Excitable Tissue Flashcards
Role of ion channels
Ion channels are ..?.. proteins spanning the ..?.. membrane
- These are ..?.. due to pore ..?.. and ..?.. of the ..?.. lining the channel
- ..?.. channels are always ..?.. and simply allow ions to move according to ..?..
- ..?.. channels are ..?.. or ..?.. by ..?.. or ..?.. signals
- Ions diffuse down ..?.. gradients, not ..?.. gradients
Transmembrane; plasma membrane; selective; size; changes; amino acids; leakage; open; concentration gradients; gated; opened; closed; chemical; electrical; electrochemically; concentration
Role of ion pumps and exchangers
- ..?.. protein like ion channel
- Move ion ..?.. or ..?.. concentration gradients
- ..?.. active transport: energy to do work comes directly from ..?.. E.g. ..?.. pumps, H pumps, Na-K pump
- Uses ..?.. active transport: energy stored in ..?.. gradients from ..?.. active transport pumps (i.e. ..?.. system)
o ..?.. pump indirectly drives the ..?.. active transport of other ..?..
o ..?.. is actively pumped ..?.. of the cell, then ..?.. back ..?.. cell with a ..?.. protein along ..?.. gradient thru ..?.. channels, and other substances are co-transported with the same ..?.. protein = ..?.. system (primary and secondary solutes are move in the ..?.. direction)
o ..?.. system (primary and secondary solutes moved in ..”.. directions) for example, ..?.. gradient to move ..?.. ions out of the cell to maintain ..?..
Transmembrane; against; up; primary; ATP; calcium; secondary; ionic; primary; coupled; Na-K; secondary; solutes; Na; out; leaks; into; carrier; ion; leakage; co-transported; carrier; SYMport; same; ANTIport; opposite; Na; H; pH
Indicate and explain the direction of Na+, K+, Cl- and Ca2+ movement across a cell membrane if the membrane were temporarily permeable to each ion
Na+, Cl- and Ca2+ would all move into the cell down their concentration gradients K+ would move out of the cell down its concentration gradient
Changes to the cell that influence permeability:
- ..?..-sensitive channels are affected by ..?.. or ..?.. in the membrane around it
- ..?..-sensitive channels are affected by the current ..?.. around the membrane
- ..?..-sensitive channels are affected by ..?.. agents binding to the ..?.. protein
- ..?.. to the cell membrane
Mechano; distortions; deformations; voltage; voltage; ligand; chemical; channel; damage
Define voltage gated ion channels and state how it’s activated
Voltage gated ion channels are a class of trans-membrane ion channels that are activated by changes in electrical membrane potential near the channel; these types of ion channels are especially critical in neurons, but are common in many types of cells.
Define ligand gated ion channels and state how it’s activated
Ligand gated ion channels are a group of trans-membrane ion channel proteins, which open to allow ions such as Na+, K+, Ca2+, or Cl- to pass through the membrane in response to the binding of a chemical messenger (i.e. a ligand), such as a neurotransmitter.
What is the average resting membrane potential of cells?
-70mV
How many gates (name them) do voltage gated Na+ channels have and what are their states?
*Gates- activation and inactivation gate
* states- closed at resting state (no Na+ enters cell); opened by depolarise on (Na+ enters the cell); inactivated (blocked by inactivation gates soon after they open)
How many gates (name them) do voltage gated K+ channels have and what are their states?
- gates- 1 gate
- states- closed a testing state (no K+ exits cell); opened by depolarisation after delay allowing K+ to exit cell
What does generating an AP depend on?
- Differences in K+ and Na+ concentrations inside and outside of the cell
- Differences in permeability of the plasma membrane to these ions
..?.. concentration is greater outside the cell
Na+
..?.. concentration is higher inside the cell
K+
What ion contributes most to RMP and explain its dominant effect over other ions?
Diffusion of K+ contributes the most to RMP, because the plasma membrane is relatively permeable to K+ but impermeable to anions. (i.e. At a normal state, the plasma membrane is most permeable to K+, less to Cl-, and a lot less to Na+). Therefore, K+ diffuses out of the cell but anions cannot follow, thereby creating negative membrane interior. (Leaky K+ channels)
Role of Na+-K+-ATPase pump in contributing toward RMP
K+ ..?.. so much that ..?.. membrane face electrically ..?.. the ..?.. charged K+ back ..?.. the cell. At ..?..mV, one ..?.. enters (due to electrical attraction), and one K+ exits (due to diffusion).
Even though the membrane is permeable to ..?.., it does not contribute to ..?.. because its ..?.. and ..?.. gradients exactly ..?.. each other.
..?.. is also attracted to the ..?.. membrane, and also ..?.. its concentration gradient, however the cell is much more permeable to ..?…
The rate of ..?.. transport is = rate of ..?.. diffusion ..?.. the cell. For each turn, the pump moves ..?.. Na+ out of the cell, while simultaneously moving ..?.. K+ into the cell so as to maintain the ..?.. gradients.
Diffuses; negative; attracts; positively; towards; -90; K+; Cl-; RMP; concentration; electrical; balance; Na+; negative; down; K+; active; Na+; into; 3; 2; electrochemical
What are the phases of muscle fibre contraction?
