neurotransmission Flashcards
- ways to classify neurons
1- —- as bipolar or multipolar aka the number of — from cell body
2- Neurons that transmit information towards the CNS are —– and Neurons that transmit information from the CNS are —-
3- type of — they release
4- —- send information to the central nervous system about the internal and external environment
5- —– control the activity of the body by controlling muscle and gland functions (contraction, relaxation, secretion).
- morphology ( shape)
- projections
- afferent ( arriving )
- efferent ( existing , effector organ ) aka afferent and efferent are classified by their direction
- neurotranskitter ( substacne or chemicals they release as dopamine, acetylcholine)
- sensory nerves
- motor nerves
( sensory and motor and the functional ways of classifying )
signal conduction :
—- receive in-put signals, leading to a
—– propagate out-put signals and are for action potential
- dendrites or cell body ( soma)
leads to:
1-depolarisation or
2-hyperpolarisation of the plasma membrane - axons
( check slide 7 for structure pls)
1-is the junction between one neuron & the next cell —
2-Specialised structure at which —– impulse is converted to a —- signal for communication between cells (electro-chemical coupling)
types of communication includes:
3-Synapses between nerve and muscle cells are also called —-
- synapse
- electrical to chemical
- communication include:
Nerve-Nerve
Nerve-Organ / Organ-Nerve
Nerve-Muscle
Nerve-Gland - neuromuscular junctions or motor end plates
-Typically small, rapid-acting molecules
-e.g. Acetylcholine, Dopamin, glutamate, noradrenaline, GABA
-Generally, neurons release —- type of —
- neurptranmsitter
- one type of NT
—–releases a chemical, a neurotransmitter
The neurotransmitter diffuses across —-
The neurotransmitter binds to specific receptor proteins on the plasma membrane of the —- to alter its membrane potential
- presynaptic neuron
- synaptic cleft
- postsynaptic cell
- synpses can be —-
- The neurotransmitter at excitatory synapses —- the postsynaptic membrane.
example: —
by which the binding of — to its receptor on postysunaptic cell; open up —-
which allows — of na
+ ions — membrane potential - If depolarisation of the postsynaptic membrane reaches a —- , an action potential is generated in the postsynaptic cell.
- excitatory or inhibitory
- depolarise
- acteylcholine (ACh)
-ACh - ligand gated sodium channel
- influx
- reduces
- threshold
-Two basic forms of electrical signals:
1- —- local changes in membrane potential not reaching threshold and these die out over – distances , they can be generated by —- which serves as — signals
- graded and action potential
- graded potential
- short
- action potenial
- long distance signal
graded potential occur in — , — region of excitable membrane
- Magnitude of graded potential varies directly with the magnitude of the —-
- small
- specialised
- triggering event
If depolarisation at a certain spot on the neuron reaches a threshold voltage of approx. —-
the — voltage opens up several —- in portion of plasma membrane
- -50mV
- reduced voltage
- voltage gated na+ channels
-Brief, —— (≅100mV) changes in membrane potential during which potential actually —-
- Involves only a —-portion of the total excitable cell membrane at a certain time
- Do not decrease in —- as they travel from their site of initiation throughout remainder of cell membrane
- rapid and large
- reverses
- small portion
- strength
( so basically the size is the same but diff frequency )
During an AP voltage-gated Na+ channels open in the PM that allows Na+ movement into the cell this causes —-
PM depolarises
if the threshold is not reached there’s no —-
action potential
Voltage-gated K+ channels subsequently open which allows K+ to leave the cell down its electrochemical gradient bringing the MP back toward —-
resting ( -70mV)
( pls check the graphs especially 27 )
When membrane reaches threshold potential:
1-Voltage-gated Na+-channels in the membrane undergo —-
2- Flow of sodium ions into the ICF —- the membrane potential from — mV to —-mV
3- Flow of potassium ions into the ECF restores the membrane potential to the —-
- conformational changes
- reverses
- -70
- +30
- resting state
—– period is the period when a further stimulus applied to the neuron (or muscle fiber) will not trigger another action potential.
