5.3.1 roles of sensory receptors

Question 1

pacinian corpuscle

Answer 1

pressure sensor found in skin

Question 2

sensory receptors

Answer 2

cells/sensory nerve endings which respond to stimulus in internal/external environment of organism & can create action potentials

Question 3

transducer

Answer 3

cell which converts one form of energy into another (eg. electrical impulse)

Question 4

describe sensory receptors

Answer 4

• specialised cells which detect changes in environment
• most energy transducers

Question 5

stimulus

Answer 5

change in environment

Question 6

stimulus: change in light intensity
sensory receptor =
energy change involved =

Answer 6

sensory receptor = light sensitive cells (rods & cones) in retina

energy change involved = light to electrical

Question 7

stimulus: change in temp
sensory receptor =
energy change involved =

Answer 7

sensory receptor = temperature receptors in skin & hypothalamus

energy change involved = heat to electrical

Question 8

stimulus: change in pressure on skin
sensory receptor =
energy change involved =

Answer 8

sensory receptor = pacinian corpuscles in skin

energy change involved = movement to electrical

Question 9

stimulus: change in sound
sensory receptor =
energy change involved =

Answer 9

sensory receptor = vibration receptors in cochlea of ear

energy change involved = movement to electrical

Question 10

stimulus: movement
sensory receptor =
energy change involved =

Answer 10

sensory receptor = hair cells in inner ear

energy change involved = movement to electrical

Question 11

stimulus: change in length of muscle
sensory receptor =
energy change involved =

Answer 11

sensory receptor = muscle spindles in skeletal muscles

energy change involved = movement to electrical

Question 12

stimulus: chemicals in air
sensory receptor =
energy change involved =

Answer 12

sensory receptor = olfactory cells in epithelium lining nose

energy change involved = these receptors detect presence of chemical & create electrical nerve impulse

Question 13

stimulus: chemicals in food
sensory receptor =
energy change involved =

Answer 13

sensory receptor = chemical receptors in taste buds in tongue

energy change involved = these receptors detect presence of chemical & create electrical nerve impulse

Question 14

structure of pacinian corpuscle

Answer 14

• oval-shaped structure
• consists of concentric rings of connective tissue wrapped around end of nerve cell
• pressure changes in skin = deforms rings of connective tissue which push against nerve ending

Question 15

what happens when pressure is constant

Answer 15

= stops responding
- corpuscle only sensitive to changes in pressure which deforms rings of connective tissue

Question 16

how does membrane permeability change
- open/closed channel proteins

Answer 16

• if channel proteins permanently open = ions can diffuse across
• do so until concentrations on either side of membrane reached equilibrium
• if channels closed = action of active pumps can create concentration gradient across membrane

Question 17

changing membrane permeability
- sodium/potassium channels

Answer 17

–> possess gate which can open/close channel

1. sodium channels = specific to sodium ions (Na+)
   - sensitive to small movements of membrane
   - if membrane deformed (change in pressure) = sodium channels open
   - sodium ions can diffuse into cell producing generator potential
2. potassium channels = specific to potassium ions (K+)

Question 18

changing membrane permeability
- sodium/potassium pump

Answer 18

• actively pump sodium ions out of cell & potassium ions in
• 3 sodium ions pumped out for every 2 potassium ions
• channel proteins closed = sodium/potassium pump works to create concentration gradient
• concentration of sodium ions outside cell increases
• concentration of potassium ions inside cell increases
• membrane more permeable to potassium ions = some leak out
• membrane less permeable to sodium ions

Question 19

what is the result of these ionic movements within the membrane/cell

Answer 19

= potential gradient across membrane
- cell negatively charged inside compared to outside
- negative potential enhanced by negatively charged anions inside cell

Question 20

what is the cell membrane called when the cell is inactive

Answer 20

polarised

Question 21

polarised

Answer 21

negatively charged inside compared to outside

Question 22

how is a nerve impulse created

Answer 22

= by altering permeability of nerve cell membrane to sodium ions

• achieved by opening sodium ion channels
• causes membrane permeability to increase & sodium ions can diffuse into membrane down concentration gradient
• movement of ions across membrane creates change in potential difference across membrane
• inside of cell becomes less negative than usual (compared to outside
  = DEPOLARISATION

Question 23

generator potential

Answer 23

change in potential across a receptor membrane

Question 24

impact of size of stimulus

Answer 24

• small stimulus detected = few sodium channels will open
• larger the stimulus = more gated channels open

–> if enough gates opened & enough sodium ions enter cell, potential difference across cell membrane changes significantly = initiate impulse or action potential