lecture 7 Flashcards
neurons
- excitable cells
- carry electrical signals (fire action potentials or release neurotransmitters)
- several types
~ classified based on structure/function
glial cells (neuroglia)
- non-excitable cells
- provide physical and biochemical support for neurons (act as a supporting cell)
- several types
~ classified based on location/function
Glial cells (in CNS)
- ependymal cells (create barrier between carpartments)
- astrocytes (sweep up)
- microglia cells (act as immune cells)
- oligodendrocytes (form myelin)
Glial cells (in PNS)
- satellite cells (provide physical support)
- schwann cells (form myelin)
dendrites
receives incoming signals
cell body (soma)
integrates information
axon
carry outgoing information to the axon terminal
information is passed to the next (post synaptic) neuron or other target cell (e.g. muscle, gland)
Neuron =
1cell
Nerve=
a bundle of axons from multiple neurons
Node of Ranvier
region of unmyelinated axon membrane between two schwann cells
—> action potentials are generated here
diseases of demyelination include
- multiple sclerosis: autoimmune degeneration of myelin in CNS; progressive
- guillain-barré syndrome: autoimmune degeneration of myelin in PNS; sudden onset and usually temporary
demyelination causes impaired conduction of electrical signals along the axon
graded potential
- depolarization or hyperpolarization
(excitatory (EPSP) vs inhibitory (IPSP) post-synaptic potential) - amplitude of response depends on strength of stimulus and density of receptor channels
- electrical signal travel in form of ionic charge (+ or -) diffuse through the cell
- response diminishes with distance
action potential
- depolarization only
- all-or-none response depends on the membrane reaching threshold potential
- needs high density voltage gated Na+ channels for this type of signal
explain how electrical signals are produced in neurons
- Signal input in dendrites
- change in ion permeability
- generation of graded potential - Graded potential spreads through soma and reaches axon hillock where there is a high density of voltage gated Na+ channels
—> if threshold is reached, initiates action potential - action potential is propagated along axon
- at axon terminal, action potential triggers neurotransmitter release
- Neurotransmitter binds to receptors on postsynaptic dendrites/membrane
Ohms law equation
V=IR
Rm (membrane resistance) varies with
channel gating
- no channels and good insulator = high Rm
- channels allowing ion flow= low Rm
Ri internal resistance of cytoplasm
- depends on cytoplasm composition
- inversely proportional to diameter
subthreshold graded potential ___________ trigger action potentials
DO NOT
suprathreshold graded potentials ____ trigger action potentials
DO
what is the minimum potential required to trigger an action potential
threshold : -55mV
