Comprehensive Overview of Brain and Spinal Cord Functions

the topic of this lecture is the brain and spinal cord so let's start by talking about the

brain so the surface of the brain is wrinkled there are all of these kind of bumps or folds called gyri and there are

sulcai which are the grooves so if we look over here we can see gyri are going to be these kind of uh the bumps that

stick out the sulcai are going to be the wrinkles the grooves that go in a deep sulcus is called a fissure such

as the longitudinal fissure that divides the brain into the left and right hemispheres right so there's a deep

fissure along the center of our brain going back that separates the brain into two halves the right and left hemisphere

these cerebral hemispheres are connected by the corpus callosum so one of the things that's important to

know about the two hemispheres is that there's this concept of lateralization What lateralization refers to is that

each hemisphere of the brain is associated with specialized functions for example the left hemisphere of the

brain is going to control the right side of the body and it's also going to be associated with things connected with

verbal processing language speech reading writing those sorts of things the right hemisphere in contrast

controls the left side of the body and it's also associated with things like non-verbal sorts of processing spatial

processing musical processing visual recognition those sorts of things this is an illustration that's an

oversimplification of the way that here hemispheric specialization works right so you can see here from a kind of top

down view looking down on someone's brain the left hemisphere is responsible for things like right hand touch things

like math language science writing logic those things tend to be taken care of by the left hemisphere now there's a

there's a lot of complexity of this we'll talk about later so it isn't the case that all everything we know about

science is in the left hemisphere it the the brain isn't quite that simple the right hemisphere is responsible for

things like left hand touch music appreciation art appreciation dance perception fantasy sculpture those sorts

of things and the two hemispheres are connected by the corpus callosum right this thick band of fibers neurons that

collect that connect the right and left hemispheres now again this is a an

oversimplification meaning that even though sometimes people will talk about things being I'm a left hemisphere or

left brain sort of person or a right brain sort of person really both hemispheres are are involved in many of

these processes working oftentimes in slightly complementary ways we'll talk about more as we move through this

lecture we also can think about dividing the brain in different ways as far as there

being three main categories the first of these main categories is the forebrain followed by the midbrain so the

forebrain is here the midbrain here and the hind brain this part down here so let's go through each of these three

primary parts of the brain and again there would be a forebrain midbrain and hindbrain for both hemispheres and so

what we'll do is we'll kind of work through and we'll talk about these areas of the brain one at a time so let's

start with the foreground so the forebrain is going to be the largest part of the brain and it

contains cerebral cortex which is uh associated with higher level processes and in a moment we'll spend a fair bit

of time going through the cerebral cortex in more detail the forebrain also has Thalamus which is

responsible for kind of it's essentially kind of a sensory relay station it also contains the hypothalamus which

is responsible for maintaining homeostasis within the body it contains the pituitary gland which is

a master gland of the endocrine system basically it controls the endocrine system or hormonal system

and the forebrain also contains the limbic system which is associated with emotion and memory

so let's go into more detail about the cerebral cortex the cerebral cortex is going to be that outer part of the brain

that we were looking at earlier the surface of the brain and it's associated with some of our highest mental

capabilities things like our sense of Consciousness our ability to think the emotions we experience our ability to

reason to use language in our memory the cerebral cortex can be broken up into four lobes each of these lobes has

a slightly different function so if we start here at the front of the brain we can talk about the frontal lobe

which is associated with things like cognition recent memories uh planning some aspects of emotion

we have the parietal lobe here which is going to be associated with bodily sensation the occipital lobe here at the

back of the brain which is primarily responsible for vision and then we have the temporal lobe here behind the temple

that's responsible for our sense of hearing as well as some types of advanced visual processing

so let's start by going into more detail about each of these four lobes so let's begin with the frontal lobe so the

frontal lobe is involved in executive functioning our ability to plan to organize to engage in making judgments

to attend to things to reason it also is implicated in things like our motor control our emotion and our ability to

produce language the frontal lobe contains the motor cortex which is a strip of Cortex that's

involved in planning and coordinating our movements it contains the prefrontal cortex as

