lecture 6: chemical & electrical signal transformation Flashcards
neurons are specialized and terminally differentiated _______ cells
- sensory:
- motor:
- interneurons:
epithelial cells
- afferent
- efferent
- integration/coordination
cellular organs:
- condensed, lost replicative functions, no centriole
- protein/peptide synthesis
- lipid synthesis
- modification of synthesized protein/peptide and lipid for sorting
- degrade metabolic wastes
- power plant
- neurofilaments, unique shape
- nucleus
- rough ER/ nissl body
- smooth ER
- golgi apparatus
- lysosome and peroxisome
- mitochondria
- cytoskeletal structures
what is a nissl body?
helps with protein synthesis in the rough ER
What is neuron reception and summation of signals?
reception: 1st step in communication, dendrites catch neurotransmitters
summation: neurons sum up all signals received (inhibitory & excitatory)
MOST neurons have only ______ axon, may or may not be ________
Neurons can have _____ of axon terminals
one; myelinated
hundreds
What are enzymes for neurotransmitter synthesis and activation:
Mitochondria, lysosome/peroxisome
Where axon form and extending out, the initiation of AP:
hillock
What is unique about pseudounipolar neurons:
initiation of action potential by peripheral process (touch, pressure, temp.)
Neuron axons form synapses with ______ cells through _______
The release of neurotransmitters = transformation from _________ to _______
target; terminals
electrical to chemical
Which neuron in the cerebellar cortex is the only one providing afferent axons to other brain structures and which neurotransmitter does it release?
Purkinje cell; GABA
Types of Neurons:
1. multiple dendrites from the soma:
2. dendrites mainly on one end of the soma:
3. one hillock with dendrites on the axon
4. one hillock then divides the axon into 2 branches
- multipolar
- bipolar
- unipolar
- pseudounipolar
Where are MOST of the sensory neurons?
pseudounipolar
Neurons: dendrites = limited cellular organs like axons but have ______ extension
Golgi apparatus
Transportation of molecules in the neurons —> rapid delivery = _______
(a) anterograde transportation:
(b) retrograde transportation:
active transportation
(a): from soma to dendrites/axons
(b): from dendrites/axons back to soma
Transportation of Molecules in the Neurons:
_________ elongating unidirectional to the plus direction (+)
_______ can be either way ( + or -) but only to the terminal in the axon
Tubulins
Dendrites
Transportation of Molecules in the Neurons:
Golgi apparatus extension directly delivers the ______ proteins in the tip
Differentiation of dendrites and axons:
tubulin
dendrites: both directions (+/-)
axons: uniform only (+) direction
Kinesin =
Dynein =
anterograde transportion
retrograde transportation (die*)
Which transportation can be hijacked by virus and bacterial toxins:
retrograde transporttaion, dynein
Is neuron cellular membrane is selectively permeable?
yes - allows some molecules to pass through while blocking others
- Facilitate the transport of water molecules; maintain water balance________
ion channels: _____ or ______
ion pumps:
water channel: aquaporin
leaking or gated
Na/K, atp dependent
The ion pumps consists of _______ and _____ dependent
Na+ (sodium) and K+ potassium); ATP
The polarity of the neuron cell membrane
-Osmotic:
-Electric:
Inside the neuron cellular membrane is more ______ due to the 2 potentials: _____ to _____, rest membrane potential
numbers of ions and molecules- related to movement of water
positive and negative charges- electrical potential for signaling
negative; -40 to -90 mV
Which cellular organs are located in the axons?
Mitochondria, lysosomes/peroxisomes, and enzymes
Ligand-gated: Lignad as _________, ion channel as _________ –> change in _________ potential
Voltage-gated: resting membrane potential increased to the _______ no ______ needed. Only opens when membrane potential ________
Modality gated: open or close based receptors such as:
neurotransmitters; receptors; membrane
threshold; ligand; reaches threshold
touch, pressure, heat, cold, light, sound wave
K+ can freely move cross membrane through _______ channel and is in charge of _______ membrane potential: polarized
leaking
resting
List the 5 phases of initiation of AP:
resting potential
slow depolarization/graded potential
fast depolarization/ action potential
repolarization
hyperpolarization
-70 mV =
> -70mV, ligand/modality gated Na+ =
> -55mV, threshold, voltage gated Na+
back to -70mV, voltage gated K+ and pumps
resting potential
slow depolarization/graded potential
fast depolarization/action potential
Hyperpolarization
Is the following statement True or False?
