Week 1 Flashcards
1
Q
What is developmental biology?
A
The series of changes which animal and vegetable organisms undergo in their passage from the embryonic state to maturity, from a lower to a higher state of organisation (Biology online)
Developmental biology is the study of the process by which organisms grow and develop. Modern developmental biology studies the genetic control of cell growth, differentiation and the morphogenesis, which is the process that gives rise to tissues, organs and anatomy (Wiki)
2
Q
What does the study of development help us to understand?
4 reasons
A
To understand…
- How animals (and plants) develop
- How tissues can regenerate
- Mechanisms of congenital diseases, birth defects and cancer
- How different structures evolved
3
Q
What does the study of development help us to harness information for?
3 reasons
A
To harness information for…
- Developing regenerative therapies
- Treating congenital disease
- Treating cancer
4
Q
How do we use model organisms?
A
To manipulate:
- Genetically
- Pharmacologically
- Ablation
- Transplantation
To assay:
- Traditional methods plus whole animal fixed and live assays e.g. live labels
- Locomotion (YOU WILL BE EXPECTED TO KNOW THE COMMON ONES AND HOW THEY WORK)
Aim to determine cause and effect, correlations are not enough!!!
5
Q
How are the mechanisms driving embryonic development controlled?
A
- Generation of cells - cell division and growth
- The generation of different cells - cell differentiation
- The generation of the shape of cells, tissues, organs, the whole body - morphogenesis
6
Q
How are the mechanisms driving embryonic development controlled (the 2 main ways)?
A
Intrinsically
- E.g. expression of a specific transcription factor such as Zic2 in a cell turns on expression of a set of genes (Slug, FoxD3) in the cell expressing Zic2
Induced/Extrinsically
- E.g. expression of Shh from the notochord forms a gradient and receiving cells
- Differentiate differently depending on how much they perceive
7
Q
What are the underlying changes in the control of embryonic development?
A
- Gene/Protein expression
E.g. proteins of the differentiated state such as a neurotransmitter in neurons; proteins of a partially differentiated state such as Zic2 in neural crest cells - Cytoskeleton
E.g. cell motility, cell shape - Connections
E.g. cell-cell, cell-matrix
8
Q
What are the signals involved in neural crest induction?
A
BMP4
Notch
Wnt6
Fgf
9
Q
What does the neural crest express?
A
Slug (Snail)
FoxD3
10
Q
What does a gene signalling network result in?
A
The birth of the neural crest
11
Q
What are the three steps to cell division and differentiation in embryonic development?
A
- The generation of cells - cell division and growth
- The generation of different cells - cell differentiation
- The generation of the shape of tissues/organs/the whole body-morphogenesis
12
Q
What is cell division in embryonic development?
A
The process by which cells double their content, then divide to produce two daughter cells
These daughter cells have half of the cell contents each
Regulation is important
Many checkpoints
Can be symmetric or asymmetric
- Symmetric - two daughter cells are the same as each other
- Asymmetric - two daughter cells are different from each other
13
Q
What are the 3 cycles of the cell division?
A
- The chromosome cycle
- DNA replication and segregation (mitosis) - Cytoplasmic cycle
- Organelle replication and physical division (cytokinesis) - The centrosome cycle:
- Replication of the mitotic spindle
14
Q
What are totipotent cells?
A
Cells that can differentiate fully to produce any type of cell
E.g. Epiblast cells can differentiate into any embryonic cell, unlimited capacity to proliferate
15
Q
What are pluripotent cells?
A
Cells that can partially differentiate to produce several types of cells
E.g. ectoderm can become neural or epidermal;
E.g. Neural crest can become cartilage or neurons of peripheral nervous system; can proliferate
E.g. Neuroepithelial cells, radial glial cells, intermediate progenitor cells
16
Q
What are differentiated cells?
A
Cells that have taken on a final character, they rarely differentiate
E.g. Neurons don’t proliferate
E.g. Microglia are immune cells in the brain that do differentiate
17
Q
What are the two steps in differentiation?
A
Specification
- Capable of autonomous differentiation in isolation (if in test tube or dish) but can be reversed.
- Not “Fate committed”
Determination
- When the cell differentiates into a specific cell type, even when it is placed amongst cells of a different type.
- This is irreversible and “Fate committed” or is it?
18
Q
What is final cell differentiation?
