Lecture 15 Seasonal Responses

Question 1

How is seasonal responses determined

Answer 1

Photoperiodism- changes in daylight and night length

Question 2

Critical Day length

Answer 2

Long day plants hrs>CDL

Question 3

Models for day length perception

Answer 3

External coincidence- light senstive molecule accumalation coincides with light
Intenral Coincidence- daylight length brings circadian rythms in synchrony,

Question 4

How is seasonal reproduction/development percieved

Answer 4

light-SCN-Pineal gland

Question 5

how melatonin regulates reproductiojn

Answer 5

Metlationin- produced at night
Long days- Wide peak- reproduction in smaler mammals
Short days- Small peak-

Question 6

how does melatonin work?

Answer 6

targets mediobasal hypothalmus- to produce GnRH which acts on piturary
Releases FSH and LH- stimulated testosterone and sperm production in males
stimulates start of mentstruation cycle in females(and release of progesterone and estradiol

Question 7

how does melatonin Work 2

Answer 7

Acts on Pituary gland to release thyroid stimulating hormone which converts prohormone thyroxine to T3 active form
T3 regulated release of GnRH