endocrine system

What are the two systems that communicate with neurotransmitters and hormones?

The nervous system and the endocrine system.

What is the primary focus of the chapter on the endocrine system?

The chapter discusses the endocrine system, its functions, and its role in adaptation to stress.

What are hormones?

Chemical messengers that travel in the bloodstream to stimulate physiological responses in target cells.

What distinguishes endocrine glands from exocrine glands?

Endocrine glands have no ducts and secrete hormones directly into the bloodstream, while exocrine glands have ducts that carry secretions to an epithelial surface.

What are the four principal mechanisms of communication between cells in the body?

Gap junctions, neurotransmitters, paracrine hormones, and hormones.

What role do gap junctions play in cellular communication?

They allow signaling molecules, nutrients, and electrolytes to move directly from cell to cell.

How do neurotransmitters function in the nervous system?

They are released from neurons to travel across the synaptic cleft to a second cell.

What are paracrine hormones?

Hormones secreted into tissue fluids that affect nearby cells.

What is endocrinology?

The study of the endocrine system and the diagnosis and treatment of its disorders.

Name some major organs of the endocrine system.

Pineal gland, hypothalamus, pituitary gland, thyroid gland, thymus, adrenal gland, pancreas, parathyroid glands, ovaries, and testes.

What is the difference in the effects of endocrine and exocrine glands?

Endocrine glands have internal secretions with intracellular effects, while exocrine glands have external secretions with extracellular effects.

How do the nervous and endocrine systems compare in terms of speed of response?

The nervous system reacts quickly (1 to 10 ms) and stops quickly, while the endocrine system reacts slowly (hormones release in seconds or days) with effects that may last for weeks.

What is the area of effect for the nervous system compared to the endocrine system?

The nervous system has targeted and specific effects (one organ), while the endocrine system has general, widespread effects (many organs).

What is a unique characteristic of some hormones in relation to neurotransmitters?

Several chemicals function as both hormones and neurotransmitters, such as norepinephrine and dopamine.

What is the role of neuroendocrine cells?

They are neurons that release their secretions (hormones) into the bloodstream.

How do the nervous and endocrine systems regulate each other?

Neurons can trigger hormone secretion, and hormones can stimulate or inhibit neuronal activity.

What are target organs or cells in the context of the endocrine system?

Organs or cells that have receptors for a hormone and can respond to it.

What is the effect of norepinephrine and glucagon on the liver?

Both cause glycogen hydrolysis in the liver.

What is the adaptation response of the nervous system to long-term stimuli?

The nervous system's response declines and adapts quickly.

What is the adaptation response of the endocrine system to long-term stimuli?

The endocrine system's response persists and adapts slowly.

What is the significance of the hypothalamus in the endocrine system?

It plays a crucial role in regulating the endocrine system and hormone secretion.

What is the function of the pituitary gland in the endocrine system?

It is often referred to as the 'master gland' because it regulates other endocrine glands.

What is the role of the adrenal gland?

It produces hormones that help regulate metabolism, immune response, and stress.

What is the function of the pancreas in the endocrine system?

It regulates blood sugar levels by secreting insulin and glucagon.

What are the two main systems that regulate body functions?

The nervous system and the endocrine system.

What is the role of neurotransmitters?

They transmit nerve impulses between neurons and target cells.

What is the anatomical relationship between the hypothalamus and the pituitary gland?

The pituitary gland is suspended from the hypothalamus by a stalk called the infundibulum.

What is the size and shape of the pituitary gland?

It is the size and shape of a kidney bean and is housed in the sella turcica of the sphenoid bone.

What are the two main parts of the pituitary gland?

The adenohypophysis (anterior pituitary) and the neurohypophysis (posterior pituitary).

What is the embryonic origin of the adenohypophysis?

It arises from the hypophyseal pouch, which is an outgrowth of the pharynx.

What is the embryonic origin of the neurohypophysis?

It is a downgrowth from the brain.

What constitutes the anterior pituitary?

The adenohypophysis constitutes three-quarters of the pituitary and has two segments: the anterior lobe (pars distalis) and the pars tuberalis.

