Chapter 18 The Endocrine system Flashcards
The nervous and endocrine systems act together to do what?
Coordinate all systems in the body
The nervous system releases what? Opposed to the endocrine system?
Neurotransmitters and hormones
What are the molecules of the nervous systems?
Neurotransmitters released locally in response to nerve impulses
What are the sites of actions for the nervous system?
Close to site of release, at synapse; binds to receptors in postsynaptic membrane
What are the types of target cells for the nervous system?
Muscle fibers, glands cells, other neurons
What is the time to onset of action for the nervous system?
Typically within milliseconds
What is the duration of the nervous system control system?
Generally briefer (milliseconds)
What are the molecules involved in the endocrine system?
Hormones delivered to tissues throughout the body by blood
Where is the site of action for the endocrine system?
Far from site of release; binds to receptors on or in target cells
What are the target cells of the endocrine system?
cells throughout body
What is the time to onset of action for the endocrine system?
Seconds to hours or days
What is the duration of action for the endocrine system?
Generally longer (seconds to days)
What are exocrine glands?
- secrete their products into ducts
- None of these are hormones
Exocrine glands include what?
- sudoriferous (sweat) glands
- Sebaceous (oil) glands
- mucous glands
- Digestive glands
What are endocrine glands ?
- Secrete hormones
- do not have ducts; instead they secrete their hormones directly into the interstitial fluid that surrounds them
What are different types of endocrine glands?
- Pituitary
- Thyroid
- Parathyroid
- Adrenal
- Pineal glands
Just because a organ or tissue excrete hormones does that mean its part of the endocrine system?
Untrue, some organs contain secreting cells
What are secreting cells?
Secreting cells can be found in the
1. hypothalamus
2. thymus
3. pancreas
4. ovaries
5. testes
6. kidneys
7. stomach
8. Liver
9. small intestine
10. heart
11. adipose tissue
12. placenta
Hormones traveling throughout the body will only affect what?
target cells that posses specific protein receptors for the hormone
Receptors are continually doing what?
Being synthesized and broken down
What are two major classifications of hormones?
- Amino- based hormones
- Steroid hormones
Responses to the same hormone may vary depending on the hormone itself and the target cell. What are some of the responses?
- Synthesis of new molecules
- Changing permeability of the cell membrane
- Stimulating transport of a substance into or out of the cell
- Altering the rate of metabolic actions
- Causing contraction of smooth or cardiac muscle
What are lipid soluble hormones?
They bind to receptors within target cells
What are water soluble hormones?
Bind to receptors on the surface of the target cell
How target cell responds to a hormone is based on what?
- The hormones concentration in the blood
- The number of hormone receptors on the target cells
- Influences exerted by other hormones
- Some hormones work more effectively when a second hormone is present to assist them (synergistic effect)
- Some hormones oppose the actions of others (antagonist effect)
Hormones are secreted in what kind of bursts?
Short bursts
Secretions of hormones is regulated by what?
- Signals from the nervous system
- Chemical changes in the blood
- Other hormones
Most hormone regulation is achieved how?
Negative feedback
How many hormones operate via positive feedback?
Few
How are the hypothalamus and pituitary gland connected?
By the infundibulum
The anterior lobe (adenohypophysis) makes up how much weight of what?
75% of the pituitary gland and secretes 7 hormones
The posterior lobe (neurohypophysis) is made of what?
Neural tissue and releases two hormones made by the hypothalamus
The hypothalamus secretes what to control the hormones in the pituitary gland?
Releasing and inhibiting hormones. Which reach the pituitary gland via the hypophyseal portal system
What is HGH?
Human growth hormone is the most plentiful anterior pituitary hormone
How often is HGH released?
Every few hours by somatotrophs
What activates and deactivates HGH?
GHRH (Growth hormone releasing hormone) and GHIH (growth hormone inhibiting hormone)
What does the Anterior pituitary gland secrete?
- Human growth hormone (HGH)
- Thyroid stimulating hormone (TSH)
- Follicle stimulating hormone (FSH)
- Luteinizing hormone (LH)
- Prolactin (PRL)
- Adrenocorticotropic hormone (ACTH)
- Melanocyte stimulating hormone (MSH)
What are the principle actions of HGH?
