Week 1 Lectures Flashcards
Name the brain orientation of the top part of the brain.
Dorsal/Superior
Name the brain orientation of the bottom part of the brain.
Ventral/Inferior
Name the brain orientation of the front side of the brain.
Rostral/Anterior
Name the brain orientation of the back part of the brain.
Caudal/Posterior
What is the name of the top part of the longitudinal axis of the brainstem and spinal cord?
Dorsal
What is the name of bottom part of the longitudinal axis of the brainstem and spinal cord?
Ventral
What is the name of the back part of the longitudinal axis of the brainstem and spinal cord?
Caudal
Name the orientation of the brain if you were to cut off the top part of the brain.
Horizontal/Axial/Transverse
Define midline
Directly in the middle of the brain in between the two hemispheres.
- relative to something
Define lateral
Directly to the side of whatever structure you are describing towards the outside of the brain, away from the midline
Name the brain orientation when you take a section down the middle or to the sides?
Sagittal, Midsagittal, Parasagittal
Midsagittal
directly down the center
Parasagittal
parallel to sagittal plane
Are sagittal sections always right on the middle between the hemispheres?
No, they can be lateral to the midline (parasagittal)
Name the brain orientation associated with making slices of the brain starting on the rostral side and taking the sections all the way back to the anterior.
Coronal
Coronal
perpendicular to sagittal plane
Define ipsilateral
on the same side of the body
Define contralateral
on the opposite side of the body
Are the sensory and motor cortex that control perception and movement ipsilateral or contralateral?
Contralateral
What is the human nervous system composed of?
Central nervous system (CNS) and peripheral nervous system (PNS)
What makes up the CNS?
Brain and spinal cord
What makes up the PNS
Cranial (12 pairs) and spinal nerves (31 pairs)
What are the structures that make up the brain (name 4)?
- Cerebrum
- Forebrain
- Cerebellum
- Brainstem
What makes up the cerebrum/forebrain?
Cerebral hemisphere (left and right)
What makes up the cerebral hemisphere? (name 1 thing)
Cerebral cortex
What makes up the cerebral cortex? (name 6 parts)
- Frontal lobe
- Parietal lobe
- Occipital lobe
- Temporal lobe
- Limbic lobe
- Insular cortex
What are sulci?
Inward folds
- Furrow or grooves
What are very large sulci called?
Fissures
What are gyrus or gyri?
folds, outward folds
What do you call a brain that lacks sulci and gyri?
Lissencephalic
Name the parts of the frontal lobe.
- Primary motor cortex
- Broca’s area
- Prefrontal cortex
What is the function of the primary motor cortex? ( located in the frontal lobe)
Movement
What is the function of the Broca’s area? ( located in the frontal lobe)
Production of written and spoken language
What is the function of the pre-frontal cortex? ( located in the frontal lobe)
Executive function
Name the parts of the parietal lobe.
Primary sensory cortex
What is the function of the primary sensory cortex?
tactile, sensory perception
What is the function of the inferior portion of the parietal lobe
Inferior portion involved in comprehension of language
What are the parts of the temporal lobe?
- Primary auditory cortex
- Wernicke’s area
- Hippocampus
What is the function of the primary auditory cortex
hearing
What is the function of the Wernicke’s area?
Language comprehension
What is the function of the hippocampus?
Memory
What is the part of the occipital lobe?
Primary visual cortex
What is the function of the primary visual cortex?
Vision
Where is the central sulcus located at (in relation to the lobes?
Between the frontal and parietal lobe
Where is the lateral sulcus located at (in relation to the other lobes)?
Near frontal, parietal, occipital, and temporal lobe
What are the 4 visible lobes?
Frontal, Parietal, Occipital, and Temporal
What are the 2 hidden cortex lobes?
Limbic lobe and insular cortex
What does the limbic lobe encircle?
Diencephalon
What is the function of the limbic lobe?
Involved in drive-related behaviors, emotional responses, movement, and memory.
If you were to pull down the temporal lobe, what do you expect to see?
Gyri of insula
What is the function of the insular cortex?
- Sensory processing
- Feelings and emotions
- Motor control
- Risk prediction
- Decision-making
- Bodily self-awareness
- Complex social functions like empathy
Outline the 8 steps of embryonic development.
What are trophoblasts? (and location)
- Cells that form the outer later of blastocysts.
- The placenta and yolk sac are formed from the trophoblast
What are epiblast cells? (and location)
- Cells located in the inner cell mass of blastocysts
- the brain and spinal cord (and rest of the body) are formed from the cells of epiblast cells
Pluripotent vs Totipotent cells?
