The Essay On The Cardiovascular System: The Blood.

Understanding Elevation Changes and Hemostasis

1. Have you ever changed elevation from a lower elevation to a higher elevation, or vice versa? How did that change make your body feel? If you went to a higher elevation, did you notice anything similar to what John noticed (Critical thinking section on page 575)? Why might athletes train at a higher elevation before running a marathon?

Elevation changes affect the overall heart rate and also affect the breathing rate [1]. In higher elevations, a significant increase in an individual's heart rate can be observed. Similarly, low elevation can lead to a decrease in heart rate. In the present case, it has been seen that John has effectively trained himself to sustain at the "high altitude of Denver" where the partial pressure of oxygen is low in the atmosphere and this can lead to effective homeostasis disruption. After some time, this disruption of homeostasis leads to "polycythemia" (a condition of blood doping where the storage of erythrocytes increases and then restores to a normal level). The physical training has helped John's body and it can effectively restore the "blood dropping" to a normal level. Athletes effectively train their body at "higher elevation" to prepare their body so that during a marathon they would not face any "shortness of breathing" or sudden shock [2].

Erythrocyte is responsible for delivering oxygen into tissues via carrying it in blood. The mechanism that is employed by the erythrocytes cells for carrying oxygen is as follows.

While running at a high altitude, new stress is faced by John's body due to decreased oxygen levels in the air. This in turn effectively reduces the overall oxygen level in tissues and disrupts homeostasis. This disruption is effectively managed by John's kidneys as it responds to the disruption.

Change in Hematocrit can be observed when an individual lives at high altitudes for some period of time. This occurs due to polycythemia which is a condition of blood doping where the stored erythrocytes get removed from an individual's body [3].

2. Explain the proposed role of hemoglobin in the maintenance of blood pressure.

Blood pressure and effective blood flow regulation are maintained by haemoglobin [4]. Endothelial cells are present in the linings of blood vessels and these cells produce Nitric oxide which is a gaseous hormone and this hormone binds with haemoglobin. Haemoglobin releases nitric oxides under specific circumstances. Effective vasodilation is caused by the released NO, which is an increase in the diameters of blood vessels.

Describe the events of hemostasis from the injury to the vessel until just before the clot is formed.

Hemostasis is an effective sequential response that "stops bleeding". This quick response generates when damage occurs to the blood vessels. It quickly localizes the damaged region and controls the damage in order. The mechanism of reducing the blood loss is done by three mechanisms which are "Vascular Spasm '', "Platelet plug formation" and "Coagulation of blood clotting" [5].

Vascular Spasm: This occurs right after the vessel injury (immediate response)

The contraction of smooth muscles in the walls occurs immediately after arterial damage and this is known as a "vascular spasm". The vascular spasm reduces the overall blood loss from "several minutes" to "several hours”.

The Role of Hemoglobin in Blood Pressure Maintenance

Platelet plug: this is another effective method for preventing blood loss in which accumulation of a large mass of platelets occurs at the injury site. This is effective when the blood loss has occurred due to small holes in blood vessels.

The chemicals that are present in the vesicles of cytoplasmic granules are,

 Dense granules: This contains “ADP”, “Ca++” and “serotonin.

Alpha granules: This contains different clotting factors and "Platelet-derived growth factors or PDGF". PDGF is a protein that is responsible for the effective proliferation of the fibres of vascular smooth muscles.

