Ch 9 Endocrine Lecture Flashcards

Vocabulary flashcards covering key endocrine system terms, glands, hormones, mechanisms, and feedback processes from the notes.

Endocrine system

System that uses hormones circulated through the bloodstream to regulate growth, development, aging, and homeostasis; slower signals than the nervous system and often works with it.

Hypothalamus

Brain region that links the nervous and endocrine systems; produces releasing and inhibiting hormones; has portal circulation to the anterior pituitary and stores oxytocin and ADH in the posterior pituitary.

Hypothalamic-pituitary portal circulation

Direct circulatory link from hypothalamus to the anterior pituitary; allows releasing/inhibiting hormones to control pituitary secretions.

Pituitary gland

Master gland that secretes many hormones; has an anterior lobe (adenohypophysis) and a posterior lobe (neurohypophysis).

Adenohypophysis (anterior pituitary)

Anterior lobe that releases hormones such as TSH, ACTH, LH, FSH, GH, prolactin, and MSH.

Neurohypophysis (posterior pituitary)

Posterior lobe that stores and releases oxytocin and ADH, produced by the hypothalamus.

Thyrotropin-releasing hormone (TRH)

Hypothalamic hormone that stimulates the anterior pituitary to secrete thyroid-stimulating hormone (TSH).

Thyroid-stimulating hormone (TSH)

Anterior pituitary hormone that stimulates the thyroid to produce T3 and T4.

Adrenocorticotropic hormone (ACTH)

Anterior pituitary hormone that stimulates the adrenal cortex to produce glucocorticoids.

Luteinizing hormone (LH)

Anterior pituitary hormone that stimulates gonads; in females triggers ovulation and estrogen/progesterone production; in males stimulates testosterone.

Follicle-stimulating hormone (FSH)

Anterior pituitary hormone that promotes maturation of eggs and sperm; gonadotropic.

Growth hormone (GH, somatotropin)

Anterior pituitary hormone that regulates growth and metabolism; influences protein synthesis and tissue growth.

Prolactin

Anterior pituitary hormone that initiates milk production after birth.

Melanocyte-stimulating hormone (MSH)

Anterior pituitary hormone associated with skin pigmentation.

Oxytocin

Posterior pituitary hormone that stimulates uterine contractions and milk ejection; also involved in bonding.

Antidiuretic hormone (ADH, vasopressin)

Posterior pituitary hormone that increases water reabsorption in kidneys, concentrating urine.

Pineal gland

Gland in the brain that stores and secretes melatonin, influencing sleep-wake cycles.

Melatonin

Hormone from the pineal gland that regulates the circadian rhythm and sleep–wake cycle.

Thyroid gland

Endocrine gland in the neck; produces thyroid hormones (T3 and T4) and calcitonin.

Thyroid hormones (T3 and T4)

T3 (triiodothyronine) and T4 (thyroxine); regulate cellular metabolism; T3 is the active form; T4 is the storage form converted to T3; iodine is essential.

Calcitonin

Thyroid hormone that lowers blood calcium by inhibiting bone resorption and promoting calcium storage in bone.

Parathyroid glands

Four small glands on the posterior thyroid; secrete parathyroid hormone to increase blood calcium when needed.

Parathyroid hormone (PTH)

Raises blood calcium by increasing bone resorption, increasing renal calcium reabsorption, and promoting calcitriol formation.

Calcitriol

Active form of vitamin D; increases calcium absorption from the gut and works with PTH to raise blood calcium.

Islets of Langerhans

Endocrine cell clusters in the pancreas that secrete insulin and glucagon to regulate blood glucose.

Pancreas (endocrine vs exocrine)

Gland with exocrine function (ducted digestive juices) and endocrine function (islets of Langerhans) releasing hormones into the blood.

Basal metabolic rate (BMR)

Rate of oxygen consumption at rest; influenced by thyroid hormones (e.g., T3).

Thyroid hormones mechanism (T3/T4)

T3 and T4 regulate metabolism; T3 is more active; T4 acts as storage and can be converted to T3; iodine is essential.

Calcitonin vs PTH

Calcitonin lowers blood calcium (bone storage) while PTH raises blood calcium (bone resorption, kidney activation, and intestinal absorption via calcitriol).

Sella turcica

Bony saddle in the skull where the pituitary sits; nickname for the Turkish saddle surrounding the pituitary.

Pituitary stalk

The connecting stalk between the hypothalamus and the pituitary; contains vessels and nerves linking the two.

Isthmus (thyroid isthmus)

The narrow part of the thyroid that connects the two lobes; lies over the voice box.

Parathyroid hormone action sites

PTH increases osteoclast activity, increases renal calcium reabsorption, and promotes calcitriol formation to raise blood calcium.

Osteoclast

Bone-resorbing cells activated by PTH to release calcium into the blood.

Osteoblast

Bone-forming cells (mentioned in contrast to osteoclasts in calcium regulation).

Water-soluble hormones

Hormones that dissolve in water; cannot cross the plasma membrane; use surface receptors and second messenger systems (e.g., cAMP).

Lipid-soluble hormones

Hormones that require carrier proteins in the blood; cross the plasma membrane and bind intracellular receptors to affect gene transcription.

Carrier proteins

Blood carriers for lipid-soluble hormones; help transport fats and steroid hormones through the bloodstream.

Second messenger system

Pathway where a water-soluble hormone binds a membrane receptor (first messenger) and triggers intracellular messengers (e.g., cAMP) to produce a response.

G protein

Intracellular protein activated by a membrane receptor; contributing to the production of cAMP and downstream effects.

Receptors

Proteins on target cells that bind to specific hormones; receptor density can range from 2,000 to 100,000 per cell and can be up- or down-regulated.

Synergistic effect

Two or more hormones work together to enhance a target cell response.

Antagonistic effect

Hormones with opposite effects (e.g., insulin lowers blood glucose, glucagon raises it).

Permissive effect

One hormone increases a target cell’s sensitivity to another hormone.

Negative feedback loop

A loop in which rising levels of a hormone inhibit further release; maintains homeostasis (e.g., blood glucose regulation).

Positive feedback loop

A loop in which a hormone release stimulates more release until a final event occurs (e.g., oxytocin during childbirth).