How is the adenohypophysis linked to the hypothalamus?

It is linked by the hypophyseal portal system, which connects primary capillaries in the hypothalamus to secondary capillaries in the adenohypophysis.

What regulates the cells of the adenohypophysis?

Hypothalamic hormones regulate the cells of the adenohypophysis.

What constitutes the posterior pituitary?

The neurohypophysis constitutes the posterior one-quarter of the pituitary and has three parts: median eminence, infundibulum, and the posterior lobe (pars nervosa).

What type of tissue is the neurohypophysis made of?

It is made of nerve tissue and is not a true gland.

How do hypothalamic neurons interact with the neurohypophysis?

Nerve cell bodies in the hypothalamus pass down the stalk as the hypothalamo-hypophyseal tract and end in the posterior lobe.

What happens to hormones secreted by hypothalamic neurons?

They are stored in the neurohypophysis until released into the bloodstream.

What are the functions regulated by the hypothalamus?

It regulates primitive functions such as water balance, thermoregulation, sex drive, and childbirth.

What is the expected learning outcome regarding the hormones produced by the hypothalamus?

Students should be able to list the hormones produced by the hypothalamus and each lobe of the pituitary, and identify their functions.

What is the function of growth hormone?

Growth hormone stimulates growth, cell reproduction, and cell regeneration.

What is the significance of the hypophyseal portal system?

It allows for the direct transport of hormones from the hypothalamus to the adenohypophysis.

What is the role of the infundibulum?

The infundibulum connects the hypothalamus to the pituitary gland.

What is the primary function of the pituitary gland?

The pituitary gland controls various endocrine functions by releasing hormones that regulate other glands.

What is the anatomical significance of the sella turcica?

It is the bony structure that houses the pituitary gland.

What is the primary function of the hypothalamic hormones?

They regulate the anterior pituitary and influence its secretion.

What are the two types of hormones released into the posterior pituitary from the hypothalamus?

Oxytocin (OT) and Antidiuretic hormone (ADH).

What hormones are produced in the anterior lobe of the pituitary gland?

Follicle-stimulating hormone (FSH), Luteinizing hormone (LH), Thyroid-stimulating hormone (TSH), Adrenocorticotropic hormone (ACTH), Prolactin (PRL), and Growth hormone (GH).

What is the role of Gonadotropin-releasing hormone (GnRH)?

It stimulates the secretion of FSH and LH from the anterior pituitary.

What is the function of Thyrotropin-releasing hormone (TRH)?

It stimulates the secretion of Thyroid-stimulating hormone (TSH) from the anterior pituitary.

What does Corticotropin-releasing hormone (CRH) do?

It stimulates the secretion of Adrenocorticotropic hormone (ACTH) from the anterior pituitary.

What is the role of Prolactin-inhibiting hormone (PIH)?

It inhibits the secretion of prolactin from the anterior pituitary.

What is the function of Somatostatin?

It inhibits the secretion of Growth hormone (GH) and Thyroid-stimulating hormone (TSH) from the anterior pituitary.

What hormones are secreted by the anterior pituitary?

FSH, LH, TSH, ACTH, PRL, and GH.

What is the role of the hypophyseal portal system?

It transports hypothalamic hormones to the anterior pituitary.

Which nuclei produce Oxytocin (OT)?

The right and left paraventricular nuclei.

Which nuclei produce Antidiuretic hormone (ADH)?

The supraoptic nuclei.

What is the function of Follicle-stimulating hormone (FSH)?

It stimulates secretion of ovarian sex hormones, development of ovarian follicles, and sperm production.

What does Luteinizing hormone (LH) stimulate?

It stimulates ovulation, corpus luteum secretion of progesterone, and testosterone secretion by testes.

What is the role of Thyroid-stimulating hormone (TSH)?

It stimulates secretion of thyroid hormones.

What does Adrenocorticotropic hormone (ACTH) stimulate?

It stimulates the adrenal cortex to secrete glucocorticoids.

What is the function of Prolactin (PRL)?

It stimulates mammary glands to synthesize milk and enhances testosterone secretion by testes.

