6.1 Stimuli Flashcards
Stimulus definition
A detectable change in the internal or external environment of an organism
How is the peripheral nervous system divided?
Autonomic (parasympathetic, sympathetic) + Somatic
Taxes definition
Directional movement response to a directional stimulus
Kineses definition
Non-directional movement response to a stimulus
Auxin definition
Growth factors in plants
Where does IAA accumulate in plants?
Gravity in roots - underside
Light degrades in shoots - Non lighted side
Where is IAA produced?
Tips of shoots
Reflex definition
Rapid, automatic response to a stimulus
Describe the structure of a Pacinian corpuscle
End of a sensory neuron (sensory nerve ending)
Wrapped in layers of connective tissue (lamellae)
Describe the action of a Pacinian corpuscle
When pressure applied lamellae deform and press on sensory nerve ending
This stretches the membrane
Deforms stretch-mediated Na+ channels
What do photoreceptors do?
Convert light stimuli into an electrical impulse
What are the types of photoreceptors?
Rods - Black and white monochromatic
Cones - RGB trichromatic
How do photoreceptors work?
1) Light enters eye and hits photoreceptors
2) Light-sensitive optical pigment absorbs light
3) Light bleaches pigment - chemical change - ^ membrane solubility of Na+
4) Bipolar neurones connect photoreceptor to optic nerve which takes an impulse to brain
Why are rods very light sensitive?
Multiple rods attached to one bipolar neruon ∴ many weaker generator potentials combine and can reach a threshold (spatial summation)
Why do cones have high visual acuity?
One cone attached to one bipolar neuron and are close together
Light from two points hits two different cones, two different action potentials generated and given
Sent to brain as two separate points
