BIOLOGICAL RHYTHMS

Question 1

What is a rhythm

Answer 1

Function which oscillate cycles at a regular frequency

Question 2

What is a circadian rhythm

Answer 2

A daily rhythmical change in behaviour or in a physiological process (24 hour period )

Question 3

What is chronobiology

Answer 3

A field of science that examines biological rhythms

Question 4

What is infradian rhythm

Answer 4

Rhythm with a period longer than the period of a circadian rhythm, frequency less than 1 cycle per 28 hours e.g. reproduction

Question 5

What is an ultradian rhythm

Answer 5

Refers to rhythm s with periods shorter than the period of a circadian rhythm
E.g. cycle in sleep or REM (rapid eye movement)

Question 6

Function of rhythm: what is external synchronisation

Answer 6

Clocks are internal physical system
Allows organisms to live in harmony with the environment
E.g. night and day or seasonal changes

Question 7

Function of biological rhythms: what is internal synchronisation

Answer 7

Circadian rhythms maintain temporal organisation of endogenous processes

Question 8

What is zeitgeber

Answer 8

Means time giver
Is any external cue that entertains the internal time keeping system or organisms
E.g strongest zeitgeber in plants is light

Question 9

What are the features of the retina in terms of biological rhythms

Answer 9

• no need for cones or rods
  Melanopsin containing ganglion cells in the retina transmit information to the SCN, thalamus and the olivary pretectal nucleus

Question 10

What are the features of the suprachiasmatic nucleus (SCN) in terms of biological rhythms

Answer 10

A nucleus found on top of the optic chiasm

Contains a biological clock that is responsible for organising many of the body’s circadian rhythms

Question 11

What are the features of the pineal gland in terms of biological rhythms

Answer 11

Gland attached to the dorsal tectum

Produces melatonin and plays a role inc circadian and seasonal rhythms

Question 12

What are the functions of melatonin

Answer 12

-more melatonin produced when dark, induces sleep
Represses reproduction in long day breeders (e.g. horse, fox ,ferret (SPRING)
Stimulates reproduction in short day breeders (e.g. sheep, goat (AUTUMN)

Question 13

Describe the physiological basis of biological rhythms

Answer 13

• light enters eye
• the information (light/dark ) is transferred from the retina to the SCN (biological clock )
• The SCN sends neuronal signals to the pineal gland to secrete melatonin( high in dark). Melatonin also appears to be involved in synchronising circadian rhythms

Question 14

What are some seasonal infradian rhythms

Answer 14

Polyoestrus
Season polyoestrus (long day and short day)
Monooestrus

Question 15

What are the functions of biological rhythms

Answer 15

External and internal synchronisation

Question 16

Where are th ebiological clocks

Answer 16

Retina
Suprachiamatic nucleus
pineal gland

Question 17

How is the retina a biological clock

Answer 17

A photopigment present in ganglion cells in the retina whose axons transmit information to the SCN, the thalamus and the olivary pretectal nucleus. Melanopsin containing ganglion cells in the retina

Question 18

How is the suprachiasmatic nucleus part of the biological clock

Answer 18

Nucleus on top of the optic chiasm. Contains a biological clock that is responsible for organising many of the body’s circadian rhythms with the environment via a zeitgeber

Question 19

How is the pineal gland part of a biological clock

Answer 19

Attached to the dorsal tectum, produces melatonin and plays a role in circadian and seasonal

Question 20

How does melatonin work

Answer 20

More melatonin whenit is dark to induce sleep. It also reresses reproduction in long day breeders and stimulates reproduction in short day breeders

Question 21

How do the biological clocks work together

Answer 21

Light enters the eye, information is transferred from the retina to the SCN and the SCN sends neuronal signals to the pineal gland to secrete melatonin which is involved in synchronizing circadian rhythms

Question 22

What is the biological clock in the SCN responsible for

Answer 22

Entrained to solar time by retinal afferents, primary pacemaker of the SCN, synchronises tissue based clocks in the major organ systems by a blend of endocrine, autonomic and behavioural cues. Entrains the peripheral clocks of many organs. It is the principle circadian mechanism

Question 23

How can we understand how genes regulate behaviour

Answer 23

Characterisation of the genes encoding the feedback loop of the clock and how they and their protein products respond to synchronising clues

Question 24

What is the precursor of melatonin

Answer 24

Seratonin

Question 25

Why are biological clocks important

Answer 25

Desynchronisation can lead to the development of diseases