LAB Final Part 2 (Nervous system) Flashcards
nerve cells that transfer information within the body
neurons
what are the two types of signals that neurons use to communicate?
electrical signals (long-distance) and chemical signals (short-distance)
what happens in the ganglia (clusters of neurons) and a more complex organization of neurons the brain?
processing of information
what does neuron organization and structure reflect?
function in information transfer
what does the neuron (cell) exempllify?
close fit between form and function
where are most of the neuron’s organelles?
in the cell body
what do most neurons have and what are they?
dendrites, highly branched extensions that receive signals from neurons
what is the much longer extension that transmits signals to cells at synapses?
the axon
the cone-shaped base of an axon
axon hillock
the synaptic terminal of one axes passes information across the synapse in the form of chemical messengers
neurotransmitters
a junction between an axon and another cell
synapse (synaptic cleft)
how is information transferred?
from a presynaptic cell (a neuron) to a postsynaptic cell (a neuron, muscle or gland cell)
what are most neurons nourished or insulated by?
cells called glia or glial cells
what do sensors detect external stimuli and internal conditions and transmit information along?
sensory neurons
where do sensory information get sent to the brain or ganglia?
where interneurons integrate the information
what does the motor output leave the brain by and what does that trigger?
motor neurons, triggers muscle or gland activity
what establishes the resting potential of a neuron?
ion pumps and ion channels
the membrane potential of a neuron no sending signals
resting potential
how do changes in membrane potential act act as?
signals, transmitting and processing information
three stages of how the Nervous system processes information (SIM)
1) sensory output
2) integration
4) motor output
where integration takes place, this includes the brain
central nervous system (CNS)
carries information into and out of the CNS
peripheral nervous system (PNS)
what does the neurons of the PNS when bundled together form?
nerves
in a mammalian neuron at resting potential what concentration is the highest inside the cell and what is the highest outside the cell?
inside: K+
outside: Na+
what does sodium-potassium pumps use the energy of ATP to maintain?
K+ and Na+ gradients across the plasma membrane
what do the concentrations K+ and Na+ gradients represent?
chemical potential energy
what do ion channels in the plasma membrane convert chemical potential into?
electrical potential
characteristics of a neuron at resting potential(3) (MFK)
1) many open K+ channels
2) fewer open Na+ channels
3) K+ diffuses out of the cell
what is the major source of membrane potential?
the resulting buildup of negative charge within the neuron
types of ion channels (3) (SPS)
1) sodium/potassium pump
2) potassium (K+) channels
3) Sodium (Na+) channels
what type of ion channel is sodium/potassium pump?
active
characteristics of the ion channel, potassium (K+) channels (3) (PSS)
1) passive
2) some are always open
3) some are gated and closed when resting
characteristics of the ion channel, Sodium (Na+) channels
1) passive
2) gated and closed when resting (only open for certain circumstances like membrane potential)
what can resting potential be modeled by?
an artificial membrane that separates the two chambers
charactertistics of the resting potential modeled by an artificial membrane (3) (CKN)
1) the concentration of KCI is higher in the inner chamber and lower in the outer chamber
2) K+ diffuses down its gradient to the outer chamber
3) negative charge (CI) builds up in the inner chamber
what gradients are balanced at equilibrium?
both the chemical and electrical
charateristics inside a resting potential (2) (CR)
1) the currents (net flow) of K+ and Na+ are equal and opposite
2) the resting potential across the membrane remains steady
what are action potentials?
signals conducted by axons
what do neurons contain that causes changes in membrane potential to occur that opens or close in response to a stimuli?
gated ion channels
when gated K+ channels open what happens?
K+ diffuses out, making the inside of the cell more negative (hyperpolarization)
increase in magnitude of the membrane potential
hyperpolarization
what triggers depolarization?
opening other types of ion channels
a reduction in the magnitude of the membrane potential
depolarization
what is an example of depolarization?
occurs if gated Na+ channels open and Na+ diffuses into the cell
changes in polarization where the magnitude of the change varies with the strength of the stimulus
graded potentials
what are graded potentials NOT and what do they have an effect on?
they are not nerve signals that travel along axons and they have an effect on the generation of nerve signals
if a depolorization shifts the membrane potential sufficiently what massive change in membrane voltage occurs?
action potential (not graded)
what do action potentials have and what do they transmit over long distances?
they have a constant magnitude and they transmit signals
why do action potentials arise?
because some ion channels are voltage-gated and open or close when the membrane potential passes a certain level
what can an action potential be considered as?
a series of stages
characteristics of an action potential at resting potential
- most voltage-gated sodium (Na+) and potassium (K+) channels are closed
what happens second when the action potential is generated?
- voltage-gated Na+ channels open first and Na+ flows into the cell
what happens third when the action potential is generated during the rising phase?
- the threshold is crossed and the membrane potential increases
what happens fourth when the action potential is generated during the falling phase?
