The Human Dive Reflex

The Human Dive Reflex INTRODUCTION: The dive reflex is portrayed as bradycardia caused by submerging an individuals head underwater. In diving vertebrates this occurs in a remarkable manner than compared to humans (Hurwitz Furedy 1986). A diving seal where baseline heart rate rises 100 beats to 10 beats per minute when diving would be an example of this (Hurwitz Furedy 1986). Bradycardia is stated as slow resting heart rate or pulse rate (Tortara Derrickson 2009). Accompanied bradycardia response to breath hold is advantageous for vertebrate as well as humans because it permits physiological processes to adjust to environmental change by redistributing blood flow from periphery (non-essential organs) to brain and other essential organs (Hurwitz et al 1986 Gooden 1994 ) The dive reflex depends on the autonomic control of the heart to begin proper responses, the sympathetic nervous system (SNS) sends impulses through the cardiac accelerator nerve and starts release of norephrine which increases contractility and hear t rate. However parasympathetic nervous system (PNS) works through vagus nerves which end in heart decreasing contractility of the heart by decreasing rate of spontaneous depolarization (Tortara Derrickson 2009). Producing bradycardia response requires the sympathetic nervous system and parasympathetic nervous system to work antagonistically (Hurwitz Furedy 1984). Dive reflex consists of two stimuli; the stimulation of facial receptors which are responsive to cold and wetness (pressure receptors), and the voluntary or involuntary termination of breathing or a decrease PO2 (Gooden 1994). Facial stimulus travels through the trigeminal to integrated respiratory centre and cardiovascular centre inside medulla oblongata. Inhibitory neural signals generated by facial receptors inhibits respiratory centre consequently triggers termination of respiratory muscles such as the diaphragm and intercostals causing reflex apnoea in order to inhibit aspiration of water (Hiebert Burch 2003). In a ddition, inhibition of respiratory centre stimulates cardiovascular centre and therefore increases parasympathetic activity via vagus nerve to start bradycardia , and as well stimulates sympathetic activity to vasoconstrict arterioles in limbs and non essential organs for instance the skin, intestines, and kidney causing them to rely on anaerobic conditions (Hiebert Burch 2003).This non essential organ vasoconstriction allows the redirection of blood flow to the brain and heart, this guards the brain from injury by supplying as much as oxygen that is needed , and reducing the brains requirement for oxygen by cooling (Hiebert Burch 2003).The decrease in PO2 is sensed by the arterial chemoreceptors from involuntary or voluntary breath hold , stimulates the cardiovascular centre to signal the SNS and PNS to complete the same antagonist functions completed in respiratory inhibition stimulus(Hiebert Burch 2003). Also the expected Bradycardia when simulating dive can be unsuccessful du e to emotional reasons such as fear, being distracted, being embarrassed, or in eagerness to submerge out of water could induce tachycardia response (Gooden 1994). In addition the experiments accomplished will show the stimulus in dive reflex and the physiological reasons behind those reflexes will be discussed. METHOD: First of all the investigation was accomplished using a subject seated on lab stool with the same posture, with their head down, and elbows resting on the bench. Chart 5 was setup and a finger transducer was connected to the subjects index finger. The subject sat quietly to rest heart rate and distractions were kept to smallest amount to avoid false recordings .The subjects palms were facing up to diminish finger movement as a result reducing signal dampening of finger transducer while recording . Prior to undertaking the diving experiments the subject practiced their breath hold; the subject took two deep breaths but not maximal breaths before holding their breath for 30 seconds. Every experiment lasted 1 and half minutes with recordings showing heart rate per min at: rest, 1st 15 seconds of breath hold, 2nd 15 seconds of breath hold, and recovery. For each dive stimulation, this was expected. Prior to the experiments it was noted not to force the subject from simulating a dive or b reath hold if they feel unpleasant doing so. The effect of diving was experimented on using different water temperatures, and snorkelling equipment. The water basin was positioned in front of the subject seated in appropriate posture staying motionless (it was furthermore important for the subject to remain motionless during the experiment as this triggered further signal dampening while recording heart rate) .the subject would take a deep breath and exhale to some extent and submerge their face in water up to cheeks, and yet again heart rate would be recorded for 30 seconds. These events were used for every breath hold dive simulation. For a more detailed method refer to MEDSCI 205 laboratory manual page 35-39. For the analysis of results % change in heart rate was calculated using the equation below: % change The above graph shows the percentage change in heart rate from the effect of apnoea caused by water temperature and pressure changes. The graph above shows the effect of apnoea only on heart rate of the subject which indicates that holding breath has a apparent change in heart rate compared to holding breath in cold water. The above graph represents the percentage change in heart rate due to the effects of temperature. Discussion: Investigating all data gathered from the experiments draw together the fact that bradycardia was observed in most of them. In table 3 the subject showed an increase in heart rate in snorkelling, the standard dive and holding breathing in warm water. As reviewed in the introduction the reason may be due anxiety or distractions which lead to the beginning of tachycardia (Gooden 1994). Snorkelling (shown on table 3) showed a noteworthy increase in heart rate instead of a bradycardia response, the fact that literature proposes on immersing face in water the body must begin reflex apnoea and diving bradycardia (Gooden 1994). Also in resting pulse 1st standard dive the 1st 15 seconds showed an increase in heart rate followed by significant decrease to 69.68 beats per min. The rapid decrease in the 2nd 15 seconds was due to the importance of the body adapting to retain oxygen reserve to supply vital organs (Hurwitz Furedy 1984). Analysing breathing in water with snorkel vs. Holding breath in cold water showed there were not such significant heart rate differences between the two experiments conducted .In breathing in water with a snorkel, there was a steady increase and decrease in heart rate from 7.9 % 16.1% change, but these heart rate measurements were in range if of resting pulse 55.82 beats per min measured at the start of the experiment. In comparison holding breath in cold water showed expected decrease in heart rate from resting pulse by 7.8% decrease in first 15 seconds to 16.6% decrease in second 15 seconds. This experiment shows that voluntary apnoea by itself causes bradycardia through the decreasing levels of PO2 which triggers arterial chemoreceptors ,that sends stimulating the cardiovascular centre to start appropriate responses via the parasympathetic and sympathetic pathways working destructively (Hurwitz Furedy 1984). Snorkelling showed a change in heart rate by 7.9 % and 16.1%, but the reaction was an increase in heart rate than a likely decrease as assumed in literature (Hiebert Burch 2003). Voluntary facial immersions in water according to literature should usually stimuli pressure receptors in face and obstruct respiratory muscles to begin reflex apnoea and in addition stimuli sympathetic to constrain blood flow and stimuli cardiovascular centre to begin bradycardia during the dive is model (Hiebert Burch 2003). Additionally the simulated dive with cold water demonstrated a likely bradycardia response with a decrease change in heart by 7.8% and 16.6% this implies that the sensitivity of cold wet receptors on the face can add to Bradycardia, in effort to reduce oxygen expenditure (Hiebert Burch 2003).While evaluating heart rate values obtained from snorkelling and breath hold in cold water, the experiment showed the stabilizer effects of cold water on decreasing the heart rate and that facia l immersion should show a Bradycardia response. (Hiebert Burch 2003) (Pauler, Pokorski, Honda, Ahn et al 1990. From the analysis of results it can be agreed upon that holding breath in warm water has to some level, less change in heart rate, in the first 15 seconds heart rate increased by 1.3% and decreased by 0.79% in second 15 seconds with a significant 13.1% increase in heart rate in recovery phase well over the normal resting pulse 62.0 beats per min a probable cause may have been anticipation to submerge out of water (Hiebert Burch 2003). Cold water, in comparison demonstrated the expected Bradycardia by illustrating significant change in heart rate from resting pulse by 7.8% in first 15 seconds to 12.3% in second 15 seconds, then restoring back to the resting pulse in the recovery phase. This experiment additionally confirmed that facial receptors are sensitive to cold and that immersion in cold water will constantly associate with a strong decrease in heart rate (Pauler, Pokorski, Honda, Ahn et al 1990). Also the variation in heart rate between warm water and cold water dive simulatio ns point out that cold water has additive effects on heart rate reduction by apnoea (Hiebert Burch 2003). Cold water demonstrated the majority of significant change in heart rate compared to other cues. The probable cause of this would be facial immersion in cold water, as this leads to reducing metabolic functions in an effort to lower the oxygen demand to peripheral tissue caused from hypoxia and tissue cooling (Hiebert Burch 2003). It has been stated by literature, that the higher the temperature the lower bradycardia responses expected the lower the temperature the higher the bradycardia responses expected (Gooden 1994). The second highest change in heart rate was shown in snorkelling which was not expected. The expected result was a small decrease in heart rate to explain pressure / wet receptors stimuli bradycardia (Hiebert Burch 2003).Holding breath in air showed the expected change in heart rate. The other cues experimented showed the added effects to breath hold will increase bradycardia compared to breath hold alone. Also warm water had showed small change in heart rate this pr oposed that it has little or no added effect to dive reflex response. Conclusion In conclusion in all cues experimented with breath hold and facial immersion a commencement bradycardia was observed this proposed that breath hold or apnoea plays an important role in the dive reflex. In addition facial immersion in cold water was established to be the most powerful stimulus of dive reflex.