The platelet plug formation occurs in three different steps

1. Platelet adhesion: At the initial stages, the platelets effectively contact and effectively sticks in the parts of the blood vessels that have been damaged. When the endothelial linings are disrupted, the collagen fibres present in the blood vessels get exposed [6].
2. Platelet activation: Platelets are activated due to the effective adhesion and presence of the Thrombin. During this activation, the shapes of the platelets change and these platelets are effectively spread into different projections. This allows the platelets to interact with each other and after that, the platelets effectively liberate their vesicle contents and different other substances that have been effectively synthesized by the platelets in a reaction known as the "platelet release reaction". The nearby platelets are activated by the "Liberated ADP" and "Thromboxane A2". This effectively cause and properly sustains the vascular smooth muscle contraction by functioning as "vasoconstrictors".
3. Platelet aggregation: The ADP that is released provides stickiness to the platelets of the surrounding area and this helps in adherence of the "newly recruited and activated platelets" to the "originally activated platelets"; this platelet gathering is also known as "platelet aggregation".
4. Blood Clotting: Effective formation of the fibrin threads in the injured area

In the blood vessels, the blood remains in a liquid form however this blood thickens and forms a gel after it releases from the body which eventually separates from the "liquid" and the "serum". The formation of the gel is known as clotting and the formation of fibrin threads is known as Coagulation [7].

3. Have you ever had a wound become infected? What kind of wound was it? What other kinds of wounds do you think might be easily infected? What methods might you use to protect yourself if your skin barrier is damaged?

My wounds become infected due to many reasons when I was young,

Skin cannot protect against the infection when the wounded skin is open as the infection becomes more prone to enter the skin. The body's immune system is effective in fighting against the infection and the main role in killing the "foreign particles" is played by the "leukocytes" or the "White blood cells". Infection occurs for a longer period on the condition that the immune system of the body is weak and in less or low immunity, the body wounds tend to get easily infected. One can protect himself from infection by covering the wounded area, cleaning the affected area regularly and having proper antibiotics to get more immunity [8].

4. Contrast the two types of defense mechanisms. Give examples of each.

First Line of Defense

The external "physical" and "chemical" barriers of the body are the first line of defence against pathogens. Skin acts as an effective physical barrier that protects the body by preventing the microbes and different foreign substances from penetrating and entering the body. There are two different layers of skin and these are the "Outer Epidermis" and "Epidermis". The epidermis consists of epithelial cells which are keratinocytes and contain keratin which is a "tough" and "fibrous protein". This helps in protecting the skin and its "underlying tissues" against excessive heat, microorganisms and different chemicals. The "outer epidermis" layer contains dead keratinocytes and the periodic shedding help in effective microbe removal from the surface of the skin.

The second line of defence

The second line of defence occurs when the pathogen crosses the physical and chemical barriers of the first line of defence. The second line of defense includes "antimicrobial substances", "natural killer cells", "and phagocytes", "anti-inflammation" and effective "fever".

Antimicrobial substances: There are four different types of "antimicrobial substances" that reduce microbial growth. These are "interferon", "complement", 'iron-binding proteins", and "antimicrobial proteins". Interferons or IFNs are the proteins that have been produced from cells that have been infected with viruses and after releasing from the "virus-infected cells", the IFN effectively diffuses to the uninfected cells and synthesizes effectively "antiviral proteins" that interferes with the effective viral replication. "Natural Killer cells" and "cytotoxic T cells" are activated by IFN and this inhibits "Infected and oncogenic cells". Moreover, IFN restricts cell division and causes tumour suppression. There are three types of IFN such as "alpha", "beta" and "gamma" [9].

Describing the Process of Hemostasis

5. Describe the process that results in an activated B-cell.

Specific antigens are inactivated by the use of “antibodies” from antibody-mediated immunity

The human body has millions of B cells and T cells and each B cell can effectively respond to specific antigens. B cells also undergo clonal selection and segregate to antibodies that reach the invasion site after circulating from lymph and blood [10].

Antigen processing B cell

When the antigens are taken into the B cell it is broken into different peptide fragments and is combined with the MHC self-antigens after that it moves to the plasma membrane. The T cells effectively recognize the class II MHC cells and after that the B cell activation, proliferation and differentiation occur through co-stimulation by T cells [11]. The activated B cells undergo specific clonal selection. The plasma cells produce millions of antibodies after contacting an antigen for four to five days. Memory B cells ensure that the same antigen does not reappear in future by entering the plasma cells.

