PSYB65 Human Brain & Behaviour
Lecture 2 –Function of the cerebral hemispheres, brain vascular supply, cerebral ventricles, cerebral coverings
(Chapters 2, 14)
Monday, September 17, 2012
Today’s Lecture:
Organization and structure of the human brain, especially the cortex
Different lobes of the cerebral cortex
Function of the lobes and the functions within each lobe
Inner structure of the brain such as the ventricles
Outer structure surrounding the brain (meninges), which are the coverings of the brain
Blood supply of the brain
Introduction: Human Brain
As you move forward in the brain, the cortex is the newest evolutionarily
The cortex is NOT smooth for humans
There is some evolutionary pressure that wants humans to be
smart
The cortex moves back smooth and covers the whole brain
because there are no space , and it folds on itself; allthe cells
line the little grooves and this leads to mountains and valleys
(becomes NOT smooth) you can tell where each function
ends and begins
Basic Structure of the Brain
Sulcus/Sulci
o The valleys in the brain
o If there are huge (major one), it’s called fissure
Gyrus/Gyri
o The individual mountains in the brain
SULCI (valleys) and GYRUS (mountains)
o If you look at the top of the brain, the 2 sides of the
brain are not connected from the top view, but they
actually are connected
How the brain is divided
The brain is divided into two HEMISPHERES (right and left),
but they are not indentical
They are connected by a FIBER PATHWAY
The left controls the right and the rightcontrols the left
o Right hemisphere controls/receives information from the left side of
the body
o Left hemisphere controls/receives information from the right side of
the body
Example: person paralyzed on the right side due to brain
damage on the left hemisphere
Incorrect terms: Left Brain, Right Brain can be used, but NOT the official terms
to identify the left and right hemispheres
The Hemispheres
The two sides are divided by the longitudinal fissures which divide the two
hemispheres (left and right)
o Also known as longitudinal sulcus
The two hemispheres areconnected
SLIDE2: CORPUS CALLOSUM the fibres move from the left to the right side and vise versa
o Fibre pathway that connect the two hemispheres
o Send fibre pathway which cross over the corpus callosum
o Each part of the right hemisphere is connected to the adjacent (similar) part of the opposite hemisphere
o Example: right occipital lobe is connected to the left occipital lobe
o Excellent communication between each side of the hemispheres
The central portion of one side is connected to the similar side on the other
SULCI
There are 3 main SULCI when they are large they are called FISSURES.
o LONG TUDINAL fissure is from the right to left.
Seperates hemishpheres into left and right
o CENTRAL fissure (or central sulcus): divides the brain in half from front to back, divides frontal lobe from the
paritial lobe, anterior from posterior
o SYLIAN (or LATERAL): it separates the frontal and the parietal
Runs up the sideof the brain
Separates the temporal lobe
The Lobes within the Brain
Cerebral cortex divided into 4 lobes:
1. FRONTAL(in the front),
2. PARIETAL (behind the central sulci)(LOOK at the diagram,slide1),
3. OCCIPITAL(the very back),
4. TEMPORAL
Function of the Lobe
Each lobe has one main primary function and a primary cortex (a major function) and an association cortex within each lobe
In each lobe, it is divided into two types of cortex (tissue):
1. PRIMARY Cortex (for each lobe): is the primary receptive(receiving) info from the outside (hot,cold,etc etc)
o Responsible for performing basic input/out function
o It is the area that is responsible for the primary input/output function within that lobe
o Receives sensory information
Example: burn your finger and it processes what you do (move your finger away from the burning
sensation
Each lobe has primary receptors
2. ASSOCIATIONAL Cortex: processes the higher order computing, it is the newest (most recent) evolutionarily there
is a greater percentage of association cortex compared to primary cortex for humans and other primates. More
evolved species have more of cortex.
o Because people are trying to understand how the cortex works Brodmann’s numbers labels the functions
on the brain.
o Higher order functions, bigger than primary cortex
o More complex orders
o Each lobe has one associational cortex
o More recently evolved
o Thought processing part, whereas the primary cortex does basic input/output functions
o More evolved the organism, more associational cortex there is
o Higher percentage or ratio of associational cortex, much more intelligent
Example: humans have a small primary cortex and a huge associational cortex
Example: simple organisms such as frogs tend to have more primary cortex rather than associational
cortex because they can’t process much high order of thoughts or memory
MOTOR cortex (for each lobe): controls the muscles, the output go to nerve, and to muscle to your hand. MUSCLE
OUTPUT
o Sensory input motor output. Brodmann: Organizing the Brain using numbered mapped concept (slide 3)
Mapped the brain
Placed numbers on different parts of the brain
For example: the occipital lobe is area 17
Area 4 and 6 is the primary area of the frontal cortex
Area 3,1,2 stripe of the parietal lobe
Area 17: the occipital lobe the info from eyes comes here. 17 is
the primary area where the info from the eyes comes to
41: deals with hearing, the primary receptive area in the
temporal lobe, info from ears goes here
How did Brodmann number them? randomly
Lobes of the Brain
1. Frontal Lobe (Slide 4 above)
Primary function: primarily involved in motor (muscle) control; walk, type, turn your head .blink your eyes
o Involved in planning movements and inhibition of inappropriate behaviours
Associational cortex:
o Long term planning of movement (ie: go to university in order to get an education and get a decent job in the
future)
It starts at the most anterior part of the brain and it continues till the CENTRAL SULCUS (the division of the brain in
half; valley)the PRECENTRAL GYRUS’s primary function is that it controls motor movements
When you want to move your arm, it starts in the FRONTAL lobe
As you move more anterior in the frontal lobe, it is involved in planning you won’t be anywhere without your
frontal lobe
And inhibits inappropriate behaviours! OH SNAP.
The primary cortex is the PRIMARY MOTOR (get words out of your mouth; move, walk)
o STRIP(Broadmann’s area 4 and 6) it is located in the PRECENTRAL GYRUS(mountain) primary motor
strip of the primary cortex
All the stuff in front of that strip is the associational cortex (planning long-term
Primary cortex deals with how you move, walk/run, type, turn head, blink
Associational cortex deals with planning, inhibition of appropriate behaviour, long-term planning
The way the motor strip is organized is not random
o Slide 5: the blue strip is the motor striparea 4 and 6 As you move away from the motor cortex(dark
blue)(slide5)you move into the association cortex(lighter blue) the further you move away from the motor cortex(further anterior) it is higher in
function (more planning)
Motor Humunculous (Slide 6 below)
If you cut the strip if you stimulate close to the
central sulcus, it causes twitching of the foot
HUMUNCULOUS (little man) in the brain
Neurons in the different parts of the brain arrive at the
cortex at different times and they layer upon each
other
In the adult, the motor humunculous, if we take a slice
in the middle of the motor strip (left image) and you
bring it out and look at it (right image; corpus
callosum; connects other hemispheres),
The part that controls the feet, and if you go up the
brain, it’s the part that controls the knees, main torso,
then its the part that controls your arm (where the
neurons are found that control your arm), further
down its the neurons that control your hands (more
space devoted to the hands rather than the knees)
Side of the strips further down shows the part that
controls your mouth and
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