in this last part of chapter 23 we're going to look at how our respiratory mechanisms are regulated now there are going to be mechanisms for regulation both at the local level within the tissue and then also neural control let's start with looking at mechanisms or methods that we find locally in the tissue to regulate the rate of respiration so if the carbon dioxide par partial pressure or concentration levels increase this is going to result in Vaso dilation so that smooth muscle will relax and this is going to allow the increase of blood flow to this area and that's going to result in an increase exchange of your gases in that area so think of active skeletal muscle inv Vaso dilation however in the lungs that pulmonary circuit it's a little bit different and we started to talk about this a little bit in the previous video so what we see in the capillary beds that surround the Alvi is that there is going to be a attraction or a shunting of blood towards the Alvi in which the concentration or the percentage of oxygen present is high so this is a little bit opposite for what we see with skeletal muscle if the LV a particular region of the lung is not functioning well and air is not flowing into and out of the Alvi efficiently the capillaries are not going to dilate in that region in fact the blood will be shunted towards the LV that are functional this is referred to as the ventilation to profusion Ratio or VQ and this makes sense because why would we want to send blood to nonfunctioning lvi if they cannot provide the oxygen that the red blood cells are there to pick up I think of it like going to the gas station sometimes when there's shortages there may there are two gas stations at the end of one of the streets that goes by my neighborhood let's say one of those gas station is all out of gas and the other gas station at the other end of the street has gas am I going to go to the gas station where the tanks are empty no that would be a waste of my time I'm not going to be able to get the gas that I need but I will go to the gas station where there is gas in the tanks even if I have to wait in line I can fill up it's the same with the capillaries surrounding the Alvi so a little bit backwards in the pulmonary circuit compared to skeletal muscle and this we mentioned previously if there is an increase in the partial pressure of carbon dioxide associated with increase hydrogen levels that's going to result in the Bronco dilation and vice versa if we see a decrease with carbon dioxide levels now let's look on to how our nervous system regulates respir respiration we have areas in our brain that are going to function to regulate our breathing subconsciously and then most of us are familiar with the ability to regulate our breathing we can take in deep inhalations when we want to want to or exhale deep strongly as well when we choose to so the subconscious or involuntary areas that regulate our breathing are found in the medulla aanga and the ponds and these are those areas we call nuclei where we have cell bodies and synopsis associated with a particular function when we want want to voluntarily control our breathing that's going to involve higher order areas of the brain such as the cerebral cortex even though we usually associate low oxygen content as the driving force to increase our breathing and yes it it is true it is important if we're running out of oxygen we're going to want to breathe however we're going to learn that the driving force is really the carbon dioxide level let's look at these regions in the brain that are going to function to help us regulate our breathing rate and Rhythm so here we are in the medulla ablang and we find two regions called centers that are respiratory groups so a dorsal respiratory group and a vental respiratory group this picture will come up multiple times we'll keep coming back to it so here's the medulla ablang we've got a respiratory Center we have a dorsal respiratory group within that Center and a vental respiratory group within this Center these centers or these groups are going to have communication with each other and other regions of the brain are also going to communicate with them let's look at how it works so the regions the respirator dorsal respiratory group is going to function with a property of automaticity similar to what we saw with the cardiac tissue and we will see activity in this group occurring at approximately 2C intervals and I'm not sure of the mechanism by which the activity starts uh as we are aware of how this occurs in cardiac tissue but what we see is in this dorsal respiratory group there is the function for inhalation so we call this the inspiratory center and this is going to be involved not just in regular quiet breathing but also when we are giving forced inhalations let's look at how this functions just during just normal breathing so at approximately 2 second intervals this dorsal respiratory group is going to become active it's going to stimulate those muscles involved in inhalation the diaphragm the external intercostals so here's our dorsal respiratory group sending the message down for these muscles do come active and we inhale now these neurons are active for about 2 seconds and then they cease being active and so we move into exhalation which is the passive process so this if you follow this diagram it is actually quite helpful in understanding this cyclical action of breathing of just a regular quiet breathing now the vental respiratory group is going to have neural tissue associated with both inhalation and exhalation however this respiratory group is only going to function when we have forced exhalation and inhalation so if that dorsal respiratory group becomes more active than normal that's going to stimulate the vental respiratory group to become active and the vental group will begin to activate those accessory muscles that we looked at previously that are involved in a forced inhalation so we see that how we can follow this cycle here with the drg and the vrg once again once activity is stopped then the muscle these a become inactive and exhalation will begin now the other area of the brain that helps to regulate breathing is called is found in the ponds and there are two areas one is called the apneustic center and the other is the pneumotoxic center and once again these communicate with each other and they communicate with the respiratory groups that we saw in the medulla ablang so let's take a peek here at our pond so we can see our pond we have a pneumotoxic center and an apneustic Center and we can see that we have both stimulatory and inhibitory activity