Sensory receptors-1 Flashcards
What is a grey matter?
Collection of cell bodies in the CNS
What is a ganglia?
Collection of cell body in the peripheral nervous system
What are the different types of neurons?
1) Bipolar (interneuron)
2) Unipolar (always sensory neuron)
3) Multipolar (motor neuron)
4) Pyramidal cell
What are the types of ganglia?
1) Autonomic (cell bodies of postsynaptic neurons)
2) Dorsal root (cell body of sensory neuron)
What are the motor signals that goes out of the brain?
1) Autonomic (we cannot control it) “1 pre & 1 post”
2) Somatic (voluntary) one neuron outside the CNS cell body is found in the CNS “grey matter”
Describe the route of sensory signals
1) Sensory axon that has a ganglia
2) Synapses in the spinal cord for it to continue along the spino-thalamic tract axon
3) Synapses in the brain to go to the sensory cortex which will signal the motor for movement
Describe the somatic route
1) Upper motor neuron from the brain to the spinal cord
2) Lower motor neuron from the spinal cord to the muscle
What are the branches of the nervous system
1) CNS
2) PNS
What are the branches of the PNS?
1) Motor nervous system
2) Sensory nervous system
What are the different sensory receptors we have in our body?
1) Skin
2) Eyes
3) Muscles (pain and position)
4) Ears
5) Nose
6) Tongue
- FYI sensory receptors converts mechanical/chemical/light, etc stimulus o electrical signals, the stimulus must be strong enough to reach the threshold for us to feel it
What is the proper definition of a sensory receptor?
They are specialized cells that converts internal/external stimuli into electrical nerve impulse and transmits them to the CNS
- Example of internal stimuli: pain in heart attack, stomach ulcer, kidney stones, bone fracture / temperature in esophagus for hot and cold food
How do sensory receptor detect a stimuli?
1) Detects a stimulus by (Being deformed (touch) Receiving light (vision) Receiving chemicals (taste) Detecting change in temp)
2) Stimulus causes a depolarization
3) Depolarization causes a action potential that will be transmitted as a nerve impulse along the neurons and to the sensory cortex in the brain
What are the types of receptors?
1) Photoreceptors (Rods & cons)
2) Chemoreceptors (taste & oxygen regulation)
3) Nociceptors (“pain” somatosensory)
4) Thermoreceptors (somatosensory)
5) Mechanoreceptors (somatosensory)
What types of stimuli do nociceptors detect and where are they found in the body?
- They can detect mechanical, thermal and polymodal (both mechanical and thermal stimuli), like sharp pricking pain and extreme temperature
- They are found in the skin, bones and heart
What type of stimuli do thermoreceptors detect and where are they found in the body?
1) They are active in a specific range of warm and cold where outside that range you will feel pain that is detected by the nociceptors
2) They are found in the skin, digestive tract, liver, & skeletal muscles
What are the different types of mechanoreceptors?
1) Pacinian corpuscle
2) Meissner corpuscle
3) Hair follicles
4) Ruffini corpuscle
5) Merkel receptors
6) Tactile discs
What is the location, adaptation & the sensation encoded by pacinian corpuscle?
1) Found subcutaneously, and intramuscular
2) They adapt rapidly
3) The sensation they encode is vibration, pressure and tapping
- Pac-man is muscular and rapid and vibrates on pressure
What is the location, adaptation & the sensation encoded by meissner corpuscle?
1) They are found in the non-hairy skin
2) They adapt rapidly
3) The sensation they encode is point discrimination, tapping, and flutter
What is the location, adaptation & the sensation encoded by hair follicles?
1) Found in hairy skin
2) They adapt rapidly
3) The sensation they encode is velocity, and direction of movement
What is the location, adaptation & the sensation encoded by ruffini corpuscle?
1) They are found in hairy skin
2) They adapt slowly
3) The sensation they encode is stretch and joint rotation
- Rough pressure “stretches” the “joint” “skin” “slowly”
What is the location, adaptation & the sensation encoded by merkel receptors?
1) They are found in non-hairy skin
2) They adapt slowly
3) The sensation they encode is the vertical indentation of the skin
What is the location, adaptation & the sensation encoded by tactile disc?
1) They are found in the hairy skin
2) They adapt slowly
3) The sensation they encode is vertical indentation of the skin
What are the different receptors found in the hairy skin?
1) Hair follicles
2) Ruffini corpuscles
3) Tactile discs
What are the mechanoreceptors that are found in the non-hairy skin?
1) Meissner corpuscle
2) Merkel receptors
What is the difference between a weak stimulus and a strong stimulus?
Weak stimulus has a weak action potential which does not reach the threshold and thus does not activate the action potential receptor, and vice versa
What happens if the stimulus increases in intensity?
Amplitude of receptor potential responds less and less as the stimulus strength increases
What happens if the stimulus is continous?
- Like the touch of chair for example
The intensity will decrease due to the decrease in receptor activity
What is a tonic receptor?
Receptors that reduces the sensation like Merkel receptors
- They start with a high activity, then reduce the firing rate with time making us feel less and less stimulus, like when hearing loud noises for a long time
- They care for the intensity & duration of the stimulus
What is a phasic receptor?
They stop the sensation like Pacinian corpuscle they are active at the start and end of a stimuli
- They start with high activity
- Then they will have no activity until the stimulus disappears
- They only care for the onset/offset of the stimulus
What are the different tracts we have for sensory signals?
1) Anterolateral (light touch, pain, temperature, etc), they also have a second order neuron that crosses the midline in the spinal cord
2) Dorsal column system (fine touch, pressure, position)
What is meant by sensation?
It is the conscious or subconscious awareness of the environment through sensory receptors
What is meant by perception?
It is the interpretation of the information by the brain
- Subjective from a person to another