- Phase 1- motor neuron stimulates muscle fibre
- Phase 2- excitation- contraction coupling occurs
Phases leading to muscle fibre contraction
Phase 1- motor neuron stimulates muscle fibre
- ..?.. arrives at the ..?.. terminal at the ..?..
- ..?.. is released and binds to ..?.. on the ..?..
- the ..?.. permiability of the ..?.. changes
- ..?.. occurs
- local ..?.. (..?.. potential) ignites the ..?.. in the ..?..
Phase 2- excitation- contraction coupling occurs
- the ..?.. travels across the entire ..?..
- the AP travels along the ..?..
- the SR releases ..?.. which binds to ..?… The ..?.. binding sites (..?.. sites) on ..?.. is exposed
- ..?.. heads bind to ..?.. and ..?.. begins
Action potential (AP); axon; NMJ; ACh; receptors; sarcolemma; ion; sarcolemma; depolarisation; depolarisation; end plate; AP; sarcolemma; AP; sarcolemma; T tubules; Ca2+; troponin; myosin; active; actin; myosin; actin; contraction
At resting action potential:
- Voltage gated Na+ channel ‘..?..’ (..?..) gates are ..?..
- Voltage gated Na+ channel ‘..?..’ (..?..) gates are ..?..
- Voltage gated K+ channel ‘..?..’ gates are ..?..
- m; activation; closed
- h; inactivation; open
- n; closed
AP- depolarisation
- Depolarisation is initiated by a stimulus which makes the membrane potential more ..?..
- Voltage gated Na+ channel ‘..?..’ (..?..) gates then start to ..?..
- Na+ ions ..?.. across the membrane causing ..?..
- Depolarisation from the stimulus must reach the ..?.. potential for depolarisation to become ..?.., urged on by ..?.. feedback
- As more Na+ diffuses, membrane depolarises further, opening more Na+ ..?.. gates until all channels are ..?.. (this = sharp spike in action potential)
- Inside the cell is not ..?..
Positive; m; activation; open; diffuse; depolarisation; threshold; self-generating; positive; activation; open; positive
AP- repolarisation
- At maximum depolarisation, Na+ channel ‘..?..’ (..?..) gates begin to ..?.., limiting the ..?.. in action potential
- Voltage gated ..?..+ channel ‘..?..’ gates begin to ..?.., but more ..?..
- Diffusion of Na+ ion ..?..
- Voltage gated ..?..+ channel ‘..?..’ gates remain ..?..
- K+ continue to diffuse ..?.. of the cell
- The increased K+ ..?.. lasts slightly ..?.. than the time required to bring the ..?.. back to its ..?.. level, causing the membrane to be more ..?.. than ..?..
H; inactivation; close; spike; K+; n; open; slowly; decreases; K; n; open; out; permeability; longer; membrane potential; resting; negative; RMP
AP- hyperpolarisation
- After the ..?..+ channel ‘..?..’ gates ..?.. again, the ..?.. transport of Na+ and K+ by the ..?.. pump re-establishes the ..?..
- This is quickly ..?.. due to the thousands of Na-K ..?.. in the membrane.
K; n; close; active; Na+ -K+ ATPase; RMP; restored pumps
Action potential
- At resting state- no ..?.. move through the ..?.. channels
- ..?.. is caused by ..?.. flowing ..?.. the cell
- ..?.. is caused by ..?.. flowing ..?.. of the cell
- ..?.. is caused by ..?.. continuing to ..?.. the cell
- Ions; voltage-gated
- Depolarisation; Na+; into
- Repolarisation; K+; out
- Hyperpolarisation; K+; leave
What is the absolute refractory period and what causes it?
The period of time where it’s impossible for a cell to send more AP’s due to the gating mechanism of Na+ channels (the Na+ channel inactivation period)
What is affect on AP’s the stronger the stimulus gets?
The stronger the stimulus, more frequently APs are generated
If the membrane is more permeable to Na+:
- ..?.. or ..?.. will rush ..?.. the cell ..?..
- Cell will become more ..?..
- Reach ..?.. potential ..?..
- Action potential generated ..?..
- Na+; CA2+; into; quicker
- positive
- threshold; quicker
- quicker
If the membrane is more permeable to K+ or Cl-:
- ..?.. will rush ..?.. or ..?.. will rush ..?.. cell ..?..
- Cell will become more ..?..
- ..?.. from ..?.. potential
- Greater ..?.. needed to elicit ..?..
- Action potential ..?.. likely to occur
- K+; out; Cl-; into; quicker
- negative
- further; threshold
- depolarisation; AP
- less
How an excitatory transmembrane potential influence APs
- an EPSP is a local ..?.. of the ..?.. membrane that brings the neuron ..?.. to ..?..
- ..?.. binding opens ..?.. gated ion channels, allowing ..?.. and ..?.. to pass through ..?..
- depolarisation; postsynaptic; closer; AP potential
- Neurotransmitter; chemically; Na+; K+; simultaneously
How an inhibitory transmembrane potential influence APs
- an IPSP is a local ..?.. of the ..?.. membrane that drives the neuron ..?.. from the ..?..
