45 Chapter Flashcards
In animals, hormones are secreted into the extracellular fluid, circulate in the blood (or hemolymph), and communicate regulatory messages throughout the body.
True
Target cells
Cells with the matching receptor to the hormone.
Endocrine system basic function
Chemical signaling by hormones
Nervous system
A network of neurons that transmit signals along dedicated pathways.
Endocrine signaling
Secreted molecules diffuse into the bloodstream and trigger responses in target cells anywhere in the body. Hormones secreted into extracellular fluid by endocrine cells reach target cells via the bloodstream (or hemolymph).
Local regulators
Molecules that act over short distances and reach their target cells solely by diffusion.
Local regulators include:
Cytokines and growth factors
Cytokines
Enable communication between immune cells
Growth factors
Promote growth, division, and development of many types of cells
Signaling by local regulators can either be ____________ or ____________
Paracrine, autocrine
Paracrine signaling
Target cells lie near the secreting cell. Secreted molecules diffuse locally and trigger a response in neighboring cells.
Autocrine signaling
The secreting cells themselves are the target cells. Secreted molecules diffuse locally and trigger a response in the cells that secrete them.
Prostaglandin
Are modified fatty acid local regulators that are secreted by virtually all tissues and that perform a wide variety of functions. For example, it functions in reproduction and in inflammation and blood clotting as part of the immune system
Synapses
Are specialized junctions between two nerve cells where they communicate with each other by transmitting electrical or chemical signals.
Neurotransmitter
A molecule that is released from the synaptic terminal of a neuron at a chemical synapse, diffuses across the synaptic cleft, and binds to the postsynaptic cell, triggering a response.
Synaptic signaling
Neurotransmitters diffuse across synapses and trigger responses in cells of target tissues (neurons, muscles, or glands).
Neurohormone
A molecule that is secreted by a neuron, travels in body fluids, and acts in specific target cells, changing their functioning.
Neuroendocrine signaling
Neurohormones diffuse into the bloodstream and trigger responses in target cells anywhere in the body.
Pheromones
Chemicals that are released into the external environment.
Nitric oxide (NO)
A gas produced by many types of cells that functions as a local regulator and as a neurotransmitter. When the level of oxygen in the blood falls, endothelial cells in blood vessel walls synthesize and release NO. After diffusing into the surrounding smooth muscle cells, NO activated an enzyme that relaxes the cells. The result is vasodilation, which increases blood flow to tissues.
Hormones fall into three major chemical classes:
Polypeptides, steroids, and amines
Polypeptide hormone characteristics
-Water-soluble (hydrophilic)
-Contains two chains in its active form
Ex. Insulin
Steroid hormone characteristics
-Lipid-soluble (hydrophobic)
-Are lipids that contain four fused carbon rings.
-Are all derived from the steroid cholesterol.
Ex. Cortisol
Amine hormones
-Can be hydrophilic or hydrophobic
-Are synthesized from a single amino acid, either tyrosine or tryptophan
Ex. Epinephrine and thyroxine
Water-soluble hormone cellular response pathways
Water-soluble hormones are secreted by exocytosis and travel freely in the bloodstream. These hormones bind to cell-surface receptors because of their lipid insolubility.
Lipid-soluble hormones cellular response pathways
Lipid-soluble hormones diffuse out across the membranes of endocrine cells. Outside the cell, they bind to transport proteins that keep them soluble in the aqueous environment of the blood. Upon leaving the blood, they diffuse into target cells and typically bind to receptors in the cytoplasm or nucleus.
Signal transduction
The series of changes in cellular proteins that converts the extracellular chemical signal to a specific intracellular response.
Epinephrine (adrenaline)
A water-soluble hormone that binds to the G protein-coupled receptor in the membrane of target cells in the liver and ultimately causes the liver to release glucose into the bloodstream. In smooth muscle cell lining blood vessels that supply skeletal muscle, epinephrine leads to vasodilation and hence increased blood flow to skeletal muscles. In the smooth muscle cells lining blood vessels of the intestines, epinephrine leads to vasoconstriction, restricting blood flow to the intestines.
In most cases, the response to a lipid-soluble hormone is a _____________
Change in gene expression
Endocrine glands
A ductless gland that secretes hormones directly into the interstitial fluid, from which they diffuse into the bloodstream.
