chapter 16 study guide: endocrine system

What is the endocrine system?

A system of glands that release hormones into the bloodstream to regulate body functions such as growth, metabolism, reproduction, and stress responses.

What are hormones?

Chemical messengers released by endocrine cells into the blood that affect specific target cells or organs.

What is an endocrine gland?

A ductless gland that releases hormones into the bloodstream or surrounding fluid.

What is an exocrine gland?

A gland that releases its products through ducts onto a body surface or into a body cavity, such as sweat or saliva glands.

What is the difference between endocrine and exocrine glands?

Endocrine glands are ductless and release hormones into the blood. Exocrine glands use ducts to deliver substances such as sweat, saliva, or digestive enzymes.

What is the pituitary gland?

A small, pea-sized gland beneath the hypothalamus that releases hormones regulating growth, reproduction, water balance, and other endocrine glands.

Why is the pituitary gland called the master gland?

It releases several hormones that control other endocrine glands, including the thyroid gland and adrenal cortex.

Why can the hypothalamus be considered the master endocrine regulator?

The hypothalamus controls the anterior pituitary through releasing and inhibiting hormones and controls the posterior pituitary through nerve connections. It coordinates endocrine activity with the nervous system.

Where is the pituitary gland located?

At the base of the brain, just below the hypothalamus, connected by the infundibulum.

What is the infundibulum?

The stalk connecting the hypothalamus to the pituitary gland.

What is the hypothalamic-hypophyseal tract?

A bundle of nerve fibers that connects the hypothalamus to the posterior pituitary and carries nerve impulses from hypothalamic neurons.

What is the anterior pituitary?

The front lobe of the pituitary gland that produces and secretes hormones in response to hypothalamic signals.

What is the posterior pituitary?

The back lobe of the pituitary gland, which stores and releases ADH and oxytocin made by neurons in the hypothalamus.

Why is the posterior pituitary not considered a true hormone-producing endocrine gland?

It does not synthesize its own hormones. It stores and releases ADH and oxytocin produced by the hypothalamus.

What are the major hormones of the anterior pituitary?

Growth hormone (GH), thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prolactin (PRL).

What does growth hormone (GH) do?

Stimulates body growth, especially in bones and skeletal muscles, partly by promoting growth factors produced by the liver.

What does thyroid-stimulating hormone (TSH) do?

Stimulates the thyroid gland to produce and release thyroid hormones.

What does adrenocorticotropic hormone (ACTH) do?

Stimulates the adrenal cortex to release hormones, especially cortisol.

What does prolactin (PRL) do?

Stimulates milk production by the breasts.

What does antidiuretic hormone (ADH) do?

Helps the kidneys conserve water, reducing water loss in urine.

What does oxytocin do?

Stimulates uterine contractions during childbirth and milk ejection during breastfeeding.

What is the thyroid gland?

An endocrine gland in the neck that produces thyroid hormones to regulate metabolism and calcitonin, which can help lower blood calcium.

What are the major metabolic hormones produced by the thyroid gland?

Thyroxine (T4) and triiodothyronine (T3), which increase metabolic activity and support growth and development.

What does thyroxine (T4) do?

Helps regulate the body's metabolic rate, energy use, growth, and development.

What does calcitonin do?

Helps lower blood calcium levels by inhibiting bone breakdown, although its role in everyday calcium regulation is relatively minor.

What are the parathyroid glands?

Small glands located on the back of the thyroid gland that produce parathyroid hormone (PTH).

What does parathyroid hormone (PTH) do?

Raises blood calcium levels by promoting calcium release from bone, calcium reabsorption by the kidneys, and activation of vitamin D to increase intestinal calcium absorption.

What is the most important regulator of blood calcium levels according to the study guide?

Parathyroid hormone (PTH).

What is the pancreas?

An organ that has both endocrine and exocrine functions. Its endocrine cells release insulin and glucagon to regulate blood glucose.

What does insulin do?

Lowers blood glucose by helping cells take up glucose and encouraging the storage of glucose as glycogen.