A
When cells that have differentiated have reached their final specialised form
They differ from each other both structurally and functionally
They express specific sets of genes/proteins that are characteristics of that particular cell type e.g. specific neurons express specific neurotransmitters
Differentiated cells are often post mitotic - cannot undergo further cell division and are in G0. This is terminal differentiation
Some differentiated cells can be:
- Slowly dividing (e.g. satellite cells in the muscle)
- Divide when stimulated to (e.g. microglia in the brain)
19
Q
What are two ways a cell can change its differentiated state?
A
Regeneration
Functional adaptation/plasticity
20
Q
What is regeneration?
A
During regeneration - some animals can regenerate body parts after injury. Cells at the injured site de-differentiate
An example is the newt limb. Injury prompts muscle cells to dedifferentiate and then re-differentiate into cartilage
21
Q
What is functional adaptation/plasticity?
A
One part of the brain can take over functions of another missing one, e.g. woman born without a cerebellum, who took longer to learn to walk and speak and only had relatively mild motor and speech problems
Plasticity = capacity to change structure and function over time
22
Q
What is morphogenesis?
A
The generation of shape
Contraction
- Cell or tissues
Adhesion
- Between cells, or between cells and the extracellular matrix
Location
- Depends on induction and cell migration
23
Q
What is the structure of epithelial cells?
A
Sheet or tube of cells
Cells have apical-basal polarity and sit on basal lamina
Cells regular shape, tightly connected and communicating via tight junctions, adherens junctions, gap junctions and desmosomes e.g. neural plate, neural tube
24
Q
What is the structure of mesenchymal cells?
A
Loosely connected
Often irregularly shaped cells
Mobile or migratory
Delicate balance of adhesion with matrix
Dynamic cytoskeleton e.g. neural crest cells, migratory neurons
25
What are the steps in the epithelial to mesenchymal cell transition (EMT)?
1. Basal lamina broken down
2. Cell elongates
3. Cell breaks inter-cellular connections
4. Cell assumes "bottle" shape characteristic of cell undergoing EMT
5. Cell no longer connected to any other cell-mesenchyme
26
What is cloning from adult cells?
An example of de-differentiation to make multiple cell types. Requires knowledge of factors that induce stem-ness
Dolly the sheep was made from a cell derived from an adult udder (a slow dividing, differentiated cell).
Viable cloned animals (mice) have been produced from terminally differentiated olfactory neurons
27
What is stem cell therapy for age-related macular degeneration (AMD) and why is it used?
Need to repopulate retina with healthy cells
Avoid rejection by using patient's own cells
De-differentiate to produce stem cells
Re-differentiate to make retinal pigmented epithelial (RPE) cells and implant into eye
With stem cells, it is possible to correct a congenital genetic defect
28
What 2 things aid investigation of gene function?
1. Mutants
2. Fluorescent markers aid visualisation
29
What are the pros and cons to using model organisms?
Pros:
- Easy to breed year round
- Easy to maintain in a lab
- Easy to keep in large numbers
- Fast development
- All have a sequenced genome
- Display similarities to humans
Cons:
- No single model is sufficient so often a combination is used in research
- Other considerations, cost, availability, suitability to answer your research question
30
What are the invertebrates used as animal models?
Social amoeba
- Single cells coalesce to form a fruiting body
- Haploid
- Genetically tactable and versatile
- Transparent
Nematodes
- Lineage of every cell known (302 neurons)
- Genetically tractable and versatile
- Transparent
Fruit fly
- More complex anatomy and behaviour
- Genetically tractable and versatile
31
Why are zebrafish used as animal models?
- Small, cheap, easy to keep
- Transparent - good for anatomical development
- Fast development
- Amenable to genetic embryology
- Easy to mutate
32
Why are African Clawed Frogs (Xenopus laevis) used as animal models?
- Large eggs
- Develop external to mother
- Easily manipulated for experimental embryology
- Genetics difficult as they have 4 copies of each gene!!!!
33
Why are chickens (Gallus callus) used as animal models?
- Develop external to mother
- Large embryo
- Easily experimentally manipulated
- Closer to humans than Xenopus or Zebrafish
- Not often used for genetics as adults so large
34
Why are mice (Muscus domesticus) used as animal models?
- Mammalian therefore closest to humans
- Same number of genes, in same order
- Transgenics, knockouts
- Small, short breeding cycle
- Poor for experimental studies on embryos also as harm mother
35
What is the function of neurons?
