Week 14 (Pre-class Assignment)

Please answer these questions in complete sentences.

1.     If there was one aspect of BIO 160 (class, organization, or content, or something else) you especially enjoyed, what was it?

During this fall semester in BIO 160 my favorite part has been doing the labs in class. I like being able to move around and ask questions to fellow students as well as Joanne. I felt this was a good way to get to know other students and it helped me learn a lot.

2.     If there was something especially challenging (class, organization, or content, or something else), what was it?

Surprisingly, I found Chapter 2 (basic Chemistry) to be the most challenging for me. I also had some trouble with the anatomy of a skeletal muscle fiber, that section was tough!

Thirst Mechanism

Thirst Mechanism is the driving force for water intake. An increase in plasma osmolality of only 2-3% excites the hypothalamic thirst center. Thirst is "the physiological urge to drink water". In studies, it is recognized when subjects report the conscious sensation of a desire to drink. Under normal conditions, most water intake is due not to thirst but to social and cultural factors (eg drinking with meals or at work breaks, water in food). Thirst offers a backup to these behavioral factors and to the ADH response. Both the thirst and the ADH mechanisms are regulated in the hypothalamus. Water intake can be considered to consist of two components: a regulatory component (due to thirst) and a non-regulatory component (all other fluid intake).

The 4 major stimuli to thirst are:

1.Hypertonicity: Cellular dehydration acts via an osmoreceptor mechanism in the hypothalamus

2.Hypovolaemia: Low volume is sensed via the low-pressure baroreceptors in the great veins and right atrium

3.Hypotension: The high-pressure baroreceptors in carotid sinus & aorta provide the sensors for this input

4.Angiotensin II: This is produced consequent to the release of renin by the kidney (eg in response to renal hypotension)

Four layers of the Alimentary Canal (GI) Tract

The four layers of the alimentary canal starting with the innermost layer.

1.     The mucosa is formed by epithelium and a small amount of connective tissue, comes into direct contact with food passing through the canal. It secretes mucus that protects and lubricates the lining.

2.     The submucosa is composed of loose connective tissue, blood vessels, and many nerve endings. The blood vessels carry away the nutrients that are absorbed, and the nerve endings stimulate the muscle fibers so that the food is continually moving by peristalsis.

3.     The muscularis externa consists of a circular band and a longitudinal band of visceral muscles; is the thickest of the four layers. Main function: peristalsis.

4.     The serosa is continuous with the mesentery, the connective tissues that attach to the posterior body wall and hold the digestive organs in their proper position.

Gas Exchange During Respiration

1.) The direction of gas movement is determined by:

DD. Partial pressure differences.

2.) Which of the following statements about partial pressures of gases is true?

BB. PO2 in the lung is greater than PCO2 in the blood; PC02 in the lungs is less than PC02 in the blood.

3.) Which of the following statements about partial pressures of gasses is true?

BB. P_O2 in blood is greater than P_O2 in tissues; P_CO2 in blood is less than P_CO2 in tissues

4.)Oxygen-rich blood is carried through pulmonary arteries from the lungs to the heart

False

5.)Oxygen-poor blood is carried through systemic veins from the body tissues back to the heart.

A.True.

The relationship of the lymphatic vessels to the blood vessels

The lymph begins as a tissue fluid derived from blood capillaries, then enters the lymph capillaries and then travels through the lymphatic vessels and nodes. It then enters the blood steam through veins at the root of the neck. 

Blood vessels carry nutrients, water, oxygen and waste products to and from your body cells. There are three primary types of blood vessels: arteries, capillaries, and veins. The functions include transporting blood away from the heart (arteries), transporting blood toward the heart (veins), and capillaries, which connect the arteries to the veins.

The lymphatic vessels pick up and return excess tissue fluid to the blood vascular system.

The vessels carry lymph from peripheral tissues to the venous system. The lymphatic system transports lymphocytes, is involved in the removal of foreign matter & cell debris by phagocytes & is part of the body's immune system. It also transports fats from the small intestine to the blood.

Components of the lymphatic system:

Lymphatic vessels, Lymph nodes, Spleen, Thymus, Tonsils, Peyer’s Patches, Appendix

Work cited: http://www.lymphedemablog.com/wp-content/uploads/2011/09/Lymphatics.gif

Endorine Gland Stimuli: Hormonal, Humoral and Neural

     Various endocrine glands are stimulated to manufacture and release their hormones by three main types of stimuli -Hormonal, Humoral and Neural. 

Hormonal is the most common it releases hormones in response to hormones produced by other endocrine organs. For example: the hypothalamic secrete hormones that stimulate the anterior pituitary, which stimulate glands to secret hormones (thyroid gland, adrenal cortex and gonads).

Humoral secret hormones in direct response to changing blood levels of ions and nutrients. Declining blood Ca2+ concentration stimulates the parathyroid glands to secrete PTH (parathyroid hormone) PTH causes Ca2+ concentrations to rise and the stimulus is removed. Other hormones releases due to humoral are calcitonin and insulin. 

Neural, in some cases, nerve fibers stimulate hormone release. For example, catecholamine (epinephrine and norepinephrine) is released during times of stress by stimulation of the adrenal medulla by the sympathetic nervous system. Also, the hypothalamus stimulates the release of oxytocin and anti-diuretic hormone by neural stimulation.

Five formed elements and their functions

Five formed elements and their functions

1.     Erythrocytes or red blood cells (RBSs)- The primary function of these cells is to carry oxygen and carbon dioxide to all parts of the body. They deliver oxygen to the tissues and return carbon dioxide rom the tissues to the lungs. They are the most numerous in the blood.  Erythrocytes do not need a nucleus to carry out the function of the transport of oxygen and carbon dioxide.

2.     Leukocytes or white blood cells (WBCs)-White blood cells provide protection against foreign organisms and matter. They circulate throughout the body and tissues. To carry out their function the white blood cell must be highly mobile. They are confined to the blood stream and slip in and out of blood vessels.

3.     Platelets also know, as megakaryocytes-Their main function is to form clots to stop bleeding. It also plays a huge role in homeostasis (prevention of blood loss).

4.     Granulocytes: Neutrophils- is phagocytes that are partial to bacteria and fungi, which they destroy when they invade.

      5.   Eosinophils- they increase during infections of parasites.  They gather and release enzymes from their cytoplasmic granules onto the parasite and digest   it away.