Chapter 13 Flashcards
diurnal animal
organism that is active chiefly during daylight
circadian rhythm
Day–night rhythm.
metabolic syndrome
combination of medical disorders, including obesity and insulin abnormalities, that collectively increase the risk of developing cardiovascular disease and diabetes.
biological clock
neural system that times behavior.
biorhythm
inherent timing mechanism that controls or initiates various biological processes.
what processes cycle daily?
Not only does human waking and sleep behavior cycle daily, so also do pulse rate, blood pressure, body temperature, rate of cell division, blood-cell count, alertness, urine composition, metabolic rate, sexual drive, feeding behavior, and responsiveness to medications. The activity of nearly every cell in our bodies, including gene expression, also has a daily rhythm.
What do biological clocks help with?
allows an animal to anticipate events in advance and prepare for them both physiologically and cognitively. And unless external factors get in the way, a biological clock regulates feeding times, sleeping times, and metabolic activity so that they are appropriate to day–night cycles. Biological clocks also regulate gene expression in every cell in the body so that cells function in harmony.
period
time required to complete a cycle of activity.
circannual
yearly; migratory cycles of birds
circadian
Daily; human sleep–wake cycle
ultradian
Less than a day; human eating cycles
infradian
more than a day; human menstrual cycle
do humans have an endogenous biological clock?
yes, it governs sleep-wake behavior
given no external cues, will people stay on a 24 hour cycle?
more or less, but may range from 25-27
free-running rhythm
Rhythm of the body’s own devising in the absence of all external cues.
Zeitgeber
environmental event that entrains biological rhythms: a “time giver.”
entrain
Determine or modify the period of a biorhythm.
rule of thumb to explain the period of free-running rhythms in light or dark
animals expand and contract their sleep periods as the sleep-related period expands or contracts.
when are Zeitgebers effective?
both sunrise and sunset
how many times per day can clocks be adjusted?
morning light sets the biological clock by advancing it, and evening darkness sets the clock by retarding it.
light pollution
exposure to artifical light that changes activity patterns and so distrupts circadian rhythms.
jet lag
fatigue and disorientation resulting from rapid travel through time zones and exposure to a changed light–dark cycle.
problems associated with light pollution
a great deal of inconsistent behavior associated with accidents, daytime fatigue, alterations in emotional states, and obesity and diabetes.
suprachiasmatic nucleus (sCn)
master biological clock, located in the hypothalmus just above the optic chiasm.
retinohypothalamic tract
neural route formed by axons of photosensitive retinal ganglion cells from the retina to the suprachiasmatic nucleus; allows light to entrain the rhythmic activity of the scn
what other neural structures display clock-like activity besides the SCN?
intergeniculate leaflet; pineal gland
when are neurons of the SCN most active?
neurons in this region are more active during the light period of the cycle than during the dark period.
what can entrain the SCN?
a regular feeding schedule
how do SCN cells synchronize?
SCN cells connect one to another through inhibitory GABA synapses, and these connections allow them to act in synchrony. Their entrainment depends upon external inputs.
where does the retinohypothalamic tract begin?
This pathway begins with specialized retinal ganglion cells (RGCs) that contain the photosensitive pigment melanopsin. These melanopsin-containing, or photosensitive RGCs, receive light-related signals from the rods and cones and send that information to visual centers in the brain. However, pRGCs also can be activated directly by certain wavelengths of blue light in the absence of rods and cones.
retinal ganglion cells
distributed across the retina and, in hu- mans, make up between 1 and 3 percent of all RGCs. Their axons project to various regions in the brain, including the SCN, which they innervate bilaterally.
Melanopsin- containing ganglion cells
use glutamate as their primary neurotransmitter but also contain two cotransmitters, substance P and pituitary adenylate cyclase-activating polypeptide (PACAP).
how many parts make up the SCN?
two; more ventrally located core and a more dorsally located shell.
what activates the core cells of the SCN?
The retinohypothalamic tract
core neurons
are not rhythmic, but they entrain the shell neurons, which are rhythmic.
where does the SCN receive projections from?
These include the intergeniculate leaflet in the thalamus and the raphé nucleus, the nonspecific serotonergic ac- tivating system of the brainstem.
what entrains the SCN?
is usually entrained by morning and evening light, but it can also be entrained or disrupted by sudden changes in lighting, by arousal, by moving about, and by feeding.
what other pathways influence SCN?
