PSY290H5 Lecture Notes - Lecture 2: Myelencephalon, Mammillary Body, Globus Pallidus
PSY290 Lecture 2
Neuroanatomy
There are special features of our visual system that only would respond to faces
oTurns out it is not present in the visual cortex, not in the occipital lobe
Question: Do we have 1 thalamus in or brain, or do we have 2 thalami (one on each side)?
We have 2 thalami on each hemisphere
The Nervous System
Coordinates every aspect of how our body works: basic autonomic process (breathing and heart rate) to most
sophisticated responses and complex emotions
Gerald Edelman statement
oWhen we actually start to take a look of anatomy and localization of features, some of the basic
elements of coordination will become evident
oQuestion: what did Gerald Edelman say?
Gross (visible to the naked eye) versus microanatomy (visible under a microscope)
Brain Size Comparison
Human versus non-human species brain distinction
Human weighs 4 pounds (2% of body weight)
Human brain versus sheep brain
oDifference in size
oA sheep’s brain is a quarter of the size of the human brain
oOlfactory bulbs are on the down side of the brain
o“smaller brain because smaller animal” not true
a mature adult sheep weighs as much as a mature adult human female but nonetheless if we
compare something about the size of the brain, it’s not the size of the body that limits the size
of the brain. There is something else limiting the brain size. What is it?
Food/calories consumption (look below)
Sheep reach functional brain maturity an sexual maturity at 5 years whereas human
brain actually develops at 25 years. At 18, frontal lobes are refining themselves.
Question: What are the factors limiting brain size in sheep?
o“Advances in how we eat lead to the evolution of brain size”
Our brain consumes 20% of our metabolic needs toward the basic functioning of the brain
If the average adult needs 2000 calories, 400 calories go straight to help the brain function
The bigger your brain, the more calories you need
We do know that the sheep, to maintain all metabolic needs in any given day, need to spend 6-8 hrs each day
searching for food therefore their metabolic rate is not as high as a human
For every bit your brain grows, you need to consume more food
One of the advancements that allowed our brains to be as big as it is that we invented cooking techniques
oAdvances in how we eat lead to the evolution of brain size
Relative brain size of Mammals
1600 grams of brain for humans
most animals have a brain weight that bears some consistent relationship to their size
oline of best fit
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oif we know their body weight we can predict their brains size
othe biggest mammals, the blue whale, have a massive brain (10,000 grams)
othe smallest mammals, moles, have a brain that weights 0.1 grams
osome dots are above and below line of best fit
line and any dot: residual
“modern humans have the biggest residual of any single animal”
for our body size, we have a brain that is significantly larger in relation to our body
weight
oIn some ways, we can say a blue whale is the smartest due to size.
oCome up with an answer that can account for the blue whale’s size regardless that we’re smarter
We can discuss the basic functions such as thinking and feeling
The Central and Peripheral Nervous System
The blue whale would have a massive PNS which is the parts outside the brain and spinal cord
It’s our PNS that contains motor and sensory nerves
oThis determines the size of the brain for most animals
When we look at humans, there is something different, human brains are disproportionally bigger than
our body size which means we would use it differently than other mammals
o“This disproportion less highlights complexity”
On the surface: bumps and spaces (sulci)
Fissure: a bigger sulcus (divide larger areas – 2 hemispheres)
Gyri
Sulci
Central Sulcus
Sensory Strip
All these gyri and sulci are clever solutions to a clever problem: What is it?
Cats and rats have less sulci and gyri
oRates have a very few indications
One of the reasons why we have more bumps: the bigger our brain is, the bigger our skull must be and this
hinders the birth process which can result in the death of mother and daughter
It is hypothesized that the evolutionary solution of creating animals with bigger brains is that we need
a brain that has kinks and folds that allow you to have a much bigger surface area without drastically
increasing the volume of the brain.
oIn the picture on slide, if we extend the brain, it would fill just a little more than the grey square
oThe surface of the brain is only 1/3 of the cortex and 2/3 of the brain is stuck inside the folds
We do know that there are links between the size of the brain and intelligence but we need a way to account
for the body size thing
oIt turns out that the best way to distinguish brain size and intelligence is to look at proportion
of different brain areas (the cerebrum and the brain-stem)
o“lizard brain” when we think about a roughly primitive brain with basic features: lizard
ocrocodile: have all basic elements [cerebrum (executive functioning of the brain, decision making,
processing, emotional responses), brain stem (regulates all autonomic functions)..]
oa lizard has all the basic elements there but the part that does the thinking is small (cerebrum is small)
owhat seems to be different from humans: humans have a relatively speaking a much larger
cerebrum than they do a brain-stem
oone way we can capture an estimate of intelligence is by creating a ratio of the cerebrum to the brain
stem: executive brain ratio cerebrum / brain stem
therefore, it does not matter how much an animal weighs
“The Executive Brain Ratio” is positively correlated with intelligence
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Similarities
there is a lot of similarity that can be drawn when we start to take a look at the midline of the brain
the midline region is identical
the big white band: corpus callosum major connecting pathway between hemispheres
pineal body
our brain is covered by layers of sheath: tough fibrous piece of covering dura mater
oinside is a fluid that circulates cerebral spinal fluid
odura mater is Latin for “tough mother”
oour brain also has a pia mater: literally stuck like skin to the brain and you could peel it back
o3rd kind of mater: arachnoid connects the pea to the dura like spider webs
o3 types of maters
dura mater
pia mater
arachnoid
Global Terms
anterior: front of
posterior: back of
dorsal: extends through the back (original name for 4-legged animals)
ventral: part that is underneath
medial: toward midline
lateral: toward the outsides
Local Terms
when I look at a single part of the brain, I may be interested in saying something like “gyri that sits on the top
surface of the temporal lobe” = this is on the lateral side of the brain
however, it is not very accurate because global language is hard to determine local points
we use “caudal” Latin term for tail/ at the back of something
“rostral”
The inferior part are closer to the ventral side of the brain or superior is closer to the dorsal side
Fissure: major sulcus
Fissure between temporal lobe
Frontal and parietal lobe
Extends between cerebellum and cerebrum
Finding our Way in the Nervous System
If two things are found on the same side of the brain Ipsilateral
oBroca and Wernicke area are ipsilateral to one another (both found on the left)
If two things are found on the opposite side of the brain Contralateral
X-line feature: optic nerve extend to the eye/ cross over is so obvious that it looks like a big X
oProjections that a sheep left eye will cross to the right visual cortex
oThe information is sent to the contralateral side
o“cross over” point decussation: cross midline
oOptic Chiasm: point of cross over
oCorpus Callosum: connects left and right hemispheres
oProximal: close to point of reference
oInfundibulum
oPituitary gland: hands from bottom of the brain, circular in shape
oEarly anatomists used to think the pituitary is connected to the nose
Pituita is the Latin for mucus
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Document Summary
There are special features of our visual system that only would respond to faces: turns out it is not present in the visual cortex, not in the occipital lobe. We have 2 thalami on each hemisphere. Coordinates every aspect of how our body works: basic autonomic process (breathing and heart rate) to most sophisticated responses and complex emotions. Gross (visible to the naked eye) versus microanatomy (visible under a microscope) Human weighs 4 pounds (2% of body weight) There is something else limiting the brain size. Sheep reach functional brain maturity an sexual maturity at 5 years whereas human brain actually develops at 25 years. Question: what are the factors limiting brain size in sheep: advances in how we eat lead to the evolution of brain size . Our brain consumes 20% of our metabolic needs toward the basic functioning of the brain. If the average adult needs 2000 calories, 400 calories go straight to help the brain function.
