chapter 15 nervous tissue Flashcards
1
Q
What are the charcteristics of nervous tissue?
A
- Irritability
- Specialized to recieve stimuli
- COnductabiltiy
- transmist nerve impulses
- cellular componets
- neurons - conduct impulses
- fundamental structural and functional unit of NS
- Neuroglial cells
- non conductive cells that support and protect neurons
- parts of neuron
- cellbody (soma)
- dendrites
- axon
- neurons - conduct impulses
2
Q
What is the cell body (soma)?
A
- contains nucleus
- Nissl bodies (substances) consists of RER and free ribosomes
- Extensive RER visible with light microscopy and elaborate golgi structures
- abundunt mitochondria, microtubles, and intermediate filaments (neurofilaments )
- Lipofucsin granules are formed from lysosomes and accumulate with age of the neuron
- associated with ligand gated channels and local potentials
3
Q
What are dendrites?
A
- Connduct impulses (local potentials) toward the cell body
- Contain Nissl Substance, mitochondria, and ect. but NO GOLGI BODY
- may be studded with dendritic spines to increase sa
- tend to taper distally and may branch
- assocated with ligand channels
4
Q
What is an axon hillock?
A
(part of the axon)
site for origin of the axon
devoid of nissl substance
associated with action potential generation
5
Q
What is axon
A
- Assoc. with volt. gated ion channels and AP
- Contain mito chondria and microtubles
- but lack RER, Ribosomes, and Golgi
- terminates in branching telodendrites
- telodendrites contain synaptic vesicles and related proteins
- form presynaptic vescles
- may be enclosed in myelin sheath
6
Q
structure of axon pic
A
7
Q
structure of axon pic
A
8
Q
How are nerve cells classified on function?
A
- Sensory (afferent)
- To CNS
- Motor (efferent)
- Exit CNS
- Somatic
- skeletal
- automatic
- glands, cardiac, smooth
- divided in to parasymp and sympathetic neurons
- INterneurons
- transmit impulses within CNS and b/w sensory and motor neurons
- most abundant class
9
Q
how are nerve cells classified on processes?
A
- multipolar neurons
- most common
- single axon and multiple dendrites
- bipolar
- two processes, one at each end of spindle shaped neuron
- in association of special senses such as olfactory and visual
- pseudounipolar
- single process from the cell body that bifurcates into a central and a peripheral process
- found in ganglia alongside spinal cord (dorsal root gangila )
10
Q
How are neurons classified according to length?
A
- Golgi 1
- neurons with long axons which leave the gray matter of which thye are a part of
- Golgi 2
- Neurons with short axons which ramify through the gray matter
11
Q
what is this?
A
12
Q
what is this?
A
13
Q
What is a nerve?
A
a bundle of axons (fibers) in the PNS
14
Q
What is a tract?
A
A bundle of axon (fibers) in the CNS
15
Q
What are ganglion?
A
An aggregation of cell bodies and dendrites in the PNS
16
Q
What is a nucleus?
A
A aggregation of cell bodies and dendrites in the CNS
17
Q
What is the micro architechure of the nerve?
A
-
Epineurium
- thick fiborus coat
- covers entire nerve
- cupplied by blood and lymphatic vessels
- type 1 collagen and fibroblasts
-
Perineurium
- dense CT
- covers bundles of axons (fasiciles) within nerve
- Epithelial like fibroblasts on inner surface joined by tight junctions
- zonulae occuldens
- provide permiability barruer
- layer must be regjoined in micro surgery for limb reattachment
-
blood nerve barrier
- Endothelial cells of vessels also linked by tight junctions
-
Endoneurium
- thin layer of recticuar CT
- surrounds indivdual dibers and schwann cells
- type 3 collagen
18
Q
What is the membrane specializations on a nerve?
A
- Receptors
- ion channels
- ligand gated channels on dendrites and cell bodies
- potassium channels on axon
- voltage gated sodium channels on axon
- voltage gated calcium channels on axon
- Presynpatic membrane
- synaptic vesicles
- vesucular docking protins and synapsin filaments
- Post synaptic membrane
- receptors
- ligand gated ion channels
19
Q
microstructure
A
20
Q
microstructure
A
25
Q
What are the functions of astrocytes?
A
- Regulate composition of intercellular environments or entry of substances into it
- Structural support
- blood-rain barrier
- mediate exchange of nutrients and metabolites between blood and neurons
- end feet form glia limitans
- Development of cerebral cortex
- potassium sink
- secretion of neurotrophic factors
- uptake/metabolism of neurotransmitters
- help forms non collagen scar tissue after injuy to CNS
26
Q
what is this tissue
A
27
Q
What is this tissue
A
33
Q
How does myelination ocur in the PNS?
A
- Schwann cell plasma membrane wraps around axon
- schwann cell cytopasm is squeezed out leaving behind concentric layers of membranes
- internal and external mesaxon
- outer and innermost points of fusion between the outerleaflets (extracellular leaflets )
- internal and external mesaxon
- intraperoid lie
- eletron dense line created by extracelllar space between adjacent outer leaflets
- major protein zero is a transmembrane protein that forms homodimers
- found in the PNS
- homodimers form homotetramers with the opposing outer leaflets
- mutation are related to charcot-marie-tooth diseases
- In CNS version of this protein - mutation result in pelizaeus merzbacher disease
- major protein zero is a transmembrane protein that forms homodimers
- eletron dense line created by extracelllar space between adjacent outer leaflets
- Major Dense line
- e dense line created by cytoplasmic space remnant between adjacent inner leaflets
- myelin basic protein ( also in PNS) is an abundant protein assocated with the inner leaflets
- stablized lipids in leaflets
- there are a number of forms created by splicing of a single gene
- Schmidt- lanterman clefts ( incisures)
- residual areas of cytoplasm within the major dense lines
37
Q
What are meninges and how are they listed from superficial to deep?
A
- Superfical to Deep
- Epidural space (absent around brain)
- Dura mater
- Subdural Space
- Leptoemninx
- Archnoid membrane
- Archnoid villi Pia Mater
45
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47
Q
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