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When a target cell is exposed to high levels of a hormone for a long period, what is likely to occur?
When a target cell is exposed to high levels of a hormone for a long period, what is likely to occur?
What is the primary function of the hypophyseal portal system?
What is the primary function of the hypophyseal portal system?
Which of the following hormones is not produced by the anterior pituitary gland?
Which of the following hormones is not produced by the anterior pituitary gland?
Which of the following hormones utilizes the PIP2-calcium second messenger system?
Which of the following hormones utilizes the PIP2-calcium second messenger system?
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What is the relationship between growth hormone (GH) and insulin-like growth factors (IGFs)?
What is the relationship between growth hormone (GH) and insulin-like growth factors (IGFs)?
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Which of the following hormones is directly inhibited by rising blood levels of thyroid hormones?
Which of the following hormones is directly inhibited by rising blood levels of thyroid hormones?
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Which of the following correctly describes the relationship between glucagon and epinephrine in their actions on the liver?
Which of the following correctly describes the relationship between glucagon and epinephrine in their actions on the liver?
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What is the primary function of antidiuretic hormone (ADH)?
What is the primary function of antidiuretic hormone (ADH)?
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What is the significance of the fact that steroid hormones and thyroid hormone circulate bound to plasma proteins?
What is the significance of the fact that steroid hormones and thyroid hormone circulate bound to plasma proteins?
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What is the main difference between tropic hormones and non-tropic hormones?
What is the main difference between tropic hormones and non-tropic hormones?
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Which of the following best describes the action of prolactin (PRL)?
Which of the following best describes the action of prolactin (PRL)?
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Which of the following hormones is not involved in the regulation of reproduction?
Which of the following hormones is not involved in the regulation of reproduction?
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What is the primary function of the paraventricular neurons in the hypothalamus?
What is the primary function of the paraventricular neurons in the hypothalamus?
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What is the significance of the hypothalamic-hypophyseal tract?
What is the significance of the hypothalamic-hypophyseal tract?
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Which of the following correctly describes the half-life of a hormone?
Which of the following correctly describes the half-life of a hormone?
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How does alcohol affect the action of antidiuretic hormone (ADH)?
How does alcohol affect the action of antidiuretic hormone (ADH)?
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What is the primary function of the hormones in the endocrine system?
What is the primary function of the hormones in the endocrine system?
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Which of the following is NOT a primary role of the endocrine system?
Which of the following is NOT a primary role of the endocrine system?
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Which type of glands produce hormones and lack ducts?
Which type of glands produce hormones and lack ducts?
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What is an example of a chemical messenger that acts on the same cells that secrete them?
What is an example of a chemical messenger that acts on the same cells that secrete them?
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Which of the following hormones is lipid-soluble?
Which of the following hormones is lipid-soluble?
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What class of hormones is synthesized from cholesterol?
What class of hormones is synthesized from cholesterol?
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Target cells for hormones are determined by:
Target cells for hormones are determined by:
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Which of the following mechanisms is used by amino acid–based hormones to exert their effects?
Which of the following mechanisms is used by amino acid–based hormones to exert their effects?
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What is one of the two main second-messenger systems involved in hormone action?
What is one of the two main second-messenger systems involved in hormone action?
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Which gland is considered a neuroendocrine organ?
Which gland is considered a neuroendocrine organ?
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Which type of hormone primarily acts on intracellular receptors?
Which type of hormone primarily acts on intracellular receptors?
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Which of the following organ systems does the endocrine system work closely with?
Which of the following organ systems does the endocrine system work closely with?
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What is the role of paracrines in the body?
What is the role of paracrines in the body?
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Which physiological activity might hormones influence?
Which physiological activity might hormones influence?
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What role does cAMP play in signaling mechanisms?
What role does cAMP play in signaling mechanisms?
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How does the phospholipase C pathway contribute to signal transduction?
How does the phospholipase C pathway contribute to signal transduction?
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What is the function of calcium ions in cellular signaling?
What is the function of calcium ions in cellular signaling?
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What initiates hormone release from endocrine glands?
What initiates hormone release from endocrine glands?
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What mechanism allows endocrine glands to respond to fluctuating nutrient levels?
What mechanism allows endocrine glands to respond to fluctuating nutrient levels?
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Which statement accurately describes how target cells respond to hormones?
Which statement accurately describes how target cells respond to hormones?
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What initiates the release of parathyroid hormone (PTH)?
What initiates the release of parathyroid hormone (PTH)?
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What is the primary role of tyrosine kinase enzymes in hormone signaling?
