Endocrine System

Hormones

• Hormones are chemicals that are secreted into the blood stream by the endocrine glands

• Hormones are received by target cells throughout the body

• Target cells have receptor proteins that help determine the response to the hormone

• Different hormone/receptor combinations cause different responses

Types of Hormones

Steroid Hormone

Target Cell Creates Response

Chemical Structure of Steroids

• Steroid hormones are created by modifying cholesterol molecules

Peptide and Amine Hormones• Peptide and Amine hormones are large molecules that are

not lipid soluble and cannot enter target cells directly.

Glands of the Endocrine System

• Hypothalamus– Connection between the

Nervous System and the Endocrine System

– Secretes Antidiuretic Hormone (ADH) to help maintain kidney functions

– Secretes hormones into the pituitary gland to stimulate the production of other hormones

Pituitary Gland

• Sometimes called the “Master Gland”

• Controls many other glands in the body

• Directly connected to the Hypothalamus through neural connections

Pituitary GlandHormone Effect

Somatotropin (Growth Hormone) Affects growth and development; stimulates protein production

Prolactin Stimulates milk let down during lactation

Thyroid-stimulating hormone (TSH) Stimulates the production and secretion of thyroid hormones

Luteinizing hormone (LH) In females this LH acts on the ovary to stimulate the production of estrogens and induce ovulation. In males this LH acts on the testis to stimulate the production of testosterone.

Pineal Gland

• Located in the center of the brain behind the Hypothalamus

• Produces Melatonin which helps regulate sleep and waking cycle

• Sometimes called the “Biological Clock”

Thyroid

• Located in front of the trachea

• Responsible for maintaining Metabolism

ThyroidHormone Effect

Triiodothyronine (T3) Body temperature, growth and heart rate

Thyroxine (T4) Controls the metabolic processes in the body

Calcitonin Stimulates calcium deposits to bones

Parathyroid

• Four small glands located on the back of the Thyroid

• Help to maintain the amount of calcium in the blood to maintain muscle and nervous function

Parathyroid

• Releases Parathyroid Hormone when calcium levels are low

• This causes bone break down and increased calcium absorption

Thymus

• Essential in the development of immune functions

• Very large in childhood• Tissue is replaced by fat

into adulthood• Produces humoral

which stimulates the development of the lymphoid system

Adrenal Glands

• Located on each of the Kidneys

• Divided into two sections – Cortex• Produces hormones

essential to life– Medulla• Produces hormones

not essential to life

Adrenal GlandsHormone Effect

Cortisol Immune suppression and stress response

Adrenaline (Epinephrine)

*** Also a neurotransmitter

Variety of reactions depending on the tissue. Heart – Increases heart rateLungs – Increases respiration rateLiver - Glycogenolysis

Noradrenaline (Norepinephrine)

*** Also a neurotrasmitter

Similar to Adrenaline

Pancreas

• Main control of the blood sugar in the body

• Secretes Insulin or Glucagon as required to maintain blood sugar levels

• Endocrine portion is called the Islets of Langerhans

Blood Sugar Homeostasis

Testes/Ovaries

• Development and maintenance of sex traits

• Become more active at puberty

• Produce steroid hormones

Testes/OvariesHormone Effect

Estrogen Maintaining female sex characteristics

Testosterone Maintaining male sex characteristics

Progesterone Stimulates the lining of the uterus and prepares the body for milk production

Inhibin Inhibits the production of Follicle Stimulating Hormone (FSH) in the Pituitary gland