action potentials Flashcards
t1 w9-12
what is the term that describes the resting membrane potential of a neuron: repolarised polarised hyperpolarised depolarised
polarised
at rest, what is the normal movement of potassium ions in / out of the cell: a) move in along its chemical gradient and move out due to the electrical gradient b) move in along its chemical gradient and move in due to the electrical gradient c) move out along its chemical gradient and move out due to the electrical gradient d) move out along its chemical gradient and move in due to the electrical gradient
d) move out along its chemical gradient and move in due to the electrical gradient
the cell membrane is most permeable to what charged molecule at rest? a) sodium B) potassium c) protein Anions d) calcium
B) potassium
at RMP what is the charge? a) -90mV b) +30mV c) -55mV d) -70mV
d) -70mV
what are the two main factors that maintain the disequilibrium within the cells? a) plasma membrane and leaky sodium channels b) leaky potassium and sodium channels c) active transport (using Na+ K+ ATPase pump) d) protein channels and non diffusible anionic proteins
c) active transport (using Na+ K+ ATPase pum
how does the sodium / potassium pump contribute toward the RMP a) 3K+ out for every 2Na+ in b) 2Na+ out for every 3K in c) 3Na+ out for every 2K+ in d) 2K+ out for every 2Na+in
c) 3Na+ out for every 2K+ in
if there were no anionic proteins in the ICF the resting membrane potential would eventually be destroyed? T F what would the RMP become? why would it eventually be destroyed?
True It would move towards 0mV Due to the continuous leakage of sodium ions (along its concentration gradient) which will destroy the negative charge inside the cell. also, due to the potassium ions leaking along its concentration gradient.
The location at which a neuron interacts with its target cell (either another neuron or a muscle cell, etc.) is called the __________. a) synapse b) junction c) connection d) axoaxonic target
a) synapse
Which of the following synapse types is the most rapid? a) Chemical synapse b) Electrical synapse c) Presynaptic synapse d) None of these is more rapid than the others.
b) Electrical synapse
During the events involved in information transfer across a chemical synapse, which of the following steps would be directly interrupted by exposing a neuron to a calcium channel blocker? a) Neurotransmitter exocytosis from the presynaptic neuron b) Depolarization of the presynaptic neuron c) Binding of neurotransmitters to the postsynaptic membrane d) Depolarization of the postsynaptic membrane
a) Neurotransmitter exocytosis from the presynaptic neuron
Generally speaking, opening chloride channels in the postsynaptic membrane will result in an __________. a) excitatory postsynaptic potential b) excitatory presynaptic potential c) inhibitory postsynaptic potential d) inhibitory presynaptic potential
c) inhibitory postsynaptic potential
Identify the false statement. a) Temporal summation occurs with graded potentials b) EPSPs and IPSPs can summate spatially c) EPSPs and IPSPs can summate temporally d) Spatial summation occurs with action potentials
d) Spatial summation occurs with action potentials
Certain psychosomatic drugs exert their effects by keeping the concentration of neurotransmitters elevated within the synapse. These drugs could exert their effects by: a) inhibiting enzymes associated with the postsynaptic membrane that degrade the neurotransmitter. b) inhibiting reuptake of the neurotransmitter by astrocytes or the presynaptic terminal. c) doing both a and b. d) doing neither a nor b
c) doing both a and b.
Neurotransmitters are important in functioning of __________ synapses. a) chemical b) electrical c) gap d) converging
a) chemical
Which synapse is more common in embryonic tissue?
Electrical synapses
What is structure is present in this synapse that allows rapid impulse conduction?
Gap junctions
Explain what temporal summation is. (2 marks)
When one or more presynaptic neurons fire in rapid order it produces a much greater depolarization of the postsynaptic membrane than would result from a single EPSP;
Multiple sclerosis (MS) is a disease in which the myelin sheaths are destroyed. What process does this interfere with and what would be the consequence?
Demyelination (0.5) interferes with saltatory conduction (0.5), which would result in a slowing down and even permanent cessation of nerve impulse propagation (1).
