Module 1/2 - Structure and development of the nervous system and cells of the nervous system Flashcards
Why do we have a nervous system?
To react to in response to stimuli around us
Difference between invertebrate and vertebrate brains
Ventral nerve cord compared with a dorsal cord in vertebrates
Divisions of the brain
Spinal cord - spinal cord
Hindbrain - Pons, Medulla
Midbrain - Tectum, Tegmentum
Forebrain - Diencephalon (Thalamus, Hypothalamus) and Telencephalon (Cortex, Olfactory bulb)
Three layers of cells
Endoderm, mesoderm, ectoderm
Endoderm
The lining of the organs, and tracts (innermost layer)
Mesoderm
Forms bones and cartilage (the middle layer between the endoderm and ectoderm)
Ectoderm
Outermost layer (skin, hair, nails) and the nervous system
The neural tube: what is it formed from and what happens with the nervous systems?
Formed by the folding of the neural plate
CNS is formed from the walls of the tubes and PNS is formed from the neural crest
Spina Bifida: what is it, what is the treatment, and what may influence its occurrence?
The failure of the posterior neural tube to close
Supplementing the diet with folic acid reduces the likelihood of it happening by 90%
Antiepilepsy and antibipolar drugs may interfere with embryo metabolism and influence Spina Bifida
Ventricles: what are they in the brain and what do they do?
Four cavities filled with cerebrospinal fluid
They act as a cushion for the brain, remove waste and maintain chemical stability
The spinal cord: what are the things near it and what do they do, what does the spinal cord do, what do the dorsal roots mostly contain, and what do the ventral roots mostly contain?
Protected by the spinal column and surrounded by meninges and cerebrospinal fluid
The spinal cord transmits messages from the brain to the periphery and acts as the primary channel for messages from the skin, joints, and muscles to the brain
Dorsal contains sensory and afferent neurons
Ventral contains motor and efferent neurons
Parts of the spinal cord
Dorsal root ganglion, dorsal root, ventral root, grey matter (neuron cell bodies), white matter (myelinated axons), central canal, and anterior commissure
Brainstem: what is it and what does it contain?
The oldest part of the brain which acts as a decision matrix and controls vital processes
Midbrain (controlling movement and sensory input (eyes, ears)), and some parts of the Hindbrain (Pons and Medulla)
Pons: where is it located and what does it do?
Swells out from the ventral surface of the brain stem and is important in the relay between the cortex and cerebellum
Medulla: where is it located and what does it do?
The bottom part of the brain, below the Pons and the cerebellum.
Important in blood pressure and ventilation control.
Hydrocephalus: what is it and what does it do?
Brain stem damage, may cause damage to the Medulla and therefore respiratory arrest
Cerebellum
A part of the brain you can live without. It affects motor functions and it has extensive connections to the cerebellum and spinal cord (at least as many as both hemispheres)
Affected by alcohol and Ataxias. Those suffering from Ataxias may be perceived as drunk because motor issues occur in either situation
Cerebral cortex: what is it, what does it do, and what are the key facts about its evolution?
The layer above the cerebrum (including both hemispheres) which controls voluntary actions, cognition, and perception awareness.
- Mammals have a more complex 6-layer structure (neocortex)
- Number of neurons related to ‘intelligence’
- Although they may have different sizes, they’ll have the same general structure
The four lobes of the cerebral cortex
Frontal - at the front
Parietal - to the right of the frontal, above temporal
Occipital - to the right of temporal, below parietal
Temporal - above the spinal cord, left of cerebellum
The frontal lobe: what does it do?
Control actions, motor, speech control, and emotion
The Parietal lobe: what does it do?
Sensory and language
The Occipital lobe: what does it do?
Memory, sensory, language
The Temporal lobe: what does it do?
