Topic E

Stimulus and Response

Stimuli

• Stimulus- A distinguishable change in the internal or external environment

• Response- The reaction to a stimulus• Reflex- An innate behavior or reaction to a

stimulus– A rapid unconscious autonomic response

Responses to Stimuli

Receptors

• Sensory receptors– Nerve ending that responds to a stimulus (internal

or external)– Initiates sensory transduction

• By ACTION POTENTIALS

Neurons• Sensory Neurons

– Converts external stimuli of the environment into internal stimuli

• E.g. vision, touch, hearing…

• Relay Neurons– INTERNEURON ( part of CNS Central Nervous System)– Usually between sensory and motor– Can link up to the brain for controlled varied response

• Motor– Neuron that triggers physical response– By neurotransmitter

Synapses

• Special junctions used by neurons to pass signal molecules on to other neurons or receptor cells, such as muscles

• Allow neurons to form circuits from the CNS

Effector

• Effector cell- muscle, gland, or cell, capable of responding to a stimulus– At terminal end of an efferent neuron or motor

neuron• Effector molecule

– Small regulatory molecule that binds to a protein, altering its activity

Reflexes

• Involuntary, fast, reaction to a stimulus

Pain Withdrawal Reflex

• Involuntary reaction to pain– Body can be trained to over-ride reflex– Unconscious, drugged, or drunk bodies will not

exhibit reflex

Knee Jerk Reflex

Example

• The bird Sylvia atricapilla (blackcap) breeds during the summer in Germany

• 10% of blackcaps now migrate to the UK instead• eggs were collected from parents who had migrated

to the UK in the previous winter and from parents who had migrated to Spain

• Birds whose parents had migrated to the UK tended to fly west, wherever they had been reared, and birds whose parents had migrated to Spain tended to fly south- west.

• Behavior is what an animal does and how it does it.

What is Behavior?

Behavior

• Innate– Independent from

environment

• Learned• Develops as a

result of experience

1. Kinesis: "change the speed of random movement in response to environmental stimulus“

2. Taxis: "a directed movement toward or away from a stimulus; positive and negative taxes

3. Reflex: "movement of a body part in response to stimulus".4. Fixed Action Pattern (FAP): "stereotyped and often complex

series of movements, responses to a specific stimulus", hardwired, however, not purely genetic, may improve with experiencea. programmed response to a stimulusb. stimulus of FAP = "releaser", sometimes called "sign

stimulus“c. examples:

- courtship behavior- rhythms - daily (circadian); annual (circannual)

Learning - Learned Behavior: Five Categories

A. Imprinting

1. a strong association learned during a specific developmental period

a. "sensitive period" or "critical period"b. imprinting of baby geese on mother - Lorenz

baby geese imprint on mother within hours of hatchingwill imprint on any object during that period

2. learning a releaser for an innate FAP

B. Habituation

1. decline in response to a harmless, repeated stimulus

filter - prevents animal from wasting energy/attention on irrelevant stimuliadaptive

C. Conditioning - laboratory setting

1. classical conditioning animals make associations - Pavlov's dog associates bell with food, begins to salivate, can be extinguished and later followed by recovery (unconditioned stimulus - meat, unconditioned response - salivation, conditioned stimulus - bell, conditioned response - salivation)

a. animal learns to perform an "old" response to a new stimulus

b. Pavlov's dog- place dried meat powder in dog mouth - salivation- associate with bell - salivation to bell

c. Stimulus first, behavior second (but of course there is an expectation of reward second)

2. operant conditioning a. perform behavior to receive reward or avoid punishment b. Skinner Box - levers, reward - self training elaborate protocolsc. behavior first, reward second (but of course there is a stimulus, if only a thought of reward)

Innate Behaviors – inherited, instinctiveA. programmed by genes; B. highly stereotyped (similar each time in many individuals)C. Four Categories

1. Kinesis2. Taxis3. Reflex4. Fixed Action Pattern

D. Trial and Error Learning - nature setting

1. natural operant conditioning2. modify responses to specific stimuli (releasers) - making both more adaptive3. modify releaser to specific FAP - making both more adaptive

Observational learning - social imitation

E. Insight, reasoning

1. manipulating concepts in the mind to arrive at adaptive behavior

2. mental trial-and-error

3. internal memory stores are used as additional sensory/information source

All examples of tool-using:

• chickadees/tits and opening milk bottles

• Egyptian Vulture - uses rocks

• Cocos Finch - uses splinters of wood

• North American Gulls, Northwestern Crow - smash clams on sandy beaches

• Cognition is the ability of an animal’s nervous system to perceive, store, process, anduse information gatheredby sensory receptors.

The study of cognition connects nervous system function with behavior

• Kinesis and taxis.– These are the simplest mechanisms of

movement.• Kinesis is a change in activity rate in response to

a stimulus.– For example, sowbugs are more active in dry areas and less

active in humid areas.

• Taxis is an automatic, oriented movement to or away from a stimulus.– For example, phototaxis, chemotaxis, and geotaxis.

Animals use various cognitive mecha- nisms during movement through space

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Taxis and Kinesis lecture

• http://www.youtube.com/watch?v=nzT9F6knDVs

• Responses to stimuli• Taxis is directional to or away• Kinesis is random movement

How Learning Improves Survival

• Can prevent an animal from repeating dangerous behaviours

• Example:– Fox/wolf attempts to eat a porcupine– Gets pricked or poked– No longer attempts to eat porcupine

• Songbird repertoiresprovide us withexamples.– Why has natural

selection favoreda multi-songbehavior?

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 51.5

• It may be advantageous for males attracting females.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 51.6

Medulla Oblongata

• controls automatic and homeostatic activities, such as swallowing, digestion and vomiting, and breathing and heart activity.

Cerebellum:

• coordinates unconscious functions, such as movement and balance.

Hypothalamus:

• maintains homeostasis• coordinates the nervous and endocrine

systems, secreting hormones of the posterior pituitary, and releasing factors regulating the anterior pituitary.

Pituitary gland:

• the posterior lobe stores and releases hormones produced by the hypothalamus and the anterior lobe, and produces and secretes hormones regulating many body functions.

Cerebral hemispheres

• act as the integrating centre for high complex functions such as learning, memory and emotions.

Animal Experimentation

• On Brain Growth and Behavior– Rats placed on turntable had more mature brain

cells in the vestibular area of the brain– Rats placed in a more stimulating environment

had a larger cerebral cortex• Also more “spines” which mostly serve as receivers in

synaptic contacts

Sympathetic Control

• Sympathetic- Autonomic– Responsible for organs and glands (functioning

unconsciously) • Responsible for flight or fight response and

homeostasis• Used for actions requiring a quick/immediate

response

Parasympathetic control

• responsible for stimulation of activities that occur when the body is at rest, including sexual arousal, salivation, lacrimation (tears), urination, digestion, and defection (pooping)– SLUDD

• Branches from the Autonomic system• Functions in actions not requiring an

immediate response

Pupil Reflex

• Controls the diameter of the iris when exposed to light

• Light stimulates photosensitive ganglion cell• Synapses with the oculomotor nerve, which

controls the muscle that constricts the pupil

Detecting brain death/damage

• Under normal conditions, the pupils of both eyes respond identically to a light stimulus, regardless of which eye is being stimulated

• a direct response in the right pupil without a consensual response in the left pupil suggests a problem with the motor connection to the left pupil

• Brain death is when a portion of the brain is no longer functional

Pain

Endorphins

• Prevent nerve cells from releasing more pain signals