Hormones I Flashcards
Organization of behavior, circadian rhythms (17 cards)
What in the body direct organizing of behavior? What is it aided by?
- CNS
- Hormones
How do insect central nervous systems organize behavior? What is an example? Elaborate. How does the brain then coordinate movement and what are the cells called that do this? What happens if you sever the protocerebral ganglia?
- Inhibitory signals –> neural command centers
- Preying mantis - muscles controlled by ganglia within the segments themselves (in other words, local ganglia have the circuitry for movement in one segment without any higher level of neural input (just need the on/off signal))
- Inhibits local ganglia until they are needed for their encoded functions (inhibits with protocerebral ganglia)
- No inhibition –> multiple mutually exclusive events at once (such as walking and grasping with forelegs)
What part of the body organizes behavior and what is it aided by?
- CNS, hormones
How do insect central nervous systems organize behavior? What is an example? Elaborate. What happens when you cut connections between segments and what does this mean? What happens when you cut connections between protocerebral ganglia and segments and what does this mean?
- Inhibitory signals –> neural command centers
- Preying mantis - muscles are controlled by a series of ganglia in the segments
- When stimulated, they perform the movements relevant for those muscles, means that local ganglia have circuitry necessary for movement without higher input
- Walk and grasp simultaneously, meaning that inhibitory function gone and muscles perform actions at the same time
Under what conditions is the protocerebral ganglion not always necessary in the preying mantis?
When copulating, if female takes off males head, the body can still make rotary movements and twist to continue going
What is another insect example of how the brain organizes behavior (not preying mantis)? Under what conditions is this shown? What happens in the body of the organism?
- Crickets (which call with their wings)
- Blowing a puff of air on the cricket
- puff –> inhibition of calling circuits –> start again after inhibition released (when no air movement is detected)
Why are circadian rhythms relevant? What is an example? Explain. What was an experiment done on monarchs to test the importance of circadian rhythms?
- Majority of behaviors are relevant for only a certain time of day
- Use of sun compass requires a clock (travelling towards the sun may take you SW or SE depending on time of day)
- Reared in the lab, then brought outside and they travelled consistent with their perception on the time of day
What is a free-running cycle? What is an example? What happens to this example if you add a night cue? What is this type of cycle called?
- A circadian rhythm without any cues, so it’s just running based on its own approximation of time (typically slightly longer or shorter than one day)
- Crickets raised without any day/night cues –> calling behavior (alleles determine if it runs long or short)
- Crickets will call two hours before the lights turn off
- Entrained
If cycles can be entrained to match relevant environmental conditions, why should the crickets evolve the circadian rhythm that has to be overridden every day by environmental signals (3 reasons)?
- There is no cue to sing 2hrs before lights out, only an internal clock lets them sing on time
- Noisy cues (weather can obscure light cues)
- Cues can change (day length can vary with season and definitely at the poles)
What happens if there is no selective advantage for daily rhythms? What is an example? Elaborate.
- Rhythm is lost
- Sand crickets - some fly, some don’t. Ones that do need a signal because flight is dangerous during the day (monitored by juvenile hormone). Ones that don’t fly don’t have a cycle.
Under what conditions is a circadian rhythm formed? What are two examples of species where circadian rhythms are not found, and why?
- Environments change
- Nurse bees (never go outside the hive) and naked mole rats (never go outside the dirt colony)
What is the master clock? What causes jet lag? Where is the master clock in crickets and where does entrainment occur?
- Master clock synchronizes all of the other clocks in your body
- Asynchrony between the different clocks in your body (one for your heart, stomach, intestines, kidneys, etc)
- Optic lobe and entrained by input from eyes
Think about the cricket master clock. What happens if you sever input from the eyes into the optic lobe? Sever between optic lobe and rest of brain?
- Rhythm is free-running (no longer entrained)
- Calling cycle breaks down (no synchronization of daily clocks)
Where is the master clock located in vertebrates? From where does it receive input? What does this input control?
- Hypothalamus - specifically suprachiasmatic nucleus (SCN)
- Photosensitive ganglion cells in eyes (use melanopsin as photopigment, not rods and cones) (sluggish for entrainment)
- Release of melatonin, strong blue light images
What are the genes that create the feedback loop for the circadian rhythm (2)? Explain their roles.
Clock and BMAL1 make PER and CRY that inhibit Clock and BMAL1
What can mutations in PER cause in the clock?
- Increase cycle length (slowing down PER degradation)
- Decrease cycle length (speed up degradation)
- Eliminate cycle (disrupting all PER dynamics)
What are possibilities for signals that regulate the other clocks from the master clock (2)? Which one is more likely? Elaborate on it. What happens if you inject rats with PK2 at night?
- Melatonin, PK2 (made in SCN)
- PK2 - pattern changes throughout the day, produced in normal light conditions or for 2-8 days in complete darkness
- Their cycle changes to a point where they are active during the day and asleep at night
