Module 6 - The Endocrine System Flashcards
What does the endocrine system do?
The endocrine system (along with the nervous system), coordinates the various activities of body parts by utilizing chemical messengers to coordinate these activities.
How does the nervous system send messages to other parts of the body?
Neurons release neurotransmitters that influence the excitability of the other neurons.
How does the endocrine system send messages to other parts of the body?
The endocrine system utilizes hormones, chemical messengers, that are typically released directly into the bloodstream. Once the hormones are in the bloodstream, they interact with cells throughout the body.
Does the nervous system or the endocrine system react quicker to internal and external stimuli?
The nervous systems reacts quicker than the endocrine system.
Why does the endocrine system take longer to react to stimuli (both internal and external)?
Because the hormone needs to be produced, released into the bloodstream, and travel through the circulatory system until it finds its target organ.
How does a hormone know what it’s target organ is?
Hormones know what their target organs are by trial and error. Only specific cells can react to specific hormones. Cells will only react to a hormone if it is able to connect with that particular cell’s surface receptors. Basically, the receptors combine with the hormone in a lock-and-key manner (it has to be the right fit) so certain cells respond to one hormone and not to another.
Define a hormone
an organic chemical produced by one set of cells that affects a different set of cells.
What are the two main categories of hormones?
Peptide hormones
Steroid hormones
Define peptide hormone
derived from proteins, peptides, or catecholamines. This type of hormone activate existing enzymes in the cell. They act quickly but for a short period of time.
Define Steroid hormone
derived from cholesterol by a series of metabolic reactions. Act slower than peptides because it takes more time to synthesize new proteins than it does to activate enzymes that are already present in the cell. Last longer than peptide hormones because steroid hormones actually create new proteins for the cell.
Explain the difference between a peptide and a steroid hormone:
Peptide hormones act quickly but only last for a short period of time. They activate existing enzymes in the cell, whereas, steroid hormones act slowly, but they last longer. This is because they can create new proteins for the cell due to the activation of specific genes that lead to protein synthesis. Basically, steroid hormones can change the function of a cell, where peptides can only activate the enzymes already present.
What is responsible for secreting hormones?
glands and organs.
What are the two types of glands?
Endocrine glands
Exocrine glands
Define endocrine gland
A ductless gland responsible for secreting its contents directly into the bloodstream for distribution throughout the body.
Define exocrine gland
A gland with ducts that secrete its contents into epithelial surface.
Provide an example of an exocrine gland
Salivary glands. They secrete salivary amylase into the mouth.
What are primary endocrine organs?
Primary endocrine organ’s main job is to secrete hormones that chemically regulate body functions.
List 7 primary endocrine organs
Hypothalamus Pituitary gland Pineal gland Thyroid gland Parathyroid glands Adrenal glands Pancreas
What 3 primary endocrine glands are located within the brain?
Hypothalamus
Pineal gland
Pituitary gland
Identify the following (3) glands located within the brain (refer to figure 6.1 brain glands)
- Hypothalamus
- Pituitary gland
- Pineal gland
Where are the adrenal glands located?
superiorly to each kidney
Where is the thyroid gland located?
Large gland in the neck where it is attached to the trachea just below the larynx
How many parathyroid glands are there?
4
Where are parathyroid glands located?
They are embedded into the surface of the thyroid gland.
Describe the location of the pancreas
It is a long organ that lies transversely in the abdomen between the kidneys and near the duodenum of the small intestine
Identify the following primary endocrine organs located throughout the body (refer to figure 6.2 primary endocrine organs)
- Thyroid
- Adrenal gland
- Kidney
- Adrenal gland (L)
- Pancreas
Identify 1 and 2 on figure 6.3
- Thyroid
- Parathyroid (L)
* remember this figure is a posterior view of the thyroid gland.
What is a secondary endocrine organ?
These are organs that secrete hormones as a secondary function (as opposed to those whose primary function is hormone secretion)
What are the 4 secondary endocrine glands?