part of the brain right here behind our foreheads that's responsible for higher level cognitive functioning

it also contains Broca's area which is a region in the left hemisphere That's essential for a language production

right our ability to create languages if we suffer some sort of damage to Broca's area this can lead to

difficulties in producing language so for example if you had a tumor or a stroke right that impacted Broca's area

it could impair your ability to generate language since we're talking about the frontal

lobe I want to spend a few minutes talking about a really famous uh case involving damage to the frontal lobe

this is about a gentleman named Phineas Gage who was a railroad foreman and an 1848 he was uh he was part of an

accident where he was using these camping rods basically to shoot metal rods down into the ground until a

railroad tracks there was a misfire with the device he was using to fire these railroad spikes down and instead the uh

the iron Rod went through his head basically it kind as you can see in the image over here it went in uh kind of

behind his uh jaw and went out through the top of his head basically it created this hole right through his brain

and it damaged his frontal lobe after the accident people noticed that Phineas Phineas Gage's behaviors and personality

had changed before the accident he was very well mannered he was relatively soft-spoken after the accident he

started behaving in odd and inappropriate ways um and the idea is that what we think

happened with the case of Phineas Gage is that parts of the frontal lobe that are associated with our ability to

control our impulses was damaged so severely by this accident that it changed his personality now things don't

have people can suffer damage to the frontal lobe through other means it doesn't have to be this sort of uh

horrible uh railroad accident you could have a stroke or a tumor for example or some sort of concussion impact that

could damage the frontal lobe and could lead to similar sorts of impairments in our ability to control our impulses

next up is the parietal lobe the parietal lobe is going to be involved in processing various sensory and

perceptual types of information it's going to contain the primary somatosensory cortex this is going to be

essential for processing sensory information from across the body our feelings of touch temperature and pain

for example the parietal lobe is going to be organized topographically so for example if we look at this image here

we've got sensory cortex area as well as motor cortex area and if you'll notice that each part of this cortex area right

the outer part of the brain is going to correspond to a particular part of the body so for example in the sensory

cortex area over here by the way there's left and right motor and sensory cortex I just have them next to each other for

ease of presentation but we have things like for example parts of our cortex area here will be

associated with our uh with our sensories uh information coming in from the leg and the genitals the hips the

trunks the arms elbow forearm hand fingers and forefinger also notice that the sizes of these body parts differ the

reason for that is the kind of that sort of deformation of the the body parts is due to how much cortex area is devoted

to each of them right now notice that here our feet for example is taking up relatively small amounts of Cortex

relative to our hands the reason is that the sensory information coming in through our hands is much much richer

right than what we're receiving from our feet right it doesn't mean that we're completely immune to sin's sensation

through our feet it just means that we have we have far more nerve endings in our fingers and in our hands because we

typically manipulate the environment using our hands rather than our our feet we then have areas dedicated to sensory

information from our eyes nose face slips Jaws teeth gums and tongue we also have motor cortex area associated with

our ability to move these different parts of the body our toes our knees our hips our trunk shoulder arms elbow wrist

hand fingers thumb neck brow face lips tongue jaw and our planets so all of these areas of the brain are organized

topographically basically parts of the body that are closer together right physically closer together also tend to

be close more closely associated in terms of where they're located in the cortex area

next up is the temporal lobe the area of the brain directly behind the temple so this is associated with hearing memory

emotions some aspects of language we also mentioned previously there are some parts of really kind of advanced visual

processing take place in the temporal lobe as well so this is going to contain the auditory

cortex a strip of Cortex in the temporal lobe that's responsible for processing auditory information so our sense of

hearing for example uh we this part of the brain is also going to contain vernix area which is

important for speech comprehension right so up here we can see vernix area which is about speech comprehension and it's

going to play a complementary role to Broca's area from the frontal lobe which is important for speech production right

so damage to one or both of these areas can impair speech damage to Broca's area can make it difficult for us to produce

speech damage to vernix area can make it difficult for us to actually comprehend speech

next is the occipital lobe the occipital lobe is associated with visual processing the occipital lobe is back

here at the back of the head um it's going to contain the primary visual cortex which is responsible for