“A totipotent cell has the potential to divide until it creates an entire, complete organism. Pluripotent stem cells can divide into most, or all, cell types in an organism, but cannot develop into an entire organism on their own”
What are embryonic stem cells (ESCs)?
Pluripotent embryonic stem cells are the epiblast cells from the inner cell mass of the blastocyst
Induced pluripotent stem cells (iPSCs)
Induced pluripotent stem cells can be created in the lab from any somatic cell in the body (skin and blood most common)
Derivatives of the embryonic germ layer
- Ectoderm
- Mesoderm
- Endoderm
What is gastrulation?
formation of the three germ layers
- gastrulation is the process by which the bilaminar blastocyst forms a trilaminar embryo
Name the three germ layers?
Ectoderm, Mesoderm, Endoderm
What do the three germ layers form?
The three germ layers of the embryo go on to form different tissue and organ systems of the body
What layer forms the brain and spinal cord?
The ectodermal layer forms the brain and spinal cord.
What are the two phases of neurulation?
Primary and Secondary Neurulation
What occurs during primary neurulation? (what germ layer is involved and what does it form)
The ectodermal germ layer forms the nervous system.
How does the neural plate form?
Ectoderm dorsal (above) to the notochord (along the midline of the ectodermal layer thickens to form the neural plate
What is invagination and what does it form?
Invagination forms the neural groove
How does the neural tube form?
Fusing of the neural folds completes the neural tube as it lengthens (3rd week)
What does the neural tube later become?
Brain and spinal cord
How does the neural tube become the brain and spinal cord?
- Rostral seals and expands = brain
- Caudal = spinal cord
What becomes the PNS neurons and glia?
Neural crest cells
How doest the epidermis (skin) form?
Epidermis (skin) forms from the most lateral ends of the neural plate.
List the 6 steps of Primary Neurulation from the image below.
- Ectoderm thickens
- The neural plate folds inward
- Superior edges fuse forming neural tube
- Neural tube detaches from the ectoderm
- The rostral (brain_ end of the neural tube closes first at day 24.
- The caudal (spinal cord) end of the neural tube closes last at day 28.
What is secondary neurulation?
the formation of the sacral spinal cord which occurs after neural tube closure
How many phases of specialization does the brain go through?
Two phases
What are the primary vesicles of the brain? (there are 3)
- Prosencephalon (Forebrain)
- Mesencephalon (Midbrain)
- Rhombencephalon (Hindbrain)
What part of the neural tube becomes the brain and spinal cord?
The rostral end becomes the brain and the caudal end becomes the spinal cord
How does the rostral end of the neural tube form the three primary brain vesicles?
The rostral end of the neural tube expands and constricts to form the three primary brain vesicles.
- The prosencephalon becomes the forebrain. The mesencephalon becomes the midbrain. The rhombencephalon becomes the hindbrain.
How do the primary vesicles differentiate into secondary vesicles? (what are their names and what do they differentiate from)
The prosencephalon differentiates into:
- Telecephalon
- Dicencephalon
The Rhombencephalon differentiates into:
- Metencephalon
- Myelencephalon
What secondary vesicles does the prosencephalon differentiate into?
The prosencephalon differentiates into:
- Telecephalon
- Dicencephalon
What secondary vesicles does the rhombencephalon differentiate into?
The Rhombencephalon differentiates into:
- Metencephalon
- Myelencephalon
What primary vesicle does not differentiate into a secondary vesicle?
Mesencephalon
When and how are secondary brain vesicles formed?
- Week 5
- In week 5 of embryonic development, secondary brain vesicles form
- The secondary vesicles that form are the telencephalon, diencephalon, metencephalon, and myelencephalon.
Name the adult brain structures that the telencephalon evolves into. (there are 4)
- Cortex
- Hippocampus
- Corpus Callosum
- Amygdala
Name the adult brain structures that the diencephalon evolves into. (there are 2)
- Thalamus
- Hypothalamus
Name the adult brain structures that the mesencephalon evolves into. (there are 2)
- Tectum
- Tegmentum
Name the adult brain structures that the metencephalon evolves into. (there are 2)
- Brain stem: pons
- Cerebellum
The caudal end of the neural tube develops into the …
Spinal cord
What are the secondary vesicles of the forebrain?
- Telencephalon
- Diencephalon
What are the secondary vesicles of the midbrain?
There are none!
What are the secondary vesicles of the hindbrain?
- Metencephalon
- Myelencephalon
Name the brain tissue that folds into the telencephalon?