Targets liver. Stimulates liver, muscle, cartilage, bone, and other tissues to synthesize and secrete insulin-like growth factors, which in turn promote growth of body tissues.
What are the principle actions of Thyroid stimulating hormone (TSH)?
Stimulates synthesis and secretion of thyroid hormones by thyroid gland
What are the principle actions of follicle stimulating hormones (FSH)?
In females, initiates development of oocytes and induces ovarian secretion of estrogens. In males, stimulates testes to produce sperm
What is luteinizing hormone (LH)?
In females, stimulates secretion of estrogens and progesterone, ovulation, and formation of corpus luteum. IN males stimulates testes to produce testosterone
What are the principle actions of prolactin (PRL)?
Together with other hormones promotes milk production by mammary glands
What are the principle actions of Adrenocorticotropic hormone (ACTH)?
Stimulates secretion of glucocorticoids (mainly cortisol) by suprarenal cortex
What are the main actions of Melanocyte-stimulating hormone (MSH)?
Exact role in human is unknown by may influence brain activity; when present in excess, can cause darkening of skin.
What does the posterior pituitary gland do?
The posterior pituitary gland does not synthesize any hormones, but stores and releases from axon terminals two hormones produced by the neurosecretory cells of the hypothalamus.
What is stored and released by the posterior pituitary gland?
- Oxytocin
- Antidiuretic hormone
What is oxytocin?
Stimulates contract of smooth muscle cells of uterus during childbirth; stimualtes contraction of myoepithelial cells in mammary glands to cause milke ejection
What is antidiuretic hormone?
Conserves body water by decreasing urine volume; decreases water loss through perspiration; raises blood pressure by constricting arterioles
What is the thyroid gland?
The butterfly shaped gland located inferior to the larynx and anterior to the trachea.
How many lobes does the thyroid have?
It has two. A left and right lateral lobes connecting by a isthmus
Follicular cells are stimulated by what?
TSH to produce Thyroxine(T4) and triiodothyronine (T3) known as thyroid hormones
Parafollicular cells produce what?
The hormone calcitonin to help regulate calcium homeostasis
T3 and T4 are synthesized and secreted in how many steps?
A 8 step process
What do Thyroid hormones do?
- increase basal metabolic rate (BMR)
- Help maintain normal body temperature
- Stimulate protein synthesis
- Increase the use of glucose and fatty acids for ATP production
- Upregulate beta receptors that attach to catecholamines
- work with HGH and insulin to accelerate body growth
What stimulates synthesis and release of thyroid hormones?
Two things
1. Thyrotropin- releasing hormone (TPH) from the hypothalamus
2. Thyroid stimulating hormone (TSH) from the anterior pituitary
How many steps does it take to stimulate and synthesize the release of thyroid hormones?
5 steps
What is the 8 steps T3 and T4 synthetization and secretion process.
- Iodide trapping
- Synthesis of TGB
- Oxidation of Iodide
- Iodination of tyrosine
- coupling of T1 and T2
- Pinocytosis and digestion of colloids
- secretion of thyroid hormones
- Transport in blood
What is the 5 step process to stimulate and release thyroid hormones?
- Stimulus: low level of thyroid hormones (T3 and T4) or low metabolic rate.
- Controlled condition: TRH in hypothalamus
- Receptors: Anterior pituitary
- Control center: Thyroid follicle is is stimulated to release hormones (T3 and T4)
- Effectors: Most body cells
Finally a response followed by a return to homeostasis
What are the principle actions of T3 and T4 or thyroid hormones from follicular cells?
- Increase basal metabolic rate
- stimulate synthesis of proteins
- increase us of glucose and fatty acids for ATP productions
- Increase lipolysis
- Enhance cholesterol excretion
- Accelerate body growth
- contribute to development of nervous system
What is the control of secretion for T3, T4, or thyroid hormones from follicular cells?
Secretion is increased by thyrotropin releasing hormone (TRH), which stimulates release of thyroid stimulating hormone (TSH) in response to low thyroid hormone levels, low metabolic rate, cold pregnancy, and high altitudes; TRH and TSH secretions are inhibited in response to high thyroid hormone levels; high iodine level suppresses T3/T4 secretion
What is the control of secretion for calcitonin (CT) from thyrocytes?
