Let's get a better understanding of our hormonal system today. The endocrine system discusses the organs and the chemicals they secrete into the blood stream. There they then influence body processes such as growth, glucose absorption, and also reproduction.
Since I decided not to have an anatomy LAB portion, I will also discuss the skin in today's lesson. The skin, or integumentary system is actually your largest organ!
So...as always, please print the lecture notes, watch the videos, answer the questions below, and then email them to me at [email protected] before class to get credit.
And the Lecture Videos:
15.1. The endocrine system deals with one’s hormones. Hormones are chemicals that flow through the blood stream. They attach themselves to body cells (via receptors on their surface) and influence their ‘target’s’ function. Hormones are secreted by glands. Glands also make other substances, such as sweat for example that ’exit’ the body via channels (ducts). What do we call that type of gland?
15.2. The nervous system is a fast acting system that is short lived. Nerve cells send an electrical impulse quickly along a wire. They release a chemical at its end-point (neurotransmitter), which then influences a target cell (make a muscle contract for example). Hormones on the other hand trickle through the blood stream until they find a matching receptor on a cell. They are great for ongoing processes that take time, such as body growth. As the nervous system is fast and quick, the endocrines system is ____ and ____.
15.3. The key to understanding hormones is that the receptor they attach to is what changes the cell’s activity. The hormone is simply a messenger. Hormones come in two different classes (flavors), either water loving or water fearing. Lipophilic (fat loving / water fearing) hormones can easily pass through a cell membrane (an oil film) and attach themselves to receptors inside the cell. Hydrophillic (water loving) hormones cannot pass through the cell membrane. Where do you think their receptors are located?
15.4. Hormones are secreted by many body cells. For example muscle that is not used releases myo-statins, hormones that influence many body functions negatively, increasing the likelihood for diabetes or high blood pressure for example. A muscle that contracts however, releases myo-kines, which are hormones that influence body functions positive, decreasing blood pressure or the likelihood for diabetes. Who knew that muscle tissue also acts as an endocrine gland? This chapter mainly discusses glands however, that exclusively deal with hormone release. Most of their secretions are controlled by the negative feedback system, which is designed to keep many chemicals in the blood (such as glucose or calcium) at a certain range. Chemoreceptors measure specific chemical levels and influence gland secretions accordingly. Where are many of those chemoreceptors locate?
15.5. The pituitary gland is small and sits in the center of the skull, the sella turcica. It has two parts, which together release about eight hormones. The posterior part or lobe has direct neural connections to the hypothalamus, which controls the hypophysis (an old name for pituitary gland). One of the two hormones released from that lobe, the anti-diuretic hormone, or the anti-pee hormone as I call it, controls how much water gets excreted in the urine. What is the other one released by that part of the gland called?
15.6. The anterior lobe of the pituitary gland is linked to the hypothalamus (which controls it) by a small vascular network. The hypothalamus releases so called liberins, molecules that ‘liberate’ or cause the pituitary to release a hormone, or statins, which are chemicals inhibiting it to release one of it’s hormones. Can you name the six hormones released by the adenohypophysis?
15.7. The pineal gland is pine cone shaped, situated in the middle of the brain. It secrets melatonin. What does that this hormone regulate?
15.8. One reason people sometimes have difficulty loosing weight is because of an under-functioning thyroid, a gland in front of our neck. What does the hormone from that gland regulate?
15.9. We have heard before of how important blood calcium levels are. Many vital body functions depend on it. We have two hormones regulating it. Can you name them?
15.10. The adrenals are two glands sitting on top of the kidneys. They consist of a ‘shell’, a surrounding cortex, and a inner medulla. The cortex consists of 3 layers, or ‘zones’ each releasing a different hormone with unique functions. Can you name the 3 different hormones released?
15.11. The inner adrenal medulla secretes a hormone closely related to the ‘fight-or-flight’ response. What is that hormone?
15.12. The pancreas is interesting. It releases lots of digestive enzymes into the first part of the small intestine. Besides that, it also controls blood glucose levels. It secretes a hormone called insulin that attaches to most body cells and let glucose enter from the blood stream. Glucose is then broken down inside the cell to make energy (ATP). Can you name the hormone that can raise blood glucose levels?
15.13. What glands secrete the sex hormones (estrogen & testosterone)?
Please email the answer back to [email protected] before class. Thank you.
And here is the lecture video. Please answer the questions below.
16.1. The skin is the integumentary system’s main organ covering the external surface of our body. On top, many layers of epithelial cells (stratified squamous keratinized epithelium) protect us against dangers coming from the environment. The top layers are ‘dead’ cells that simply fluff off when we bump into something for example. Underneath that is connective tissue anchoring the top layer. Below that is a layer of adipose tissue (a fat layer). Can you name the 3 layers?
16.2. Remember, epithelial tissue is basically rows of cells. It doesn’t have the extracellular component that is part of connective tissue (in bone that is the calcium and fibers holding it together; in blood it’s the plasma). In the skin, the epithelium is stratified, which means it consists of many layers. The bottom layer anchors the epidermis to the underlying tissue. It is very regenerative and constantly produces new cells, which are then pushed upward towards the surface, slowly drying out and accumulating the protein keratin, which makes them hard and waterproof. What are the four main epidermal layers called?
16.3. The main cell type in the epidermis is the keratinocyte. Others concern themselves with transforming touch and pressure into a nerve signal that is sent to the brain. Some are designed to protect us against UV light from the sun. Another cell type again protects us against invaders and are actually resident macrophages. What are the different cell types described called?
16.4. The underlying dermis is connective tissue, which has a few important properties. For once, its extracellular matrix contains fibers, which prevent the skin from tearing. Peg-like projections of the top dermal layer increase the surface area to help anchor the epidermis to the underlying tissue. What is the top dermal layer called?
16.5. We learned from the immune system chapter that the first line of defense is the skin because it creates a boundary keeping ‘bad’ stuff from entering the body. Can you list a few other functions of the integumentary system?
16.6. Have you ever wondered where sweat comes from or what it actually is? Well, it comes from, you guessed right, sweat glands. Can you name the other skin gland type, the one that secretes an oily substance?
16.7. Hair is absolutely cool! When I shaved my head once, I started hitting it all over the place. It was then that I realized hairs protection, because it helped me sense objects before the head hit them. Another great advantage hair provides can be observed in furry animals. When a cat, for example, fears an attack, it’s neck hairs stand up to make it look bigger and more scary. Hair exits the body at an angle. A muscle attached to its shaft and the skin above it can straighten it out when contract. What are those muscles called?
16.8. Nails are another skin appendage that are quite curious. Visualize not having them and skin would cover both ends of a finger. That would make it quite difficult picking up small objects and manipulating them. What tissue type are nails made off?
Please email the answer back to [email protected] before class. Thank you.
No lab for this class.