Endocrine System (Pt. 2) Flashcards
What types of hormones does the hypothalamus secrete to control the pituitary gland?
Releasing and inhibiting hormones
What is the main function of these hypothalamic hormones?
They control the release of hormones by the pituitary gland
How do hormones from the hypothalamus reach the pituitary gland?
Via the hypophyseal portal system
What is the hypophyseal portal system?
A specialized blood vessel system that connects the hypothalamus to the pituitary gland
Why is the hypophyseal portal system important?
allows for direct delivery of hypothalamic hormones to the pituitary, enabling precise control
What are releasing hormones?
Hormones that stimulate the pituitary to release specific hormones
What are inhibiting hormones?
Hormones that prevent or reduce the release of specific pituitary hormones
How does this system demonstrate the hierarchical nature of the endocrine system?
It shows how one gland (hypothalamus) controls another (pituitary) through hormone signaling
Why is the pituitary often called the “master gland”?
Because its hormones control many other endocrine glands, but it’s itself controlled by the hypothalamus
Why is the connection between the hypothalamus and pituitary gland important?
It coordinates the release of hormones that regulate many bodily functions
What regulates the pituitary gland?
The hypothalamus
How many hormones does the hypothalamus produce to regulate the pituitary?
At least nine
What areas do hypothalamic hormones affect?
Growth, development, metabolism, and homeostasis
What is the hypophyseal portal system?
A specialized network of blood vessels connecting the hypothalamus to the anterior pituitary gland
What’s the main function of the hypophyseal portal system?
It allows quick and direct transport of hypothalamic hormones to the pituitary gland
Why is the hypophyseal portal system important for hormone regulation?
It ensures precise regulation of hormone release, allowing immediate hypothalamic influence on the pituitary
What percentage of the pituitary gland’s weight does the anterior lobe make up?
75%
What does the anterior lobe of the pituitary gland secrete?
Hormones
What are hormones that target other endocrine glands called?
Tropic hormones
What type of tissue is the posterior lobe of the pituitary gland made of?
Neural tissue
How many hormones does the posterior lobe store and release?
Two
Where are the hormones stored in the posterior lobe produced?
The hypothalamus
Name the two hormones stored and released by the posterior lobe of the pituitary gland.
Oxytocin and antidiuretic hormone (ADH)
What is the main function of the anterior pituitary?
To secrete hormones that regulate various body functions, including growth and reproduction
What hormone do somatotrophic cells secrete?
Growth hormone (GH)
Which cells secrete thyroid-stimulating hormone (TSH)?
Thyrotrophic cells
What hormones are secreted by gonadotrophic cells?
Luteinizing hormone (LH) and follicle-stimulating hormone (FSH)
What hormone do prolactin cells secrete?
Prolactin (PRL)
Which hormones are secreted by corticotrophic cells?
Adrenocorticotropic hormone (ACTH) and melanocyte-stimulating hormone (MSH)
Does the posterior pituitary produce its own hormones?
No, it stores and releases hormones produced elsewhere
Which two hormones does the posterior pituitary store and release?
Oxytocin and antidiuretic hormone (ADH)/vasopressin
What is the function of oxytocin?
It is involved in childbirth and lactation
What does antidiuretic hormone (ADH)/vasopressin regulate?
Water balance and blood pressure
What is the composition of the posterior pituitary?
Axons and terminals of over 10,000 neurosecretory cells originating in the hypothalamus
How do hormones reach the posterior pituitary from the hypothalamus?
They travel down the axons through the hypothalamic–hypophyseal tract
list the hormones of the anterior pituitary
- Growth Hormone (GH)
- Thyroid-Stimulating hormone (TSH)
- Follicle stimulating hormones (FSH)
- Luteinizing hormone (LH)
- Prolactin (PRL)
- Adrenocorticotropic hormone (ACTH)
- Melanocyte-Stimulating hormone (MSH)
What is GH secreted by?
Somatotrophic cells.
GH - Hypothalamic Releasing Hormone (Stimulates Secretion)
Growth hormone-releasing hormone (GHRH), also known as somatocrinin.
GH - Hypothalamic Inhibiting Hormone (Suppresses Secretion)
Growth hormone-inhibiting hormone (GHIH), also known as somatostatin.
what is TSH secreted by?
Thyrotrophic cells.
Which hypothalamic releasing hormone stimulates the secretion of thyroid-stimulating hormone (TSH)?
Thyrotropin-releasing hormone (TRH)
What hormone is secreted by gonadotrophs?
Follicle-stimulating hormone (FSH) and Luteinizing hormone (LH)
Which hypothalamic releasing hormone stimulates the secretion of FSH and LH?
Gonadotropin-releasing hormone (GnRH)
What hormone is secreted by lactotrophs?
Prolactin (PRL)
Which hypothalamic releasing hormone stimulates the secretion of prolactin (PRL)?
Prolactin-releasing hormone (PRH)
Which hypothalamic inhibiting hormone suppresses the secretion of prolactin (PRL)?
