4/9/25, 7:39 Module 4- psyc 388 |
AM
MODULE 4- PSYC 388 EXAM QUESTIONS AND ANSWERS WITH
COMPLETE SOLUTIONS VERIFIED
- circadian timekeeping system in multicellular organisms contains many
oscillators, playing different roles, in a hierarchy.
- Oscillator: as any device that produces a rhythm.
- pacemaker: 'master oscillator' that controls the timing of other oscillators
or directly driven processes.
- An oscillator might be incapable of keeping a rhythm on its own, and may
be completely dependent on signals from the pacemaker. We might be
Terminology: inclined to call this a 'directly driven process', and not a true oscillator at all.
Alternatively, we might call this a 'slave oscillator'. Without the pacemaker, the
-oscillator: slave oscillator stops. Oscillators can be 'masters', or 'slaves', or they can be
-pacemaker: something in-between. We can call these 'secondary' or 'local' oscillators.
Use orchestra as a metaphor, - Local oscillators would be those found in a specific body tissue or organ or
- is an oscillator incapable of keeping a brain region, which are responsible for inducing circadian rhythms in the
rhythm? functions of that particular tissue, organ or brain region. Removal of a local
- what r Local oscillators? oscillator would affect rhythmicity in the affected tissue, and may have no effect
- Removal of a local oscillator ? on rhythms elsewhere in the organism.
- how many pacemakers do we have? - Removal of a pacemaker, by contrast, would affect rhythms throughout the
organism. In the absence of a pacemaker, local oscillators may continue to
oscillate, but would eventually become desynchronized from other local
oscillators, resulting in loss of circadian rhythmicity at the level of the whole
tissue or organ.
- Circadian pacemakers follow the cycles of nature, most importantly the
rising and setting of the sun. There could be multiple pacemakers, with one
responding to light, and others responding to nonphotic stimuli such as
temperature or food.
In everyday life, we speak of clocks and watches, not of oscillators and
pacemakers. When an oscillator (or pacemaker) is synchronized to the external
world, a specific phase of the oscillator (the current position of the oscillator
or pacemaker within its cycle) corresponds to a particular time of day in the
Oscillator can serve as a clock:
local environment. If the phase of the oscillator represents a time of day, then the
oscillator can serve as a clock. This definition aligns with our everyday notion of a
clock. It is a device that allows us to know the time of day, even if we cannot see
whether the sun is up, or where it is in the sky.
There are other types of timing devices:
1. 'interval timer', which can time one cycle, but then stops and needs to be
reset. It is not an oscillator.
Hourglass clocks are an example of an interval timer; an hourglass clock has two
There are other types of timing compartments connected by a narrow neck. The hourglass clock is built such that
devices: give eg one compartment can be filled with an amount of sand that takes an hour (or
'interval timer'? is it an oscillator? eg some other duration) to completely empty into the other compartment under the
of one? force of gravity can measure an hour (or some other interval). We call this a 'clock',
egs of interval timer? but it is limited to timing one set interval, and does not provide information about
time of day.
Stopwatches are another example of an interval timer. Stopwatches can be
distinguished from hourglass clocks because they are flexible, that is, they can be
used to measure any interval.
Circadian clocks have three defining characteristics.
Turning an oscillator into a clock: 1. They are self-sustaining and persist with an ~ 24h periodicity in
Circadian clocks have three defining constant conditions
characteristics? 2. They are temperature compensated
3.They are entrainable by environmental stimuli
1/12
, 4/9/25, 7:39 Module 4- psyc 388 |
AM
- circadian clocks coordinate behaviour and physiology with predictable daily
events in the real world.
- Circadian clocks can act like alarm clocks, and trigger behavioural or
physiological events at appropriate times of day.
- Circadian clocks act as wristwatches (also called 'continuously consulted
clocks'), enabling animals to recognize and remember multiple times of day at
which important things (like food) are encountered. The circadian wristwatch
Turning an oscillator into a clock:
enables some animals to use the sun as a landmark for travel (time-
give eg of different roles of
compensated sun compass orientation).
Circadian clocks?alarm clocks,
- Circadian clocks are also used to measure day length (photoperiodism) and
wristwatches & measure day
thereby permit some species to organize their behaviour and physiology into
length?
annual rhythms.
To accomplish these functions, the
- It is self-evident that to accomplish these functions, the circadian clock must
circadian clock must have astable 'phase
have astable 'phase relationship' with the solar day. If the circadian clock is not
relationship' with what?
synchronized to the LD cycle, then its phase will not be predictive of local
entrainment?
environmental time, and outside of controlled environments (e.g., a zoo,
household or laboratory) it may be worse than useless. It would cause animals to
wake up and go to sleep at the wrong time of day for finding food and mates and
staying safe.
