13.3 Sensory receptors

Question 1

what are effectors

Answer 1

muscles or glands that create the desired response to a stimulus

Question 2

what are the 2 main features of sensory receptors

Answer 2

• specific to a single type of stimulus

- act as a transducer (convert a stimulus into a nerve impulse)

Question 3

what are the 4 main sensory receptors in animals

Answer 3

• mechanoreceptor
• chemoreceptor
• thermoreceptor
• photoreceptor

Question 4

describe mechanoreceptors

Answer 4

• stimulus: pressure and movement
• e.g: Pacinian corpuscle (pressure)
• e.g. of sense organ: skin

Question 5

describe chemoreceptors

Answer 5

• stimulus: chemicals
• e.g: olfactory receptor (smell)
• e.g. of sense organ: nose

Question 6

describe thermoreceptors

Answer 6

• stimulus: heat
• e.g: end-bulbs of Krause
• e.g. of sense organ: tongue

Question 7

describe photoreceptors

Answer 7

• stimulus: light
• e.g: cone cell
• e.g. of sense organ: eye

Question 8

explain the role of sensory receptors as transducers

Answer 8

• detect range of stimuli

- receptor converts stimulus into generator potentials

Question 9

what are Pacinian corpuscles

Answer 9

• specific sensory receptors that detect mechanical pressure
• located deep in the skin
• abundant in fingers and soles of feet
• found within joints (know which joints change direction)

Question 10

describe the structure of the Pacinian corpuscle

Answer 10

• sensory neuron ends in the centre
• surrounded by layers of connective tissue
• layers separated by a layer of gel
• neuron membrane contains sodium channels
• neuron ending has a stretch-mediated channel which can change shape and therefore change permeability

Question 11

explain how a Pacinian corpuscle converts mechanical pressure into a nervous impulse

Answer 11

1. Neurone of the Pacinian corpuscle has a resting potential in its resting state and the stretch-mediated sodium channels are very narrow
2. Pressure causes the corpuscle and neurone membrane to change shape
3. Sodium ion channels present widen so sodium ions can diffuse into the neurone
4. The membrane becomes depolarised and results in a generator potential
5. Generator potential creates an action potential
6. Action potential transmitted along neurons in the CNS