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.