Prolactin-inhibiting hormone (PIH), also known as dopamine
What hormone is secreted by corticotrophs?
Adrenocorticotropic hormone (ACTH)
Which hypothalamic releasing hormone stimulates the secretion of adrenocorticotropic hormone (ACTH)?
Corticotropin-releasing hormone (CRH)
which cells secrete MSH? (melanocyte stimulating hormone)
Corticotropic cells
MSH - Hypothalamic Releasing Hormone (Stimulates Secretion)
Corticotropin-releasing hormone (CRH).
MSH - Hypothalamic Inhibiting Hormone (Suppresses Secretion)
Dopamine
Luteinizing hormone (LH) secreted by:
Gonadotrophic cells
LH - Hypothalamic Releasing Hormone (Stimulates Secretion)
Gonadotropin-releasing hormone (GnRH).
Prolactin (PRL) - secreted by:
prolactin cells
Prolactin (PRL) - Hypothalamic Releasing Hormone (Stimulates Secretion)
Prolactin-releasing hormone (PRH).*
Prolactin (PRL) - Hypothalamic Inhibiting Hormone (Suppresses Secretion)
Prolactin-inhibiting hormone (PIH), which is dopamine.
the anterior pituitary gland secretes:
Growth hormone (GH)
Thyroid-stimulating hormone (TSH)
Follicle-stimulating hormone (FSH)
Luteinizing hormone (LH)
Prolactin (PRL)
Adrenocorticotropic hormone (ACTH)
Melanocyte-stimulating hormone (MSH)
Growth Hormone (GH)
Stimulates liver, muscle, cartilage bone and other tissues to synthesize and secrete insulin-like growth factors, which in turn promote growth of body tissues.
Follicle-Stimulating Hormone (FSH)
Purpose: Essential for reproduction.
In Women: It helps control the menstrual cycle and promotes the growth of eggs in the ovaries.
In Men: It aids in the production of sperm.
Thyroid-Stimulating Hormone (TSH)
Purpose: Signals the thyroid gland to produce hormones that control your body’s metabolism, which is how your body uses energy.
Luteinizing Hormone (LH)
Purpose: Also important for reproduction.
In Women: It works with FSH to ensure normal functioning of the ovaries and triggers ovulation.
In Men: It stimulates the production of testosterone from the testes.
Prolactin (PRL)
Purpose: Primarily associated with milk production after childbirth.
Additional Role: It has over 300 different functions in the body, including roles in regulating the immune system and behavior.
Adrenocorticotropic Hormone (ACTH)
Purpose: Stimulates the adrenal glands to produce cortisol, a hormone that helps respond to stress, regulate metabolism, and control inflammation.
Melanocyte-Stimulating Hormone (MSH)
Purpose: Influences pigmentation (color) of the skin.
Additional Role: May play a role in appetite and sexual arousal, although these roles are less understood.
what hormone acts directly on target cells to enhance lipolysis and decrease glucose uptake?
Growth Hormone (GH)
stimulates synthesis and secretion of thyroid hormones by thyroid gland:
thyroid-stimulating hormone (TSH)
in females, initiates development of oocytes and induces ovarian secretion of estrogen.
in males, stimulates testes to produce sperm
follicle stimulating hormone (FSH)
in females, stimulates secretion of estrogen and progesterone, ovulation, and formation of corpus luteum. In males, stimulates testes to produce testosterone.
luteinizing hormone
How does Growth Hormone (GH) promote tissue growth?
By stimulating cells to multiply and increasing cell size, particularly in bones and muscles
What does GH stimulate the liver to produce?
Insulin-like growth factors (IGF-I and IGF-II)
How does GH affect protein synthesis?
It increases DNA transcription to mRNA, enhancing protein synthesis
What is the effect of GH on amino acid transport and protein catabolism?
It boosts amino acid transport into cells and decreases protein breakdown
How does GH influence lipid metabolism?
It stimulates fat cells to release free fatty acids (FFAs) and glycerol
What is the “protein sparing” effect of GH?
It promotes the use of fats for energy, sparing proteins for growth and repair
How does GH affect carbohydrate metabolism?
reduces glucose use by body cells and stimulates liver to produce more glucose
What is the “glucose sparing effect” of GH?
It ensures the brain has enough glucose by reducing its use in other body cells
How does GH influence electrolyte balance?
It promotes retention of sodium, potassium, and chloride ions, and increases calcium absorption
What are the main electrolytes affected by GH?
Sodium (Na+), potassium (K+), chloride (Cl-), and calcium (Ca2+)
Q: What role does Growth Hormone (GH) play in tissue growth?
GH stimulates cell multiplication and increases cell size, promoting the growth of bones and muscles.
How does GH affect the liver?
GH stimulates the liver to produce insulin-like growth factors (IGF-I and IGF-II), which promote cell growth and development.
Q: How does GH affect amino acid transport and protein catabolism?
A: GH boosts amino acid transport into cells and decreases protein breakdown, contributing to muscle growth and maintenance.