Name the types of neural synapses and discuss the likelihood of them being an excitatory or inhibitory synapse. (6 marks)
Axosomatic, axoaxonic, axodendritic (1 mark each) Axosomatic more likely to be inhibitory due to the summation of IPSP and EPSP before the axon hillock Axodendritic more likely to be excitatory as they are furthest away from the axon hillock so inappropriate impulses have an opportunity to be inhibited. Axoaxonic equally likely to be either but they are rare
A vegan has decided to stop taking supplementary calcium in addition to their vegetable only diet. What two actions of the neuromuscular junction could this impact? (2 marks)
the vegan is deficient in calcium ions neurotransmitter vesicle secretion at the axon terminal (1) will be impacted as well as signalling of muscle contraction via calcium influx into the sarcoplasmic reticulum (1)
. The movement of which ion contributes most to the resting membrane potential? a) Potassium b) Sodium c) Chloride d) Calcium
a) Potassium
Microelectrode 1 was inserted into a resting cell just underneath its membrane whilst microelectrode 2 was inserted into the centre of the same resting cell. The charge at microelectrode 1 would be ____ and the charge at microelectrode 2 would be_____? a) -70mV and 0mV b) -90mV and -90mV c) -70mV and -70mV d) 0mV and -70mV
a) -70mV and 0mV
At which region in the neuron do all graded potentials meet, as well as determining if an action potential will be propagated? a) Soma b) Axon hillock c) Dendrites d) Axon terminal
b) Axon hillock
What is the resting membrane potential charge? a) +60mV b) -90mV c) -70mV d) -55mV
c) -70mV
. Identify the phenomenon when two graded potentials fire simultaneously close within time from the same location? a) Spatial Summation b) Temporal Summation c) Rapid Summation d) Simultaneous Summation
b) Temporal Summation
Which of the following statements regarding the absolute refractory period is incorrect? a. Important conformational changes in Na+ channels occur during this period of time b. It is crucial to ensuring unidirectional flow of information in the nervous system c. This stage typically occurs over a period of 5ms d. Further action potentials are unable to be generated during this period, irrespective of the magnitude of subsequent stimuli
c. This stage typically occurs over a period of 5ms
- Identify the phenomenon during an action potential, when a neuron is able to fire another action potential only when increased stimulus is available? a) Absolute Refractory Period b) All-Or-Nothing Refractory Period c) Temporal Refractive Period d) Relative Refractory Period
d) Relative Refractory Period
Sodium channels undergo conformation changes following the generation of an AP. Which of the following statements regarding this event is correct? a. At resting membrane potential, both the activation and inactivation gates are set in the closed position b. During repolarisation, the activation gate closes whilst the inactivation gate hangs freely in the open position; c. During depolarisation of the RMP, both the activation and inactivation gates swing to the closed position. d. During repolarisation, the activation gate resets to the closed position, whilst the inactivation gate resets to the open position
d. During repolarisation, the activation gate resets to the closed position, whilst the inactivation gate resets to the open position
Which two factors are primarily dependent for axon velocity? a. The amplitude of the received stimulus and the axon’s degree of myelination b. The diameter of the axon and its degree of myelination c. The All-or-Nothing rule and the diameter of the axon d. The number of voltage-gated receptors available at the axon hillock for summation of the stimulus and the amplitude of the received stimulus
b. The diameter of the axon and its degree of myelination
- Unipolar, Bipolar, & Multipolar are the three types of? a) Functional Neurons b) PNS Neurons c) Structural Neurons d) CNS Neurons
c) Structural Neurons
- Identify the three mechanisms in which neurotransmitter effects are terminated at the post-synaptic membrane: a. Degradation by enzymes b. Diffusion away from the synaptic cleft c. Protein mediated re-uptake into the pre-synaptic membrane d. All of the above
d. All of the above
- Identify the correct mechanism in which promotes potassium movement: a) Potassium moves down its chemical gradient out of the cell from a high concentration to low concentration. However, potassium is pulled back towards the cell due to its electrical gradient from anions, as potassium is a positive ion. b) Potassium moves against its chemical gradient out of the cell from a low concentration to high concentration. However, potassium is pulled back towards the cell due to its electrical gradient from anions, as potassium is a positive ion. c) Potassium moves down its chemical gradient out of the cell from a high concentration to low concentration. Potassium is also pulled out of the cell due to its electrical gradient from anions, as potassium is a positive ion. d) Potassium moves against its chemical gradient out of the cell from a low concentration to high concentration. Potassium is also pulled out of the cell due to its electrical gradient from anions, as potassium is a positive ion.
a) Potassium moves down its chemical gradient out of the cell from a high concentration to low concentration. However, potassium is pulled back towards the cell due to its electrical gradient from anions, as potassium is a positive ion.