- voltage-gated Na+ channels become inactivated; voltage K+ channels open and K+ flows out
what happens fifth when the action potential is generated during the undershoot?
- membrane permeability to K+ is at first higher than at rest, then voltage-gated K+ channels close an resting potential is restored
what happens sixth when the action potential is generated during the refractory period?
- after an action potential, a second potential cannot be initiated
what is the refractory period of an action potential a result of?
temporary inactivation of the Na+ channels
at the site where the action potential is generated (usually the axon hillock) what depolorizes the neighboring region of the axon membrane?
an electrical current
how do action potentials travel?
only in one direction toward the synaptic terminals
what does inactivated Na+ channels behind the zone of depolarization prevent?
the action potential from traveling backwards
what does the speed of an action potential increase with?
the axon’s diameter
in vertebrates what are axons insulated by and what do they cause?
myelin sheath which causes an action potential’s speed to increase
what are myelin sheaths made of?
glia- oligodendrocytes in the CNS and Schwana cells in the PNS
where do neurons communicate with other cells?
at synapses
what do electrical curren tflows go from one to another through electrical synapses?
through gap junctions
what does a chemical neuron carry at chemical synapses?
information between neurons
what are most synapses?
chemical synapses
where does the presynaptic neuron synthesize and package the neurotransmitter?
in synaptic vesicles located in the synaptic terminal
what does the action potential cause the release of?
the neurotransmitter
where does the neurotransmitter diffuse across and what is it received by?
across the synaptic cleft and if received by the postsynaptic cell
where does direct transmission involve the binding of neurotransmitters to?
ligand-gated ion channels
where are the ligand-gated ion channels located?
in the postsynaptic cell
what does neurotransmitter binding cause?
ion channels to open, generating a postsynaptic potential.
two categories of postsynaptic potentials
1) excitatory postsynaptic potentials (EPSPs)
2) inhibitory postsynaptic potentials (IPSPs)
depolarizations that bring the membrane potential toward threshold
excitatory postsnyaptic potential (EPSPs)
hyperpolarizations that move membrane potential further from threshold
inhibitory postsynaptic potential (IPSPs)
where do most neurons have many synapses on?
their dendrites and cell body
what is a single EPSP usually too small to trigger?
an action potential in a postsynaptic neuron
what occurs if two EPSPs are produced in rapid succession?
an effect called temporal summation occurs
EPSPs produced nearly simultanously by different synapses on the same postsynaptic neuron add together
spatial summation
what can the combination of EPSPs through a spatial and temporal summation trigger?
an action potential
through summation, what can an IPSP counter?
the effect of an EPSP
what does the summed effect of EPSP s and IPSPs determine?
whether an axon hillock will reach threshold and generate an action potential.
in some synapses what does a neurotransmitter bind to?
a receptor that is metabotropic
if a neurotransmitter binds to a receptor that is metabotropic what does movement of ions through a channel depend on?
one ore more metabolic steps
what does binding of a neurotransmitter to a metabotropic receptor activate?
a signal transduction pathway in the postsynaptic cell involving a second messenger
compared to ligand-gated channels what does the effects of the second messenger systems have?
a slower onset but lasts longer
what may a single neurotransmitter bind specifically to?
more than a dozen different receptors
when does receptor activation and postsynaptic response cease?
when neurotransmitters are cleared from the synaptic cleft
what are neurotransmitters removed by? (3) (SIR)
1) simple diffusion
2) inactivation by enzymes
3) recapture into the presynaptic neuron
a common neurotransmitter in vertebrates and invertebrates
acetycholine
what is acetycholine involved in? (3) (MML)
1) muscle stimulation
2) memory formation
3) learning
what disrupts acetycholine neurotransmission?
a number of toxins
what do the toxins include that disrupts acetycholine neurotransmission?
1) nerve gas
2) sarin
3) botulism toxin produced by certain bacteria
what is acetycholine just one of?
more than 100 known neurotransmitters
what 4 classes does the remainder of neurotransmitters fall into? (ABNG)
1) amino acids
2) biogenic amines
3) neuropeptides
4) gases
what do biogenic amines include? (3) (NDS)
1) norepinepherine
2) dopamine
3) serotonin
mobilizes brain and body for action, fight or flight
norepinephrine
reward motivated behavior
dopamine
mood, appetite and sleep
serotonin
where are biogenic amines active in?
the CNS and PNS
what are local regulators in the PNS?
gases such as nitric oxide (NO) and carbon minoxide (CO)
unlike most neurotransmitters what is not store in cytoplasmic vesicles but is synthesized on demand?
nitric oxide (NO)
when is nitric oxide (NO) broken down?
within a few second of production
although inhaling CO can be deadly what does the vertibrate body do?
synthesizes small amounts of it, some of which is used as a neurotransmitter
where are action potentials formed only at?
nodes of Ranvier
gaps in the myelin sheath where voltage-gated Na+ channels are found
nodes of Ranvier
a process where action potentials are myelinated axons jump between the nodes of Ranvier.
saltatory conduction
