Hormones Flashcards
Endocrine system
The endocrine system is a network of glands and organs that produce, store, and secrete hormones. These hormones regulate various bodily functions, including growth, metabolism, reproduction, and mood. Key components include:
Glands: Such as the pituitary, thyroid, adrenal glands, and pancreas.
Hormones: Chemical messengers like insulin, adrenaline, and thyroid hormones.
Functions: Regulating processes like metabolism, blood sugar levels, stress response, and reproductive cycles.
The endocrine system works closely with the nervous system to maintain homeostasis and coordinate complex physiological processes.
Hormones
Hormones are chemical messengers produced by glands in the endocrine system. Hormones trigger changes in in target cells differently depending on whether the hormone is water-soluble or lipid-soluble. Water-soluble hormones trigger responses without entering the cell whereas lipid-soluble lipids trigger responses after entering a cell.
They travel through the bloodstream to tissues and organs, where they regulate various physiological processes. Key functions include:
Growth and Development: Hormones like growth hormone and thyroid hormones regulate physical and mental development.
Metabolism: Insulin and glucagon control blood sugar levels, while thyroid hormones influence metabolic rate.
etc.
A hormone that binds to a plasma membrane receptor
(water-soluble hormones that cannot pass the phospholipid bilayer)
1) A water-soluble hormone binds to to a specific receptor protein in the plasma memmbrane of the target cell.
The binding activates the receptor protein.
2) The previous step initiates a signal transduction pathway: a series of changes to molecules that converts a chemical message from the outside of the cell to a specific response inside the cell.
3) The final relay molecule activates a protein that either carries out a response in the cytoplasm (such as activating an enzyme) or affects gene regulation in the nucleus (such as turning genes on and off).
A hormone that binds to an intracellular receptor
(Lipid-soluble hormones that can pass the phospholipid bilayer)
1) A lipid-soluble hormone enters a cell by diffusing through the plasma membrane. If the cell is a target cell, the hormone…
2) Binds to a receptor protein in the cytoplasm or nucleus. Rather than triggering a signal transduction pathway, the receptor itself carries the hormone´s signal.
3) The hormone-receptor complex attaches to specific sites on the cell´s DNA in the nucleus.
4) The binding to DNA turns specific genes on or off.
Hypothalamus
The hypothalamus is a small but crucial region of the brain located below the thalamus and above the pituitary gland. It plays a key role in regulating various bodily functions, including:
Homeostasis: Maintains the body’s internal balance by regulating temperature, thirst, hunger, and circadian rhythms.
Endocrine Control: Produces releasing and inhibiting hormones that control the release of hormones from the pituitary gland.
The hypothalamus acts as a link between the nervous and endocrine systems, ensuring coordinated control over vital physiological processes.
Pituitary gland
The pituitary gland, often referred to as the “master gland,” is a pea-sized gland located at the base of the brain, just below the hypothalamus. It plays a crucial role in regulating various endocrine functions through its two main parts: Anterior Pituitary and Posterior Pituitary
Anterior Pituitary
Anterior Pituitary: Produces and secretes hormones such as:
Growth Hormone (GH): Stimulates growth and cell reproduction.
Thyroid-Stimulating Hormone (TSH): Stimulates the thyroid gland to produce thyroid hormones.
Adrenocorticotropic Hormone (ACTH): Stimulates the adrenal glands to produce cortisol.
Prolactin: Promotes milk production.
Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone
(LH): Regulate reproductive processes.
Posterior Pituitary
Posterior Pituitary: Stores and releases hormones produced by the hypothalamus, such as:
Oxytocin: Promotes uterine contractions during childbirth and milk ejection during breastfeeding.
Antidiuretic Hormone (ADH): Regulates water balance in the body by increasing water reabsorption in the kidneys.
The pituitary gland is controlled by the hypothalamus and plays a vital role in maintaining homeostasis and coordinating the endocrine system.
Thyroid gland and TSH
The thyroid gland is a butterfly-shaped gland located in the front of the neck, below the larynx. It is part of the endocrine system and plays a crucial role in regulating metabolism, growth, and development. The thyroid gland is the only organ in the body that actively takes up iodine to produce thyroid hormones.
