The Baroreceptor Reflex and the Diving Reflex

Exercise increases heart rate by a process of sympathetic autonomic stimulation. Sympathetic (adrenergic) nerves increase the excitability of the sino-atrial node and reduce the P-R interval .As exercise continues, the physiological changes in the body are continuously monitored by a number of physiological systems and the balance of activity of the sympathetic system (speeding up) and the parasympathetic system (slowing down) is constantly adjusted. When exercise is over, the heart rate does not drop immediately as the body has to undergo a period of re adaption to return to the resting state.

Some of the normal physiological reactions of the body to regulate blood pressure is to modulate the heartbeat of the person and/or adjust the expansion or constriction of the arterial walls and blood vessels to normalize the pressure.

Moreover, Gooden (1994) describes apnea as an essential element to the diving reflex; it ensures not only the prevention of water inhalation, but also acts as an energy-saving device through decreasing nerve stimulation to the diaphragm and intercostals. Therefore, heart rate will be monitored under both experimental conditions and compared to the resting rate and apneic-resting rate. As a profound autonomic phenomenon, further establishment of the diving reflex in humans will shed light on the preservation of the reflex and its role in the survival during ‘near-drowning’ experiences. Only by examining the physiological response in humans can we appreciate the evolutionary significance of this innate neural circuitry.

Epinephrine/adrenaline: Heart rate is increased by the sympathetic nervous system and the hormone adrenaline circulating in the blood via activation of cell surface receptors in

The purpose of arterial pressure and the pulse lab is to determine the effect of posture and exercise on systolic and diastolic pressure and the heart rate. And also in order to find the differences in the reading taken under these condition compares to the baseline reading. The Sphygmomanometer and stethoscope are used to measure the systolic and diastolic blood pressure, counting the beat on the radial artery will give the reading for pulse rate and by using the lab scribe software and IWX214, the blood pressure will be measured. In the heart, the aorta and the carotid arteries have baroreceptors and the chemoreceptors that identify the changes in arterial pressure and the changes in

Vasoconstriction- The sympathetic nervous system on the brain causes the heart rate to increase making your veins constrict. This is called vasoconstriction and the blood flow will be directed right to the muscle to help it work harder. Temperature increases to help the flow of blood around the body. Your reflexes will be quicker and your muscles tense. This facilitates the blood carrying oxygen and removing waste products.

The heart serves an important purpose within the body, pumping blood throughout the circulatory system to supply all parts of the body with vital nutrients and molecules. It pumps oxygen and nutrient rich blood to be exchanged for carbon dioxide, which is then pumped to the lungs and eliminated from the body. The movement of blood throughout the body is due to the heart’s ability to push blood along the circulatory system at a steady, unfaltering rate. This rate, known as heart rate, is regulated and can be altered at a moment’s notice by signaling within the body and heart itself. In vertebrates, the autonomic nervous system controls and regulates heart rate. The autonomic nervous system is divided into two subunits, the sympathetic nervous system and parasympathetic nervous system. The parasympathetic nerve that innervates the heart is the vagus nerve. In this laboratory experiment, the regulation of heart rate was observed by studying a certain breed of turtle, the Red-eared Slider (Trachemys scripta elegans). Both chemical and electric signaling can influence the components of the nervous

Blood pressure in our blood vessels is monitored by the baroreceptors. These receptors send messages to the cardio regulatory center of the medulla oblongata to regulate our blood pressure every minute. In order for blood to be delivered to all organs and tissues, our cardiovascular system must always maintain adequate blood pressure. If the blood pressure drops too low, these organs will not receive an adequate of nourishing blood. Also if the pressure goes too high, the walls of the arteries will stretch and increased activity within the baroreceptor, information will then be sent through the nerves to the cardio regulatory center within the medulla which will responds by initiating the mechanisms that decrease the blood pressure to a normal

Bradycardia is a decrease of heart rate to less than 60 beats per minute (American Heart Association 2016). In humans, the heart rate could slow up to 50%. Peripheral vasoconstriction causes blood flow to reduce by narrowing the blood vessels or increasing resistance (Tandy 2016). Reduction of blood flow allows for the intrinsic oxygen stores to go to oxygen sensitive organs with highest priority like the heart and brain. Blood shift protects the lungs in high pressure such as preventing the lungs from collapsing by moving blood plasma to the blood vessels of the thoracic chest cavity and accumulating there (Breatheology). These three physiological responses work together to conserve oxygen activated by peripheral receptors. Age is also another factor that affects the diving reflex because older adults have increasing heart rate in comparison to children (Panneton 2013). Therefore, the diving reflex works better in

The Sympathetic Cardiac recording measures sympathetic cardiac nerves. The sympathetic nerves innervate the SA and AV nodes which electrical impulses from these nerves increases activity of the nodes to increase heart rate. The Sympathetic Vasoconstrictor is the recording that measures the electrical activity of sympathetic nervous system nerves. The stimulation of these nerves triggers vasoconstriction of systemic arteries while a decrease in electrical activity in these nerves triggers vasodilatation of systemic arteries.

The presence of a dive response in humans when the face is submerged in water was studied. A lot of mammals have shown to exhibit a dive response known as the mammalian dive reflex. During this reflex bradycardia, a slowing of the heart rate, is shown. In this study, human subjects were put through various tests to determine if humans also exhibit bradycardia. Subject's heart rates were measured while breathing normally, while holding breath and while holding breath with face submerged in water. The results showed that there was a significant decrease in heart rate while submerged in water as compared to normal breathing or holding breath out of water. Many other studies have been done that agree with the results found in

The slowing of the heart rate in the subjects while immersed in the cold water provides evidence that follows the theory of the mammalian dive reflex that claims heart rate slows in order to preserve oxygen. Preserving oxygen will divert blood flow and oxygen supply to the lungs, heart, and brain. This will prevent permanent damage such as brain damage.

Vasovagal Syncope, also known as fainting, neurocardiogenic syncope, and neurally mediated syncope, is a very common condition, occurring in roughly half of all people at least once within their life; three percent of the population develops it repeatedly. It is not a serious condition.(2) A vasovagal response involves a decrease in the volume of blood that is returned to the heart, which enervates the baroreceptors(2) in the sympathetic nervous system to increase the force of each contraction of the heart. Consequently, the opposing parasympathetic nervous system is alerted to slow the heart rate and dilate the surrounding veins and arteries. These responses of the nervous system cause the blood pressure to drop very low, causing syncope (loss of consciousness).(1) Most patients are young and healthy, although vasovagal syncope can occur in the elderly population that has preexisting cardiac problems. Extremely hot weather and blood-alcohol levels are typical triggers. Some patients suffer from several, often attacks, while others may only experience them sporadically.(3)

The two divisions of the autonomic nervous system (ANS), sympathetic (SNS) and parasympathetic (PNS), function in a complementary and integrated manner to maintain homeostasis. The output of the autonomic nervous system is quick in comparison to the endocrine system functions. In most cases, these systems have opposite effects, where one initiates a physiological response and the other inhibits. The nerves of this system regulate vital internal functions which are generally performed without conscious control (Khan Academy, 2014).

14. Chemoreceptors can detect changes in oxygen and carbon dioxide levels in the blood, so when there is a change, such as an increase in carbon dioxide, the parasympathetic stimulation of the heart is decreased because the heart needs to work harder. The parasympathetic division is at work when the body is at rest, or to return the body to a state of rest, so in this case, the sympathetic division, not the parasympathetic division, is needed to make the heart work harder to get that oxygen-carbon dioxide imbalance under control.