occurring between all these regions also previously when you may have noticed that we've got cranial nerve 10 the vagus nerve and also cranial nerve 9 is going the glossop fenial nerve is going to be communicating with these respirat groups so let's go back and see how the apneustic center and pumat taxic centers function the ostic center is going to stimulate that dorsal respiratory group so we're increasing the we're stimulating inhalation the pneumotoxic center is going to stimulate exhalation so essentially these are working in collaboration to create that very smooth rhythmic action that we associate with our normal quiet breathing now if we lose functioning of the pneumotoxic pneumotoxic center then we increase our apneustic so we inh increase our inhalation we lose that smoothness of the inhalation ending and moving into a passive exhalation and so apneustic breathing can be S of like a gasping bright breathing here we see the abnus stic center is going to stimulate the drg whereas the apneustic is going to inhibit the apneustic and so it will lead to that smooth transition to exhalation these respiratory recenters are going to respond to different types of stimulus very important is the chemical constituents in our body fluids that are detected by chemo receptors that are going to communicate about respiration the Barrow receptors detecting stretch such as blood pressure are also relevant we have stretch receptors such as in our lungs that are going to help us regulate our breathing rate and Rhythm there may be some type of irritant such as something in our nose or throat that that we have inhaled that can influence this also and just as an additional thought our breathing rate can change in response to other kind of miscellaneous types of stimulus pain we usually increase our breathing rate as well as if we become hot so let's look at how the chemo receptors function with respiration so here we're bringing in cranial nerve 9 and cranial nerve 10 these nerves are going to detect the levels of pH and partial pressure of oxygen in the blood at both the kateed bodies and aortic bodies we also have chemo receptors that are Central and these are going to be found within the medulla ablang and these chemo receptors are detecting the carbon dioxide levels and hence pH of the cerebral spinal fluid this is a really sensitive and important component of how we regulate our breathing if our partial pressure of carbon dioxide elevates this is called hyper capnia so this is caused by hypoventilation meaning we are not moving the air into and out of our Airways efficiently there are multiple causes of this it could be an obstruction it could be mechanical within the lungs and thoracic cavity it could be neural something has in inhibited the brain stem those respiratory centers some type of uh alcohol or drug if we are not exhaling out the carbon dioxide that our body is metabolizing and producing then the concentration or the partial pressure in our blood is going to increase that is called hyper Capia our respiratory centers our chemo receptors are going to detect this especially the chemo receptors in our medulla ablang those Central chemo receptors and stimulate our respiratory centers to cause us to increase our breathing rate we need to get that carbon dioxide out on the other hand if our partial pressure of carbon dioxide in our blood or the concentration of carbon dioxide in our blood gets too low we call this hypocapnea and this is going to be caused by hyperventilation so we're over breathing we are exhaling out more carbon dioxide than our body is producing so the concentration in our blood goes down this is detect Ed once again by chemo receptors but since there is not a large volume of carbon dioxide present the chemo receptors are not going to stimulate the respiratory rate there is a an association between blood pressure and our breathing you know which came first a chicken or egg I'm not exactly sure however uh we do know that if someone begins to breathe deeply slowly it is going to be associated with decreasing blood pressure so if you see a friend who's getting all agitated and upset for some reason and you tell them off the off the top of your head just just breathe calm down breathe deep breathe Bree in breathe out it's true it will help to lower the blood pressure and calm the body two other reflexes involved in respiration are called The hearring Bu Brewer reflexes so essentially this is going to be involved with inflation and deflation the inflation component of this reflex is going to detect stretch of the lungs and uh prevent overexpansion over breathing too much so we're going to inhibit that dorsal respiratory group so we don't overexpanded component of this reflex is going to uh detect if the lungs are underinflated or deflated and make sure we don't keep exhaling or cause us to inhale uh signaling the lungs are not full let's breathe and then we have uh just automatic reflex responses to noxious or irritating stimuli uh whether it's something we breathe in a chemical or maybe some uh debris and this is going to cause us to have reactions uh such as sneezing or coughing to to help us rid these irritants from our system now now Pia is the term we use for breathing and if you put an A in front of it it means without so apnea is going to be an event in which the the U respiratory activity is stopped for a bit and then you you'll Force really um ex exhale out that air so this would be an example of what we see with the sneezing or coughing kind that that very forceful action trying to rid the body of of some type of debris that has gotten in accidentally uh we often are familiar with the term sleep apnea so this is when uh during someone's sleep they stop breathing for a period of time sometimes you can have an irritant that will cause a spasm in this Airway and as far as the superior higher order involvement with our brain and breathing most of us are familiar with the fact that not only can we voluntarily make ourselves take a deep breath in or Force our breathing out but we also know that um anxiety stress excitement can cause us to change our respiratory rate so let's go back to that picture that I kept bringing up previously and it shows here we see the higher order Center of our brain can either stimulate or inhibit the breathing rate and Rhythm exercise is also going to change our respiratory rate and this is going to involve the sympathetic system which apparently even be before you hit the pavement the sympathetic system is going to become active and help you get ready with your respiratory rate for the changes in your breathing