Nerves and Stimuli

Stimulus – any perturbation in an animal’s internal or external environment which results in changes in membrane physiology of a receptor neuron leading to an action potential

Nerve Cells

axon myelin

Nerve Stimulation Membrane Current

Action Potential

CytosolExtracellular fluid Na + 15 mM K mM Cl mM A mM Na mM K + 5 mM Cl - 10 mM -60 to -70 mV negative

Action Potential Sodium (Na + ) ion Potassium (K + ) ion Sodium channel Potassium channel Activation gate Inactivation gate

Action Potential 3. Depolarization opens most Na + activation channels. Influx of Na + makes inside of cell +ve. 4. Inactivation channels close & block Na + influx. Activation gates on K + channels open & K + ions leave making cell more -ve. 5. Some K + channels are still open, allowing K + ions to escape and making the cell more -ve. As the K + gates close, the cell returns to its resting state. 1. Resting state - activation gates on K + and Na + channels are closed. 2. Stimulus opens activation gates on some Na + channels. Influx of Na + and depolarization.

Synaptic Junctions

Receptors -All receptors are designed for signal transduction (the changing of a signal in one modality (chemical, mechanical, thermal etc.) into an action potential in a nerve

Chemoreceptors Hamster - taste budMoth antenna

Mechano- and chemoreceptors

Thermoreceptors

Photoreceptors Photosensitive cells - Planaria Compound eye - Arthropods

Nerve cells, stimuli and behaviour Tail flip response in crayfish

Lateral Giant interneuron (LGI)

a. Correlation between nerve firing and response LGI Stimulating electrode Recording electrode Tactile stimulation b. LGI is sufficent for response LGI Stimulating electrode Recording electrode Tactile stimulation LGI Stimulating electrode Recording electrode Tactile stimulation c. Hyperpolarizing nerve Tail flip No tail flip

Nerves, Genetics and Behaviour shaker animation Three genes -shaker, hyperkinetic, ether-a-go-go

Nerves, Genetics and Behaviour

Sodium (Na + ) ion Potassium (K + ) ion Sodium channel Potassium channel Activation gate Inactivation gate

Peripheral Processing of Stimuli Worm-catching Toads

Peripheral Processing of Stimuli Worm-catching Toads

Central Processing Optic Tectum of a Toad

Central Filtering – Lesion of the HVc region in Canaries

Number of displays elicited Before lesion After lesion Canary song Sparrow song

Central Pattern Generator Senses CNS interneuron Effector Muscle Motor Pattern Motor impulse Sensory input Peripheral filtering Central filtering

Central Pattern Generators (Motor Pattern Generators)

Cockroach – reflex arc Sensory input Nerve impulse

Nerves and Stimuli 1. Structure of nerves 2. Polarity of a nerve cell 3. Transmission of an action potential 4. Peripheral filters 5. Central filters 6. Motor pattern generators

Moth Ears Noctuid mothArctiid moth

Moth Ears

Bat Hunting Call

Moth Ears

A1A1 A1A1 A2A2 A2A2 A x more sensitive than A 2

Moth Ears 1) Bat approaches from side A 1 left A 1 right

Moth Ears 2) Bat approaches from front -moth moves side-to-side

Moth Ears 3) Bat approaches from above or below From above -ears are covered on downstroke -ears are uncovered on upstroke From below -ears are uncovered on both

STIMULI - AN ETHOLOGICAL PERSPECTIVE

1.Releasing (or triggering) stimuli 2.Orienting stimuli 3.Priming stimuli 4.Sign stimuli CATEGORIES OF STIMULI

Sign stimuli - species specific -release a reaction that is inherited not learned CATEGORIES OF STIMULI

Sign Stimuli 1. European robin Red breast releases aggressive behaviour in males

Herring Gull -chick pecks at parent’s beak to obtain regurgitated food Cues?? Complex Sign Stimuli

Two major cues are involved: 1. Yellow bill2. Red spot on the mandible

Male Stickleback (Gasterosteus) Red Belly Red Belly + Head Down Posture

Innate Releasing Mechanisms SIGN STIMULUS receptorCNS IRM Motor pattern Generated No motor pattern generated Match No match Motor output

Fixed Action Pattern (FAP) Egg Rolling in a Greylag Goose Egg-rolling video

A series of FAP’s can be put into a sequence Female Male 1. Appears -heads up display 2. Zig-zag swim 3. Swims head up to male 4. Swim to nest 5. follows 6. Show nest 7. Enters nest 8. Tremble thrust 9. spawn

In reality:Should look like:

More Fixed Action Patterns Courtship behaviour of the mallard, Anas platyrhynchos

Modal Action Patterns

SUPERNORMAL STIMULI

Oystercatcher

Lorenz’s Hydraulic Model

Vacuum activity Time Court live female Court female model Court rolled up towel Court corner of cage

Displacement activity