Basic structure of the nervous system.
the nervous system - central (central nervous system) and peripheral (peripheral nervous
central - brain and spinal cord.
peripheral - everything other than brain and spinal cord - the nerves in our body.
the brain is a continuation of the spinal cord - during evolution it looks like a tube - like a straw
brain and spinal cord - evolution and development - one end develops more than the other
gets more bumps - starts to look like another structure.
Basic components of the brain.
brain - starting from the most posterior part of the brain - closest to the spinal cord.....
2 major components:
basic life processes.
keeps heart beating, respiratory system going, etc.
cabbage at the base of the brain.
sensory and motor integration.
damage - can't walk upright etc
alcoholics - damages cerebellum.
there are different components to it.
reticular formation is in the midbrain.
the reticular formation - involved in sleep-wakefulness.
damage here might put you in a coma - no sleep wakefulness.
gunshot - makes reticular formation fire - you wake up really fast.
thalamus - relay station - relaying information to the cerebral cortex - all information stops here
for a while - relaying information from here - like Bell Canada.
hypothalamus - smaller, under thalamus - basic body functions - flight or fear - fighting -
feeding - the 4 Fs - flight, feeding, fighting, and sexual reproduction - also remember it as - if it
feels good - than it is probably in the hypothalamus.
In the forebrain.
The limbic system
emotion and emotionality. amygdala - involved in emotion, aggression, happiness, sadness
some people put hypothalamus here too - i.e. it has emotional aspect as well.
Notice that these don't keep you alive - but give you emotional repertoire - this is a network of
structures which are tied together.
Olfactory - in animals very important for everything - but in humans - we don't depend on smell
but limbic system still plays the role in everything to do with emotion and aggression and some
At the front - we see the cerebral cortex - or neocortex.
This is all forebrain
this neocortex - deals with higher brain functions.
this curls back and covers the rest of the brain&ldots; so in humans - cortex is huge.
dolphins seem more evolved than us - more convolutions, more weight to total body weight.
Evolution of the nervous system
brain in human is increased in size.
even rat brain is much bigger than turtle.
gets more bumps so it can do extra stuff.
one end started to develop more in higher guys.
the forebrain has started (even in fish) - to get larger relative to other parts of the brain.
since skull will not grow - the cortex gets pushed back and covers everything else.
only thing left is cerebellum.
also, behavioural repertoire of animal is correlated with brain parts.
i.e. there is a direct correlation between what the animal can do and what his brain parts look
if an animal depends on vision - that part of the brain - will be bigger
animals that deal with balance - i.e. birds - have larger areas of the brain that deal with that.
olfactory bulb - in rat - is quite large - because they deal with smell
our olfactory bulb is quite small.
so through evolution - forebrain gets larger - and those things that the organism does best - gets
the largest in their brain.
size of cortex is related to intelligent behaviour.
Development of the brain
phylogeny recapitulates ontogony.
your phylogenetic development - your development as a species
Ontogony - your development as an individual.
If you look at the way we development from conception to adulthood - it goes through the same
steps that we did as a species.
We get gill slits, mamillary organs, a tail - we get those as we start to develop - this is also seen in development of nervous system.
Like the primitive organisms - initially the nervous system looks like a tube - at 7 weeks - it is
more complicated but still very simple.
At 9 weeks - the forebrain in humans gets bigger and pushes everybody else away - it pushes
until its full - then it starts to convolute - this is done during phylogenetic and ontogenetic.
This cortex in human looks like its most of the brain - but remember this is the anterior structure
of the brain - it starts at the front - so if cortex is damaged - we have hit the most anterior and
thus most evolved structure of the brain - this is bad.
As organisms have developed - they have added on more parts - the most recent is always
So the most forward and thus most new in our brain - is the cortex - hence neocortex.
Triune brain theory. MacLeans
3 parts to brain functioning.
oldest portion of the brain - the reptilian brain - or the hind brain - or brain stem - i.e. the basic
core of the hind brain.
found in reptiles.
there to form basic life processes.
Next we added..
paleo mammalian brain
here he was referring to the limbic system (emotions)
i.e. we still have reptilian brain - we just added other things to it.
Finally we add..
this is the cerebral cortex
this lets us add the repertoire of intellectual behaviour.
read, write, language, study.
always remember - we don't lose those old brains - we just add some on.
Within every human there are 3 brains - paleo-mammalian, reptilian, neo-mammalian.
As the brain has evolved - primitive in brain stem - then more anterior - is more complex - so the
further up it goes up - the more complex but the less life threatening it becomes.
Always keep this in mind.
Stroke in cortex - call therapist
it has convolutions - not flat - it had mountains and valleys.
valleys - sulci - sulcus is singular
mountains - gyri - gyrus is singular.
top view - divided into left and right hemisphere. each side controls the contralateral side and gets its information from the contralateral side.
paralysis on the right side - damage to the left side.
some of indentations are quite large - large ones are fissures.
fissures divides the brain (cerebral cortex) into different lobes.
central sulcus (or fissure) - sylvian or lateral fissure - up the side of the brain.
longitudinal fissure - brain into right and left hemisphere.
the two hemisphere are connected - corpus callosum - large fibre band.
these large fissures divide the brain into different lobes - fronta is the most anterior. Parietal
lobe behind central sulcus. Occipital - posterior portion of the brain. Temporal lobe - base of brain
- separated from sylvian fissure.
divide the lobes not only because of their anatomy - but because each lobe has it's own
particular behavioural function.
frontal - motor behaviours.
parietal - sensations from the body. I.e. somatosensory. Soma means body. I.e. it is not vision -
vision is not somatosensory.
occipital - vision
temporal - auditory information. Important function in speech.
each lobe has it's primary function which is a basic function - then it does higher order things
each lobe has a primary area. Or we can say it has an area of primary cortex. Then there is
associational cortex or secondary areas.
primary areas do principle actions.
Brodmann's areas - each lobe is broken up into certain areas. He put numbers on the cortex.
frontal lobe - motor output - the primary motor area or strip - information goes out of the cortex
here - so guy can't move if problem here.
the rest is associational - they do much more complex things - they plan the motor movements -
they think about them in the future.
occipital - area 17 is for vision - putting shapes together and stuff is associational.
as we go through evolution - the more evolved - the more associational cortex there is. I.e. we
have more higher order complex things.
in human - most is associational.
moves until central sulcus.
this is the function of it's primary strip (the motor strip)
it's associational cortex is for planning of motor movement.
pre-central gyrus - easy to remember - we have a central sulcus - the little mountain in front of it
is a pre (in front) central gyrus - this is the primary motor strip in the brain - just anterior to the
the precentral gyrus is organized in a very specific manner. Brodmann's areas 4 and 6 are the
primary motor strip. I.e. it controls toes one by one in order then torso then fingers one by one -
so if you get a tumor - you know where his brain was hurt - you know it's opposite side - if his
foot can't move - I know it is frontal lobe at the top.
homunculus - little person - but a distorted view - it seems like the representation in the brain
isn't correlated with anatomy but with what we have more control over. I.e. if we need lots of
control over our mouth - it is bigger.
our fingers need a lot of control and so does our mouth and lips - so they are well repr