biolpsy_lecture08
Biological Psychology Lecture 08: Sensory Systems IInstructor: Dr. Richárd ReichardtContact: reichardt.richard@ppk.elte.hu
Basic Rules of Sensation
All living things interact with their surroundings through matter and energy.
Stimuli can activate receptors in our nervous system, leading to feelings or sensations.
Specific types of stimuli are better at activating certain receptors.
How Sensory Systems Work
Sensory systems only respond to a limited range of stimuli.
Different animal species may have very different ranges of responsiveness.
Labeled Lines
Different receptors create different perceptions.
Each receptor connects to specific areas of the nervous system through pathways called labeled lines.
Sensory Transduction
When a receptor cell is stimulated, it changes its membrane potential, called the receptor potential.
Sensory Pathways
Most sensory pathways help send signals from receptors to the thalamus through the spinal cord and brainstem and then to the appropriate areas of the brain.
Receptive Field
The receptive field of a sensory neuron is the specific area where stimulation influences the neuron’s activity.
The Hard Problem of Consciousness
It is still unclear how brain activity produces conscious experiences; some think we may never fully understand this.
The Somatosensory System
Receptors for Touch
There are four types of receptors in the skin that help us sense touch.
The distribution of these receptors differs depending on body parts.
Touch Receptors and Braille Response
Merkel's Discs: Fire when touched and provide ongoing information as they adapt slowly.
Meissner's Corpuscles: Have larger areas they respond to, adapt quickly, and provide less clear information.
Ruffini's Endings: Respond to stretch but do not give a clear picture of form.
Pacinian Corpuscles: Respond to vibrations, giving information about texture.
Discovery of Touch Receptors
The Nobel Prize was awarded to Ardem Patapoutian and colleagues for discovering Piezo1 and Piezo2 in 2021.
Piezo2 is found in Merkel's discs and reacts to mechanical pressure, changing the cell’s membrane potential.
Somatosensory Pathways Overview
Touch receptors pick up stimulation on the skin and send signals through axons that enter the spinal cord.
The axons then join the dorsal white matter column and go up to the brain.
The first synapse occurs in the medulla, and then axons switch sides before heading to the thalamus, which relays information to the primary somatosensory cortex.
Skin Surface Innervation
Each dermatome is an area of skin served by a specific spinal nerve (there are overlapping boundaries between dermatomes).
Primary Somatosensory Cortex
This area represents the body’s surface.
A sensory homunculus shows how much space in the brain is allocated to different body parts.
Plasticity in the Somatosensory Cortex
After losing a hand, the areas that represent the remaining arm and face can expand into the area previously representing the hand.
Nociceptors and Pain Perception
Nociceptors are free nerve endings that detect pain.
Some also react to temperature changes and certain chemicals, contributing to our sense of temperature.
Pain Pathways
Signals related to pain travel to the brain through the spinothalamic or anterolateral tracts.
Modulating Pain
Pain sensations can be modified at different points along the pain pathway.
Chronic pain is a serious and difficult medical issue.
Phantom Pain
People can feel pain in a limb that has been amputated (phantom limb pain).
Mirror therapy, created by Vilayanur Ramachandran, uses an intact limb's reflection to help reduce phantom pain by tricking the mind into perceiving movement in both limbs.
Itch Receptors
There are specific receptors for itching, which are mainly sensitive to histamine.
Pathways for itching signals also use the anterolateral tract.
Conclusion
Thank you for your attention!
Next class: Sensory Systems II.