Neurons, Cellular network properties

anterograde transport is?

cell body to axon terminals (fast)

retrograde transport is?

from axon terminals to cell body (fast)

since myelin is void at nodes of ranvier, what is there instead?

clusters of voltage gated Na and K channels

what is saltatory conduction & how does it relates to nodes of ranvier?

saltatory conductions in neurons refers to the impulse "jumping" to the next node for a faster response, depolarization at one node to next -- a myelinated axon can send a signal as fast as 150 m/sec

can neurons regenerate?

in cns its unlikely for them to regenerate. in the PNS, the part that has cell body attached will proceed while the cut off part will dintergrate

what do Schwann cells do when there is neuron damage?

they will secrete neurotropic factors

what is the typical resting membrane potential of a neuron?

at -70 mV

if the ECF concentration of K went from 3 to 5 mM, what happened to the membrane potential of the cells?

the membrane potential becomes less negative; this is because potassium has a positive charge = less negative

what is the difference between graded and action potentials?

Graded potentials are used for short distance communication (vary in strength), while action potentials are brief (large depolarizations) that are rapid signals over long distances

which is stronger for graded potentials?

signals closer to stimulus will be faster as signals that have disappated over the cell lose their strength as they get farther

why do graded potentials lose strengh?

cytoplasmic leak and current leak

is excitatory depolarizing or hyperpolarizing

excitatory = depolarizing

inhibitory = hyperpolarizing

true or false: a graded potential can release an action potential if the stimulus is strong enough?

True, a graded potential that has a strong enough stimulus can reach the trigger zone in the axon hillock to trigger an action potential afte suprathreshold

is potassium linked to depolarization or hyperpolarization?

hyperpolarization

true or false: action potentials follow the 'all or nothing' phenomenon?

true!!!!!!

depolarization occurs when?

Na+ voltage gated channels open, allowing Na+ to influx into the cell

what voltage gated channels close at the peak of action potential?

Na+ voltage gated channels

repolarization occurs with what ion?

slower voltage K+ gated channels open so that it can efflux out of the cell

how do anestetics like lidocaine, xylocaine, and novocain work?

drugs like lidocainee will bind to the Na+ gated channeles on the neuronal membrane and prevent their entry, meaning no action potential is generated

-is used in surgery to ensure pain is subdued

how does diethyl ether work?

it causes K+ gates to stay open, which leads to hyperpolarization that can't discharge

-used in sedation and euphoria

what does curare and alpha-bungarotoxin do the nervous system?

the toxins relax the skeletal muscles that then become paralyzed

what is temporal summation?

when one presynaptic neurons release 2 subthreshold signals close enough in time to sum into triggering an action potential

what happens in spatial summation?

when multiple subthreshold signals from neurons come together to reach the trigger zone to generate an action potential

what happens in synaptic inhibition?

2 excitatory neurons may fire, but am inhibitory nueron also fires that prevents any action potential from generating

global vs selective presynaptic inhibition?

global is when an inhibitory neuron won't allow an action potential to generate AT ALL while selective allows it to go through, but then blocks the release of a neurotransmitter

what neurotransmitter is key in potentiation?

glumate with AMPA/DMDA receptors

what is the brains inhibitory molecule?

GABA and works by hyperpolarizing target cells opening Cl- gates

what is the CNS excitatory molecule?

glutamate

-has receptors for NMDA and AMPA

what is local current flow?

a wave of depolarization that moves through the cell

what does voltage gated channels mean?

channels open due to membrane potential like when Na+ gates open during depolarization

what does mechanically-gated channels mean?

these channels open in response to mechanical stimulation in the form of vibration, tissue stretching, or pressure like the auditory receptors in the inner ear

what do chemically gated channels mean?

chemically gated channels open and close due to a chemical stimulus like odorants binding to olfactory receptors

what do electromagentic gated channels mean?

these channels open in response to light, which can only be found in the eye's retina with their photoreceptors

what is the resting value for K+

5mM (3.5-5 is normal),-90 mV, and 150 mM

what is the resting value for Na+

145 mM (135-145 is normal), 15 mM, +60 mV

what is the resting value for Cl-

108 mM (normal is 100-108), 10 mM (normal is 5-15), and -63 mV

what is the resting value for Ca2+

1 mM, 0.0001 mM, and 130-135 mV

for fast axonal transport, how fast can it move?

moves organelles at rates up yo 400 mm/day

for slow axonal transport, how slow does it move?

moves material by axoplasmic flow at 0.2-0.25 mm/day

how do axons cary outgoing signals?

thru the axon hillock

how do dendrites recieve incoming signals?

with dendritic spine

what do epydemal cells do?

lines the brain and CNS-- creates CSF and forms the epithelium known as ependyma and the the neural cell source

what do satellite or amphicytes do?

non myelinating Schwann cell thought to play a role in controlling the chemical environment of neurons

what do microglia in the CNS and Schwann Cells in the PNS secrete?

neurotropic factors when there is neural damage

What happens in Multiple Sclerosis?

it is an autoimmune diseases where the myelination sheath is degraded in the body leading to loss in muscular control , vision and speech impairments

-relapses and periods of remission

this means that conduction along the axon is slowed down and

what happens in the damaged CNS cells?

glial cells of the CNS will release factors that inhibit axonal growth

name the steps in neuronal repair in the PNS

1. axoplasm leaks out & seals the damaged end while the distal segment swells

2. schwann cells sends out signals alerting of tissue damage

-distal axon segment degeneration

-myelin sheath unravels

-cell debris removed

3. Schwann cells sends out neurotropic factors to ensure cell body health and encourage axon regrowth

axon acts as growth cone

what does the resting membrane potential primarily rely on?

