Bio Class 7 Flashcards
_____ send impulse towards soma, while _____ send impulse away from soma
dendrites, axon
Nodes of Ranvier
“saltatory conduction”
- propagation of AP along myelinated axons from one node to another, increasing velocity of ap
Axon hillock
Connects soma and axon
- ap starts here
Schwaan cells
Found in PNS, wrap around axon to form myelin
Oligodendrocytes
Found in CNS, wrap around axon to form myelin
Myelin
Insulator, increases speed of conduction
Soma
Performs basic function of cell
Types of neurons
Bipolar, unipolar, multipolar (most popular)
Bipolar neuron
Single axon, single dendrite
- direction determined by direction of impulse
Unipolar
Single process that divides to form axon and dendrite
- direction determined by direction of impulse
Depolarization
Move away from rest in positive direction (-70 to -50)
Hyperpolarization
Move away from rest in negative direction (-70 to -90)
Repolarization
Returning to rest from hyperpolarization or depolarization
Equilibrium Potential
The potential at which there is no driving force on an ion
Action Potential Process
Potential starts at -70
Cell depolarizes as Na+ VG channels open (-50)
Reaches Na+ equilibrium potential (+35)
Na+ channel is inactive and K+ VG channel opens
Cell hyperpolarizes
Na+ VG channel shifts to “closed”
K+ channel closes
What is the resting membrane potential?
-50 mV
Absolute refractory period vs relative refractory period
Absolute
- Na+ channel is inactive, cell is too positive
- impossible to fire a second potential
Relative
- Na+ channel is closed, cell is too negative
- close to K+ eq potential
Nerve impulse
Action potential travelling
Synapse
Once signal reaches end of neuron, signal goes to different cell or neuron
If there is a impulse from A –> B –> , why would the AP go towards C and not A?
Because A is in the refractory period
What happens to B and C if A is going through an AP?
Na+ is entering A and the membrane potential of B and C is at -70
- then charge from A reaches B and depolarizes it
- Once B reaches threshold, it’ll fire an AP
Electrical Synapses vs Chemical synapses
Electrical synapse
- Gap junctions
- Unregulated
- Bidirectional
- Always excitatory (always causes AP in postsynaptic cell)
* Relatively rare & found in cardiac muscle cells
Chemical synapse
Opposite of electrical synapse
- Presynaptic neuron has neurotransmitters in vesicles that are bound by synapsin (cytoskeleton filaments)
- When VG Ca2+ channel reaches threshold, it breaks down synapsin
- Vesicles are released and neurotransmitters float in synaptic cleft
- Receptors on post-synaptic dendrite will bind to some neurotransmitters
1. Neurons make one type of NT, but respond to many
2. NT in cleft can be recycled or broken down, medication can change amount of time it spends in cleft
3. Response of post-synaptic cleft depends on receptors
4. takes more than one vesicle of neurotransmitters to elicit a significant response on post-synaptic cell
EPSP
Excitatory post synaptic potential
- when one vesicle dumps into post-synaptic cleft
- If AP comes and dumps lots of vesicles, it will add up and eventually membrane reaches threshold and causes AP
IPSP
Inhibitory Post Synaptic Potential
- Adds up and eventually membrane hyperpolarizes
Summation
Adding EPSP and IPSP
- Spatial - add multiple inputs over wide area
- Temporal - add frequent impulses from a single source
_______ increases intensity in neurons
frequency