To carry electrical impulses
Transfer them to other neurons via transmitters
36
What are the three components to neurons?
A. Cell body:
- Cytoplasm filled region containing nucleus
B. Dendrites:
- Numerous projections from cell body
- Receive impulses
- Post synaptic membranes contain receptors for neurotransmitters
C. Axon:
- Single projection
- Carries impulses AWAY from cell body
- Pre-synaptic membranes release neurotransmitters
37
What are the 5 functions of Glia?
1. Insulates axons by producing Myelin
- Cells in CNS called Oligodendrocytes
- Cells in PNS called Schwann Cells
2. Provide energy, maintain environment, synaps pruning, contribute to blood-brain barrier
- Astrocytes
3. Macrophage (innate immunity), synapse pruning
- Microglia
4. Secrete and move cerebrospinal fluid (CSF)
- Ependymal cells
5. Stem cell, stratum for neurons to migrate
- Radial glial cells
38
What are the interactions of Neurons and Glial cells?
An oligodendrocyte wraps myelin around axons
An astrocyte extension touches the synapse
Astrocyte extensions contact the blood vessel
39
What is the classification of Neuronal cells?
1. Localisation of cell nucleus
A. Central Nervous System (CNS) (From neural tube)
2. Level of control
A. Somatic or voluntary. Controls skeletal muscle
B. Autonomic or involuntary. "Resting activities". Controls heart, gut peristalsis, sweat glands...
Split into sympathetic and parasympathetic - Opposing function
E.g. Sympathetic system innervating heart increases beat, parasympathetic decreases
3. Function
A. Relay signals to the CNS - sensory or afferent
B. Relay signals away from the CNS - motor or efferent
40
Where do neuronal cells come from?
Differentiated neurons, glia and ependymal cells in correct locations with correct connectivity for function
41
What is the Gastrula made up of?
Ectoderm
Mesoderm
Endoderm
42
What are the steps of brain development?
Induction
Neurulation
Elaboration
43
What processes are involved in brain development?
Patterning
Cell division, growth and differentiation
Migration and pathfinding
Shape changes
44
What is neurulation?
Formation in the early embryo of the neural plate, including its closure to develop the neural tube
Neural tube becomes central nervous system (predominantly neurons and glia)
Neural crest becomes peripheral nervous system (neurons and glia); melanocytes; some craniofacial cartilage, bones and dermis
45
What happens in neural plate induction?
Ectoderm
Mesoderm
Endoderm
-->
Epidermis - Neural - Epidermis
LPM - Not - LPM
Endoderm
46
What signals are involved in neural tube and neural crest induction?
Epidermis:
- Wnt
- BMP
Placodal cells:
- Wnt --> BMP
Neural crest:
- Wnt --> BMP
Neural cells:
- Wnt
47
What happens in neurulation?
Neural tube formed
1. Neural plate slightly curved to form neural groove with neural folds either side
2. Neural folds come closer together and form neural crests with a deeper neural groove
3. Neural crests touch and a fusion of neural folds occurs, formin the neural tube
4. Neural folds fuse to form epidermis. Neural crest forms underneath with the neural tube under that. From the neural crest melanocytes, schwann cells, adrenal medullary cells, dorsal root ganglion cells and cranial nerve cells and autonomic ganglion cells.
48
Steps of primary and secondary neurulation
Primary:
1. Initial epithelium
Convergence and extension
- Correct width
2. Columnarisation
Convergence and extension
- Correct width
3. Rolling/Folding
Localised contraction
(actin cytoskeleton)
--> Zic 2
--> MHP
--> DLHP
4. Closure
Epithelial to mesenchymal transition
- Interdigitation/contact
- Neural crest migration
5. Neural tube complete
Secondary:
1. Dispersed mesenchyme
2. Mesenchymal condensation
3. Medullary Cord/Neural rod
4. Epithelial transition/cavitation
5. Neural tube complete
49
What signals control convergent extension in neurulation?
Wnt5a non-canonical wnt signalling
Planar cell polarity proteins (PCP)
50
What signals are involved in the control of rolling/folding in neurulation?
Zic2 and 5 regulate formation of dorso-lateral hinge point (DLHP) and myosin II localisation
Blebbistatin inhibits myosin II
51
What are the functions of Cadherin?
pre-EMT and in neuroepithelial cells
- Full-length N-cad mediates homophilic adhesion between cells and is anchored to the actin cytoskeleton via the catenin complex
BMP signalling stimulates N-cad cleavage, reducing adhesion and releasing a cytoplasmic fragment that moves to the nucleus and induces transcription of pro-EMT genes.
