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Anatomical and functional unit of the nervous system
Consists of a nerve cell body, dendrites, and an axon
Neuron
Groups of neurons located in a specific region of the brain or spinal cord that have a similar appearance, receive information from similar sources, project their axons to similar targets, and share similar functions
Nucleus
Many axons grouped together, which typically pass from a given nucleus to a common target region or to several regions
Tract
White matter consists of _____
Gray matter consists of ______
Myelinated axons / neuronal cell bodies
Nonneural cells forming the interstitial tissue of the nervous system
Glial cells
Three connective tissue coverings surrounding the CNS
Meninges
Fluid-filled spaces within the CNS
Ventricles
Where does the corticospinal tract cross?
Lateral: pyramidal decussation (caudal medulla)
Anterior: at the level of the spinal segment
Corticospinal tract function
Voluntary movement of upper and lower limbs
Where are the medullary pyramids located?
On either side of the continuation of the anterior median fissure in the caudal medulla
Positive Babinski indicates a lesion in which tract?
Corticospinal
Main excitatory neurotransmitter
Glutamate
Main inhibitory neurotransmitter
GABA
Steps of glutamate-mediated synaptic transmission
- Glutamine–>Glutamate via glutaminase in mitochondria
- Released via vesicles into synaptic cleft
- Effects
- Glutamate is taken up by glial cells and converted to glutamine
- Glutamine transported to presynaptic terminal and the cycle starts over
Why is glutamate converted to glutamine in the postsynaptic terminal?
To keep glutamate levels low in synaptic cleft
Which ion channels does glutamate bind to?
NMDA
Kainate
AMPA
Steps of GABA-mediated synaptic transmission
- Glutamate converted to GABA by glutamic acid decarboxylase
- Stored and released via vesicles from presynaptic cell
- Effects
- Taken up by postsynaptic and glial cells
- Glial mitochondria convert GABA to glutamine
- Repeat cycle
What ion channel does glycine affect?
Cl-
How is glycine formed?
Glucose forms serine, which forms glycine via serine trans hdroxymethylase
Fast synaptic transmission
Ionotropic
Slow synaptic transmission
Metabotropic
Which ion channels are ionotropic?
NMDA
AMPA
Kainate
NMDA co-agonists
D-serine
Glycine
GABA stimulates _____ channels. What are the effects?
Cl-
Hyperpolarizing and inhibitory