study guide 2 Flashcards
what did Volta invent/do
invented the electric battery. proved electricity could be generated chemically
what is a cells resting membrane potential
-70mV
what do Na+/K+ pumps do
help maintain osmotic equilibrium and membrane potential in cells
what do K+ leak channels do
allow K+ to diffuse out of cells (passive transport)
what are fixed intracellular anions
organic anions that cannot leave the cell
what do fixed intracellular anions do
help with the transport of gases, nutrients, and other molecules
why does the thickness of the PM matter
plays a key role in protein function
how much of the cells total potassium ions are needed to establish the resting membrane potential
a very small amount
what is the INTRACELLULAR/CYTOSOLIC concentration for SODIUM ions (Na+)
5-15mM
what is the EXTRACELLULAR concentration for SODIUM ions (Na+)
145mM
what is the INTRACELLULAR/CYTOSOLIC concentration for POTASSIUM ions (K+)
140mM
what is the EXTRACELLULAR concentration for POTASSIUM ions (K+)
5mM
what are the main excitable cells in the body
neurons and muscle cells
what are some key features of AP (6)
- depend on VGNCs or VG calcium channels
- all or nothing events
- brief duration (~2ms)
- self propagating down the length of an axon.
- unidirectional w a constant amp. and wave shape
- high velocity of propagation (0-100 m/s)
what are the 3 states of VGNCs?
closed (and ready to open)
open (and conducting Na+ ions)
inactivated (similar to open, but non conducting)
how can ion channels be selective
surround a central pore, guarded by selectivity filter. ions have to shed their sphere of hydration to pass through
what is a selectivity filter
a region of an ion channel protein that ddetermines the specificity of a particular channel
what is loligo/ why is it studied
squid w big axon
what is the AP threshold
enough Na+ leaks in for any portion of the inner membrane to depolarize (all or nothing principal)
if the AP threshold is met, what is the probability of an AP being triggered
50%
do all VGNC’s have to open to trigger an AP
no, only needs to be ‘a sufficient amount’
what happens 1-2ms after VGNCs open
enter inactivated state stopping the flow of sodium ions
what is repolarization?
membrane returns to resting membrane potential
how do local anesthetcs work?
block the inner mouth of VGNCs and prevent Na+ conduction and thereby prevent APs in sensory neurons
what does tetrodotoxin (TTX) do
plugs the EXTRACELLULAR mouth of a VGNC pore
where does TTX come from
pufferfish, porcupine fish, ocean sunfish, triggerfish, blue ringed octopus, rough skinned new, moon snail
what is myelin
a fatty insulating sheath that surrounds nerves in the brain and spinal cord
what cells make myelin
schwann cells
what does myelination do for a neuron (2)
- increases the propagation velocity of APs
- decreases metabolic energy expenditure by the neuron (bc the Na/K pups dont need to transport as many ions post AP)
what are the gaps in the myelin sheath called
nodes of ranvier
know what an axon hillock is
ok
what ion channels are found in the nodes of ranvier
VGNCs
what is saltatory conduction
AP jumps from one node of ranvier to the next, AP only occurs at nodes bc VGNCs are only present at the nodes
what is a synapse
a point of very close physical contact between a neuron and another cell
what are the different kinds of synapses
electrical, chemical (more??)
where would you find a gap junction
electrical synapses
explain connexins and connexons
6 connexins (individual proteins) make up 1 connexon
2 connexons form 1 gap junction
what are skeletal muscles fibers encased in
connective tissue
each skeletal muscle fiber in an adult human is innervated by how many presynaptic terminals of a somatic motor neuron
a SINGLE presynaptic terminal of a SOMATIC MOTOR NEURON
what is a motor unit
basic functional units of a skeletal muscle
why wouldnt all the muscle fibers be innervated by just one motor neuron
bc if there was just one innervating everything it would severely limit muscle’s ability to produce graded movements
why study the NMJ
big and easy to find w microscope
also very hardy can survive in petri dish for a long time
what are some unique features of the NMJ
junctional folds to incrase surface area
what neurotransmitter is released at the NMJ
Acetylcholine (ACh)
how much excess neurotransmitter is secreted at the NMJ and why
3X of ACh secreted as a safety factor to endsure muscle contraction
once a neurotransmitter like ACh is released what happens to it
binds to something opening some kind of gated channel to allow sodium ions to flow into the postsynaptic cell (i couldnt find this one on the ppt and your study guide answer was too vague)
what special enzyme is present in the snaptic cleft at the NMJ
acetylcholinesterase (AChE)
explain this https://imgur.com/a/wGXjKDm
do it
what are myofibrils
bundles of myofilaments
what filaments are found in myofibrils
actin and myosin
what are thick filaments made of
myosin II dimers
what are thin filaments made of
actin
what is a sarcomere
the contractile unit of a muscle fiber
what are the 2 binding sites for on a myosin head
one for actin one for ATP`
what are Z disks
protein that anchors the thin filaments and connects the myofibrils to each other
what attaches to a Z disk
I band (isotropic band)
what are I bands
Isotropic bands- actin bands (lighter)
what are A bands
anisotropic bands- myosin bands (darker)
whats an M line
a spot on the myosin filament where there are no myosin heads present- anchor for thick filaments
what shortens during muscle contraction
sarcomeres shorten bc actin filaments slide relative to myosin filaments and the distance between adjacent Z disks becomes shorter
do the filaments shorten during contraction
NO
why is release of calcium so important for contraction
calcium binds to troponin and myosin binding site is exposed (on actin)
what is troponin
a regulatory protein that moves tropomyosin aside and exposes myosin binding sites on actin when calcium is released during muscle contraction
what is tropomyosin
long, fibrous protein that winds around actin fiber, blocks all myosin binding sites
role of troponin I
prevents myosin from binding to actin in relaxed muscle
is the one stuck to the actin, like an anchor
role of troponin C
calcium ion binds here
role of troponin T
where the pulling happens
Troponin is a calcium-regulatory protein for the calcium regulation of contractile function in skeletal and cardiac muscles.
why are T tubules important
permit rapid transmission of an AP into a cell. also plays important role in regulating cellular calcium concentration
what is a triad
T-tubule plus 2 terminal cisternae
what is RYR1
gatekeeper of calcium in the muscle cell. its mechanically gated by FOUR Cav1.1 channels
RYR1 channels are located in the membrane surrounding a structure in muscle cells called the sarcoplasmic reticulum. This structure stores calcium ions when muscles are at rest.
what is Cav1.1
L type voltage gated Ca2+ channel. serves as a voltage center for E-C coupling in skeletal muscle fibers
voltage-gated calcium channel that plays a key role in skeletal muscle contraction
where does most of the Calcium that plays a role in contraction come from
sarcoplasmic reticulum
what happens to calcium once its released
after Ca2+ is released from SR, its IMMEDIATELY pumped back into SR by numerous Ca2+ ATPases (like SERCA)
when is ATP used
during quick movements
is atp only needed for contraction?
no needed for both contraction and relaxation- rigor mortis !!!
what is SERCA and why is it important
Sarcoplasmic Endoplasmic Reticulum Calcium ATPase
constantly pumps calcium back into SR lumen
what kind of paralysis does tetanus cause
spastic paralysis
what kind of paralysis does botox cause
flaccid (lol) paralysis