BMP also upregulates Cad6, which feeds back on BMP signalling and leads to de-epithelialisation of premigratory NCCs.
In migrating NCCs, cleaved Cad11 signals via Rho GTPases to stimulate cell protrusions and migration
52
What happens during closure in neurulation?
N-Cadherins and E-Cadherins produced
Non-neuronal ectoderm wraps itself around the neural ectoderm at the edge of the closing neural folds
Cellular bridges from the non-neuronal ectoderm connect the two juxtaposed neural folds
53
What are the closure locations in neurulation?
Closure 1
(Craniorachischisis)
- back of foetus, base of skull
Closure 2
(Anencephaly)
- top of skull
Closure 3
- Jaw/mouth
Closure 4
- Human only
- Just above Closure 1, by hindbrain
Closure 5
- Human only
- Tailbone area
54
What is happening in Antero-posterior patterning (early)?
Rostral (towards head)
(Telencephalon)
- αBMPs
- αWnts
Mid/Hindbrain
- FGF8
Caudal (towards tail)
(Spinal Cord)
- Wnts
- RA
55
What is the process of dorso-ventral patterning?
A. BMP4, 7 in epidermis
Shh in notochord
B. BMP4 in roof plate
Shh in floor plate
C. TGF-ß family:
1. BMP4, BMP7, BMP5, Dorsalin, Activin
2. BMP7, Dorsalin, Activin
3. Dorsalin, Activin
D. Gradient of TGF-ß family
- Roof plate
- D1 interneurons
- D2 interneurons
- V0 interneurons
D. Gradient of Shh
- V1 interneurons
- V2 interneurons
- Motor neurons
- V3 neurons
- Floor plate
56
What is the Dorso-ventral patterning of Shh?
A. In order of closest to the notochord going up:
1. FP
2. V3
3. Motor
4. V2
5. V1
B. Notochord
Then Floor plate
Then Motor Neuron region
C. Then Secondary set of motor neurons and then in between them is the secondary floor plate.
In the secondary floor plate, there is a donor notochord, floor plate, or other Shh-secreting cells.
57
What is the left-right patterning?
LEFT
Hensen's node
- Shh
- Cerberus
- BMPs
- Nodal
- Snail
- Pitx2
Separated by midline
RIGHT
Hensen's node
- Activin --> Shh
- BMP4 --> Fgf8
- Cerberus
58
What are the steps of vesicle formation and elaboration?
1. Occlusion
2. Pressure builds and induces faster rate of cell division
59
Describe 3 vesicle vs 5 vesicle:
3:
- Prosencephalon (forebrain)
- Mesencephalon (midbrain)
- Spinal cord
5:
- Telencephalon (cerebral hemispheres)
- Optic vesicle
- Diencephalon
- Pons (metencephalon)
- Medulla (myelencephalon)
- Spinal cord
60
What happens in cell division in the early neural tube?
Mitotic cells are found near the inner surface of the neural tube, adjacent to the lumen
The dynamic distribution of Par-3 protein in these luminal stem cells regulates the synthesis of Notch signalling pathway components in the cell membrane of the daughter cells
At mitosis, Par-3 becomes localised primarily to one of the two daughter cells
That daughter cell will express Notch and remain a stem cell; the cell receiving less Par-3 will express less Notch and become a neuroblast (neural progenitor cell).
After producing neurons, neuroblasts switch to the production of glial cells.
61
Describe cell migration in the early neural tube:
SYNTHESIS
- Basal, cells heading towards apical
G2
- Still closer to basal, cells heading towards apical
G2-MITOSIS
- Cells at apical
MITOSIS
- Cells at apical
G1
- Both daughter cells move towards basal
G1 pt2
- Cells reach basal
62
Describe mouse neocortex organisation:
63
What is the process of neuronal migration?
Extracellular cues/receptors:
- Reelin
- Ephrins
- RA
- Wnt
Intracellular Signal Transduction
- Actins, Tubulins, P13k/RhoA
- Cdk5, Dab1
- APC, PAR6/PKC, GSK3
- Dynein, Dcx, Lis1, Ndel1
- Myosin II
A. Leading process extension
P13K, MT-actin interaction, MT remodelling
- Elongation of the microtubules
B. Forward movement of the centrosome
GSK3ß, PAR6, APC, Actin, Dcx, Myosin II
Dynein motor complex: Lis1, Disc1, Ndel1
- Microtubules contract, centrosome retracts with microtubules, cell rear left elongated
C. Nucleokinesis and trailing process retraction
Myosin II
- Cell rear trails after centrosome, retracting until it is back next to it.
