FAU: Bio Bases 2, Exam # 1

Zeitgeber

(time giver) -A stimulus that resets the circadian rhythm. -Examples: Sunlight, tides, exercise, meals, arousal of any kind, meals, temperature of environment, etc.

Jet lag

-A disruption of circadian rhythms due to crossing time zones. -A mismatch of the internal circadian clock and external time. -People experience sleepiness during the day, sleeplessness at night, depression and impaired concentration.

Insomnia

-A sleep disorder associated with inadequate sleep. -Caused by noise, stress, pain, diet, and medication -Can be the result of disorders such as epilepsy, Parkinson's disease, depression, anxiety or other conditions -Dependence on sleeping pills or alcohol can also result in insomnia

Sleep Apnea

-A sleep disorder characterized by the inability to breathe while sleeping for a prolonged period of time. -Sleepiness during the day, impaired attention, depression, and sometimes heart problems. -Causes: Genetics, hormones, old age, obesity and deterioration of the brain mechanisms that control breathing. -Cognitive impairment may result.

How light resets the SCN

-A small branch of the optic nerve, known as the retinohypothalamic path, from the retina to the SCN, alters the SCN's settings. -Most of the input to that path does not come from normal retinal receptors. -Example: Mice with genetic defects that destroy nearly all their rods and cones, Blind mole rats -The retinohypothalamic path to the SCN comes from a special population of retinal ganglion cells that have their own photopigment, MELANOPSIN

Locus coeruleus

-A small structure in the pons whose axons release norepinephrine to arouse various areas of the cortex and increases wakefulness. -Usually inactive, especially during sleep, but emits bursts of impulses in response to meaningful events, especially those that produce emotional arousal -Output increases activity of the most active neurons and decreases activity of less active neurons -Results in enhanced attention and enhanced memory

Optogenetics

-A technique that allows researchers to turn on activity in targeted neurons by a device that shines a light within the brain -Use a specially manipulated virus to insert light-sensitive proteins into the membrane of a given type of neuron -Reacts to light by opening a sodium channel, exciting the neuron. -The virus can be altered so that it delivers one of these proteins only to a certain type of neuron, or even to just one part of the neuron.

Endogenous circadian rhythms: mood

-Adults recorded their mood throughout the day. -Most showed increases in positive mood (happiness) from waking until late afternoon, and then a slight decline until bedtime. -Suggests a biologically driven circadian rhythm in our emotional well- being.

Pons

-Area of the hindbrain that sits directly above the medulla. -Serves as a message station between several areas of the brain. -Contains nuclei that relay signals from the forebrain to the cerebellum, along with nuclei that deal with sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, posture, facial expressions and sensation.

Astronauts in orbit face a special problem

-As they orbit the Earth, a 45-minute period of daylight alternates with 45 minutes of darkness. -Constant dim light. -Not fully alert during their wakeful periods or deeply asleep during rest periods. -Many experience depression and impaired performance.

Morning people

-Awaken early -Reach their peak of productivity early -Become less alert later in the day

Functions of the inhibitory neurotransmitter GABA are also important for:

-Decreasing the temperature and metabolic rate -Decreasing the stimulation of neurons

The daily activity of a squirrel kept in total darkness

-Even in an unchanging environment, the animal generates a consistent rhythm of activity and sleep. -Depending on the animal and the details of the procedure, the self- generated cycle may be slightly shorter than 24 hours.

Shift work

-For people who sleep irregularly, sleep duration depends on when one goes to sleep. -Working at night long term does not reliably change the circadian rhythm -People adjust best to night work if they sleep in a very dark room during the day and work under very bright lights at night

Age and gender differences in circadian rhythms

-Morning people are most impaired when working the night shift. -Evening people are most impaired when working the morning shift. -Changes as a function of age.

