hello everybody my name is Iman welcome back to my YouTube channel today we're starting a new playlist MCAT Behavioral Science now this playlist is based on the Kaplan book and today we're going to start with chapter 1 which is titled biology and Behavior now the objectives that we're going to cover in the chapter are the following first we're going to discuss the history of neuropsychology and we're going to talk talk about a couple of important individuals who really formed the foundation of current knowledge about neuroanatomy then we're going to move into learning about the organization of the human nervous system we're going to talk about the Central and peripheral nervous system and we're going to learn that the peripheral nervous system can be divided into two branches the somatic and the autonomic and we're going to discuss both then we're going to move into the organization of the the brain in this section we're going to identify various anatomical structures inside the human brain we're going to talk about how the the brain is divided into three categories we have the hindbrain midbrain and forbrain and we'll cover generally what each of these divisions consist of and in the fourth objective we're going to focus on the forbrain the forbrain forms the largest portion of the brain by which weight and volume and we're going to work through the different regions and functions of the forbrain Together Fifth we're going to move into a discussion on the influences on Behavior so merely describing the functions of the brain regions does not fully explain the wide variety of human behaviors that are possible other influences like chemical controls hereditary and the environment are all going to influence human behavior as well and so we're going to go over these influences together in the fifth objective and then last but not least we're going to talk about development the development process begins at the moment of conception and changes occur quickly so we're going to discuss and begin to understand these changes and when they occur with that being said the link between mind and body is definitely a Hot Topic in medicine this playlist is going to be extremely applicable to Future doctors and I hope you enjoy it with that being said let's go ahead and get started with our first objective which is all about a brief history of neuros psychology now during the 19th century the study of behavior underwent a significant transformation it shifted from a philosophical perspective to a more empirical and scientific one and this era marked the Genesis of our contemporary understanding of neuroanatomy and then it's con connection to cognition and behavior so in other words researchers in the 19th century they begin to think about behavior from a physiological perspective and many of these early thinkers formed the foundation of current knowledge about neuroanatomy and this is where we're linking the functions of specific areas of of the brain with thought and behavior and we're going to start by talking about a man named France gal he lived between 1758 to 1828 and he was one of the earliest um people who developed a theories that behavior intellect and even personality might be linked to brain anatomy and he specifically developed the doctrines of phenology all right the basic idea of phenology was that if a particular trait was welld developed then the part of the brain that's responsible for that trait would expand this expansion according to Gaul would push the area of the skull that covered that part of the brain outward and therefore cause a bulge on the head and then G believe that one could then measure um psychological attributes by feeling or measuring the skull of course his work was debunked but gul's ideas did spur some research into brain functions with that being said the next person that we want to talk about is Pierre Florence he was the first person to study the functions of the major SE sections of the brain and he did this by exter pation on rabbits and and pigeons so in extrap various parts of the brain are surgically removed and then the behavioral consequences are observed and what Florence's work showed and what it led to was his assertion that the brain had specific parts for specific functions and the removal of any part any one part weakens the whole brain now after Pier Florence we want to talk about William James who's known as the father of American psychology and he believed that it was important to study how the mind functioned in adapting to the environment and his view was among the first theories that formed a branch of psychology known as functionalism this is a system of thought and psychology that studied how mental processes help individuals adapt to their environment John Dewey is another important name in functionalism because his 1896 article is seen as its Inception so this article criticized the concept of the reflex arc which breaks the process of reacting to a stimulus into discrete parts do we believed that psychology should focus on the study of the organism as a whole as it functioned to adapt to the environment now around 1860 Paul brought comes into the scene he added to the knowledge of physiology by examining the behavioral deficits of people who have brain damage he was the first person to demonstrate that specific functional impairments could be linked with specific brain lesions and brocka found that a man who had been unable to talk was unable to do so because of a lesion in a specific area on the left side of the brain and this area of the brain is now referred to as brona's area another important individual is Herman Von Helm holes he was the first to measure the speed of a nerve impulse and by actually measuring the speed of a nerve nerve impulse in terms of reaction time Helm holds is often credited with the transition of psychology into a field of the Natural Sciences now just as a little bit of a a side note if you want to go over nerve impulses and uh any information on that we discuss these