hello everybody my name is Iman welcome back to my YouTube channel today we're continuing our lecture on biology and behavior and we made it to the fifth objective which is influences on Behavior now like we said in the previous video human behavior is also influenced by other factors like chemical controls hereditary and environmental factors which collectively contribute to the diversity and complexity of human behaviors in this objective we're going to start with discussing chemical controls first AKA neurotransmitters now more than 100 neurotransmitters have been identified but we're only going to focus on seven that we need to know for the mcap and we start off with acetal choline acetyl choline is a neurotransmitter that's found in both the Central and peripheral nervous systems in the peripheral nervous system acetylcholine is used to transmit nerve impulses to the muscle and in the central nervous system acetylcholine has been linked to attention and arousal next is epinephrine and norepinephrine now epinephrine norepinephrine and dopamine are three closely related neurotransmitters known as catac colomines and due to the similarities in their molecular composition these three transmitters are also identified as monoamines or biogenic amines the most important thing to know about catacol amans is that they all play important roles in the experience of emotions but now just to focus on epinephrine and norepinephrine EP epinephrine also known as adrenaline and nor epinephrine also known as nor adrenaline are involved in controlling alertness and wakefulness and as the primary neurotransmitters of the sympathetic nervous system they promote the fight ORF flight response whereas nor epinephrine more commonly act as a local at the local level as a neurotransmitter epinephrine is most often secreted from the adrenal Med medula to act systematically as a hormone now low levels of norepinephrine are typically associated with depression whereas high levels are associated with anxiety and Mania next up is dopamine dopamine is another catacol amine that plays an important role in movement and posture high concentrations of dopamine are normally found in the basil gangli which helps smooth movements and it helps maintain postural stability imbalances in dopamine transmission has been found to play a role in schizophrenia and an important theory about the or the origin of this mental illness is called the dopamine hypothesis of schizophrenia the dopamine hypothesis argues that Illusions hallucinations and agitation associated with schizophrenia arises from either too much dopamine or from an over sensitivity to dopamine in the brain now although the dopamine hypothesis hypothesis of schizophrenia is an important Theory it doesn't account for all the findings of the disease so that is something to be cautious of then we have serotonin serotonin along so serotonin along with the catacol amine serotonin is classified as a monoamine or a biogenic immune neurotransmitter it is generally thought to play roles in regulating mood eating sleeping and dreaming and like norepinephrine serotonin is thought to play a huge role in depression and Mania so an overs supply of Serotonin is thought to produce manic States and an under Supply is is thought to produce depression now the next three that we want to talk about are Gaba Glycine and glutamine so the neurotransmitter Gaba it produces inhibitory post synaptic potential and it's thought to play an important role in stabilizing neural activity in the brain Gaba exerts its effects by causing hyperpolarization of the post synaptic membrane glycine may be better known as one of the 20 proteinogenic amino acids all right it serves as an inhibitory neurotransmitter in the central nervous system and it does so by increasing chloride influx into the neuron this is going to hyperpolarize the post synaptic membrane very similar to the function of Gaba and finally we have glutamate this is another one of the 20 proteinogenic amino acids it also acts as a neur neurotransmitter in the central nervous system but in contrast to glycine it's an excitatory neurotransmitter and then last but not least we want to talk about peptide neurotransmitters now studies suggest that peptides are also involved in neurotransmission the synaptic action of these neuromodulators also called neuropeptides it involves a more complicated chain of events in the post synaptic cell than any of those regular neurotransmitters we've discussed th thus far neuromodulators are therefore then relatively slow and they have longer effects on the post synaptic cell than neurotransmitters the endorphins which are natural painkillers that are produced in the brain are the most important peptide to know endorphins have actions that are similar to Morphine or other opioids in the brain in the body I should say all right now we've discussed the relatively fast communication Network that is the nervous system and the nervous system uses chemical messages called neurotransmitters the endocrine system is the other internal communication Network in the body and it uses chemical Messengers called hormones the endocrine system is somewhat slower than the nervous system because hormones travel to their target Destin ations through the bloodstream but let's go ahead and talk about this the hypothalamus links the endocrine and nervous system and in addition to the roles that we described earlier about the hypothalamus the hypothalamus also regulates the hormonal function of the pituitary gland the hypothalamus and the pituitary gland all right the the hypothalamus and the pituitary gland are spatially close to to each other and control is maintained through paracrine release of hormones into the hypophysial portal system that directly connects the two organs now the pituitary gland sometimes referred to as the master gland it's located at the base of the brain and it's divided into two parts all right it's divided into two parts anterior pituitary gland and the posterior pit AR gland fantastic now it is the anterior pituitary that is the master because it releases hormones that regulate activities of endocrine glands however the anterior