Lecture 6

Question 1

Encephalization factor -

Answer 1

Takes into account each class’s deviation from the slope of the ratio of brain weight to body weight for all species

Question 2

What brain region increases with brain size?

Answer 2

Cortex, not other regions

Question 3

In more recent evolution, there is an expansion of _____

Answer 3

Expansion of cortex, and neuron complexity

Question 4

Human brain evolution - Australopithecus

Answer 4

first appeared ~4 mil yrs ago
-bipedal (upright) hominids
-350-400 cm3 cerebral volume (size of chimp)
-made and used crude stone tools (chimps
use, but do not make, tools)
*Tool-making ability likely reduced selective pressure
for large jaws and teeth
*may also relate to increasing social tolerance

Question 5

Homo species

Answer 5

came within last 2 mil yrs (and brain volume seems to have reached a plateau during this time

Question 6

Homo habilis

Answer 6

had cerebral volume of 600-700 cm3

Question 7

Homo erectus

Answer 7

had cerebral volume of 7001400 cm3 (i.e., it expanded over a 1.5 mil year period)
-made elaborate stone tools, used fire, and killed large animals
-spread over three continents (i.e., from Africa  Asia, Europe)

Question 7

Homo sapiens

Answer 7

emerged ~150,000 yrs ago - 1400 cm3
cerebral volume

Question 8

Genotype

Answer 8

genes for traits contained within an individual

Question 9

Phenotype

Answer 9

physical characteristics

Question 10

The fertilized egg (zygote) develops
three layers…

Answer 10

1) Ectoderm is the outer layer that forms during gastrulation that becomes the nervous system ***Highlighted
2) Mesoderm – muscle, heart, red blood cells
3) Endoderm – lung, endocrine glands, pancreas

Question 10

During a developmental stage called
gastrulation….

Answer 10

the human CNS begins to form when the embryo is 2 wks old,
- The dorsal surface thickens forming a
neural tube surrounding a fluid filled
cavity
– The anterior end enlarges and
differentiates into the hindbrain, midbrain and forebrain
– The rest of the neural tube becomes the spinal cord

Question 11

The earliest events in development are orchestrated by _________ proteins that bind to DNA and broadly activate gene expression

Answer 11

Transcription Factors (TFs)

Question 11

Transcription Factors (TFs)

Answer 11

proteins that bind to DNA and broadly activate gene expression

Question 12

TFs orchestrate cascades of gene expression that allow for
_________ and creation of specific
tissue systems and cell types

Answer 12

segmentation (i.e., body plan)

Question 13

TFs play a fundamental role in early development, so they are ________ in __________

Answer 13

highly conserved in ALL vertebrates

Question 14

Homeotic proteins

Answer 14

Transcription factors involved in body plan determination (i.e.,segmentation); are highly conserved across evolution

Question 15

_____% protein sequence homology, mice and humans

Answer 15

95%, although the common ancestor for mice and humans is 90mil years ago

Question 16

6 Stages in neural development

Answer 16

1. Neurogenesis
2. Cell migration
3. Differentiation
4. Synaptogenesis
5. Neuronal cell death
6. Synaptic rearrangemen

Question 17

Cell migration

Answer 17

refers to the movement of the newly formed neurons and glia to their
eventual locations, there are 2
types: Radial and Tangential migration

Question 18

Neurogenesis

Answer 18

Cells on the inner side of the neural tube (ventricular zone - VZ) undergo cell division
- cells in the VZ provide the source from which all neurons and glial cells are derived,
- a combination of genetic and extracellular signals (especially transcription factors) determine which kind of cell is born

Question 19

Neurogenesis continues to occur in a more limited capacity in adulthood in several brain regions, which are……

Answer 19

1) olfactory bulb
2) granule neurons in the dentate gyrus of the hippocampal formation

Question 20

Radial migration

Answer 20

occurs on “scaffolding cells” – radial glia, from the ventricular zone toward the outer (pial) surface
– e.g., pyramidal neurons

Question 21

Differentiation

Answer 21

process of cells adopting their phenotype appropriate for the particular brain region

Question 21

Tangential migration

Answer 21

involves the movement of cells in the rostral-caudal axis of the CNS – e.g., cortical interneurons