Note that endocrine glands secrete hormones directly into the surrounding fluid. In contrast, exocrine glands, such as salivary glands, have ducts that carry secreted substances onto body surfaces or into body cavities.
True
Human endocrine glands:
Pineal gland
Hypothalamus
Pituitary gland
Thyroid gland
Parathyroid glands
Adrenal glands
Pancreas
Ovaries (female)
Testes (male)
Pineal gland hormone(s)
Melatonin: Participates in regulation of biological rhythms.
Hypothalamus hormone(s)
-Hormones released from posterior pituitary (oxytocin and vasopressin)
-Releasing and inhibiting hormones: Regulate anterior pituitary
Pituitary gland structures
Anterior pituitary
Posterior pituitary
Anterior pituitary hormone(s)
-Follicle-stimulating hormone (FSH) and luteinizing hormone (LH): stimulate ovaries and testes
-Thyroid-stimulating hormone (TSH): Stimulates thyroid gland
-Adrenocorticotropic hormone (ACTH): Stimulates adrenal cortex
-Prolactin: Stimulates mammary gland cells
-Growth hormone (GH): Stimulates growth and metabolic functions
Posterior pituitary hormone(s)
-Oxytocin: Stimulates contraction of smooth muscle cells in uterus and mammary glands
-Vasopressin: Promotes retention of water by kidneys; influences social behavior and bonding
Thyroid gland hormone(s)
-Thyroid hormone (T3 and T4): Stimulates and maintains metabolic processes
-Calcitonin: Lowers blood calcium level
Parathyroid glands hormone(s)
-Parathyroid hormone: Raises blood calcium level
Adrenal glands structures
Adrenal medulla
Adrenal cortex
Adrenal medulla hormone(s)
Epinephrine and norepinephrine: Raise blood glucose level; increase metabolic activities; constrict blood vessels
Adrenal cortex hormone(s)
-Glucocorticoids: Raise blood glucose level
-Mineralcorticoids: Promote reabsorption of Na+ and excretion of K+ in kidneys
Pancreas hormone(s)
-Insulin: Lowers blood glucose level
-Glucagon: Raises blood glucose level
Ovaries hormone(s)
-Estrogens: Stimulates uterine lining growth; promote development and maintenance of female secondary sex characteristics
-Progestins: Promote uterine lining growth
Testes hormone(s)
-Androgens: Support sperm formation; promote development and maintenance of male secondary sex characteristics
In a simple endocrine pathway,
Endocrine cells respond directly to an internal or environmental stimulus by secreting a particular hormone.
In a simple neuroendocrine pathway,
The stimulus is received by a sensory neuron, which stimulates a neurosecretory cell. The neurosecretory cell then secretes a neurohormone, which diffuses into the bloodstream and travels to target cells.
Oxytocin
A hormone (or neurohormone) produced by the hypothalamus and released from the posterior pituitary. It induces contractions of the uterine muscles during labor and causes the mammary glands to eject milk during nursing.
Negative feedback
The response reduces the initial stimulus
Positive feedback
Reinforces a stimulus, leading to an even greater response
Hypothalamus
The ventral part of the vertebrate forebrain; functions in maintaining homeostasis, especially in coordinating the endocrine and nervous systems; secretes hormones of the posterior pituitary and releasing factors that regulate the anterior pituitary.
Pituitary gland
An endocrine gland located at the base of the hypothalamus; consists of a posterior lobe, which stores and releases two hormones produced by the hypothalamus, and an anterior lobe, which produces and secretes many hormones that regulate diverse body functions.
The posterior pituitary is an extension of the hypothalamus.
True
Anterior pituitary
An endocrine gland that synthesizes and secretes hormones in response to hormones from the hypothalamus.
Each hypothalamic hormone is either a _________________ or an ____________.
Releasing hormone, inhibiting hormone
Prolactin
A hormone produced and secreted by the anterior pituitary with a great diversity of effect in different vertebrate species. In mammals, it stimulates growth of and milk production by the mammary glands.
Every anterior pituitary hormone is controlled by at least one releasing hormone.
True
Tropic hormones, or tropins
A hormone that has an endocrine gland or endocrine cells as a target. For example, hormone cascade pathways.