6. Have you ever gone swimming and held your breath to go underwater? How long were you able to hold your breath? How did it feel near the end, before you let go? Try holding your breath now. Why couldn’t you hold it for longer?

I have held my breath underwater while swimming. I have been able to hold my breath for about one to two minutes before I let it go. Near the end, it felt "disoriented" and "inebriated". At first, I felt relaxed while holding my breath. This is known as the "diving reflex" as the heart rate and metabolism rate of the diver's body slow down underwater.

The situation is different out of the water. I can hold my breath for 30 seconds to 1 minute out of water. This occurs as out of the water the air pressure restricts the body from holding breath for too long. On the other hand, the water pressure underwater is higher than the air pressure. However, as the metabolism rate and heart rate do not slow down on land, individuals feel more pressure on them and this limits their ability to hold their breath [12]. I cannot hold my breath any longer on land due to this reason.

7. Define ventilation, inspiration, and expiration, and describe how lung volume affects pressure and therefore air movement.

 Ventilation: Breathing is the first and most effective step in respiration and this helps the body in "effective O2 supply" and CO2 removal [13]. The process of ventilation is defined as the "in and out" of effective airflow from the lungs. Inspiration is the inflow of air which is done by inhalation and expiration is the outflow of air which allows CO2 outflow through exhalation.

Inspiration: Here the alveolar pressure is less than the atmospheric pressure which is gained through effective lung volume increase which requires muscular contractions of diaphragms and intercostal.

Expiration: Here the alveolar pressure is higher than the atmospheric pressure and muscular relaxation occurs.

The Immune System

Pulmonary circulations define the "high blood flow" as the cardiac output received by the lungs. However, as the diameter of blood vessels is larger there is less resistance, thinner walls and low blood pressure.

8. PO2 is a primary factor influencing the degree of hemoglobin saturation. Explain how PO2 in the lungs and tissue cells determines whether oxygen binding or dissociation occurs with hemoglobin.

As the PO2 increases its combination rate with haemoglobin also increases and a sigmoidal curve can be observed. This describes that after O2 binding a specific conformational change can be observed in haemoglobin due to "cooperative-O2 binding" and this conformational change enhances the affinity of haemoglobin for oxygen. The O2-transportation via blood is done by haemoglobin and the O2 effectively binds with the haemoglobin molecule which consists of one globin protein (this contains four polypeptide chains and among them, two are alpha and two are beta chains) and one heme protein (red pigment) which bounds to the polypeptide chains. Oxyhemoglobin produces with the reaction of O2 and Hb ((Hb+O2=HbO2 - O2) and deoxyhemoglobin produces when low oxygen is present (CO2+Hb=HbCO2- CO2) HCO3). PO2 is the determining factor for Hb-O2 binding.

Dissociation curve for O2-Hb-

On the condition that high PO2 is present, saturation occurs as a large volume of O2 binds with Hb and in presence of low PO2 partial saturation occurs. O2 molecules continue to bind with Hb molecules until saturation during high PO2 and in low PO2, less O2 holding is done by haemoglobin. A "full load O2" is effectively picked by blood from the lungs [14].

9. Do you drink coffee? Have you ever noticed a change in your need to urinate while drinking coffee? Have you ever felt dehydrated after drinking a large amount of coffee?

Yes, I drink coffee. I feel that after drinking coffee my urge to urinate becomes more frequent. Coffee and caffeine have a specific "diuretic effect". It has been observed that consumption of "250mg to 300mg" caffeine consumption can trigger the "diuretic effect" in the body. This explains that caffeine increases the amount of fluid loss from the body. Consumption of a high amount of caffeine often causes dehydration and creates a feeling of "thirst" [15]. Again, the feeling of dehydration and thrust occurs due to the inhibition of the ADH hormone. This hormone is responsible for stimulating the aquaporins which again act for "H2O reabsorption" in kidneys and keeps the body hydrated. Inhibition of ADH hormone production results in increased dehydration and thrust.