Reticular formation

-Part of the midbrain that extends from the medulla to the midbrain and is responsible for arousal. -Some neurons of the RF have axons ascending into the brain, and some have axons descending into the spinal cord. -Axons descending into the spinal cord form part of the medial tract of motor control -Neurons with ascending axons have widespread connections and regulate arousal -Has projections to the thalamus and cerebral cortex that allow it to exert some control over which sensory signals reach the cerebrum and come to our conscious attention -It plays a central role in states of consciousness like alertness and sleep

Pontomesencephalon

-Part of the reticular formation that contributes to cortical arousal -Axons from some of the cells release GABA, which inhibits or interrupts behavior and promotes slow-wave sleep -Other axons extend to the hypothalamus, thalamus, and basal forebrain, release acetylcholine and glutamate. -Excitatory effects to widespread areas of the cortex -Stimulation awakens sleeping individuals and increases alertness in those awake

The sun time at the eastern end of Germany differs by about half an hour from that at the western edge. How do the people cope?

-People at the eastern edge have a sleep midpoint 30 mins earlier than those at the west, corresponding to the fact that the sun rises earlier at the eastern edge.

Paradoxial or REM sleep

-REM: Sleep stage with rapid eye movements, high brain activity, and relaxation of the large muscles -Paradoxial sleep: Deep sleep in some ways, but light sleep in other ways. -EEG shows irregular, low-voltage, and fast waves that indicate increased neuronal activity -The EEG record is similar to that for stage 1 sleep -Postural muscles of the body are more relaxed than other stages -Heart rate, blood pressure, and breathing rate are more variable in REM than in stages 2 through 4

All animals produce endogenous circadian rhythms. What are some examples?

-Sleep cycle -Frequency of eating and drinking -Secretion of hormones -Urination -Sensitivity to drugs -Metabolism -Body temperature

Polysomnograph Records: Stage 2 Sleep

-Sleep spindle: Consists of 12 to 14-Hz waves during a burst that lasts at least half a second. -K-complex: A sharp wave associated with temporary inhibition of neuronal firing.

Circadian rhythms: Blind people

-Some set their rhythms by noise, temperature, meals, and activity. -When their cycles are in phase with the clock, all is well, but when they drift out of phase, they experience insomnia at night and sleepiness during the day. -For those who are not sufficiently sensitive to these secondary zeitgebers, do you think their circadian rhythms are longer or shorter than 24 hours?

The biochemistry of the circadian rhythm

-Studies on the fruit fly Drosophila found several genes responsible for a circadian rhythm. -Two types of genes are responsible for generating the circadian rhythm: -Period- Produce proteins called PER -Timeless- Produce proteins called TIM -The concentration of these proteins oscillates over a day, based on feedback interactions among neurons.

The Suprachiasmatic Nucleus (SCN)

-The main control center of the circadian rhythms of sleep and body temperature. -Located above the optic chiasm and is part of the hypothalamus. -SCN generates circadian rhythms in a genetically controlled, unlearned manner -Various cells communicate with each other to sharpen the circadian rhythm

What are the mechanisms of circadian rhythms?

-The suprachiasmatic nucleus -Genes that produce certain proteins -Melatonin levels

Special population of retinal ganglion cells that have their own photopigment, melanopsin.

-These special ganglion cells are located mainly near the nose. -They respond to light slowly and turn off slowly when the light ceases. -Respond mainly to short-wavelength (blue) light.

During REM sleep

-cells in the pons and medulla send messages that inhibit the spinal neurons that control the body's large muscles -Occasionally, most of the brain wakes up while the pons remains in REM -The result is your experience of being temporarily unable to move

hypothalamus

-contains neurons that release histamine to produce widespread excitatory effects throughout the brain -Many antihistamine drugs, often used for allergies, counteract this transmitter and produce drowsiness. -Antihistamines that do not cross the blood-brain barrier avoid that side effect

K- Complex

-have been suggested to protect sleep and to contribute to memory consolidation -Arise spontaneously and can also be evoked -Respond to internal and external stimuli in a reactive manner and are believed to reflect a mechanism of sleep protection -The state they induce allows for "cortical firing 'reboots' in a systematic order" so that memory engrams can be "repeatedly practiced and thus consolidated".

