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Biology - Chemical Coordination

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    Study Guide Biology – Chemical Coordination 1. Hormones and Glands The animal body uses two main systems to coordinate activities and keep everything working together smoothly: 1. Nervous coordination – fast, direct control using nerve impulses 2. Chemical coordination – slower, long - lasting control using hormones This section focuses on chemical coordination , which is carried out by a group of glands called the endocrine system . 1.1 The Endocrine System: Chemical Coordination The endocrine system is made up of special glands located throughout the body. Some important endocrine glands include the pancreas , thyroid gland , and adrenal glands . These glands release chemical messengers called hormones . • Hormones are made of proteins or sterol lipids • They travel through the bloodstream • They affect specific organs or tissues called target organs Rather than causing quick, short actions, hormones usually bring about slow but widespread and long - lasting changes in the body. 1.2 What Do Hormones Do? Hormones help coordinate body systems and regulate important processes such as growth, metabolism, and energy use. Here are two key examples: • Insulin ○ Secreted by the pancreas ○ Helps glucose move into body cells

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    Study Guide ○ Allows cells to use glucose for energy metabolism • Thyroxine ○ Secreted by the thyroid gland ○ Regulates the body’s overall metabolic rate ○ Influences how fast cells carry out chemical reactions These hormones don’t act instantly, but their effects are essential for normal body function. 1.3 Hormones vs. Nerve Signals Both the endocrine system and the nervous system coordinate body activities, but they work in different ways. 1.3.1 Endocrine Coordination • Uses hormones • Hormones travel through the blood • Effects are slower but long - lasting • Influences the body in a general and widespread way 1.3.2 Nervous Coordination • Uses nerve impulses • Signals move along specific nerve pathways • Effects are fast and localized • Controls actions like muscle contraction and gland activity Together, these two systems allow the body to respond both quickly and steadily to changes. 1.4 Endocrine vs. Exocrine Glands Endocrine glands have a unique feature: they have no ducts .

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    Study Guide • Hormones are released directly into the bloodstream • Because of this, endocrine glands are also called ductless glands In contrast, exocrine glands : • Release substances through ducts • Examples include salivary glands , which secrete digestive enzymes into the mouth This difference explains how hormones can reach many parts of the body at once. 1.5 A Shared System Across Animals The basic structure and function of endocrine glands and hormones are very similar in most animals. While this chapter focuses on humans, the same principles of hormonal control apply broadly across the animal kingdom. 2. Human Endocrine System The human endocrine system helps control and coordinate many body activities by releasing hormones . Hormones act as chemical messengers that travel through the bloodstream and tell organs and tissues what to do and when to do it . In this way, the endocrine system carefully regulates growth, metabolism, stress responses, reproduction, and many other vital processes . 2.1 Pituitary Gland: The Master Gland The pituitary gland is located at the base of the brain. It is often called the master gland because many of its hormones control other endocrine glands. The pituitary has two parts: 2.1.1 Anterior Pituitary (Adenohypophysis) This lobe produces several important hormones: • Human Growth Hormone (HGH) ○ Also called somatotropin ○ Stimulates body growth by increasing protein synthesis

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    Study Guide ○ Too little HGH causes dwarfism ○ Too much HGH causes gigantism • Prolactin (Lactogenic Hormone) ○ Promotes breast development and milk production in females • Thyroid - Stimulating Hormone (TSH) ○ Controls hormone release from the thyroid gland • Adrenocorticotropic Hormone (ACTH) ○ Stimulates hormone secretion from the adrenal glands • Follicle - Stimulating Hormone (FSH) ○ In females: stimulates development of egg - containing follicles ○ In males: stimulates sperm production • Luteinizing Hormone (LH) ○ In females: completes follicle maturation and forms the corpus luteum ○ In males: called interstitial cell - stimulating hormone (ICSH) and promotes male hormone production • Melanocyte - Stimulating Hormone (MSH) ○ Stimulates production of the pigment melanin 2.1.2 Posterior Pituitary (Neurohypophysis) The posterior pituitary stores and releases hormones made in the hypothalamus: • Antidiuretic Hormone (ADH or Vasopressin) ○ Increases water reabsorption in the kidneys • Oxytocin ○ Stimulates uterine contractions during childbirth

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    Study Guide 2.2 Thyroid Gland The thyroid gland is located at the base of the neck, just below the pharynx. It has two lobes connected by a narrow bridge called the isthmus . • Produces thyroxine , which controls the body’s metabolic rate • Produces calcitonin , which helps regulate calcium levels in the blood Thyroid Disorders • Iodine deficiency causes thyroid enlargement called goiter • Low thyroxine in childhood causes cretinism • Low thyroxine in adults causes myxedema • Excess thyroxine causes Graves’ disease , marked by a high metabolic rate 2.3 Parathyroid Glands The parathyroid glands are tiny glands located on the back of the thyroid gland. • They produce parathyroid hormone (parathormone) • This hormone: ○ Increases calcium reabsorption in the kidneys ○ Increases calcium absorption from the digestive tract • Together, these actions regulate calcium balance in the body 2.4 Adrenal Glands The adrenal glands sit on top of the kidneys and have two regions: 2.4.1 Adrenal Cortex (Outer Layer) Produces corticosteroids , including: • Mineralocorticoids (such as aldosterone)

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