Neurons, Action Potential and Synapses Flashcards
Anterograde Movement
Proteins synthesized in the “secretory pathway” are packaged by budding off in membrane-enclosed vesicles from the golgi.
The Vesicles and mitochondria are carried down the axon on microtubule “tracks” by kinesin motors that are energized by ATP
Retrograde Movement
Vesicles now move in reverse, carried by Dynein motors, which also split ATP and Move along microtubule “tracks”
Fast anterograde
Fast retrograde
Slow Anterograde
Glial cell
Non Neuronal
Main types of CNS glial cells are:
Oligodendrocytes
Astrocytes
Microglia
Main types of PNS glial cells are:
Satellite cells
Schwann cells
Enteric glial cells
Oligodendrocytes
synthesize myelin in CNS
form myelin sheaths of CNS axons
Astrocytes
Microglia
Schwann cells
Form myelin sheaths of PNS axons
3 Functions of Neurons
Reception
Conduction
Transmission
Action Potential flow
- Synaptic terminals: Brings signals from other neurons
- Dendrites: receive signals from other neurons.
- The cell body: integrates signals; coordinates metabolic activities
- The action potential starts between the cell body and axon.
- The axon transmits action potential.
6.The myelin sheath makes the signal travel faster
7:Synaptic terminals transmit signals
Generation of Action Potential
- Action potential reaches pre-synaptic terminal leading to neurotransmitter release
- Released neurotransmitter binds to post-synaptic receptors leading to post-synaptic potentials
- Integration of post-synaptic potentials at initial segment of axon triggers action potential if threshold is exceeded
Resting Potential
3 sodiums come out
2 potassium comes in
makes inside the cell more negative
-70 membrane potential
Threshold of excitation
-55 membrane potential
The neuron must reach the threshold of excitation in order to generate an action potential
All the sodium gated channels open, causing a rush of sodium to come in
Refractory Period
Absolute refractory period: Positive membrane potential ( cycle of the action potential)
Relative refractory period : repolarization
Check these
Conduction Velocity
If unmyelinated, slower
if myelinated, faster as the action potential can jump between the gaps
Summation
Look at pictures
Temporal Summation
Concentrated
several impulses from one neuron over time
Spatial summation
Wide range of stimuli
Impulses from several neurons at the same time
Acetylcholine
An excititory neurotransmitter
Location: neuron to muscle synapse
Function: Activates muscle
Dopamine
An excititory neurotransmitter
Location: Mid-brain
Function: Control of movement
Epinephrine
A neurotransmitter
Location: Sympathetic system
Function: stress response ( fight or flight)
Serotonin
A neurotransmitter
Location: Midbrain, pons, medulla
Function: sleep, mood
Endorphins
A neurotransmitter
Location: Brain, Spine
Function: mood, pain reduction
Modulation of Functions of the Brain
Spatially focused or
WIdely Divergent
Spatially Focused
Widely Divergent
Types of Action
(that will be on the exam)
Fast transmission
Slow Transmission
Fast transmission
=>1msec
Examples: Acetylcholine (nicotinic)
Amino Acids
Slow Transmission
between 1 msec to 1 sec
Examples: Acetylcholine (muscarinic)
Catecholamines
Electrical and Chemical Synapse
Electrical Signals at Synapse
Electrical signals :
Due to changes in permeability and altering flow of charged particles
changes in permeability are due to changing the number of open membrane channels
Ionic Channels
Non-gated ion channels or leak channels
- always open
-specific for a particular ion
Gated Ion channels
- open only by stimulus
-voltage–gated, ligand-gated, stress-gated
Ion pumps
- needs ATP
-maintain ion gradients
Graded Potentials
Occur in dendrites/cell body
Small, localized change in membrane potential (graded potential)
- change of only a few mV
- opening of chemically-gated or physically-gated ion channels
-travels only a short distance (few mm)
Release of neurotransmitters
- neurotransmitter is packaged into vesicles
- Action potential arrives at axon terminal
- Voltage-gated Ca2+ channels open and Ca2+ enters the axon terminal
- Ca2+ entry causes synaptic vesicles to release neurotransmitter
- Neurotransmitter diffuses across the synaptic cleft and binds to specific receptors on postsynaptic membrane
- Binding of neurotransmitter opens ion channels, resulting in graded potentials
- neurotransmitter effects are terminated by reuptake through transport proteins, enzymatic degradation, or diffusion away from the synapse