- ..?.. binding opens ..?.. or ..?.. channels
- hyperpolarisation; postsynaptic; away; AP potential
- neurotransmitter; K+; Cl-
How increases or decreases in the ‘openness’ of Na+, K+, Ca2+ and Cl– channels affect action potentials
Ca+ entry causes synaptic vesicles to release ..?.. by ..?…
If K+ channels open K+ moves ..?.. of the cell. If Cl- channels open Cl- moves ..?.. cell.
- Either case, charge on ..?.. face of membrane becomes more ..?..
- As membrane potential ..?.. and is driven further from the axon’s ..?.. the ..?.. neuron becomes ..?.. likely to ..?.. and large ..?.. currents are required to induce an ..?..= ..?..
Neurotransmitter; exocytosis
Out; into
- inner; negative
- increases; threshold; postsynaptic; less; fire; depolarising; AP; IPSPs
Cell body/soma:
- ..?.. nucleus
- ..?.. ER of the cell body is also called ..?.. bodies (stains dark). These bodies also contain ..?.. that maintain cell ..?..
- Well-developed Golgi apparatus forms an ..?.. around ..?..
- Mostly located in the ..?..
- Function: produces all the ..?.. for the ..?.., ..?.. and ..?.. terminals and contains ..?..
- spherical
- rough; Nissl; neurofibrils; shape
- arc; nucleus
- CNS
- proteins; dendrites; axons; synaptic; organelles
Dendrites:
- Process of ..?.. that branches closely to the cell body
- Also contain ..?..
- Function:
o Main ..?.. region for the neuron
o Increased ..?..
o Convey ..?.. towards the ..?.. via ..?.. potentials
- cell body
- organelles
- receptive
- surface area
- signals; cell body; graded
Axon:
- ..?.. axon per neuron
- Arises from the ..?..-shaped part of the cell body (..?..)
- Slender, ..?.. process
- Long axons are called ..?..
- Axon branches occur at ..?.. and are called axon ..?..
- Knob-like distal endings of terminal branches are call ..?..
- Lacks ..?.. and ..?..
- Function: ..?.. region of the neuron
o Generates ..?.. and ..?.. them
o At the axon terminals, ..?.. are released into ..?.. space
- single
- cone; axon hillock
- uniform
- nerve fibres
- right angles; collaterals
- axon terminals
- ER; Golgi apparatus
- conducting
- action potentials; transmits
- neurotransmitters; extracellular
*Pre-synaptic membrane: Membrane of axon ..?.. releasing the ..?..
*Post-synaptic membrane: Membrane of receiving ..?.. with receptors ..?.. the ..?..
- terminal neurotransmitter
- dendrite; receiving; neurotransmitter
How neuronal conduction velocity is affected by axonal diameter and degree of myelin at ion
*The ..?.. the axon ..?.., the faster it conducts impulses due to the ..?.. resistance to the flow of local ..?.., bringing ..?.. areas of the ..?.. to ..?.. more ..?…
*The presence of ..?.. sheath dramatically ..?.. the ..?.. of action potential ..?… Myelin acts as an ..?.., preventing almost all ..?.. from ..?.. from the ..?.. and allows the membrane ..?.. to change more ..?… The local ..?.. current doesn’t ..?.. though the ..?.. membrane regions but is rather ..?.. and moves rapidly to the next ..?.. where another ..?.. is triggered.
*Action potentials are therefore only triggered at these ..?… All the voltage gated ..?.. channels are ..?.. in these gaps. This is called ..?.. and is ..?.. times faster than ..?.. conduction.
- larger; diameter; decreased; currents; adjacent; membrane; threshold; quickly
- myelin; increases; rate; propagation; insulator; ions; leaking; axon; voltage; rapidly; depolarising; dissipate; myelinated; maintained; myelin sheath gap; action potential
- gaps; Na+; concentrated; saltatory conduction; 30; continuous
- In bare plasma membranes, voltage ..?… Without voltage gated channels, as on a ..?.., voltage ..?.. because current ..?.. across the ..?..
- decays; dendrite; decays; leaks; membrane
- In non myelinated axons, conduction is ..?.. (..?.. conduction). Voltage gated ..?.. and ..?.. channels regenerate the ..?.. at each ..?.. along the ..?.., so voltage doesn’t ..?..
- Conduction is ..?.. because it takes time for ..?.. and for gates of ..?.. to move, and this must occur ..?.. voltage can be ..?..
- slow; continuous; Na+; K+; action potential; point; axon; decay
- slow; ions; channel proteins; before; regenerated
- In myelinated axons; conduction is ..?.. (..?.. conduction).
- ..?.. keeps the current in the ..?.. (voltage doesn’t ..?.. as much). Action potentials are generated only in the ..?.. and appear to ..?.. rapidly from ..?.. to ..?..
- fast; saltatory
- myelin; axons; decay; myelin sheath gaps; jump; gap; gap
What are myelin gaps also known as?
Nodes of Ranvier
Role of Nodes of Ranvier
- ..?.. rate of action potential ..?..
- Myelin is ..?.., thus ..?.. (..?..) won’t ..?.. across it
- Ion flow across the membrane occurs only at the ..?… As a result, the action potential signal jumps along the ..?.., from ..?.. to ..?.., rather than propagating ..?.., as they do in axons that lack a ..?..