10. Two autoregulatory mechanisms maintain normal GFR. Describe how each of them can increase or decrease GFR.

GFR is the per-minute formation of filtrate in each renal capsule and this is known as the “Homeostasis of body fluids” and this effectively determines the total “net filtration pressure” with a little increase of GFR [16]. The regulation of GFR is done in two different ways such as “adjustments of blood inflow and outflow from glomerulus” and “alerting of glomerular capillary surface area for effective filtration”.

Protecting Wounds from Infection

11. Describe reabsorption via sodium-potassium pump activity along the collecting duct. Include hormonal influences in your description.

Reabsorption: This is known as the "effective return of filtered H2O and solutes" to the bloodstream which is done by "nephron and collecting duct". Two types of cells can be seen are the "principal cells" such as reabsorbed sodium ions and secreted potassium ions which have aldosterone and ADH (Antidiuretic hormone) receptors and the "intercalated cells" which are the reabsorbed carbonated ion and secreted hydrogen ions.

Sodium-Potassium pump: N+ leaked channels are seen in earlier nephron segments. As the Na+/K+ undergoes active transport of sodium ions across the "basolateral membranes'' the overall concentration of the sodium ion remains low. The sodium ions undergo passive diffusion from the interstitial spaces into the peritubular capillaries. The transcellular reabsorption and paracellular reabsorption of the potassium ions occur in the "proximal tubule" and "Henle's loop". The effective dietary potassium ion intake helps in maintaining the level of potassium ions in body fluid. A different type of K+ ions are also secreted by the "principal cells'' and this keeps a high potassium ion concentration in the sodium/potassium pump.

Hormonal effect on “H2O, Na+, Ca++ reabsorption and K+ secretion

ADH or “antidiuretic hormone” which is released by the “Posterior pituitary gland”, regulates the effective reabsorption of H2O permeability for the P cells. The insertion of the “aquaporin-2-containing vesicles'' under the stimulation of ADH hormone in the “apical membrane” effectively results in the enhancement of blood volume and blood pressure. On the condition that effective reduction of ADH level can be seen, adequate removal of the “aquaporin-2” channels from the “apical membrane” occurs via endocytosis. This decreases the overall H2O permeability by the principal cells. The ADH regulation for the “facultative water reabsorption” involves an effective “Negative feedback system”. When the concentration of H2O declines, by 1%, the osmotic pressure of “plasma fluid” and intestinal fluids' ' increases and this can be detected by the hypothalamus.

12. What fluid do you most frequently ingest? What other things are in that beverage that might change your balance of energy and electrolytes? Does Figure 20.2 make you want to change the beverage you drink most frequently?

The most frequently ingested fluid by me is coffee which is a “diuretic drug”. The main element of coffee is caffeine which is responsible for causing excessive diuretic effects in the body. Excess consumption of caffeine creates “urinary incontinence’ and might lead to excess fluid loss from the body [17].

Figure 1: Water and electrolyte balance in the body

(Source: Learning materials)

The above figure demonstrates the need for perfect electrolyte balance in the body. According to the figure, the amount of water that is being consumed should be equal to the total amount of fluids that are lost from the body due to excess sweat, dehydration and other effects. This figure has influenced me to change my beverage to a substance that has more electrolyte balance to support my body. 

13. How thoroughly do you chew your food before swallowing it? What is the purpose of chewing your food? Do you think it is better to chew it more thoroughly or less thoroughly?

Contrasting the Two Types of Defense Mechanisms

I chew my foods approximately 30 to 32 times before effectively swallowing that food. Proper chewing of food before swallowing helps in better digestion and also helps in preventing "overeating".

I think foods should be chewed “more thoroughly” to avoid indigestion and other complexities. “Through Chewing” also helps in getting all the benefits from the food.

