in this video I'm going to briefly review some of the major parts of the central nervous system focusing on those that are going to be relevant to our discussion of CNS drugs now first and foremost remember that in order for the brain to function it has to have sugar and it has to have a high enough blood pressure every second of every day it only takes one time having low blood pressure or low blood sugar and then you pass out and lions eat you that's no good so most of the systems in your body work to increase blood pressure and increase blood sugar we'll come back to this when we study the cardiovascular and endocrine drugs all right as for CNS Anatomy we humans are privileged enough to have a nice big portion of the what are called higher order or thinking parts of the brain called the cerebrum the cerebrum surrounds a more primitive part of the brain called the diyon and that surrounds the most primitive part of the brain which just sort of keeps you alive that's the brain stem sitting behind brain is the cerebellum and all of this sits on top of the spinal cord which along with 12 cranial nerves relays information to the rest of the body now let's start with the cerebrum now there's a cerebral cortex and a cerebral medulla in anatomy the word cortex corresponds to the choc outside and the medulla refers always to the insides which in the case of a Reese's Peanut Butter Cup is made of peanut butter similarly in the cerebrum the cortex surrounds the medulla the cortex is the gray Mattern is made up mostly of cell bodies of the brain cells and the cerebral medulla is all the connections between those cells the cerebrum contains areas important for voluntary action such as thinking speaking comprehension Reading Writing mathematics memory intelligence personality that is all the cool stuff that humans are really good at uh as compared to say rats this is my friend Schmo the Executioner now he's very clever he knows a lot of tricks uh but he's complete rubbish at differential equations and I think you can see there is definitely a difference in the size of our brains and he's quite got quite a lot more um midbrain and brain stem rather than cerebrum the cerebrum consists of four main loes uh my personal favorite of course is the occipital load which is important for vision but there are also the frontal temporal and parietal lobes very generally speaking the frontal lobe is pretty good at problem solving parietal lobe is good for touch and vibration the temporal lobe is good at language and memory uh they're all important for movement but let's be honest it is not that simple in the olden days uh portions of the brain were roughly classified by their physical and anatomical structures but nowadays we have a much better feeling for the functional parts of the brain uh because of tools that we have like you know functional emogene like pet scans so now we can divide structures by function rather than just the way they look on a cadaver now before we go on I just want to point out two big functional structures that are partially in the cerebrum and partially deeper down there's the basil ganglia which coordinates gross muscle movements some unconscious movements starting and stopping movements uh and muscle tone we're going to talk about the basil ganglia with specific reference to Parkinson's disease and the side effects of some of the anti-dopamine drugs particularly those used for psychosis next I want to mention the lyic system which regulates emotional and behavioral response to stress and threats to survival so that's things like fear rage anxiety and pleasure and uh the lyic system is thought to be related to addictive behavior remember that addiction is different from dependence when it comes to drugs next we've got the dlon and within that we have the pineal gland the pineal gland is responsible for circadian rhythms which are which has to do with our 24 almost 24-hour internal clock and the pineal gland secretes melatonin to help you regulate your sleep cycles it's pretty well known that disruption of sleep usually worsens any kind of condition having to do with the brain next up in the diyon we have the hypothalamus which is a huge deal it's a heavy hitter in the body it controls and regulates uh not only autonomic nerves system and therefore the blood pressure and the heart rate but it also has an important part to play in the regulation of mood appetite body temperature the ph and osmolarity of your blood uh and it helps to keep you awake so there's a lot of stuff that goes on with the hypothalamus now when I went to medical school in the late 80s and early 90s uh the part of the hypothalamus that produces hormones like ADH which is anti-diuretic hormone uh which is important for regulation of blood volume and oxytocin that part of the hypothalamus was called the posterior pituitary but it's been since sort of turned into part of the hypothalamus now the hypothalamus also regulates the pituitary gland which is going to be a big deal when we talk about endocrine drugs uh next up in the dlon is the thalamus oh wait I don't care about the thalamus let's move on now we're getting to the brain stem which sits sort of on the top of the spinal cord and again because of its position part of the function of the brain stem is going to just be relaying information between the spinal cord and the other parts of the brain and the cereum etc etc the brain stem is also where most of the cranial nerves originate now there's something that runs throughout the brain stem called the reticular formation and it has a lot of different functions but I want to point out the reticular activating system or the RAS that is part of the reticular formation but the reticular activating system is a series of fibers that are either activating or inhibitory and they regulate how awake you are so if there's loud music and bright colors and people around you are screaming and firing off weapons the RS keeps you awake so that you can deal with the excitement in contrast when you are in a dark quiet room and someone is droning on and on about brain anatomy the RAS is inhibited and you fall asleep pharmacologically speaking the RAS is inhibited by the CNS depressants like alcohol barbituates benzodiazapines and it's excited by stimulants like amphetamines and caffeine and we're going to come back to all those drugs in the next lecture now all three of the main structures in the brain stem the midbrain the ponds and the medulla oblongata are crucial cral to numerous physiologic systems and I don't want to get into all that let's just say that the hypothalamus is a heavy hitter and the brain stem is also crucial to keeping oxygenated blood and sugar coming to our brain so we don't pass out and you know what uh first the midbrain uh it has a lot of different functions I like the ones where when somebody scares you you jump away and look at what was scaring you and that's actually a reflex so when you see people getting scared on TV and everyone laughs they're just displaying their regular normal brain function it's not really that funny more immediately relevant to this to this Farm class is the substan this is one of many centers important in controlling movements but it's particularly critical in Parkinson's disease that ponds it helps your medulla with breathing it helps you remember not to urinate on yourself but I want to get to the best part which is of course the medulla oblongata my favorite part of the brain just the name is beautiful it sounds like the name of a beautiful woman anyway the medulla does a lot of things including regulating the raas and therefore regulating how awake you are uh there's also cardiovascular centers in the medulla oblongata which keep your heart beating and work on your blood vessel constriction and dilation there's a breathing Center which is huge in terms of uh drug toxicity there's also a vomiting Center and what's called the chemor receptor trigger Zone which we'll get back to when we talk about GI drugs other things that the medulla oblongata controls are the larns your tongue swallowing coughing sneezing hiccups and of course you've got all those cranial nerves uh part of seven and eight and then you got 9 10 11 12 the medulla blata becomes a big deal in this class because of what's called medular depression that's depression of the medulla is called medular depression so meary depression is something that causes death in cases of overdose of CNS depressants like alcohol opiates or any drugs that mimic the action of Gaba like benzodiazapines or barbiturates or even anesthetics and the result of that is that you stop breathing and stop and your heart stops beating which is not good for you all right lastly we have the cerebellum the cerebellum regulates posture and balance cerebellum is really important for coordinating very complex movements it Compares what movement your brain was intending to do with what actually happened uh and that has to do with proception which is your body's ability to know where it is in space at any time I think a great example of how your cerebellum works and how it helps you is the task of carrying a picture of water downstairs without spilling it now again remember that regulation of movement is incredibly complicated with components of the motor cortex of the cerebrum other parts of your cerebrum the basil ganglia Thalamus brain stem cerebellum all sorts of places and because of that a very small lesion somewhere in your brain will produce noticeable movement problems and that's actually very helpful in diagnosis of disease or injury all right next thing to review will be neurotransmitters and then we're going to get into talking about CNS drugs woohoo