- Increases; propagation
- fatty, ions; (hydrophilic); diffuse
- nodes of Ranvier; jumps; axon; node; node; smoothly; myelin sheath
Graded potential: are short-lived, ..?.. changes in membrane ..?.. that can either be ..?.. or ..?… These changes cause ..?.. that ..?.. in ..?.. with ..?… Their magnitude varies directly with ..?… The ..?.. the stimulus, the more the voltage ..?.. and the ..?.. the current ..?… Graded potentials are triggered by a ..?.. that ..?.. gated ions channels.
- localised; potential; depolarisations; hyperpolarisations; current flows; decrease; magnitude; distance; stimulus strength; stronger; changes; further; flows; stimulus; open
Generator potentials: a ..?.. potential occurs within a ..?.. that is part of a ..?.. neuron (i.e., dendrite) that generates ..?.. in the ..?.. ..?.. neuron
Receptor potentials: a ..?.. potential that occurs in a ..?.. receptor cell from the ..?.. neuron. The receptor potential changes the amount of ..?.. released by the ..?.. cell onto the ..?.. neuron.
Postsynaptic potentials: ..?.. potential produced from ..?.. binding to a ..?.. (can be ..?.. or ..?..)
- graded; receptor; sensory; action potentials; same; sensory
- graded; separate; sensory; neurotransmitter; receptor; sensory
- graded; neurotransmitter; synapse; inhibitory; excitatory
Mechanisms of neuronal transmission in electrical synapses
- Consist of ..?.. that contain ..?.. channels (..?..) that connect ..?.. of ..?.. neurons
- These connexons allow ..?.. and small ..?.. to flow ..?.. between ..?..
- ..?.. coupled
- Very ..?.. transmission across ..?.. (may be ..?..- or ..?..)
- Found in ..?.., and more common in ..?.. nervous tissue
- gap junctions; protein; connexons; cytoplasm; adjacent
- ions; molecules; directly; neurons
- electrically
- rapid; synapses; uni; bidirectional
- hippocampus; embryonic
Mechanisms of neuronal transmission in chemical synapses
- Allow ..?.. and ..?.. of ..?..
- Axon ..?.. of ..?.. neuron contains ..?..
- Receptor region on ../.. neuron membrane located on ..?.. or ..?..
- Separated by ..?.. that is filled with ..?..
- Prevent ..?.. from being ..?.. transmitted from one ..?.. to ..?..
- Ensures ..?.. communication between neurons
..?.. (PSD): ..?.. complex that supports ..?.. function at ..?.. synapses and includes ..?.. receptors, scaffolding ..?.. and regulatory ..?.. molecules
- release; reception; neurotransmitters
- terminal; presynaptic; synaptic vesicles
- postsynaptic; dendrite; cell body
- synaptic cleft; fluid
- impulse; directly; neuron; another
- unidirectional
- postsynaptic density; macromolecular; chemical; neurotransmitters; proteins; signalling
Mechanisms of neuronal transmission in mixed synapses
- Interactions of ..?.. and ..?.. signalling occur ../..
- During ..?.. and within the ..?.. brain
- ..?.. communication between ..?.. is ..?.. regulated: it is initially ..?.. but declines at later ..?.. stages
- The initial increase in ..?.. enables ..?.. neurons to form ..?.. that exhibit ..?.. patterns of ..?.. activity
- ..?.. provide a ..?.. for the formation of ..?… These networks then trigger the ..?.. of ..?.. in most
neuronal cell types. - By regulating nearby gap junctions, ..?.. at ..?.. synapses provide a mechanism for fine-tuning ..?.. coupling within networks of ..?.. neurons
- Such interactions result in ..?.. of hardwired networks within the brain
- electrical; chemical; postsynaptically
- development; adult
- gap junction; neurons; developmentally; prominent; developmental
- coupling; developing; functional domains; coordinated; spontaneous
- gap junctions; blueprint; chemical neuronal networks; elimination; coupling
- PSDs; glutamatergic; electrical; electrically coupled
- dynamic reconfiguration
Briefly describe exocytosis with reference to chemical synapses
Action potential arrives at presynaptic axon terminal
- ..?..+ and ..?..+ voltage gated channels ..?..
- Very fast influx of ..?..+ acts as ..?.. messenger causing ..?.. to fuse with ..?..
- Release ..?.. into ..?.. by ..?..
- Ca2+ is quickly ..?..
o Taken up by ..?..
o Ejected by active ..?..
- The higher the ..?.. of the impulse (i.e. ..?.. impulse), the ..?.. vesicles fuse
- Electrical signal is stopped when Ca2+ is ..?.. by the ..?.. or ..?.. by ..?.. pumps
Action potential arrives at presynaptic axon terminal
- Na; CA2; open
- CA2; intracellular; synaptic vesicles; axon membrane
- neurotransmitters; synaptic cleft; exocytosis
- removed
- mitochondria
- Ca2+ pump
- frequency; stronger; more
- reabsorbed; ER; ejected; active
Briefly describe exocytosis with reference to chemical synapses
Neurotransmitters diffuse across the synaptic cleft and bind to specific receptors on the postsynaptic membrane
- ..?.. gated ion channels are ..?.. and creates ..?.. potential
- ..?.. neuron is either ..?.. or ..?..