- Thymus
- Heart
- Kidneys
- Gonads (testes or ovaries)
Define thymus
lobular gland that lies in the upper thoracic cavity
Identify the following secondary endocrine organs (refer to figure 6.4 Secondary endocrine organs)
- Thymus
- Heart
- Kidneys
- Testes
Describe the negative feedback system in the endocrine system (refer to figure 1 Negative feedback system thermostat example)
Mechanism that controls most hormones.
Negative feedback is a way of “turning off” hormone production and keeping hormones within their proper range.
Define homeostasis
Also referred to as set-point. Which is a range in which the body acts to maintain all its levels for function.
Describe the positive feedback system within the endocrine system
This system enhances or increases the amount of the hormone that is regulated.
Provide an example of a hormone that is controlled through negative feedback
ADH (antidiuretic hormone) is used to dilute the blood. Once the blood is dilute, the hypothalamus detects the dilute levels and shuts off the release of ADH.
Provide an example of a hormone that works through the action of positive feedback
Oxytocin, a hormone involved in childbirth that causes the uterus to contract. The action of the uterus contracting causes more oxytocin to be released. This enhances the effect of the uterus contractions, causing more oxytocin to be released. The positive feedback loop is stopped once the baby is born and the uterus no longer needs to contract, stopping the production of oxytocin.
Define hypothalamus
the portion of the brain that regulates the internal environment and homeostasis.
What types of things does the hypothalamus help regulate?
- Control of heart rate
- body temperature
- water balance
- the glandular secretions of the pituitary gland
Where is the pituitary gland located?
The pituitary gland lies just below the hypothalamus and is divided into two portions called the posterior and anterior pituitary.
Define posterior pituitary
Connected to the hypothalamus by means of a stalk-like structure.
What are neurosecretory cells?
These are neurons located in the hypothalamus that respond to neurotransmitters and produce hormones that are stored and released from the posterior pituitary.
What are the 2 major hormones stored in the axon endings in the posterior pituitary?
- Antidiuretic hormone (ADH) a.k.a. vasopressin.
2. Oxytocin
Define ADH
ADH stands for antidiuretic hormone.
Made in hypothalamus and stored in posterior pituitary.
This hormone promotes the reabsorption of water from the collecting ducts, which receive urine produced by nephrons within the kidneys. As the blood becomes dilute, the hormone is no longer released until it is needed again.
Basically, it is responsible for regulating the amount of water in the body. It controls the amount of water the kidneys reabsorb as they filter waste from the blood.
Define Oxytocin
Made in hypothalamus and stored in posterior pituitary.
Causes uterus to contract through a positive feedback system. This hormone can be given artificially to help induce labor. It also stimulates the release of milk from the mammary glands for nursing.
Define anterior pituitary gland
Produces specific hormones that control thyroid, adrenal cortex, and gonads as a result of the hypothalamus producing hormones that travel to, and stimulate the anterior pituitary gland.
Do the hormones produced in the thyroid, adrenal cortex, and gonads utilize a positive or negative feedback mechanism?
They utilize a negative feedback mechanism.
What 7 hormones does the anterior pituitary secrete?
- Growth hormone (GH)
- Melanocyte stimulating hormone (MSH)
- Thyroid stimulating hormone (TSH)
- Adrenocorticotropic hormone (ACTH)
- Follicle stimulating hormone (FSH)
- Luteinizing hormone (LH)
- Prolactin
Identify the following hormones released by the anterior and posterior pituitary, as well as figures 1, 10, and 11 (refer to figure 6.6 Hormones released by the anterior and posterior pituitary).
- Anterior pituitary
- TSH
- ACTH
- FSH / LH
- PRL
- MSH
- hGH
- OXT
- ADH
- Posterior pituitary
- Hypothalamus
Define GH
Growth hormone or somatotropic hormone. Dramatically affects physical appearance. The amount of this hormone determines the height and bone structure of a person. It causes cell growth, division and protein synthesis. It impacts changes on skeletal muscles, liver, and bones. In bones, it promotes growth of the cartilaginous plates and causes osteoblasts to form new bone,
What happens if there is too little GH produced in childhood?
