neuroscience - exam 3 Flashcards
neurons
cells that send & receive electrical or chemical signals (nerve cells)
nervous systems
circuits of neurons that integrate internal & external
How do neurons and nervous systems differ in association with species complexity
more complex organisms have more complex nervous systems & more neurons
least complex organisms nervous system
neurons spread out
nerve net
nerves
neurons bundled
cephalization
neurons cluster in the head = brain
bilateral symmetry
both sides the same
central nervous system
brain & spinal cord
peripheral nervous
nerve cells outside the CNS
dendrites
receives signals
cell body
contains cell machinery
axon hillock
integrates signals
“decider”
axon
carries signals to synaptic terminals
synaptic terminals
send signals to other cells
astrocytes
blood-brain barrier
prevents toxins from entering the brain
nourish/support neurons
role in mental disorders
microglia
immune cells
protect brain against pathogens
clean up debris
oligodendrocytes
glial cells in CNS
wrap around axons
schwann cells
glial cells in PNS
wrap around axons
myelin sheath
encases neurons & insulates
increases signal speed
what disease is associated w/ myelin degeneration
multiple sclerosis
what type of signals travel down neurons
electrical signals
what type of signals travel between neurons
chemical signals
sensory neurons
PNS –> CNS
interneurons
“talk” to other neurons
can be CNS or PNS
motor neurons
CNS –> PNS
cone snail sensory, inter, & motor
sensory input of PNS - cone snail’s siphon senses a fish
integration - sensory input sent to CNS
motor output (PNS) - proboscis sends thing out to inject fish w/ poison
which type of neuron is affected by Lou Gehrig’s disease?
motor neuron
membrane potential
voltage across a plasma membrane
voltage
electrical charge difference
resting potential
membrane potential of a neuron that is not transmitting signals
-70mV
what forms the resting potential
differences in ions across the plasma membrane
distribution of ions in membrane
Na+ = sodium - more outside cell
K+ = potassium - more inside cell
A- = anions (negatively charged ions)
polarization of cell
more positive ions outside of cell
INSIDE of cell is relatively MORE NEGATIVE than the outside
selective permeability
channels only let certain things through
are ion channels mostly open or closed in a
neuron at rest
closed
keeps Na+ on 1 side & K+ on the other side
sodium potassium pump
moves Na+ ions out of the cell & K+ into the cell in a 3:2 ratio
active transport
why are sodium potassium pumps important
for making sure the inside stays more negative
concentration gradient w/ Na+ & K+
concentration gradient pressures Na+ to enter the cell
pressures K+ to exit the cell
passive transport
voltage-gated ion channels
electrical signals from other neurons cause ion channels to open
change in membrane potential (voltage) causes ion channel to open
hyperpolarization
inside becomes MORE negative
channel opens, K+ leaves, cell becomes more negative
depolarization
inside becomes more positive
Na+ channel opens, Na+ enters, neuron becomes less negative
graded potentials
depolarization & hyperpolarization under the threshold
the stronger the stimulus, the larger the change in membrane potential
what happens when a depolarization crosses the “threshold potential”
action potential
not a graded response
action potential
brief all-or-none depolarization of a neuron’s plasma membrane
type of signal that carries info along axons
size & shape of action potentials
size & shape of each one is the same
a stronger stimulus generates more action potentials
stages of action potential
- resting state
- depolarization
- rising phase
- falling phase
- undershoot
- restoration of resting potential
- resting state of action potential
Na+ & K+ channels are closed
- depolarization of action potential
Na+ channels open
Na+ diffuses into the cell
- rising phase
MANY Na+ channels open
Na+ rushes into the cell
positive feedback
- falling phase
K+ channels open
K+ rushes out of the cell
- undershoot
K+ slowly closing
Na+ inactivated
refractory period
brief period when a neuron cannot generate an action potential
- restoration of resting potential
K+ channels close
sodium potassium pump
moving Na+ inside neuron
moving K+ outside neuron
helps restore resting membrane potential
tetrodotoxin
blocks Na+ channels
used by puffer fish for defense
alpha & beta toxins
shifts opening & closing of Na+ channels
used by scorpions to capture prey
apamin
blocks K+ channels
used by honey bees for defense
how do action potentials move down the axon
the depolarization of one region of the axon stimulated depolarization of the next region
why doesn’t the action potential move backwards
Na+ channels become inactivated
what determines conduction speed of an axon
axon diameter
myelin sheath
How can axons send rapid signals in humans even though axons are small
a myelinated axon is faster than a giant axon 40x its size
> 2000 myelinated axons can be packed into the space occupied by just 1 giant axon
nodes of ranvier
gaps in myelin sheath where action potentials are generated
concentrated w/ sodium ion channels
saltatory conduction
action potentials are “jumping” down the length of the axon
synapse
site of communication between the synaptic terminal & another cell
presynaptic cell
neuron 1
sending signal
postsynaptic cell
neuron 2
receiving signal
chemical synapses
a chemical acts as a signal between cells
electrical synapses
electrical current flows from cell to cell
vesicle
a packet of neurotransmitters
neurotransmitter
a chemical messenger between neurons
synaptic cleft
gap between pre & post synaptic neurons
chemical synapse @ synaptic terminal
- action potential depolarizes presynaptic membrane
- voltage-gated Ca2+ channels open
Ca2+ enters the neuron - Ca2+ causes vesicle to fuse to membrane & release neurotransmitter –> exocytosis
EPSP
excitatory postsynaptic potentials
depolarization
IPSP
inhibitory postsynaptic potentials
hyperpolarization
ionotropic receptors
neurotransmitters bind to receptors that are part of ion channels
open ion channel
change membrane potential
rapid, short lasting
If one input to a postsynaptic neuron is usually too weak to initiate an action potential,
then how are action potentials elicited
synaptic integration / summation
epsp & ipsp are added together
where does synaptic integration take place
axon hillock
metabotropic receptors
neurotransmitters bind to a receptor that is not part of an ion channel
activates a signal transduction pathway
slower, longer lasting
can open an ion channel or activate another molecule