64
What does migration along glia to final site require?
Changes in adhesion
In reeler mutant mice, Cajal-Retzius cells lack Reelin. Pre-plate partitioning by CP neurons fails and later layers are inverted
65
How were robo and slit first found?
In drosophila through mutagenesis
66
Describe axon growth and pathfinding:
Growth cone response to attractive and repulsive forces.
The periphery of the growth cone contains lamellipodia and filopodia
The lamellipodia are the major motile apparatus and are seen in the regions that are turning toward a stimulus.
The filopodia are sensory. Both contain actin microfilaments. There is also a central region of microtubules, some of which extend outwards and join the filopodia.
The transition region between them contains regulatory proteins that can extend or retract the cytoskeleton.
The microtubules entering the peripheral area can be lengthened or shortened by proteins activated by the attractive or repulsive stimuli.
During attraction, proteins bind to the plus ends of the microtubules, stabilising and lengthening them.
On the side opposite the attractive cue, microtubules are removed from the periphery.
The four major ligands providing cues to the growth cone (ephrins, netrins, slit proteins, and semaphorins) bind to receptors that stabilise or destabilise actin microfilaments.
The Rho family of GTPases (RhoA, Rac1 and Cdc42) act as mediators between the receptors and the agents carrying out the cytoskeletal changes.
67
What is the role of Ephrins, Netrins, Slit and Semaphorins?
Guidance cues (ligands)
Bind to receptors
Ephrins and Netrins bind to G-exchange factors (GEFs)
Slit and semaphorins bind to G-activating proteins (GAPs)
These stabilise or destabilise actin microfilaments.
Rho family GTPases - RhoA, Rac1, Cdc42 - act as mediators for integration and coordination
RhoA communicates with cytoskeletal effectors
--> Rock
Causes cytoskeletal changes
- MLCK --> Myosin II --> Actomyosin contraction
- LIMK --> Cofilin --> F-actin disassembly
RAC1 communicates with cytoskeletal effectors
--> Formin
--> Ena/VASP
--> Arp2/3
Causes cytoskeletal changes
- F-actin polymerisation
Cdc42 communicates with cytoskeletal effectors
--> Arp2/3
Causes cytoskeletal changes
- F-actin polymerisation
68
How does the human spinal cord develop?
The neural tube is functionally divided into dorsal and ventral regions, separated by the sulcus limitans.
As cells from the adjacent somites form the spinal vertebrae, the neural tube differentiates into the ventricular (ependymal), mantle, and marginal zones, as well as the roof and floor plates.
The sulcus limitans separates the dorsal (alar) part of the spinal cord that receives information from the ventral (basal) part of the spinal cord, which projects motor neurons.
69
How is the spinal cord or medulla organised zone-wise?
Central canal, ventricular zone, intermediate (mantle) zone, marginal zone
70
What does the neural tube differentiate into?
Spinal cord or medulla
Cerebellum
Cerebral cortex
71
What is the structure of the neural tube?
From left to right:
Ventricular zone
Intermediate zone
Marginal zone
72
What is the structure of the cerebrum (zone wise)?
from left to right:
Ventricle
Ventricular zone
Intermediate zone
Internal granular zone
- BMPs induce differentiating cells to be granule cells
Purkinje cell layer
Marginal zone
Neuroblasts
- Shh maintaining proliferating neuroblasts
External granular layer
Migration along glia to final site requires changes in adhesion - in reeler mutant mice, glial cells lack ECM protein Reelin so neuroblasts can't bind to them
73
What is the structure of the cerebral cortex (zone-wise)?
left to right
Ventricle
Ventricular zone
Sub-ventricular zone *
Intermediate zone *
- * White matter
Cortical plate
- Neocortex
Marginal zone
Molecular layer
Neuroblasts migrate through the white matter and start a new layer of neurons outside the first
74
Main parts of human brain and canine brain:
HUMAN:
- Brain
- Ventricles
- CSF
- Spinal Cord
CANINE:
- Telencephalon (cerebrum)
- Metencephalon (cerebellum and pons)
- Diencephalon
- Mesencephalon (midbrain)
- Myencephalon (medulla oblongata)
75
Describe the components of the spinal cord and peripheral nervous system:
SENSORY RECEPTOR i.e. hand
SENSORY STRETCH RECEPTOR i.e. leg muscle
SENSORY NEURON
- Dorsal root
- Dorsal root ganglion
SPINAL CORD
- Interneuron
MOTOR NEURON
- Ventral root
EFFECTOR ORGAN
76
What is the monosynaptic reflex?