What does glucagon do?

Raises blood glucose by stimulating the liver to break down glycogen and produce and release glucose.

What is the difference between insulin and glucagon?

Insulin lowers blood glucose, while glucagon raises blood glucose.

Which hormone helps prevent blood sugar from dropping too low?

Glucagon raises blood glucose when it falls.

What are the adrenal glands?

Glands located above the kidneys. Each has an outer adrenal cortex and an inner adrenal medulla.

What is the adrenal cortex?

The outer part of the adrenal gland that produces steroid hormones, including cortisol, aldosterone, and adrenal androgens.

What is the adrenal medulla?

The inner part of the adrenal gland that releases epinephrine and norepinephrine during sympathetic nervous system activation.

Why is the adrenal medulla considered part of the sympathetic nervous system?

It functions like a modified sympathetic ganglion and releases epinephrine and norepinephrine during the fight-or-flight response.

What does cortisol do?

Helps the body respond to prolonged stress, increases blood glucose availability, and affects metabolism and inflammation.

What does aldosterone do?

Promotes sodium reabsorption and potassium excretion by the kidneys. Water follows sodium, helping maintain blood volume and pressure.

What are epinephrine and norepinephrine?

Hormones released by the adrenal medulla that prepare the body for fight-or-flight responses by increasing alertness and affecting heart rate, blood pressure, and energy availability.

What is the thymus gland?

An endocrine and immune organ that produces hormones involved in T-cell development and normal immune function.

Why can thymus atrophy affect immune responses in older adults?

The thymus is important for T-cell maturation. As it shrinks with age, production of new T cells decreases, which can weaken some immune responses.

What is the pineal gland?

A small endocrine gland in the brain that produces melatonin.

What does melatonin do?

Helps regulate the body's sleep-wake cycle and circadian rhythm, especially in response to darkness.

Which hormone may help the body adjust its sleep timing after crossing time zones?

Melatonin is involved in circadian rhythm regulation.

What is diabetes mellitus?

A disorder involving insufficient insulin production, impaired insulin action, or both, leading to elevated blood glucose.

What are the three cardinal signs of diabetes mellitus?

Polyuria (frequent or excessive urination), polydipsia (excessive thirst), and polyphagia (excessive hunger).

What does polyuria mean?

Excessive urination.

What does polydipsia mean?

Excessive thirst.

What does polyphagia mean?

Excessive hunger.

Which is NOT a cardinal sign of diabetes mellitus: polyuria, polydipsia, polyphagia, or polycythemia?

Polycythemia. The three cardinal signs are polyuria, polydipsia, and polyphagia.

Why can a person with diabetes feel shaky, dizzy, or confused?

These symptoms can occur when blood glucose becomes too low, a condition called hypoglycemia.

Why might hard candy help a conscious person experiencing hypoglycemia?

Candy contains sugar that can be absorbed quickly and raise blood glucose. If the person is awake and able to swallow safely, fast-acting sugar is an appropriate response.

What should you do if a person with suspected low blood sugar is unconscious or cannot swallow safely?

Do not give food or drink by mouth. Call emergency services and use prescribed emergency glucagon if available and you are able to administer it.

What is pituitary dwarfism?

Short stature caused by insufficient growth hormone during childhood, resulting in reduced growth before the growth plates close.

What is gigantism?

Excessive growth caused by too much growth hormone during childhood, while the growth plates are still open.

What is acromegaly?

Enlargement of the hands, feet, jaw, and other facial bones caused by excess growth hormone in adulthood, after the growth plates have closed.

What causes gigantism and acromegaly?

Both result from excess growth hormone, commonly due to a pituitary tumor. Gigantism occurs before growth plates close; acromegaly occurs after they close.

What is the difference between gigantism and acromegaly?

Gigantism causes excessive height growth in children with open growth plates. Acromegaly causes enlargement of the hands, feet, and facial bones in adults after growth plates have closed.

What is Graves' disease?

An autoimmune disorder in which antibodies stimulate the thyroid gland, commonly causing excessive thyroid hormone production and hyperthyroidism.