- What two factors maintain the chemical disequilibrium? a) Active transport and passive transport b) Active transport and proteins c) Passive transport and proteins d) Passive transport and facilitated transport
b) Active transport and proteins
- Myelinated axons have very fast conduction, which is approximately 30x faster than non-myelinated axons, this type of conduction can be referred as? a) Rapid b) Myelinated a. Saltatory b. Continuous
a. Saltatory
- Which of the following nervous divisions is responsible for mobilizing the body systems during activity? a) Auditory b) Parasympathetic c) Sensory d) Sympathetic
d) Sympathetic
- Information coming out of the central nervous system is transmitted along ________ neurons. a) Afferent b) Auditory c) Efferent d) Parasympathetic
c) Efferent
- The multiple thin, branched structures on a neuron whose main function is to receive incoming signals are the a) Axons b) Cell bodies c) Dendrites d) Synapse
c) Dendrites
- Which structural class of neurons is most abundant in the body? a) Bipolar b) Multipolar c) Tripolar d) Unipolar
b) Multipolar
- Which glial cell is responsible for producing saltatory conduction? a) Astrocytes b) Oligodendrocytes c) Schwann cells d) Schwann cells & oligodendrocytes
d) Schwann cells & oligodendrocytes
- The RMP most closely reflects the equilibrium potential of ________, meaning that ______? a) potassium ions, substantial amounts move into a cell rendering it slightly positive internally b) potassium ions, substantial amounts move out of a cell rendering it slightly negative internally c) sodium ions, substantial amounts move into a cell rendering it slightly negative internally d) sodium ions, substantial amounts move out of a cell rendering it slightly negative internally
b) potassium ions, substantial amounts move out of a cell rendering it slightly negative internally
- If a neuron has a resting RMP of -75mV, and it becomes hyperpolarized, the membrane potential is likely to be approx. ______, and the nerve is______________. a) -65 mV, less likely to fire b) -65 mV, more likely to fire c) -85 mV, less likely to fire d) -85 mV, more likely to fire
) -85 mV, less likely to fire
- Voltage-gated sodium gates in neurons provide for movement of Na+ _______. This movement is due to __________________. a) into cells, due to a chemical gradient alone b) into cells, due to an electrochemical gradient c) out of cells, due to a chemical gradient d) out of cells, due to electrical forces
b) into cells, due to an electrochemical gradient
- High extracellular levels of potassium ions will ____________________. a) depolarize the cell membrane b) hyperpolarize the cell membrane c) hypopolarize the cell membrane d) reduce the RMP to zero
d) reduce the RMP to zero
- What role does the sodium inactivation gate play in action potential (AP) propagation in nerve cells? a) it allows Na+ to move into a nerve cell, stimulating an AP b) it prevents Na+ from entering cells, and so allows APs to move up or down an axon c) it prevents Na+ from entering the cell, and so determines the absolute refractory period d) it prevents Na+ from moving into the cell, while allowing K+ to move freely across the membrane, and determines the relative refractory period
c) it prevents Na+ from entering the cell, and so determines the absolute refractory period
- Which of the following does NOT influence the time necessary for a nerve impulse to be conveyed by a particular neuron? a) diameter of the axon b) length of the axon c) presence or absence of a myelin sheath d) presence or absence of nodes of Ranvier
b) length of the axon
- What determines if a neuron has high excitability and is ready to fire again? a) The intracellular concentration of sodium b) The intracellular concentration of potassium c) Sodium and potassium channels are both in the resting state d) Sodium and potassium channels are both open
c) Sodium and potassium channels are both in the resting state
- Initiation of a second action potential during the relative refractory period can only occur when? a) A stronger than normal stimulus is received b) All the potassium channels are closed c) All the sodium and potassium channels are closed. d) All the sodium channels are closed
a) A stronger than normal stimulus is received
- Which region of a stimulated neuron ‘decides’ whether or not that neuron will fire off an AP? a) axon hillock b) axon terminus c) cell dendrites d) cell nucleus
a) axon hillock
During depolarization, the inside of the neuron’s membrane becomes less negative.
True – depolarization is when the voltage becomes closer to 0 mV
The purpose of the neuron microtubules is intracellular transport between the cell body and the axon terminal
True – Act as tracks for vesicular transport via motor proteins
During depolarization, the inside of the neuron’s membrane becomes less negative.
True – depolarization is when the voltage becomes closer to 0 mV
The membrane potential is solely determined by the movement of K+ ions.
