Week 12 - Chapter 18: The Endocrine System
What system controls homeostasis using hormones that act slowly on distant parts of the body?
Endocrine system
What is the difference between exocrine and endocrine glands?
Exocrine glands secrete through ducts into cavities or onto surfaces; endocrine glands secrete hormones into interstitial fluid
Name five classic endocrine glands
Pituitary, thyroid, parathyroid, suprarenal, and pineal glands.
What determines a hormone's target cells?
The presence of specific receptors for the hormone
What are the two chemical classes of hormones?
Lipid-soluble and water-soluble hormones
How do lipid-soluble hormones travel in the bloodstream?
Bound to transport proteins synthesized by the liver
What three factors control hormone secretion?
Nervous system signals, chemical changes in the blood, and other hormones
What type of feedback system regulates most hormone secretions?
Negative feedback systems
What is the primary role of the hypothalamus in the endocrine system?
It links the nervous and endocrine systems and regulates growth, metabolism, and homeostasis.
What are the two portions of the pituitary gland?
Anterior pituitary (glandular portion) and posterior pituitary (nervous portion)
What are the main thyroid hormones?
Thyroxine (T4) and triiodothyronine (T3)
What regulates the secretion of thyroid hormones?
TRH (thyrotropin-releasing hormone) and TSH (thyroid-stimulating hormone)
What does parathyroid hormone regulate?
Homeostasis of calcium, magnesium, and phosphate ions
What triggers parathyroid hormone secretion?
Blood calcium levels
What hormones are secreted by the suprarenal medulla?
Epinephrine and norepinephrine
What are the four types of pancreatic islet cells?
Alpha, beta, delta, and F cells
What is the function of glucagon?
Glucagon increases blood glucose
What hormones are produced by the ovaries?
Estrogens, progesterone, and inhibin
What hormone is produced by the testes?
Testosterone and inhibin
What hormone is secreted by the pineal gland, and what does it regulate?
Melatonin; it regulates the biological clock
What hormones are secreted by the thymus, and what is their function?
Thymosin, thymic humoral factor, thymic factor, and thymopoietin; they promote T cell maturation.
What are the three stages of the general adaptation syndrome?
1. Fight or flight Stage: The hypothalamus activates the adrenal glands, releasing adrenaline and cortisol to prepare the body for the fight-or-flight response.
2. Resistance Stage: The body maintains elevated cortisol levels to sustain energy and cope with prolonged stress.
3. Exhaustion Stage: Prolonged stress depletes resources, leading to reduced hormone production, fatigue, and potential health issues.
What hormone is released during the resistance stage and helps resist stress?
Cortisol
The control center
The hypothalamus
The master gland
The pituitary gland
The pituitary gland secretes ____ hormones
8; 6 from anterior and 2 from posterior
The hypothalamus secretes 9 hormones that regulate:
Growth, development, metabolism, homeostasis
These hormones (insulin, adrenaline, thyroid-stimulating) are:
- Soluble in water, travel freely in bloodstream without the need for carriers
- Effects are rapid and short
- Bind to receptors on surface of target cells
Water-soluble hormones
These hormones (steroids, cortisol, estrogen, thyroid) are:
- Not soluble in water
- Require carrier proteins in blood for transport
- Bind to intracellular receptors
- Effects are slower but longer lasting
Fat-soluble hormones
The anterior pituitary secretes the following hormones:
1. Growth hormone (GH): Stimulates growth/cell reproduction.
2. Thyroid-stimulating hormone (TSH): Stimulates the thyroid gland to produce thyroid hormones.
3. Adrenocorticotropic hormone (ACTH): Stimulates the adrenal glands to release cortisol.
4. Follicle-stimulating hormone (FSH): Stimulates the growth of ovarian follicles in females and sperm production in males.
5. Luteinizing hormone (LH): Triggers ovulation in females and testosterone production in males.
6. Prolactin (PRL): Stimulates milk production in females after childbirth
7. Melanocyte-stimulating hormone (MSH): Regulates the production of melanin in the skin.
The posterior pituitary stores and releases hormones produced by the hypothalamus:
1. Oxytocin: Stimulates uterine contractions during labor
2. Antidiuretic hormone (ADH): Regulates water balance by promoting water reabsorption in the kidneys
The hypothalamus produces hormones that regulate the pituitary gland:
1. Thyrotropin-releasing hormone (TRH): Stimulates the release of TSH from the anterior pituitary.
2. Corticotropin-releasing hormone (CRH): Stimulates the release of ACTH from the anterior pituitary.
3. Gonadotropin-releasing hormone (GnRH): Stimulates the release of FSH and LH from the anterior pituitary.
4. Growth hormone-releasing hormone (GHRH): Stimulates the release of GH from the anterior pituitary.
5. Somatostatin: Inhibits the release of GH and TSH.
6. Dopamine: Inhibits the release of prolactin from the anterior pituitary.
7. Antidiuretic hormone (ADH) and Oxytocin: Stored and released by the posterior pituitary.
Main hormones that control calcium levels in the body:
Parathyroid hormone (PTH), Calcitonin, Vitamin D
______ is an enlargement of the thyroid gland and may be associated with hyperthyroidism, hypothyroidism, or iodine deficiency
Goiter
High levels of circulating cortisol or tumors (adrenal cortex, pituitary gland) is called ______ syndrome.
Cushing’s
Hypersecretion vs. hyposecretion
Hypersecretion is the excessive production of hormones, leading to symptoms like rapid metabolism or organ enlargement, while hyposecretion is the insufficient production of hormones, causing symptoms such as fatigue and slowed metabolism.
General Adaptation Syndrome (GAS) describes the body's physiological response to:
Stress
GAS is regulated by the:
Hypothalamus-pituitary-adrenal (HPA) axis.