The voltage-gated sodium channels 2 gates open and close separately at different phases this means that both gates can close at the same time.
false; BOTH gates CANNOT close at the same time
Resting state =
AG:
IAG:
below threshold
closed
open
Activated state =
AG:
IAG:
fast depolarization
both gates are open
Inactivated state =
AG:
IAG:
repolarization + hyperpolarization
open
closed
Which proteins oversee anterograde and retrograde transportation along the axons separately?
Anterograde: kinesin
Retrograde: dynein
Is the following statement True or False? During the absolute refractory period, voltage-gated sodium channel APs will respond to any stimulus.
False: APs WILL NOT respond to any stimulus no matter how strong
Why can APs be induced in the relative refractory period but not in the absolute refractory period?
The IAG is engaged/closed during the absolute refractory period but is open in the relative.
_______ defines unidirectional conduction of APs by preventing immediate re-excitation
Refractory period
What is the flow of the Na+/K+ pumps during repolarization of neurons:
3 Na+ out and 2 K+ in
Na+/K+ pumps are ________ dependent and ________% of the energy consumed by the brain
ATP; 20-40%
Generally, APs are unidirectional conduction but AP in the middle of axons spreads bidirectionally under experiment. How so?
artificial stimulus- direction electrical stimulation
Axonal reflex: both _______ and ______ on one axon
Example:
afferent (skin detecting P! ful stimulus) and efferent (muscles near the site of injury contract)
papercut: P! and inflammation but no bleeding
What blocks the backflow of action potentials?
activated and then inactivated voltage-gated sodium channels
True or False:
Refractory period = bidirectional spread
False: unidirectional - ensures APs flow in one direction along axon
Which of the 5 phases of AP follows the absolute refractory period?
repolarization
*depolarization, absolute refractory period, REPOLARIZATION, end of absolute refractory period
When there are multiple AP along one axon: _____ of stimuli represented by _____ of AP
intensity; frequency
Why is there an absolute refractory period phase for action potential initiation?
Only one AP at a time and backflow prevention
layers of lipid, insulation-
small gap, only voltage gated sodium channels -
myelins sheath
node of ranvier
Node of Ranvier: no __________ due to outflow of K+
hyperpolarization
Axons only need regeneration AP in the nodes, fast pass in the internodes. How does this happen?
AP conduction jumps from one node to another: known as saltatory conduction
Giant squid axon is myelinated or unmyelinated?
How many vertebrae (mammal) myelinated axons can be bundled in a giant squid axon?
unmyelinated
160,000
There are different types of myelin sheath in CNS and PNS:
CNS: oligodendrocytes
PNS: Schwann cells
CNS:
Oligodendrocytes wrap around ________axons, and some nonmyelinated axons in CNS: get wrapped by ________
multiple
astrocytes
PNS:
Schwann cells wrap around a _______ axon, and nonmyelinated axons _____ together and wrapped by Schwann cells ________ myelin sheath.
single; bundle
without
Communication between myelin layers is located where?
Local ions replenish ______ during repolarization.
gap junctions
fast
What is repolarization and how does neuron repolarize?
AP returns to its resting membrane potential
sodium-potassium pump transports Na+ out and K+ in
*(3 Na+ out = 2 K+ in)
What two pathologies affect myelin sheath:
CNS (1)
PNS (1)
CNS: multiple sclerosis (MS)
PNS: Guillan Barre Syndrome
Which pathology is being described:
Olfactory bulb/tract, CN II, optical nerve, and diencephalon are impaired/affected?
Multiple sclerosis
Gillian Barre affects Schwann cells or Oligodendrocytes?
Schwann cells
Target cells- neurons can synapse with: (3)
Terminal functional cells:
dendrites, soma, or axons/terminals
muscles & glands
Components of an electrical synapse: (2)
gap junctions, AP directional conduction (neuron can directly pass through gap junction to connected neuron)
Components of electrical synapse: axon terminal: vesicles with ___________, _________cleft, ________ membrane: receptors, __________ channels and ___ protien.