Polysomnograph Records: Stage 3 and 4

-heart rate, breathing rate, and brain activity decrease. -Slow, large-amplitude waves are more common. -Stages 3 and 4 differ only in the prevalence of these slow waves, and some combine them as a single stage, slow-wave sleep (SWS)

Sleep spindles

-increase in number after new learning -The number of sleep spindles correlates positively with improvements in certain types of memory -Represent activity related to the consolidation of memory. -Most are fairly consistent in their amount of spindle activity from one night to another -The amount of spindle activity correlates more than 0.7 with nonverbal tests of IQ

Daily pattern of body temperature

-mean rectal temperatures for 9 adults -body temperature reaches its low for the day about 2 hours after sleep onset. -It reaches its peak about 6 hours before sleep onset

During lucid dreaming,

-someone is dreaming but aware of being asleep and dreaming. -Some brain area is more awake than usual during dreaming, capable of monitoring dreams that the rest of the brain is generating. -Someone having a lucid dream can control the content of the dream to some extent, as well as eye movements. -In one study, young adults learned to use their eye movements to signal the onset of a lucid dream. -When they had lucid dreams about moving their hands, activity increased in the areas of motor cortex responsible for preparing for an actual hand movement.

Polysomnograph Records: Relaxed Wakefulness

-steady series of alpha waves at a frequency of 8 to 12 per second. -Alpha waves are characteristic of relaxation, not of all wakefulness.

Polysomnograph Records: Stage 1 Sleep

-the EEG is dominated by irregular, jagged, low-voltage waves. -Brain activity is less than in relaxed wakefulness but higher than other sleep stages

As the messenger RNA levels increase during the day

-they increase synthesis of the proteins -the process takes time, so the concentrations lag behind.

When people fall asleep,

-they progress through stages 1, 2, 3, and 4 in sequential order. -After about an hour, the person begins to cycle back through the stages from stage 4 to stages 3 and 2 and then REM -The sequence repeats with each cycle lasting approximately 90 minutes

What is the purpose of the circadian rhythm?

-to keep our internal workings in phase with the outside world -"biological clock"

Ordinarily, people fall asleep while their temperature is ________ and awaken while it is ______.

1) declining 2) rising

During the night, the PER and TIM concentrations are _____ and the messenger RNA concentrations are ____

1) high 2) low

Vegetative state

A condition in which someone has decreased brain activity and alternates between wakefulness and sleep but shows only limited responsiveness, such as increased heart rate in response to a painful stimulus.

Minimally conscious state

A condition of decreased brain activity with occasional, brief periods of purposeful actions and limited speech comprehension.

Pineal gland

An endocrine gland located posterior to the thalamus -secretes melatonin

Coma

An extended period of unconsciousness with a low level of brain activity and little or no response to stimuli.

Brain death

Condition with no sign of brain activity and no response to any stimulus.

Traveling _____ phase advances our circadian rhythms

EAST -Going east, we phase-advance to sleep earlier and awaken earlier

What can we use to record the various stages of sleep?

EEG -Records an average of the electrical potentials of the cells and fibers in the brain areas closest to each electrode on the scalp. -Compare brain activity at different times during sleep.

what does light do to the TIM protein?

It inactivates it

orexin or hypocretin

Neurotransmitter that increases wakefulness and arousal. -Axons releasing orexin extend from the hypothalamus to the basal forebrain and many other areas, enhancing wakefulness -Orexin is it is for staying awake especially toward the end of the day

A pathway from the hypothalamus releases a peptide neurotransmitter called

Orexin

Sleep spindles result from

Oscillating interactions between cells in the thalamus and the cortex.

REM sleep is associated with a distinctive pattern of high-amplitude electrical potentials known as

PGO waves, for pons-geniculate- occipital. -PGO waves start in the pons (P) and then show up in the LGN (G) and the occipital cortex (O).

During slow-wave sleep, sensory input to the cerebral cortex is greatly

REDUCED

While asleep, activity increases in the pons, which triggers the onset of

REM sleep, and the limbic system (which is important for emotional responses).

_______ and norepinephrine interrupt REM

Serotonin

What is the dominant zeitgeber for land animals?