The individual becomes a “pituitary dwarf” because the pituitary gland does not secrete enough growth hormone.
What is a “pituitary giant”?
When the pituitary gland produces too much growth hormone (GH).
Define acromegaly
This is a condition where an adult overproduces growth hormone (GH), resulting in the feet, hands, and face (particularly, chin, nose, and eyebrow ridges) to become overly large.
Define prolactin (PRL)
Prolactin (PRL) is a hormone produced in quantity only during pregnancy and childbirth/nursing. It causes the mammary glands in the breasts to develop and produce milk. It also plays a role in carbohydrate and fat metabolism.
What is Melanocyte-stimulating hormone (MSH)?
MSH stimulates melanocytes to increase their synthesis of melanin, which is a dark pigment that is released when exposed to sun.
Define Thyroid-stimulating hormone (TSH)
TSH stimulates the thyroid gland to produce T3 and T4.
What part of the pituitary produces TSH?
The anterior pituitary produces TSH.
Does TSH stimulate the thyroid to secrete thyroxin (T4) via positive or negative feedback?
Negative.
What are the 2 main hormones produced by the thyroid?
T3
T4
Describe a goiter and what causes goiters
A goiter is an enlarged thyroid gland. Goiters are a result of a lack of iodine (typically found in T3 and T4) in the blood. When there is a low level of thyroxin in the blood, the anterior pituitary continues to produce TSH, causing the thyroid to respond (by increasing in size, producing a goiter). The size increase is ineffective, as thyroxin cannot be produced without iodine.
Define congenital hypothyroidism
congenital hypothyroidism is a term for low thyroid function since birth. People with congenital hypothyroidism show reduces skeletal growth, sexual immaturity, and an abnormal protein metabolism which can lead to intellectual disability.
Define calcitonin
Hormone produced by thyroid that lowers the level of calcium in the blood and deposits calcium into bone. It also opposes the action of parathyroid hormone (PTH) produced by the parathyroid glands.
What are the parathyroid glands?
There are 4 parathyroid glands. They are embedded into the surface of the thyroid gland. They produce parathyroid hormone (PTH).
What is parathyroid hormone (PTH)?
Under the influence of PTH, the calcium level in the blood increases and the phosphate level decreases. PTH stimulates the increased absorption of calcium from the intestines. It also retains calcium through excreting phosphate at the kidneys. In bones, PTH promotes the activity of osteoclasts to demineralize the bone, increasing the amount of calcium in the blood. When blood calcium levels reach the appropriate range, the parathyroid glands stop producing it through negative feedback,
Define tetany and what causes it
Tetany is when the body shakes and cramps from continuous muscle contraction. Tetany is a result of not enough PTH being produced in response to low blood calcium levels and an electrolyte imbalance.
Basically, low blood calcium causes increased excitability of the nerves, which fire spontaneously and without rest.
What is the hypothalamus?
It is the portion of the brain that regulates the internal environment and homeostasis.
What are some things the hypothalamus helps to regulate?
Heart rate
Body temperature
Water balance
Glandular secretions of the pituitary gland.
Where is the pituitary located?
Just below the hypothalamus.
What are the 2 portions of the pituitary?
- Posterior pituitary
2. Anterior pituitary
What does the functional and structural relationship between the hypothalamus and the posterior pituitary illustrate?
The overlap between the nervous and endocrine systems.
How is the posterior pituitary connected to the hypothalamus?
By means of a stalk-like structure.
What are neurosecretory cells and where can they be found?
Neurosecretory cells are neurons in the hypothalamus and they respond to neurotransmitters and produce hormones that are stored in and released from the posterior pituitary.
How do the hormones produced by neurosecretory cells terminate in the posterior pituitary?
Through axons.
