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.