Week 11

Question 1

Ghrelin

Answer 1

is released into the bloodstream by endocrine cells in the stomach

• Circulating levels of ghrelin rise during fasting and immediately drop upon eating

(i.e. Treating rats/ humans with ghrelin produces a rapid increase in appetite)

Question 2

PYY3-36 -

Answer 2

released into bloodstream from the gut

• Its effects are opposite of ghrelin: levels are low during fasting, and rise right after eating
• PYY3-36 is associated with feelings of satiety with effects of PYY are somewhat like leptin (i.e., satiety-related, hunger inhibiting)

Question 3

Arcuate nucleus of the hypothalamus:

Answer 3

NPY/AgRP (neuropeptide Y/ Aghouti-related protein) neurons

POMC/CART (pro-opiomelanocortin/ cocaine- and
amphetamine-related transcript) neurons

**Only remember abbreviations

Question 4

NPY/AgRP neurons

Answer 4

have appetite stimulating effects:
1) inhibit POMC/CART cells
2) activate paraventricular hypothalamus (PVH, see next)
3) activate lateral hypothalamus (LH)

Question 5

POMC/CART neurons

Answer 5

have appetite suppressing effects:
1) inhibit NPY/AgRP neurons
2) inhibit LH

Question 6

Paraventricular nucleus of the
hypothalamus (PVH)

Answer 6

Activating PVH on its own stimulates appetite:

PVH is a control center of hormones by projecting to pituitary gland and activating hormonal systems to alter metabolism

PVH has projections to brainstem neurons important for
energy balance and food intake

Question 7

Nucleus of the solitary tract (NTS)

Answer 7

is part of a central pathway for feeding behavior:

Appetite-stimulating effects of PVH and LH are relayed to, and
integrated in, the nucleus of the solitary tract (NTS)

Question 8

Cholecystokinin (CCK) –

Answer 8

is yet another peripheral signal that is
released by the gut after ingestion of food high in protein or fat
* CCK release is associated with feelings of satiety
* CCK activates receptors in the vagus nerve, that ascends to the NTS, to signal satiety by inhibiting NPY/AgRP and exciting POMC/CART neurons

Question 9

Leptin/ Insulin - activate ______ and inhibit _______

Answer 9

activate POMC/CART neurons, and inhibit
NPY/AgRP neurons

Question 10

Ghrelin activates

Answer 10

NPY/AgRP neurons

Question 11

PYY3-36 inhibits

Answer 11

NPY/AgRP neurons - shorter time scale

Question 12

POMC/CART neurons prevent eating by inhibiting _____

Answer 12

the LH

Question 13

NPY/AgRP neurons stimulate feeding by ________

Answer 13

activating the LH and PVH

Question 14

Ultradian rhythms

Answer 14

– frequency > once/day
-e.g. rest-activity cycle in humans is 90 min

Question 15

Infradian rhythms

Answer 15

– frequency < once/day
-e.g. menstrual cycle (primates) or estrous cycle (other mammals)

Question 16

endogenous circannual rhythms-

Answer 16

internal mechanisms that
operate on an annual or yearly cycle
– e.g., bird migratory patterns, animals
storing food for the winter, hibernation

Question 17

All animals (and life – plants, fungi, bacteria) produce
________________, internal mechanisms
that operate on an approximately 1-day cycle

Answer 17

endogenous circadian rhythms

Question 18

Free-running rhythm is

Answer 18

a rhythm that occurs when no stimulus resets it; it is still rhythmic, but not phase-locked with day length

Question 19

Phase shift –

Answer 19

shift of activity due to a shift in a synchronizing stimulus
(e.g., changing time zones during airline travel)

Question 20

Zeitgeber -

Answer 20

term used to describe any stimulus that entrains the
circadian rhythm to the earth’s 24 h light/ dark cycle… light is the main
one

Question 21

suprachiasmatic nucleus (SCN) -

Answer 21

part of the hypothalamus and the
main control center of the circadian rhythms
– Located dorsal to the optic chiasm
– Damage to the SCN results in less consistent body rhythms that are
no longer synchronized to environmental patterns of light and dark

• SCN sends information to hypothalamic nuclei (and indirectly, to the
  pineal gland) to modulate body temperature and production of
  hormone

Question 22

SCN lesions:

Answer 22

Makes activity pattern more erratic, but still works

**Therefore, SCN lesions damage the
endogenous rhythm

Question 23

Evidence for SCN as rhythm-maker

Answer 23

• SCN is activated by light
• SCN lesions destroy intrinsic rhythm BUT the rhythm still
  works when light-dark cues are present
• Hamsters with a selective mutation (in a gene called tau), have
  an unusually short circadian rhythm
• Transplantation of SCN cells following lesions, or from SCN of
  mutant to non-mutant (or vice-versa) affects rhythmicity

Question 24

Light resets the SCN via a small branch of the optic nerve known as the __________, that travels directly from the retina to the SCN

Answer 24

retinohypothalamic tract

Question 25

The retinohypothalamic tract comes from a special population of ganglion cells that have their own photopigment called__________

Answer 25

melanopsin – these cells respond directly to light and do not require any input from rods or cones

Question 26

How does a cell “know” how to generate such a rhythm???