Demonstrate How To Respond Essay

There are several different ways to respond to an individual’s reactions when communicating. As communication is a two way process, it important to respond to show that I am listening and that I understand the information being given. 2.4 There are many ways in which we can demonstrate how to respond to an individual’s reactions when communicating. A response during communication is needed for the communication to take place. If someone is talking to you and you are not responding, it is difficult for any communication to take place. When you respond to someone, it shows that you are listening to them, which then shows that you understand what they are saying and are interpreting it correctly. However, the response doesn’t need to be verbal. A simple nod can even be considered communicating, as long as both participants are aware of each other and understand what is being put forth. If a patient is upset and appears to be getting agitated whilst talking, a simple change of tone can help calm the situation down, also by using gentle hand gestures it could also help diffuse the situation and it also shows that you are listening to what they are saying. Another example is observing a patient when they are talking to you. You need to be aware of their body language as this can show any sign of anxiousness, agitation or stress. By looking at their facial expressions when you are speaking to them to see how they react to what you are saying. Eyes contact is also another thing to look at. If a person is avoiding eye contact with you it may be because they feel uncomfortable with what they are saying of hearing from you. It is essential that you feel the patient has understood what you have said, therefore by repeating what you have said and rephrasing what you have said ensure this. Also by leaving the conversation for a while then coming back to talk about it again may help.

