Chapter 12 part 2 Flashcards
resting neuron
difference in electrical signal across the cell membrane
difference in electrical charge=
-2 things
electrical potential difference = transmembrane potential
difference in electrical charge refers to
difference in charge across the plasma membrane
transmembrane potential
- definition
- how do you measure it
- mV
- what does the sign refer to
- more + or - in the inside
- key concept
- varies from moment to moment depending on the cell
- using a volt meter
- 70mV
- to charges inside the cell
- more -
- all neutral activities begin with a change in the resting membrane potential
what makes the resting membrane potential -70mV
intracellular and extracellular fluids are different from eachother because plasma membrane is selectively permeable
resting cell membrane
- K+ outside the cell
- K+ inside the cell
- Na+ outside the cell
- Na+ inside the cell
- protein -
- low
- high
- high
- low
- negative inside the cell
what is located inside the resting
-3 things
- greater concentration of K+
- negatively charged protein
- other large anionic molecules
what is located outside the cell in the resting cell
-1 things
greater concentration of Na+
what is responsible for establishing these concentration gradients for Na+ and K+?
Largely due to the Na+/K+ exchange pump
how leaky are sodium leak channels
not very leaky because the membrane in a resting neuron is not very permeable to sodium
how leaky are potassium leak channel?
very leaky
action potential
- definition
- where does it begin
- involves
- an abrupt change in the electrical potential difference across the cell membrane which occurs after a stimulus
- at the hillock
- another set of channel proteins in the cell membrane (voltage gated sodium channel and voltage gated potassium channel)
4 steps for development of an action potential
- resting neuron
- application of stimulus
- depolarization
- repolarization
application of a stimulus
- definition
- voltage change
localized change in resting potential causes depolarization to threshold
- -70 mV to -60 mV
depolarization
- what happens to channels
- what happens to plasma membrane
- what happens to Na+
- voltage change
- voltage gated sodium channel opens when threshold is reached
- becomes permeable to Na+
- Na+ quickly flows down its concentration gradient
- -60 mV to +10 mV
Repolarization
- what happens to channels
- what happens to sodium permeability and sodium movement
- what happens to potassium permeability and movement?
- voltage
- voltage gated sodium channel closes around +30 mV and voltage gated potassium channel opens
- stops
- plasma membrane become permeable to K+ and it flows out of cell
- +30 mV to -90 mV to -70mV
absolute refractory period
period when membrane cannot respond to a new stimulus
relative refractory period
Na+ channels are returning to normal resting levels and membrane can respond to a larger than normal stimulus
impulse conduction would be faster in
-why
an axon with a larger diameter
-because a larger diameter offers lower resistance-ions can move more freely within the cytoplasm
All-or-nothing principle for an action potential
if a stimulus is strong enough to initiate an action potential, then the action potential will be conducted at a constant magnitude and rate along the length of the axon
an action potential at the beginning of the axon equals
an action potential at the end of the axon
how does the neuron transmit info about the strength and duration of stimulus that started the action potential?
- definition
- 1 AP/sec produces
- 100 AP/ sec produces
frequency of action potential propagation
- produces a muscle twitch
- produces muscle tenancy
2 types of communication between neurons
- electrical
2. chemical
electrical communication
-2 things
- presynaptic and post synaptic membranes are locked together at gap junction
- action potentials propagate from 1 cell to the other
chemical communication
-2 things
- cells are not directly attached to eachother
- cells use neurotransmitters to communicate with eachother
5 events occuring at the synapse
- action potential arrives and depolarizes the synaptic knob
- extracellular Ca++ ions enter through open channels and trigger exocytosis of acetylcholine
- acetylcholine diffuses across synaptic cleft and binds to receptor on the postsynaptic membrane
- causes opening of Na+ channels on postsynaptic membrane= depolarization of postsynaptic membrane
- depolarization ends as acetylcholine is broken down into acetate and choline by acetylcholinestrase
2 major groups of neurotransmitters
- excitatory
2. inhibitory
excitatory neurotransmitters
causes depolarization of the postsynaptic membrane and promotes generation of an action potential
inhibitory neurotransmitters
causes hyperpolarization of the postsynaptic membrane and supresses generation of an action potential
-will go from -70 mV to -90mV
5 examples of neurotransmitters
- Acetyl choline (can be either)
- dopamine (can be either)
- seratonin (can be either)
- Norepinephrine (excitatory)
- Gamma-aminobutynic acid (GABA) (inhibitory)
what does the exact effect of particular neurotransmitter depend on?
the receptor of the postsynaptic neuron not the neurotransmitter
postsynaptic potential
develops in post synaptic membrane in response to neurotransmitter
- Excitatory postsynaptic potential (EPSP)
- inhibitory postsynaptic potential (IPSP)
- Excitatory postsynaptic potential (EPSP)
EPSP
causes depolarization of post synaptic membrane
IPSP
causes hyperpolarization of post synaptic membrane
how much effect do ind. postsynaptic potentials have on the postsynaptic membrane
minimal effect
2 types of summation
-end result
- temporal
- spatial
- action potential generation in postsynaptic cell
temporal summation
- definition
- degree of depolarization of postsynaptic membrane
- key concept
- increased frequency of stimulus applied at a single synapse
- increases every time an action potential causes the release of a neurotransmitter from the pre-synaptic neuron
- series of small steps brings the hillock to threshold
spatial summation
- definition
- how many synapses are activated at the same time
- simultaneous stimuli applied at different locations have cumulative effect
- multiple synapses activated at the same time
5 functional organization of neurons
- diverging
- converging
- serial
- parallel
- reverberating
diverging
-definition
-permits what
ex
- spread of info from one neuron to several neurons
- permits a broad distribution of signal
- occurs when sensory neurons bring info to CNS
converging
- definition
- ex
- several neurons synapse on a signal postsynaptic neuron
- subconscious and conscious control of breathing
serial
- definition
- ex
- info relayed in a stepwise fashion
- sensory info relayed from 1 part of brain to another
parallel
- definition
- example
- several neurons process same info simultaneously
- complex response when stepping on a sharp object
reverberating
- definition
- ex
- like a positive feedback loop that involves neurons
- very complicated circuits in the brain that control consciousness
