Endocrine Glands and Thyroid Gland Overview

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Questions and Answers

What is the primary function of thyroid hormone (TH)?

Promoting adrenal function

Regulating blood calcium levels

Controlling metabolic rate (correct)

Enhancing reproductive hormone production

Which of the following statements about T3 and T4 is correct?

T3 contains four iodine atoms, while T4 contains three.

Salt is often iodized to provide iodine necessary for their synthesis. (correct)

T4 is more active than T3 in cellular metabolism.

Both T3 and T4 are hydrophilic.

Where is the thyroid gland located?

Behind the pancreas

In front of the trachea, just below the voice box (correct)

Next to the pituitary gland

Above the adrenal glands

What hormone regulates calcium levels in the blood alongside thyroid hormones?

Calcitonin Signup and view all the answers

Which hormones are responsible for the release of thyroid hormone?

Thyrotropin-releasing hormone (TRH) and thyroid-stimulating hormone (TSH) Signup and view all the answers

How do T3 and T4 hormones enter the target cells?

Diffusion across the plasma membrane Signup and view all the answers

What kind of mechanism is responsible for maintaining TH levels within homeostatic limits?

Negative feedback mechanism Signup and view all the answers

What role does the hypothalamus play regarding thyroid hormone?

It is the ultimate control center for metabolic rate. Signup and view all the answers

What hormone secretion is inhibited when T3 concentration is elevated in the blood?

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

Which condition is characterized by a slower metabolic rate due to reduced levels of TH?

Hypothyroidism Signup and view all the answers

What is the most prevalent cause of hypothyroidism?

Hashimoto’s Disease Signup and view all the answers

What treatment is commonly prescribed for hypo-functioning thyroid conditions?

Synthetic TH (Synthroid®) Signup and view all the answers

Which of the following is a result of elevated levels of TH in the body?

Faster metabolic rate Signup and view all the answers

In Graves’ Disease, what is the mechanism by which hyperthyroidism occurs?

Antibodies stimulate TSH receptors Signup and view all the answers

Which pathway is NOT involved in the regulation of TH levels?

Adrenaline regulation from the adrenal glands Signup and view all the answers

Which effect does decreased TH have on the body's ability to perform homeostatic functions?

Decreases metabolic rate Signup and view all the answers

What symptom is not commonly associated with Type II diabetes?

Severe headaches Signup and view all the answers

What is the primary reason for the low levels of TRH and TSH in patients with Graves' disease?

Elevated thyroid hormone levels inhibit their release. Signup and view all the answers

Which complication is a long-term risk of poorly managed diabetes?

Kidney dysfunction Signup and view all the answers

What is the primary role of testosterone in males?

Promoting sperm production Signup and view all the answers

Which structure is responsible for producing cortisol?

Adrenal cortex Signup and view all the answers

Which hormone is significantly associated with the menstrual cycle in females?

Estrogen Signup and view all the answers

What is a hallmark characteristic of Graves' disease related to the eyes?

Protrusion of the eyes Signup and view all the answers

What is one of the primary functions of cortisol in the body?

Mobilize stored nutrients for energy Signup and view all the answers

Which hormone is released by the anterior pituitary gland as part of the HPG axis?

Follicle-stimulating hormone Signup and view all the answers

What is one of the effects of estrogen in both sexes?

Regulation of body temperature Signup and view all the answers

When are cortisol levels typically low, and melatonin levels high?

During nighttime Signup and view all the answers

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

Triggering ovulation in females Signup and view all the answers

What effect does chronic stress have on the immune system?

Diminishes immune response Signup and view all the answers

In which organ is testosterone predominantly produced in males?

Testes Signup and view all the answers

What physiological changes occur in the body during stress responses?

Mobilization of nutrients and increased metabolic rates Signup and view all the answers

Which of the following glands is involved in producing short-term stress hormones?

Adrenal medulla Signup and view all the answers

What is the primary function of glucagon in the body?

To stimulate the liver to release glucose Signup and view all the answers

Which hormone is responsible for inhibiting the breakdown of glycogen in the liver?

Insulin Signup and view all the answers

During a fight or flight response, which of the following is NOT a result of epinephrine (E) and norepinephrine (NE) release?

Decreased respiratory rate Signup and view all the answers

What characterizes Type I diabetes?

Has an autoimmune component Signup and view all the answers

Which statement about insulin is true?

It stimulates muscle cells to take in glucose. Signup and view all the answers

What is a common symptom of Type I diabetes?

Frequent urination Signup and view all the answers

What lifestyle factors are primarily associated with the onset of Type II diabetes?

Poor diet and sedentary lifestyle Signup and view all the answers

What is the role of the adrenal medulla during short-term stress?

