Endocrine System

Question 1

Describe the difference between hormones and neurotransmitters.

Answer 1

Hormones are chemicals secreted from endocrine glands/organs that either enter a local tissue or travel the blood stream to attach to a target tissue. An example of a local hormone (paracrine hormone) is insulin; it is released from the pancreas and enters the duodenum.
A neurotransmitter is a chemical released from nerve cells (specifically neurons) that send signals between nerve cells via a “junction” known as a synaptic cleft (most important for this answer, is that hormones can travel through the vascular system while neurotransmitters travel only through nerve cells).

Question 2

How does the endocrine system differ from the nervous system?

Answer 2

1. The means of communication: nervous system relies on electrical and chemical methods; endocrine system relies only on chemical methods
2. Speed: the nervous system responds (activation and cessation) much faster than the endocrine system.
3. Adaptation to long-term stimuli: nervous system is more short-term (responds quickly and declines) while the endocrine system has a longer more persistent response.
4. Target cell/tissue: nervous system target is specific and precise; the endocrine system could have a more general effect (widespread to many organs).

Question 3

Where is the pituitary gland located and what are its functions?

Answer 3

The pituitary gland is located in the brain encased in the sella turcica of the sphenoid bone. It is suspended from the hypothalamus; from which it receives signals to secrete hormones.
Specifically, it secretes growth hormones (follicle stimulating hormone, leutinizing hormone, thyroid stimulating hormone, and corticotropin hormone) from the anterior lobe and antidiuretic hormone from the posterior lobe.
NOTE: be knowledgable in the target tissue and function of the above hormones.

Question 4

The thymus is located mediastinum just superior to the heart. What are its functions?

Answer 4

The thymus secretes important hormones needed for fighting pathogens. Specifically, these hormones regulate maturation and activation of T-lymphocytes. NOTE: be knowledgable in the target tissue and function of the above hormone.

Question 5

Describe the difference between the thyroid gland and parathyroid gland. Focus on the location (description) and hormone secreted.

Answer 5

• The thyroid gland has the highest rate of blood flow of all the endocrine glands. It is located on the lateral sides of the trachea connected by the isthmus. It secretes T3, T4, thyroid hormone, and calcitonin.
• The parathyroid glands are small nodules located on the thyroid gland. It is responsible for secreting PTH to regulate blood calcium levels. It is also responsible for promoting calcitriol synthesis. NOTE: be knowledgable in the target tissue and function of the above hormones.

Question 6

Other than insulin, what other hormones is the pancreas responsible for secreting?

Answer 6

The pancreas secretes glucagon (to stimulate glucogenolysis, fat catabolism, and absorption of amino acids); hyperglycemic hormones (to raise blood glucose); and hypoglycemic hormones (to lower blood glucose).

Question 7

How are the effects of hormones regulated (i.e., how are hormones received by target tissues and how are they “turned off”?

Answer 7

Hormone receptors are located on the target tissue. These receptors are specific to the hormone(s) needed for that tissue. The receptors have the ability to either receive the hormone for the desired effect OR reject the hormone so it may be “shut off” and the effects of the hormone cease.
Once a hormone signal is “turned off” or is not used, it is filtered by the liver and kidneys; it is then excreted as bile or urine.

Question 8

The body has the ability to adapt to stress. What are the stages?

Answer 8

1. The alarm stage - the body prepares a reaction by increasing metabolism, heart rate, and respiratory rate.
2. Resistance - the bodies natural energy stores become depleted causing gluconeogenesis and depressed immune functions.
3. Exhaustion - the body begins using protein as energy source, causing hypertrophy. Hypertension and electrolyte imbalances occur leading to pH imbalances, resulting in death.

Question 9

Describe the etiology of both Type I and Type II diabetes.

Answer 9

Type I diabetes is a result of the body’s inability to produce insulin. Type II diabetes is a result of the body’s or target tissues’s inability to use the insulin the pancreas secretes.