Receptors (14) Flashcards
What are 3 reasons why a simple reflex arc is important?
1) escape from predators
2) have role in homeostasis
3) preventing injury
What are the stages of a simple reflex arc?
receptor detects stimulus > sensory neuron > intermediate (relay) neuron > motor neuron > response by effector
What is the overall structure of the nervous system?
look at notes
What are 2 advantages of a simple reflex?
1) rapid response as only 3 neurons are involved
2) instinctive so does not have to be learnt
What are 2 common features of all sensory receptors?
- respond to specific stimuli
- act as energy transducers which establish a generator potential
What is the structure of a Pacinian corpuscle? (what does it contain)
- stretch-mediated sodium ion channels on plasma membrane
- capillary runs along base layer of tissue
What are the 3 steps on how a Pacinian corpuscle responds to stimuli?
1) pressure deforms membrane, causing stretch-mediated sodium ion channels to open
2) if influx of sodium ions raises membrane threshold potential, generator potential is prodced
3) action potential moves along sensory neuron
What are the 2 types of photoreceptor cell?
rod cell
cone cell
What are rod and cone cells?
photoreceptor cells
Where are rod cells located?
evenly distributed around periphery but NOT in central fovea
Where are cone cells located?
mainly in central fovea
Where are photoreceptors not located?
at blind spot
What are the 4 differences between cone and rod cells?
1) pigment
2) visual acuity
3) colour sensitivity
4) light sensitivity
How do cone and rod cells differ in terms of pigment?
rod - rhodopsin
cone - 3 types of iodopsin
How do cone and rod cells differ in terms of visual acuity?
rod - low as many rod cells connected to 1 bipolar neuron
cone - higher as 1 cone cell connected to 1 bipolar neuron so cones send separate impulses to brain
How do cone and rod cells differ in terms of colour sensitivity?
rod - monochromatic as all wavelengths are detected
cone - tricolour as red, blue, and green wavelengths are absorbed by the 3 different types of iodopsin
How do cone and rod cells differ in terms of light sensitivity?
rod - very light sensitive due to spatial summation which helps overcome threshold
cone - low as not involved in night vision
What is the pathway of light from a photoreceptor to the brain?
photoreceptor > bipolar neuron > optic nerve > brain
Where is the Pacinian corpuscle located?
located in skin, particularly fingers, feet soles, and joints on ligaments/tendons
What is the Pacinian corpuscle?
single nerve fibre surrounded by layers of connective tissue which are separated by viscous gel and contained by a capsule