David Hume’s Necessary Connection Essay

Hume questions why humans always make a necessary connection to events. Hume has always stated that it is impossible for humans to think anything that they have not already experienced. So to find the idea of Necessary Connection we have to look back on our impressions. We have to find where the idea of Necessary Connection came from. Hume argues that we cannot create new ideas for ourselves, which solidifies his position on Necessary Connection. Hume has an explanation for this his stand on Necessary Connection. Hume argues that there is cause instead of Necessary Connection. We cannot show the necessity of cause to every new existence without also showing that something’s existence depends on a productive principal. For example we are unable to explain why we are able to move our thumb. We know we can will it to do so but we do not know the process of the action. We are unable to connect all the biological connections such as nerves and impulses from our brain telling certain muscles and tendons to do the action of moving our thumb. Also, since all distinct ideas can be separated, and cause and effect are distinct ideas, we can conceive any object to be non-existent and then existent without attaching causality. This goes back to the ability, or non-ability, of humans to create an idea. There has to be a cause and effect in our minds when an event happens. Now, we go all the way back to the beginning of existence. The separation of the idea of cause from the beginning of existence is possible in the imagination. Hume says that we do not need to associate a cause with the beginning of existence.

Essay Solutions for Mcdonald Chapter 6 - 2832 Words

Chapter 6 Commodity Forwards and Futures Question 6.1. The spot price of a widget is $70.00. With a continuously compounded annual risk-free rate of 5%, we can calculate the annualized lease rates according to the formula: F0,T = S0 Ãâ€" e(r−Î ´l )Ãâ€"T ⇔ F0,T S0 = e(r−Î ´l )Ãâ€"T S0 = (r − ÃŽ ´l ) Ãâ€" T F0,T 1 ln T S0 ⇔ ln F0,T ⇔ ÃŽ ´l = r − Time to expiration Forward price Annualized lease rate 3 months $70.70 0.0101987 6 months $71.41 0.0101147 9 months $72.13 0.0100336 12 months $72.86 0.0099555 The lease rate is less than the risk-free interest rate. The forward curve is upward sloping, thus the prices of exercise 6.1. are an example of contango. Question 6.2. The spot price of oil is $32.00 per barrel. With a continuously compounded annual†¦show more content†¦It does not make sense to store pencils in equilibrium, because even if we have an active lease market for pencils, the lease rate is smaller than the risk-free interest rate. Lending money at ten percent is more proï ¬ table than lending pencils at ï ¬ ve percent. b) The equilibrium forward price is calculated according to our pricing formula: F0,T = S0 Ãâ€" e(r−Î ´l )Ãâ€"T = $0.20 Ãâ€" e(0.10−0.05)Ãâ€"1 = $0.20 Ãâ€" 1.05127 = $0.2103, which is the price given in the exercise. c) c1) Let us ï ¬ rst look at the different arbitr age strategies we can use in each case. Pencils can be sold short. We can engage in our usual reverse cash and carry arbitrage: Transaction Time 0 Time T = 1 Long forward 0 ST − F0,T Short-sell tailed pen- $0.19025 −ST cil position, @ 0.05 Lend short-sale −$0.19025 $0.2103 proceeds @ 0.1 Total 0 $0.2103 − F0,T For there to be no arbitrage, F0,T ≠¥ $0.2103 c2) Suppose pencils cannot be sold short. Then we have no ability to create the short position necessary to offset the pencil price risk from the long forward. Consequently, we are not able to ï ¬ nd a lower boundary for the pencil forward in this case. 81 Part 2 Forwards, Futures, and Swaps c3) Pencils can be loaned. We engage in a cash and carry arbitrage: Transaction Time 0 Short forward 0 Buy tailed pencil −$0.19025 position, lend @0.05 borrow @ 0.1 $0.19025 Total 0 Time T = 1 F0,T − ST ST −$0.2103 F0,T − $0.2103 For thereShow MoreRelatedSolutions For Families : Distressed Situations1551 Words   |  7 PagesSolutions for Families in Distressed Situations Caroline Aranda, Ashley Haver, Carlos Siao, Veronica Ortiz, Ronyel Calloway  Communication 8 California State University, Fresno 16 November 2016 TOPIC: Solutions for Families in Distressed Situations SPECIFIC PURPOSE: (Caroline) INTRODUCTION: (Caroline) CENTRAL IDEA: (Caroline) PREVIEW: (Caroline) [Transition 1: BODY: How do families become in these distressed situations? 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