- chemically; opened; graded
- postsynaptic; excited; inhibited
Briefly describe exocytosis with reference to chemical synapses
Neurotransmitter effects are terminated
- Binding of ..?.. to ..?.. is ..?..
- When ..?.., continues to affect membrane ..?.. and ..?.. reception of additional ..?.. from ..?.. neurons
- ..?.. of neurotransmitter by ..?.. terminal or ..?.. (eg, ..?..)
- ..?.. by enzymes associated with the ..?.. membrane or ..?.. within the ..?.. (eg, ..?..)
- Diffusion away from the ..?..
- neurotransmitter; receptor; reversible
- bound; permeability; block; signals; presynaptic
- reuptake; presynaptic; astrocytes; noepinephrine
- degradation; postsynaptic; enzymes; synaptic cleft; acetylcholine
- synapse
Example of synaptic transmission (ACh)
- synthesis of ACh- ..?.. neurone
- stored in ..?.. within the ..?..
- ..?.. of ..?.. following ..?.. of ..?.. terminal initiates ..?.. of vesicles with the ..?..
- ACh is released into the ..?.. by ..?..
- ACh diffuses across the ..?.. and binds to ..?.. receptors on the ..?..
- Ach is broken down by ..?.. = ..?.. and ..?..
- ..?.. is taken up by the ..?.. for further production of ACh
- presynaptic
- vesicles; presynaptic neurone
- influx; Ca2+; depolarisation; presynaptic; fusion; presynaptic membrane
- synaptic cleft; exocytosis
- synaptic cleft; nicotinic ACh; postsynaptic membrane
- acetylcholinesterase; choline; acetate
- choline; presynaptic neurone
Excitatory Postsynaptic potentials (EPSPs) – makes cells need less ..?..+ to generate an action potential
- Occurs at ..?.. synapses
- Binding of ..?.. ..?.. the ..?.. membrane
- ..?.. gated ion channels ..?.. (on ..?.. and ..?..)
- ..?..+ and ..?..+ diffuse ..?.. in ..?.. directions
-Electrochemical gradient for Na+ is much ..?.., thus ..?.. of Na+ ..?.. ..?.. of K+
-Therefore, net ..?.. occurs - However, a true action potential is ..?.. generated
- ..?.. reversal does ..?.. occur due to the ..?.. movement of ..?..+ and ..?..+
-This prevents excess ..?.. charge ..?.. ..?.. the cell
-Local ..?.. depolarisation events occur at ..?.. ../.. membranes
-This lasts a few ..?.. and then returns to ..?..
- ..?.. reversal does ..?.. occur due to the ..?.. movement of ..?..+ and ..?..+
- Function is to help ..?.. action potential ..?.. at the ..?..
- Currents in the ..?.. created by the ..?.. decline with ..?.. but may still be ..?.. enough to ..?.. the ..?.. to ..?..
- Voltage gated channels then ..?.. and an action potential is ..?..
- excitatory
- neurotransmitters; depolarises; postsynaptic
- chemically; open; dendrites; cell bodies
- Na; K; simultaneously; opposite
- steeper; influx; greater; efflux
- depolarisation
- never
- polarity; not; simultaneous; Na; K
- positive; accumulating; inside
- graded; excitatory; postsynaptic
- milliseconds; RMP
- trigger; distally; axon hillock
- cytoplasm; EPSPs; distance; strong; depolarise; axon; threshold
- open; generated
Inhibitory Postsynaptic Potentials (IPSPs)
- Occurs at ..?.. synapses
- Binding of neurotransmitters ..?.. a ..?.. neuron’s ability to generate an ..?..
- Membrane is ..?.. by making membrane more ..?.. to ..?..+ or ..?..-
o If K+ channels are opened, K+ moves ..?.. of cell
o If Cl- channels are opened, Cl- moves ..?.. the cell
o The cell becomes more ..?.., further from the ..?.. and ..?.. likely to fire
- ..?..+ ..?.. is not affected
- Larger ..?.. currents are required to induce ..?..
- E.g. ..?.. and ..?..
- inhibitory
- reduces; postsynaptic; action potential
- hyperpolarised; permeable; K; Cl
- out
- into
- negative; threshold potential; less
- Na; permeability
- depolarising; AP
- GABA; glycerine
Ionotropic receptors
- structure: ..?.. ion channels
- response: ..?.., ..?.. synaptic transmission
- location: directly ..?.. ..?.. release
- mechanism: ..?.. binds and causes ..?.. change. Opens ..?.. channels and allows ..?.. to pass. The ..?.. of the target cell changes
- examples
- excitatory receptor sites: ..?.., aspartate, ..?… Allows ..?.., K+ and ..?.. to enter. Na+ contributes the most to ..?..
- inhibitory receptors sites: ..?.., glycerine. Allows ..?.. to enter. Fast ..?..
- ligand
- fast; direct
- opposite; neurotransmitter
- ligand; conformation; central; ions; membrane potential
- glutamate; ATP; Na+; Ca2+; depolarisation
- GABA; Cl-; hyperpolarisation
Metabotropic receptors
- structure: ..?..- membrane, ..?..- protein ..?..