Diencephalon
From what secondary vesicle does curve c-shape brain structures evolved from?
Telencephalon
What are examples of curved C-shaped structures formed from the telencephalon?
- Hippocampus
- Corpus Callosum
- Cingulate Cortex
- Lateral ventricles
- Basal ganglia
How/why does the diencephalon form deep brain structures and what are they?
The diencephalon forms the thalamus and hypothalamus because the telencephalon grows out and folds back while the diencephalon envelopes under it.
How many and what adult neural canal regions does the telencephalon form?
- 2
- Lateral ventricles
How many and what adult neural canal regions does the diencephalon form?
- 1
- Third ventricle
What adult neural canal regions does the mesencephalon form?
Cerebral aqueduct
What adult neural canal regions do the metencephalon and myelencephalon form?
Fourth ventricle
What adult neural canal regions does the spinal cord form?
Central canal
List the processes of brain growth/expansion.
- Neurogenesis and gliogenesis
- Neural migration
- Synaptogenesis
- Myelination
What is neurogenesis and gliogenesis?
formation of neurons and glial cells that populate the brain
What is neural migration?
movement of cells to different areas of the brain
What is synaptogenesis?
formation of synapses which are connections between neurons
What is myelination?
covering of the neurons axon with a fatty sheath (like insulation around an electrical wire) that allows neurons to conduct signals more efficiently and protects the neurons
What is proliferation?
Neurogenesis and gliogenesis is the production of new neurons and glial precursor cells through cell division
What is migration?
the movement of precursor cells from proliferative areas of the brain to their final location where the cells differentiate and specialize in function
What does mitotic mean?
Mitotic = dividing = stem and progenitor (precursor) cells
What does post-mitotic mean?
Post-mitotic = no longer dividing = mature (differentiated) cell types: neurons, astrocytes, oligodendrocytes
Where does cortex formation occur?
Forebrain (prosencephalon)
Where are excitatory neurons produced?
Lateral ventricle (ventricular zone)
Where are inhibitory neurons produced?
Ganglionic eminence (GE)
Name the type of migration that excitatory neurons participate in.
Radial migration
Name the type of migration that inhibitory neurons participate in.
Tangential migration
What does radial migration cause?
- Radial migration forms the layers of the cortex.
- Cortex layers form from the inside out (deepest layers near ventricles form first) -only makes the excitatory neurons
What is cortical layering?
the formation of the six distinct layers of the adult cortex
What is a synapse?
a junction between two nerve cells through which they signal/communicate chemically
Output to other neurons: axon terminals
Input from other neurons: dendrites
What is synaptogenesis?
The formation of synapses between neurons in the nervous system
- Explosion of synapse formation occurs during early brain development
At birth how many synapses does each neuron have in the cerebral cortex?
2500 synapses
By 2-3 yrs old, how many synapses does each neuron have?
15,000 synapses
By adulthood, how many synapses does each neuron have?
7,000 synapses
Yes or No: Is synaptogenesis always happening with neurons located right next to each other?
No, synaptogenesis isn’t always happening with neurons located right next to each other. Neurons can grow very long projections to make synaptic connections on the other side of the brain or all the way down in the spinal cord.
What is myelination?
The process of wrapping a thick, fatty sheath called myelin around the axon of a neuron allows nerve impulses (action potentials) to move more quickly down the axon like insulation on an electrical wire. Myelin sheaths are formed by oligodendrocyte cells in the CNS and Schwann cells in the PNS.
Why does the process of myelination increase the size of the brain?
The process of myelination increases the size of the brain because the myelin sheaths formed around the axons of the billions of neurons in the brain have significant mass and weight.
At what age does developmental brain myelination and synaptic pruning complete?
Around the age of 20 yrs old
What is the overview of the stages of brain development? (8 on the slides)
- Neural induction
- Proliferation (growth)
- Migration (growth)
- Regional specification
- Myelination (growth)
- Synaptogenesis (growth)
- Selective cell death / apoptosis (refinement/reduction)
- Synaptic pruning
What is neural induction?
production of cells that will become nervous tissue (gastrulation and neurulation)
What is proliferation? (growth)
generation of neurons and glia through cell reproduction
What is migration? (growth)
location of cells in appropriate brain areas
What is regional specification?