Q: How does GH affect carbohydrate metabolism?
GH reduces glucose use by body cells, ensuring more glucose is available for the brain and stimulating the liver to release more glucose into the blood.
Q: What is the role of GH in lipid metabolism?
A: GH stimulates fat cells to release free fatty acids (FFAs) and glycerol, promoting the use of fats for energy and sparing proteins for growth and repair.
Q: What is the role of GH in maintaining electrolyte balance?
A: GH promotes the retention of sodium (Na+), potassium (K+), and chloride (Cl-) ions, and increases calcium (Ca2+) absorption, which are important for cellular functions.
What is the trend as exercise intensity increases?
there is a significant increase in plasma growth hormone levels.
How do growth hormone levels respond to low-intensity exercise (below 20% VO2 max)?
A: At low intensity, there is little to no change in growth hormone levels.
Q: What happens to growth hormone levels during moderate to high-intensity exercise, especially approaching 100% VO2 max?
A: Growth hormone levels increase significantly as exercise intensity approaches maximal levels (100% VO2 max).
relationship between intense physical activity and growth hormone release:
intense physical activity stimulates the release of growth hormone, which aids in metabolism, muscle growth, and recovery.
Q: What role does growth hormone (GH) play in childhood and adolescence?
A: GH helps bones, cartilage, and muscles grow, which makes kids and teens grow taller and stronger.
Q: How does GH affect growth at the epiphyseal plates in children and adolescents?
A: GH promotes growth at the epiphyseal plates, contributing to height increases during growth spurts.
Q: What is the role of GH in adulthood?
A: In adults, GH helps maintain bone health by increasing osteoblast activity, leading to thicker bones and continuous bone remodeling.
Q: How do GH levels change with age?
A: GH levels decrease with age, and by age 75, GH levels are about a quarter of what they were during adolescence.
Q: When are GH levels higher throughout the day?
A: GH levels are higher during deep sleep, after high-protein meals, and after vigorous exercise.
Q: Why are GH levels lower after high-carbohydrate meals?
A: GH levels are lower after high-carbohydrate meals because carbohydrates provide quick energy, reducing the need for GH’s energy and tissue repair benefits.
Thyroid Gland
The thyroid gland is a butterfly-shaped gland located inferior to the larynx and anterior to the trachea
Q: What does TSH stimulate the thyroid gland to produce?
A: TSH stimulates the thyroid gland to produce thyroxine (T4) and triiodothyronine (T3).
Q: How do T3 and T4 affect basal metabolic rate (BMR)?
A: T3 and T4 elevate BMR, increasing the body’s energy use at rest to maintain vital functions.
Q: What role do T3 and T4 play in body temperature regulation?
A: T3 and T4 help maintain normal body temperature by increasing heat production through elevated BMR.
Q: How do thyroid hormones affect protein synthesis?
A: T3 and T4 stimulate protein synthesis, aiding in growth, tissue repair, and maintaining muscle mass.
Q: How do T3 and T4 enhance energy production in cells?
A: They increase the use of glucose and fatty acids for ATP production, providing energy for cellular functions.
Q: What effect do T3 and T4 have on beta (β) receptors?
T3 and T4 upregulate beta receptors, making tissues more responsive to catecholamines like adrenaline.
Q: How do thyroid hormones work with GH and insulin?
T3 and T4 work with GH and insulin to accelerate body growth, supporting bone development and protein production.
Q: What regulates the secretion of TSH?
A: TSH secretion is controlled by thyrotropin-releasing hormone (TRH) from the hypothalamus.
Q: What is the role of the negative feedback loop in TSH regulation?
A: High levels of T3 and T4 signal the hypothalamus to reduce TRH production, which lowers TSH release.
Q: Is there a specific hormone that inhibits TSH directly?
A: No, there isn’t a specific hormone that directly inhibits TSH.
what hormone (produced by the thyroid gland) helps regulate calcium homeostasis and bone maintnance?
calcitonin
Where is calcitonin produced?
Calcitonin is produced by the C cells (parafollicular cells) in the thyroid gland.
What is the main function of calcitonin?
Calcitonin helps regulate calcium levels in the blood by lowering them when they are too high.
How is calcitonin secretion regulated?
Calcitonin is secreted when blood calcium levels are high, in a negative feedback system to lower these levels.
What triggers the release of calcitonin, and what effect does it have?
High blood calcium levels trigger the thyroid gland to release calcitonin, which inhibits osteoclasts and decreases blood calcium levels by incorporating calcium into bones.
What triggers the release of parathyroid hormone (PTH), and what effect does it have?
Low blood calcium levels trigger the parathyroid glands to release PTH, which stimulates osteoclasts to release calcium from bones and helps the kidneys reabsorb calcium, raising blood calcium levels.
How do calcitonin and PTH maintain calcium homeostasis?
Calcitonin lowers high calcium levels, while PTH raises low calcium levels, both working through a negative feedback loop to keep calcium within a healthy range.
