Nerve Tissue Flashcards
(19 cards)
What are the 3 different regions in an axon?
- Receptive Field - dendrites and the cell body (cell body = perikaryon/soma)
- Conducting Group - Axon hillock and axon (transmits the signal (the cable wire)
- Secretory Region - Axon terminal (releases Neurotransmitter)
What are the 3 different functions of neurons and their associated types
- Motor
- GSE - Somatomotor, multipolar (looks like your normal axon with cell body with multiple dendrites, one way axon, and axon terminal
- GVE - 2 somato motor neuron chains
- Sensory
- GSA and GVA
- Normally pesudounipolar (NO dendrites, 2 way highway with an axon hillock) or bipolar neurons (special sense neurons, NO axon hilock, cell body is in the axonal plan)
- GSA and GVA
- Integrative/Interneurons
What are 2 major histological features of a neuronal cell body?
- Euchromatic nucleus - expanded chromatin which is actively transcribing RNA
- Nissl Bodies - stacks of rER and ribosomes underingoing translation
- protein factories at work
Name 2 distinguishing features between DRG and Sympathetic chain ganglia?
- Centered nucleus (DRG) vs. polarized, off-centered nucleus (chain ganglia)
- Cell bodies are under more stress in SCG (producing more NTs in one direction?), whereas in DRG (cell body sends NTs to both ends of the axon, which makes it *less *stressful for cell body)
Name the 3 different kinds of dendrites?
- Unencapsulated - free nerve endings, common in EPT
- Nociceptors on fingertips
- Encapsulated
- Pacinian corpuscle - deep pressure; ONION shaped
- Meissner’s Corpuscle - light pressure, located within dermal papillae (finger-like projections of dermis
- Epithelial-cell associated - sensory epithelial cells that detect stimuli, and transmit signal to a nearby neuron
- Ex: taste buds
What are the 3 types of receptors associated with sensory neuron dendrites?
Exteroreceptors - external stimuli (skin, pain, touch heat
Enteroreceptors - internal stimuli (viscera, feeling full)
Proprioceptors - orientation in space
What happens during depolarization? What about hyperpolarization?
- Depol - Na+ channels open and membrane potential becomes more positive (0 to +20mV)
- Hyperpol - K+ channels open briefly causing an efflux of K+ out of the cell and cell becomes mometarly more negative
- Gradients maintained by Na/K ATPase
- 3 Na+ pumped out and 2 K+ pumped in
What are the 3 different classifications of the synapse, based, on where they synapse?
- Axosomatic - Synapse with cell body
- Axodendritic - synapse with a dendrite
- Axoaxonic - synapse with another axon
What are the 2 mechanisms of synaptic transmission. Describe the mechanism of action of each one
- Electrical
- Use connexons (ie Gap Junctions)
- More common in development, less so in adults
- Chemical
- Synpatic vesicle release at the bouton (terminal end of the axon) release NTs into synaptic cleft when calcium is released due to depolarization
- NTs bind to either ligand gated ion channels or G-protein coupled receptors (2nd messenger mechanism)
Describe 2 major NTs and their proportion of recycling vs. degradation
- Ach - released from skeletal muscle and ANS (minus NE at postG SNS)
- NE - released from postsynaptic neuron in SNS
80% recycled; 20% degraded by ach-ase
How does a vesicle dock onto the bouton?
- t-SNARE - target membrane SNARE
- v-SNARE - vescle SNARE
- T and V snares interlock and docking process is complete
- Ca++ influx enables NTs to be released via the fusion of the vesicle with the presynaptic membrane
What are the 2 main support cells in the PNS?
- Schwann Cell
- Schmidt Lanterman Clefts
- enable passage of nutrients from cell body to travel deeper into schwann cell folds (like icing btw folds on a cinnabon)
- Nodes of Ranvier
- Protein O - transmembrane protein associated with demyelinating diseases such as MS and Guillian Barre syndrome
- Schmidt Lanterman Clefts
- Satellite Cells
- Surrounding cells that are seen in DRG and SCG
What is the main function of astrocytes? How many types are there and how do they differ?
- 1 of 4 support cells in the CNS
- Similar to satellite cells in PNS
- Regulate :
- capillary blood flow via astrocyte feet
- Regulate NT levels in areas of high neuronal activity
- regulate ionic environment
- 2 types of astrocytes
- Protoplasmic (pictured)
- Usually associated with gray matter
- Takes over for pia mater to create BBB
- Fibrous
- Usually associated with white matter
- Have FEW connections with neurons and blood to regulate BBB
- 80% of adult brain tumors form from FAs
- Protoplasmic (pictured)
What are oligodendrocytes?
- Myelin secreting cells that will myelinate multiple axons by have fewer SL clefts
- will wrap multiple axons
What are microglia?
- Immune cells of the CNS
- they work to repair damaged neurons or phagocytize bacterial invaders
- Monocyte derived
What are ependymal cells
- Line the inside of ventricular system of brain and SC
- Have cilia to help circulate CSF
- Have microvilli to help absorb CSF
Describe the 3 different neuronal responses to injury?
- Anterograde (Wallwerian) Degeneration
- degeneration of axon DISTAL to the site of injury
- Traumatic Degeneration
- Retrograde degeneration BACK TOWARD the cell body
- Usually happens when injury is located in more proximal axon
- Chomatolysis
- Prelude to neuronal cell death; state of cellular stress, when neuron can either undergo “Sprouting” - regeneration - or cell death
What is the major factor in whether neuronal cells can regenerate or not?
- In PNS, there are lots of WBCs to clear up when nerve is damaged
- WBCs (m-phages) can chew through myelin rapidly and allow axon to regenerate
- Sprouting is more common in PNS
- In CNS, microglia are unable to clear damaged neuronal debris effectively. Why?
- Oligodendrocytes prevent microglia from cleaning of damaged tissue
- Immunopriviledged because of BBB
Glial cells in action