-In some neurons, the refractory period lasts only —— seconds. In other words, some neurons can transmit up to —– impulses per second
- Due to —– of sodium channels (absolute refractory period) and —– brought about by opening of potassium channels and potassium ions (K+) movement out of cell (relative refractory period).
- refractory period
- inactivation
- reploarisation
- 0.001-0.002
- ## 500-1000
- action potential is an —
- The — of the action potential is an intrinsic property of the cell.
-So long as they can reach the —- of the cell, strong stimuli produce no stronger action potentials than weak one - , the strength of the stimulus is encoded in the —- of the action potentials that it generates.
- all-or-none
- threshold
- frequency
The neurotransmitter at inhibitory synapses —- the postsynaptic membrane as:
1- binding of – to its receptor on the postsynaptic neuron opens up —–
2-The entry of negatively charged chloride ions —-the membrane potential (e.g. from — to — ), meaning even more negative charge —- the cell
-This increased membrane potential (or more negative charges inside the cell) counteracts any excitatory signals that may arrive at that neuron.
- hyperpolarises
- GABA ( : gamma aminobutyric acid )
- up ligand-gated chloride (Cl−) channel.
- increases
- -70 to -90
- inside
-axons of most neurones are encased in a fatty sheath called the —-
-Myelin functions as an —-which — current flow
-It is the expanded plasma membrane of a neighboring cell called the —–
- Where the sheath of one Schwann cell meets the next, the axon is —-
-The voltage-gated sodium channels of myelinated neurones are confined to these spots —-
- The influx of —- ions at one node creates enough —–o reach the threshold of the next. Thereby the action potential jumps from one node to the next. This results in a faster propagation of action potentials.
- myelin sheath
- electrical insulator
- restrict flow
- Schwann cell or oligiodendtryte
- unprotected
- nodes of ranvier
- sodium
- depolarisation
-straited muscle as:
- unstraited as:
- skeletal and cardiac
-smooth
info:
-the cytoplasm: mostly actin and myosin filaments - nuclei and organelles are pushed to the edge
- the endoplasmic (sarcoplasmic) reticulum is arranged as a system of tubes around groups of myofibrils. Tubes of the sarcoplasmic reticulum drain into large tubes called T-tubes.
The “output” of PNS consists of motor neurones running from the CNS to the muscles and glands called —-
1- — :skeletal muscle
neuromuscular junction (NMJ)
2- —-:cardiac or smooth muscle
- effector
- nerve somatic motor nerve
- nerve autonomic NS
motor neurons in innervate skeletal muscle fibres:
-Cell bodies of motor neurons located in —
- Thick, myelinated axons —
- Several fine branches with many varicosities (swellings), called —-
- —-
- Boutons lie over —- folds on muscle
- Each muscle cell is innervated by —motor neuron; each motor neuron can innervate —–
- ventral horn
- somatic efferent fiber
- synaptic bouton
- synaptic cleft
- postsynaptic junctional folds
- one
- many muscle fibres
-Motor neurons and skeletal muscle fibres are chemically linked at the —-
-Action potentials traveling down (large, myelinated) motor neurons of the sensory-somatic efferent branch of the nervous system cause the —– at which they terminate :
- Neuromuscular Junction (NMJ)
-contraction of skeletal muscle fibers and they terminate :
-always excitatory
-create miniature end plate potentials (mEPP) from single vesicle release
The junction between the terminal of a motor neuron and a muscle fiber is called the —- which is a specific type of —
neuromuscular junction (“motor end plate”). It is a specific type of synapse.
