Week 8 - Somatosensory System: Touch and Pain

The Somatosensory System is divided into 3 separate and interacting systems

1. Exteroceptive: external stimuli

2. Proprioceptive: body position

3. Interoceptive: body conditions such as temperature and blood pressure

Our cutaneous receptors: AKA the receptors in our skin that respond to stimulus.

How are the brain and spinal cord related to our touch receptors?

Information from our touch receptors travels to our brain, which then enter the CNS (central nervous system), entering our spinal cord and passes through our brain in segments.

Dermatome

Every part of our skin is connected to a single sensory spinal nerve

What are the two major somatosensory pathways?

1. Dorsal-column medial lemniscus system

2. Anterolateral System

Dorsal-column Medial Lemniscus System

touch and proprioception, synapses in the dorsal column nuclei on the medulla

Anterolateral System

focuses on pain and temperature, synapses upon entering the spinal cord. Contains 3 tracts: spinothalamic, spinoreticular, and spinotectal

Where is the primary somatosensory cortex located?

Behind the central sulcus

Astereognosia

inability to recognize objects by touch

Asomatognosia

failure to recognize one’s own body parts; lack of perception due to deficits in the somatosensory system.

Why does the phantom limb experience happen?

1. area of the somatosensory cortex reorganizes its connections, becoming responsive to other body parts

2. irritation of the nerves in the amputated area that sends signs to S1 areas, causing pain.

Periaqueductal Gray (PAG)

where the incoming pain signals go to be processed and dealt with

Endorphins

neurotransmitters that play a role in reducing pain

How does the PAG control pain?

Gate Theory

Pain is perceived when certain areas of the spinal cord receive messages from other receptors in the skin, so if you close those gates of pain receptors, pain will be reduced.

Analgesia

the inability to feel pain

What activities induce analgesia?

long distance running, sexual activities, music. Certain types of painful stimuli will decrease pain sensitivity by adapting with endorphin release

Placebo Effect

Perception is reality: if humans think something is happening to them when nothing is happening, they will still experience the effects of it.