False – RMP includes Na+ , Cl- and Ca2+
ICF has high [Na+] and low [K+]
False – that’s the ECF
Overall an organism is electrically neutral
True – equal numbers of + and – ions
Like all cells, the neurons’ internal organization dictates its function. Neurons have relatively many mitochondria, an extensive network of rough endoplasmic reticulum and many clusters of ribosomes. These cellular features indicate all of the following EXCEPT ________. A) neurons produce many proteins B) neurons have stable, relatively unchanging internal environments C) neurons have a relatively high consumption of oxygen D) neurons must meet a high demand for ATP
B) neurons have stable, relatively unchanging internal environments
The interior surface of a neuron’s plasma membrane at resting membrane potential will have a ________. A) negative charge and contains more sodium than outside of the cell B) positive charge and contains less sodium than outside of the cell C) positive charge and contains more sodium than outside of the cell D) negative charge and contains less sodium than outside of the cell
D) negative charge and contains less sodium than outside of the cell
The all-or-none phenomenon as applied to nerve conduction states that the whole nerve cell must be stimulated for conduction to take place.
False – only one part needs to be stimulated
During depolarization, the inside of the neuron’s membrane becomes less negative.
True – moves closer to zero mV
Strong stimuli cause the amplitude of action potentials generated to increase.
False – it’s the frequency that increases
In myelinated axons the voltage-regulated sodium channels are concentrated at the nodes of Ranvier
True – the gates can only be located in the gaps
The potassium gates close slower than the sodium gates
True – hence the refractory period
The action potential is caused by phospholipid changes in the plasma membrane.
False – it’s the permeability changes via the gated channels
Which of the following is incorrect about graded potentials? a) They are short lived and localized b) They decrease in magnitude with distance c) They are only depolarizing events d) Their magnitude is below the threshold potential
c) They are only depolarizing events
The area of a neuron where an action potential travels is known as what region? a) Receptive region b) Conductive region c) Secretory region d) Sensory region
b) Conductive region
Individual myelin sheaths cover what length of an axon? a) 1 nm b) 1 µm c) 1 mm d) 1m
c) 1 mm
What is the approximate total charge change of an action potential? a) - 70 mV b) 30 mV c) 70 mV d) 100 mV
d) 100 mV
The location at which a neuron interacts with its target cell (either another neuron or a muscle cell, etc.) is called the __________.
a) synapse
b) junction
c) connection
d) axoaxonic target
a) synapse
Which of the following synapse types is the most rapid?
a) Chemical synapse
b) Electrical synapse
c) Presynaptic synapse
d) None of these is more rapid than the others.
b) Electrical synapse
During the events involved in information transfer across a chemical synapse, which of the following steps would be directly interrupted by exposing a neuron to a calcium channel blocker?
a) Neurotransmitter exocytosis from the presynaptic neuron
b) Depolarization of the presynaptic neuron
c) Binding of neurotransmitters to the postsynaptic membrane
d) Depolarization of the postsynaptic membrane
a) Neurotransmitter exocytosis from the presynaptic neuron
Generally speaking, opening chloride channels in the postsynaptic membrane will result in an __________.
a) excitatory postsynaptic potential
b) excitatory presynaptic potential
c) inhibitory postsynaptic potential
d) inhibitory presynaptic potential
c) inhibitory postsynaptic potential
Identify the false statement.
a) Temporal summation occurs with graded potentials
b) EPSPs and IPSPs can summate spatially
c) EPSPs and IPSPs can summate temporally
d) Spatial summation occurs with action potentials
d) Spatial summation occurs with action potentials
Certain psychosomatic drugs exert their effects by keeping the concentration of neurotransmitters elevated within the synapse. These drugs could exert their effects by:
a) inhibiting enzymes associated with the postsynaptic membrane that degrade the neurotransmitter.
b) inhibiting reuptake of the neurotransmitter by astrocytes or the presynaptic terminal.
c) doing both a and b.
d) doing neither a nor b
c) doing both a and b.
Neurotransmitters are important in functioning of __________ synapses.
a) chemical
b) electrical
c) gap
d) converging
a) chemical
Which synapse is more common in embryonic tissue?
Electrical synapses
What is structure is present in this synapse that allows rapid impulse conduction?
Gap junctions
Explain what temporal summation is. (2 marks)
When one or more presynaptic neurons fire in rapid order it produces a much greater depolarization of the postsynaptic membrane than would result from a single EPSP;
Multiple sclerosis (MS) is a disease in which the myelin sheaths are destroyed. What process does this interfere with and what would be the consequence? (2 marks)
Demyelination (0.5) interferes with saltatory conduction (0.5), which would result in a slowing down and even permanent cessation of nerve impulse propagation (1).