Question 22

Neural cell adhesion molecules (NCAMs) –

Answer 22

are a class of chemicals expressed on the extracellular surface that guide cells and growing axons to their appropriate targets – There are many other molecules important for guiding neuronal processes to their correct location, NCAMs are just one example

Question 23

Growth cones

Answer 23

tips of growing axons; they contain finger-like extensions – **filopodia, at their tips that detect chemicals in the local environment as they navigate

Question 24

Molecules called _______ and ______ are chemical signals that attract or repel growth cones to enable guidance to their appropriate target neuron

Answer 24

chemoattractants and chemorepellent

Question 25

Synaptogenesis

Answer 25

refers to the formation of the synaptic connections between neurons during brain development

Question 26

Apoptosis –

Answer 26

programmed” mechanism (i.e., gene expression-dependent) for implementing cell death

Question 27

necrosis

Answer 27

the term used to describe cell death from injury or damage; necrosis usually occurs from trauma and/or disease)

Question 28

Postsynaptic targets provide ______ to extending axons

Answer 28

neurotrophins *Neurotrophins are necessary for presynaptic cells to survive; if they do not receive enough, then they die *Neurotrophins allow for matching between the size of target and the number of neurons with axonal efferents to the target region

Question 29

Nerve growth factor (NGF)

Answer 29

a neurotrophin secreted in target organs (e.g. muscle) in the peripheral nervous system

Question 30

Brain-derived neurotrophic factor (BDNF)

Answer 30

a key neurotrophin secreted by target neurons in the neocortex and hippocampus

Question 31

Synaptic rearrangement

Answer 31

describes the process whereby earlier formed synapses may be eliminated, while others are added

Question 32

Memories are made by....

Answer 32

refinement (i.e, both formation and elimination), and not just overall increase/decrease in synapses

Question 33

Gliogenesis

Answer 33

occurs throughout prenatal development concurrent with neurogenesis; it increases after birth in many animals, and continues throughout life

Question 34

Myelination

Answer 34

by contrast occurs primarily after birth -important for increasing AP conduction velocity – therefore, facilitates coordinated control of movements, and later on, for better cognitive functioning

Question 35

Behavioral teratology

Answer 35

study of how maternal environment influences nervous system development in the fetus - in this field, a major focus is drug exposure to the fetus

Question 36

Transgenic model

Answer 36

an animal (usually a mouse) with the artificial introduction or removal of a gene

Question 37

knockout (KO) –

Answer 37

a gene has been selectively inactivated

Question 38

Knock-in –

Answer 38

a new gene has been introduced

Question 39

Overexpression mutant –

Answer 39

increase expression of an existing gene by inserting extra copies of it into the DNA

Question 40

Conditonal KO/ transgenic

Answer 40

it's expression may be targeted to certain cell types in the body, or it's KO/ transgene is present in the DNA but it is not active until a desired time during development

Question 41

Epigenetics

Answer 41

The study of heritable changes in the individual caused by modifications in gene expression rather than alterations in the DNA itself - e.g., during early-life development (i.e., pre-/postnatally), experience can change the expression patterns of genes, and, in turn, behavior -this may have long-lasting consequence

Question 42

DNA methylation

Answer 42

chemical modification of parts of the genome; this usually prevents gene expression at that site

Question 43

histone modification –

Answer 43

alteration of histone proteins (i.e., proteins act as the “spool” for chromosomal DNA

Question 44

Histones may be _______ which makes the DNA more easily accessed to increase gene expression

Answer 44

acetylated – the addition of an acetyl group to the histone protein

Question 45

Autism spectrum disorders (ASD)

Answer 45

*Describes a class of disorders of neural development characterized by impaired social interaction and communication, and by restricted interests and repetitive behavior *Occurs by ~3 years of life - ASD is likely due to abnormal development of interneurons in the cerebral cortex, although the genetic mechanisms poorly understood

Question 46

Attention deficit/ hyperactivity Disorder (ADHD)

Answer 46

onset of ADHD by 7 yrs of life; 3-5% of all children are thought to have ADHD; 2-4 times more commonly diagnosed in boy