topics in mcap biology I believe you will learn more about the nervous system nerve impulses in chapter 4 specifically and I just wanted to let you guys know in case you're thinking about nerves and nerve impulses now and you're like got to touch up on that so that's where you can find that information now around the turn of the century Sir Charles sh darington first inferred the existence of synapsis so many of his conclusions actually have held over time except for one he thought that synaptic transmission was an electrical process but we now know that it's primarily a chemical one and again if you're interested in going over synapses also it's in chapter 4 in the mcap biology playlist now with that all right we've been introduced to a couple of in individuals a couple of scientists here and these Pioneers contributions were very critical in shaping modern Neuroscience however it is important to acknowledge that there are some ethical considerations regarding their methods particularly in animal research and studies involving patients with brain damage regardless a lot of this work definitely pioneered some of the current work that's that's being done in neuroscience and future directions in Neuroscience they continue to evolve with d with with Technologies like functional MRI which has really helped scientists learn about the brain and unravel the brain's Mysteries and as we build upon the legacies of these 19th century scientists our understanding of the brain and behavior continues to grow now with that introduction and with that brief history of neuros psychology let's move into our second objective which is on the organization of the human nervous system now the human nervous system is a complex web of over 100 billion cells that communicate coordinate and regulate signals for the rest of the body and mental and physical action occurs when the body can react to external stimuli using the nervous system so the goal of this objective then is to look at the nervous system and its basic organization to start we want to say that there are three kinds of nerve cells in the nervous system you have Sensory neurons also known as apher neurons they transmit sensory information from receptors to the spinal cord and brain then we also have motor neurons also known as efferent neurons they transmit motor information from the brain and spinal cord to muscles and glands and then the third type of neuron we have are interneurons these are found between other NE neurons and they're the most numerous of the three types of neurons inter neurons are located predominantly in the brain and spinal cord and they're often linked to reflexive behavior and neural circuits called reflexive arcs control this type Ty of behavior so for example let's pretend you're walking and you accidentally step on a Lego all right receptors in the foot detect the pain and the pain signal is going to be transmitted by Sensory neurons up to the spinal cord at that point the sensory neurons connect with interneurons which can then relay pain impulses up to the brain but rather than waiting for the brain to send out a signal inter neurons in the spinal cord are going to send signals to the muscles of both your legs all right they send signals to both of your legs the one that stepped on the Lego the signal is for you to lift that foot up so you are no longer incurring pain from stepping on that Lego and signal to your other leg to keep you supported and standing all right and so rather than waiting for the brain to send out a signal you have these interneurons in the spinal cord send signals to the muscles of both your leg directly and it's going to cause you to withdraw the foot with pain and support the other foot and the original sensory information though it still makes its way up to the brain however by the time it arrives there thankfully the muscles have already responded to the brain thanks to the reflexive Arc so that's a little bit of a motivation about the nervous system and our nerve cells so now let's turn to the overall structure of the human nervous system which is diagrammed here now the nervous system can be broadly divided into two primary components we have the central nervous system and the peripheral nervous system the central nervous system is composed of the brain and the spinal cord and then the peripheral nervous system is made up of nerve tissue and fibers outside of the brain and spinal cord this is going to include all 31 pairs of spinal nerves and 10 out of the 12 pairs of cranial nerves now the peripheral nervous system connects the central nervous system to the rest of the body and it itself can be subdivided into the sematic and autonomic nervous system what is the difference between these two well the the the sematic nervous system it consists of sensory and motor neurons that are distributed through the skin joints and muscles all right the autonomic nervous system it generally regulates heartbeat respiration digestion and glandular secretions in other words the autonomic nervous system manages the involuntary muscles that are associated with many of those internal organs and glands and it also helps regulate body temperature the main thing to understand about these functions is that they are automatic or they're independent of conscious control and you can note the similarity in the words so that it's easier to remember autonomic nervous system is automatic all right so that's one way to keep in mind now the autonomic nervous system itself has two subdivisions the sympathetic nervous system and the parasympathetic nervous system and these two branches often act in opposition to one another one another meaning that they're antagonistic so for example the sympathetic nervous system acts to accelerate heart rate and inhibit digestion while the parasympathetic nervous system decelerates heart rate and increases digestion now the main role if we were to focus first let's talk about this parasympathetic nervous system the main role of the parasympathetic nervous