neurotransmitters, synaptic cleft, postsynaptic, ligand-gated, and G-protein coupled receptors
TRANSFORMATION of ELECTROCHEMICAL SIGNALS:
AP arrives at the presynaptic terminal of the chemical synapse
Depolarization opens Ca2+ channel: voltage-gated
Inflow of Ca2+ facilitates the docking of vesicles on the presynaptic membrane
Fuse vesicles with presynaptic membrane
Release neurotransmitters
Diffusion across the synaptic cleft
Bind to receptors on the postsynaptic membrane
Excitation: excitatory postsynaptic potential (EPSP)
__________ postsynaptic membrane
DOES NOT mean ______ initiation but ________
depolarize
AP; more likely
Inhibition: inhibitory postsynaptic potential (IPSP)
________ postsynaptic membrane
DOES NOT mean ______ initiation but ________
hyperpolarize
AP: less likely
What are the two receptors on the postsynaptic membrane:
ionotropic and metabotropic receptors
Which postsynaptic receptor is being described:
-fast: point to point specific
-one AP is enough
-small vesicles with different neurotransmitters to synaptic gap
ionotropic
Which postsynaptic receptor is being described:
-slow: can be point to area, nonspecific
-need multiple APs: longer Ca2+ channel
-large vesicles release neurotransmitters through exocytosis
metabotropic
Which postsynaptic receptor is associated with ligand-gated ion channels?
ionotropic
Single postsynaptic membrane potential: graded potentials are either _______ or _________.
Dissipation (become weaker) due to _________ and _______: spatiotemporal effects.
EPSP or IPSP
distance & time
stimuli from the same location or location with different timeframe
stimuli from different locations simultaneously
temporal summation
spatial summation
If the total summation results are over-resting potential but lower than the threshold can you have AP initiation?
If the total summation results are over the threshold can you have AP initiation?
What if the total summation results are lower than the resting potential?
No
Yes
inhibitory, hyperpolarized, and refractory activated
At the neuromuscular junction, __________ is the neurotransmitter responsible for transmitting signals.
Nicotinic acetylcholine receptor is a ligand-gated ion channel and the binding site is located on ___________ the of the receptor. It causes the ion channel to open, allowing the influx of sodium ions. The influx of sodium ions ultimately leads to _____________
acetylcholine (ACh)
alpha subunit
muscle
A synapse contains which components: (3)
presynaptic axon terminal
synaptic cleft
postsynaptic membrane
A patient is experiencing muscle weakness and flaccidity due to diminished Ca2+, which has impaired fusion of ACh.
Antibodies against:
Lambert Eaton Syndrome (LEMS): VGCC
A patient is experiencing muscle spasms due to blocked K+.
Antibodies against:
Isaacs’ syndrome: VGKC
A patient is experiencing muscle weakness, eye muscles are MOSTLY affected.
Antibodies against:
Myasthenia gravis disease
MuSK, LRP4, AChR
Fate of neurotransmitters: (4)
reuptake
degradation
diffusion away
endocytosis by postsynaptic membrane
What will happen when multiple depolarization signals arrive at the neuron dendrites and soma at the same time?
spatial summation
What are the two main ACH receptors:
Nicotinic and Muscarinic
Nicotinic (nAChRs) are generally associated with ____________ signaling in both the PNS and CNS.
fast, point-to-point, specific
In the CNS, muscarinic receptors play a role in _________
signaling =
neuromodulation
slow, point to area, nonspecific
Muscarinic- PNS: slow IPSP in smooth and caridac muscle= ___________ signaling in both the PNS and CNS.
slow, point to point, specific
Muscarine is an _______ for muscarinic acetylcholine receptors (mAChRs) in the brain. If consumed via mushrooms it can be ________
agonist; deadly
Anterograde Transportation: soma to terminals- for small molecular neurotransmitters
enzymes needed synthesized in the soma
transport to terminals
synthesize small molecular neurotransmitter in terminals
Anterograde Transportation: soma to terminals- for peptide neurotransmitters
pre-peptide synthesized in the soma
transport with enzymes to the terminals
degrade to form active neurotransmitter
Retrograde Transportation: terminals to soma-
molecules recovered from terminals
transported back to cell body for reuse
Which type of receptors for neurotransmitter are on the postsynaptic membrane?
Ionotropic (fast) and Metabotropic (slow) receptors
Receptors on the postsynaptic membrane define functions:
-Fast vs. Slow
-Excitatory vs. Inhibitory: depending on both the _______ and _______
-___________ inhibitory and excitatory for different bipolar neurons depending in the visual systems
transmitter and receptor
glutamate
Three amines: ARAS =
arousal and alert status of cerebral cortex
Main neurotransmitters: (4)
Amines
Amino acids
Neuropeptides
Other small molecules
