Endocrine System

Nervous System controls the Endocrine System The endocrine system, along with the nervous system, functions in the regulation of body activities. (Maintaining Homeostasis) The nervous system acts through electrical impulses and neurotransmitters to cause muscle contraction and glandular secretion.

Nervous VS Endocrine The nervous system coordinates rapid and precise responses to stimuli using action potentials. The endocrine system maintains long-term control using chemical signals. The endocrine system works in parallel with the nervous system to control growth and maturation along with homeostasis

Endocrine system The endocrine system acts through chemical messengers called hormones that influence growth, development, and metabolic activities. The action of the endocrine system is measured in minutes, hours, or weeks and is more generalized than the action of the nervous system.

Two major categories of glands in the body Exocrine Exocrine glands have ducts that carry their secretory product to a surface Endocrine The endocrine glands do not have ducts to carry their product to a surface

Endocrine Glands The endocrine glands do not have ducts to carry their product to a surface. (ductless glands) Only endocrine glands produce Hormones The secretory products of endocrine glands (hormone) are secreted directly into the blood The Hormone is transported throughout the body, by blood, where they influence only those cells that have receptor sites for that hormone.

Endocrine glands of the Human body

Exocrine Glands Exocrine glands have ducts that carry their secretory product to a surface. These glands include the sweat glands mammary glands glands that secrete digestive enzymes These type of glands DO NOT produce hormones

Hormones 2 Types of hormones Steroid Hormones – are lipid like carbon rings These hormones are able to pass though the cell membrane. This type of hormones is produced in the adrenal glands and the Gonads (testis and ovaries) Protein hormones – made up of amino acids - These hormones cannot pass though the cell membrane because they cannot dissolve in fats. Ex. Insulin

Pituitary Gland The pituitary gland is often called the master gland because hormones released from the pituitary gland control other endocrine glands in the body. It is located at the base of the brain. A stalk links the pituitary to the hypothalamus, which controls release of pituitary hormones. The pituitary gland has two lobes: the anterior lobe (front) posterior lobe (back)

Major Hormones of the Anterior Pituitary Thyroid simulating hormone: (TSH) stimulates the production and release of thyroxin from the thyroid gland Adrenocorticotropic Hormone: (ACTH) stimulates the production and release of hormones of the adrenal glands Growth Hormone: (GH) controls the release of GH into he body

Major Hormones of the Anterior Pituitary Continued Follicle Simulating Hormone: (FSH) stimulates the development of egg cell in females and controls sperm production in males Luteinizing Hormone: (LH) Causes the release of an egg in the female and controls the production of sex hormones in both males and females Prolactin: Stimulates the secretion of milk after birth only found in females

Major Hormones of the Posterior Pituitary The posterior pituitary stores and releases hormones into the blood. 2 Major Hormones: Vasopressin (Antidiuretic Hormone - ADH) controls water balance in the body and blood pressure. Oxytocin is a small peptide hormone that stimulates uterine contractions during childbirth.

Job of the Hypothalamus The Hypothalamus contains neurons that control releases from the anterior pituitary. The Hypothalamus is the major link between the nervous system and the endocrine system The hypothalamus regulates homeostasis. It has regulatory areas for thirst, hunger, body temperature, water balance, and blood pressure, and links the nervous system to the endocrine system

The Adrenal Glands The nerves of the sympathetic nervous system regulate the release of adrenal hormones The adrenal glands secrete two hormones: epinephrine (adrenalin – 80%) and norepinephrine. (noradrenalin – 20%) “Fight or Flight hormones

The Thyroid Gland The thyroid gland is located in the neck. Thyroid stimulating hormone (TSH) from the anterior pituitary causes thyroid hormones be be released. Almost all body cells are targets of thyroid hormones. Thyroid hormone increases the overall metabolic rate regulates growth and development as well as the onset of sexual maturity

Parathyroid Gland These are tiny oval glands imbedded in the thyroid gland Secrete parathyroid hormone which regulates calcium and phosphate levels in the body. Calcium is necessary for proper growth and health of bones, teeth, blood clotting, and muscle contraction Phosphate is found in bones, and many compounds including DNA, ATP, and RNA

The Pancreas The pancreas is made up of exocrine and endocrine Excocrine glands that secrete digestive enzymes into the small intestine Endocrine glands secrete the hormones insulin and glucagon, which regulate blood glucose levels. Digestion prompts the release of insulin, which causes cells to take up glucose, and liver and skeletal muscle cells to form the carbohydrate glycogen.

Thymus Gland The Thymus is an endocrine gland and is located in the upper chest near the heart As a young child the thymus helps in the processing of lymphocytes The thymus secretes thymosin throughout childhood The thymus appears to have little or no function in adults

The Pineal Gland The pineal gland is a pea shaped endocrine gland that is attached to the base of the brain It secretes melatonin which is thought to help control the human sleep cycles. Low levels of melatonin during the day and higher levels at night

Gonads Sex glands Ovaries in female – produce eggs and female sex hormones estrogen and progesterone Testes in male – produce sperm and male sex hormone testosterone Both of these stimulate the development secondary sex characteristics when they are stimulated (puberty) In females this causes the broadening of the hips and development of breasts In males this cause the deepening of the voice, facial hair, body hair, and broader shoulders

Improper Functioning of Glands Hypersecretion – When a gland secretes more hormone then normal Hyposecretion – When a gland secretes less hormone then normal

Negative feedback Loop Hypothalamus receptors monitor blood levels of thyroid hormones. Low levels of thyroxin cause the Hypothalamus stimulates the anterior pituitary Hypothalamus stimulates the release of TSH-releasing hormone from the anterior pituitary. TSH travels to the thyroid where it promotes production of thyroid hormones, which in turn regulate metabolic rates and body temperatures. The increased levels of thyroid hormone in the blood stops the release of TSH form the hypothalamus and anterior pituitary gland stopping the thyroid from releasing too much thyroid hormone.