Endogenous

Question 1

Biological Clocks

Answer 1

Internal timing systems which enable an organism to anticipate changes in environmental cycles and physiologically prepare for that.

Question 2

Endogenous (WHY)

Answer 2

Internal biological clocks
- When changes occur, organism is ready to take advantage of the new conditions.
- Many bio rhythms are linked to cyclical changes in the enviro ( day/night, season, tides)
- Have survival values as all organisms (except primitive ones like bacteria) have some kind of bio clock.

Question 3

Endogenous (HOW)

Answer 3

• Endo rhythms are set by an internal clock located in the SCN of humans/animals/mammals, OPTIC LOBE of insects and PINEAL GLAND of birds.
• they will persist even in the absence of enviro cues.
• Pineal gland synthesised and secretes melatonin.

Question 4

How does it work?

Answer 4

The Suprachiasmatic Nuclei (SCN) is a distinct group of cells found within the HYPOTHALAMUS (relay centre, passes info onto PINEAL GLAND).
- SCN is 1 part of the mechanism where “time is kept”.
-Pineal gland is pea-like structure found behind the hypothalamus in humans. It recives info indirectly and secretes and synthesises melatonin.

Question 5

WHY - Adaptive significance of biological clocks

Answer 5

Can predict change in environment (e.g incoming tide and
so can begin feeding immediately) – allows max feeding
and therefore increase survival and repro success

Animals can predict winter – so moult summer hair to
replace with thicker coat for increased insulation. This
increases the animals chance of surviving the winter and
therefore reproducing

Rhythms can be synchronised with other members of the
species facilitating successful mating and thus
reproduction and long term species survival

Question 6

Endogenous Rhythms

Answer 6

• will carry on in the ABSCENCE OF EXTERNAL CUES

Question 7

Free Running

Answer 7

When a pattern continues in the abscence of enviro cues.

Question 8

The Free Running Period of a cycle……

Answer 8

is the length of 1 cycle in the abscence of enviro cues. could be more than 24 hrs ( right ) less than 24hrs (left).

Question 9

Entrainment

Answer 9

Bio rhythm needs to constantly be RESET or ENTRAINED by EXTERNAL/ EXO cues called ZEITGEBER .

Question 10

bio clokcs key words

Answer 10

synchronise, reset, zeitgeber, entrainment, scn, hypothalamus, optic lobe, pineal gland etc……

Question 11

ZEITGEBER

Answer 11

External factor that resets bio clock

Question 12

Flow ideas

Answer 12

human circadian rhythm = 1) retina detects light, 2) sends signal to SCN in HYPOTHALAMUS, 3) sends signal to pineal gland= synthesise melatonin and secretion inhibition.

Question 13

Circadian

Answer 13

Endogenous