Direct communication between sensory and motor neuron
77
What is the polysynaptic reflex?
Interneuron facilitates sensory-motor communication
78
What are the major derivatives of ectoderm and their BMP levels required to form?
1. Surface ectoderm (epidermis)
- High BMP levels
2. Neural Crest
- Moderate BMP levels
3. Neural plate/Neural tube
- Low BMP levels, Sox transcription factors expressed
79
What is the surface ectoderm (epidermis) used in?
Epidermis
Hair
Nails
Sebaceous glands
Olfactory epithelium
Mouth epithelium
- Anterior pituitary
- Tooth enamel
- Cheek epithelium
Lens, cornea
80
What is the Neural crest used for?
Peripheral nervous system
- Schwann cells
- Glial cells
- Sympathetic nervous system
- Parasympathetic nervous system
Adrenal medulla
Melanocytes
Facial cartilage
Dentine of teeth
81
What is the Neural plate/neural tube used for?
Brain
Neural pituitary
Spinal cord
Motor neurons
Retina
82
What is the structure of the neural tube primary vesicles from top to bottom?
Wall
Cavity
Forebrain
(Prosencephalon)
Midbrain
(Mesencephalon)
Hindbrain
(Rhombencephalon)
83
What does the forebrain (prosencephalon) in the primary vesicle become in the secondary vesicle?
Telencephalon
Diencephalon
84
What does the midbrain (mesencephalon) in the primary vesicle become in the secondary vesicle?
Mesencephalon
85
What does the hindbrain (rhombencephalon) in the primary vesicle become in the secondary vesicle?
Metencephalon
Myelencephalon
86
What is the structure of the neural tube secondary vesicles from top to bottom?
Telencephalon
Diencephalon
Mesencephalon
Metencephalon
Myelencephalon
Goes down to spinal cord
87
What are the adult derivatives of the neural tube, deriving from the Telencephalon?
Olfactory lobes - smell
Hippocampus - memory storage
Cerebrum - Association (*intelligence)
88
What are the adult derivatives of the neural tube, deriving from the diencephalon?
Optic vesicle - Vision (retina)
Epithalamus - Pineal gland
Thalamus - Relay centre for optic and auditory neurons
Hypothalamus - Temperature, sleep and breathing regulation
89
What are the adult derivatives of the neural tube, deriving from the mesencephalon?
Midbrain - Temperature regulation, motor control, motivation, and emotional control
90
What are the adult derivatives of the neural tube, deriving from the metencephalon?
Cerebellum - Coordination of complex muscular movements
Pons - Fibre tracts between cerebrum and cerebellum
91
What are the adult derivatives of the neural tube, deriving from the myelencephalon?
Medulla - Reflex centre of involuntary activities
92
What are some neural crest derivatives?
Peripheral Nervous system (PNS)
Endocrine and paraendocrine derivatives
Pigment cells
Facial cartilage and bones
Connective tissue
93
What cell type or structure derives from the peripheral nervous system (PNS)?
Neurons, including sensory ganglia, sympathetic and parasympathetic ganglia, and plexuses
NeuroGlial cells
Schwann Cells and other glial cells
94
What cell type or structure derives from the endocrine and paraendocrine derivatives?
Adrenal medulla
Calcitonin-secreting cells
Carotid body type I cells
95
What cell type or structure derives from the pigment cells?
Epidermal pigment cells
96
What cell type or structure derives from the facial cartilage and bones?
Facial and anterior ventral skull cartilage and bones
97
What cell type or structure derives from the connective tissue?
Corneal endothelium and stroma
Tooth papillae
Dermis, smooth muscle, and adipose tissue of skin, head, and neck
Connective tissue of salivary, lachrymal, thymus, thyroid, and pituitary glands
Connective tissue and smooth muscle in arteries of aortic arch origin
98
How do placodes contribute to the nervous system?