To release epinephrine and norepinephrine Signup and view all the answers

Study Notes

Endocrine Glands and Tissues

The endocrine system includes the pineal gland, hypothalamus, pituitary gland (anterior and posterior), thyroid gland, adrenal glands, pancreas, and gonads (testes and ovaries).

Thyroid Gland

Butterfly-shaped, located in front of the trachea, below the larynx.
Releases two hormones, Thyroid hormone (TH) and Calcitonin, calcitonin regulates calcium levels in blood.
TH regulates metabolic rate.
TH has two forms, T3 and T4, and differs in the number of iodine atoms.
Iodine from the diet is required to make TH, and salt is often iodized.
TH is hydrophobic and transported in blood plasma bound to proteins. Released TH enters cells, and binds to intracellular receptors triggering a nuclear response in almost every cell.
The final concentration of TH is regulated by negative feedback.
High levels of TH inhibit the secretion of TRH from the hypothalamus.
Low levels of TH stimulate the secretion of TRH from the hypothalamus.

Thyroid Hormone (TH)

TH (T3 and T4) regulates metabolic rate and heat production.
TH increases energy use from glucose and lipids, generating ATP in mitochondria and protein synthesis within the cells.

Control of TH Release

The hypothalamus releases TRH (thyroid releasing hormone).
TRH stimulates the anterior pituitary to release TSH (thyroid stimulating hormone).
TSH stimulates the thyroid gland to release TH.
TH regulates its own release through negative feedback.

Thyroid Disorders

Hypothyroidism (slow metabolism): Reduced levels of TH released into blood. Causes include problems with the hypothalamus, pituitary, or thyroid gland. Symptoms include fatigue, memory impairment, depression, swollen face, weight gain, dry skin, and muscle cramps. Hashimoto's disease is a common cause of hypothyroidism.
Hyperthyroidism (fast metabolism): Elevated levels of TH released into blood. Causes include problems with the hypothalamus, pituitary, or thyroid gland. Symptoms include nervousness, irritability, insomnia, depression, weight loss, feeling hungry, diarrhea, and warm skin. Graves' disease can cause hyperthyroidism.

4. Adrenal Glands

Small glands located on top of each kidney.
Consist of two regions:
- Adrenal cortex: Produces steroid hormones, including male and female sex hormones and stress hormones like cortisol (for long-term stress).
- Adrenal medulla: Releases hormones that respond to short-term stress, like epinephrine (adrenaline) and norepinephrine.

Stress Responses

Enable body adaptation by mobilizing nutrients, increasing metabolic rates, and increasing nutrient and oxygen delivery to cells.
Suppressing bodily functions not useful in dealing with a stressor (e.g., decreasing digestive and immune activity).
Short-term stress responses differ from long-term responses.

Cortisol

Released daily, especially in the morning, in response to melatonin variations (part of a circadian rhythm).
Prepares the body for activity by mobilizing nutrients.
Suppresses immune function.
A part of the long-term stress response leading to adaptation.

5. Pancreas

Located behind the stomach.
Produces two hormones that regulate blood glucose levels:
- Glucagon: Increases blood glucose.
- Insulin: Decreases blood glucose.
Glucose is a crucial fuel for cellular respiration.

Glucagon and Insulin

Antagonistic hormones that work opposite to each other to maintain blood glucose homeostasis.
Glucagon: Stimulates liver to convert glycogen to glucose and release it into the bloodstream.
Insulin: Inhibits glycogen breakdown in liver cells, stimulates muscle and adipose cells to absorb glucose from the bloodstream.

Diabetes Mellitus

A chronic metabolic disorder characterized by high blood glucose levels (hyperglycemia).
Type I diabetes: Autoimmune disorder damaging insulin-producing cells, requiring insulin injections.
Type II diabetes: Body becomes resistant to insulin and may involve poor diet, sedentary lifestyle, or obesity.

6. Gonads (Testes and Ovaries)

Testes in males and ovaries in females produce gametes and sex hormones. (sex hormones for reproduction).
The hypothalamus, pituitary, and gonads work together through the HPG axis releasing these sex hormones.

Testosterone

Produced in both sexes but higher in males in the testes.
Important for sperm production, male characteristics (genitals, secondary sex characteristics), and sex drive.

Estrogen

Produced in both sexes but higher in females in the ovaries.
Important for menstrual cycle, female reproductive structures, secondary sex characteristics, and uterine lining preparation for implantation.

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Description

This quiz provides an overview of the endocrine system, focusing on various glands including the pineal, hypothalamus, pituitary, thyroid, adrenal glands, and pancreas. It highlights the structure and function of the thyroid gland, the hormones it releases, and the mechanisms of hormone regulation in the body.