Answer 26

* Early work with drosophila pointed to a gene called per (for “period”) * From there, the mechanisms underlying SCN circadian rhythms in mammals were eventually discovered

Question 27

The SCN regulates the _______, an endocrine gland located posterior to the thalamus

Answer 27

pineal gland,

Question 28

Jet lag refers to

Answer 28

the disruption of the circadian rhythms due to crossing time zones – stems from a mismatch of the internal circadian clock and external time

Question 29

The electroencephalogram (EEG)

Answer 29

allowed researchers to discover that there are various stages of sleep * EEG measures brain activity from noninvasive electrodes placed on the scalp

Question 30

Alpha waves are present when

Answer 30

......one begins a state of relaxation * Stage 1 sleep is when sleep has just begun – the EEG is dominated by irregular, jagged, low voltage waves – brain activity begins to decline

Question 31

Stage 2 sleep is characterized by the presence of:

Answer 31

Sleep spindles - 12-14 Hz waves during a burst that lasts at least half a second. – K-complex - a sharp high-amplitude negative wave followed by a smaller, slower positive wave

Question 32

Stage 3 and 4 sleep predominate ______ in the night

Answer 32

early

Question 32

Stage 3 and stage 4 together constitute _______ and are characterized by:

Answer 32

slow wave sleep (SWS) – EEG recording of slow, large amplitude delta waves. – Slowing of heart rate, breathing rate, and brain activity. – Highly synchronized neuronal activity

Question 33

REM sleep is predominant______ in the night

Answer 33

later

Question 33

Rapid eye movement sleep (REM); also known as paradoxical sleep

Answer 33

* EEG waves are irregular, low-voltage and fast (i.e., like waking) * Postural muscles of the body are more relaxed than other stages

Question 34

Cerveau isolé –

Answer 34

“isolated cerebrum” – transection through the mesencephalon; animal shows constant unresponsiveness and signs of continuous SWS

Question 35

Encéphale isolé –

Answer 35

“isolated brain” – animal with transection at level of medulla; shows normal responsiveness and sleep-wake patterns

Question 36

ascending reticular activating system (ARAS)

Answer 36

a collection of anatomical structures with different functions, but there are ”wake-maintaining circuits in this region

Question 37

4 major systems that interact to mediate states of arousal:

Answer 37

1. Forebrain system – that can display SWS by itself (a la Bremer) 2. Brainstem system – that activates forebrain into wakefulness (a la Moruzzi and Magoun) 3. Pontine system – that triggers REM sleep 4. Hypothalamic system – that affects other three brain systems to determine sleep/wake

Question 38

Forebrain system - stimulation of the ________ produces sleepiness, whereas lesions produce insomnia

Answer 38

preoptic area (POA)

Question 38

Forebrain system - Basal forebrain POA neurons become active at onset of sleep and release GABA at a key hypothalamic structure__________ that is important for increasing arousal

Answer 38

- tuberomammillary nucleus -

Question 39

Brain stem system

Answer 39

activates forebrain into wakefulness – consists of several structures that are AChergic and NEergric

Question 40

Brain stem system - locus coeruleus –

Answer 40

major source of NE for entire forebrain; this also has stimulatory effects on alertness

Question 41

Brain stem system - -Reticular formation

Answer 41

collection of cells throughout midbrain and brainstem; many of which are cholinergic (ACh) -ACh neurons project to variety of structures in brain to promote wakefulness

Question 42

Pontine system

Answer 42

triggers REM sleep Small group of cells in pons, just ventral to locus coeruleus, triggers REM sleep

Question 43

Hypothalamic system

Answer 43

acts as a counter-weight to the other three brain systems and ensures smooth transitions between sleep and wakefulness Lateral hypothalamus and tuberomammillary nucleus of the hypothalamus – utilize a peptide transmitter - hypocretin/ orexin

Question 44

Hypothalamic system - Hypocretin/ orexin –

Answer 44

has stimulatory effects on arousal, but its role is more nuanced, since it provides a counter-weight to the other systems to ensure a smoot transition across both sleep and waking states

Question 45

Narcolepsy

Answer 45

person (or animal) has sudden, intense bouts of sleep during day Sleep – last 5-30 minutes

Question 46

cataplexy

Answer 46

sudden loss of muscle tone without loss of consciousness (prob. due to aberrant activity in pontine/REM system)

Question 47

In narcoleptic dogs, a mutant gene was isolated by de Lecea and Kilduff encoding for a receptor of _______ in 1998; at same time Yanagisawa’s group discovered the same thing, and called it_____

Answer 47

hypocretin, orexin