system is to conserve energy to conserve energy it is associated with resting and sleeping States and it acts to reduce heart rate and constrict the bronchi the parasympathetic nervous system also responsible for managing digestion and it does this by increasing peristalsis and exocrine secretions now on the other hand we could talk about the sympathetic nervous system the sympathetic nervous system is activated by stress and it can include everything from a mild stressor to emergencies the sympathetic nervous system is closely associated with rage and fear reactions also known as fight or flight all right so sympathetic nervous system you can remember as flight or fight and on the other hand you can remember parasympathetic as rest and digest so that's one way to help you remember what does what here regardless the sympathetic nervous system when activated can increase heart rate redistribute blood to muscles increase blood glucose concentration relax the bronchi decrease digestion and dilate the eyes to maximi maximize light intake and all of those are kind of summarized in this infograph right here so we have the parasympathetic nervous system what happens to the pupil it constricts what happens to the heart rate it slows down what happens to the Airways well the parasympathetic nervous system can constricts the bronchi and the liver oh the parasympathetic nervous system stimulates bile release it constricts blood vessels it stimulates the digestive uh system Etc on the other hand we have the sympathetic nervous system what happens to the pupil dilates and heart rate is increased Airway well here you're going to have dilation of the bronchi sweat glands they're going to be stimulated stimul Ates secretion liver is going to increase the rate of glycogen to glucose the digestive system is going to decrease activity so with that being said we've talked about what we need to for the organization of the nervous system the next thing we want to talk about is the organization of the brain the organization of the brain and here what we want to talk about is the three main divisions that we can um Define for the brain and different parts of the brain are going to perform remarkably different functions so for example one part of the brain processes sensory information while an entirely different part of the brain maintains activities of the internal organs now for complex functions several brain regions are going to work together and those are kind of the things that we're going to see as we talk talk about the organization of the brain here in the third objective and also when we focus on the for uh forbrain in the fourth objective so let's start with a couple of notes the first note is that the brain has three subdivisions that's the hindbrain the midbrain and the forebrain and also the brain I'm going to scroll down from these notes now show you this image of the brain with a lot of the regions labeled here we're going to be covering over these different regions of the brain and their functions but even before we get to any of that it's important for us to talk about what the brain is covered with the brain is covered with a thick sheath of connective tissue called the meninges all right the meninges help protect the brain keep it anchored within the skull and resorb uh cerebral spinal fluid it's composed of three layers the Duram Moder the arachnoid mod and the Pia Mo now cerebral spinal fluid is the aquous solution in which the brain and spinal cord rest and it is produced by specialized cells that line the ventricles of the brain now what I want to do is I want to scroll back up to where we saw these notes on the three subdivisions of the brain right the human brain can be divided into three basic subdivisions the hind brain the midbrain and the forbrain now something that's really interesting is that in terms of physical location and functionality there's a significant correlation and what I mean by that is you'll notice that as we talk about brain structures we're going to see that brain structures associated with B basic survival are going to be located at the base of the brain and brain structures with more complex functions are located higher up and the meaningful connection between brain location and functional complexity is no accident so in evolutionary terms the hindbrain and the midbrain were brain structures that developed earlier together they form the brain stem which is the most primitive region of the brain the forbrain developed later including the limpic system is a group of neural structures primarily associated with emotion and memory things like aggression fear Pleasure and Pain are all related to the lyic system now the most recent evolutionary development of the human brain is the cerebral cortex which is the outer covering of the cerebral hemispheres in humans the cerebral cortex is assoc iated with everything from language processing to problem solving and from impulse control to even long-term planning now we're going to talk about each of these subdivisions in details but an obvious question to ask is how do these different parts of the brain develop well in prenatal life the brain develops from neural tube at first the tube is composed of of three swellings which correspond to the hindbrain midbrain and forebrain now both the the hindbrain and the forebrain later divide into two swellings creating five total swellings in the mature neural tube all right and the eonic brain is diagrammed right here as you see and the subdivisions are shown as well and it is what we're going to talk about in detail next the first thing we're going to start off with is talking about the Hind brain it is located where the brain meets the spinal cord and it's also referred to as the rhomin sephylon it controls balance motor coordination breathing digestion and general arousal processes such as sleeping and waking so in short the hind brain manages vital functioning necessary for survival during embryonic development the romen sephylon is going