The intergeniculate leaflet and the raphé nucleus are pathways through which other photic and nonphotic events influence the SCN rhythm
how many groups of circadian neurons are there?
2: M cells and E cells
M cells
control morning activity and need morning light for entrain- ment;
E cells
control evening activity and need darkness onset for entrainment
where are the “timing devices” located?
in each SCN neuron and in most other cells of the body as well.
chronotype
individual differences in circadian activity.
dimer
two proteins combined into one.
circadian rhythm feedback loop
in which proteins are first made and then combine. The combined protein, called a dimer for “two proteins,” inhibits the production of its component proteins. Then the dimer degrades and the process begins anew
what produces cellular rhythm?
the increase and decrease in protein synthesis
SCN and Slave Oscillator
light entrains the SCN, and the pacemaker in turn drives a number of “slave” oscillators. Each slave oscillator is responsible for the rhythmic occurrence of one activity. In other words, drinking, eating, body temperature, and sleeping are each produced by a separate slave oscillator.
How does the SCN clock entrain slave oscillators?
- SCN neurons send axonal connections to nuclei close by in the hypothalamus and thalamus. These nuclei in turn have extensive connections with other brain and body structures to which they pass on the entraining signal.
- The SCN connects with pituitary endocrine neurons to control the release of a wide range of hormones. These hormones circulate through the body to entrain many body tissues and organs.
- The SCN also sends indirect messages to autonomic neurons in the spinal cord to inhibit the pineal gland from producing the hormone melatonin, which influences daily and seasonal biorhythms.
what controls the release of melatonin?
The SCN controls the release of melatonin from the pineal gland so that it circulates during the dark phase of the circadian cycle, and it controls the release of glucocorticoids from the adrenal gland so that they circulate during the light phase of the circadian cycle.
what does melatonin do?
sleep-promoting actions and influences the parasympathetic rest and digest system.
what do glucocorticoids do?
mobilize glucose for cellular activity and can support arousal responses in the sympathetic system.
melatonin
hormone secreted by the pineal gland during the dark phase of the day– night cycle; influences daily and seasonal biorhythms.
besides daily rhythms, what does the SCN control?
circannual rhythms
is the pineal glad a slave oscillator?
The control that the pineal gland exerts over the gonads is in turn controlled by the supra- chiasmatic nucleus. Through connections in the autonomic nervous system, the SCN drives the pineal gland as a slave oscillator.
why do we think circadian rhythms play a role in cognitive and emotional functions?
- The extent to which a process depends on the expenditure of metabolic energy dictates optimal times for its activity during the circadian cycle.
- Many cognitive events require changes in gene expression, either turning on or turning off genes.
- The time of day can serve as a good index for the “time and place” at which things should happen.
electroencephalogram (EEG)
Electrodes pasted onto standard locations on the skull’s surface; record of brain-wave activity.
electromyogram (EMG)
Electrodes placed on neck muscles; record muscle activity
electrooculogram (EOG)
Electrodes located near the eyes; record of eye movements.
beta (b) rhythm
fast brain-wave activity pattern associated with a waking eeg.
delta (d) rhythm
slow brain-wave activity pattern associated with deep sleep.
atonia
no tone; condition of complete muscle inactivity produced by the inhibition of motor neurons.
ReM sleep
fast brain-wave pattern displayed by the neocortical eeg record during sleep.
nReM (non-ReM) sleep
slow-wave sleep associated with delta rhythms
slow-wave sleep
nRem sleep.
Waking State
When a person is awake, the EEG pattern consists of small-amplitude (height) waves with a fast frequency (repetition period); (b) rhythm, the EMG is active, and the EOG indicates that the eyes move.
frequency of Beta-rhythm waves
ranging from 15 to 30 Hz (times per second).