Visual
Golgi and the reticular theory
Golgi discovered a silver stain allowing neurons to be viewed, his findings led him to believe that neurons fused together
Cajal and the neuron doctrine
Using Gogli’s stain, he concluded that neurons were distinct cells that communicated by contact and they only sent information to other neurons
Confocal microscopy
The basic principle of confocal microscopy is that the illumination and detection optics are focused on the same diffraction-limited spot, which is moved over the sample to build the complete image on the detector
Why do neurons not fall apart despite not having connective tissue?
Neurons are supported by a cell type known as glia
Glia are cells that can divide unlike neurons have the primary job of supporting the nervous system but may also have their own role in signalling
Astrocytes: what are they?
Star-shaped cells that are the main type of glia which fill the space between neurons and regulate the composition of extracellular fluid
Can also play an important role in the differentiation and proliferation (increase) of neurons
Oligodendrocytes: what do they do?
Myelinate axons on neurons in the CNS
Schwann cells: what do they do?
Myelinate cells in the PNS
Microglia: what are they and what do they do?
Type of migrating glial cells that act as brain scavengers with phagocytic/immune function
Ependymal cells: what are they and what do they do?
They have cilia and their structure resembles epithelial cells with an important role in the production of cerebrospinal fluid
Axons features: physiological, organelles, structural, specialisations, and myelination?
Propagate information, synaptic vesicles, long and untapered and branch at 90°, terminal, and often
Dendrite features: physiological, organelles, structural, specialisations, and myelination?
Receive information, soma (containing the cytosol), short and tapered and branched, dendritic spines, and none
Cystolic organelles
Dendritic organelles:
* Peroxisomes, mitochondria
* Ribosomes
* Vacuolar apparatus (secretory/endocytic pathway):
ER endoplasmic reticulum, secretory vesicles, Golgi complex, endosomes
Axon organelles:
* Synaptic vesicles
* Mitochondria
* Smooth ER
Membrane differences between axons and dendrites
Dendrites:
Ca²⁺ channels
GPCRs
Ligand-gated ion channels
Axons:
Na⁺ and k⁺ channels along the axon
Ca²⁺ channels (terminal)
GCPRs (terminal)
How does axon/dendrite targetting work?
Mechanism unclear
The role of the neuronal cytoskeleton
- Structural support – shape and calibre of axons and dendrites
- Transport cargo to and from axons and dendrites
- Tethering of components at the membrane surface
Microtubules in the neuron: what do they do, what are their key features, and what does the moving?
Run longitudinally down axons and dendrites, aiding structural and Transport
- Big, 20 nm wide, tubulin polymers
- Polymerisation/Depolymerisation – shape change
Microtubule Associated Proteins e.g. MAP-2, Tau, Kinesin (moves down towards the terminal axon) & Dynein (moves back up from the axon to the dendrites)
Neurofilaments in the neuron: what do they do and what are their key features?
Mechanical strength
10 nm wide filamentous protein threads
Microfilaments in the neuron: what do they do and what are their key features?
Mediate shape change
- 5 nm wide, actin polymers
- Tethered to membrane
Types of neurons
Sensory (afferent; somatic or visceral) neurons originate from sensory receptors to the ‘processor’
Motor (efferent; somatic or visceral) neurons conduct signals that originated in the CNS
Interneurons are between sensory and motor neurons
Decussation
Two things crossing over in an X shape (ie eyesight)
What treatments are there for Alzheimer’s disease
- Small molecule drugs which act as acetylcholinesterase inhibitors (donepezil, galantamine)
- Preventing excessive glutamate transmission (N-methyl-D-aspartate (NMDA) receptor blockers)
What are the differences in brains with Alzheimer’s and without it: β amyloid, tau, microglia activation, and synaptic function/density?
β amyloid - increases
Tau - increases
Microglia - increased activation
Synaptic function/density - decreases
Lecanemab: what is it, what can it be treated for and how may it do this?
A monoclonal antibody obtained by a mouse antibody
Treating AD
Preventing excessive β amyloid deposition
