Module 11 Flashcards
To be entrained to local time, the circadian clock must have access to information about ______ (photic entrainment) and ______ (non-photic entrainment)
- the timing of dawn and dusk
- the timing of meals, the behavioural state of the animal, or other stimuli
Rods are specialized to ___ vision and cones are specialized for ____ vision
- night
- day
Rods and cones contain ____ that absorb light
photopigments
Absorbtion of light triggers _______ that alter ______
- intracellular second messenger pathways
- the amount of neurotransmitters that rods and cones release
Changes in neurotransmitter release by rods and cones alters _______ which, along with _____, send information to _____
- Neural activity in horizontal and bipolar cells
- amacrine cells
- retinal ganglion cells
What are the output neurons of the retina?
Ganglion cells
The axons of ganglion cells make up the _____
Optic nerves
How does loss of rods and cones in mice affect their circadian response to light?
Does not affect their ability to phase shift and entrain to light
How does the functioning of melanopsin-containing retinal ganglion cells work?
The cells have long dendritic trees, which are photoreceptive and send information to the SCN
Melanopsin-containing retinal cells are also called ______
Intrinsically photoreceptive melanopsin-containing ganglion cells (ipRGCs)
What happened to melanopsin KO mice?
They still responded to light cues
What gene mutation is required to make mice circadian blind?
Mutation to make the melanopsin gene undergo cell death, eliminating ipRGCs that connect to the SCN
The retina innervates the SCN directly through the ______
Retinohypothalamic tract (RHT)
The RHT originates from neurons in the ______
Intergeniculate leaflet (IGL) of the thalamus
SCN action potentials code for ____
Total illuminance - the total number of photons falling on the retina
SCN neurons have ______ receptors, which is the main _____ in the brain
- glutamate
- depolarizing transmitter
What is most likely the photic neurotransmitter for shifting SCN clocks?
Glutamate
In Syrian hamsters, NDMA injections to the SCN early in the subjective night cause ______, and late in the subjective night cause ______ - the same as _______
- phase delay
- phase advance
- short light pulses
What happens if a drug that blocks glutamate receptors is injected before a light pulse?
The pulse does not induce a phase shift
What does cfos do?
Expression is turned on when neurons are depolarized, correlated with phase shifting
IGL lesions that eliminate ___ in the SCN prevent entrainment of free-running rhythms by a ______
- NPY
- daily exercise schedule
In Syrian hamsters, stimulation of the IGL with electric currents or stimulation of the SCN with NPY both _______
Induce phase shifts like those by exercise in the middle of the subjective day
NPY neurons are activated by _____
Exercise
In mice, lesions to the median raphe prevent _______
Full entraining effects of exercise in mice
Raphe nuclei use _____ as a neurotransmitter
Serotonin (5HT)
Which neurotransmitters appear to be involved in non-photic entrainment, and which one is necessary
NPY (necessary) and 5HT
In hamsters, stress activates cells in the _____, which project to the ____, which inhibits _____, preventing the activation that is needed to _____
- Dorsal raphe
- IGL
- NPY neurons in the IGL
- Release NPY into the SCN to induce a phase shift
The photic PRC can be reproduced using ______
Injections of glutamate into the SCN
The PRC in rats to melatonin causes a phase _____ near _____
- Advance
- CT12
The PRC to physical restraint is _____
The mirror image to melatonin