Drowsy State
When a person becomes drowsy, the EEG indicates that beta-wave activity in the neocortex disappears. The amplitude of the EEG waves increases, and their frequency becomes slower. Concurrently, the EMG remains active, as the muscles have tone, and the EOG indicates that the eyes are not moving.
alpha rhythm
large, extremely regular brain waves with a frequency ranging from 7 to 11 Hz; drowsy state
sleeping state
As participants enter deeper sleep, they produce yet slower, larger EEG waves called delta (d) rhythms. The slowing of brain-wave activity is associated with the loss of consciousness that characterizes sleep. Still, the EMG indicates muscle activity, signifying that the muscles retain tone, although the EOG indicates that the eyes do not move.
frequency of delta rhythms
1 to 3 Hz.
sleep stages
the sleeper moves from relatively shallow sleep in stage 1 to deep sleep in stage 4; stage 4 is the deepest
What is unique about EEG during REM?
activity shows a waking pattern
how long does the NREM-REM sequence last?
~90 minutes; about 5 times over the course of the sleep period
How much REM do we get?
~2 hours over an 8 hour night; vary at different times of life. Periods of REM sleep increase during growth spurts, in conjunction with physical exertion, and for women during pregnancy.
what happens during REM sleep?
body temperature declines, heart rate decreases, blood flow decreases, body weight decreases because of water loss in perspiration, and levels of growth hormone increase. Our eyes move, our toes, fingers, and mouths twitch, and males have penile erections. Still, we are paralyzed, as indicated by atonia
what happens during NREM sleep?
we toss and turn in bed, pull on the covers, and engage in other movements, may talk in our sleep
What stops working during REM sleep?
mechanisms that regulate body temperature stop working, and body temperature moves toward room temperature.
when does dreaming occur?
REM sleep
night terrors
brief, very frightening dreams; can be so vivid that the child may continue to experience the dream and the fear after awaking.
does everyone dream?
everyone dreams, that they dream a number of times each night, and that dreams last longer as a sleep session progresses.
How long do dreams last?
dreams appear to take place in real time
manifest content of a dream
series of often bizarre, loosely connected images and actions.
latent content of a dream
contains its true meaning
what are most dreams about?
more than 64 percent are associated with sadness, anxiety, or anger. Only about 18 percent are happy
activation-synthesis hypothesis
during a dream, the cortex is bombarded by signals from the brainstem, and these signals produce the pat- tern of waking (or activated) EEG. The cortex, in response to this excitation, generates images, actions, and emotion from personal memory stores. In the absence of external verification, these dream events are fragmented and bizarre and reveal nothing more than that the cortex has been activated.
Dreams as Coping
dreams are biologically adaptive in that they lead to enhanced coping strategies in dealing with threatening life events; approach behavior occurs more frequently in dreams than does avoidance behavior
sleep as biological adaptation
Sleep serves as an energy-conserving strategy to cope with times when food is scarce; Whether a species is predator or prey influences its sleep behavior; Strictly nocturnal or diurnal animals are likely to sleep when they cannot travel easily.
basic rest-activity cycle (BRAC)
Recurring cycle of temporal packets, about 90-minute periods in humans, during which an animal’s level of arousal waxes and wanes.
Sleep–conserving energy
During sleep, energy is not being expended in moving the body or supporting its posture. The brain is a major energy user, so switching off the brain during sleep, espe- cially NREM sleep, conserves energy. The drop in body temperature that typically accompanies sleep slows metabolic activity, so it too contributes to energy conservation.
BRAC and sleep
BRAC rhythm is so fundamental that it cannot be turned off. Accordingly, for a night’s sleep to be uninterrupted by periodic waking (and perhaps snacking), the body is paralyzed and only the brain is active.
sleep deprivation
does not seem to have adverse physiological consequences, but it is associated with poor cognitive performance. Performance on tasks that require attention declines as a function of hours of sleep deprivation. Irregular sleep can be associated with metabolic syndrome,
what does sleep deprivation disrupt?
sustained attention
microsleep
Brief period of sleep lasting a second or so.
consolidation
the process of stabilizing a memory trace after learning; may involve a memory “moving” from an initial coding site in one part of the brain to a permanent location in another part.
REM Sleep deprivation
- Participants show an increased tendency to go into REM sleep in subsequent sleep sessions, so awakenings must become more and more frequent.
- After REM deprivation, participants experience “REM rebound,” showing more than the usual amount of REM sleep in the first available sleep session.
Episodic Memory
includes conscious information, such as our autobiographical memories and knowledge of facts
Implicit Memory
includes unconscious processes such as motor-skills learning.
what suppresses REM sleep?
