L14. Nerves Part II Flashcards
What is a ganglion?
it is a group or cluster of nerve cell bodies :
-nucleus ( CNS)
-ganglion (PNS)
synapses are present in both
What is an autonomic ganglion
A cluster of nerve cell bodies and their dendrites, the synapse/junction is between the spinal cord and the autonomic innervation of the target organ
Sketch a diagram showing stomach (autonomic innervation)
L12 pg 2b
What is the function of the neurofilaments?
provide structural backbone for dendrites and axons
What is the function of microtubules in the nervous system?
Transport mitochondria and neurotransmitter containing vesicles
What is the function of the smooth ER in the nerve cell
- extends from the soma to the axon terminal
- occassionally associates with the axon or vesicular membranes
- SER contains molecules and building blocks for membrane assembly
Describe the process for synaptic transmission
- vesicles are transported down the axon
- vesicle is loaded
- depolarization occurs
- exocytosis
- binding of the NT to the ligand
- depolarization occurs at the post synaptic vesicle
Draw the synaptic transmission from the pre-synaptic cell to the post synaptic cell
(pg 5a)
Name what are the structures present in the cell body
nucleus, RER, mitochondria, golgi
Name what are the structures present in the axon
mitochondria,SER, microtubules and neurofilaments
Name what are the structures present in the terminal of the nerve cell
synaptic vesicles and mitochondria
What do additional cell types do for the nerve cells?
maintain the internal environment ( homeostasis)
contribute or assist in the process of neurotransmission
What are the types of glial cells that maintain homeostasis
- Schwann cell and oligodendrites
- astrocytes and microglia
- ependymal cell
What is a neuron
It is the basic unit of transmission in the CNS
What are the functions of glia cells
- non-conducting
- enhance neuro-transmission
- biochemical (speed up impulses)
- structural support (physical support)
- nutritive (growth and maintenance)
- immune (clear debris, scavenge toxins)
Draw how the action potential relates with sodium and potassium channels
pg 8b
What forms the myelin sheath
glial cells that wrap around the axon
What is the advantage of having the myelin sheath
Myelination speeds up nerve impulses through having nodes of Ranvier ( promotes saltatory conduction)
Compare the difference between myelinated and unmyelinated neurons
myelinated neurons: - faster impulse velocity -less leaky (efficient conduction) - less energy consumption unmyelinated neurons: -leak Na+ -slower impulse conduction -channels are open along the entire length
Under what circumstances do we need heavy myelination?
- high impulse velocity
- motor (conscious reactions)
- sensory ( acute pain)
Under what circumstances do we need moderate to un-myelinated neurons?
- need slower impulse velocity
- motor (unconscious targets: autonomic)
- sensory (chronic pain)
What do Schwann cells do?
- occur in the PNS
- wrap around axons to form myelin sheath
- 1 Schwann cell per 1-2mm segment of 1 axon
- forms discontinuous nodes of ranvier
Draw how a myelinated schwann cell looks like
pg 11b
Draw how a unmyelinated schwann cell looks like
pg 12a
Describe how the un-myelinated axon looks like
- axon is not completely swallowed by schwann cells
2. axons communicate with the EC space
What are oligodendrocytes (OL)
- same function as schwan cells
- increases the impulse velocity
- capable of contracting greater than 60 nerve axons
What are the functions of astrocytes
- contact blood vessels and regulate blood flow
2. scavenge ions to nutrify neurons
What is the difference between protoplasmic astrocytes and fibrous astrocytes ( draw difference)
- protoplasmic occurs in grey matter
2. fibrous astrocytes occurs in white matter
What is GFAP?
glial fibrillary acidic protein- it is a protein found in the cytoskeleton of glial cells that can be stained by antibodies
What is the function of microglial?
- patrol brain and shield it from injury
- continually extend and retract their processes
- stimulated by the release of chemo-attractants
- processes move towards site of injury
cell types in the CNS are… name their functions
- oligiodendrocytes: myelination
- fibrous astrocytes+protoplasmic astrocytes: BBB to repair and nutrify
- microglial: immune scavengers
- ependymal cells: BBB/CSF production
What are the 3 connective tissue coverings in the PNS?
- epinerurium
- perineurium
- endoneurium
Draw the connective tissue coverings with Schwann cell and single nerve axon identified
pg 16a
What causes meninges?
- inflammation of coverings in brain and spinal cord
- curable
What are the 3 connective tissue coverings in the CNS ( which is closest to the skull, which is closest to the brain)?
- dura mater (closest to skull)
- arachnoid mater
- pia mater (closest to brain)
Draw the coverings
pg 17a
How is brain homeostasis achieved?
- capillary endothelium
- tight lining of blood vessels
- maintains BBB - ependymal cells
- continuous lining of the brain
- synthesize,secrete, excrete CSF
- maintain blood-CSF-brain barrier
What is the difference between capillary endothelium in neural and non-neural capillaries?
- neural capillaries have a lot more tight junctions, non-neural capillaries have lots more pores
- neural capillaires restricts large molecules,non-neural capillaries are thinner and less restrictive
What are the characteristics of capillary endothelium in neural environments?
- many large Blood borne molecules do not cross the CNS
- still penetrable through:
- astrocytes contact with blood vessels
- lipid soluble substances free to pass (eg.alcohol)
- water soluble substances can gain access via membrane bound pumps to produce CSF
What is the function of the ventricular system in the brain?
- has 4 cavities
- spans entire CNS
- circulates CSF at 14-36mls/hr
- contains NT, waste materials and nutrients
What is the function of choroid plexus?
- acts as a barrier
- actively transports small molecules
- synthesizes and secrete CSF
- simple cubodial epithelium
What is the function of the arachnoid vili?
- allows CSF to exit the brain and enter the venous system
- protrude into venous cavities
- pierce through dura mater ( 1st CT layer around CNS closest to skull )
Label CSF circulation diagram (arachnoid vili,choroid plexus etc)
pg 22b
What is white matter?
collection of myelinated axons
tracts in spinal cord and brain
What is grey matter?
collection of nerve cell bodies
horns (spinal cord)
cortex in brain
Where is the grey and white matter located in brain
white: within head
grey: outside head
(vice versa for spinal cord)
multiple sclerosis
- primary destructve loss of central myelin
- death within months -years of onset
- incidence ~50/100000
- disease rate follows geographic gradient
ALS (amyotrophic lateral sclerosis)
- loss of motor cells and muscle atrophy
- death within2-6 years
- 3-7/100000
- loss of myelin
