Perception L3

Touch fibres

There are two types: Rapid adopting Slow Adapting

Detection of pain and temperature

you need to feel pain in order to protect your self.

3 types of receptor

1. Mechanoreceptor 2. Nociceptor 3. Thermoreceptor

Capsaicin

Active component of chilli peppers. Activate polymodal fibres. These fibres are present in all mammals, except for birds. Repeated exposure to chilli cause decline in neuronal response, therefore become tolerant.

Golgi tendon organ

Another type of proprioceptor that provides information about changes in muscle tension. e.g. if i lift up a heavy object, the tension is created. As the object becomes heavier, more tension is needed therefore the receptor detects this tension and tell the brain to exert more muscle.

Slow adapting

As you hold the stimulus(insect) for a while, then more slow fibre responding to the stimulus. consist of : Markel disks Ruffini organ

Meissner corpuscle

Elongated receptor found underneath the finger, palm and soles. When the corpuscle is deformed by pressure, the nerve endings are stimulated, creating AP that cause the sensation of touch. sensitive to light touch and vibration. because Meissner's corpuscles are quickly deactivated, you eventually stop feeling the clothing on your skin.

Ruffini organ

Elongated spindle shaped structure. located deep in the skin and ligament. Responsible for sensation of the stretch on your skin. They don't elicit any particular feeling when stimulated.

Tactile afterimage

If you touch something hot, then after warm water doesn't seem hot to touch than if you touch that warm water directly. Observed for texture(rough vs smooth)>

local anaesthesia

It involves numbing a specific part of the body to prevent any feeling of pain during surgical procedures. This proves that receptors/fibres provide information about the external world.

The somatosensory system

It is the part of the sensory system concerned with the conscious perception of touch, pressure, pain, temperature, position, movement, and vibration, which arise from the muscles, joints, skin, and fascia Divided into two forms: Detection of mechanical stimuli Detection of pain and temperature.

Interoception

It is the sense responsible for detecting internal regulation responses, such as respiration, hunger, heart rate, and the need for digestive elimination.

Markel disk

Located in the epidermis. Found in fingertips, lips, hand. They provide information on pressure, position, and deep static touch features such as shapes and edges.

Detection of mechanical stimuli

Mechanical receptors sense every stimuli that you experience in the world. Mechanical force is created between the skin and the stimuli.

Three different types of nociceptors in skin are:

Mechanosensitive mechanothermal polymodal(responsive to all different stimuli)

Pecinian corpuscle

Onion like capsule found in gut, skin. The capsule acts like a filter that allow rapid, high frequency disturbances to activate the nerve ending. sensitive to transient vibration and pressure applied to the skin. Pacinian corpuscles are only able to tell when pressure has begun and ended. For example, when you just press your finger against your skin or just let go.

Proprioceptor

Receptors located in the muscles, joints and other deep structures detect mechanical forces generated by the musculoskeletal system. it provides information about joint angle, muscle length, and muscle tension, which is integrated to give information about the position of the limb in space

Nociceptor

Receptors that detect pain. Faster AP with myelinated axon. The experience of sudden pain--> myelinated axon The experience of gradual pain--> unmylinated axon

Thermoreceptor

Receptors that detect temperature. physiological zero(sensation neither felt warm nor cold). When we say something cold, our skin senses something colder than the physiological of zero. The difference in temperature(hot vs cold) creates the sense of hotness.

Mechanoreceptor

Receptors that detect touch or sound.

visceral pain

The pain we feel when our internal organs are damaged or injured e.g. kidney, stomach. Cause referred pain: Pain felt at a site other than where the cause is situated. e.g. pancreas cause pain on the back.

The importance of touch

Touch is related to emotion,thus important. especially between mother an babies.

Active vs passtive touch

We actively touch something to try and figure out what the object is. Actively touching allows you to identify the object much accurately than someone putting the object on your hand.

Rapid adapting

When you touch something initially, both rapid and slow fibres responding to the stimuli. -Meissner corpuscles - Pacinian corpuscles e.g. When you touch an insect, both rapid and slow fibres detecting the skin of the insect.

How we sense something?

all receptor detect a particular stimuli, and receptor takes some type of energy and transport it into action potential to generate electrical current that is interpreted by the brain. Brain detects sense not the receptor itself detects the sense.

Joint receptor

provide information on joint position and movement.

Detection of external stimuli

uses cutaneous (skin) and subcutaneous (under the skin) mechanoreceptors at the body surface.

Tactile adaptation

when I first touch something, there are more receptors of the cells detecting the objects. But fade away after touching it many times. Only half of the receptors responding to the stimulus after multiple exposure to the object.