Sensory 1: Sensory Receptors

Question 1

Sensory Unit is made up of

Answer 1

single afferent fiber+ Receptor Ending

Question 2

Enumerate functions of Sensory Receptors

Answer 2

1. Detector
2. Trasducer
3. Generator of Action potential

Question 3

Explain how sensory receptor is transducer

Answer 3

coonverts any type of stimulus into Electrical Energy, known as Signal Transduction

Question 4

Enumerate properties of Sensory Receptors

Answer 4

1. Specificity
2. Excitability (Transduction)
3. Adaptation

Question 5

Definition of Specificity of Sensory receptor

Answer 5

Receptor reacts to specific stimulis

Question 6

Enumerate properties of Receptor Potential (Local Response)

Answer 6

1. Non-propagated
2. Can Be summated (no ARP)
3. Doesn’t obey all or non law (can be graded)
4. 5-10 msec (longer than Action potential)
5. Maximum capacity=100 mV

Question 7

explain How Local Response generates Action potential

Answer 7

1. Stimulation arrives as Deformational Changes to the receptor/ capsule
2. This Change causes opening of cation channels which causes Depolization (local Response)
3. Electronic Spread/ passive spread: Depolarization spreads to Action potential Generating zone, which is the 1st node of ranvier (it has a low firing level)
4. Action potential Is generated and travels through afferent fiber

Question 8

Explain the relationship between Intensity of stimulus on Receptor & Number of Action potentials generated

Answer 8

As Intensity increases, No. of Channels opening Increases, so Longer period of Local response, so Higher number of Action potentials Generated

Question 9

Define Adaptation of Sensory Receptor

Answer 9

Gradual Loss of Receptor potential (local response) Despite constant presence of Adequate stimulus of constant strength

Question 10

Causes of Adaptation of Sensory Receptors

Answer 10

1. remodelling or readjustment of Structure of receptor itself
2. Accommodation: Caused by the continuous current flow causing inactivation of Na+ channels at Action potential Generating Zone (1st node of Ranvier)

Question 11

Enumerate types of receptors according to rate of Adptation

Answer 11

• Rapidly adapting (phasic)
• Slowly Adapting (Tonic)

Question 12

importance, mechanism & example of Phasic (rapidly adapting) Receptors

Answer 12

• Mechanism: Discharge strongly when stimulus takes place
• Importance: Detection of movement & vibration
• Examples: touch & pressure receptors

Question 13

importance & example of tonic (slowly adapting) Receptors

Answer 13

• Importance: Keep the brain continuously Informed

Examples:
* Pain receptors
* Muscle spindles
* Alveolar stretch receptors
* Arterial Barorecptors

Question 14

Receptors that are both Phasic and tonic

Answer 14

• Proprioceptors
• Thermoreceptors

Question 15

Relationship between Receptor Potential amplitude and stimulus strength and it’s effect on receptor sensitivity

Answer 15

As stimulus strength increases, receptor potential Magnitude increases rapidly at first, then progressivly less

• The rapid increase of potential Magnitude at first, causes the receptor to have an extreme response range, making it higly sensitve
• The progressively less increase in magnitude is caused by limited amount of non-specific (cation) channels