14.Response To Stimuli Flashcards
What is phototropism
Directional movement to unilateral light, shoot tip bends towards light due to IAA moving moving to the shaded side of the shoot top, cells on shaded side elongate faster than those on light side, so top bends towards light
What is gravitrophism
Directional to gravity, root tip bends downwards due to IAA moving to lower side, IAA inhibits the cells elongation so those on top side elongate faster and so tip bends downwards
What is IAA
Auxin - hormone produced by frowning shoot and root tips
What were Darwin’s experiments
Normal plant shoot
Shoot tip removed
Lightproof cover on tip
What was boysens-jensons experiments
Thin impermeable mica inserted in sunny side of tip - tip bends same away and hormone can pass down to shaded side
Mica inserted on shaded side-tip doesn’t bend as movement of IAA prevented down shaded side
Tip removed and gelatin block placed between-gelatin allowed movement of chemicals to pass through it, bending must be due to chemical passing from tip
What was Paals experiment
Removed tip and placed to one side of shoot-shoots bend towards the side where no tip is present
What was Briggs experiment
Put shoot in darkness
Thin glass plate between two sides of shoot-amount or IAA is same on either side of plate as chemical can’t move across
Glass plate half way up shoot, not through tip-shoot bends towards light as chemical can move to shaded side
What is a stimulus
Detectable change in the internal or external environment of an organism that leads to a response in the organism
What are receptors
Specific to one type of stimulus
What’s an effector
What produced the response
What’s the sequence of nervous system
Stimulus Receptor Sensory Coordinator Motor Effector Response
What’s a taxis
Simple response whose direction is determined by the direction of stimulus as result motile organism response directly to environs changes by moving whole body either towards favourable stimulus or away from unfavourable one.
What’s a kineses
Form of response in which organism doesn’t move towards or away from stimulus, changes speed at which it moves and rate at which it changes direction
If organism crosses from favourable to unfavourable area it’s turning rate increases
What’s a tropism
Growth part of a plant in response to directional stimulus.
Shoot tips positive phototropism
Root tips positive gravitropism
What are the external stimulus plants respond to
Light - need for photosynthesis
Gravity - need to be firmly anchored
Water - to absorb for support, metabolic processes and photosynthesis
What’s an example of a plant growth factor
IAA - indolescetic acid
Type of auxin
What does IAA do to shoot tips
IAA moves to shaded side of shoot
Greater conc of IAA builds up on shaded side than light side
IAA causes elongation of shoot cells and as there’s greater concern on shaded side, shaded side cells elongate more
Shaded side of shoot elongates faster than light side causing it to bend towards light
What does IAA do to root tips
Gravity influences IAA to build up on lower side of tip
Greater conc on lower side
IAA inhibits elongation of root cells
Greater conc on lower side, cells elongate less than those on top side of root
Causing root to bend downwards towards force of gravity
What are the major divisions of the nervous system
Central nervous system - brain spinal chord
Peripheral nervous system - pairs of nerves originate from brain or spinal chord
What is the peripheral nervous system split into
Sensory neurones-impulse from receptor to cns
Motor neurones-impulse away from cns to effectors
What’s the further split of the motor neurone nervous systems
Voluntary- nerve impulse to body muscles and under conscious control
Autonomic-nerve impulses to glands,smooth muscle and cardiac muscle under unconscious control
What’s the spinal chord made of
Column of nervous tissue run alongside back and lies inside vertebral column for protection
Emerging at intervals along spinal chord are pairs of nerves
What’s the steps of a reflex arc
Stimulus Receptor Sensory neurone Coordinate/intermediate Motor Effector Response
What is a reflex arc
Rapid short lived response that’s localised and involuntary
Whata the importance of reflex arcs
- involuntary, don’t require decision making powers of brain-leaving it free to carry out more complex responses-brain not overloaded-some go to brain to be overridden if needed
- protect body from harm- not learnt
- fast- neurone pathway short and don’t have lots of synapses which slow transmission
- absence of decisions means action rapid
What does a pacinian corpuscle detect
Changes in mechanical pressure
What does a pacinian corpuscle do
Response to mechanical pressure and produces a generator potential by acting’s as a transducer
What is a generator potential
Receptors convert energy of stimulus into nervous impulse
What’s the structure of pacinian corpuscle
Sensory Neurone that ends in layers of connective tissue that has viscous gel between
Sensory neurone ending has special type of sodium channels in its plasma membrane-stretch mediated sodium channels.
How does the Pacinian corpuscle function
- in resting state stretch mediated challenge too narrow to allow sodium ions to diffuse through, has resting potential
- when pressure applied to pacinian corpuscle, it’s deformed and membrane and neurone becomes stretched
- widens sodium channels and na+ diffuse into neurone
- influx of sodium ions changes membrane potential and it becomes depolarised producing generator potential
- generator potential creates action potential and that propagates along neurone
What are the two types of receptors in a mammalian eye
Rod and cones
Difference between cone cells and rod cells
Rod shaped / cone shaped
More / less
More at periphery / concentrated at fovea
Poor visual acuity / give visual acuity
Sensitive to low intensity / not sensitive to low intensity
One type / three types for different wavelength
How does a rod cell act as a transducer
Conserve light energy into the electrical energy of a nerve impulse
Pigments in rod cell must be broken by light in order for this to happe
What’s a cone cells job in the eye
- Contain different pigment which requires higher intensity light to break it down and create generator potential
- each cone cell specific range of wavelengths
- each has own connection to bipolar cells so if two adjacent cone cells stimulated brain receives two impulses, two dots can be resolved
What’s the distribution of rod n cone cells
Uneven
- Light focused by lens on part part of retina opposite pupil-fovea
- fovea receives highest internist, cone cells found at fovea
- conc of cone cells diminish further away from fovea
- at peripheries of retina only rod cells found
What’s the importance of having different light receptors
Both respond to different stimuli
Mammals benefit form good all round vision day n night
Why are the types of autonomic nervous systems
Sympathetic-stimulates effectors, speed up activity (heightens awareness - fight or flight)
Parasympathetic-inhibits effectors and slow down activity, controls under normal resting conditions, conserve energy
How in heart rate controlled
- wave of electrical excitation spread out from sinoatrial node across both atria-contract
- layer of non/conductive tissue prevents wave crossing to ventricles
- wave of excitation enters atrioventricular node
- atrioventricular node after short delay conveys wave of excitation along bundle of his to purkyne tissue fibres
- bundle of his conducts wave through atrioventricular septum to base of ventricles
- wave of electrical excitation released and moved up from base, ventricles contract from bottom upwards simultaneously
How is heart rate modified
- Medulla oblongata
- sympathetic nervous system which increases HR which is linked to sinoatrial node
- parasympathetic nervous system which decreased heart rate which linked to sinoatrial node
How do chemoreceptors control heart rate
- found in wall or carotid arteries
- when blood has higher conc of carbon dioxide, pH lowers
- chemoreceptors detect this and increase frequency of impulse to medulla oblongata
- increases frequency of impulses via sympathetic system to sinoatrial node, increasing procession of electrical waves and therefore increase HR
- increases blood flow leads to more carbon dioxide being removed by lungs
- pH roses to normal and chemoreceptors reduce their frequency of nerve impulses to medulla oblongata
- therefore medulla oblongata reduces frequency of impulses to sinoatrial node and leads to recursion in HR
How is heart rate controlled by pressure receptors
-when blood pressure higher, pressure receptions transmit more nervous impulses to centre in medulla oblongata that decreased HR, centre sends impulses via parasympathetic system to sinoatrial node which leads to decrease in rate of heart beat
Why is the pigment in cone cells
iodopsin