14. Detail the three functions of the enterogastric reflex and segmentation and its effect.

The enterogastric reflex is effectively triggered in the duodenum through the presence of “baroreceptors” and “chemoreceptors''. This occurs due to the entry of chymes and the effective change in pH in the duodenum [18].

1. Enterogastric reflex helps in preventing the entry of high amounts of chyme into the duodenum.
2. This effectively inhibits the total amount of gastric acid inflow. This way it also reduces the cellular erosion of intestinal cells.
3. This reflex increases the time duration for the effective “chyme digestion”. This occurs before its effective movement towards the “small intestine”.

The main effects of “enterogastric effects and segmentations” are inhibition of the production of gastrin, reduction of overall stomach contractions, and enhancement of the overall contractions of “pyloric sphincter”

15. Describe the following as they pertain to the functions of bile and bicarbonate:

a) source (organ)

The pancreas is the effective source organ for the production of "bile" and "bicarbonate".

b) molecular structure

The "Bile acids or BAs" are effective amphipathic molecules containing "24 carbon atoms". The nucleus of this molecule has a "rigid structure" and the nucleus is hydrophobic. An acidic side chain is also attached to the structure which is an aliphatic side chain and is flexible [19].

c) primary function

The primary function of bile is to effectively “carry waste” and it also helps in fat digestion.

d) emulsification need

Bile salts have an effective “detergent property” which helps in fat digestion. The large fat globules are broken apart or effectively emulsified by bile salts.

e) intestinal protection

Bicarbonate helps in the effective neutralization of the stomach acid and retains the balance of acids and alkali.

f) intestinal enzymes

The effective formation of bicarbonate is done by the enzyme “carbonic anhydrase” which facilitates the production of bicarbonate from carbon dioxide and water.

16. How do you feel when you are in the absorptive state? How do you feel when you are in the postabsorptive state? How can you be sure that you are in the postabsorptive state?

The absorptive state is an effective stage where specific absorbed nutrients are effectively catabolized to serve the body's needs.  During this stage, I feel "fed or full" as the digestion starts during this stage. 

Figure 2: Absorptive stage

(Source:  Learning materials)

The post-absorptive stage is also known as the "fasting stage" [20]. Here the food digestion is effectively completed and I feel hungry again. I can understand that I am in a postabsorptive stage of the feeling of hunger.

17. What do you know about breast cancer? Look at Figure 23.8(d) and identify which structures/tissues you think most commonly become cancerous in the breast to lead to breast cancer.

Breast cancer is a type of cancer were some of the breast cells start growing very abnormally and the cell division rate of these cells surpasses the division rate of healthy breast cells [21].  

Figure 3: Breast cancer diagram

(Source:  Learning materials)

According to the above figure, the tissues of the right side structure have the most risk of breast cancer. This is because significant tissue inflammation can be seen for which the milk ducts cannot be visualized clearly.

18. Describe the following as they pertain to hormonal control of male reproductive functions:

a) gonadotropin-releasing hormone (GnRH) production

The GnRH hormone effectively stimulates the overall production of “luteinizing hormone” and “follicle-stimulating hormone” which again stimulates the production of testosterone.

b) effect of luteinizing hormone (LH) on the testes

The LH hormone stimulates testes in testosterone production which stimulates the production of sperms.

c) effect of testosterone and follicle-stimulating hormone (FSH) on the testes

FSH hormone triggers the growth of testicles and stimulates Sertoli cells in producing "androgen binding proteins' which is an effective component of "testicular tubule".

d) androgen-binding protein (ABP)

ABP stores androgens inside the “seminiferous tubule” and these efficient “steroid hormones” are used for the production of “spermatocytes” and “spermatids” [22].

19. Describe the positive feedback loop that results in childbirth.

During childbirth, the uterine contractions stimulate the oxytocin release which helps in stimulating the “muscular contraction” [23]. This muscular contraction causes the baby to effectively pass through the “birth canal”. 

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