interpreting incoming visual information uh the the occipital lobe is going to be organized retinopically which is going

to be uh where the neurons with receptive fields that are closer together in the visual space have cell

bodies that are closer together in the cortex so this is going to be in a way kind of similar to the topographical

organization we saw in the parietal lobe but instead of being about different parts of the body instead it's going to

be about the visual field right so the brain is organized in a way that it's trying to make sense of of the neuron

the neurons are organized in such a way that it's going to correspond to what it's dealing with in this case it's

dealing with information coming in through the retina the second brain structure after the

forebrain is going to be the midbrain so the midbrain contains the reticular formation which is going to be

associated with regulation of sleep wake Cycles arousal alertness and motor activity

the midbrain also contains something called the substantia which is going to be responsible for reducing

dopamine partly responsible for producing dopamine and it's involved in our control of movement

the midbrain also contains the ventral tegmental area the BTA which also is going to produce dopamine and is

associated with mood report and addiction processes when we see a degeneration of the

substantia and the VTA that's going to be involved with Parkinson's disease and here we can see part of the

midbrain here where the substantia are and the VTA next up is the hindbrain the hindbrain

consists of the medulla the pons and the cerebellum so the medulla controls automated processes like our breathing

our blood pressure and our heart rate like these things again are taking are being controlled automatically we don't

have to devote uh energy and thought and resources to breathing blood pressure and heart rate our body is doing that

for us through the medulla the pons connects the brain and the spinal cord it's involved in regulating

brain activity during sleep and the cerebellum it controls our balance coordination movement motor

skills and it's thought to be an important plain important role in processing some types of memory

so together these three structures are known as the brain stem so now let's move through the brain some

of its major major structures and some of their functions so let's begin by talking about the

Corpus glossum we've already mentioned the corpus callosum but let's spend a little bit more time going into a tiny

bit more detail so the corpus callosum is only a bridge of fibers neurons the passes information

between the two cerebral hemispheres basically the corpus callosum allows the right hemisphere in the left hemisphere

to communicate with each other which is going to be really vital because the two hemispheres are going to be playing

slightly different roles in a number of processes so for example when we see an object in the environment and we want to

recognize it and then be able to give it a verbal label but we really need both hemispheres working together and it's

going to do that through the corpus callosum next is the thalamus this is going to be

a relay Center for incoming sensory information right we've mentioned the the thalamus earlier

the cerebrum is going to be this large part of the external area of the brain that kind of wrinkled area is going to

be involved in things like sensing thinking learning emotion Consciousness and voluntary movement

the amygdala is going to be a limbic system structure and it's going to be involved in emotion and aggression

the hippocampus is also a limbic system structure and it's involved in learning and memory

the cerebellum which we just spoke about a moment ago is going to coordinate fine muscle movement and balance so for

example if someone suffered damage to the cerebellum that may have it may lead to may have implications for their

ability to control their fine motor skills or maintain their balance the brain stem area is the most ancient

part of the brain it determines our alertness and regulates basic survival functions things like our ability to

breathe heartbeat blood pressure those sorts of things so for example if if someone was in a

really uh nasty car accident they could suffer brain brain damage to many areas of the brain that may have tremendous

impact on their ability to function but if the brain stem is intact it's possible that they may still be able to

survive despite the damage to other areas of the brain now again their survival may be in a comatose state in

some cases but if the brain stem is intact right it's possible right that the organism can continue to survive

even if other parts of the brain are fairly severely damaged however if the brain stem is damaged

there's a very very very high probability that the organism is going to cease to survive

the spinal cord is going to be the next part of the central nervous system we'll spend some time talking about in just a

little bit it's going to transmit information between the brain and the rest of the body and it's going to

handle some simple reflexes next is the reticular formation this is going to be a group of fibers that carry

stimulation related to sleep and arousal through the brain stem next is the medulla it's going to

regulate vital functions such as our breathing and circulation the puns is involved in sleep and

arousal we also have pituitary gland which serves as the master gland that

regulates the other endocrine glands and finally the hypothalamus the hypothalamus is going to be responsible

