Introduction to the Neural
Motor
System
August 14, 2013
So far as our present knowledge goes we
are
led to think that the tip of a twig of the [axon's] arborescence
is not
continuous with but merely in contact with the substance of the
dendrite
or cell body on which it impinges. Such a special connection of
one
nerve
cell with another might be called a synapsis.
- C.S.
Sherrington (1897)
Individual neurons can encode complex
information
and concepts into simple electrical signals; the meaning
behind these
signals
is derived from the specific interconnections of neurons.
- S.W. Kuffler & J.G. Nicholls (1976) From Neuron to
Brain
- Neuron
structure and function
- Structural features
- Functional properties
- Cell membrane
- Channels
- Allow passage of certain ions
- Receptors
- Resting membrane potential
- Inside of cell -70 mV with respect to outside
- Action
potential
- Transient change in voltage across membrane, from -70 mV
to
+55 mV that
travels down axon at speeds ranging from less than 1 to 100
meters/second
- Synaptic
transmission
- Excitatory
- Results in depolarization, positive shift of membrane
potential
- Inhibitory
- Results in hyperpolarization, negative shift of membrane
potential
- Electrotonic conduction of EPSPs and IPSPs in along
dendrites
- Summation at axon hillock where action potential is
generated
- Synthesis and transport of neurotransmitter to synaptic
cleft
- Diversity of neuronal types
- Excitatory
- Inhibitory
- Long-range connections
- Local connections
- Types of neural circuits
- Excitatory loops
- Inhibitory loops
- Lateral inhibition
- Overview of the Central Nervous System
- Basic principles
- Hierarchical processing
- e.g., corticospinal tract
- Parallel processing
- e.g., frontal eye field and superior colliculus
- Recurrent Loops
- Functional areas
- e.g., Primary motor cortex
- Topographic maps
- e.g., Map of body in motor cortex
- Compartmentalization
- e.g., striosomes and matrix in striatum
- Spinal cord
- motor neurons - final common pathway (Sherrington)
- Brainstem
- Cerebellum
- Basal ganglia
- Limbic system
- Thalamus
- Cerebral cortex