FSH and LH are considered _____________ because they…
Gonadotropins
Convey signals from the hypothalamus to the gonads (testes or ovaries)
Thyroid hormone
Either of two iodine-containing hormones (triiodothyronine and thyroxine) that are secreted by the thyroid gland and that help regulate metabolism, development, and maturation in vertebrates.
Thyroid gland
An endocrine gland, located on the ventral surface of the trachea, that secretes two iodine-containing hormones, triiodothyronine (T3) and thyroxine (T4), as well as calcitonin.
Hypothyroidism
The secretion of too little thyroid hormone; can cause weight gain, lethargy, and intolerance to cold in adults.
Hyperthyroidism
Excessive secretion of thyroid hormone; can lead to high body temperature, profuse sweating, weight loss, irritability, and high blood pressure.
Growth hormone (GH)
A hormone that is produced and secreted by the anterior pituitary and that has both direct (nontropic) and tropic effects on a wide variety of tissues. In the liver, GH causes the release of insulin-like growth factors (IGFs), which circulate in the blood and directly stimulate bone and cartilage growth.
Parathyroid glands
A set of four small structures embedded in the posterior surface of the thyroid hormone, play a major role in blood Ca2+ regulation.
Parathyroid hormone (PTH)
A hormone secreted by the parathyroid glands that raises blood calcium level by promoting calcium release from bone and calcium retention by the kidneys.
Calcitonin
A hormone that inhibits bone breakdown and enhances Ca2+ excretion by the kidneys.
Adrenal glands
Two endocrine glands located adjacent to the kidneys in mammals. Is made up of two parts, the adrenal cortex, the outer part, and the adrenal medulla, the central part.
The adrenal cortex consists of true cells, whereas the secretory cells of the adrenal medulla develop from neural tissue. This, like the pituitary gland, each adrenal gland is a fused endocrine and neuroendocrine gland.
True
Catecholamines
A class of amine hormones synthesized from the amino acid tyrosine. Includes both epinephrine and norepinephrine
The adrenal medulla secretes epinephrine and norepinephrine in response to short-term stress.
The adrenal cortex functions in the body’s response to long-term stress.
True
In contrast to the adrenal medulla, which reacts to nervous input, the adrenal cortex responds to endocrine signals.
True
Glucocorticoids
A steroid hormone that is secreted by the adrenal cortex and that influences glucose metabolism and immune function. Promote glucose synthesis from noncarbohydrate sources, such as proteins, making more glucose available as fuel. Glucocorticoids also act on skeletal muscle, causing the breakdown of muscle proteins. The resulting amino acids are transported to the liver and kidneys, where they are converted to glucose and released into the blood.
Mineralocorticoids
A steroid hormone secreted by the adrenal cortex that regulates salt and water homeostasis.
The gonads produce and secrete three major types of steroid sex hormones:
androgens, estrogens, and progestins.
Androgens
Any steroid hormone, such as testosterone, that stimulates the development and maintenance of the male reproductive system and secondary sex characteristics.
Testosterone
A steroid hormone required for development of the male reproductive system, spermatogenesis, and male secondary sex characteristics; the major androgen in mammals.
Anabolic
Muscle-building
Use of anabolic steroids, while effective in increasing muscle mass, can cause severe acne outbreaks and liver damage, as well as significant decreases in sperm count and testicular size.
True
Estrogens
Any steroid hormone, such as estradiol, that stimulates the development and maintenance of the female reproductive system and secondary sex characteristics.
Estradiol
A steroid hormone that stimulates the development and maintenance of the female reproductive system and secondary sex characteristics; the major estrogen in mammals.
Progestins
Any steroid hormone with progesterone-like activity.
Progesterone
A steroid hormone that prepares the uterus for pregnancy; the major progestin in mammals.
Endocrine disruptor
A foreign molecule that interrupts the normal function of a hormone pathway.
Melatonin
A hormone that is secreted by the pineal gland and that is involved in the regulation of biological rhythms and sleep.
Pineal gland
A small gland in the dorsal surface of the vertebrate forebrain that secretes the hormone melatonin.
Suprachiasmatic nucleus (SCN)
A group of neurons in the hypothalamus that control the pineal gland. The SCN functions as a biological clock and receives input from specialized light-sensitive neurons in the retina of the eye.
Melanocyte-stimulating hormone (MSH)
A hormone produced and secreted by the anterior pituitary with multiple activities, including regulating the behavior of pigment-containing cells in the skin of some vertebrates.
