Intro to Brain Anatomy

Question 1

Central Nervous System (CNS)

Answer 1

Brain and spinal cord

Question 2

Peripheral Nervous System (PNS)

Answer 2

All parts of the nervous system outside of the brain and spinal cord

Question 3

Two components of the brain

Answer 3

1. Grey matter

2. White matter

Question 4

Grey matter

Answer 4

what makes it grey?

Density of the cell bodies of the neurons

Question 5

White matter

Answer 5

the axons of the neurons
-what makes it white?
The myelin sheath –> a fatty substance to enhance
conduction of the electrical signal down the axon

Question 6

cerebral cortex

Answer 6

the seat of higher cognitive processes
• Technically a continuous sheet of tissue, but it is not
homogenous –> cytoarchitectonic areas
• The cerebral cortex has expanded immensely over
evolution. The human cortex is the most convoluted
of any primate brain!
• Folded into: sulci (the valleys), gyri (the hills), and
fissures (deeper valleys)

Question 7

Subcortical structures

Answer 7

more primitive controls than cerebral cortex (e.g., breathing, heart rate, alertness, etc.)

Question 8

Mapping cortical folds – early studies

Answer 8

• Mapping cortical folds started in the 19th century when it became possible to harden brain tissue using alcohol.
  • These early studies demonstrated relatively consistent patterns across individuals
  • Certain correlations with functional processes
• limited to post-mortem specimens. This meant mainly surface analysis and a restricted sample size!

Question 9

Mapping cortical morphology – recent advances

Answer 9

• With the advent of neuroimaging tools, it became possible to study the cortical folds of many subjects (who were alive!) in 3D.
• Using Magnetic Resonance Imaging (MRI), one can follow a sulcus on the surface of the cortex to its depth
• Can make use of a standard space

Question 10

Frontal Lobe

Answer 10

• Voluntary motor control
• Working memory functions (monitoring/tracking
information, selective attention, active memory retrieval)
• Broca’s area for speech production

Question 11

Parietal Lobe

Answer 11

• Somatosensory processing
• Dorsal stream of vision - “where” pathway
• Reading functions
• Writing functions

Question 12

Occipital Lobe

Answer 12

Visual processing

Question 13

Temporal Lobe

Answer 13

• Auditory processing
• Wernicke’s area for language comprehension
• Ventral stream of vision – “what” pathway
• Smell processing (medial side)
• Memory consolidation (medial side)

Question 14

Penfield’s stimulations

Answer 14

• Dr. Wilder Penfield stimulated these areas using
electrodes directly on the cortex during awake
surgery:
-precentral gyrus = motor cortex (“M1”)
-postcentral gyrus = somatosensory cortex (“S1”)
• Mapped the somatotopic organization of these gyri –>
motor and somatosensory homunculi

Question 15

Paracentral lobule

Answer 15

• motor and somatosensory processing of the foot
  • Dr. Penfield then discovered a totally different motor homunculus on the medial surface of the
  frontal lobe that he referred to as “M2” or the Supplementary Motor Area (SMA)

Question 16

Hippocampus

Answer 16

• technically only one layer of neurons

- aka archicortex (first cortex)

Question 17

Limbic cortex

Answer 17

• Phylogenetically old cortex
• Used to be called the “limbic lobe”
- limbus = ring

Question 18

Insula

Answer 18

• Insula –> “island”, sometimes referred to as it’s
own lobe
• Found within the Sylvian Fissure – cannot see
from the lateral view itself because covered by
the frontal, parietal, and temporal opercula
• Has a central sulcus
• 3 short gyri: motor processing
• 2 long gyri: somatosensory processing
• Notice how it sits under the pre and postcentral gyri
of the lateral surface

Question 19

anterior commissure

Answer 19

Communication of the cortex of the anterior temporal lobes

Question 20

Occipito-frontal fasciculus

Answer 20

connects frontal and occipital lobes

Question 21

Superior longitudinal fasciculus

Answer 21

connects frontal with parietal lobes

Question 22

Arcuate fasciculus

Answer 22

connects lateral PFC with lateral posterior temporal lobes

Question 23

Inferior longitudinal fasciculus

Answer 23

connects temporal and occipital lobes

Question 24

Temperal-frontal extreme capsule fasciculus

Answer 24

lateral mid-temporal with lateral frontal cortex, part of the
extreme capsule

Question 25

Uncinate fasciculus

Answer 25

orbitofrontal cortex and temporal poles

Question 26

traditional language pathway

Answer 26

Norman Geschwind, 1970’s Boston –>
aphasiologist who emphasized the importance of the arcuate fasciculus to connect Broca’s area and Wernicke’s area in the language dominant hemisphere

Question 27

Subcortical structures

Answer 27

Thalamus, striatum, basal ganglia

Question 28

Thalamus

Answer 28

“grand central station”, consists of many

nuclei that regulate different types of information

Question 29

Striatum

Answer 29

Putamen, Caudate Nucleus, Globus Pallidus

“pale globe”

Question 30

Putamen and Caudate Nucleus

Answer 30

neostriatum

Question 31

Globus Pallidus

Answer 31

paleostriatum

Question 32

Basal ganglia

Answer 32

includes the striatum and amygdala and nucleus accumbens, and other structures important for motor learning and procedural memory

Question 33

White matter connectivity

Answer 33

1. cortico-cortical connections: connect one
   area of cortex to another, either
   • Within the same hemisphere - association
   fibres (e.g., arcuate fasciculus)
   • Between hemispheres - commissural fibres
   (e.g., corpus callosum)
2. cortico-subcortical connections: also referred to as projection fibres

Question 34

External capsule

Answer 34

motor cortex primarily to putamen (uni-directional)

Question 35

Internal capsule

Answer 35

a massive white matter highway connecting subcortex (e.g., thalamic nuclei) to cortex and vice versa, i.e. bidirectional

Question 36

Cortical cytoarchitecture – early studies

Answer 36

By hardening a brain using alcohol, one could section the tissue very thinly and stain the tissue for microscopic analysis.
• It became obvious that the cortex is not a homogeneous sheet of tissue, but rather can be subdivided based on its cytoarchitecture (“cyto” = cell; “architecture” = structure).

Question 37

Golgi stain

Answer 37

• only stains about 10% of neurons but you can see the entire morphology of the neuron
• The Golgi stain is what Ramon y Cajal perfected and how he was able to demonstrate that the neuron is the individual unit of the brain. Generated beautiful illustrations of neurons using this stain

Question 38

Nissl stain

Answer 38

stains the cell bodies of all neurons – great for cytoarchitecture studies because can determine cell densities

Question 39

Weigert stain

Answer 39

stains the axons, i.e. the white matter (myelo-architecture)

Question 40

Neocortex can be divided into how many layers?

Answer 40

6

Question 41

2 main types of neurons in cortex

Answer 41

Pyramidal neurons – soma is shaped like a pyramid. These neurons have basal dendrites, an apical
dendrite, and a long axon that exits the cortex to
form the white matter. They are the typical cortical
neuron.
Granule/stellate neurons – much smaller, rounder
cells. Axons usually do not leave the cortex
(intrinsic) as they mainly distribute information to
neighbouring layers.