Response to stimuli Flashcards
Describe taxes
- Simple response where organism moves it’s entire body towards favorable stimulus/ away from unfavorable
- Towards = positive taxis
- Away = negative taxis
Describe kinesis
- Organism changes speed of movement and rate of changing direction
- If move from beneficial to harmful environment = increases rate of change in direction to return to favorable environment
- If surrounded by negative stimuli rate of turning decreases = moves in a straight line = increase chance of finding new favorable location
What is tropism?
- Plant respond to stimuli via growth
- Positive = towards stimuli
- Negative = away from stimuli
- Stimuli of light + gravity
What is IAA?
- Growth factor
- Made in tips of shoots/roots
- Controls cell elongation in shoots
- Inhibit growth in roots
Describe positive phototropism in shoots
- Shoot tips produce IAA = elongation
- IAA diffuses to other cells
- Unilateral light = IAA diffuses to the shaded side = higher concentration on shaded side
- IAA causes cells on shaded side to elongate = plant bends towards light
Describe negative phototropism in roots
- IAA moves to the side away from light
- High concentration inhibits elongation = elongates on the side towards the light
- Root bends away from light
Describe negative gravitropism in shoots
- IAA will diffuse from the tip downwards to the lower side
- Shoot elongates = grows upwards against gravity
Describe positive gravitropism in roots
- IAA moves to lower side of roots = upper side elongates
- Root bends down towards gravity
What is a stimulus?
Detectable change in the environment
What is a receptor cell?
- Cells that detect specific stimuli
- Stimulation = action potential = response
What is the Pacinian corpuscle?
- Receptor that responds to pressure change
- Located deep in the skin of fingers and feet
- Consists of a sensory neuron + wrapped in layers of tissue with layers of gel in between each layer
Describe how Pacinian corpuscle works
- Cell membrane around sensory neuron has stretch mediated Na+ channel
- Resting state Na+ channel too narrow for diffusion = resting potential maintained
- Pressure applied = deforms membrane + stretches/widens channels = Na+ diffuses in = action potential
2 types of photoreceptors in retina
1) Rod: Distributed around retina but not in fovea
2) Cone: Mainly central fovea
Describe the rod
- Rhodopsin pigment broken by light energy
- Low resolution visual acuity = retinal convergence = many rod cells synapse with 1 bipolar neuron
- Monochromatic vision
- Very sensitive to light intensity due to spatial summation
Describe the cone
- 3 iodopsin pigments broken by light energy
- High resolution visual acuity = no retinol convergence = 1 cone synapse with with 1 bipolar neuron
- Tricolor: Red + blue + green absorbed by 3 different iodopsins
- Less sensitive to light intensity
Path of light from photoreceptor to brain
Photoreceptor - Bipolar neuron - Ganglion cells of optic nerves - Brain
2 nodes involved in heart contractions
1) SAN: In wall of right atrium AKA pacemaker
2) AVN: Lower border of right atrium
Describe how heart beats are coordinated
- SAN initiates wave of depolarization across atria = contraction
- AVN releases another wave of depolarization
- Non-conductive layer between atria/ventricle prevents depolarization from travelling = bundle of His in septum conducts
- Depolarization travels down septum to Purkyne fibers in wall of ventricles
- Apex contracts = ventricles contract
Why do non-conducting tissue delay impulse?
- Allows time for atria to pump blood into ventricle
- Cells can repolarize
What is the autonomic nervous system?
- Controls involuntary actions of glands + muscles
- Consists of sympathetic + parasympathetic
Difference between 2 autonomic nervous systems
- Sympathetic: Stimulates effectors to speed up activity
- Parasympathetic: Inhibits effectors to slow down
Heart rate in response to increased pressure
- Increased pressure = Pressure-receptors in the aorta + carotid are stretched
- More electrical impulses sent to medulla oblongata via parasympathetic to SAN to decrease frequency of electrical impulses
- SAN = reduced heart rate
Heart rate in response to decreased pressure
- Decreased pressure = Pressure-receptors in aorta + carotid are not stretched
- More electrical impulses sent to medulla oblongata via sympathetic to SAN to increase electrical impulses
- SAN = increased heart rate
Heart rate in response to decreased pH
- Decreased pH = Chemoreceptors in aorta + carotid pick up change
- More electrical impulses sent to medulla oblongata via sympathetic to SAN to increase frequency of electrical impulses
- SAN = increases rate of blood delivered to lungs to remove CO2
