6 Responding to Change- Nervous Communication Flashcards
How can organisms increase their chance at survival?
By detecting a change & responding accordingly
Where can organisms detect change in?
-External environments (eg temp of surroundings)
-Internal environments (eg blood glucose conc)
What are the 3 steps in coordinating a response?
-Stimulus; change in environment
-Receptors; detect change in environment
-Effectors; initiate response
How do plants respond to change,why?
-Plants aren’t mobile organisms so can’t move to avoid harmful environments
-They regulate growth in response to direction stimuli, which are called tropisms
What is phototropism?
Growth in response too direction of light:
-Shoots positively phototropic= grow towards light
-Roots negatively phototropic= grow away from light
What is gravitropism?
Growth in response to direction of gravity:
Shoots negatively gravitropic= grow upwards, away from gravitational pull
Roots positively gravitropic= grow downwards, towards gravitational pull
What is Indoleacetic acid (IAA)?
Type of auxin controlling tropic response in plants
How can IAA be transported and what does this result in for its distribution?
-Can be transported over short distances (diffusion/active trans) & longer distances (in phloem) around plant
-This causes an uneven distribution of IAA, and a directional growth occurs
What is the process of a shoot bending towards light?
-Shoots= positively phototropic
-If shoot—> exposed to uneven light source, IAA is transported to more shaded part
-Higher conc of IAA in shaded part—> causes cells in shaded area to elongate
-Cell elongation= shoot bends towards light
What is the process of a shoot bending away from the gravitational pull?
-Shoots= negatively gravitropic
-If shoot—> exposed to uneven gravitational pull, IAA transported to underside (closer to gravity pull)
-High conc of IAA—> cells in underside elongates
-So, shoot bends away from gravitational pull
What is the process of roots bending towards the gravitational pull?
-Roots= positively gravitropic
-If root—> exposed to uneven gravitational pull, IAA= transported to underside (closer to gravity pull)
-Higher conc of IAA in underside—> inhibits cell elongation on lower side
-Root bends towards gravitational pull
What are tactic responses (taxes)? + give example
-Stimulus= positively/negatively directional, like light
Eg- woodlice move away from light source
-Dark environments like under stones= favourable for woodlice for protection from predators
-Ability to detect direction of light + move away helps woodlice locate more favourable habitat
What are kinetic responses (kinases)? + give example
Stimulus= non-directional, like humidity
Eg woodlice move more slowly, turn less in high humidity but opposite in low humidity
-Damp environments= favourable for woodlice, reduce water loss
-Woodlice detect drier environment—> move more, increases chance they’ll find more favourable enviro
-Woodlice detect damper environment—> move less, ensures they stay in more favourable enviro
What are reflex responses and what to they do?
-Automatic, quick, unconscious responses to a stimulus
-Often help organism respond quickly to harmful stimulus like heat
What is a reflex arc and which 3 neurones does it involve?
-Pathway of neurones involved in a reflex response
-3 neurones; sensory, relay and motor
What are the steps involved in a reflex arc?
-Detection; Thermoreceptors in skin detect heat stimulus
-Sensory neurone carries impulse from thermoreceptors to relay neurone in spinal cord
-Relay neurone carries impulse to motor neurone
-Motor neurone carries impulse to effectors (like muscles in arm)
-Response; arm moves away from hot object
What are the 2 features of receptors?
Specificity; receptors only respond to specific stimuli, eg- light, temp, pressure
Generator potential; Receptors connect w/ sensory neurones. When stimulated, the receptor creates a generator potential in sensory neurone, eg. where stimulation of receptor causes generator potential= Pacinian corpuscle
What is the Pacinian Corpuscle and what does it mean consist of?
-A mechanoreceptor found in skin
-These respond to changes in pressure to establish a generator potential
-Consists of concentric rings of connective tissue that surrounds a sensory neurone
What is resting potential and what occurs during it?
When Pacinian corpuscle isn’t stimulated—> at resting state
-Here, charge inside neurone= more negative than outside (-70mV), as there’s more Na+ ions outside neurone than inside
-Difference in charge across cell membrane= potential difference
What occurs when pressure is applied to the Pacinian corpuscle?
When pressure is applied to the Pacinian corpuscle, the rings of connective tissue apply pressure on sensory neurone, which has stretch mediated Na+ channels; normally restrict movements of Na+ ions
Applied pressure—> Na+ channels open
How is the generator potential established?
-Na+ ions flood into sensory neurone through open Na+ channels
-Now, there’s more Na+ ions inside neurone than out
-Charge inside neurone—> more positive than out, so potential difference has been changed
-The generator potential has been established
How is an action potential produced?
If the generator potential reaches threshold level (approx -50mV), an action potential is produced in the sensory neurone
What are rod and cone cells and what do they both do?
2 main (photo)receptors in the human eye
Both respond to photons of light
What are the differences with rod and cone cells?
Rod cells;
-Highly sensitive to light
-Low visual acuity
-Highly numerous
-Evenly distributed on retina, absent in fovea
-Use pigment called rhodopsin, detects light + dark
-Monochromatic; detects only 1 wavelength of light
Cone cells;
-Less sensitive to light
-High visual acuity
-Fewer cells than rod cells
-Distributed mainly at single point in retina (fovea)
-Use pigment called lodopsin, detects colour
-Trichromatic; divided into 3 types, respond to diff wavelengths of light either red, blue or green.
