Chapter 26 Hormones and the Endocrine System - Coggle Diagram
Chapter 26 Hormones and the Endocrine System
The Nature of Chemical Regulation
Chapter 26.1 Chemical and electrical signals coordinate body functions
Chemical signals of the endocrine system (hormones) regulate gradual changes in the body. In contrast, electrical signals of the nervous system coordinate immediate responses.
is a group of interacting glands and tissues that produce and secrete chemicals to initiate and maintain body functions.
Endocrine cells release chemical signals called
, which travel in the bloodstream to all parts of the body.
Hormones are made and secreted mainly by organs called
Specialized neurons called
perform functions in both systems. Like all neurons, neurosecretory cells conduct electrical signals, but they also make and secrete hormones into the blood.
Chapter 26.2 Hormones affect target cells using two main signaling mechanisms
➊ A water- soluble hormone molecule binds to the receptor protein, activating it.
➋ This initiates a signal transduction pathway, a series of changes in cellular proteins (relay molecules) that converts an extracellular chemical signal to a form that can bring about a response inside the cell.
➌ The final relay molecule activates a protein that carries out the cell’s response, which may occur in the cytoplasm (such as activating an enzyme) or in the nucleus (regulating gene expression).
➊ A lipid- soluble hormone enters a cell by diffusion. If the cell is a target cell.
➋The hormone binds to an open receptor protein in the cytoplasm or nucleus. Rather than triggering a signal transduction pathway with relay proteins, as happens with a water-soluble hormone, the hormone-receptor complex itself usually carries out the transduction of the hormonal signal: The complex acts as a transcription factor—a gene activator or repressor.
➌ The hormone-receptor complex attaches to specific sites on the cell’s DNA in the nucleus.
➍ The binding to DNA stimulates gene regulation, turning genes either on (by promoting transcription of certain genes into RNA) or off.
Chapter 26.3 A widely used weed killer demasculinizes male frogs.
The weed killer atrazine is called an endocrine disrupter because it interferes with endocrine function.
, substances that interfere with the endocrine system’s normal functions.
Such chemicals can potentially enter animal cells, altering the normal ratio of sex hormones (hormones that regulate growth, development, reproductive cycles, and sexual behaviors).
The Vertebrate Endocrine System
Chapter 26.4 The vertebrate endocrine system consists of more than a dozen major glands
: Participates in regulation of biological rhythms
: Stimulates and maintains metabolic processes
: Lowers blood calcium level
Parathyroid hormone (PTH)
: Raises blood calcium level
Testes (in males)
: Support sperm formation; promote development and maintenance of male secondary sex characteristics
Ovaries (in females)
: Stimulate uterine lining growth; promote development and maintenance of female secondary sex characteristics
: Promotes uterine lining growth
Multiple hormones from the hypothalamus directly control the pituitary gland.
Numerous hormones affect the activity of other endocrine glands and cells of the body
: Stimulates contraction of uterus and mammary gland cells
Antidiuretic hormone (ADH)
: Promotes retention of water by kidneys
Adrenal glands (atop kidneys)
: Raise blood glucose level; increase metabolic activities; constrict certain blood vessels
: Raise blood glucose level
: Increase blood volume and blood pressure
: Lowers blood glucose level
: Raises blood glucose level
Chapter 26.5 The hypothalamus, which is closely tied to the pituitary, connects the nervous and endocrine systems
• Master control center of the endocrine system
• Composed of endocrine tissue
• Controlled by hypothalamus
• Produces and secretes its own hormones
• Composed of nervous tissue
• Stores and secretes hormones made by hypothalamus
Hormones and Homeostasis
Chapter 26.6 The thyroid regulates development and metabolism
Thyroid hormones regulate an animal’s development and metabolism. Negative feedback maintains homeostatic levels in the blood.
performs several important homeostatic functions and stimulates metabolism in virtually all the tissues of the body.
, an enlargement of the thyroid.
is located in your neck, wrapping around the trachea, just under your larynx (voice box).
Chapter 26.7 The gonads secrete sex hormones
Estrogens, progesterone, and androgens are steroid sex hormones produced by the gonads in response to signals from the hypothalamus and pituitary.
, or sex glands (ovaries in the female and testes in the male), secrete sex hormones in addition to producing gametes (eggs and sperm).
maintain the female reproductive system and promote the development of female features including breasts and wider hips.
is primarily involved in preparing and maintaining the uterus to support an embryo.
stimulate the development and maintenance of the male reproductive system; the main androgen is
Chapter 26.8 Pancreatic hormones regulate blood glucose level
is a gland with dual functions: It secretes digestive enzymes into the small intestine, and it secretes two protein hormones,
, into the blood.
Within each islet are beta cells, which produce insulin, and alpha cells, which produce glucagon. Insulin and glucagon are said to be
because the effects of one oppose the effects of the other.
Chapter 26.9 Diabetes is a common endocrine disorder
Diabetes mellitus results from a lack of insulin or a failure of cells to respond to it.
is a serious hormonal disorder caused by the body’s inability to produce or use insulin, thereby decreasing the absorption of glucose from the blood.
The result of diabetes is an elevated level of blood glucose, or
Chapter 26.10 The adrenal glands mobilize responses to stress
Nerve signals from the hypothalamus stimulate the adrenal medulla to secrete epinephrine and norepinephrine, which quickly trigger the “fight-or-flight” response.
ACTH from the pituitary causes the adrenal cortex to secrete glucocorticoids and mineralocorticoids, which boost blood pressure and energy.
The endocrine system includes two adrenal glands, one sitting on top of each kidney.
Each adrenal gland is actually made up of two glands fused together: a central portion called the
and an outer portion called the
Chapter 26.11 A single hormone can perform a variety of functions in different animals.
Diverse functions have evolved for hormones.
The hormone prolactin (PRL), which is produced and secreted by the anterior pituitary under the direction of the hypothalamus, is a good example of a hormone that produces diverse effects in different vertebrate species.
Prolactin is an ancient hormone whose functions diversified through evolution.
Chapter 26.12 Hormones can promote social behaviors
plays a part in mammalian social behaviors. For example, oxytocin promotes maternal bonds.
Oxytocin is also associated with social attachments between human mothers and their babies.
Levels of the hormone rise when new mothers gaze into the eyes of their babies. The oxytocin levels then rise in the baby, causing the baby to gaze back. This mutual gazing causes the production of more and more oxytocin and is thought to promote a strong emotional bond.