-Axon terminal of motor neuron forms — with a single —-
- signals are passed between nerve terminal and muscle fiber by mean of —-
- Released ACh binds to receptor sites on —- cell membrane
- Binding triggers opening of —- in motor end plate
- —— movements depolarize motor end plate, producing —–
-Local current flow between depolarized end plate and adjacent muscle cell membrane brings adjacent areas to —-
- —– is initiated and propagated throughout muscle fiber
- neuromuscular junction
- muscle cell
- NT ACh
- motor end plate of muscle cell membrane
- specific channels
- ion movement
- end plate potential ( EPP or end plate spike)
- threshold
- action potential
-Chemical messenger (neurotransmitter) carries —- from —- to—-
- —- was one of the first neurotransmitters discovered , its produced in — of the motor neuron by the enzyme —- which uses —- and —- as substrate , in the CNS its released within —
- signals
- nerve
- muscle
- acetylcholine
- pre synaptic terminal
- choline acteyltransferase
- acetyl coenzyme A
- choline
- cholinergic system (excitatory)
The terminals of motor axons contain thousands of — filled w —-
vesicles
neurotransmitter acetylcholine ACh
When an action potential reaches the —–, hundreds of these vesicles release their —- onto a specialized area of the —– membrane on the muscle fiber. This area contains a cluster of ligand-gated ion channels that are opened by ACh and let —- diffuse in.
- axon terminal
- ACh
- postsynaptic membrane
- sodium ions na+
( check graph )
-muscle fiber has resting membrane potential of —
- influx of sodium ions — the potential and creates a — by —- and the magnitude depends on the — of ACh
- -80mV
- reduces
- end plate potential
- depolarisation
- amount/duration
the depolarising effect of EPP open —- channels eliciting an — in the fiber
the action potential sweeps down the length of the fiber and leads to —
- muscle contraction following ca+2 release in —
- voltage gated na+ channels
-action potential - contraction of the muscle
- excitation-contraction coupling
-Receptor for ACh at postsynaptic membrane of skeletal NMJ is the
—
- the drug – also activated this receptor
- nicotine receptors are — and the — is intrinsic part of the receptor
- nicotine ACh receptor mediate very – responses
- muscle type nicotine receptor ( Nm or N1)
- nicotine
-ionotropic - ion channel
- rapid
nicotine receptors are found at the — of —
and they can also be found in —- and —
- neuromuscular junction of skeletal muscle
- autonomic nervous system ( ganglion )
- central nervous system
—– concentrated on the external surface of the postsynaptic membrane and in the synaptic cleft.
- breaks down the — in the neuromuscular junction ( 25,000 molecules per sec )
- sodium channels – and the field is – for the arrival of another nerve impulse
- ACETYLCHOLINESTERASE ( AChE)
- neurotransmitter ACh
- closes
- cleared
Nicotinic cholinergic receptors at the NMJ can be blocked by several drugs which can induce —–
- paralysis and/or cessation of breathing ( respiratory muscles are skeletal muscles too )
—- contains substances that inhibit binding of ACh to nAChR causes —-
—-used as neuromuscular blocking agents during surgical anaesthesia to relax skeletal muscle
- curare
- curare payalyses skeltal muscle
- D-tubocurarine ( an Acetylcholinesterase inhibitors)
—- blocks release of ACh - prevents muscles responding to nerve impulses , works by cleaving —- required for vesicle release
- Ingesting 0.0001 mg can —-
- caused by —-
treats — , disorders including :
- cosmetic use as:
- — contracts muscles
-botulinium toxin ( botox)
- synaptic proteins
-kill an adult
- improper canned food
- Treats dystonias – disorders including spasms, involuntary twitches
- reduces wrinkles and frown lines
- permanently
—– , disease in which immune system attacks motor end-plate ACh receptor. Commonest primary disorder of neuromuscular transmission.
-Mainly in adulthood: 20 / 100,000
-too little — effect extreme —-
- traded w :
- myasthenia graves
- ACh
- extreme muscle contraction weakness
- Treated with AChE inhibitor (neostigmine) – prolongs effect of ACh, or immunosuppressants
choose the correct ans:
How would neuromuscular transmission be affected in the presence of an acetylcholinesterase (AChE) inhibitor?
1. Muscle contraction would be delayed.
- Muscle contraction would be prolonged.
2222( check last slide plssss)
