L10 - Neurons & Hormones 1

When conflicting signals are given how do animals determine what they should do?

Not simply stimulus → response

1. Temporal organization

2. Prioritization

Specific behaviours are controlled by specific circuits. Why is “cross talk“ important?

To organize and coordinate different circuits

• especially with incompatible stimuli

How do command centers often exert control to express a certain behaviour?

Control by inhibiting a circuit until it is appropriate

• a subconscious breakpad

What are the 2 types of synapses?

1. Excitatory

2. Inhibitory

What is Tonic Inhibition?

Baseline “stop signal“

What organism has inhibitory control (used as an example in lecture)

Praying mantis

What is the protocerebral ganglion?

The brain of a praying mantis

Does the Protocerebral ganglion excite or inhibit grasping signals?

inhibits signals

What is the subesophageal ganglion?

a part of the body that promotes grasping

Does the subesophageal ganglion excite or inhibit grasping signals?

excite

What happens if you isolate the Protocerebral ganglion from the rest of the rest of the nervous system/subesophageal ganglion?

The mantis walks and grasps simultaneously

When a female eats the head of the male during mating what happens?

Elicits sexual behaviour (male body)

What are heliotrophic plants?

A plant that have leaves which open and close daily

how do you determine internal or external rhythm?

• internal = pattern is maintained without external stimulus (i.e. sun)

• external = pattern is lost without external stimulus

what is a free-running cycle?

an internal rhythm that appears without stimulus

what is an entrained cycle?

when an internal rhythm is synchronized with an external stimulus

what is a cricket’s free-running cycle?

about 26 hours

what is a cricket’s entrained cycle?

exactly 24 hours (matching daylight hours)

what happens when you cut retina lobe connection of a cricket?

The cricket maintains it’s free-running cycle (26 hours)

what happens when you cut the optic lobe connection in crickets?

the crickets become arrhythmic (no circadian rhythm)

→ optic lobe is the pacemaker (clock mechanism) in crickets

What does the SCN stand for?

Suprachiasmatic Nucleus

Where is the SCN located?

Is a region in the hypothalamus within the brain

What effect does light have on the SCN?

Light induces neural activity and gene expression in the SCN

What effect do small electrolytic lesions of adult SCN do?

Lesions of SCN eliminate circadian rhythms

Can a circadian rhythm be restored? How or why not?

Circadian rhythms can be restored through a SCN transplant

What are the 2 ways to measure circadian rhythms in Drosophila?

1. Eclosion Assay

2. Activity assay

What are eclosion assays? How do they help measure circadian rhythms in Drosophila?

Eclosion assays = used to measure the timing of adult insect emergence (eclosion) from their pupal cases