The Pain Reflex The pain withdrawal reflex is a rapid, unconscious response to danger or injury. It is mediated by the spine’s grey matter.

Reflex animation from: http://www.bbc.co.uk/schools/gcsebitesize/science/add_ocr_pre_2011/brain_mind/reflexactionsrev1.shtml

A very basic overview from the BBC:

The Pain Reflex The pain withdrawal reflex is a rapid, unconscious response to danger or injury. It is mediated by the spine’s grey matter.

(nociceptors)

The Pain Reflex The pain withdrawal reflex is a rapid, unconscious response to danger or injury. It is mediated by the spine’s grey matter.

Injury stimulates pain receptors (nociceptors), causing Ca2+ ions to rush in. This depolarises the sensory neuron and starts an action potential.

(nociceptors)

propagates the AP along theaxon (review action and resting potentials!)

The Pain Reflex The pain withdrawal reflex is a rapid, unconscious response to danger or injury. It is mediated by the spine’s grey matter.

Relay neurons (interneurons in the animation above) are in the grey matter of the spine. They receive the signal from the sensory neuron, through synaptic transmission (review it!) and coordinate the response to pain:

• An excitatory neurotransmitter (e.g. ACh) is sent across the next synapse to the motor neuron for muscles to contract.

• An inhibitory NT is used to send a signal to antagonistic (opposite) muscles to relax.

Spine-mediated pain reflex arc, from: http://en.wikibooks.org/wiki/Anatomy_and_Physiology_of_Animals/Nervous_System

The Pain Reflex The pain withdrawal reflex is a rapid, unconscious response to danger or injury. It is mediated by the spine’s grey matter.

(nociceptors)

Finally, the motor neurons conduct the AP from the relay neuron to the effector (muscle). • Muscles that need to contract

receive and excitatory signal. • Muscles that need to relax

receive an inhibitory signal.

The response is rapid movement away from the source of pain.

http://kickyoutube.com/watch/?v=vUNZv-ByPkU

The common birds are found in gardens throughout most of Europe. They have a specific mating schedule linked both to warm temperatures and to the presence of caterpillars, which great tits feed to their young.

Warming temperatures are making caterpillars arrive earlier. Birds that laid eggs on their typical schedule would have a difficult time raising their young as Caterpillars would not be as plentiful when the eggs finally hatched a few weeks later.

The Wytham population moved its egg-laying schedule forward 14 days to synchronize with the earlier caterpillar activity—without a lot of chick deaths.

Rapid evolution of Malawai cichlids

Cichlid fish are famed for their rapid evolution, particularly in the African Great Lakes, where over a thousand new species have evolved over the last 12,400 to 100,000 years. The members of the cichlid family have diverse diets, mating habits and methods of looking after their young.