- response: ..?.., ..?.. synaptic responses
- Location: ..?.. of cells
- mechanism: ..?.. binds to ..?.. linked receptor. .?.. is activated, controlling production of ..?..- regulate ..?.. channels, activate ..?.. enzymes, interact with ..?.. proteins to influence ..?.. transcription
- examples: secondary messengers- ..?.., cGMP, ..?.., Ca2+. Bring about widespread ..?.. changes
- trans; G; complexes
- slow; direct
- surface
- neurotransmitter; G-protein; G-protein; secondary messengers; ion; kinase; nuclear; RNA
- cAMP; diacylglycerol; metabolic
An auto-receptor: present at ..?.. ending, a receptor that regulates, via ..?.. or ..?.. feedback processes, the ..?.. and/or ..?.. of its own physiological ..?…
Nerve; negative; positive; synthesis; release; ligand
Secondary messengers: one of the ..?.. components of intracellular ..?… (Signal ..?..)
Signal transduction cascades; amplification
What are the main components of cAMP?
Neurotransmitter binds to receptor. This activates G-protein. GTP > GDP. G protein activates Adenylate cyclase, ATP> cAMP
What are the effects of cAMP?
o Changes membrane permeability by opening or closing ion channels
o Activates protein kinase enzymes, which phosphorylate other enzymes
o Activates specific genes through nuclear proteins
What hormones achieve their affects through cAMP?
- adrenaline
- glucagon
- leutinising hormone
What substance is responsible for degrading cAMP?
Phosphodiesterase
PIP2-Calcium mechanism
- ..?.. is the G-protein that splits the membrane lipid, ..?.. (PIP2) into two secondary messengers: ..?.. (DAG) and ..?.. (IP3)
§ DAG activates protein ..?.. enzymes
§ IP3 releases ..?..+ from ..?.. storage sites (ER)
§ Ca2+ also serves as a ..?..
• Alters ..?.. of specific ..?.. and ..?..
• ..?.. to and activates ..?.. protein to ..?.. the ..?.. response
- phospholipase C; phosphatidyl inositol biphosphate; diacyglycerol; inositol triphosphate
- kinase
- Ca2+; intracellular
- secondary messenger
- activity; enzymes; channels
- binds; calmodulin; amplify; cellular
GABA is the principle ..?.. neurotransmitter in the brain that uses both ..?.. and ..?.. messengers to illicit and effect (see IPSP)
Inhibitory; direct; secondary messengers
..?.. is the main excitatory neurotransmitter in the brain and is important in ..?.. and ..?.. (see EPSP)
Glutamate; learning; memory
What are the main neurotransmitters in the PNS?
- ACh
- NA
What are the main neurotransmitters in the CNS?
- serotonin
- dopamine
- noepinephrine
- histamine
- glycine
- ACh
The differences between pre-synaptic and post-synaptic effects of neurotransmission and neuromodulation
*Neuromodulator: ..?.. messenger released by a ..?.. that does not ..?.. cause ..?.. or ..?.. but instead affects the ..?.. of ..?.., can act ..?.. the synapse as well
*Can act pre-synaptically to influence ..?.., ..?.., ..?.., or ..?.. of ..?..
*Can act post-synaptically to alter ..?.. of the ..?.. membrane to the ..?..
- chemical; neuron; directly; EPSPs; IPSPs; strength; synaptic transmission; outside
- synthesis; release; degradation; reuptake; neurotransmitter
- sensitivity; postsynaptic; neurotransmitter
List 5 neuromodulators found in the CNS and PNS
- NO gas
- adenosine
- dopamine
- serotonin
- acetylcholine
- histamine
- norepinephrine
Temporal summation: when one or more ..?.. transmit impulses in ..?.. order and bursts of ..?.. are released in ..?… The first impulse produces a small ..?.. and before it dissipates, ..?.. impulses trigger more ..?… These ..?.., causing the ..?.. to ..?.. much ..?.. than it would from a ..?.. ESPS. ..?.. impulses from ..?.. neuron.
Presynaptic neurons; rapid-fire; neurotransmitter; quick succession; ESPS; successive; ESPSs; summate; postsynaptic membrane; depolarise; more; single; electrical; one
Spatial summation: occurs when the ..?.. is stimulated ..?.. by a large number of ..?.. from ..?.. or many ..?.. neurons. Huge numbers of its receptors bind ..?.. and ..?.. initiate ..?.., which ..?.. and dramatically enhance ..?… Electrical impulses coming from ..?.. axons
Both temporal and spatial summation can also occur with ..?…
Postsynaptic neuron; simultaneously; terminals; one; presynaptic; neurotransmitter; simultaneously; ESPSs; summary; depolarisation; multiple
IPSPs
Graded potential
- location of event: ..?..
- distance travelled: ..?.. distance- typically within ..?.. to ..?..
- amplitude: ..?.. sizes (..?..); ..?.. with distance
- stimulus for opening channels: ..?.. (neurotransmitter) or ..?.. stimulus (e.g., light, ..?.., temperature)
- is there a positive feedback cycle?- ..?..
- repolarisation: ..?.. independent. When does it occur?
- summation: stimulus responses can ..?.. to ..?.. ..?.. of graded potential.
- cell body and dendrites
- short; cell body; axon hillock
- various; graded; decays
- chemical; sensory; pressure
- no
- voltage; when stimulus is no longer present
- summate; increase; amplitude
Action potential
- Location: ..?.. and ..?..
