Nervous System Flashcards
neuronal
cellular communication
fast, direct, targets specific cells/tissues (nerves)
hormonal
cellular communication
- seen in the endocrine system
- slow
- widespread
- affects multiple cells/tissues throughout body
paracrine system
cellular communication
local hormones released by cells into IF to act on a nearby cell
neuron structure
soma, dendrites, and axons
neuron function
transmit electrical signals from one cell to another
soma
cell body
dendrites
extension –> receives signals signal
axon
sends signal out
* axon hillock
* myelin sheath
* nodes of ranvier
axon hillock
axon
connection to cell body
myelin sheath
axon
fatty acid insulation (speed up AP by stopping ion exchange)
cells that make myelin
axon
- oligodendrocytes in CNS
- schwann cells in PNS
white matter
axons with myelin
gray matter
axons without myelin
Resting membrane potential
- 70 mV
- Establish by Na+/K+ pump
- 3 Na+ out, 2 K+ in makes inside of cell have negative charge relative to outside
- Maintained by Na+/K+ ATPases via hydrolysis of ATP
- K+ leaky channels also maintain RMP
Depolarization
- Stimulus cause threshold potential to be -55 mV
- Voltage-gated Na channels open, Na+ diffuses into cell
- Inside develops a positive charge
- K+ channels close
Transition point
- Depolarization to repolarization
- Na+ reaches peak and channels close
Repolarization
- Na+ channels close
- Voltage gated K+ channels open, K+ diffuses out
- Inside of cell becomes negative once again
- Absolute refractory period
Hyperpolarization
- Inside of cell becomes more negative than resting potential due to K+ flow
- Relative refractory period
Absolute refractory period
no stimulus can cause AP
* Due to inactivation of Na+ channels
Relative refractory period
requires strong stimulus for AP
Synapse
- AP reaches end of presynaptic axon voltage gated Ca++ channels open and enters neuron
- Ca++ cause synaptic vesicles to fuse/exocytosis from neuron with NT inside
- NT binds to ligand gated ion channels on post synaptic neuron graded potentials
- Graded potentials summate at axon hillock and AP fires once it passes threshold
EPSP (excitatory postsynaptic potential)
depolarized membrane and cause Na+ ions to flow into cell
IPSP (inhibitory postsynaptic potential)
hyperpolarized membrane and causes K+ to flow OUT and Cl- in