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Questions and Answers
The endocrine system comprises feedback loops of ______ released by internal glands.
The endocrine system comprises feedback loops of ______ released by internal glands.
hormones
In vertebrates, the ______ is the neural control center for all endocrine systems.
In vertebrates, the ______ is the neural control center for all endocrine systems.
hypothalamus
Cells that have specific receptors for a hormone are called ______ cells.
Cells that have specific receptors for a hormone are called ______ cells.
target
Examples of ______ hormones include insulin and gastrin.
Examples of ______ hormones include insulin and gastrin.
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Endocrine signaling typically results in a ______ response that can last for an extended period.
Endocrine signaling typically results in a ______ response that can last for an extended period.
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The nervous system uses ______ and chemical signals.
The nervous system uses ______ and chemical signals.
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The major endocrine glands in humans include the thyroid, parathyroid, pituitary, pineal, adrenal glands, and the ______ and ______.
The major endocrine glands in humans include the thyroid, parathyroid, pituitary, pineal, adrenal glands, and the ______ and ______.
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The hormone ______ regulates the circadian rhythm.
The hormone ______ regulates the circadian rhythm.
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Hyposecretion of growth hormone during childhood can lead to ______ dwarfism.
Hyposecretion of growth hormone during childhood can lead to ______ dwarfism.
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The ______ is the neural control center for all endocrine systems in vertebrates.
The ______ is the neural control center for all endocrine systems in vertebrates.
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Study Notes
Endocrine System Overview
- The endocrine system is a messenger system in an organism.
- It comprises feedback loops of hormones.
- Hormones are released by internal glands.
- Hormones are released directly into the circulatory system.
- Hormones target and regulate distant organs.
- In vertebrates, the hypothalamus is the neural control center for all endocrine systems.
- The endocrine system and the nervous system are primarily responsible for maintaining homeostasis in the human body.
Endocrine Glands
- The major endocrine glands in humans include the thyroid, parathyroid, pituitary, pineal, adrenal glands, and gonads (testes and ovaries).
- The hypothalamus, pancreas, and thymus also function as endocrine glands.
- The hypothalamus and pituitary glands are organs of the neuroendocrine system.
- The hypothalamus links the endocrine system to the nervous system via the pituitary gland.
Pituitary Gland
- The pituitary gland is approximately the size of a pea.
- Hormones secreted by the pituitary gland include:
- Growth hormone
- Prolactin
- Antidiuretic hormone (ADH)
- Oxytocin
- Growth hormone is involved in skeletal muscle and bone growth.
- Hyposecretion leads to pituitary dwarfism.
- Hypersecretion leads to gigantism.
Pineal Gland
- The pineal gland is a cone-shaped structure within the brain.
- It produces melatonin, which regulates the circadian rhythm.
- Circadian rhythm is the natural, internal process that regulates the sleep-wake cycle and repeats every 24 hours.
- Melatonin levels increase during sleep and decrease before awakening.
Thyroid and Parathyroid Glands
- The thyroid gland is a butterfly-shaped gland anterior to the trachea and inferior to the larynx.
- It has follicles that produce thyroid hormone (T3 and T4).
- Thyroid hormone increases metabolism by controlling the rate of glucose oxidation to produce body heat and chemical energy (ATP).
- Parafollicular cells release calcitonin, which decreases blood calcium levels.
- Parathyroid glands located on the posterior surface of the thyroid gland produce parathyroid hormone.
- Hypothyroidism means low thyroid hormone levels, leading to low metabolic rate, weight gain, lethargy, and a feeling of being cold.
- Hyperthyroidism means high thyroid hormone levels, leading to increased metabolic rate, weight loss, hyperactivity, and heat intolerance.
Adrenal Glands
- Adrenal glands are located superior to the kidneys.
- They secrete epinephrine and norepinephrine, which produce effects similar to sympathetic responses during stress.
- The adrenal glands secrete cortisol, a primary stress hormone.
Stress Response
- Stress is any potential or actual threat to homeostasis.
- Physiological and psychological stresses exist.
- It triggers a stress response that aims to bring back homeostasis.
- The stress response activates two systems:
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- Sympathetic nervous system (fight-or-flight response).
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- Hypothalamo-pituitary-adrenal (HPA) axis (endocrine response).
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Hypothalamic-Pituitary-Adrenal (HPA) Axis
- The hypothalamus is the major link between the nervous and endocrine systems.
- The secretion of CRH (corticotropin-releasing hormone) activates ACTH (adrenocorticotropic hormone) release from the anterior pituitary.
- ACTH travels to the adrenal glands to stimulate cortisol production, which is the body's major stress hormone.
- Cortisol affects nearly every organ system; its effects include regulating blood glucose, blood pressure, and immune function.
- There is negative feedback control of cortisol. High levels of cortisol inhibit further cortisol production.
- Prolonged cortisol exposure can cause a variety of health problems.
Pancreas
- The pancreas has both exocrine and endocrine functions.
- The endocrine function involves the release of insulin from beta cells, decreasing glucose levels.
- The endocrine function involves the release of glucagon from alpha cells, increasing glucose levels.
Gonads
- Testes secrete testosterone and ovaries secrete estrogen and progesterone.
- These hormones regulate reproductive processes.
Local Hormones
- Autocrine hormones act on the same cells that produced them.
- Paracrine hormones act on neighboring cells.
Circulating Hormones
- Hormones are carried through the blood to act on distant target cells.
Neural vs. Endocrine Signaling
- Endocrine system uses chemical signals (hormones), and its response is fast or slow (up to 48 hours). Hormones have a widespread effect throughout the body.
- Nervous system uses electrical and chemical signals (neurotransmitters), and its responses are always fast (milliseconds). Nervous system signals are localized.
Objectives
- Identify functions of the endocrine system.
- Compare signaling in the endocrine system and nervous system.
- Describe hormone interactions with target cells.
- Discuss endocrine glands and their functions.
- Discuss the stress response as an example of neuroendocrine signaling.
Additional Terminology
- Endocrinology: The study of the endocrine system and its disorders.
- Target cells: Cells with specific receptors for a specific hormone.
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Description
Explore the essential components and functions of the endocrine system in this quiz. Learn about hormone feedback loops, major glands, and the role of the hypothalamus in regulating bodily functions. Test your knowledge of how the endocrine system contributes to homeostasis.
