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WorksheetsExcitable Tissues
Total questions: 23
Worksheet time: 26mins
An INCREASE in the magnitude of the membrane potential of a neurone at rest is known as which of the following?
hyperpolarisation
a resting membrane potential
depolarisation
an action potential
hypopolarisation
When the membrane potential of an excitable cell decreases in magnitude from the resting membrane potential (i.e. the inside of the cell becomes less negative) we refer to this type of movement as?
hyperpolarisation
repolarisation
depolarisation
hypopolarisation
none of the above
Which of the following statements about depolarising graded potentials is FALSE?
depolarising graded potentials are elicited by an excitatory stimulus
depolarising graded potentials are fairly transient
the size of the polarising graded potential is dependent upon the size of the stimulus
depolarising graded potentials take the cell away from threshold
none of these statements is false
The membrane potential of a typical excitable tissue cell at rest is usually around?
+50mV
-50mV
0mV
+0.08V
-0.08V
The hyperpolarising phase of the action potential is caused by?
sodium channel inactivation
slow opening of voltage-gated potassium channels
slow-closing of voltage-gated potassium channels
sodium channel activation
voltage-gated sodium ions opening
Which of the following is primarily responsible for the repolarising phase of the action potential?
the sodium/potassium exchange pump
flow of sodium ions out of the cell
flow of sodium ions into the cell
flow of potassium ions into the cell
flow of potassium ions out of the cell
The ion channels that are fundamentally responsible for the magnitude of the resting membrane potential are known as?
voltage-gated K+ channels
resting K+ channels
stretch-gated K+ channels
ligand-gated Na+ channels
voltage-gated Na+ channels
Which of the following are classified as monovalent anions?
sodium ions
potassium ions
chloride ions
calcium ions
none of these are monovalent anions
Which of the following statements about ion concentrations and excitable tissues is FALSE?
the concentration of Na+ is higher in the extracellular fluid than the intercellular fluid
the concentration of Ca2+ is lower in the intracellular fluid than the extracellular fluid
the concentration of Cl- is higher in the extracellular fluid than the intercellular fluid
the concentration of K+ is higher in the extracellular fluid than the intercellular fluid
the concentration of Na+ is lower in the intracellular fluid than the extracellular fluid
Which of the following is/are features of voltage-gated ion channels?
1. a gate whose opening is regulated by the membrane potential
2. a molecular sensor that measures the membrane potential
3. membrane-spanning proteins that act as conduits for ions
3 only
1 & 2 only
1, 2 & 3
1 only
1 & 3 only
Which of the following statements about action potentials is TRUE?
action potentials only affect parts of cells adjacent to the excitatory stimulus
action potentials can travel along axons at speeds of up to 130 Km.sec-1
action potentials can arise from hyperpolarising graded potentials
in most cells action potentials are over in a few milliseconds
action potentials amplitude is directly proportional to excitatory stimulus strength
If an inhibitory stimulus produces a small transient increase in the polarisation of the membrane of a neurone this would be called a?
hypopolarising graded potentional
depolarising resting potential
hyperpolarising resting potential
depolarising graded potential
hyperpolarising graded potential
Excitable tissues relay information about the size of a stimulus using which of the following variables:
1. the amplitude of action potentials
2. the number of action potentials per unit time
3. the duration of action potentials
2 only
1 & 3 only
2 & 3 only
3 only
1 only
Which of the following is/are features of excitable tissue cells at rest?
1. a concentration gradient that favours the movement of Na+ into the cell
2. an electrical gradient that attracts Na+ into the cell
3. voltage-gated Na+ channels that are programmed to close when the membrane potential reaches threshold
3 only
1 & 2 only
1 , 2 & 3
1 & 3 only
1 only
Which of the following is NOT a feature of graded potentials?
they can result in in a decrease in the membrane potential
they only affect a restricted (local) region of the membrane
they can result in an increase in the membrane potential
they alter the excitability of neurons
their size is indirectly proportional to the size of the stimulus
When membrane potential decreases in magnitude from RMP & membrane becomes less polarised, this is known as?
depolarisation
repolarisation
hyperpolarisation
hypopolarisation
T or F. Action potentials can come in different sizes
(a)
Which of the following statements are true for ligand-gated ion channels
channels have molecular sensor that measures MP & opens/closes gate depending on value
ions move through channels freely depending on charge
interaction between ligand & receptor enables specificity in controlling ion channels
channel is regulated by degree of stretch exerted on membrane
T or F. At rest, membrane of excitable tissue cells is freely permeable to K+
(a)
K+ equilibrium potential is -96.9 mV and most excitable cells are -80 mV. Why is there a difference?
small amounts of Na+ enter cell & makes it less negative
leaky channels
more K+ enters cell, therefore, higher equilibrium potential
Na+ leave the cell & makes it less negative
T or F. Voltage-gates Na+ channels are closed at resting MP but open when MP reaches threshold
(a)
What happens in the depolarising phase of an action potential?
Na+ enters the cell
Na+ leaves the cell
K+ enters the cell
K+ leaves the cell
What happens in the repolarising phase of an action potential?
K+ leaves the cell
K+ enters the cell
Na+ leaves the cell
Na+ enters the cell
