S11 Nervous System Flashcards
What two areas form the nervous system?
- CNS
2. PNS
What type of reaction is the knee jerk reaction?
An unconditional reflex
Where does the parasympathetic system arise from?
Nuclei found in brain stem and sacral region of the spinal cord (S2-S4)
Where does the sympathetic nervous system arise from?
Nuclei found in thoracolumbar region of spinal cord (T1-L2)
Out of the cranial nerves, which number is the vagus nerve?
10 (X)
Where do the sensory neurones have cell bodies?
In the dorsal root ganglion
What does anterograde transport, transport down the nerve?
Empty secretory vesicles and mitochondria
What are Nissl bodies composed of?
Polyribosomes and RER
What happens to synaptic vesicles at the presynaptic membrane?
They fuse with the presynaptic membrane
What is the CNS composed of?
Brain and spinal cord
Contains relay neurons/interneurons
What is the PNS composed of?
Cranial, spinal and peripheral nerves
Contains sensory and motor neurons
What is the grey and white matter distribution in::
- The brain
- Spinal cord
- Grey - peripheral, white - central
2. Grey - central, white - peripheral
What does grey matter contain (5 items)?
- Nerve cell bodies
- Dendrites
- Axon terminals
- Non-myelinated axons
- Neuroglia (support cells)
What does white matter contain?
Myelinated material
What parts of the neuron are in the CNS?
The cell body, dendrites, Nissl bodies ogliodendrocytes (and accompanying myelinated axon), proximal axon
What parts of the neuron are in the PNS?
Distal axon, Schwann cells (and associated myelin), motor end plate, muscle/target tissue, nodes of Ranvier
What is another name for the main cell body?
Soma
What are the four types of neurons?
- Motor
- Sensory
- Integrative
- Anaxonic
What are the types of sensory neurone? Are they in the CNS or PNS?
- Pseudounipolar neuron
- Bipolar neurone
PNS
What are the types of motor neurones?
- Large motor neurone
2. Pre and post synaptic autonomic neurons
Is the postsynaptic autonomic neuron (motor neuron) in the CNS or PNS?
PNS
What are the types of integrative neurons? Are they found in the PNS or CNS?
- Pyrimidal cell
- Interneurons (relay neurons)
- Purkinje cell
CNS
Describe the structure of pyrimidal and purkinje cells?
Many dendritic arborisations
What does the psuedounipolar neurone look like?
Cell body isn’t with dendrites - cel body is further along neurone (protrusion from axon)
What is the structure and function of anaxonic neurons?
Many dendrites but no axon
Help in visual processes (found in retina)
What is the structure of multipolar neurons?
One axon, many dendrites
Most common neuron types
What is the structure and location of bipolar neurons?
One axon, one dendrite
Found in olfactory cells, retina, inner ear
What is the structure and function of unipolar neurons?
Single process leading away from the soma
Sensory from skin and organs to spinal cord
What would you see lots of if looking at a neuron in the CNS through a micrograph?
- RER
- Golgi apparatus
- Free ribosomes
What are the proteins in anterograde transport?
Kinesin and microtubules
What are the proteins in retrograde transport?
Dynactin and microtubules
Which direction is anterograde transport?
From cell body (soma) to synapse
What direction is retrograde transport?
From the synapse to the cell body (soma)
What does retrograde transport transport?
Vesicles
What are microtubules part of?
The cell cytoskeleton
What do immature NT vesicles contain in its membrane?
Enzyme
When does NT synthesis occur in the vesicle?
As it travels the length of the axon
What are the two fates of the NT vesicle?
- Recycled by endocytosis
2. Lost to neurolemma
What happens to NT when it separates from receptors in postsynaptic membrane?
- Reuptake of NT
2. NT recycled (repackaged and remains at presynaptic terminal or broken down into precursor)
What happens to empty vesicles at the presynaptic terminal?
Transported back by retrograde transport
What are the 5 different types of synapse?
- Axodendritic or axosomatic (directly to plasma membrane of nerve/cell
- Axodendritic (synapses with dendritic spine)
- Axoaxonic (synapse at axonic bouton)
- Dendritic-dendritic (dendrite to dendrite synapse)
- Axo-axonal
What is the name of the new model of NT release?