High blood CA levels stimulate secretion; low blood CA levels inhibit secretion
What are the principle actions of Calcitonin (CT)?
Lowers blood levels of CA and HPO by inhibiting bone resorption by osteoclasts and by accelerating uptake of calcium and phosphates into bone extracellular matrix
Where is the parathyroid glands located?
On the posterior aspect of each lobe of the the thyroid glands.
How many parathyroid glands are there?
- One superior and one inferior
What two types of cells does the parathyroid cells consist of?
- Chief cells (principle cells)
- Oxyphil cells
What are Chief cells (principle cells)?
They produce parathyroid hormones
What are oxyphil cells?
Function is not known in the normal parathyroid glands, but which secrete excess PTH in cases of parathyroid cancer
Calcitonin produced by the thyroid gland works in conjunction with what to regulate calcium homeostasis?
PTH and Calcitriol
What is the control of secretion for parathyroid hormone (PTH)?
Low blood CA levels stimulate secretion: high blood CA levels inhibit secretion
What are the principle actions of parathyroid glands?
1.Increases blood CA and Mg levels and decreases HPO4 level
2. increase bone reabsorption by osteoclasts
3. increases CA reabsorption and HPO4 excretion by kidneys
4. promotes formation of calcitriol which increases rate of dietary CA and Mg absorption
Where are the suprarenal glands located?
On top of each kidney
What are the suprarenal glands divided into?
Outer cortex and inner medulla
The cortex of the suprarenal glands are divided into what 3 regions?
- The zona glomerulosa
- The zona fasciculata
- The zona reticularis
What does the zona glomerulosa do?
Secretes hormones called mineralocorticoids used to regulate mineral homeostasis, the most common is aldosterone
The zona fasciculata does what?
secretes hormones called glucocorticoids that affect glucose homeostasis cortisol
The zona reticularis does what?
Secretes gonadocorticoids, weak androgens
The adrenal medulla is stimulated by what?
Sympathetic preganglionic neurons of the autonomic nervous system (ANS)
What are chromaffin cells?
They secrete epinephrine (adrenaline) and norepinephrine (noradrenaline) both of which are involved in the fight or flight response.
What is the control of secretion for mineralocorticoids?
Increased blood K level and angiotensin stimulate secretion
What is the principle action of mineralocorticoids?
Increase blood levels of Na and water; decrease blood level of K
What are glucocorticoids principle actions?
Increase protein breakdown (Except in liver), stimulate gluconeogenesis and lipolysis, provide resistance to stress, dampen inflammation, depress immune response
What is the control of secretion for glucocorticoids?
ACTH stimulates release; corticotropin releasing hormone (CRH) promotes ACTH secretion in response to stress and low blood levels of glucocorticoids
What are androgens principle actions?
Assist in early growth of axillary and pubic hair in both sexes; in females contribute to their libido and are sources of estrogen after menopause
What is the control of secretion for androgens?
ACTH stimulates secretion
What is the control of secretion for epinephrine?
Sympathetic preganglionic neurons release acetylcholine, which stimulates secretion
What are the principle actions for epinephrine?
Enhance effects of sympathetic part of autonomic nervous system during stress
Where is the pancreas located?
In the curve of the duodenum and its both a endocrine and exocrine gland
Almost all of the exocrine cells of the pancreas are arranged in clusters called what?
Acini
Acini produce what?
Digestive enzymes that are delivered to the gastrointestinal tract through ducts
What is the pancreatic islets?
Clusters of endocrine tissue
The islets of the pancreas contain which secreting cells?
- insulin
- Glucagon
What is the control of secretion for insulin?
Increased blood glucose, acetylcholine, arginine and leucine, glucagon, GIP, GH, and ACT. Somatostatin inhibits secretion
What are the principle actions of insulin?
Lowers blood glucose levels by acceleration transport of glucose into cells, converting glucose into glycogen, and decreasing glycogenolysis and gluconeogenesis; increases lipogenesis and stimulates protein synthesis
What are control of secretion for glucagon?
Decreased blood levels of glucose, exercise, and mainly protein meals stimulate secretion of somatostatin and insulin inhibit secretion
What are the principle actions of glucagon?
Raises blood glucose level by accelerating breakdown of glycogen into glucose in liver, converting other nutrients into glucose in live and releasing glucose into blood.
