Podcast
Questions and Answers
How does the endocrine system primarily influence cellular activities?
How does the endocrine system primarily influence cellular activities?
- Via mechanical forces exerted on target tissues.
- Through electrical impulses that directly stimulate cells.
- By releasing hormones that alter metabolic activity. (correct)
- Through direct physical connections between organs.
Which of the following is a characteristic of hormones?
Which of the following is a characteristic of hormones?
- They act as signaling molecules that regulate cell activity. (correct)
- They always inhibit the growth of target tissues.
- Their effects are immediate, lasting only seconds.
- They exert effects only on the organs that produce them.
What is the primary role of the hypothalamus in the endocrine system?
What is the primary role of the hypothalamus in the endocrine system?
- To regulate body temperature through sweat glands.
- To directly control muscle contractions.
- To produce digestive enzymes.
- To serve as the major endocrine system controller. (correct)
Which of the following is a characteristic of local-acting hormones?
Which of the following is a characteristic of local-acting hormones?
Which of the following is an example of an autocrine function?
Which of the following is an example of an autocrine function?
Which gland type secretes substances through excretory ducts directly into adjoining areas?
Which gland type secretes substances through excretory ducts directly into adjoining areas?
Hormones can be classified based on their chemical structure. Which of the following is a major class of hormones?
Hormones can be classified based on their chemical structure. Which of the following is a major class of hormones?
Which type of hormone can readily pass through cell membranes due to its lipid-soluble nature?
Which type of hormone can readily pass through cell membranes due to its lipid-soluble nature?
What is the direct effect of hormones on target cells?
What is the direct effect of hormones on target cells?
How do steroid and peptide hormones differ in their mechanisms of action on target cells?
How do steroid and peptide hormones differ in their mechanisms of action on target cells?
How can a single cell respond to multiple hormone signals simultaneously?
How can a single cell respond to multiple hormone signals simultaneously?
Where are thyroid hormone receptors typically located?
Where are thyroid hormone receptors typically located?
What is the significance of the blood-brain barrier in the context of hormone action?
What is the significance of the blood-brain barrier in the context of hormone action?
What is a key factor that controls target cell activation by a hormone?
What is a key factor that controls target cell activation by a hormone?
How does down-regulation affect target cell sensitivity to hormones?
How does down-regulation affect target cell sensitivity to hormones?
Flashcards
Endocrine System
Endocrine System
Integrated system of small organs exerting large effects on cell metabolic activity, controlling it by hormonal means.
Hormones
Hormones
Bloodborne chemical substances functioning as signaling (messenger) molecules that regulate cell activity.
Hypothalamus
Hypothalamus
A neuroendocrine organ that produces/releases several hormones and is the major endocrine controller.
Local-acting hormones
Local-acting hormones
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Autocrines
Autocrines
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Paracrines
Paracrines
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Exocrine Gland
Exocrine Gland
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Endocrine Gland
Endocrine Gland
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Mixed Gland
Mixed Gland
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Hormone characteristics
Hormone characteristics
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Amino acid-based hormones
Amino acid-based hormones
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Steroid hormones
Steroid hormones
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Cellular Action
Cellular Action
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Peptide/steroid hormone
Peptide/steroid hormone
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Up-regulation
Up-regulation
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Study Notes
- Topics include the Endocrine system overview, Hormone types, chemistry and control, Target cell action and properties, Signaling mechanisms and Target cell activation
Endocrine System Overview
- An integrated system of small organs exerts significant effects on cell metabolic activity and controls cell activity through hormones
- Hormones are bloodborne chemical substances that act as signaling messengers, regulating cell activity with effects felt far from the release site, stimulating or inhibiting tissue growth and function for seconds to days
- The hypothalamus is the primary neuroendocrine controller releasing various hormones and influencing the autonomic nervous system
Local-Acting Hormones
- Produced by various tissues, not considered true hormones due to their effect close to the production site
- These include adipose cells, the small intestine, the stomach, kidneys, and heart
- Autocrines exert effects on the same cells that secrete them, using autocrine receptors, illustrated by prostaglandin release causing vasoconstriction
- Paracrines affect nearby cells using paracrine receptors like pancreatic somatostatin which inhibits insulin and glucagon release from beta and alpha cells respectively
Hormone Control and Glands
- Body cells targeted by hormones regulate growth, maintenance and repair through processes like reproduction, development, electrolyte and water balance, cell metabolism, nutrient management, energy output, and immune responses
- Exocrine glands secrete sweat, saliva, and digestive enzymes, moved through ducts to adjoining areas
- Endocrine glands, including the pituitary, thyroid, parathyroid, adrenal, and pineal glands, release hormones into interstitial fluid and bloodstream, binding to target organ receptors
- Mixed glands, such as the pancreas, gonads, and placenta, perform both exocrine and endocrine functions, like the pancreas producing insulin and digestive enzymes
Hormones- General Characteristics
- Hormones regulate metabolic activity, show a delayed response lasting seconds to hours, with prolonged effects
- Amino acid-based hormones are proteins, including amines, short peptides, and long polypeptides
- Steroids are cholesterol-based
- Eicosanoids consist of biologically active lipids such as leukotrienes and prostaglandins, released by nearly all cell membranes
Hormone Chemistry
- Amino acid-based hormones are water-soluble and can not pass through cell membranes, except for thyroid hormone which has to relay an external signal through an internal pathway
- Steroid hormones, being lipid-soluble pass through cell membranes
- A hydrophobic cholesterol base helps steroid hormones penetrate the hydrophobic phospholipid layers
- Variations in receptors and target cell types determine the exact cellular response to hormones which then alter cell activities
Hormone Action on Target Cells
- Hormones signal changes in cellular action, shifting protein output, activating enzymes, adjusting ion channels, and controlling secretion
- Target cell effects include altering plasma membrane permeability, stimulating protein production, activating or deactivating enzyme systems, inducing secretion, and promoting mitosis, which supports cell maintenance, growth, and repair
Hormones Signaling
- Whether peptide or steroid, a target cell’s activation depends on membrane permeability and receptor location
- Steroid hormones enter the cell, bind to chaperone proteins, migrate to the nucleus, and bind to an internal (DNA) receptor, changing cell activity by stimulating transcription (direct mechanism)
- Peptide hormones bind to an extracellular receptor, triggering signal transduction, producing cAMP, and activating enzymes through an indirect mechanism
Peptide Hormones- Target Cell Properties
- Hormones circulate to all body tissues except the brain, protected by the blood-brain barrier
- Hormones affect cells with specific receptors, activating a pre-programmed function
- A single cell can have different types of hormone receptors
- Receptor location, amount, and type of vary among cells with ACTH receptors found only on adrenal cortex cells and thyroid hormone receptors on nearly all body cells
Peptide Hormones- Target Cell Activation
- Hormone action is controlled by hormone blood levels, how many target cell receptors there are, and the binding strength
- Receptor number is a dynamic, regulated process
- Up-regulation happens when a cell increases receptor numbers in response to low hormone levels
- Down-regulation occurs when high hormone levels cause a reduction in receptor numbers, desensitizing the cell to the hormone
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