Hormones Overview

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which hormone is primarily released by the adrenal medulla during stressful situations?

Androstenedione

Epinephrine (correct)

Cortisol

Aldosterone

Which type of stimuli involves the direct stimulation of glands by nerve fibers?

Humoral stimuli

Chemical stimuli

Neural stimuli (correct)

Hormonal stimuli

What is the primary function of cortisol in the body?

To promote sex drive

To enhance water retention

To increase glucose availability (correct)

To stimulate sodium absorption

What role does the hypothalamus play in the endocrine system?

It functions as a neuroendocrine organ. Signup and view all the answers

In response to situations of fear or stress, which part of the adrenal gland is directly stimulated?

Adrenal medulla Signup and view all the answers

Which type of hormone is aldosterone classified as?

Mineralocorticoid Signup and view all the answers

What is the primary method of hormone transportation within the endocrine system?

Bloodstream Signup and view all the answers

Which statement best describes how hormonal secretion is initiated?

It is regulated by both internal and external stimuli. Signup and view all the answers

What effect does androstenedione primarily have in the body?

Might be related to sex drive Signup and view all the answers

Which hormone is secreted by the parathyroid gland in response to low blood calcium levels?

Parathyroid hormone (PTH) Signup and view all the answers

How does negative feedback affect hormone secretion within the endocrine system?

It inhibits secretion when hormone levels are high. Signup and view all the answers

In which scenario would humoral stimuli be activated?

When blood glucose levels increase. Signup and view all the answers

What characterizes a tropic hormone?

It controls the secretion of another hormone. Signup and view all the answers

Which hormone is primarily synthesized as a protein and is known to stimulate the thyroid gland?

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

What is the main function of the antidiuretic hormone (ADH)?

Regulating water balance and osmolarity Signup and view all the answers

What type of hormone can easily pass through a cell membrane to reach its receptor?

Thyroid hormone Signup and view all the answers

How does the anterior pituitary communicate with the hypothalamus?

Via blood vessels Signup and view all the answers

What triggers the hypothalamus to release antidiuretic hormone (ADH)?

Decreased blood volume or increased blood osmolarity Signup and view all the answers

Negative feedback loops in the endocrine system serve what main purpose?

To counteract changes and maintain homeostasis Signup and view all the answers

Which of the following hormones is classified as a peptide hormone?

Calcitonin Signup and view all the answers

Which hormone is primarily responsible for stimulating uterine contractions during labor?

Oxytocin Signup and view all the answers

What is the significance of the hypothalamus concerning homeostasis?

It stores the ideal set-point for various physiological variables. Signup and view all the answers

Which hormones are produced by the thyroid gland?

T3 and T4 Signup and view all the answers

What defines the release mechanism of protein hormones?

They are synthesized, stored, and released upon proper stimulation. Signup and view all the answers

What type of relationship exists between the hypothalamus and the anterior pituitary?

Sequential control via hypophysiotropic hormones Signup and view all the answers

What is the main function of the hormones produced by the posterior pituitary?

To assist in water balance and uterine function Signup and view all the answers

In a positive feedback loop, the physiological response is aimed at what?

Increasing the magnitude of the initial change Signup and view all the answers

Which hormone is regulated by its elimination through urine excretion and liver breakdown?

Epinephrine Signup and view all the answers

What characterizes the anterior pituitary in relation to the hypothalamus?

It secretes only tropic hormones Signup and view all the answers

What is the primary function of T3 in the body?

Increases metabolism in most tissues Signup and view all the answers

How do parathyroid glands respond when blood calcium levels are low?

They release parathyroid hormone (PTH) Signup and view all the answers

What role does calcitonin play in calcium metabolism?

Promotes calcium deposition in bones Signup and view all the answers

What are the two hormones produced by the pancreatic islets?

Insulin and glucagon Signup and view all the answers

Which type of hormones are produced by the adrenal cortex?

Mineralocorticoids, glucocorticoids, and androgens Signup and view all the answers

What triggers the release of insulin from the pancreas?

Increase in blood glucose levels Signup and view all the answers

What is responsible for the regulation of calcium levels in the small intestine?

Parathyroid hormone (PTH) Signup and view all the answers

Which gland plays a role in both endocrine and digestive systems?

Pancreas Signup and view all the answers

Study Notes

Hormones

Thyroid hormones (T3 and T4), dopamine, epinephrine (adrenaline), norepinephrine, and melatonin can cross cell membranes, but some more easily than others
Thyroid hormone can easily pass across a cell membrane to reach a receptor inside the cell, while epinephrine cannot
Protein hormones are made of chains of amino acids and include:
- Insulin
- Thyroid-stimulating hormone (TSH)
- Follicle-stimulating hormone (FSH)
- Luteinizing hormone (LH)
- Growth hormone (GH, or human growth hormone HGH, or somatotropin)
- Parathyroid hormone (PTH)
- Antidiuretic hormone (ADH)
- Adrenocorticotropic hormone (ACTH)
- Glucagon
- Calcitonin
- Oxytocin
- Hormones from the hypothalamus
Proteins are too large to pass through cell membranes
Peptide and protein hormones are synthesized in stages, stored in secretory sacs, and only released when the hormone-secreting cell receives a proper stimulation
After a hormone is secreted into the blood, three outcomes may take place:
- The hormone is either removed from the blood by the liver or kidney
- The hormone is converted to an inactive form.
- The hormone binds to its target cell and causes a change in its function

Homeostasis

Homeostasis is a dynamic process of maintaining stable internal conditions
The body constantly monitors variables and compares them to a set point, which is the ideal level stored for that variable.
The hypothalamus stores the ideal set point for temperature
Both endocrine and nervous systems work to maintain levels at or near the set point

Feedback Loops

Negative feedback loops oppose the stimulus, helping to restore the variable to its set point
Positive feedback loops increase the magnitude of a change, amplifying it further away from the set point

Hormonal Control

Negative feedback is the primary mechanism controlling hormone secretion.
As hormone levels rise, negative feedback inhibits further secretion.
As hormone levels decrease, negative feedback triggers increased secretion.
Negative feedback can be triggered by internal or external stimuli.

