NSB 1. Overview of the Nervous System and Development Flashcards
What are neurons?
cells that transmit nerve impulses
What are glia?
non-neuronal cells in the central and peripheral nervous system
What are microglia?
macrophages found in the brain and spinal cord
What does the Central Nervous system consist of?
[1] brain
[2] brain stem
[3] spinal cord
What does the Peripheral Nervous system consist of?
all the nerves in the body that are found outside the spinal cord
What are the parts of a neuron?
[1] Cell Body
[2] Dendrites
[3] Axon
[4] Nerve Terminals/Synaptic Vesicles/Neurotransmitters
What are glial cells? What are the different types of glial cells?
Glial Cells: they provide structural support and myelin to the nervous system
[1] Astrocytes
[2] Oligodendocytes
[3] Schwann Cells
What are the different types of supporting cells of the nervous system? [3]
[1] Astrocytes
- provide structural support/blood brain barrier
[2] Oligodendrocytes
- form myelin in CNS
[3] Schwann Cells
- produce myeline in the PNS
How many lobes are in the cerebrum of the brain?
4 lobes
- Frontal Lobe
- Temporal Lobe
- Parietal Lobe
- Occipital Lobe
What is the cerebrum?
Cerebrum: consists of the right and left cerebral hemisphere + 4 lobes (frontal, parietal, temporal + occipital)
What is the brainstem?
it is the final part of the brain before the spinal cord begins
What is the cerebellum?
- “little brain”
- posterior aspect of hte brain/brainstem
What are the 3 main divisions of the brain?
[1] Cerebrum
[2] Brainstem
[3] Cerebellum
What are the 3 parts that the brainstem is divided into?
[1] Midbrain
[2] Pons (latin for bridge, due to its shape)
[3] Medulla
What does the hindbrain consists of?
- pons
- medulla
- cerebellum
What is the function of the corpus callosum?
connects the right and the left hemispheres
What does the grey matter of the brain consist of?
- neural tissue that is grey in colour
- on the OUTER SIDE
- comprised of neural cell bodies (where the nuclei/ganglie in the brain)
- along with other connective tissue and immune cells
What does the white matter of the brain consist of?
- neural tissue that is white in colour
- on the INNER SIDE
- comprised of myelinated axons (which gives it its white colour
- along with other connective tissue and immune cells
Where is the cortex of the brain located? What is it made up of?
Cortex: the outer layer of the cerebral hemispheres
- composed of folds of grey matter
What are gyrus’ in the brain?
Gyrus: convex folds of grey matter
- “mountains” in the cortices of the cerebral hemispheres
What are the sulcus’ in the brain?
Sulcus: the concave folds of grey matter
- “valleys” in the cortices of the cerebral hemisphere
What are association fibres?
they are fibres that interconnect the cortical sites WITHIN one cerebral hemisphere
- “individual bits of the hemisphere”
What are the commissural fibres?
they are fibres that run from one cerebral hemisphere to the other
- e.g. corpus callosum
- between the right and left hemisphere
What are projection fibres?
they are fibres that pass from the cerebral cortex to the subcortical structures
- head south to the brain stem + spinal cord
What does ipsilateral mean?
it means on the SAME SIDE
What does contralateral mean?
it means on the OPPOSITE SIDE
What does decussate mean?
to switch from one side to the other
What is an example of decussation that occurs in the brain?
- from the cerebral cortex to cerebellum it decussates 2 times
- RIGHT CEREBRAL CORTEX supports LEFT SIDE of body
- LEFT CEREBRAL CORTEX supports RIGHT SIDE of body
- RIGHT CEREBELLUM supports RIGHT SIDE of body
- LEFT CEREBELLUM supports LEFT SIDE of body
What is the difference between cranial and spinal nerves?
Cranial Nerves: a set of 12 pairs of nerves the emerge directly from the brain (as distinct from spinal nerves)
- supplies eyes, smell, vision
Spinal Nerves: nerves that exit from spinal cord
- from below the brain stem
What are the 3 types of neurons?
[1] Afferent (Sensory)
[2] Efferent (Memory)
[3] Interneurons
What type of neurons are afferent neurons?
- sensory neurons
- A for Arriving
- message goes up to a higher centre
- 3 neuron pathways
What type of neurons are efferent neurons?
- motor neurons
- E for Exiting
- message comes down from higher centre
- 2 neuron pathways (upper + lower neuron)
How many neuron pathways do afferent neurons have?
3 neuron pathways
How many neuron pathways do efferent neurons have?
2 neuron pathways
What are interneurons?
they relay signals between afferent and efferent neurons
- the connecting bit
Are efferent or afferent neurons more complicated?
afferent (sensory) neurons are more complicated
What are the meningeal layers of the brain from inside to out? (include the spaces!)
