Chapter 2 Flashcards
Charles Scott Sherrington
Neurons communicate
by transmitting chemicals
at junctions, called “synapses”
-Order of reflex of reflex: 1st sensory neuron, 2nd interneuron, 3rd connects to motor neuron or afferent neuron (bring in information)
Sherrington’s reflex
- As one set of muscles becomes excited, another set relaxes
- Reflexes are slower than conduction along an axon
- how neurons communicate with each other by studying reflexes (automatic muscular responses to stimuli) in a process known as a reflex arc
Temporal Summation
Repeated stimuli can have a cumulative effect and can produce a nerve impulse when a single stimuli is too weak
EPSP
Excitatory postsynaptic
- graded potential that decays over time and space
- sodium gates open
Presynaptic neuron
neuron that delivers the synaptic transmission
Postsynaptic neuron
neuron that receives the message
Spatial Summation
combined effect of several nearly
simultaneous stimulations at several synapses onto one neuron
Temporal summation
combined effect of quickly repeated
stimulation at a single synapse
IPSP
Inhibitory Postsynaptic Potential
- temporary hyperpolarization of a membrane
- potassium or chloride gates open
Sherrington wrong
Sherrington assumed that synapses produce on and off responses
Synapses vary enormously in their duration of effects
Spontaneous Firing Rate
The periodic production of action potentials despite synaptic input
SFR EPSP
increase the number of action potentials above the spontaneous firing rate
SFR IPSP
decrease the number of action potentials below the spontaneous firing rate
What does it mean when we say the membrane is polarized?
This means that there is an electrical difference across the cell membrane.
How is EPSP like depolarization?
Deporalization is the action it gets more positive, epsp is when it gets to the high level
How is IPSP like hyperpolarization?
Hyperporazation becomes begative, IPSP is finally negative
Difference between EPSP and an action potential
Action potential is a nerve impulse
EPSP is graded potential
Otto Loewi
First to convincingly demonstrate that communication across the synapse occurs via chemical means
Neurotransmitters
chemicals that travel across the synapse and allow communication between neurons
Otto Loewi’s experiment
Found that stimulating one nerve released something that inhibited heart rate, and stimulating a different nerve released something that increased heart rate
Realized that he was collecting and transferring chemicals, not loose electricity
The Sequence of Chemical Events at the Synapse
- The neuron synthesizes chemicals that serve as neurotransmitters
- Action potentials travel down the axon
- Released molecules diffuse across the cleft, attach to receptors, and alter the activity of the postsynaptic neuron