Cranial places form sensory neurons
A portion of the pharyngeal endoderm secretes Fgf8, which induces the mesoderm overlying it to secrete Fgf19
Fgf19 is received by both the prospective otic placode and the adjacent neural plate
Fgf19 instructs the neural plate to secrete Wnt8c and Fgf3, two paracrine factors that work synergistically to induce Pax2 and other genes that allow the cells to produce the otic placode and become sensory cells
99
What is the strucutre of the cranial placode?
Olfactory
Neural plate
Lens
Notochord
Trigeminal
Geniculate
Epibranchial
Petrosal
Otic
Nodose
Neural crest
Primitive streak
Epidermis
Somites
100
What are the main components of the elaborate vertebrate brain?
Cerebrum
Olfactory lobe
Optic lobe
Cerebellum
Spinal cord
Medulla oblongata
101
What are the main components of the simple vertebrate brain?
Olfactory bulb
Cerebrum
Optic lobe
Cerebellum
Medulla oblongata
Spinal cord
(Fish brain)
102
Describe the embryonic brain:
three to four week embryo:
Three primary vesicles
- Prosencephalon (forebrain)
- Mesencephalon (midbrain)
- Rhombencephalon (hindbrain)
five week embryo:
Five secondary vesicles
- Telencephalon - cerebrum
- Diencephalon - Eye cup, Thalamus, hypothalamus, and epithalamus
- Mesencephalon - Midbrain
- Metencephalon - Pons, Cerebellum
- Myelencephalon - Medulla oblongata
103
What does the embryonic forebrain, or prosencephalon, divide into?
The telencephalon and diencephalon
104
What do we know about telencephalon?
The telencephalon can be subdivided into pallium and sub pallium
The relative proportions of each varies between vertebrates
Structure:
- Medial pallium
- Dorsal pallium
- Lateral pallium
- Subpallium
- Septum
(grey matter)
105
What do we know about the dorsal pallium?
Forms neocortex. Divided into frontal, parietal occipital and temporal lobes.
Folded in primates, smooth in others.
Functions associated with "higher functions", such as language, motor commands and conscious thought
Differs a lot between species
When we're looking at the brain, most of it is the dorsal pallium. Part of the brain that differs most between species:
- In volume
- Number of neurons
- Glial cells etc
106
What do we know about the medial pallium?
Forms hippocampus
Functions short to long term memory. Spatial awareness
Appearance differs in fish and amphibians but has similar functions
Hippocampus has a very specific shape
- Fish and amphibia look very different to higher vertebrate (primates etc)
--> So many thought there was no hippocampus
107
What do we know about the lateral pallium?
Forms olfactory bulb/lobe and amygdala
Function olfaction. Memory and emotion.
Olfactory bulb small in humans in comparison to most species.
So as vertebrates, humans are quite poor at smelling
108
What do we know about the ventral pallium?
Forms claustrum and amygdala
Functions consciousness. Memory and emotion
109
What are the structures in the limbic system?
Singulate Gyrus
Septum
Claustrum
Olfactory bulb
Hypothalamus
Amygdala
Mammillary body
Hippocampus
110
What is the structure of the sub pallium?
Lateral ganglionic eminence
Medial ganglionic eminence
Telencephalic Stalk:
- Striatum (lateral ganglionic eminence)
---> Coordinates movement
- Pallidum (medial ganglionic eminence)
---> Voluntary movement
111
What are the three subdivisions of the diencephalon?
1. Thalamus - relays motor and sensory info to cerebral cortex
2. Hypothalamus - endocrine hormone release
3. Epithalamus - connects limbic system to the rest of the brain, hormone release (pineal gland)
112
What are two parts of the midbrain and hindbrain important for sensory processing?
Tectum - superior and inferior colliculi (visual and auditory reflex centres respectively)
Tegmentum - cerebral peduncles (conveys motor info) substantia nigra (motor planning)
Important for sensory processing from the periphery
Substantia nigra
- Where we see dopamine produced
- Problems here in people with Parkinsons
113
What is the Substantia nigra?
Where we see dopamine produced
Problems here in people with Parkinsons
114
What does the cerebellum do?
Coordinates voluntary movements
E.g. posture, balance and speech, resulting in smooth, balanced muscular activity
Very important for us.
Folds called Arbor Vitae - tree of life
Cerebellum divided into 3 sections
115
What do we know about the pons and medulla?
Pons containing reflex centres (breathing)
Medulla contains reflex centres (breathing, heart rate and blood pressure)