to divide to form the myin sephylon and the Menan sephylon the myin sephon becomes the medula oblongata and the mettin sethlon becomes the ponds and the cerebellum now the medula obligant is a lower brain structure that is responsible for regulating vital functions such as breathing heart rate and blood pressure and again that is associated with the Mylon so we're going to go ahead and write that medula oinga now the met and sephylon like we said all right becomes the ponds and the cerebellum ponds and cerebellum the ponds lies above the medula and it contains sensory and motor pathways between the cortex and the medula now at the top of the hind brain mushrooming out of the back of the ponds is the cerebellum and this is a structure that helps maintain posture and balance and coordinates body movements if you were to damage your cerebellum this would cause clumsiness it would cause slurred speech and it would result in a loss of balance so that is the hind brain for us let's scroll back up here where we write our e away notes it contains the cerebellum the medula oblongata and the ponds and what is the function it it functions to help motor movements vital functioning like breathing and digestion arousal and alertness with that we can move into discussing the midbrain now just above the hindbrain is the midbrain also referred to as mlon it receives sensory and motor information from the rest of the body and it is associated with involuntary reflux responses that are triggered by visual or auditory stimuli now there are several prominent nuclei in the midbrain two of which are collectively called the calculi the superior calculus is going to receive visual sensory input and the inferior calculus is going to receive sensory information from the auditory system so let's write that down the midbrain also referred to as the messen sephylon all right it has several prominent nuclei there's several prominent nuclei in the mid midbrain and it's called culi all right and you have Superior and inferior fantastic now now we can move into talking about the forbrain now this is going to be very just preliminary information about the forbrain because the fourth objective is completely dedicated to talking about the forbrain in depth but above the midbrain is the forbrain also referred to as the proon It's associated with complex perceptual cognitive and behavioral processes now among its other functions the forbrain is associated with emotion and memory and it is the forebrain that has the greatest influence on human behavior it functions its functions are not absolutely necessary for survival but they're associated with intellectual and emotional capacities that are descriptive and characteristic of human beings now during prenatal development the proen seylon divides to form the Talen sephylon the tlon is going to form the cerebral cortex it's going to form the basil ganglia basil gangli oh my pen is failing me right now and in addition to that the limic system it will also form the dlon the DI sephon forms the thalamus the hypothalamus the posterior pituitary gland and the penal gland so let's go ahead and write that down Thalamus the hypothalamus the pituitary gland or posterior pituitary gland and the penal gland so there we have it now before we move into the fourth objective where we talk some more about the forbrain we want to go ahead and talk about something that's important to recognize and that's the methods of mapping the brain one traditional method involves studying patients with brain lesions however the challenge here is that lesions often affect multiple brain areas and that makes it difficult to pinpoint which area is responsible for a specific specific functional impairment now to overcome this researches researchers study brain lesions in laboratory animals and so in these controlled settings precise lesions can be created and then you can study what that lesion causes in terms of consequences and then associate specific brain regions with specific functions now something else that's really interesting is that electrical stimulation and recording of brain activity is another method to study the brain in humans this involves stimulating the brain cortex with a small electroid this is going to cause neurons to Fire and activate specific behaviors or perceptions and this technique helps neurosurgeons create cortical maps and it can actually be used on awake patients since the brain itself doesn't have any pain receptors of course with some local anesthesia it can also be done on lab animals electroids have also been used in lab animals to study deeper regions of the brain and of course depending on where they're implanted the electroids can elicit a range of actions it can elicit sleep or sexual arousal Rage or Terror and stimulation of different brain regions can be upon that researchers can study the actions that happen as a consequence of that fantastic it now electroids can also be used to record electrical activity produced by the brain itself so in some studies individual neurons are recorded by inserting Ultra sensitive micro electroids into individual brain cells and then recording their electrical activity electrical activity generated by a larger group of neurons can be studied using an EEG which involves placing several electroids on the skull uh on the scalp I should say my apologies and Broad patterns of electrical activity can thus be detected and recorded and this procedure is noninvasive so it doesn't cause any damage and it can be commonly used with human subjects in fact research on sleep seizures and brain leisures relies heavily on these eegs with that we have completed our third objective I'm going to go ahead and stop the video here in the next part we're we're going to continue with our fourth objective which is on parts of the forbrain and I hope this was helpful let me know if you have any questions comments concerns down below other than that good luck happy studying and have a beautiful beautiful day future doctors