- Function: ..?.. distance signalling. Constitutes the ..?..
- Distance travelled: ..?.. distance- from ..?.. at the axon ..?.. through the entire length of the ..?..
- Amplitude: ..?… (..?.. or ..?..); does not ..?.. with distance
- stimulus for opening channels: ..?.. (depolarisation is triggered by ..?.. reaching ..?..)
- Is there a postive feedback cycle?
- Repolarisation: ..?.. regulated. Occurs when ..?.. channels ..?.. and K+ channels ..?..
- Does summation occur? why?
- Initial effect of stimulus: opens ..?.. gated channels. First opens ..?.. channels and then ..?.. channels
- Peak membrane potential: ..?.. to ..?..mv
- axon hillock; axon
- long; nerve impulse
- long; trigger zone; hillock; axon
- always the same; all; none; decay
- voltage; graded potential; threshold
- yes
- voltage; Na+; inactivate; open
- no- it’s an all-or-none response
- voltage; Na+; K+
- +30; +50
What are the types of graded potentials?
- excitatory postsynaptic potential (EPSP)
- inhibitory postsynaptic potential (IPSP)
EPSP
- Function: ..?.. distance signalling. ..?.. that spreads to the ..?… It moves the membrane potential ..?.. threshold for generating an ..?..
- Intial effect of stimulus: opens ..?.. gated channels that allow simultaneous ..?.. and ..?.. fluxes
- Peak membrane potential: ..?..- moves towards ..?..mv
- short; depolarisation; axon hillock; towards; AP
- chemically; Na+; K+
- depolarises; 0
IPSP
- Function: ..?.. distance signalling. ..?.. that spreads to the ..?.. and moves the membrane potential ..?.. from threshold for generating an ..?..
- Initial effect of stimulus: opens ..?.. gated ..?.. or ..?.. channels
- Peak membrane potential: ..?..- moves towards ..?.. mv
- short; hyperpolarisation; axon hillock; away; AP
- chemically; K+; Cl-
- hyperpolarises; -90
What is the role of the t-tubule system in striated muscle?
AP’s in the t-tubule has a voltage gated receptor that is mechanically linked to the RYR receptor in the SR, so when stimulated, both open and Ca2+ is released from the SR
Steps in excitation-contraction coupling
- The AP propagates along the ..?.. and down the ..?..
- ..?.. ions are released. Transmission of the AP along the ..?.. of the ..?.. causes the ..?..-sensitive tubule ..?.. to change ..?… This ..?.. change opens the ..?.. release channels in the ..?.. of the ..?.., allowing ..?.. to flow ..?.. the ..?..
- ..?.. binds to ..?.. and removes the ..?.. action of ..?… When ..?.. binds, ..?.. changes ..?.., exposing ..?.. sites for ..?.. (..?.. sites) on the ..?.. filaments
- ..?.. begins. ..?.. binding to ..?.. forms ..?.. and ..?.. begins. At this point, ..?.. is over.
- sarcolemma; t-tubules
- calcium; t-tubules; triad; voltage; proteins; shape; shape; Ca2+; terminal cisterns; SR; Ca2+; into; cytosol
- Calcium; troponin; blocking; tropomyosin; Ca2+; troponin; shape; binding; myosin; active; thin
- Contraction; myosin; actin; cross bridges; contraction, cross bridge; E-C coupling
What is the role of the SR and Ca2+ release from the SR in muscle contraction?
Ca2+ binds to troponin to induce conformational change to drag tropomyosin off the active sites of the actin helix.
Each thick molecule consists of many ..?.. molecules whose ..?.. protrude at ..?.. ends of the ..?…
myosin; heads; opposite; filament
A thin filament consists of ..?.. strands of ..?.. subunits twisted into a ..?.., plus ..?.. types of ..?.. proteins (..?.. and ..?..)
2; actin; helix; 2; regulatory; troponin; tropomyosin
What proteins does the troponin complex consist of?
- TnT: binds to tropomyosin to position it on the actin
- TnI: inhibitory subunit that binds to actin
- TnC: binds to Ca2+ ions
What is myosin-ATPase?
The enzyme hydrolying ATP into ADP and Pi.
Myosin-ATPase is important for:
- energising the ..?.. (flexing of the ..?.. pulling the ..?.. filament towards the ..?.. of the ..?..)
- disconnecting the myosin ..?.. from the binding site on ..?.. hydrolyses ..?.., providing energy for ..?.. to return to its ..?.. energy conformation
- energising the ..?..
- power stroke; cross bridge; actin; centre; sarcomere
- cross bridge; actin; ATP; myosin; high
- Ca2+ pump
The role of the SR Ca2+ ATPase pump once E-C coupling is over
- when the muscle ..?.. ceases, the ..?..- sensitive tubule ..?.. return to their original ..?.., closing the ..?.. release channels of the ..?..
- ..?.. levels in the ..?.. fall as Ca2+ is continually pumped back into the ..?.. by ..?..
- without ..?.., the ..?.. action of ..?.. is restored, ..?.. interaction is ..?.., and ..?.. occurs.