What does Growth hormone (GH) stimulate?

It stimulates mitosis and cellular differentiation.

What is the Pars Intermedia and its function?

It is present in the fetus, absent in adults, and produces melanocyte-stimulating hormone in animals.

What is proopiomelanocortin (POMC)?

A precursor processed within the pituitary to yield smaller fragments like ACTH and endorphins.

What is the significance of the hypothalamic-releasing and -inhibiting hormones?

They regulate the secretion of hormones from the anterior pituitary.

What is the difference between the anterior and posterior pituitary in terms of hormone synthesis?

The anterior pituitary synthesizes hormones, while the posterior pituitary stores and releases hormones produced by the hypothalamus.

What is the floor of the third ventricle of the brain?

Hypothalamus

What hormones are produced in the hypothalamus and transported to the posterior lobe of the pituitary gland?

Oxytocin and Antidiuretic hormone (ADH)

What is the function of Antidiuretic hormone (ADH)?

Increases water retention, reduces urine volume, and prevents dehydration.

Why is ADH also called vasopressin?

Because it can cause vasoconstriction.

What is the role of oxytocin during childbirth?

Stimulates labor contractions.

How does oxytocin affect emotional bonding?

Promotes feelings of sexual satisfaction and emotional bonding between partners.

What triggers the release of oxytocin during lactation?

Suckling by the infant.

What regulates the secretion rates of hormones from the pituitary gland?

Hypothalamus, other brain centers, and feedback from target organs.

What is the neuroendocrine reflex?

Hormone release in response to nervous system signals.

What is negative feedback in hormone regulation?

Increased target organ hormone levels inhibit the release of hormones.

What is positive feedback in hormone regulation?

Stimulatory effects, such as stretching of the uterus increasing oxytocin release.

What are the effects of Growth Hormone (GH) on body tissues?

Widespread effects, especially on cartilage, bone, muscle, and fat.

What does GH induce the liver to produce?

Growth stimulants, specifically insulin-like growth factors (IGF-I and IGF-II).

What is the half-life of Growth Hormone (GH)?

6 to 20 minutes.

What is the half-life of IGF-I?

About 20 hours.

How does GH affect protein synthesis?

Increases transcription of cells, production of mRNA, and amino acid uptake.

What is the carbohydrate metabolism effect of GH?

Glucose-sparing effect, mobilizes fatty acids, reduces dependence on glucose.

How does GH influence electrolyte balance?

Promotes Na+, K+, and Cl− absorption and Ca2+ retention by kidneys.

When is GH secretion highest?

During the first 2 hours of sleep.

What factors can cause a peak in GH levels?

Vigorous exercise.

How does aging affect GH levels?

GH levels decline gradually with age.

What changes occur in body composition with age?

Decrease in bone and muscle mass, increase in fat.

What are the expected learning outcomes regarding other endocrine glands?

Describe the structure and location of the remaining endocrine glands.

What ions are promoted for absorption by electrolyte balance?

Sodium (Na+), Potassium (K+), and Chloride (Cl−)

What role does growth hormone (GH) play in the body?

It influences bone growth, thickening, and remodeling, especially during childhood and adolescence.

When is growth hormone secretion highest?

During the first 2 hours of sleep and can peak in response to vigorous exercise.

How do growth hormone levels change with age?

GH levels decline gradually with age, averaging 6 ng/mL during adolescence and 1.5 ng/mL in old age.

What physical changes occur in the body by age 30?

Average adult body composition is 10% bone, 30% muscle, and 20% fat.

What physical changes occur in the body by age 75?

Average adult body composition is 8% bone, 15% muscle, and 40% fat.

What is the location of the pineal gland?

Attached to the roof of the third ventricle beneath the posterior end of the corpus callosum.

What happens to the pineal gland after age 7?

It undergoes involution, shrinking by 75% by the end of puberty.

What hormone does the pineal gland synthesize during the night?

Melatonin, synthesized from serotonin.

What is seasonal affective disorder (SAD) and when does it occur?

SAD occurs in winter or northern climates, characterized by depression, sleepiness, irritability, and carbohydrate craving.