Porocytosis
What are the separations of peripheral nerves by CT?
- Endoneurium - around single nerve cell
- Perineurium - around fascicles (clusters of nerve cells)
- Epineurium - around all fascicles (separates different nerve types)
- Paraneurium - separates nerves from surrounding structures
What does myelin look like on a micrograph?
Darker than if no myelin
What are Schmidt-Lanterman clefts?
Small amounts of Schwann cell cytoplasm
What is the intermodal distance?
Distance between Nodes of Ranvier
When is the intermodal distance bigger?
In larger diameter axons
How does myelination occur?
- Axon surrounded by Schwann cell
- Mesaxon membrane of Schwann cell initiates myelination by surrounding axon
- Sheet-like extension of mesaxon membrane wraps successively around axon, forming multiple membrane layers
- Cytoplasm is between plasma membranes of Schwann cell
- Compaction occurs
What is the main difference between Schwann cell and ogliodendrocytes in myelin formation?
Ogliodendrocytes wrap around more than one axon simultaneously
What are the support cells in the CNS (4 cells)?
- Ogliodendrocytes
- Astrocytes
- Microglial cells
- Ependymal cells
Describe the structure and function of astrocytes.
‘Star-like’ structure
Regulate nerve impulses by releasing glutamate
Contribute to blood-brain barrier (‘perineural feet’ - contain gap junctions)
Perineural feet gap junctions also help support endothelial cells
Describe the structure and function of microglial cells.
Large cells with elongated nucleus and few processes from cell body.
Macrophages - immune response, remove damaged nerve cells, sense K+ conc
(May digest protein tangles associated with senile dementia and Alzheimer’s?)
Describe the structure and function of ependymal cells.
Line the spinal cord
Look like columnar epithelial cells lining spinal canal and ventricles of the brain
Joined by a junctional complex
Apical surface has cilia and microvilli
Synthesis and secrete cerebrospinal fluid (CSF) in ventricles - cilia move CSF through ventricles to spinal cord, microvilli absorb CSF for removal of pathogens, modified tight junctions between epithelial cells control fluid release into brain
What are some symptoms of MS?
Fatigue, vision problems, slurred speech, numbness and tingling, mobility issues, urinary retention, constipation
What is MS?
A degenerative autoimmunity disease caused by the degradation of myelin (maybe against EBV?)
What are the two parts of the autonomic nervous system?
Sympathetic and parasympathetic
Describe the length of the pre- and post-ganglionic nerves in the sympathetic and parasympathetic nervous systems.
Sympathetic - pre is short, post is long
Parasympathetic- pre is long, post is short
Describe the 3 sympathetic nervous system distribution routes to the skin
- Synapse at the level of entry - supplies dermatomes at T1-L2 levels. Postganglionics gets to targets through T1-L2 spinal nerves.
- Ascend the chain, then synapse - supplies head and neck. Postganglionics gets to targets along walls of blood vessels.
- Descend the chain, then synapse - supplies lower limbs. Postganglionics get to targets through the spinal nerves at levels L3 and below.
Describe the sympathetic nervous system distribution to the abdominal viscera.
- Preganglionics can transverse the chain then synapse at pre-aortic ganglion to supply abdominal viscera. Postganglionics get to targets along blood vessels.
- Sensory fibres can also travel along sympathetics destined for the abdomen and relay pain from the viscera to the CNS
What is the axon type if it is surrounded by Schwann cells but the cell hasn’t coiled itself around the axon?
Unmyelinated
What is a ganglion?
An accumulation of neuron cell bodies outside the CNS
What is the structure of ganglion cells of sensory nerves?
Round with large ovoid nuclei with prominent nucleoli.
Each cell is surrounded by satellite cells (muscle stem cells).
Psuedounipolar cells that give rise to a single myelinated process which branches into a dendrite from PNS and axon to the CNS
What is the cerebrospinal ganglia structure?
Cell bodies grouped at periphery of ganglion, fibres grouped in the middle.
Easy to distinguish from autonomic nervous system ganglia structures.
What is the structure of autonomic ganglia?
Ganglion cells are small and multipolar with several dendritic processes and unmyelinated axons.
Capsule and satellite cells present in layer around cell bodies.
