The physiological basis of behaviour

Question 1

What is an Endogenous Clock?

Answer 1

A biological timing mechanism with a built in schedule
Acts independently of cues in surroundings
Allows priorities to change over time

Question 2

What is an Environmental Stimulus?

Answer 2

Feedback from surroundings to change priorities

Question 3

What were the two hypothesis about crickets calling at the same time each day?

Answer 3

1) Cricket has an internal timer which can determine duration since last bout of calling
2) Nervous system set to initiate calling when light levels fall below a certain level

Question 4

How were the two hypothesis about crickets calling at the same time each day tested?

Answer 4

1) Crickets kept under fixed light and temperature conditions for a number of days
2) Crickets kept under 12/12hr light/dark cycle

Question 5

What was the conclusion about male cricket calling?

Answer 5

Environment independent endogenous clock, if they are removed from the usual light dark cycle they still call but it isn’t set at 24 hours
The environmental stimulus synchronizes endogenous clock with local conditions

Question 6

Describe environment independent behavioural cycle in mice.

Answer 6

Mice are nocturnal, odour cues are incredibly important for communication and avoiding location of predators. Olfactory bulb exhibits cyclical changes, mice are more sensitive to odours at night

Question 7

What is melatonin?

Answer 7

It is a mammalian hormone that is secreted by the pineal gland
It is produced at night, modulates circadian timings, modulates sleep
Seasonal changes influence secretion and can interact with other reproductive hormones to influence breeding

Question 8

How is melatonin production modulated?

Answer 8

Melatonin production is also modulated by external stimuli
If it is dark, photoreceptors in the eye are stimulated and this helps modulate the internal clock and more melatonin is produced
However if there is constant daylight or lots of artificial light, this inhibits production

Question 9

Name 3 organisms lacking circadian rhythm.

Answer 9

Naked mole rats: Live underground, almost never surface
Nurse honey bees: Never leave hive, brain lacks gene expression associated with bee circadian clock
Forager honey bees: Collect pollen during the day brain exhibits signs of gene activity linked to circadian clock

Question 10

Why is circannual rythm difficult to study?

Answer 10

2 year minimum period

Question 11

Name 5 predictable environmental cues.

Answer 11

Tidal cycles
Lunar cycles
Change in day length
Sunrise / Sunset

Question 12

What organism responds to the environmental cue, Tidal cycles?

Answer 12

Atlantic marsh fiddler crabs

• Plug burrows with mud HIGH
• Forage / look for mates LOW

Question 13

What organism responds to the environmental cue, Onset of rainy season?

Answer 13

European Stonechats

• Abundance insects
• Mating so nestlings have sufficient food

Question 14

What organism responds to the environmental cue, Sunrise / Sunset?

Answer 14

Crickets

Males call to locate mate

Question 15

What organism responds to the environmental cue, Change in day length?

Answer 15

Junco

*migration

Question 16

What organism responds to the environmental cue, Lunar cycles?

Answer 16

Banner tail kangaroo rat

• More likely to stay underground with increased moonlight
• Aid to predators

Question 17

Who studied seasonal changes in behaviour of European stonechats?

Answer 17

Holt et al 2009

Question 18

What were the findings of Holt et al’s 2009 study on European stonechats?

Answer 18

This annual cycle was still present even with no wild external stimuli
However after a period of time it became out of sync with wild counterparts (shortening)

Question 19

Describe Holt et al’s 2009 study on European stonechats?

Answer 19

European stonechats were taken from Kenya and moved to a lab in Germany
These birds were really young so had no experience of the spring/rainy season
The Stonechats were held in constant temperature & light conditions in the lab

Question 20

Why is the rainy season an important cue for European stonechats?

Answer 20

When food is most abundant, the birds must reproduce.

Immediately prior to breeding the testicular width of these birds increases

Question 21

Who studied social conditions in mice?

Answer 21

Mak et al 2007

Question 22

What did Mak et al 2007 find?

Answer 22

Prior exposure to a subordinate: female spends equal time sniffing sub and dom male
Prior exposure to a dominant: increased time near the dominant
Exposure to dominant scent promotes neuronal growth to allow identification of dominant male should one be there

Question 23

What are hormonal mechanisms?

Answer 23

Hormones play a key role in linking environmental information with rapid changes in behaviour.
Hormones, during development, can alter the nervous system & change physiology & behaviour.

Question 24

Describe hormones and mouse infanticide.

Answer 24

Switch from infanticidal to paternal in 3 weeks
Endogenous clock – number of days since last copulation
Number of light: Dark cycles controlled infanticidal behaviour
Physiological mediator that links change in daylight to change in aggression:
Hormone
Immediate but temporary effect
A) testosterone – linked with male aggression
B) Progesterone – suppresses parental behaviour in female rodents
KO mice produces lacking progesterone receptors
*KO – never attacked pups
*WT - >50% attacked
NSD in levels of circulating testosterone or progesterone in groups

Question 25

Who studied hormones and mouse infanticide?

Answer 25

Schneider et al 2003