Thyroid-Stimulating Hormone (TSH):
- TSH is produced by the anterior pituitary gland.
- It stimulates the thyroid gland to produce and release thyroid hormones.
- TSH regulates the thyroid gland’s activity and ensures proper hormone levels in the bloodstream.
Hyperthyroidism
A condition where the thyroid gland is overactive, producing excessive thyroid hormones. Symptoms include weight loss, rapid heartbeat, sweating, and anxiety.
Treated with low dose of radioactive iodine because it selectively targets and destroys thyroid tissue, reducing hormone production.
Hypothyroidism
A condition where the thyroid gland is underactive, producing insufficient thyroid hormones. Symptoms include weight gain, fatigue, depression, and cold intolerance.
Treated with iodine because the hormone cant be synthesized without it.
The pancreas and blood glucose
The pancreas plays a crucial role in regulating blood glucose levels through the production and secretion of two key hormones:
Insulin: Produced by beta cells in the pancreas, insulin helps lower blood glucose levels by facilitating the uptake of glucose into cells for energy production and storage. It promotes the conversion of glucose into glycogen in the liver and muscles, lowering blood sugar levels.
Glucagon: Produced by alpha cells in the pancreas. It helps raise blood glucose levels by stimulating the liver to convert stored glycogen into glucose and release it into the bloodstream.
Together, insulin and glucagon maintain blood glucose homeostasis, ensuring that cells receive an adequate supply of glucose for energy while preventing excessively high or low blood sugar levels. Dysregulation of insulin and glucagon secretion can lead to conditions such as diabetes mellitus, characterized by abnormal blood glucose levels.
How the adrenal glands control our response to stress
The adrenal glands play a pivotal role in the body’s response to stress by releasing hormones that prepare the body for “fight or flight” responses. The process involves the following steps:
Perception of Stress: When the brain perceives a stressor, it activates the hypothalamus, a region in the brain.
Hypothalamic Response: The hypothalamus releases corticotropin-releasing hormone (CRH) into the bloodstream.
Pituitary Gland Activation: CRH stimulates the pituitary gland, located at the base of the brain, to release adrenocorticotropic hormone (ACTH) into the bloodstream.
Adrenal Gland Activation: ACTH travels through the bloodstream and stimulates the adrenal glands, located atop the kidneys, to release hormones.
Adrenal Medulla Response: The adrenal medulla, the inner part of the adrenal gland, releases adrenaline (epinephrine) and noradrenaline (norepinephrine) rapidly into the bloodstream.
Adrenal Cortex Response (longterm): The adrenal cortex, the outer part of the adrenal gland, releases glucocorticoids, such as cortisol, more slowly into the bloodstream.
Physiological Changes: The hormones released by the adrenal glands trigger physiological changes in the body, such as increased heart rate, elevated blood pressure, heightened alertness, enhanced metabolism, and suppressed non-essential functions like digestion and immune response.
Stress Response: Collectively, these changes prepare the body to respond effectively to the stressor, either by confronting it (fight) or fleeing from it (flight).
The adrenal glands’ coordinated release of hormones in response to stress ensures the body’s ability to adapt and cope with challenging situations.
Male gonads and sex hormones
The gonads are the primary reproductive organs responsible for producing sex cells (gametes) and sex hormones. In males, the gonads are the testes.
Testes (Male Gonads):
Testosterone: The primary male sex hormone produced by the Leydig cells in the testes. Testosterone is responsible for the development of male secondary sexual characteristics, such as facial hair, deep voice, and muscle growth. It also plays a role in sperm production (spermatogenesis).
Female gonads adn sex hormones
The gonads are the primary reproductive organs responsible for producing sex cells (gametes) and sex hormones. In females, they are the ovaries. These organs produce the following sex hormones:
Ovaries (Female Gonads):
Estrogen: The primary female sex hormone produced by the follicular cells in the ovaries. Estrogen is responsible for the development of female secondary sexual characteristics, such as breast development, widening of hips, and regulation of the menstrual cycle. It also plays a role in bone health and cardiovascular function.
Progesterone: Produced by the corpus luteum in the ovaries during the second half of the menstrual cycle and during pregnancy. Progesterone is essential for the maintenance of pregnancy and regulation of the menstrual cycle.
