circuits of CNS Flashcards
what are Central Pattern Generators?
neural circuits that produce rhythmic motor output
what is a Local Circuit?
arrangement of neurons and their synaptic connections within local brain region
Define microcircuits.
finer arrangements of neurons and synapses w/in local circuits
what are the 3 elements of local circuits?
- input axons
- interneurons
- projection/output neurons
what neurons function in local processing?
- interneurons or intrinsic neurons whose axonal connections remain within the local circuit
how do neurons in local circuits operate?
these neurons operate in parallel w/ one another and info from each circuit is mutually shared while continually influencing its neighbors.
(in a highly interactive, simultaneously interdependent, expansive networks)
A single motor neuron & muscle cells it synapses on are collectively called _______.
motor unit
_________ innervate main force generating muscle fibers.
alpha motor neurons
_________innervate only fibers of muscle spindles.
gamma motor neurons
what generates rhythms?
combination of intrinsic pacemaker properties and synaptic interconnections
how to achieve coordination among various limbs?
sets of central pattern generators must be interconnected
what is reciprocal innervation?
it increases effectiveness of stretch reflex by minimizing antagonistic forces of antagonist muscles.
sound localization along vertical plane depends on what?
distinctive shape of external ear (pinna)
how to accurately determine sound along horizontal plane (horizontal direction)?
- two ears needed wherein cochlea of each ear will process the sounds and then sounds will be compared by neurons w/in CNS
Interaural intensity difference measures what?
sounds that are high in frequency (~2 to 20 kHz)
What does the NS use IOT measure low frequencies?
interaural time-delay map, using info from both ears together
how does the brain measure interaural timing?
neural delay lines and coincidence detectors
Do neurons in cochlear nuclei receive info from both ears?
No. Neurons in each nuclei receive input from only the ear on one side.
What neurons receive abundant input from both ears?
medial superior olivary nucleus
what do the axonal length of delay lines and their conduction velocity determine?
how long it takes for activated APs to go from cochlear nucleus to presynaptic terminals onto the MSO neuron.
What is the 1st place where APs from both ears converge?
superior olivary nucleus
how does the brain organize sensory input and motor output?
brain organizes these functions spatially by use of maps.
Main force-generating muscle fibers
extrafusal fibers
Muscle spindles
intrafusal muscle fibers
group of motor neurons innervating a muscle
motor neuron pool
Example of monosynaptic/myotatic reflex
knee jerk reflex
What neuron will be stimulated in knee jerk reflex?
primary sensory afferent, which convey their info through Group Ia axons.
Monosynaptic communication
Direct communication b/w sensory and motor neurons
Why is the reflex relaxation of the antagonist muscle in the knee jerk reflex considered polysynaptic?
it is considered polysynaptic b/c IOT achieve inhibition, branches of group Ia sensory axons synapse w/ inter neurons that inhibit alpha motor neurons of antagonist muscle of quadriceps, resulting in relaxation of semitendinosus muscles.
Sensitive to tension w/in a tendon & respond to the force generated by muscle rather than to muscle length
golgi tendon organ
Example of polysynaptic inverse myotatic reflex
Golgi tendon reflex
Axons present in golgi tendon organ
group Ib axons
axons present in muscle spindles/intrafusal muscles
group Ia axons and group II axons
What group of axons are involved in polysynaptic flexor reflex?
group A delta axons
What axons does a noxious stimulus activate?
group A delta axons
How is flexor reflex different from simple stretch reflex?
flexor reflexes coordinate movement of entire limbs and even pairs of limbs
Ex. During noxious stimuli
Central pattern generators in SC CAN CREATE COMPLEX
motor program even WITHOUT SENSORY FEEDBACK
What is a motor program?
Set of structured muscle commands determined by NS before a movement begins
What makes the visual thalamus?
primary visual cortex
interneurons facilitate sensory-motor communication
polysynaptic reflex
ex. golgi tendon, flexor
CPGs in spinal cord take advantage in:
- sensory feedback
- interconnections among spinal segments
- interactions with brainstem control centers
is phantom limb a psychological problem?
NO but sensations originate from SC and brain
brain’s ability to reorganize itself by forming new neural connections
plasticity
coincidence detection
axons from both right & left cochlear nuclei converge and synapse onto a series of neurons in MSO nucleus
neurons from MSO nucleus and higher CNS centers receive input from: both ears? one ear only?
both ears
a positive feedback circuit found in respiratory center
also helps maintain consciousness, muscular coordination, & normal breathing
reverberation
circuit in which neurons or poos process same info simultaneously
found in reflex arcs
parallel-after discharge
continuous firing after stimulus has stopped
after discharge
a circuit in which neurons or pools work sequentially
serial processing
convergence circuit
provides input to a single neuron from multiple sources
divergence circuit
spreads stimulation to multiple neurons or neuronal pools in CNS
interneurons are organized into functional groups
neuronal pools (responsible for broad range of neural functions)
