormones of the Anterior Pituitary

Six hormones are produced in the anterior pituitary.
Two hormones affect non-endocrine targets, and four others stimulate other endocrine glands (tropic hormones).
All anterior pituitary hormones are proteins, or peptides, and operate via second-messenger systems.
Mostly regulated by hormonal stimuli; primarily negative feedback.

Growth Hormone (GH)

A general metabolic hormone affecting skeletal muscles and long bones.
Promotes amino acid incorporation into proteins and fat breakdown for energy.

Functions of Other Anterior Pituitary Hormones

Prolactin (PRL): Important for milk production in females.
Adrenocorticotropic hormone (ACTH): Regulates adrenal cortex endocrine activity.
Thyroid-stimulating hormone (TSH): Influences thyroid growth and activity.
Gonadotropic hormones:
- Follicle-stimulating hormone (FSH): Stimulates follicle development in ovaries, and sperm development in testes.
- Luteinizing hormone (LH): Triggers ovulation, helps the ruptured follicle become the corpus luteum, and stimulates testosterone production in males (also known as interstitial cell-stimulating hormone (ICSH)).

Hormones of the Posterior Pituitary

Oxytocin: Stimulates uterine contractions during labor and milk ejection.
Antidiuretic hormone (ADH): Inhibits urine production and, in high amounts, causes vasoconstriction, increasing blood pressure (also known as vasopressin).

Thyroid Gland

Consists of two lobes connected by an isthmus.
Produces two hormones: thyroid hormone and calcitonin.

Thyroid Hormone

A major metabolic hormone composed of two iodine-containing hormones:
- Thyroxine (T4): Secreted by thyroid follicles.
- Triiodothyronine (T3): Conversion of T4 at target tissues.

Calcitonin

Lowers blood calcium levels by promoting calcium deposition into bone.
Antagonistic to parathyroid hormone.
Produced by parafollicular cells (C cells).

Parathyroid Glands

Tiny masses on the posterior of the thyroid.
Secrete parathyroid hormone (PTH).
Stimulates osteoclasts to release calcium from bone, and stimulates the kidneys and intestine to absorb more calcium.
Raises blood calcium levels.

Adrenal Glands

Located on top of kidneys.
Composed of two parts: cortex (outer, glandular) and medulla (inner, neural tissue).

Hormones of the Adrenal Cortex

Mineralocorticoids (mainly aldosterone): Produced in the outer adrenal cortex. Regulates mineral content in blood, water, and electrolyte balance; targets the kidney. Stimulated by renin and aldosterone, inhibited by atrial natriuretic peptide.
Glucocorticoids (e.g., cortisone, cortisol): Produced in the middle adrenal cortex layer and promote normal cell metabolism, aiding resistance to long-term stressors. Released in response to increased blood ACTH levels.
Sex hormones (androgens and some estrogen): Produced in the inner adrenal cortex layer. Androgens are male sex hormones, and some estrogen is a female sex hormone.

Hormones of the Adrenal Medulla

Produces similar hormones (catecholamines):
- Epinephrine: Aids body in dealing with short-term stressors.
- Norepinephrine: Aids body in dealing with short-term stressors.

Pancreatic Islets

The pancreas is a mixed gland.
The islets produce:
- Insulin: Allows glucose to enter cells (released from beta cells).
- Glucagon: Allows glucose to leave cells (released from alpha cells).
These hormones work as antagonists to maintain blood sugar homeostasis.

Pineal Gland

Located on the third ventricle of the brain.
Secretes melatonin, which helps establish wake/sleep cycles.

Thymus

Located posterior to the sternum.
Largest in infants/children. Produces thymosin.
Matures some types of white blood cells, important in developing the immune system.

Hormones of the Ovaries

Estrogens: Produced by Graafian follicles or the placenta; stimulates development of secondary female characteristics, matures female reproductive organs, helps prepare the uterus, helps maintain pregnancy, and prepares the breasts.
Progesterone: Produced by the corpus luteum and acts with estrogen to bring about the menstrual cycle, aiding implantation of an embryo.

Hormones of the Testes

Interstitial cells in testes produce androgens.
Testosterone is the most crucial androgen. Responsible for adult male sex characteristics, promotes growth/maturation of the male reproductive system, and is essential for sperm production.

Other Hormone-Producing Tissues and Organs

Parts of the small intestine
Parts of the stomach
Kidneys
Heart
Scattered endocrine cells in various tissues

Endocrine Function of the Placenta

Produces hormones to maintain pregnancy and delivery.
Produces human chorionic gonadotropin (HCG) alongside other hormones like estrogen and progesterone.

Developmental Aspects of the Endocrine System

Most endocrine organs work smoothly until old age.
Menopause is caused by low ovarian efficiency.
Reduced estrogen levels pose problems.
Growth hormone production declines with age.
Many endocrine glands decline in output as we age.

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Description

Test your knowledge on the endocrine system and its functions. This quiz covers hormonal categories, mechanisms of action, and hormone release control. Understand how hormones affect bodily processes and their significance in maintaining homeostasis.