Sunlight

T/F: A single isolated SCN cell can maintain a circadian rhythm

TRUE

T/F: You could have substantial inhibition in one brain area and not in another

TRUE

When neurons do fire during sleep,

They fire in synchronous bursts, yielding the high-amplitude waves that characterize slow-wave sleep

What is the dominant zeitgeber for marine animals?

Tides

Traveling ____ phase delays our circadian rhythms

WEST -Going west, we stay awake later at night and then awaken late the next morning, already partly adjusted to the new schedule

polysomnograph

a combination of EEG and eye-movement records

Sleep is characterized by

a moderate decrease in brain activity and decreased response to stimuli.

Mice lacking orexin

alternate between waking and sleeping, even during an activity that causes arousal, such as running in a wheel.

Each PGO wave is synchronized with

an eye movement in REM sleep

Sleep apnea may lead to

brain abnormalities

The next morning, PER and TIM protein levels start to ______

decrease -the flies awaken and the cycle is ready to start again

Sleep depends partly on

decreased sensory input to the cerebral cortex.

REM is strongly associated with

dreaming

Stages 3 and 4 of sleep predominate

early in the night -Length of stage decreases as the night progresses

Someone whose rhythm is phase advanced

falls asleep easily but awakens early

Optogenetic inhibition of orexin neurons causes mice to

go quickly into slow-wave sleep.

Someone whose rhythm is phase delayed

has trouble falling asleep at the usual time.

Drugs that block orexin receptors

help people go to sleep, with fewer side effects, as compared to other drugs marketed for insomnia.

In stage 1 and wakefulness the cortex receives

high-frequency input

Melatonin

hormone secreted by the pineal gland that increases sleepiness

During sleep, neurons in the thalamus become

hyperpolarized -decreasing their readiness to respond to stimuli and decreasing the information they transmit to the cortex.

Both morning people and evening people reach their peak

in the late afternoon or evening

During sleep, axons that release the inhibitory neurotransmitter GABA

increase their activity, interfering with the spread of information from one neuron to another. -Connections from one brain area to another become weaker. -When stimulation doesn't spread, you don't become conscious of it.

Injury to the reticular formation can result in

irreversible coma

REM sleep is predominant

later at night -Length increases as the night progresses.

People with sleep apnea have multiple brain areas that appear to have

lost neurons -they show deficiencies of learning, reasoning, attention, and impulse control.

Early in the morning, the messenger RNA levels responsible for producing PER and TIM start at

low concentrations

Sleepwalkers are asleep in much of the brain, but awake in the

motor cortex and a few other areas. -They generally have their eyes open, orient to the world enough to find their way around, and often remember at least part of what they thought and did while sleepwalking.

Slow waves indicate

neuronal activity is highly synchronized

Stages other than REM are known as

non-REM (NREM) sleep

The SCN regulates waking and sleeping by controlling activity levels in other areas of the brain including the

pineal gland

Drugs that stimulate acetylcholine receptors

quickly move people to REM. -Acetylcholine is important for both wakefulness and REM sleep

Endogenous circadian rhythm

self-generated rhythm that lasts about a day

Endogenous circannual rhythm

self-generated rhythm that lasts about a year

REM is also regulated by

serotonin and acetylcholine.

During wakefulness, acetylcholine's release

sharpens attention—it increases the accurate, reliable detection of sensory stimuli.

Some cases of insomnia relate to

shifts in circadian rhythms.

Because sleep depends on GABA-mediated inhibition,

sleep can be local within the brain.

The human circadian clock generates a rhythm

slightly longer than 24 hours when it has no external cue to set it.

Acetylcholine is released during wakefulness and REM sleep, but not during

slow-wave sleep

Cells of the basal forebrain release

the inhibitory neurotransmitter GABA. -inhibition provided by GABA is essential for sleep -Other axons from the basal forebrain release acetylcholine, which is excitatory and increases arousal.

As the PER and TIM protein concentrations increase

they feed back to inhibit the genes that produce the messenger RNA molecules.

There are individual differences in patterns of

wakefulness and alertness

Evening people

warm up more slowly