What 2 major hormones are stored in the axon endings in the posterior pituitary?
- Antidiuretic hormone (ADH)
2. Oxytocin
What glands does the hypothalamus control the release of hormones from?
- Posterior pituitary
2. Anterior pituitary
Define Adrenocorticotropic hormone (ACTH)
This hormone stimulates the adrenal cortex to produce cortisol.
Name 2 gonadotropic hormones
- Follicle stimulating hormone (FSH)
2. Luteinizing hormone (LH)
What are gonadotropic hormones responsible for?
Stimulating the gonads (the testes in males and ovaries in females).
Where are the adrenal glands located?
They lie atop the corresponding kidney (left adrenal over left kidney, right adrenal over right kidney).
What are the 2 portions of the adrenal glands?
- Medulla
2. Cortex
Is the medulla located on the inner or outer portion of the adrenal glands?
Inner portion
Is the cortex of the adrenal glands located on the inner or outer portion?
Outer portion
What 2 hormones does the adrenal medulla secrete?
- Epinephrine
2. Norepinephrine
What 2 hormones are associated with the “flight-or-fight” reaction?
- Epinephrine
2. Norepinephrine
When and where does the adrenal medulla secrete epinephrine and norepinephrine?
When: under conditions of stress.
Where: Directly into the bloodstream.
What is the “flight-or-fight” reaction responsible for?
Increase in blood glucose level
metabolic rate increase
breathing and heart rate increases
Constricting the blood vessels in the intestine, dilating the muscles.
What does the constricting of the blood vessels in the intestine and the dilating of the muscles during a “flight-or-fight” response result in?
Increased circulation to the muscles that causes them to have more stamina than usual.
What can epinephrine be used for in a medical setting?
It can be used as an emergency drug to stimulate the body in patients in cardiac arrest.
What part of the adrenal gland is essential to sustain life?
The adrenal cortex. The medulla can be removed.
What 2 main classes of hormones are made by the adrenal cortex?
- Glucocorticoids
2. Mineralocorticoids
What other hormones are secreted by the adrenal cortex in small amounts?
Small amount of male sex hormones and even smaller amount of female sex hormones. (if you are female it helps secrete smalls amounts of male sex hormones and in males it releases small amounts of female hormones).
Of the various glucocorticoids. what hormone is responsible for the greatest amount of activity?
Cortisol
What does cortisol do?
Promotes the hydrolysis of muscle protein to amino acids that enter the blood.
In a medical setting, what can the administration of cortisol do?
reduce inflammation
What is the most significant secretion of mineralocorticoids?
Aldosterone
What is the secretion of aldosterone responsible for?
Regulating the level of sodium ions and potassium ions in the blood.
What is aldosterone’s target organ?
The kidneys.
What does aldosterone do when it reaches the kidneys and why is it important?
Promotes renal absorption of sodium and renal excretion of potassium. This is important to the maintenance of blood pressure.
What does “water follows salt” mean?
It means that when sodium is absorbed into the blood the water will follow, increasing our blood volume, thus, increasing blood pressure.
Which gland produces melatonin?
The pineal gland.
Where is the pineal gland located?
In the brain.
What causes jet lag?
Melatonin. When you travel internationally, your body still produces melatonin according to the body’s “old” schedule.
Identify the the two parts of the brain and the gland shown in this image (refer to figure 6.7 posterior view of brain and X gland), then, explain what one hormone this gland is responsible for producing is.
- Cerebrum
- pineal gland
- cerebellum
- The pineal gland produces melatonin.
What two types of tissue is the pancreas composed of?
- exocrine tissue
2. endocrine tissue
What does exocrine tissue produce?
It produces and secretes digestive juices.
What is the endocrine tissue of the pancreas called?
The pancreatic islets (of Langerhans).
What 2 hormones do the pancreatic islets produce and secrete?
- Insulin
2. Glucagon
Identify structures 1, 7, 9, 10 (refer to Figure 6.8 pancreas located between stomach and small intestine).
