Topic 6A: Stimuli and Responses Flashcards
What makes up the CNS?
- Brain
- Spinal cord
What makes up the PNS?
- Somatic - conscious activities
- Autonomic - unconscious activities
What are the two parts of the autonomic nervous system?
- Sympathetic - increases activity
- Parasympathetic - decreased activity
What route does a reflex take?
- Stimulus
- Receptor
- Sensory neurone
- Relay neurone
- Motor neurone
- Effector
- Response
How are reflexes localised?
- Neurotransmitters secreted directly onto cells
How are reflexes short lived?
- Neurotransmitters are quickly removed
How are reflexes rapid?
- Electrical impulses are very fast - allows for quick reactions
What is a tropism?
- Response to a directional stimulus in plants
- Growth response
What tropisms do shoots do?
- Positively phototropic
- Negatively gravitropic
What tropisms do roots do?
- Negatively phototropic
- Positively gravitropic
What auxin performs tropisms and how is it transported?
- Indoleacetic acid (IAA)
- Short distances - diffusion and active transport
- Long distances - phloem
What does IAA do in shoots?
- Stimulates cell elongation
What does IAA do in roots?
- Inhibits cell elongation
Where does IAA move to?
- Lower or shaded side
What is a taxis?
- Directional movement response to a stimulus
What is a kinesis?
- Non directional response to a stimulus
What performs taxes and kinesis?
Invertebrates
What are choice chambers?
- Have different compartments to create different environmental conditions
What are choice chambers used for?
- Investigating how animals respond to different conditions
What do pacinian corpuscles detect?
pressure - in the skin
How do pacinian corpuscles work?
- Stimulated by pressure
- Lamellae deformed
- Stretches membrane of sensory neurone inside
- Opens stretch mediated sodium ion channels
- Sodium ions move in
- Depolarises
- Generator potential made
- If threshold reached - action potential formed
How do photoreceptors work?
- Light sensitive pigments absorb light
- Become bleached
- Cause a chemical change - become more permeable to sodium ions
- Generator potential formed
What is visual acuity?
- Ability to distinguish between two points that are close together
What is retinal convergence?
- Several rods connect to one bipolar cell
- Summation occurs - effect of neurotransmitters added together so threshold reached more easily
What pigment is in rods?
Rhodopsin
Where are rods found?
Periphery of retina
What do rods make images in?
black and white
What sensitivity to light do rods have and why?
- Very sensitive
- Multiple join to one bipolar cell
- Weak generator potentials added together to reach the threshold
What visual acuity to rods have and why?
- Low visual acuity
- Multiple join to one bipolar cell
- Cannot tell them apart
What pigment is in cones and what colour light are they sensitive to?
- Iodopsin
- Red, green or blue sensitive
Where are cones found?
Fovea
How sensitive to light are cones and why?
- Less sensitive
- Each join to their own bipolar cell
- Takes more light to reach the threshold
What visual acuity do cones have and why?
- High visual acuity
- Close together
- Each join to their own neurone
- Make separate action potentials
How is heart rate stimulated?
- SAN sends impulses across the atria causing them to contract
- Non-conducting tissue prevents the atria and ventricles contracting together
- The impulse is delayed at the AVN so that the atria can fully empty of blood before the ventricles contract
- The impulse travels down the bundle of His to the apex of the heart
- Then move up purkyne fibres to make the ventricles contract from the bottom up
How is heart rate increased?
- Impulses to medulla
- More frequent impulses down sympathetic nerve releasing neuradrenaline
- The SAN sends impulses more frequently
- Heart rate increases
How is heart rate decreased?
- Impulses to medulla
- More frequent impulses sent down the vagus nerve
- Releases acetylcholine
- Decreases frequency of impulses from SAN
- Decreases heart rate
What detects CO2 or pH levels in blood?
chemoreceptors
What detects blood pressure?
baroreceptors
Where are these receptors found?
carotid body
aortic arch
