Histology part 1 Flashcards
Cell types of the CNS
all cell types derived from neural tube
-Neurons
-Glia (oligodendrocytes, astrocytes, ependyma)
Microglia
-macrophages recruited to CNS (mesoderm)
Endothelial cells
-invading CNS to nourish (mesoderm)
-important for making up blood-brain barrier
Cell types of the PNS
-Sensory and motor neurons
-schwann cells (myelinate axons)
-pericytes (various functions; supporting synapses/neurons, make blood-nervous system barrier)
Tissues of the CNS
Cells of the CNS are organized into various tissue types
-White matter (myelinated axons and glia) VS. grey matter (cell bodies of neurons and glia)
-meninges- 3 layers of connective tissue (fibroblasts from mesoderm) that cover the CNS
3 layers of the meninges
1.Dura mater- tough outer layer
2.Arachnoid- middle layer; web-like structure
3. Pia mater- inner layer
Neurons
-functional unit of the nervous system
-they form synapses with other cells (neurons or target organs)
-Unidirectional signalling
-supported by glia (more glia than neurons)
Structure of neuron
-Cell body with dendrites
-Axon (myelinated or unmyelinated)
-Terminal branches/telodendrites
Neuron Function
To signal transmission form PNS to CNS, to allow animal to respond to environmental changes
* CNS responsible to integrate and interpret
* PNS responsible to detection and performing response
Neuropil
Represents the space between the neurons and glia
-dendritic processes and synpases
CNS histology
-very tightly packed (no intercellular space, instead it is the neuropil)
-no connective tissue in CNS (connective tissue arises from mesoderm (fibroblasts)
- can see synapse (has axon and dendrites)
Synapses
-similar in CNS and PNS
-Ex. neuromuscular junction (NMJ) in PNS- a single axon can innervate muscle fibers, but individual muscle fibers are only innervated by one axon
PNS synapse vs. CNS synapse in terms of neurotrasmitters
-PNS: 1 neurotransmitter (acetylcholine), always excitatory
-CNS: Many neurotransmitters (GABA-inhibitory, Glutamine-excitatory)
Input/synapses for PNS vs CNS
PNS: only input from one neuron
CNS: each neuron receives 1000+ synapses
Neurotransmitter effects for PNS vs CNS
PNS: defined effect where the AP always initiates depolarization and target organ response
CNS: Varied effect where a single AP only changes membrane potential a small amount therefore need multiple inputs to depolarize cell and initiate action (summation effect)
