Week 1 Flashcards
What are some advantages/disadvantages of nervous vs endocrine mechanisms?
Nerves provide very fine control, very precise, and very quick control of body parts (e.g. the tip of the finger). The downside is that the nervous system takes up quite a bit of space and energy. It also cannot control every cell in the body with the nervous system.
The endocrine system is chemically addressed. It sends hormones through the blood and therefore does not take up any space. It is recognized by any tissue that can “read” the hormone. However, while it takes up no space, it is comparatively slow generally speaking.
The endocrine system can also regulate things for extended amounts of time (i.e. decades), such as blood glucose. The nervous system “quickly loses interest”. For instance, when you sit down, you feel the chair, but quickly you forget the sensation of the chair unless you’re actively thinking about it.
Are the nervous system and the endocrine system completely dissociable? Give examples?
No, in many body processes, the endocrine system and the ANS interact with one another. Examples are SNS stimulation of the liver mobilizes glucose which is released through an endocrine mechanism.
What is a hormone?
A hormone is secreted by living cells, in trace amounts, and is transported, usually by the blood, to a distant site within the same organism where it is not used as a source of energy but acts to regulate or initiate reactions and produce an appropriate response.
Why does the definition of a hormone include the term “living cell”?
Because dead or dying cells release “pathological facts” or inflammatory mediators which are important, but are not considered to be hormones.
Compare the amounts expected to be found of plasma glucose vs plasma hormones (e.g. aldosterone)?
Hormones are found in trace amount in the blood. They are hardly comparable to substance like glucose which can be calculated using mmol (10-3), whereas hormones are usually measured in nanomoles (10-9) or picomoles (10-12).
How would a hormone be detected in a lab?
Antibodies raised in animals (e.g. mouse) responsive to the specific hormone would be injected in a tube and mixed with a plasma sample. Another antibody to the same hormone would be inputted, before a last antibody in large amount would be added which would be tagged with fluorescent lighting, which would allow for the detection of the hormone.
How do hormones travel in the blood? How does that affect their ability to diffuse into tissues?
If the hormone is water-soluble, it can travel freely in the blood. However, if it is lipid soluble, hormones are usually bound to binding proteins, through which they can travel. Only free hormones are able to diffuse into tissues, therefore protein-bound hormones are “unavailable” for distribution into tissues.
General Concepts of the Endocrine SystemWhat factors can affect the plasma levels of protein-bound hormones? How does that process occur? Give examples.
Different physiological processes/pathologies can cause a rise/drop in binding proteins which causes a rise in hormones bound to those proteins. Examples like pregnancy increase the number of binding proteins in plasma which causes an increase in protein bound hormones, while liver/kidney failure cause a drop in the amount of binding protein.
Agents that are released from cells to act on neighboring cells are referred to as? Give examples of hormones that have local effects.
Paracrine. Examples of hormones that have local effects as well as systemic effects are prostaglandins.
What makes glucose unable to be considered a hormone?
It is used as a source of energy. Hormones cannot be used in the body as a source of energy. Rather, they must act on receptors to exert their effects.
What is the physiological role of hormones? Give examples?
Either to regulate (stimulate or inhibit) reactions, or to start a physiological and anatomical process. Examples of those are blood glucose regulation through glucagon/insulin secretion by the pancreas, and the hormonal changes which trigger puberty respectively.
Give three different control mechanisms through which the activity of a hormone could be regulated?
- Gland secretion of the hormone
- Number of receptors
- Control of the secondary conversion of the hormone (if applicable)
What would be the effect of continuous receptor stimulation by a hormone? Give an example?
It would cause the downregulation of the receptors responsible for that hormone. An example is that long term high dose use of gonadotrophin (GnRH) is contraceptive because of a loss of sensitivity to GnRH.
What is the role of oxytocin in the scope of pregnancy?
Initiating uterine contraction during labor.
Why does oxytocin only cause uterine contraction at the end of pregnancy?
Because at the end of pregnancy the uterus is dominated by estrogen whereas earlier in gestation, it is dominated by progesterone.
Which hormone is responsible for milk let down in lactation?
Oxytocin
What is the essential role of most hormones? What is the relationship between the trigger which releases the hormone and the action of that hormone? Give examples.
Most hormones are in charge of homeostatic processes. These hormones usually work to work against the factor that triggered their release. For example, insulin secretion is stimulated by high plasma glucose concentration and acts to lower plasma glucose concentration.
What is the role of insulin and what triggers its release?
Insulin secretion is stimulated by high plasma glucose concentration and acts to lower plasma glucose concentration.
What is a diurnal rhythm in the scope of hormones? Give an example of a hormone with a diurnal rhythm?
A diurnal rhythm is a biological rhythm that is synchronized with the day/night cycle. An example of a hormone with a diurnal rhythm is cortisol (peaks at 9am and troughs throughout the evening/night).
Where are the adrenals located?
Suprarenal
What is the drainage of the adrenals?
The left adrenal drains into the left renal vein whereas the right drains directly into the inferior vena cava
What is the blood supply of the adrenals?
Liberal blood supply from; aorta, renal and phrenic arteries
What are the two anatomical zones of the adrenals?
The outer cortex and the inner medulla.
What is the role of the adrenal outer cortex?
Secretes steroid hormones