- Synchrony is critical. The mechanism by which synchrony is achieved is
called entrainment.
entrainment: The mechanism by which synchrony is achieved is called entrainment.
1. First, circadian clocks cycle with a periodicity that only approximates the
24h day. The process of entrainment must somehow adjust the clock on a
regular basis so that it does not drift out of synchrony with the outside world (as
it does when organisms are kept in constant light or dark).
2.Second, the process of entrainment must somehow ensure that organisms
Turning an oscillator into a clock:
do the right thing at the right time of day. In strictly diurnal animals, vision is
Entrainment must solve two problems:
usually the dominant sense, and night vision is weak. To be useful, the
what is the objective of entrainment?
circadian clock must be synchronized to the outside world such that sleep
and waking states occur at the appropriate time of day.
- objective of entrainment is to control both the period and the phase of the
circadian clock, to align it stably with the environment. Any external stimulus that
can entrain a circadian clock is called a Zeitgeber (German for 'time- giver').
Zeitgeber Any external stimulus that can entrain a circadian clock.
- Masking refers to a direct effect of an environmental stimulus on
behavioural state. Light and dark can directly affect behaviour.
- In diurnal animals, light tends to stimulate (or at least permit) activity and
increase alertness, while in nocturnal animals, light inhibits activity and promotes
sleep.
Masking: - Among chronobiologists, the direct effect of light on behaviour is called
diurnal animals and nocturnal rodents masking because light can 'mask' the true phase of the circadian clock.
eg? - Nocturnal rodents are normally active at night, but if the lights are turned on,
'negative masking' they become quiet, and may even go to sleep. This is called 'negative
'positive masking masking', because light is suppressing a behaviour that would normally be
present at that time of day.
- Nocturnal rodents in a laboratory cage normally sleep in the day, but if the
lights are abruptly turned off, the may become active. This is called 'positive
masking', because darkness is stimulating a behaviour that would normally be
absent at that time of day.
- A consequence of the direct effect of light and dark on behaviour is that a light-
Masking: dark cycle could induce a daily rest-activity rhythm in an animal that has no
what is the consequence of the functional circadian clock, due to a brain lesion or gene mutation.
direct effect of light and dark on - Such an animal might appear to be entrained by LD, despite lacking any
behaviour an animal that has no internal clock that could be entrained. This, as you recall, was the issue
2/12
AM
MODULE 4- PSYC 388 EXAM QUESTIONS AND ANSWERS WITH
COMPLETE SOLUTIONS VERIFIED
- circadian timekeeping system in multicellular organisms contains many
oscillators, playing different roles, in a hierarchy.
- Oscillator: as any device that produces a rhythm.
- pacemaker: 'master oscillator' that controls the timing of other oscillators
or directly driven processes.
- An oscillator might be incapable of keeping a rhythm on its own, and may
be completely dependent on signals from the pacemaker. We might be
Terminology: inclined to call this a 'directly driven process', and not a true oscillator at all.
Alternatively, we might call this a 'slave oscillator'. Without the pacemaker, the
-oscillator: slave oscillator stops. Oscillators can be 'masters', or 'slaves', or they can be
-pacemaker: something in-between. We can call these 'secondary' or 'local' oscillators.
Use orchestra as a metaphor, - Local oscillators would be those found in a specific body tissue or organ or
- is an oscillator incapable of keeping a brain region, which are responsible for inducing circadian rhythms in the
rhythm? functions of that particular tissue, organ or brain region. Removal of a local
- what r Local oscillators? oscillator would affect rhythmicity in the affected tissue, and may have no effect
- Removal of a local oscillator ? on rhythms elsewhere in the organism.
- how many pacemakers do we have? - Removal of a pacemaker, by contrast, would affect rhythms throughout the
organism. In the absence of a pacemaker, local oscillators may continue to
oscillate, but would eventually become desynchronized from other local
oscillators, resulting in loss of circadian rhythmicity at the level of the whole
tissue or organ.
- Circadian pacemakers follow the cycles of nature, most importantly the
rising and setting of the sun. There could be multiple pacemakers, with one
responding to light, and others responding to nonphotic stimuli such as
temperature or food.
In everyday life, we speak of clocks and watches, not of oscillators and
pacemakers. When an oscillator (or pacemaker) is synchronized to the external
world, a specific phase of the oscillator (the current position of the oscillator
or pacemaker within its cycle) corresponds to a particular time of day in the
Oscillator can serve as a clock:
local environment. If the phase of the oscillator represents a time of day, then the
oscillator can serve as a clock. This definition aligns with our everyday notion of a
clock. It is a device that allows us to know the time of day, even if we cannot see
whether the sun is up, or where it is in the sky.