for regulating our basic biological needs like our hunger thirst and temperature control so for example if if

you had a tumor on your hypothalamus depending on the nature of the tumor and location and those sorts of things it

could lead to problems and regulation of these basic biological needs for example depending on the placement and type of

tumor it could lead to a feeling of a lack of satiation where the individual is always hungry they never feel full

for example and that's because of that's one of the roles of the hypothalamus is kind of regulating those basic

biological needs like like hunger now even though we we talked about the location of each of these uh brain

structures for for the purpose of quizzes and exams I I won't be giving you like a diagram of the brain and

asking you with an arrow point and pointing the word one part of the brain saying what structure is this so I won't

be asking those sorts of questions I just wanted you to see what the brain looks like and where the different parts

are located mainly for your own information now things like what each part is responsible for

um that would I would consider that to be fair game there all are also some questions that

are so um that aren't terribly specific like knowing for example like the cerebrum is the outer part of the the

wrinkly part of the brain I would consider that to be fair game um now would I necessarily ask a

question about I don't know like uh where is the where is the thalamus located I I don't know if it would get

exactly that that specific but asking about the function served by the thalamus that that would be fair game

okay and here's an image of an actual cross-section of a brain so you can get a sense of what what the brain

structures actually look like we briefly want to mention the idea of brain plasticity

um it was believed at one time that significant changes in the brain only occurred very early in development uh

for example When I Was An undergraduate taking intro psychology this was still the most common belief is that

the brain wasn't terribly plastic that most of the major changes that happened in the brain structure happened really

really early in development in intervening decades it's become a little clearer that the brain is more

plastic or malleable than we used to believe so aspects of our experience can

actually sculpt features of our brain structure right things can be shaped by our experience

also if there's damage to incoming sensory Pathways or certain areas of brain tissue or are damaged this can

lead to neural reorganization basically adjacent parts of the brain may take over the functions that were that would

normally be held or taken care of by other nearby parts of the brain right so basically our brain can reorganize

within within certain within pretty strong limitations right now younger individuals typically have a better

chance of experiencing this sort of neural reorganization right so damage earlier in life it's a little bit easier

for the brain to reorganize and work around those sorts of damaged areas however even an adult ring can generate

new neurons this idea of something called neurogenesis right so it isn't the case that once a neuron is is gone

that it can never be replaced right we can generate new neurons it doesn't work nearly as efficiently as what we see

with for example our skin cells which we're constantly growing in these skin cells neurons are are more precious and

don't don't gen don't uh regenerate nearly as as quickly as what we see with skin cells

we also want to spend a bit of time talking about different brain Imaging techniques

so how do we see what's going on inside of the brain so there are some techniques that we're going to talk to

that involve radiation so we'll talk about computerized tomography CT scans we'll also briefly mention positron

emission tomography pet scans some techniques are going to involve the manipulation of magnetic fields so we'll

talk about magnetic resonance imaging MRIs we'll talk about functional magnetic resonance imaging fmris and

then the last type of Imaging technique will be a technique that uses electrical activity and this is going to be

electroencephalography and EEG so let's start the CT scan okay so it's CT scan what it involves

are a series of x-rays that are that are taken of the brain that create an image of the brain but as as the x-rays are

passing through different densities of tissue within the brain it can reveal structural issues so for example a CT

scan can reveal a brain tumor right so if we look up here at this structural issue of the CT scan right we can see

this issue here which is the formation of a tumor right so CT scans can be very helpful for looking at structural kinds

of issues CT scans are fairly readily available at hospitals and some medical providers outside of hospitals they're

relatively cheap which is a nice thing because some of these other scams can be fairly uh cost intensive

a positron emission tomography scan a pet scan involves injecting individuals with a mildly radioactive substance and

then monitoring changes in blood flow to different regions of the brain a pet scan is really helpful for showing

activity right so it can show functional issues right a CT scan is great for structure right for example if you were

involved in I I saw a CT scan one to someone who had been a construction worker who was involved in an accident

where a nail had been fired through his skull right and a CT scan could reveal where the nail uh had what part of the