- Liver
- Pancreatic duct
- hepatopancreatic ampulla
- Pancreas
What is glucose used for in the body?
Energy
What hormone is secreted by the pancreas when there is a high blood glucose level (usually occurring just after eating)?
Insulin
What are the 3 actions of glucose?
- Stimulates liver, fat, and muscle cells to take up and metabolize glucose
- Stimulates liver and muscles to store glucose as glycogen
- Promotes the buildup of fats and proteins and inhibits their use as an energy source.
Explain what insulin and glucagon do in the body?
Insulin is used for the storage of nutrients- reducing the level of glucose in the blood, while glucagon is used for the breakdown of stored nutrients and increases the glucose in the blood to rise.
Identify steps taking place in 1 and 5, and identify structures 8, 9, 10.
- Alpha cells are releasing glucagon
- Beta cells release insulin
- Pancreas
- Liver
- Adipose tissue
Identify steps taking place in 1 and 5, and identify structures 8, 9, 10.
- Alpha cells are releasing glucagon
- Beta cells release insulin
- Pancreas
- Liver
- Adipose tissue
What hormone is related to anemia?
Erythropoietin
What function does erythropoietin play in the body?
It acts on bones marrow to cause an increased release of red blood cells into the bloodstream.
What can happen without erythropoietin?
A person’s red blood cell count can fall, causing anemia.
What is a common condition for patient’s with kidney disease? Why?
Anemia, because the kidneys produce erythropoietin, which increases their red blood cell count.
Identify structures 1, 2, 3 in Figure 6.10 Cross section through the kidney.
- Segmental artery
- Renal artery
- Renal vein
What are the gonads in males and females?
Gonads in males are the testes, gonads in females are the ovaries
Where are the testes located?
Scrotum
Where are the ovaries located?
In the abdominal cavity
What do the testes produce?
Androgens (testosterone)
What 2 hormones do the ovaries produce?
- Estrogen
2. Progesterone
How do the hypothalamus and the pituitary gland control the hormonal secretions of the testes and ovaries?
Through FSH (Follicle stimulating hormone) and LH (Luteinizing hormone).
What is structure 1 and 2 in Figure 6.11?
- Testes
2. Ovaries
List some functions of testosterone?
- Essential for normal development and functioning of sex organs in males
- Maturation of sperm
- During puberty, it stimulates growth of penis and testes
- Brings about and maintains secondary sex characteristics.
List some secondary sex characteristics testosterone brings about and maintains?
growth of a beard and body hair, pubic hair
prompts larynx and vocal cords to enlarge (deepening the voice)
muscular strength in males
secretion of oil and sweat glands (responsible for acne and body odor)
sex drive
What 2 hormones regulate the sex hormones?
- FSH (follicle stimulating hormone)
2. LH (Luteinizing hormone)
What type of hormones are FSH and LH?
Gonadotropic hormones
What 2 things does FSH do in the ovary?
- The development of a follicle on the ovary to mature before ovulation.
- Increases estrogen production
What 2 things does LH do in the ovary?
- Causes ovulation to occur.
2. Causes progesterone release to facilitate potential fertilization of the egg and pregnancy.
What is the key hormone for the maintenance of pregnancy?
Progesterone
What is estrogen responsible for at the time of puberty?
Growth of the uterus and vagina
What is estrogen necessary for?
Egg maturation in the ovary
What secondary sex characteristics is estrogen responsible for in females?
body hair
fat distribution
enlarging the pelvic girdle and cavity
What are estrogen and progesterone both required for?
Breast development and regulation of the uterine cycle.
Do females and males both produce all of the sex hormones?
Yes, but in different ratios.
What gland is responsible for producing the “opposite” hormones that the gonads of a specific individual do not?
The adrenal gland
Identify the organ and gland in Figure 6.12 Covered
- Thymus
2. Heart
Where does the pineal gland receives nerve impulses from?
The optic tract of the eyes.
