Nervous Tissue Structure + Function Flashcards
What is the Central Nervous System?
The brain and spinal chord
What is the Peripheral Nervous System?
Cranial nerves and spinal nerves
Where is Grey matter found?
Peripheral in the brain in area called “nuclei”
Central in spinal chord (H/butterfly region)
What does grey matter consist of?
Nerve cell bodies Dendrites Axon terminals Non-myelinated axons Neuralgia (support cells)
Where is white matter found?
Central in the brain
Peripheral in spinal chord
What is white matter made of?
Myelinated material
Describe a cross-section of spinal chord.
Grey matter looks like a butterfly
Have dorsal horn and ventral horn-connected by grey commissure
White after contains fibres that form the acsending and descending tracks.
What is the basic structure of a Neuron?
Normal cell organelles
Cytoplasmic projections-one axon, many dendrites
Main body (soma), dendrites and proximal axon in CNS
Distal axon + arborists ions in the PNS
Often myelinated
What’s the difference between myelin in the CNS and PNS?
In CNS made from oligondedrocyte
In PNS made from Schwann cell
Describe location + function of motor neurone and any special structures.
Location=CNS to periphery
FUnction=send signals to effector tissue
Structure= if cell body is outside the CNS it forms a ganglia
Describe location + function of Sensory neurone and any special structure.
Location=periphery to CNS
Function=send environmental signal to integrative centre
Structure=a bipolar neurone has the cell body in the middle, a pseudounipolar neuron has the body to one side of the axon.
Describe the function and location of an intergrative neurone, and any special structures.
Location=CNS
Function=Collate all info
Structure=pyramidal cells have a pyramid shap cell body, interneurons have pre and post synaptic neurones, purkinjie cells have many many dendrites into 1 axon.
Describe the location and function of an anaxonic neurone and any special structures.
Location=retina (some parts of CNS)
Functions=Act as relays between nerve cells, they can hold the info for a period
Structure= cell body in centre and many dendrites
What neurones are located outside the CNS?
Pseudounipolar, bipolar and postsyynaptic autonomic neurone cell bodies are outside CNS
How are vesicles moved from the soma (cell body) to the synapse and back?
Anterograde (away from soma) and retrograde (to the soma) vesicles use microtubule “shuttle” system too move from soma to synapse and back. The microtubules can also transport mitochondria, but these don’t return
How can you tell if a vesicle is immature?
It only contains enzyme in its membrane, no neurotransmitter etc.
How does an immature vesicle develop?
As it travels the length of the axon it synthesis the neurotransmitter.
Transported using microtubules
What are the 2 possible fates of a vesicle?
1) Recycled through Cathrin-coated endocytosis (removes plasma membrane from hillock to make vesicle)
2) Lost to the neurolemma
List the different types of synapse and why they are classified as such.
Axodendritic-connect directly to plasma membrane of nerve/cell
Axodendritic or dendodendritic -axon terminal synapses with dendritic spine, fit to mould around spine for better neurotransmission
Axoaxonic-synapse at axon is bouton, the axoaxonic synapse may enhance/inhibit the axodendritic synapse
Axo-axonal-impinging another synapse, usually inhibits other outputs
What are the connective tissue layers in peripheral layers and what does each surround?
Endoneurium=loose connective, surrounds single nerve cells
Perineurium=specialised connective (transport proteins), maintain ionic composition, surrounds axon cluster/fascicles
Epineurium=dense irregular connective, separates diff nerve types and fills space between fascicles
Paraneurium=fascia that separates nerves from surrounding tissue
What does neurone diameter have to do with transmission speed?
Smaller diameter=slower signal
Larger diameter=faster signal
How do Schwann cells connect unmyelinated neurones?
Connect a few into a bundle.
The Schwann cell is in the centre
Has clefts along the side to allow fluid to pass through
How does myelination effect conduction?
The more myelinated a cell the faster conduction as it is saltatory. The distance between nodes of ranvier is larger in large diameter axons and so conduction is faster as the current jumps further
How do Schwann cells perform myelination?
1) The axon sitting in a groove is surrounded by a Schwann cell
2) The mesaxon membrane initiates myelination by surrounding the embedded axon
3) a sheet-like extension of the mesaxon membrane then wraps around the axon, forming multiple membrane layers
4) cytoplasm is extruded form between the two apposing plasma membranes of the Schwann cell, they then become compacted to form myelin.
How does an Oligodendrocyte perform myelination?
Same way as Schwann cell but in the CNS.
Cytoplasmic processes from the oligodendrocyte cell body form flattened cytoplasmic sheaths that wrap around each of the axons.
The relationship between cytoplasm and myelin is same as Schwann cells
HOWEVER=oligodendrocytes wrap around more than one axon simultaneously
What relationship do unmyelinated nerve cells have with Schwann cells.
Individual axons are engulfed by the cytoplasm of a Schwann cell. Propagation of APs are slow
List the 4 support cells in the CNS
Oligodendrocytes
Astrocytes
Microglial cells
Ependymal cells
(All very small compared to the nerves)
What is an Astrocyte and what is its role?
Star-like structure
Have “perineural feet” that contain gap junctions (biochem support for endothelial cells, transport nutrients form blood to nerve)
Regulate nerve impulses by releasing glutamate near node of ranvier
Contribute to blood brain barrier (capillary is covered in feet, blood cant get out)
What is a Microglial cell and what is its role?
Large cells with elongated nucleus and relatively few recesses emanating from the cell body
Found throughout CS
Resident macrophage (immune function, remove damaged nerve cells, sense increased K+ ions and move toward it)
Also thought to digest the protien tangles related to dementia/Alzheimer’s
What are ependymal cells and what is their function?
Line the spinal cord
Derived from neural crest, made of neural tissue
Look like columnar epithelial cells lining spinal canal and brain ventricles, have cilia and microvilli
Joined by a junction complex
Synth and secrete CSF in ventricles
Cilia move CSF through ventricles to spinal cord
Microvilia absorb CSF to remove pathogens and present them
Modified tight junctions control fluid release to brain
What is multiple sclerosis?
Remitting+relapsing diseases
Degenerative
Autoimmune degradation of myelin
Symptoms=fatigue, vision problems, slurred speech, numbness, tingling, mobility issues, urinary incontinace, constipation