What are neurons?
cells that respond to stimuli through electrochemical mechanisms
– Excitable or inhibitory
What are Glia?
support cells involved in conduction speed, repair, neurotransmitter maintenance
Describe the cell body of a "Typical" neuron.
Cell body is large & has a large, euchromatic nucleus with a well-developed nucleolus
- Nissl substance/bodies
What happens to a neuron, when you increase the amount of dendritic spines?
it increases receptive area
Where does the long axon of a "Typical" neuron emerge from?
emerges from an axon hillock
What are Nissl substances/bodies of a "Typical" neuron?
large, basophilic masses of free polysomes & RER
What is the distal end of an axon called?
- some have branching, collateral branches
Ends of axons usually have small what?
- dilation of branch ends & contact postsynaptic cell
Describe a multipolar neuron.
Describe bipolar neuron.
Describe unipolar neuron.
Describe anaxonic neuron.
For neuronal synapse communication, is the transmission unidirectional or bidirectional?
synaptic transmission is unidirectional
Synapses = Sites where nerve impulses are transmitted from one neuron to another, or from neurons and other effector cells
Synapses convert an electrical signal (nerve impulse) from the _____________ into a chemical signal that affects the ___________.
1. presynaptic cell
2. postsynaptic cell
Most synapse communication between nerves act by releasing what?
Neurotransmitters - small molecules that bind receptor proteins
Describe what the presynaptic terminal bouton of a chemical synapse contains.
mitochondria & synaptic vesicles --> release NT via exocytosis
Describe what the postsynaptic cell membrane of a chemical synapse contains.
receptors for the neurotransmitter
ion channels to initiate a new impulse
What is a 20- to 30-nm-wide intercellular space that separates pre- & postsynaptic membranes in a chemical synapse?
Describe the electrical synapse of a neuron.
Permit direct, passive flow of electrical current from one neuron to another
- potential difference (voltage) generated locally by presynaptic action potential
How does current flow occur and links pre- & postsynaptic membranes (2nm) in electrical synapses of neurons?
What proteins permit diffusion of small molecules & electric current flow in an electrical synapse of neurons?
What are the five (5) types of Glial cells?
3. Ependymal cell
4. Microglial cell
What is a neuropil?
type of Glial cell
fibrous intercellular network of cellular processes emerging from neurons & glial cells
What are characteristics of Astrocytes?
- large number of long, branching processes
- proximal regions are reinforced with intermediate filaments made of glial fibrillary acid protein (GFAP)
They form a vast network of delicate terminals contacting synapses & other structures
Terminal processes of a single astrocyte typically associate 1M+ synaptic sites
What are characteristics of Oligodendrocytes?
Type of Glial cell.
- Extend many processes that wrap repeatedly around a portion of a nearby axon
- Cytoplasm gradually moves out: leaves compacted layers of cell membrane, collectively termed myelin. Forms a myelin sheath.
Will enwrap axons from multiple neurons - a given axon is covered by many oligodendrocytes
Usually appear as small cells with rounded, condensed nuclei & unstained cytoplasm
What are characteristics of Ependymal cells?
• Columnar or cuboidal cells that line the fluid-filled ventricles of the brain & the central canal of the spinal cord
• Apical end may cilia & long microvilli
– Facilitate movement of CSF
– Likely involved in absorption
• Joined apically by apical junctional complexes & there is no basal lamina
What are characteristics of Microglia?
A type of Glial cell.
• Less numerous than oligodendrocytes or astrocytes
• Migratory, will remove damaged or unactive synapses or other fibrous components
• Major mechanism of immune defense in the CNS, removing any microbial invaders
• Originate from monocytes
What has a central mass of grey matter that has the shape of a butterfly?
- Ventral, dorsal, & lateral horns
What lies in the central commisure of grey matter of a spinal cord?
- lined by ependymal cells and contains CSF
What does white matter consist of for a spinal cord?
White matter consists of ascending tracts of sensory fibers & descending motor tracts