What is Cushing's disease according to the study guide's matching section?

It is matched with hypersecretion of the adrenal cortex. More precisely, Cushing disease is caused by excess ACTH from a pituitary tumor, which stimulates excess cortisol production by the adrenal cortex.

What is the difference between hyposecretion and hypersecretion?

Hyposecretion means a gland produces too little hormone; hypersecretion means it produces too much.

What happens when growth hormone is too low during childhood?

Growth may be reduced, potentially causing pituitary dwarfism if growth hormone deficiency is responsible.

What happens when growth hormone is too high during childhood?

It can cause gigantism because the long bones can continue growing while growth plates remain open.

Why do people stop increasing in height as they age?

The growth plates at the ends of long bones gradually close and ossify after puberty. Once they close, the bones can no longer grow longer.

Why does growth hormone treatment need to occur before growth plates close?

Growth hormone can stimulate lengthwise bone growth only while the growth plates are open. After closure, it cannot increase height.

What hormone might be prescribed to a child with growth hormone deficiency?

Growth hormone, if testing confirms the deficiency and treatment is appropriate.

What is the likely diagnosis for a 17-year-old who is much shorter than expected and is prescribed growth hormone?

Possible growth hormone deficiency, sometimes called pituitary dwarfism in the study guide. If the growth plates are still open, treatment may allow additional height growth.

Why might a 17-year-old receiving growth hormone still reach more of their growth potential?

If the growth plates have not yet closed, growth hormone treatment may promote additional bone growth. The outcome depends on the cause of short stature and remaining growth potential.

What is the likely diagnosis for an adult with enlarged hands, feet, skull, nose, and lower jaw?

Acromegaly, commonly caused by excess growth hormone from a pituitary tumor after the growth plates have closed.

Why might surgery be recommended for acromegaly?

If a pituitary tumor is producing too much growth hormone, surgery may remove or reduce the tumor and help control hormone levels.

What is hypersecretion of adrenal androgens?

Excess production of androgen hormones by the adrenal cortex, which can cause increased body hair and other signs of masculinization in females.

What hormonal dysfunction can cause excessive body hair, a deep voice, and an enlarged clitoris in a woman?

Excess androgen production, potentially from the adrenal cortex or ovaries. The symptoms require medical evaluation to identify the cause.

What is negative feedback in the endocrine system?

A control mechanism in which a hormone's effects reduce the original stimulus for its release, helping keep body conditions stable.

How does the hypothalamus control the anterior pituitary?

It releases or inhibits regulatory hormones that travel through blood vessels to control hormone secretion by the anterior pituitary.

How does the hypothalamus control the posterior pituitary?

Hypothalamic neurons produce ADH and oxytocin and transport them down nerve fibers to the posterior pituitary for storage and release.

How does ACTH help the body respond to stress?

The anterior pituitary releases ACTH, which stimulates the adrenal cortex to release cortisol. Cortisol helps maintain energy availability during stress.

Which gland produces the body's major metabolic hormones?

The thyroid gland, which produces T3 and T4.

Which gland produces hormones that regulate blood glucose?

The pancreas, through insulin and glucagon.

Which gland is the primary regulator of blood calcium?

The parathyroid glands, through parathyroid hormone (PTH).

Which gland produces hormones that stimulate other endocrine glands and is about the size of a pea?

The pituitary gland (hypophysis).

Which gland is part of the sympathetic nervous system?

The adrenal medulla.

Which gland produces hormones that support normal immune development?

The thymus gland.

Which gland produces melatonin?

The pineal gland.

What is the main difference between the anterior and posterior pituitary?

The anterior pituitary makes and releases its own hormones in response to hypothalamic signals. The posterior pituitary stores and releases ADH and oxytocin made by the hypothalamus.

How do endocrine glands communicate with their target organs?

They release hormones into the blood. Hormones reach target cells that have the appropriate receptors and change their activity.

Why can the same hormone affect some cells but not others?

Only cells with the appropriate receptors respond directly to that hormone.