Endocrine System Quiz

Endocrine System Overview

• The endocrine system involves glands that secrete hormones, chemicals that regulate body functions
• Not all glands are part of the endocrine system
• Endocrine glands release hormones into intercellular spaces
• Each hormone molecule binds to a specific receptor on a target cell
• Hormones regulate body functions more slowly than nerve impulses

Learning Objectives

• Distinguish between endocrine and exocrine glands
• Define hormone, hypersecretion, and hyposecretion
• Identify and locate primary endocrine glands
• List major hormones produced by each gland
• Describe mechanisms of steroid and nonsteroid hormone action
• Explain negative and positive feedback mechanisms regulating hormone secretion
• Define and explain prostaglandins (PGs)
• Identify functions of major endocrine glands and hormones they release
• Describe conditions resulting from hyposecretion or hypersecretion (e.g., gigantism, diabetes insipidus, goiter, cretinism, diabetes mellitus, glycosuria)

Endocrine and Exocrine Glands

• Only endocrine glands are part of the endocrine system
• Endocrine glands secrete hormones into the bloodstream
• Hormones bind to specific receptors on target cells to trigger reactions

Mechanisms of Hormone Action

• Endocrine glands secrete hormones into the bloodstream
• Hypersecretion is too much hormone, hyposecretion is too little
• Hormones are slower-acting than nerve impulses for communication and control

Types of Hormones

• Two major classes: Nonsteroid hormones (proteins) and steroid hormones.
• Nonsteroid hormones bind to receptors on the target cell membrane, triggering a second messenger system
• Steroid hormones bind to receptors within the target cell nucleus, influencing DNA activity

Location of Endocrine Glands

• Shows locations of various endocrine glands (pineal, pituitary, parathyroid, thyroid, thymus, adrenals, pancreatic islets, ovaries, testes)

Mechanisms of Hormone Action (Continued)

• Nonsteroid hormones: Act as first messengers, binding to membrane receptors and triggering second messengers
• Steroid hormones: Affect DNA activity within the target cell nucleus. This is a slower process than nonsteroid hormone action.

Mechanism of Nonsteroid Hormone Action

• Shows a diagram illustrating the mechanism of nonsteroid hormone action, including the first messenger (protein hormone), membrane receptor, enzyme, ATP, cyclic AMP (cAMP) as a second messenger, and activation of other enzymes to regulate cellular activity.

Mechanism of Steroid Hormone Action

• Shows diagram illustrating how steroid hormones influence cellular activity by binding to receptors within the cell nucleus affecting DNA.

Regulation of Hormone Secretion

• Hormone secretion is controlled by feedback mechanisms.
• Some types of feedback mechanisms reverse the physiological changes; others amplify the changes (like oxytocin secretion during childbirth).
• Negative feedback mechanisms reverse the direction of a change
• Positive feedback mechanisms amplify a change

Negative Feedback Example

• Illustrates a diagram of how negative feedback regulates blood glucose levels.

Prostaglandins

• powerful substances found in various body tissues; act as tissue hormones acting on cells locally.
• Several types of prostaglandins exist (PGA, PGE, PGF).

Pituitary Gland

• Structure of the pituitary gland includes the adenohypophysis (anterior pituitary), neurohypophysis (posterior pituitary), sella turcica and pituitary stalk.
• Main hormones from the anterior pituitary include Thyroid stimulating hormone (TSH), Adrenocorticotropic hormone (ACTH), Follicle stimulating hormone (FSH), Luteinizing hormone (LH), Growth hormone (GH), and Prolactin (PRL).

Pituitary Gland (Continued)

• List of anterior pituitary hormones and their functions.
• Examples of anterior pituitary functions include TSH stimulating thyroid growth, ACTH stimulating adrenal growth, FSH initiating follicle growth in ovaries and stimulating sperm production, LH causing ovulation, GH stimulating growth, and PRL stimulating breast development and milk production.

Pituitary Gland (Continued)

• Posterior pituitary hormones and their functions.
• Examples of posterior pituitary functions include Antidiuretic hormone (ADH) or vasopressin influencing water reabsorption and Oxytocin influencing uterine contractions and milk release.

Hypothalamus

• The hypothalamus is involved in producing ADH and oxytocin
• Hormone secretion is regulated by nervous input
• The hypothalamus also regulates many body functions like temperature, appetite, and thirst.
• Hypothalamus also produces releasing and inhibiting hormones for the anterior pituitary

Thyroid Gland

• Thyroid hormones include thyroxine (T4), and triiodothyronine (T3).
• They accelerate metabolic rate
• Calcitonin (CT) lowers blood calcium levels by inhibiting bone breakdown

Thyroid and Parathyroid Glands

• Location of thyroid and parathyroid glands in the neck region

Parathyroid Glands

• Parathyroid glands: Small, glandular tissue that secrete parathyroid hormone (PTH).
• PTH increases blood calcium levels by boosting bone breakdown.

Regulation of Blood Calcium Levels

• A diagram illustrating how negative feedback loops regulate blood calcium levels involving the parathyroid glands and thyroid hormones

Adrenal Glands

• The adrenal cortex secretes corticosteroids:
• Mineralocorticoids (aldosterone) regulate electrolytes
• Glucocorticoids (cortisol) regulate metabolism
• Small amounts of sex hormones (androgens) are also released

Adrenal Glands (Continued)

• The adrenal cortex releases hormones in response to stress

Adrenal Glands (Continued)

• Cortisol plays roles in maintaining blood glucose balance, blood pressure regulation and has anti-inflammatory and immunosuppressive impacts; and regulates multiple responses to stress.

Adrenal Glands (Continued)

• Adrenal medulla secretes epinephrine and norepinephrine
• They increase the sympathetic response to stress

Pancreatic Islets of Langerhans

• Alpha cells secrete glucagon
• Glucagon raises blood glucose levels
• Beta cells release insulin
• Insulin lowers blood glucose levels

Pancreas

• Diagram showing the locations of the alpha and beta cells in the islets of Langerhans within the pancreas
• Location of pancreas, with connections to the small intestine, and diagram of a magnified portion of the pancreas showing the islets of Langerhans and the pancreatic duct.

Female Sex Glands

• Ovaries contain ovarian follicles and corpus luteum. These regions secrete estrogen as the feminizing hormone
• Estrogen contributes to physical development of the female

Male Sex Glands

• Interstitial cells of the testes secrete testosterone (the masculinizing hormone)
• Testosterone contributes to development of the male body and characteristics.

Thymus

• Thymosin plays a critical role in immune system development

Placenta

• The placenta produces hormones during pregnancy, including chorionic gonadotropins, estrogen, and progesterone.
• Progesterone is vital for maintaining the corpus luteum

Pineal Gland

• The pineal gland is located near the third ventricle in the brain
• It is involved with regulating the body's internal clock and has influence on the pituitary gland's functions through melatonin

Endocrine Functions Throughout the Body

• Various organs produce hormones that affect appetite, metabolism, and other critical functions, for instance, ghrelin, atrial natriuretic hormone (ANH), and leptin.

Endocrine Hormone Conditions

• Conditions related to hormone imbalances like gigantism (hypersecretion of growth hormone), diabetes insipidus (hyposecretion of ADH), goiter (thyroid enlargement), cretinism (thyroid deficiency in children), type 1 & 2 diabetes mellitus (problems with insulin function), and glycosuria (excess glucose in the urine).