brain had been damaged by the nail right so that's a structural issue a pet scan can identify functional issues

basically which areas of the brain are active during certain types of tasks right

next up are MRIs and fmris so an MRI is going to use a magnetic field to get a picture of the tissue that's being

imaged right so an MRI can give you structural information right similar to a CT scan but more detailed in in some

ways and fmri in contrast can show you changes of metabolic activity over time

so for example up here we can see an fmri scan showing activity in the brain over time so if we were interested in

answering a question such as what areas of the brain are associated with solving complex mathematical procedures right we

could put someone into an fmri we could then ask them to work on some sort of mathematical task and we could image

their brain while they're working on the task and we could see which areas of the brain were lighting up and when we talk

about lighting up what we're talking about is we're identifying changes of metabolic activities and when an area of

the brain lights up on an fmri what we're saying is this part of the brain is going to be actively engaged right so

we can see which parts of the brain were more or less actively engaged during different sorts of tasks like solving a

math problem looking at a face with someone that you recognize looking at the face of a stranger right other sorts

of cognitive tasks we also have electroencephalography and EEG this is

going to involve recording the electrical activity of the brain of the brain via electrodes that are placed on

the scalp so using caps with electrodes like the one uh one worn here by this young child you can see what areas of

the brain are most active at what times by tracking the amplitude and the frequency of brain waves

so where these electrical signals are coming from is if you think back when we were talking about neural Transmissions

we were talking about those as being electrochemical processes and so the small amounts of electricity that are

being generated by a neuron right is that is that activity as that action control is kind of flowing down the axon

for example right those things can be identified by these by these uh by these eegs right these electrodes on the scalp

can be sensitive enough to detect these small changes right in electrical current in areas of the brain right so

what eegs can tell you basically is which areas of the brain tend to be active at what times which can be really

helpful if you're doing something like for example uh the the child in the image here

what he's being asked to is make some sort of decision about these different objects on the screen and so what can

happen is as he's making his decision right certain areas of the brain may be more or less active right and the EEG

can detect which areas of the brain are active right now again this isn't going to be as fine-tuned as what you can get

with something like an fmri but AEG is much easier much less invasive and intensive and much less costly to

administer as well finally we want to return to the spinal cord right we've mentioned the spinal

cord in a previous lecture but I just want to make sure that we remind ourselves since it's the second part of

the central nervous system so what the spinal cord is responsible for doing is it's delivering messages to

and from the brain basically it's serving as kind of this information Highway between the brain and the rest

of the body sending information from the brain to the rest of the body things like motor issues if if the brain wants

the right arm to move and grab bottle of water right that information is being transmitted via the spinal cord also

incoming information for example if you are touching something hot right that information travels to the spinal cord

then makes its way up to the brain as we've talked about the spinal cord has its own system of reflexes so if we

experience pain if we touch something hot or something sharp when that information travels along the fingertip

to the arm as it eventually makes its way to the spinal cord as it begins to make its way up to the brain there's

also going to be a reflex-like action where the spinal cord is going to send information back causing the hand to

retract from that painful stimulus right that's that sort of reflex-like response it isn't something that the brain is

telling the the arm to move rather it's happening before the brain can even process the information

the top of the spinal cord is going to merge with the brain stem and the spinal cord is going to end just below the ribs

the spinal cord is going to be organized in the 30 segments each of these segments is connected to a specific part

of the body through the peripheral nervous system these sensory nerves are going to bring

messages in and up to the brain and motor nerves are going to send messages out to the muscles and the organs and

again as we've mentioned in moments of survival automatic reflexes are going to allow motor commands to be initiated

without sending signals from sensory nerves to the brain first right allowing for very quick reactions like you touch

something hot in order to minimize the amount of damage that your body is going this is going to suffer your your spinal

cord it can actually send a reflex like Behavior causing you to jerk your hand back from whatever the painful stimulus

is if we take a look here at this image so we see the brain here the spinal cord

going down this way the spinal cord is going to be it's going to be embedded within the spinal column so we can see

the vertebrae around the spinal cord or this around the spinal cord and we can see the different kind of uh separations

along the spinal column