What is the primary role of tyrosine kinase enzymes in hormone signaling?
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What ensures that hormonal actions are reversed or stopped?
What ensures that hormonal actions are reversed or stopped?
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How does the nervous system influence hormonal activity under stress conditions?
How does the nervous system influence hormonal activity under stress conditions?
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What happens after a hormone binds to an intracellular receptor?
What happens after a hormone binds to an intracellular receptor?
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What is the end result of a signaling cascade initiated by adenylate cyclase?
What is the end result of a signaling cascade initiated by adenylate cyclase?
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What describes how hormones from target organs can affect the anterior pituitary?
What describes how hormones from target organs can affect the anterior pituitary?
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Study Notes
The Endocrine System
- The endocrine system works with the nervous system to coordinate and integrate bodily functions.
- It influences metabolic processes through hormones transported in the blood.
- These responses are slower but last longer than nervous system responses.
Endocrine System Overview
- The endocrine system controls and integrates:
- Reproduction
- Growth and development
- Maintaining blood electrolyte, water, and nutrient balance.
- Regulating cellular metabolism and energy balance.
- Mobilizing body defenses.
Exocrine Glands
- Produce non-hormonal substances (e.g., sweat, saliva).
- Have ducts to carry secretions to membrane surfaces.
Endocrine Glands
- Produce hormones.
- Lack ducts.
Endocrine Glands Examples
- Pituitary, thyroid, parathyroid, adrenal, and pineal glands
- Hypothalamus (a neuroendocrine organ)
- Some organs have both exocrine and endocrine functions (e.g., pancreas, gonads, placenta)
- Other tissues produce hormones (e.g., adipose cells, thymus, cells in the walls of small intestine, stomach, kidneys, and heart).
Hormone Chemical Structure
- Two main classes of hormones:
- Amino acid-based hormones (amino acid derivatives, peptides, and proteins)
- Steroid hormones (synthesized from cholesterol)
- Eicosanoids (are sometimes also treated as hormones, but mainly considered local chemical messengers)
Hormone Action
- Hormones act on target cells with specific receptors.
- Hormone action on target cells may alter plasma membrane permeability; stimulate synthesis of enzymes or proteins; activate or deactivate enzymes; induce secretory activity; and stimulate mitosis.
- Hormones act in one of two ways depending on their chemical nature and receptor location:
- Water-soluble hormones (all amino acid-based hormones except thyroid hormone) act on plasma membrane receptors via G protein second messengers.
- Lipid-soluble hormones (steroid and thyroid hormones) act on intracellular receptors that directly activate genes.
Hormone Release
- Blood hormone levels are controlled by negative feedback systems.
- Hormone release is triggered by:
- Humoral Stimuli: changing blood levels of ions and nutrients directly affecting hormone secretion.
- Neural Stimuli: nerve fibers stimulating hormone release.
- Hormonal Stimuli: hormones stimulating other endocrine organs to release hormones.
Target Cell Specificity
- Target cells must have specific receptors to which the hormone binds.
- Target cell activation depends on:
- Blood levels of the hormone
- Relative number of receptors on the cell
- Affinity of binding between the hormone and receptor
- Up-regulation: target cells form more receptors in response to low hormone levels
- Down-regulation: target cells lose receptors in response to high hormone levels.
Half-Life, Onset, and Duration of Hormone Activity
- Hormones circulate free or bound to plasma proteins.
- Hormones are removed from blood through degradation, by the kidneys, liver, or by other metabolic processes.
- Half-life: time required for the level of hormone in the blood to decrease by half; ranges from fractions of a minute to a week.
- Hormones have different response times, from immediate effects to effects that take hours or days to manifest.
Interaction of Hormones at Target Cells
- Synergism: more than one hormone produces the same effects on the target cell, causing amplification.
- Antagonism: one or more hormones oppose the action of another hormone.
- Permissiveness: one hormone cannot exert its effects without another hormone being present.
Hypothalamus and Pituitary Gland
- The hypothalamus is connected to the pituitary gland (hypophysis) via the infundibulum.
- The pituitary gland has two lobes:
- Posterior pituitary: composed of neural tissue, secretes neurohormones (oxytocin and antidiuretic hormone (ADH)).
- Anterior pituitary: composed of glandular tissue, secretes hormones in response to hormones from the hypothalamus (tropic hormones).
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Description
Explore the fundamentals of the endocrine system, its functions, and how it integrates with the nervous system to manage bodily processes. This quiz covers key concepts such as hormone production by endocrine glands, the role of exocrine glands, and examples of different glands in the body.
