Neural Architecture Flashcards
Dendrites
. Sites for incoming stimuli
. Transmit electrical signals to the cell body
. Can develop APs
Synapse types
. Axosomatic: axon ending on a cell soma/body
. Axodendritic: axon ending on dendrite
. Axoaxonic: axon ending on axon
. Motor end-plate: axon ending on muscle cell
Neuron
. Morphological and functional unit of nervous system
. Primary function is communication through neurotransmitters mostly
Neuronal language
. Function as electric switched
. Stimulates irritates neuron and electrical signal is conducts along axon and transmitted to another neuron (EPSP)
. If neuron is not stimulated enough to generate electrical signal then there is no communication amount neurons (IPSP)
Spatial summation
. Individual neuron receives simultaneous inputs from multiple sources
. Small EPSPs contributed by many different synaptic terminals add up to produce single large EPSP (same goes for small IPSPs)
. EPSP and IPSPs may cancel each other out
Temporal summation
. A second input arrives before the EPSP or IPSP elicited by the previous one has finished so it can add together
Synaptic connection characteristics
. Have plasticity (continually form new connections and breaking old ones as you grow)
. Axons and dendrites can grow and branch or retract and reform
Neural circuitry basic understandings
. Complexity of human behavior depends less on specialization of individual nerve cells and more on the fact that these cells are organized in precise anatomical circuits
. Nerve cells are able to convey unique info because they form specific networks
Afferent versus efferent
. Afferent: info carried onward the CNS
. Efferent: info carried away from CNS
Direct reflex arc
. Unlikely to be found in humans
. 2 neurons
. Sensory transfers input to a motor/efferent neurons that send the info (output) to a peripheral organ (muscle)
Indirect reflex arc
. Interneuron between sensory and motor neuron
. Patellar reflex is example
Divergence
. Output from 1 neuron onto many
. Each postsynaptic neuron receives input from the same presynaptic neuron, but may react to it different
. Divergent output allows the same signal to reach many different neurons of different circuitries
Convergence
. Output from many neurons go onto 1 postsynaptic neuron
. Inputs can be excitatory or inhibitory
. Inputs may be active at different times
Reverberating circuit
. Neuronal pathway arranged in circle so impulses are recycled in a loop to cause positive feedback/reverberation
. Important to facilitate or inhibit certain pathways
Prolonged stimulation
. Occurs to a motor neuron
. Motor receives subsequent stimulation that are delayed in time
Importance of increased numbers of interneurons
. Pools of interneurons can make more complex circuits that are in charge of intermediate processing and distribution of the input coming from sensory to motor neuron
. Allows more complex spatial and temporal distribution of the incoming info
What happens to incoming information w/in spinal cord of brainstem
. Be passed to a motor neuron via reflex
. Travel up (ascending pathway) to subcortical/cortical areas, then info is distributed to interneurons in nuclei along ascending pathway creating divergence of input and spatial/temporal distribution of info
Modality specificity
. Initially each sensory system has its own separate pathway
. Info transmitted from eye via optic n. Remains separate from auditory stuff initially
. Input will reach primary seniority cortex where stimuli of a single sensory modality are integrated
Integration w/in modality across space
. Complex sensory stimulus causes activity in multiple receptors (neurons) corresponding to multiple channels
. Info processed in different channels has to combine to produce “big picture”
Integration w/in modality across time
. Info present at 1 time has to be related to and linked w/ info that is present earlier and later
Integration across modalities
.single modality info will pass to association vortices where the information will be elaborated and integrated w/ other sensory modalities
. Info from 1 modality is is coward w/ info from other modalities
What occurs when information goes from sensory and association cortices to motor cortices?
. Info converges on upper motor neurons
. Their axons descend (descending pathway) down to brainstem/ spinal cord
. Brings response (output) that will be passed to final motor neuron (convergence) in brainstem/spinal cord (lower motor neuron)
. Ultimately passes the command to peripheral organ (muscle)
Volitional response
. Motor command decided at cortical level
. Takes longer than reflex response because it is result of longer pathways and projections to different specialized cortical areas
. What starts as volitional response can turn into reflex response later in life
What is important for accurate motor performance
. Sensing of motor action and motor feedback on sensory systems
Learning and memory formation
. When motor action occurs, comparison of sensory input in 1 modality when compared w/ input from another modality can result in memories that lead to adjustment of the relation between the 2 modalities
. Happens extensively during postnatal development
. Info about seeing objects and reaching for them results in internal representation of space in which visual space is in register w/ somatosensory space
Synthesis of info and creativity
. Brain stores information
. Information has capacity to transform information and recombine items of information in novel way
. Can create new sensory stimuli that we ha e never perceived in real world
Types of neural maps
. One for sensory perceptions
. One for motor commands
. Interconnection of sensory and motor (association area) that elaborate and integrate sensations and plan motor actions
Redundancy in neuronal circuitry
. Every single neuronal function recruits different groups of neurons that simultaneously process the same/ similar information
Parallel processing
. Deployment of several circuits to process
. Mostly utilized for functions considered priority for the economy of the entire nervous system
. Preserved attempts to maintain key functions for building a more reliable and fast-processing brain
What are the only subdivisions of CNS that communicate w/ periphery
. Spinal cord and brain stem
. Only exception is the cranial nerves
