L18: Nervous Tissue II Flashcards
1
Q
Anatomical divisions of nervous system
A
- CNS: brain and spinal cord
- PNS: cranial nerves (12 pairs), spinal nerves (31 pairs), plexuses, ganglia (cranial, spinal, autonomic)
2
Q
Gross anatomical divisions within the brain
A
- Gray matter (cerebral/bellar cortex, nuclei) = cell bodies and neuroglia
- White matter (tracts, fasciculi etc.) = cell axons and neuroglia
3
Q
Where are cell bodies located in the PNS?
A
- Ganglia (cranial, spinal, autonomic)
4
Q
Where are axons located in the PNS?
A
- In nerves
5
Q
Where are cell bodies located in the CNS?
A
- Gray matter (cerebral cortex, cerebellar cortex, nuclei)
6
Q
Where are axons in the CNS located?
A
- White matter (tracts, fasciculi, lemnisci, commissures, brachii, peduncles)
7
Q
Functional divisions of the nervous system
A
- Voluntary nervous system: somatic motor: innervation and control of skeletal muscles
- Involuntary nervous system: visceral motor: ANS (SNS thoracolumbar T1-L2/3, PSNS craniosacral – both innervate and control smooth, cardiac muscle and glands) and ENS (controls peristalsis, gland secretions, blood flow through GI)
8
Q
What is a synapse?
A
- Junction between a neuron and a neuron, muscle cell or gland cell
- Site where an action potential is transmitted from cell to cell
9
Q
Morphological types of synapses
A
- ) Axodendritic (most common)
- ) Axosomatic
- ) Axoaxonic (less frequent)
10
Q
Functional types of synapses
A
- ) Electrical (in cerebral cortex, brainstem and retina; have gap junctions, impulse is rapid)
- ) Chemical (most common, associated with NTs)
11
Q
Describe morphology of chemical synapses
A
- ) Presynaptic component
- Consists of presynaptic membrane, mitochondria, sER, synaptic vesicles containing NT and presynaptic densities (cone-shaped structures representing the active site of synapse) - ) Synaptic cleft
- Narrow EC space between presynaptic and postsynaptic membranes for NT to diffuse across - ) Postsynaptic component
- Consists of postsynaptic membrane, receptor sites for NT, displays postsynaptic densities (complex of proteins, binding NT receptors), contains ligand-gated Na channels
12
Q
Describe chemical synaptic transmission
A
- AP reaches presynaptic membrane, causes opening of Ca2+ ion channels
- Ca2+ enter causing synaptic vesicles to approach and attach to inner surface of membrane
- Vesicles fuse, 2 membranes rupture and point of contact and NT is released (kiss and run fusion or collapse fusion)
- NT diffuses across cleft
- NT binds to receptor (transmitter-gated channels) on postsynaptic membrane
- Conformation change occurs at channel proteins, opening of pores
- Influx of Na+ results in local depolarization, which opens up voltage-gated Na+ channels generating impulse
13
Q
Describe choroid plexus – location, composition, function
A
- Located in ventricles
- Consists of folds of pia mater covered by ependymal cells (simple cuboidal) with these cells held together by zonula occludens (tight junctions). Contain fenestrated capillaries
- Produces CSF. Waste diffuses into CSF of subarachnoid space, reabsorbed by arachnoid villi in superior sagittal sinus, passes into bloodstream. CSF acts as shock absorber
14
Q
3 layers of cerebellar cortex
A
- Molecular layer (superficial)
- Purkinje layer (middle): Purkinje cells = largest cells of NS, unique to cerebellum
- Granular layer (deepest): contains granule cells (smallest cells of NS)
15
Q
Does regeneration of neurons occur in PNS and CNS?
A
- only in PNS