Virtually all antidepressant drugs, including MAO inhibitors, tricyclic antidepressants, and SSRIs,
reconsolidation
the process of restabilizing a memory trace after the memory is revisited.
sleep spindle
Brief burst of eeg activity typically occurring during nRem sleep.
K-complex
sharp, high-amplitude eeg wave occurring during nRem sleep
place cell
hippocampal neurons maximally responsive to specific locations in the world.
stage 2
sleep spindles; k complexes
what do sleep spindles and k complexes play a role in?
memory
what does NREM sleep play a role in?
consolidating an explicit memory
REM and implicit memory
REM sleep is associated with the replay of implicit memory and may be related to the storage or consolidation of that memory.
storage of memories during sleep
proposal that elaborate memories are formed during sleep and then pruned to more useful dimensions during waking. yet is unlikely bc there are large variations in how long people sleep, and there are conditions in which people have little or no REM sleep.
melatonin
hormone secreted from the pineal gland during the dark phase of the light–dark cycle, causes sleepiness, and a synthetic form can be taken as an aid for sleep, so melatonin might be thought to be the sleep-producing substance.
how is sleep produced?
slave oscillator of the su- prachiasmatic nucleu
reticular activating system (Ras)
large reticulum (mixture of cell nuclei and nerve fibers) that runs through the center of the brainstem; associated with sleep–wake behavior and behavioral arousal; often called the reticular formation.
coma
prolonged state of deep unconsciousness resembling sleep.
Neural basis of EEG
The basal forebrain contains large cholinergic cells. These neurons secrete acetylcho- line (ACh) from their terminals onto neocortical neurons to stimulate a waking EEG (beta rhythm). The midbrain structure, the median raphé, contains serotonin (5-HT) neurons whose axons also project diffusely to the neocortex, where they also stimulate neocortical cells to produce a beta rhythm, recorded as a waking EEG.
cholingeric EEG
responsible for the waking associated with being still yet alert,
serotonergic EEG
responsible for the waking EEG associated with movement.
Are the basal forebrain system and median raphé system responsible for behavior?
no
peribrachial area
cholinergic nucleus in the dorsal brainstem having a role in Rem sleep behaviors; projects to medial pontine reticulum.
medial pontine reticular formation (MpRF)
nucleus in the pons participating in Rem sleep.
insomnia
Disorder of slow-wave sleep resulting in prolonged inability to sleep.
narcolepsy
slow-wave sleep disorder in which a person uncontrollably falls asleep at inappropriate times.
what happens if the medial pontine reticular formation or the peribrachial area are destroyed?
abolish REM sleep
medial pontine reticular formation sends projections
to activate basal forebrain cholinergic neurons, resulting in an activated EEG recorded from the cortex.
medial pontine reticular formation excites
brainstem motor nuclei to produce rapid eye movements and other twitches.
hows is the atonia of REM sleep produced?
by the MPRF through a pathway that sends input to the subcoerulear nucleus, located just behind i
hows is the paralysis of REM sleep produced?
The subcoerulear nucleus excites the magnocellular nucleus of the medulla, which sends projections to the spinal motor neurons to inhibit them so that paralysis is achieved during the REM-sleep period.
neural control of sleep
peribrachial area initiates REM–>
medial pontine reticular formation produces REM-related activities–> EITHER
(activated EEG in neocortex produced by basal forebrain nuclei)
(excited brainstem nuclei produce REM and other twitching movements)
(loss of muscle tone produced by the subcoerulear nucleus exciting the magnocellular nucleus of the medulla)–>
inhibits spinal motor neurons
fatal famial insomnia,
causes individuals to stop sleeping altogether.
drug-dependency insomnia
condition resulting from continuous use of “sleeping pills”; drug tolerance also results in deprivation of either Rem or nRem sleep, leading the user to increase the drug dosage.
sleep apnea
inability to breathe during sleep; person has to wake up to breathe.
sleep paralysis
inability to move during deep sleep owing to the brain’s inhibition of motor neurons.
cataplexy
form of narcolepsy linked to strong emotional stimulation in which an animal loses all muscle activity or tone, as if in Rem sleep, while awake.
hypnogogic hallucination
Dreamlike event at the beginning of sleep or while a person is in a state of cataplexy.
waking
what we colloquially refer to as “waking” com- prises at least two different states: alert consciousness, mediated by the cholinergic system, and consciousness with movement, mediated by the serotonergic system.