Types of Stimuli for Endocrine Gland Actions

Humoral stimuli: Changes in blood levels of certain ions and nutrients.
- For example, parathyroid glands monitor blood calcium and secrete parathyroid hormone (PTH) when levels decrease.
Neural stimuli: Nerve fibers directly stimulate certain glands.
- For example, the sympathetic nervous system stimulates the adrenal medulla to release norepinephrine and epinephrine in stressful situations.
Hormonal stimuli: Hormone release due to the production of other hormones.
- For example, the hypothalamus regulates the secretion of pituitary hormones.

Endocrine Organs

The endocrine system is a network of glands that secrete hormones into the bloodstream, affecting various bodily functions.
The major functions of the endocrine system include:
- Regulating metabolism
- Controlling chemical reactions
- Transporting substances
- Regulating water and electrolyte balance
- Aiding in reproduction, growth, and development
Organs that secrete hormones include:
- Hypothalamus
- Pituitary gland
- Thyroid gland
- Parathyroid glands
- Pancreas
- Adrenal glands
- Stomach, small intestine, kidneys, and heart may also secrete hormones.

Hypothalamus and Pituitary Gland

The pituitary gland is divided into the anterior and posterior pituitary
Often called the “master gland” due to its role in controlling other endocrine glands.
The pituitary gland acts under orders from the hypothalamus, with which it is directly connected.
The hypothalamus secretes hypophysiotropic hormones that regulate the anterior pituitary, while the posterior pituitary secretes tropic hormones
The anterior pituitary is connected to the hypothalamus through blood vessels.
The posterior pituitary is connected to the hypothalamus through neurons that secrete antidiuretic hormone (ADH) and oxytocin hormone, which are synthesized in the hypothalamus.

Antidiuretic Hormone (ADH)

Also known as vasopressin, ADH is involved in regulating water balance and osmolarity.
Secreted by the hypothalamus when it senses decreased blood volume or increased blood osmolarity, triggering the kidneys to reabsorb more water.
Crucial in long-term blood pressure control, especially during dehydration.

Oxytocin

Plays a vital role in:
- Maintaining uterine contractions during labor
- Milk ejection from the breasts during breastfeeding
Its function in males is not fully understood

Anterior Pituitary Hormones

Human Growth Hormone (hGH): Promotes growth and development, especially in children.
Thyroid-stimulating hormone (TSH): Stimulates the thyroid gland to produce thyroid hormone (T3 and T4).
Adrenocorticotropic hormone (ACTH): Stimulates the adrenal cortex to produce cortisol and other corticosteroids.
Follicle-stimulating hormone (FSH): In females, it stimulates the growth and development of follicles in the ovaries. In males, it stimulates the production of sperm cells.
Luteinizing hormone (LH) : In females, it triggers ovulation and production of estrogen and progesterone. In males, it stimulates the production of testosterone.
Prolactin: Stimulates the mammary glands to produce milk.

Thyroid Gland

Located anterior and lateral to the trachea, just inferior to the larynx.
Secretes T3 (triiodothyronine) and T4 (thyroxine), collectively called thyroid hormone.
- Produced from tyrosine and iodide.
- T4 is secreted in larger amounts, but T3 is more active.
- Regulates metabolic rate, growth, brain development, and function
Also secretes calcitonin, which stimulates the deposition of calcium in bones, more relevant for children than adults.

Parathyroid Glands

Four small glands embedded in the posterior surface of the thyroid gland.
Produce parathyroid hormone (PTH), which regulates blood calcium levels by:
- Stimulating the reabsorption of calcium from bones
- Increasing the absorption of calcium in the small intestine

Pancreas

Part of both the endocrine and digestive systems.
Located inferior and posterior to the stomach.
Contains pancreatic islets (islets of Langerhans), which produce insulin and glucagon.

Insulin and Glucagon

Insulin is released when blood glucose levels rise, helping glucose enter cells and storing excess glucose as glycogen in the liver.
Glucagon is released when blood glucose levels fall, causing the liver to release glucose into the bloodstream.

Adrenal Glands

Situated superior and medial to the kidneys.
Composed of two parts:
- Adrenal cortex:
  - Outer layer of the adrenal gland
  - Produces over 30 steroid hormones (adrenocorticosteroids) divided into three categories:
    - Mineralocorticoids: Primarily aldosterone, which regulates sodium and potassium balance.
    - Glucocorticoids: Primarily cortisol, which regulates stress response and glucose metabolism.
    - Androgens: Sex hormones, including testosterone, produced in smaller amounts in the adrenal cortex.
  - Production is stimulated by the anterior pituitary.
- Adrenal medulla:
  - Middle layer of the adrenal gland
  - Stimulated by the sympathetic nervous system during stress, fear, and pain.
  - Releases epinephrine (adrenaline) and norepinephrine (noradrenaline) to enhance the body's “fight-or-flight” response.
  - Medulla cells can stimulate the cortex to secrete cortisol during times of stress.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz covers various hormones including thyroid hormones, protein hormones, and their characteristics. Explore how these hormones interact with cell membranes and the differences between peptide and protein hormones. Test your understanding of hormonal functions and synthesis as highlighted in this section.