[1] Pia Mater [2] Subarachnoid Space [3] Arachnoid Matar [4] Subdural Space [5] Dura Mater [6] Extradural Space
List the characteristics of the Pia Mater
- soft
- innermost layer
- very outer layer of brain tissue
- intimately connected with brain
What is found in the Subarachnoid Space?
the cerebral spinous fluid (CSF)
List the characteristics of the Arachnoid Mater
- middle layer
- thin, transparent tisue that covers the brain (most obviously visible where it overlies the sulci)
List the characteristics of the Dura Mater
- thick, fibrous connective tissue
- often more intimately associated with the skull
- forms partitions between the hemispheres
What is the trilaminar disc? What is it made up of? Explain what it is made up of.
It is an embryo which exists as 3 different germ layers:
[1] Ectoderm
- all epidermis + nervous system
[2] Mesoderm
- bone, muscle, connective tissue + dermis
- the “stuffing”
[3] Endoderm
- inner lining of the gastrointestinal tract + respiratory tract
What are the 2 places in the early embryo (14 to 16 days) in which the ectoderm and endoderm have a direct connection? (there is no mesoderm in between)
[1] Oropharyngeal Membrane
- anterior to the stomodeum
- gives rise to the MOUTH
[2] Cloacal Membrane
- posterior to the proctodeum
- gives rise to the ANUS
Explain the basic embryological steps involved in gastrulation (starting from bilaminar disc to formation of neural tube)
[1] bilayer embryonic disc is formed
- has 2 layers: epiblast + hypoblast
[2] Gastrulation occurs
- bilaminar disc differentiates to establish 3 germ layers
[3] Primitive Streak forms
- thickened structure forms in middle of epiblast near caudal end
[4] Primitive Node
- at the cranial end of primitive streak it expands
[5] Invagination occurs
- epiblast is pulled inwards towards the primitive streak
- hypoblast cells replaced
- mesoderm formed
[6] Notochord is formed
- from primitive node, prenotochordal cells migrate down the midline towards the cranial end
- the primitive streak degenerates + disappears
- derived from the mesoderm
- lies beneath the neural tube
What is the bilaminar disc? What is it made up of?
Bilaminar Disc is made up of 2 layers: epiblast and hypoblast
- epiblast associated with amnion
- hypoblast associated with primitive yolk sac
What is the notochord?
a cartilaginous rod, positioned dorsally and longitudinally
- lies underneath the neural tube
What is the neural tube?
a hollow structure from which the brain and spinal cord form
What do the neural crest cells contribute to?
[1] neurons + glial cells of the sensory (sympathetic + parasympathetic nervous systems)
[2] epinephrine-producing (medulla) cells of the adrenal gland
[3] pigment-containing cells of the epidermis
[4] many of the skeletal and connective tissue components of the head
When does the zipping process (of the neural tube) begin? When does the neural tube finish zipping and is completely closed?
Starts: Day 22
End: Day 27
- tube closes completely at cranial end 3/4 days later
- tube closes completely at caudal (tail) end 2/3 days later
When does the neuralation process fully complete?
zipping and closure of the neural tube is done around day 27
What does the broader end/region (cranial side) of the neural tube form?
it forms the brain
What does the narrower end/region (caudal side) of the neural tube form?
it forms the spinal cord
At the same time that the neural tube is forming, what is going on with the embryo?
folding of the embryo is occurring
What are the 3 main regions of the brain during development?
[1] Prosencephalon
- forebrain
[2] Mesencephalon
- midbrain
[3] Rhombencephalon
- hindbrain
What are the 2 main parts of the Prosencephalon?
[1] Telencephalon
- superiorly
- frontal love, parietal love, occipital love and temporal lobe
[2] Diencephalon
- inferiorly
- thalamus, hypothalamus (epi/subthalamus)
What is the telencephalon made up of?
[1] frontal lobe
[2] parietal lobe
[3] occipital lobe
[4] temporal lobe
What is the diencephalon made up of?
[1] thalamus
[2] hypothalamus (epi/subthalamus)
What are the 2 main parts of the Rhomboencephalon?
[1] Metencephalon
[2] Myelencephalon
What is the metencephalon made up of?
[1] pons
[2] cerebellum
What is the myelencephalon made up of?
medulla
What are somites? What are they made from? What do they form?
- paraxial mesoderm forms into definitive blocks of cells called somites on either side of notochord/neural tube
- forms the sclerotomes, myotomes and dermatomes
In what region does zipping begin and where does it extend to?
- zipping begins in the middle of the embryos back
- it extends cranially and caudally until zipped up
What does Spina Bifida an error in?
Spina bifida arises from an error of the zipping up of the neural tube
- it is a failed closure
What is neuralation?
the process by which the neural tube is formed (from the neural plate)
- aka zipping
What is meningocele?
- birth defect
- sac is protruding from the spinal column
- the sac includes spinal fluid, but no neural tissue!
What is meningoencephalocele?
- birth defect
- sac is protruding from the spinal column
- the sac includes spinal fluid and neural tissue (brain tissue)
