Endocrine System Quiz

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Questions and Answers

What primary action does Parathyroid Hormone (PTH) perform on bones?

Enhances bone formation

Stimulates the production of collagen in bones

Increases bone resorption and mobilizes calcium (correct)

Inhibits calcium release from bones

Which hormone is primarily responsible for lowering blood glucose levels?

Glucagon

Cortisol

Insulin (correct)

Epinephrine

What is the role of glucagon in the body?

Promotes amino acid storage

Increases fatty acid synthesis

Facilitates insulin secretion

Stimulates gluconeogenesis and elevates blood glucose (correct)

Which statement is true regarding the secretion of estrogen?

Secreted by the walls of the developing ovarian follicles Signup and view all the answers

What is the effect of 1,25 dihydroxycholecalciferol (Vitamin D3) related to calcium?

Increases gut calcium absorption Signup and view all the answers

What is the primary function of the endocrine system?

Maintenance of homeostasis Signup and view all the answers

Which hormone is known for regulating growth and protein production?

Growth Hormone Signup and view all the answers

How do hormones affect cellular activities?

They regulate reactions rather than initiating them. Signup and view all the answers

Which gland is referred to as the 'Master Gland'?

Pituitary Gland Signup and view all the answers

What is NOT a function of the hypothalamus?

Producing digestive enzymes Signup and view all the answers

Which of the following statements about hormones is true?

Hormones are inactivated at the site of action. Signup and view all the answers

What is the role of the releasing inhibitory hormones produced by the hypothalamus?

Inhibit the secretion of various hormones Signup and view all the answers

What is the primary function of glucocorticoids like cortisol in the body?

Increasing blood glucose levels Signup and view all the answers

Which section of the adrenal gland is responsible for secreting aldosterone?

Zona glomerulosa Signup and view all the answers

What characterizes the response of the adrenal medulla hormones during stress?

Preparation for emergency action Signup and view all the answers

What condition is primarily caused by an under secretion of glucocorticoids and mineralocorticoids?

Addison's disease Signup and view all the answers

What stimulates the secretion of glucocorticoids like cortisol from the adrenal cortex?

Anterior pituitary ACTH Signup and view all the answers

Which of the following effects is NOT associated with epinephrine's action during stress?

Enhancing nutrient absorption in the gut Signup and view all the answers

What is one of the effects of aldosterone on the kidneys?

Enhances sodium reabsorption Signup and view all the answers

Which hormone is primarily responsible for stimulating the release of Thyroxine (T4) and Triiodothyronine (T3)?

Thyrotropin (TSH) Signup and view all the answers

Which statement about cortisol is true?

It is regulated by ACTH. Signup and view all the answers

Which hormone is considered a catecholamine produced by the adrenal medulla?

Norepinephrine Signup and view all the answers

What effect do T3 and T4 have on metabolic activities?

They stimulate metabolic activities in most tissues except for certain organs. Signup and view all the answers

Which of the following is NOT a clinical sign associated with thyroid dysfunction?

Increased appetite Signup and view all the answers

How are T3 and T4 synthesized?

By utilizing iodine and the colloid filled follicles of the thyroid. Signup and view all the answers

Which enzymes are stimulated or activated by thyroid hormones?

Cytochromes b and c, and hexokinase Signup and view all the answers

What is the primary location of the thyroid gland in the body?

On the trachea, just caudal to the larynx Signup and view all the answers

What is the result of decreased levels of thyroid hormones?

Decreased secretion of TSH from the anterior pituitary Signup and view all the answers

Which condition may result from excessive levels of thyroid hormones?

Hyperactivity and weight loss Signup and view all the answers

What is a common sign of hypothyroidism?

Muscle wasting Signup and view all the answers

Which of the following statements regarding the thyroid gland is incorrect?

The thyroid gland is a part of the digestive system. Signup and view all the answers

What condition is characterized by thyroid gland enlargement due to colloid accumulation?

Goiter Signup and view all the answers

Which hormone is primarily responsible for lowering blood calcium levels?

Calcitonin Signup and view all the answers

In young animals, what is a primary consequence of hypothyroidism?

Dwarfism Signup and view all the answers

Which condition is more common in older cats due to increased demands on the thyroid gland?

Hyperthyroidism Signup and view all the answers

What physiological response stimulates the secretion of calcitonin?

Hypercalcemia Signup and view all the answers

Which hormone acts antagonistically to calcitonin in calcium homeostasis?

Parathyroid Hormone Signup and view all the answers

What is the function of parathyroid hormone (PTH)?

Increases the rate of bone resorption Signup and view all the answers

Why do older animals with hypothyroidism generally become obese and sluggish?

Reduced metabolic rate Signup and view all the answers

Which animal is most likely to show signs of hypothyroidism, including weight gain and lethargy?

Old dogs Signup and view all the answers

What factor is essential for regulating the secretion of parathyroid hormone?

Blood calcium levels Signup and view all the answers

Study Notes

Introduction to the Endocrine System

Endocrinology is a branch of physiology focused on the study of endocrine glands and their chemical messengers.
These messengers regulate the activity of other cells within the body.