-K+ concentration gradient and the cells resting permeability to K+, Na+ and Cl-

what level does action potential have to reach in order for voltage gated channels to open?

the threshold needs to reach -55 mV otherwise an action potential will not happen ITS ALL OR NOTHING

what is the absolute refractoty period due to and what happens?

it is ide to Na gates closing & resetting and another action potential cannot fire

what is the relative refractory period due to?

it coincides with the still open K+ gates and allows an action potential with a suprathreshold stimulus but is LESSER in magnitude

what is Guillian Barre syndrome?

when a person's immune system attacks their nerves and sensation is lost after initial weakness in hands and feet

-one the most common way to get GB is from an infection with Campylobacter jejuni (causes diarrhea)

true or false: hyperkalemia brings the neuron closed to threshold to depolarize?

true, the opposite is also true: hypokalemia pushes the threhold farther

what are the derivatives of acetylcholine and where is it found?

choline (membrane phospholipids) and acetylCoA from the citric acid cycle-- found in axon terminals of neurons

what is another word for cholinergic receptors and what do they do?

AKA nicotinic receptors. they are found on skeletal muscles and in the ANS & CNS

-they have monovalent Na+ / K+ channels

what do muscarinic receptors do in ACH?

they have G-protein coupled receptors

-found in the CNS and the parasympathetic division of PNS

what are some of the amine derived neurotransmitters in the CNS?

histamine from histidine

serotonin from tryptophan

dopamine, noepinephrine, and epinephrine from tyrosine

what do adrenergic/noradrenergic neurons secrete?

noepinepherine

what do adrenergic receptors bind to and what are their classifications?

epinephrine & noepinephrine

-they activate G protein coupled receptors and they have a/b classes

what is the excitatory transmitter in the brain?

aspartate and works by depolarizing target cells

what do glycine and D-serine do in terms of neurotransmitters?

they enhance the effect of glutamate, which is excitatory in the CNS

peptide hormone examples and functions

^substance P and opioid peptides (enkephalins/endorphins); neurotransmitters, neurpmodulators, and neurohormones

^ vasopressin, atrial natriuretic peptide, & cholystokinin act as neurotransmitters and neurohormones

purines like adenosine, AMP, and ATp bind to?

Purine receptors (GPCRs)

what are examples of gases that diffuse into the cell and act as neurotransmitters?

CO2, NO, and H20

what are examples of lipid neurotransmitters and what do they bind to?

eicosanoids and endogenous ligands bind to cannabinoid receptors

true or false: a stronger stimulus releases more neurotransmitter?

true, a single action potential results in the release of a constant amount of neurotransmitter and if its strong, more action potentials = more neurotransmitter

name the steps in neurotransmitter release:

1. an action potential depolarizes the axon terminal

2. depolarization triggers voltage gated Ca2+ gates to open and Ca2+ enters the cell

3. Ca2+ entry triggers exocytosis of synaptic vesicle contents

4. the neurotransmitter diffuses across the synaptic cleft and binds to postsynaptic receptors

5. postsynaptic cell gets a reponse after binding with neurotransmitter

what is the shorter pathway for neurotransmitters?

vesicles fuse with presynaptic membrane to form fusion pore and the neurotransmitters pass through a channel

what happens in synaptic termination?

acetylcholinerase breaks down acetylcholine in the synaptic clefts and can be recycled or taken up by other cells to diffuse out

what is the recycling pathway of acetylcholine?

1. acetylcholine is made from choline and acetylcholine

2. in synaptic cleft, ACH broken down by acetylcholinesterase

3. choline gets back into axon terminal via cotransport with Na+

4. the broken down choline is reused to make more ACh

divergence and converge in the CNS does what?

changes the synaptic plasticity__ can be:

-short/long term

-enhance/reduce synaptic activity

divergence = 1 to multiple

convergence = multiple to 1

divergence looks like and examples

divergence can be multiple synapses on a cell body of a neuron so they can provide multiple inputs

ex. purkinje cells in cerebellumg

slow synaptic potentials involve?

G-protein-coupled receptors; second messengers

fast synaptic potetnials involve?

the opening of ion channels

- excitatory postsynaptic (EPSP)= depolarizing

-inhibitory postsynaptic potential (IPSP) = hypolarizing

how can long term potentiation alter synapses?

activity at the synapse induces sustained chnages in quality or quantity of connections

-disorders of this like Parkinsons, schizophrenia and some depressions are consequences of this