- AP; voltage; proteins; shape; Ca2+; SR
- Ca2+; sarcoplasm; SR; active transport
- Ca2+; blocking; tropomyosin; myosin-actin; inhibited; relaxtion
What are the components of a motor unit?
1 motor neuron and the muscle fibres it innervates
When a nerve impulse reaches a NMJ
- An AP arrives at the ..?.. of a motor neuron
- voltage-gated ..?.. channels ..?… Ca2+ enters the ..?.. moving ..?.. its ..?… gradient
- Ca2+ entry causes ..?.. to be released by ..?..
- ..?.. diffuses across the ..?.. and binds to its ..?.. on the ..?..
- ..?.. binds opens ion channels in the receptor that allow ..?.. passage of ..?.. into the ..?.. and ..?.. out of the muscle fibre. More ..?.. ions enter than ..?.. ions exit, which produces a local change in ..?.. call the ..?.. potential
- ..?.. effects are terminated by its breakdown in the ..?.. by ..?.. and diffusion away from the ..?..
- axon terminal
- Ca2+; open; axon terminal; down; electrochemical
- ACh; exocytosis
- ACh; synaptic cleft; receptors; sarcolemma
- ACh; simultaneous; Na+; muscle fibre; K+; Na+; K+; membrane potential; end plate
- ACh; synaptic cleft; acetylcholinesterase
Briefly describe the differences between cardiac and skeletal muscle contraction with reference to:
- The role of Ca2+-induced SR Ca2+ release
o Extracellular ..?.. binds to ..?.. receptors on the ..?.. which opens ion channels for massive ..?.. of ..?.. into the ..?.. – known as the “..?..”
o This makes action potential and ..?.. phases lasts much ..?..
- CA2+; RYR; SR; influx; CA2+; sarcoplasm; Ca2+ spark
- contractile; longer
Briefly describe the differences between cardiac and skeletal muscle contraction with reference to:
The role of second messengers
o The second messenger is ..?.. which activates ..?..
o The release of cAMP is stimulated or inhibited by ..?.. or ..?.. ..?..
o These G proteins are in turn are stimulated by ..?.. (sympathetic stimulation – ..?..) and ..?.. (parasympathetic stimulation – at …?..) respectively
- cAMP; protein kinase A
- excitatory; inhibitory; G proteins
- catecholamines; flight/fight; acetylcholine; rest
Briefly describe the differences between cardiac and skeletal muscle contraction with reference to:
Energy requirements
o Cardiac m contains many more ..?.. due to its heavy dependence on ..?..
- ..?.. have ..?.. so cardiac cells all contract ..?..
due to propagation of action potential, and ..?.., to keep cells ..?..
- Uses ..?.. theory to contact, but myofibrils vary greatly in ..?.. and branch extensively to make way for the ..?..
- T-tubules are ..?.. and ..?.. than in ..”.. muscle, only ..?.. per sarcomere
- SR is ..?.., no ..?.., therefore no ..?..
- ..?.. provides action potential in the ..?.., travels down ..?.., to ..?.. fibres
o These cells have ..?.. resting action potentials, and continuously ..?.., drifting slowing towards ..?..
- However, 1% of cardiac cells are ..?.. and can trigger own ..?..
- mitochondria; aerobic respiration
- intercalated discs; gap junctions; simultaneously; desmosomes; adhered
- sliding filament; diameter; mitochondria
- wider; fewer; skeletal; 1
- simpler; terminal cisterns; triads
- SA node; heart; AV bundles; purkinje fibres
- unstable; depolarise; threshold potential
- self excitable; depolarisation
Briefly describe the differences between smooth and skeletal muscle with respect to the
- Organisation of myofilaments
o Cells contain ..?.. to transmit action potential to ..?..
o No ..?.. or ..?..
o Different type of ..?.. that is ..?.. than ..?.. filaments and has actin-binding heads all along its length
o ..?.. ratio of myosin: actin (1:13)
o No ..?.. complex within actin
- gap junctions; adjacent cells
- striations; sarcomeres
- myosin; shorter; actin
- decreased
- Troponin
Briefly describe the differences between smooth and skeletal muscle with respect to the
Dependence on excitation-contraction coupling
o Innervated by ..?.. with ..?.. (..?..)
o These bulbs release ..?.. into wide ..?..(diffuse
junction) for ..?.. contraction
o No ..?.., but have ..?.. (pouch-like folds in ..?..)
o Most Ca2+ enters directly from ..?.. (SR releases some Ca2+)
o The Ca2+ binds to the ..?.., which phosphorylates ..?..
o Myosin kinase phosphorylates ..?.., activating it
o Contraction ends when Ca2+ ..?.. from ..?.., active transport of Ca2+ into the ..?.. and ..?.., and ..?.. of myosin
- autonomic nerves; bulbs; varicosities
- neurotransmitter; synaptic cleft; simultaneous
- T tubules; caveolae; sarcolemma
- ECF
- calmodulin; myosin kinase
- myosin
- detaches; calmodulin; SR; ECF; dephosphorylation
Briefly describe the differences between smooth and skeletal muscle with respect to the
Effect of Ca2+-induced SR Ca2+ release (for vascular smooth muscle)
o Vascular smooth muscle maintains a ..?.. degree of ..?..
o Called ..?..
- moderate; contraction
- smooth muscle tone