Name the types of neural synapses and discuss the likelihood of them being an excitatory or inhibitory synapse. (6 marks)
Axosomatic, axoaxonic, axodendritic (1 mark each)
Axosomatic more likely to be inhibitory due to the summation of IPSP and EPSP before the axon hillock
Axodendritic more likely to be excitatory as they are furthest away from the axon hillock so inappropriate impulses have an opportunity to be inhibited.
Axoaxonic equally likely to be either but they are rare
A vegan has decided to stop taking supplementary calcium in addition to their vegetable only diet. What two actions of the neuromuscular junction could this impact? (2 marks)
If the vegan is deficient in calcium ions neurotransmitter vesicle secretion at the axon terminal (1) will be impacted as well as signalling of muscle contraction via calcium influx into the sarcoplasmic reticulum (1) 26
When the pancreas releases insulin in direct response to blood glucose, this is an example of __________ stimulation. a) humoral b) neural c) hormonal d) negative feedback
a) humoral
Which group of messengers is defined as acting on cells within the same tissue? a) Autocrines b) Hormones c) Paracrines d) Eicosanoids
c) Paracrines
A major difference between neurotransmitters and hormones is that hormones reach their destination via __________. a) direct contact on their target cell b) cerebrospinal fluid c) ducts d) the blood
d) the blood
A major determinant of a hormone’s mechanism of action is __________. a) whether the hormonal molecule is hydrophobic or hydrophilic b) its size c) whether it is rapid acting or slow acting d) if it activates gene activity or not
a) whether the hormonal molecule is hydrophobic or hydrophilic
Receptors for steroid hormones are commonly located __________. a) inside the target cell b) on the plasma membrane of the target cell c) in the blood plasma d) in the extracellular fluid
a) inside the target cell
Interaction with a membranebound receptor will transduce the hormonal message via __________. a) depolarization b) direct gene activation c) a second messenger d) endocytosis
c) a second messenger
When an infant suckles at his mother’s breast, the mother’s neurohypophysis releases oxytocin. This is an example of __________ stimulation. a) humoral b) neural c) hormonal d) negative feedback
b) neural
Second messenger–activating hormones circulate in minute quantities because: a) they are not important signal molecules. b) small concentrations of hormone can activate many intracellular signals via amplification. c) they are continuously released from the gland. d) neurotransmitters also bind to hormone receptors.
b) small concentrations of hormone can activate many intracellular signals via amplification.
Which of the following molecules act as second messengers? a) cAMP b) Ca2+ c) PIP d) All of the above
d) All of the above
In order for a hormone to activate a target cell, the target cell must possess __________. a) a receptor b) a second messenger c) the hormone d) a chaperone
a) a receptor
When the ovaries secrete estrogen in response to the hormone GnRH, this is an example of __________ stimulation. a) humoral b) neural c) hormonal d) negative feedback
c) hormonal
1) Compare the structure and function of endocrine and exocrine glands. (4 marks)
Endocrine glands are ductless glands that release hormones into the surrounding tissue fluid; the hormones diffuse into the blood to be transported to target cells throughout the body (2). Whereas exocrine glands have ducts through which products (such as sweat or saliva) are released to a membrane surface (2).
) Glucagon and insulin both target the cells of the liver and are both made in the pancreas, yet they have very different effects on the cells they target. What accounts for this fact? (1 mark)
Glucagon and insulin use different cell surface receptors.
3) List three factors that target cell activation depends on, after the hormone binds to the receptor. (1.5 marks)
Interaction depends on (1) blood levels of the hormone, (2) relative numbers of receptors for that hormone on or in the target cells, and (3) the affinity (strength) of the binding between the hormone and the receptor.
4) What is the difference between autocrines and paracrines? (2 marks)
Autocrines are self-regulating chemical messengers because their target is the cell from which they are manufactured. Paracrines are chemical messengers that act locally. They tend to affect only the cells immediately around them.
5) How is transcription and translation involved in the steroid hormone pathway? (6 marks)
Steroids bind to an intracellular receptor (0.5) that forms a receptor-hormone complex (0.5) which binds directly to a hormone response element in the DNA (1) By doing that it can initiate transcription of a gene to mRNA (1), via RNA polymerase (0.5), which is subsequently translated into a protein (1) using ribosomes (0.5) It may also inhibit transcription and translation from occurring depending on the steroid hormone (1)