pituitary itself is controlled by the hypothalamus the pituitary secretes various hormones into the bloodstream and then that travel to other endocrine glands that are located elsewhere in the body body to activate them and then once activated by the pituitary a given endocrine gland manufactures and secretes its own characteristic hormones into the bloodstream then we have the adrenal glands these are located on the top of the kidneys they're also divided into two parts we have the adrenal medula and we have the adrenal cortex now the adrenal medula releases epinephrine and norepinephrine as part of the sympathetic nervous system the adrenal cortex produces many hormones called cartic steroids including the stress hormone cortisol now the adrenal cortex also contributes to sexual functioning by producing sex hormones like testosterone and estrogen then we have the gats these are the sex GL glands of the body ovaries in females testes in males and these glands they produce sex hormones in higher concentrations leading to increased levels of testosterone in males and increased levels of estrogen in females these sex hormones increase libido and they contribute to mating behavior and of course sexual function now we've talked about neurotransmitters and we've talked about the endocrine system remember this objective is influences on Behavior the next thing that we want to talk about in this realm then is genetics and behavior so just as physical traits are inherited from parents behavioral traits can be as well evidence for the inherited nature of behavior comes from the fact that many behaviors are species specific so for example many animals exhibit mating behaviors that are only only seen within their species behaviors can also be bred into a species so many breeds of dogs for example have been bred for certain traits and behaviors behaviors are also seen to run in families so often times things like violence and aggression are observed being passed along in a family line just as well as mental illnesses are so here though it's really important for us to step back and distinguish the difference between innate and learned behaviors innate behaviors is an inherent part of an individual it's genetically programmed and observable across all members of the species irrespective of their environment or experiences on the other hand learned behaviors develop through experience and interactions with the environment the adaptive value of a behavior or trait is its contribution to the species evolutionary Fitness leading to adaptations through natural selection now the debate over the extent to which behavior is determined by genetics nature versus the environment nurture is ongoing and complex and you've probably heard of nature versus nurture nature refers to the influence of inherited characteristics on Behavior while nurture encompasses the impact of the environment and experiences the consensus is that behavior is going to result from an interplay between both genetic and environmental factors so for instance one may have a genetic predisposition to addiction but it's environmental exposure to addictive substances or activities that's going to be necessary for that addiction to develop now there are ways that researchers can kind of facilitate and observe this nature versus nurture ratio and Research into the genetic basis of of behavior commonly employs things like family studies twin studies and adoption studies so family studies they assume that genetically related individuals are going to be more similar than unrelated ones however they can't clearly differentiate between shared environmental and genetic factors because both are present in the family setting so for example while family studies show a higher incidence of schizophrenia in the children of schizophrenics it's kind of unclear if that's due to genetics or because they share an environment with their parents who are schizophrenics so while family studies are important in kind of observing um this nature versus nurture ratio sometimes it doesn't fully tell the story because you can't differentiate between shared environments and genetic factors when you are when both are present in a family setting what something else that you can do is twin studies you can compare identical or monozygotic and fraternal or dizygotic Twins and this usually offers more insight now identical twins they share all their genes while fraternal twins they share only about 50% and by comparing traits in identical and fraternal twins especially those that are raised apart researchers can better assess the influence of genetics versus environment so something that's interesting is that Studies have shown that identical twins even when raised separately exhibit more similar traits than fraternal twins that are raised together and so this kind of suggests a strong genetic component here adoption studies also Pro provide further insight and understanding by comparing adopted children all right to their biological parents and also their adopted parents and kind of seeing and comparing and contrasting these Studies have found that certain traits like IQ are more similar between adopted children and their biological parents than their adoptive ones and that include that that indicates a heritable component and similarly patterns of criminal behavior in adopted um children also shows a trend of heritability so in conclusion first and foremost this this is a difficult topic and there's a lot of research and a lot of things to kind of break down before having this discussion we're kind of keeping it really surface level because that's all you need to know for the MCAT but both genetics and the environment play crucial roles in shaping behavior all right and the relative contribution of each varies depending on the trait in question with some traits being more strongly influenced by genetics While others more by environment envir environmental factors all right with that we have completed objective five we're going to go ahead and end the video here in the next video we're going to cover our last and final objective on development 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