Stimuli and Response Flashcards
What is a tactic response (taxis)?
-Directional movement in response to a stimulus, the direction of the stimulus affects the response
What is kinetic response (kinesis)?
-Non-directional (random) movement in response to a stimulus, the intensity of the stimulus affects the response
What is a sensory neurone?
-Transmits electrical impulses from receptors to the CNS
What is a motor neurone?
-Transmits electrical impulses from CNS to effectors
What is a relay neurone?
-Transmits electrical impulses between sensory neurones and motor neurones
Why are simple reflexes involuntary?
-The pathway of communication doesn’t go through conscious parts of the brain
What is phototropism?
-The growth of a plant in response to light
How do roots and shoots grow in response to light?
-Roots=negatively phototropic
-Shoots=positively phototropic
What is gravitropism?
-The growth of a plant in response to gravity
How do roots and shoots grow in response to gravity?
-Roots=positively gravitropic
-Shoots=negatively gravitropic
Where is auxin produced?
-In the tips of roots and shoots and diffuses down the plant
What does auxin stimulate?
-Growth in shoots
-Inhibit growth in roots
What does IAA stimulate?
-Cell elongation
What is a resting potential?
-Outside of the membrane is positive and inside of the membrane is negative
What is a generator potential?
-Membrane is stimulated and becomes excited and more permeable
-Allows more ions to move in and out of the cell
-Changes the potential difference
-Bigger stimulus=bigger change of potential difference=bigger generator potential
What is an action potential?
-Generator reaches threshold level
-All same size, strength of stimulus is is measured by frequency of action potentials
Describe the structure of a Pacinian corpuscle
-End of a sensory neurone wrapped in layers of connective tissues called lamellae
What happens when a Pacinian corpuscle is stimulated?
-Lamellae become deformed and press on end of sensory neurone
-Sensory neurone membrane stretches
-Stretch-mediated sodium ion channels become deformed
-Channels open and sodium ions diffuse into cell
-Generator potential created
-If threshold reached->action potential
How do photoreceptors work?
-Light enters eye
-Pigment in photoreceptor breaks down
-Membrane becomes more permeable to sodium ions
-Sodium ions diffuse in
-Generator potential
-If threshold reached->action potential
What are properties of cone cells and where are they found?
-Found in the fovea
-Detect 3 colours->red, yellow and blue
-Sensitive to bright light
-High visual acuity as one cone joins to one bipolar neurone
What are properties of rod cells and where are they found?
-Found in the peripheral parts of the retina
-Detect black and white light
-Sensitive to dim light
-Low visual acuity as many rods join to the same bipolar neurone
What is visual acuity?
-The ability to tell apart points that are close together
What does myogenic mean?
-The heart muscle can contract and relax without receiving signals from nerves
Describe and explain how heart rate is controlled
-The sinoatrial node (SAN) acts as a pacemaker, causes right and left atria to contract at the same time
-Electrical signals are transferred to the atrioventricular node (AVN)
-Electrical signals passed onto the bundle of His
-Then onto the Purkyne tissue which carries the electrical signals into walls of ventricles causing them to contract from the bottom up
Describe how high blood pressure is detected and what happens when it is
-Baroreceptors detect a change in blood pressure
-Impulses sent along sensory neurone to medulla
-Impulses sent along parasympathetic neurones
-Acetylcholine secreted
-Binds to receptors on SAN
-Slows down heart rate->decreases blood pressure
Describe how low blood pressure is detected and what happens when it is
-Baroreceptors detect change in blood pressure
-Impulses sent along sensory neurones to medulla
-Impulses sent along sympathetic neurones
-Secrete noradrenaline
-Binds to receptors on SAN
-Increases heart rate->increases blood pressure
Describe how high blood pH, high O2 or low CO2 levels are detected and how this is counteracted
-Chemoreceptors detect change
-Impulses sent along sensory neurones to medulla
-Impulses sent along parasympathetic neurones
-Acetylcholine secreted
-Binds to receptors on SAN
-Heart rate decreases->counteracts change
Describe how low blood pH, low O2 or high CO2 levels are detected and how this change is counteracted
-Chemoreceptors detect change
-Impulses sent along sensory neurones to medulla
-Impulses sent along sympathetic neurones
-Noradrenaline secreted
-Binds to receptors on SAN
-Heart rate increases->counteracts change