Differentiation of neurons into particular types with specific functions
What is myelination? (growth)
ensheathing of neuron axons in fatty covering
What is synaptogenesis? (growth)
formation of appropriate synaptic connections between neurons (communication)
What is selective cell death (apoptosis)? (refinement/reduction)
Elimination of mislocated cells and cells that failed to form proper synaptic connections
What is synaptic pruning (refinement/reduction)?
strengthening synapses in use, removing underused synapses
Pre or Post-natal process? Gastrulation
Pre-natal (0-4 weeks)
Pre or Post-natal process? Neurulation
Pre-natal (0-4 weeks)
Pre or Post-natal process? Neurogenesis
Pre-natal (4-12 weeks)
Pre or Post-natal process? Gliogenesis
Pre-natal (4-12 weeks)
Pre or Post-natal process? Initiation of haematopoiesis
Pre-natal
Pre or Post-natal process? Neural migration
Pre-natal
Pre or Post-natal process? Apoptosis
Occurs in the span of both
Pre or Post-natal process? Migration of immune stem cells and expansion of progenitor cells
Pre-natal
Pre or Post-natal process?
Synaptogenesis
Occurs in the span of both
Pre or Post-natal process? Colonization of immune cells
Pre-natal
Pre or Post-natal process? Myelination
Occurs in the span of both
Pre or Post-natal process? Synaptic pruning
Post-natal
Pre or Post-natal process? Maturation of innate and adaptive immunity
Post-natal
What is defined as programmed cell death
Apoptosis
Why does apoptosis occur?
Takes place to prevent redundancy in the CNS (excessive cells can also lead to abnormal synaptic connections if the cells are not eliminated through apoptosis)
Why does pre-natal neuronal apoptosis occur?
Based on access to survival factor, chemical signals received from successful connections with other neurons
Why does post-natal apoptosis occur?
Neurons with weak (under used) connections will die, and apoptosis is therefore based on postnatal experiences.
What is synaptic pruning?
Removes weaker (less used) synaptic contacts between neurons while more active connections are kept and strengthened
What is the phrase for the ability of the brain to develop new connections and to prune underused connections?
Plasticity (this allows the brain to adapt to its environment and to injury)
In what processes is synaptic pruning important?
Learning and memory
What does “use it or lose it” mean?
Both synaptic pruning and apoptosis produce a “use it or lose it” dynamic to the function of the brain. For synaptic connections that are not used, the brain removes them.
What percent of babies are born with a birth defect of any kind?
3%
List the diseases associated with neural tube defects.
- Anencephaly
- Spina bifida
What is anencephaly?
Anencephaly results from incomplete closure of the anterior neural tube. The consequence is an absence of significant portions of the brain, skull, and scalp. These children are born without the neocortex and they do not survive.
What spina bifida?
Spina bifida results from incomplete closure of the posterior neural tube. The spinal cord protrudes through the opening. While the opening can be surgically closed, this does not restore normal spine function.
What should expecting individuals take during pregnancy to decrease the incidence of spina bifida?
Folic acid
What are the diseases associated with neural migration defects?
- Lissencephaly
What is Lissencephaly?
- smooth brain
- rare brain formation disorder caused by defective neuronal migration during the 12th to 24th weeks of gestation resulting in lack of development of brain holds
- children with lissencephaly have significant developmental delays, but these vary greatly from child to child depending on degree of brain malfunction.
What are some diseases associated with brain growth defects?
- Microcephaly
- Macrocephaly
What is associated with microcephaly?
- Intellectual disability
- Poor motor function
- Delayed or absent speech
- Epilepsy (seizures)
What environmental exposures may cause microcephaly?
Viruses like CMV and Zika directly infect the fetus have been shown to be a cause of microcephaly
Do all virsuses cross the placenta barrier?
No
What is associated with macrocephaly?
- Autism
- Intellectual disability
- Epilepsy
Are all head en;argements attributed to macrocephaly?
No
What other condition causes head enlargements?
Hydrocephalus
What is hydrocephalus
- causes head enlargements
- a condition in which there is an accumulation of cerebrospinal fluid (CSF) within the brain due to a blockage somewhere within the ventricle system throughout the brain preventing drainage and reabsorption of CSF. This typically causes increased pressure inside the skull and compression of the brain tissue against the skull.
What is defined as a brain mass increase (over-growth) with skull enlargement?
Macrocephaly
What is defined as brain compression with skull enlargement
Hydrocephaly
How does mild brain overgrowth occur?
Associated with maternal infection (virus or bacteria) that cuases a maternal immune system response but does not involve direct infection of the fetus
What are examples of sites of brain overgrowth?
Frontal, temporal, amygdala
Is there an environmental cause to brain overgrowth?
Yes, can be associated with maternal infection that causes a maternal immune response but does not involve direction infection of fetus.
What defects involve infection of the fetus caused by environmental factors?
Microcephaly