The Endocrine System's Role

The endocrine system works alongside the nervous system to regulate the body.
Its primary function is homeostasis—maintaining a stable internal environment.

Hormones

Hormones are chemical substances released from endocrine glands.
They originate from Greek word "hormon" meaning "to arouse or to stimulate".
Hormones regulate the activity of other cells within the body.
The action of hormones typically involves a target cell that is unique to a specific hormone and possesses receptors for the specific hormone.
Hormones are released indirectly into the blood stream to act on target cells.
Hormones act to regulate rather than initiate reactions within the body.
Their action, and/or inactivation, is rapid and happens at target organ sites.
They are present in biocatalytic amounts, and not released at a uniform rate.

Types of Hormones

Hormones are categorized based on their chemical structure.
- Steroids: Derived from lipids, produced by gonads, adrenal cortex, and placenta. Common examples include progesterone and testosterone.
- Peptides: Short amino acid chains produced by the pituitary, parathyroid, heart, stomach, kidneys, and liver. Examples include oxytocin and luteinizing hormone.
- Amines: Secreted by the adrenal medulla and thyroid. Include epinephrine, norepinephrine, T3, and T4.

Hypothalamus and Pituitary Gland

The hypothalamus controls the pituitary gland.
The hypothalamus produces chemical signals (releasing stimulating hormones and releasing inhibitory hormones).
The hypothalamus regulates metabolism, heart rate, energy levels, body temperature, and thirst.
The pituitary gland is known as the "master gland," divided into two lobes (anterior and posterior).

Hormones of the Anterior Pituitary

Growth hormone (GH): Regulates growth at the epiphyses of bones; involved in protein production. Insufficient secretion of GH leads to pituitary dwarfism, while too much leads to gigantism.
Adrenocorticotropic hormone (ACTH): Stimulates the adrenal cortex to secrete various hormones.
Thyroid-stimulating hormone (TSH): Stimulates thyroid hormone production.
Gonadotropic hormones:
- Follicle-stimulating hormone (FSH): Stimulates oogenesis in females and spermatogenesis in males.
- Luteinizing hormone (LH): In females, assists in ovulation and corpus luteum function; in males, it stimulates testosterone secretion.
Prolactin: Initiates and maintains lactation.

Hormones of the Posterior Pituitary

Antidiuretic hormone (ADH, aka Vasopressin): Regulates water balance by affecting the kidneys. When the body is too hydrated, ADH diminishes output of dilute urine.
Oxytocin: Released by the posterior pituitary gland in neuroendocrine reflexes. This hormone is involved in uterine contractions and milk ejection.

Adrenal Glands

The adrenal glands are paired structures located above the kidneys.
- Adrenal cortex: The outer layer which secretes steroid hormones:
  - Glucocorticoids (e.g., cortisol): Regulate glucose levels, response to stress/adaptation.
  - Mineralocorticoids (e.g., aldosterone): Regulates mineral balance(sodium and potassium) in blood via kidney function.
- Adrenal medulla: The inner portion secreting catecholamine hormones:
  - Epinephrine (adrenaline), norepinephrine (noradrenaline): Responses to emergency action, controlled via the sympathetic nervous system. These hormones increase blood sugar, heart rate and respiration, and dilate skeletal muscles.

Thyroid Gland

Located in the neck, just below the larynx.
Composed of numerous follicles containing colloid.
Secretes tetraiodothyronine (T4), triiodothyronine (T3), and calcitonin.
T3 and T4 are crucial metabolic regulators.

Parathyroid Glands

Embedded within the thyroid gland.
Secretes parathyroid hormone (PTH), a hypercalcemic hormone (it increases blood calcium).
PTH influences bone, kidney, and GI tract functions affecting calcium.

Pancreas

A gland located in the abdomen, close to the duodenum.
Has exocrine (producing digestive enzymes) and endocrine (producing hormones) functions.
Endocrine portion consists of islets of Langerhans.
- Alpha cells secrete glucagon.
- Beta cells secrete insulin.

Gonads (Ovaries and Testes)

Ovaries: Located in the abdominal cavity; produce estrogen and progesterone.
Testes: Located outside the abdominal cavity; produce testosterone, and a small amount of estrogen.

Diseases

Addison's Disease: Caused by under-secretion of glucocorticoids and mineralcorticoids. Symptoms include vomiting, diarrhea, anorexia, lethargy, dehydration and bradycardia.
Cushing's Disease: Caused by over-secretion of glucocorticoids. Symptoms include polydipsia, polyuria, polyphagia, bilateral symmetrical alopecia, muscle wasting and potbelly.
Hypothyroidism: Deficiency in thyroid hormones, causing slowed metabolism, often in dogs.
Hyperthyroidism: Overproduction of thyroid hormones, causing sped up metabolism, often in cats.

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Description

Test your knowledge on the fundamental principles of the endocrine system. This quiz covers hormones, their functions, and the glands responsible for their secretion. From Parathyroid Hormone to the actions of glucagon, challenge yourself with these essential questions.