KIN 155 Study Guide - Midterm Guide: Inhibitory Postsynaptic Potential, Sliding Filament Theory, Axon Hillock

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KIN 155 Midterm #1
Terms:
Efferent neuron: motor neuron (movement + muscle) – bottom-up (data driven)
input from neurons, output to muscle cells
Afferent neuron: sensory neurons, bringing info into CNS – top-down (contextual information)
input from special endings that sense stimuli, output to neurons
Interneuron: non insulated (grey matter), generates action, communicates with each other (most
of the cell)
input from neurons, output to neurons
Structures:
Dendrites: (input) receives information (post synaptic endings)
Cell body: metabolic processes of the cell
Axon hillock: accumulates impulse/energy to generate action potential (AP)
Axon: transferring electrical information
Axon terminals: (output, presynaptic endings) sends off chemical messaging
Presynaptic membrane: flow of chemical information starts here (axon terminals)
Postsynaptic membrane: flow of chemical information ends here (dendrites)
Receptor types:
oIonotropic: protein ion channels
oMetabotropic: trigger 2nd messenger
Resting membrane potential: inside of the cell is negative compared to the outside [ion]
baseline or steady state of membrane potential, approx. -65mV in neurons
Depolarization: more positive (moves in a positive direction)
Hyperpolarization: more negative (moves in a negative direction)
Action potential: rapid depolarization and hyperpolarization of the membrane potential (all or
nothing response)
propagates down the axon (must be converted to chemical messenger at axon terminal)
Node of Ranvier – a gap between axon that generates action potential (message jumps
along the axons)
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EPSP: excitatory post-synaptic potential
leads to depolarization of membrane and increases permeability to sodium
IPSP: inhibitory post-synaptic potential
leads to hyperpolarization of membrane and increases permeability to chloride
Voltage-gated ion channels: at axon hillock there are different group of protein ion channels
Types of synaptic summation
Temporal summation: increases frequency (receiving one signal after another that
accumulates)
Spatial summation: increase number (signals from multiple dendrites combine)
Alpha motoneurons: synapse onto extrafusal skeletal muscles cells
extrafusal – muscle cells (fibres) that are responsible for generating force
Neuromuscular junction: synapse of a motoneuron onto muscle cell
Muscle action potential: depolarization leads to this (+ charge along membrane)
acetyl-choline released from motoneuron
Na+ comes in and positive along muscle cell membrane
Release of Ca+ into the cell allowing for cross bridge formation
Excitation-contraction coupling: the process of sliding filament theory
Motor Unit: the motoneuron and all the muscle cells it connects (synapses) to
Properties of muscle cells are the same for all muscle cells in a single motor unit
Innervation Ratio: the number of muscle cells in a motor unit
Lower ratio = increased precision control
Surface EMG: measurement of electrical activity reflecting the sum of the muscle AP
Concentric contraction: muscle shortened and activated
Eccentric contraction: muscle lengthening (elongates) and activated
Isometric: muscles activated but no movement
Agonist: the ‘prime mover’. Muscle that is primarily responsible for generating a specific
movement
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Antagonist: the muscle that acts in opposition to the specific movement generated by the agonist
Synergist: helps perform the movement generated by the agonist
Reciprocal activation: simultaneous activation of agonist and inhibition of antagonist muscle
Co-contraction: simultaneous activation of agonist and antagonist
Proprioception: sense of ‘one’s body position, orientation, and forces
Touch: sense of contact on skin (force, shape, texture, etc.)
Sight: sense of objects/environment based on lighting
Somatosensory: sense organs from skin, muscle, joints, internal organs (touch + proprioception)
Vestibular: inner ear organs to sense position of head movement and orientation
Visual: specialized sense organs for detecting light (retina)
Mechanoreceptor: responsive to mechanical stimulus
Muscle = muscle spindles
Tendons = Golgi tendon organs
Photoreceptor: responsive to changes in light
Nociceptor: pain receptor
Generator Potential (before AP): depolarization caused by stimulus (like an EPSP)
Detection of stimulus prior to AP. Initiates the AP
Movement time: time between onset of action and completion of the response
Response time: total time from onset of a stimulus to the end of the movement
Contraction of intrafusal muscles
Gamma motoneuron: motoneuron that synapses onto the intrafusal muscle fibre
Alpha-gamma co-activation: alpha motoneuron and gamma MN are activated together
Divergence: a neuron has many different projections to many neuron and synapses
Convergence: a neuron receives many synapses from many different neurons
Phase-dependent modulation: modulation of a reflex at different points (phases) in a movement
Modulation = measuring different size of response while stimulus stays constant
Golgi tendon organ ‘reflex’
Inhibitory reflex: activation of GTO can lead to IPSPs at the alpha motoneuron
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Document Summary

Efferent neuron: motor neuron (movement + muscle) bottom-up (data driven) input from neurons, output to muscle cells. Afferent neuron: sensory neurons, bringing info into cns top-down (contextual information) input from special endings that sense stimuli, output to neurons. Interneuron: non insulated (grey matter), generates action, communicates with each other (most of the cell) input from neurons, output to neurons. Axon hillock: accumulates impulse/energy to generate action potential (ap) Axon terminals: (output, presynaptic endings) sends off chemical messaging. Presynaptic membrane: flow of chemical information starts here (axon terminals) Postsynaptic membrane: flow of chemical information ends here (dendrites: receptor types, ionotropic: protein ion channels, metabotropic: trigger 2nd messenger. Resting membrane potential: inside of the cell is negative compared to the outside [ion] baseline or steady state of membrane potential, approx. Depolarization: more positive (moves in a positive direction) Hyperpolarization: more negative (moves in a negative direction) Epsp: excitatory post-synaptic potential leads to depolarization of membrane and increases permeability to sodium.

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