Download presentation
Presentation is loading. Please wait.
1
Sensory Receptors/ Endings/ Organs
November 23, 2018 sensory receptors
2
Sensory Receptors Sensory receptors/ endings/ organs
Specialized structures Respond to changes in stimuli from the environment (external or internal) Convert stimulus energy into electrical energy: action potential November 23, 2018 sensory receptors
3
Sensory Receptors The action potential Transmitted to the CNS
Information when analyzed may lead to: Conscious sensation: sound, heat, light, pain Regulation of body functions: BP, Osmolarity, blood sugar levels November 23, 2018 sensory receptors
4
Sensory Receptors Primary receptors Part of the NEURON
Forms the peripheral nerve endings or receptor endings November 23, 2018 sensory receptors
5
Sensory Receptors Secondary receptors
Specialized non neural cell that generate action potential in a neuron November 23, 2018 sensory receptors
6
Classification Based on SOURCE of stimulus Exteroreceptors:
Eyes, nose, ears, cutaneous receptors Enteroreceptors: Proprioceptors Visceral receptors November 23, 2018 sensory receptors
7
Classification Based on anatomical, area, division serving
Special sensory receptors Somatic sensory receptors Visceral sensory receptors November 23, 2018 sensory receptors
8
Classification Based on type of agent stimulating receptors
Mechanoreceptors Skin tactile sensibility Free nerve endings, Ruffinis end organs, Merkels discs, Pacinian corpuscles, Meissners corpuscles, hair endorgans November 23, 2018 sensory receptors
9
Classification Deep tissue sensibility
Free nerve endings, pacinian, muscle spindles Hearing: hair cells Equilibrium: hair cells Baroreceptors November 23, 2018 sensory receptors
10
Classification Thermo-receptors: Cold and warm Nociceptors (pain):
Free nerve endings Photoreceptors (electromagnetic) Rods and cones Chemo-receptors.: Taste, smell, PO2, PCO2, osmolarity November 23, 2018 sensory receptors
11
Specificity Receptors are specially adapted to respond to
One type of stimulus At a much lower threshold November 23, 2018 sensory receptors
12
Specificity Light Adequate stimulus:
Particular form of energy to which the receptor is most sensitive Light Rods, cones in the eyes November 23, 2018 sensory receptors
13
Specificity Temperature Pressure Ruffinis Cold and warm receptor
November 23, 2018 sensory receptors
14
Specificity However, almost all receptors can be activated by different forms of energy Pressure on the eyes – see stars Extreme heat or cold – feel pain November 23, 2018 sensory receptors
15
Receptor Activation Transduction of sensory stimuli into nerve impulses What process takes place between The application of sensory stimulus The generation of a nerve impulse November 23, 2018 sensory receptors
16
Receptor Activation Stimulus energy alters membrane potential at receptor to cause Receptor potential This has ability to Generate action potential at sensory axon November 23, 2018 sensory receptors
17
Receptor Activation Membrane potential depend on receptor type:
Mechanisms that alter Membrane potential depend on receptor type: Mechanoreceptors: Have mechanically gated channels Mechanical deformation Stretch the membrane Opens ionic channels November 23, 2018 sensory receptors
18
Receptor Activation Which changes permeability of membrane to ions
Chemoreceptors: Have Ligand gated channels Chemicals opens ionic channels Thermoreceptors: Change in temperature Alter membrane property Which changes permeability of membrane to ions November 23, 2018 sensory receptors
19
Receptor Activation Photoreceptors Effects of electro magnetic waves
Directly or indirectly change membrane characteristics Alter ionic permeability November 23, 2018 sensory receptors
20
Receptor Activation In general
Excitation at afferent nerve endings by different stimuli leads to Local changes in permeability of receptor membrane Leads to flow of ions (K+, Na+,Cl-) along concentration gradients November 23, 2018 sensory receptors
21
Receptor Activation This leads to change in the trans-membrane potential Leading to a local depolarization (generator/receptor potential) November 23, 2018 sensory receptors
22
Receptor Activation If the receptor potential is of
Adequate magnitude (eg 10 mV for the Pacinian corpuscle) This leads to a conducted action potential November 23, 2018 sensory receptors
23
Receptor Potential Production of generator potential
AP Production of generator potential Example in the Pacinian corpuscle The capsule of the pacinian corpuscle is filled with fluid + + + - - + - November 23, 2018 sensory receptors
24
Receptor Potential Composition similar to
AP Composition similar to That of the extra-cellular fluid Contains collagenous fibers The corpuscle is turgid and scarcely compressible + + + - - + - November 23, 2018 sensory receptors
25
Receptor Potential Local mechanical stimulus leads to
AP Local mechanical stimulus leads to Deformation of lamellar of the corpuscle This causes local change in the permeability of membrane + + + - - + - November 23, 2018 sensory receptors
26
Receptor Potential Ions flow across the membrane
AP Opening ionic channels Ions flow across the membrane Leading to local depolarization Generator potential + + + - - + - November 23, 2018 sensory receptors
27
Receptor Potential AP If the generator potential is of sufficient magnitude Then action potential is conducted along the sensory nerve + + + - - + - Action potentials Generator potentials November 23, 2018 sensory receptors
28
Stimulus Strength Effect of stimulus strength As pressure increases
The magnitude of receptor (generator, GP) potential increases As the pressure is increased Receptor potential becomes even larger Sensory nerve fires repetitively November 23, 2018 sensory receptors
29
Stimulus Strength As a result
The core continues to Emit receptor potential As long as stimulus is applied As a result As soon as the 1st node of Ranvier repolarizes It discharges once again November 23, 2018 sensory receptors
30
Stimulus Strength Action potential continues Frequency of AP
As long as receptor potential persists Frequency of AP Proportional to amplitude of receptor potential November 23, 2018 sensory receptors
31
Adaptation of Receptors
In most receptors, however, The receptor potential decays during a constant stimulation Receptor adapts to the stimulus Rate of adaptation Vary among receptors November 23, 2018 sensory receptors
32
Adaptation of Receptors
Slowly adapting receptor Stretch receptors Intermediate adaptation Temperature, light Rapid adapting receptor Pacinian corpuscle November 23, 2018 sensory receptors
33
Adaptation of Receptors
Rapidly adapting receptors Suited to record alteration of stimulus With high sensitivity Slowly adapting receptors Serve to detect long term conditions State of muscle stretch November 23, 2018 sensory receptors
34
Adaptation of Receptors
Adaptation of receptors is Reflected in in frequency of AP During a maintained stimulus November 23, 2018 sensory receptors
Similar presentations
