Phys: Propagation And Transmision Of Action Potentials And Synapses Flashcards
Schwann cells surround the nerve forming a…
Myelin sheath
Sphingomyelin decreases __________________ and _____________ 5000-fold
Membrane capacitance and ion flow
Myelin sheath is interrupted every 1-3mm by a….
Node of ranvier
Saltatory conduction
Action potentials are conducted from node to node but only OCCUR at the nodes
Why do APs only occur at the nodes?
-Na+ channels are concentrated there
APs an nodes allow for increased __________ and ______________
Velocity adn energy conservation
Velocity of AP in unmyelinated fibers:
0.25 m/s
Velocity of AP in myelinated fibers:
100 m/s
Multiple sclerosis is an…
Immune mediated inflammatory demyelinating disease of the CNS
Impulse transmission between cells occurs at a _____________
Synapse
Synapses are sites of…
Transmitting impulses from one cell (usually neuron) to another
Types of synapses:
-electrical synapse (gap junctions)
-chemical synapses(most common)
-excitatory
-inhibitory
Electrical synapses are…
Direct connections between cells which allows ions to flow between
Electrical synapses creates a ________________, which is a bunch of cells acting like one cell
Syncytium
Gap junctions are made up of…
Connexons that make holes in neighboring membranes
Where are coordinated contraction required?
-heart
-smooth muscle
-bladder
Electrical synapses are _____, no have no _____________
Fast, integration
Electrical synapses can travel…
In both directions or can be unidirectional
Electrotonic potential is proportional to…
Stimulus strength
Electrotonic potential is not propagated but…
Decremental with distance
Electrotonic potential exhibits ______________
Summation
Chemical synapse information is transported via….
Chemicals across synaptic cleft
Chemical synapse experience ______________ flow
Unidirectional - presynaptic to postsynaptic
_________ are released as neurotransmitters in chemical synapses
Chemicals
Neurotransmitters released from pre-synaptic cell by the action potential bind to…
Receptors on the post-synaptic cells
Activation of postsynaptic receptors alters __________________
Membrane potential
When an action potential reaches the terminal what opens? and what happens?
Voltage gated Ca channels open, Ca enters cell and causes exocytosis of vesicles containing neurotransmitters
Chemical synapse is _________ but allows for _____________
Slower, integration
When an action potential reaches the terminal what opens? and what happens?
Voltage gated Ca channels open, Ca enters cell and causes exocytosis of vesicles containing neurotransmitters
Binding of neurotransmitter to receptors allows:
-Neurotransmitters diffuse across the cleft from pre-post synaptic cell
-bind to receptors on post-synaptic cell mem.
Effect of neurotransmitter binding on post-synaptic cell:
-alters membrane potential, can depolarize or hyperpolarize
Depolarization is __________ and makes it _____ likely for AP to fire
Excitatory, more
Hyperpolarization is _______________ and makes it ____likely for AP to fire
Inhibitory, less
Synapses are __________ structures
Dynamic
Synapses can increase and decrease in complexity and number depending on:
-use
-experience
One-to-one synapses
One presynaptic to one postsynaptic
One-to-one synapse is used for:
-NMJ
-conveys information
One-to-many synapse:
One presynaptic to more than one post-synaptic neuron
One-to-many synapses are used for:
-motor neurons in spinal cord
-used to amplify a signal
Many-to-one synapse:
More than one presynaptic to one postsynaptic
Many-to-one synapse is used for:
-allows for integration of many signals
-decides the proper response
-very common
Excitatory post-synaptic potentials (EPSP)
-depolarize the cell towards threshold
-usually result of opening Na or Ca channels depolarizing membrane to small degree (not enough for AP)
Inhibitory post-synaptic potentials (IPSPs):
-hyperpolarize cell membrane away from threshold
-usually opening of Cl channels, increasing mem potential with negative charges
Excitatory neurotransmitters:
glutamate and acetylcholine
Inhibitory neurotransmitters
GABA and glycine
Current passing through an inhibitory interneuron elicits an…
Inhibitory IPSP in the flexor motor neuron
Usually each neuron is the post-synaptic cell for…
Numerous pre-synaptic cells (up to 10,000)
Signals have to be integrated in order to…
Make a decision about generation of new action potential
The time constant of a neuron determines…
The time course of the synaptic potential (how rapidly membrane transmits a charge)
The length constant of a neuron determines….
How much the depolarizing current is reduced as it spreads passively (how far initial depolarization travels through nerve before subsiding)
The time constant of the postsynaptic neuron affects the…
Amplitude of the depolarization caused by consecutive EPSPs produced by a single presynaptic neuron
If a second EPSP is elicited before the first decays…
The two potentials summate to induce an action potential
Spatial summation
Multiple inputs over a distance