There are other types of timing devices:
1. 'interval timer', which can time one cycle, but then stops and needs to be
reset. It is not an oscillator.
Hourglass clocks are an example of an interval timer; an hourglass clock has two
There are other types of timing compartments connected by a narrow neck. The hourglass clock is built such that
devices: give eg one compartment can be filled with an amount of sand that takes an hour (or
'interval timer'? is it an oscillator? eg some other duration) to completely empty into the other compartment under the
of one? force of gravity can measure an hour (or some other interval). We call this a 'clock',
egs of interval timer? but it is limited to timing one set interval, and does not provide information about
time of day.
Stopwatches are another example of an interval timer. Stopwatches can be
distinguished from hourglass clocks because they are flexible, that is, they can be
used to measure any interval.
Circadian clocks have three defining characteristics.
Turning an oscillator into a clock: 1. They are self-sustaining and persist with an ~ 24h periodicity in
Circadian clocks have three defining constant conditions
characteristics? 2. They are temperature compensated
3.They are entrainable by environmental stimuli
1/12
, 4/9/25, 7:39 Module 4- psyc 388 |
AM
- circadian clocks coordinate behaviour and physiology with predictable daily
events in the real world.
- Circadian clocks can act like alarm clocks, and trigger behavioural or
physiological events at appropriate times of day.
- Circadian clocks act as wristwatches (also called 'continuously consulted
clocks'), enabling animals to recognize and remember multiple times of day at
which important things (like food) are encountered. The circadian wristwatch
Turning an oscillator into a clock:
enables some animals to use the sun as a landmark for travel (time-
give eg of different roles of
compensated sun compass orientation).
Circadian clocks?alarm clocks,
- Circadian clocks are also used to measure day length (photoperiodism) and
wristwatches & measure day
thereby permit some species to organize their behaviour and physiology into
length?
annual rhythms.
To accomplish these functions, the
- It is self-evident that to accomplish these functions, the circadian clock must
circadian clock must have astable 'phase
have astable 'phase relationship' with the solar day. If the circadian clock is not
relationship' with what?
synchronized to the LD cycle, then its phase will not be predictive of local
entrainment?
environmental time, and outside of controlled environments (e.g., a zoo,
household or laboratory) it may be worse than useless. It would cause animals to
wake up and go to sleep at the wrong time of day for finding food and mates and
staying safe.
- Synchrony is critical. The mechanism by which synchrony is achieved is
called entrainment.
entrainment: The mechanism by which synchrony is achieved is called entrainment.
1. First, circadian clocks cycle with a periodicity that only approximates the
24h day. The process of entrainment must somehow adjust the clock on a
regular basis so that it does not drift out of synchrony with the outside world (as
it does when organisms are kept in constant light or dark).
2.Second, the process of entrainment must somehow ensure that organisms
Turning an oscillator into a clock:
do the right thing at the right time of day. In strictly diurnal animals, vision is
Entrainment must solve two problems:
usually the dominant sense, and night vision is weak. To be useful, the
what is the objective of entrainment?
circadian clock must be synchronized to the outside world such that sleep
and waking states occur at the appropriate time of day.
- objective of entrainment is to control both the period and the phase of the
circadian clock, to align it stably with the environment. Any external stimulus that
can entrain a circadian clock is called a Zeitgeber (German for 'time- giver').
Zeitgeber Any external stimulus that can entrain a circadian clock.
- Masking refers to a direct effect of an environmental stimulus on
behavioural state. Light and dark can directly affect behaviour.
- In diurnal animals, light tends to stimulate (or at least permit) activity and
increase alertness, while in nocturnal animals, light inhibits activity and promotes
sleep.
Masking: - Among chronobiologists, the direct effect of light on behaviour is called
diurnal animals and nocturnal rodents masking because light can 'mask' the true phase of the circadian clock.
eg? - Nocturnal rodents are normally active at night, but if the lights are turned on,
'negative masking' they become quiet, and may even go to sleep. This is called 'negative
'positive masking masking', because light is suppressing a behaviour that would normally be
present at that time of day.
- Nocturnal rodents in a laboratory cage normally sleep in the day, but if the
lights are abruptly turned off, the may become active. This is called 'positive
masking', because darkness is stimulating a behaviour that would normally be
absent at that time of day.
- A consequence of the direct effect of light and dark on behaviour is that a light-
Masking: dark cycle could induce a daily rest-activity rhythm in an animal that has no
what is the consequence of the functional circadian clock, due to a brain lesion or gene mutation.
direct effect of light and dark on - Such an animal might appear to be entrained by LD, despite lacking any
behaviour an animal that has no internal clock that could be entrained. This, as you recall, was the issue
2/12
