Topic 3: senses - touch

Question 1

What are the 3 senses touch is split into?

Answer 1

1) Pressure: stimulus is physical pressure on skin
2) Temperature: stimulus is change of temperature on skin
3) Pain: stimulus intense enough to cause tissue damage = pressure/temp/electrical/chemical

Question 2

What are the reasons for splitting touch into 3 senses?

Answer 2

• Each sense responds to distinct class of stimuli
• Each sense has distinct set of receptors
• Each sense experiences differ phenomenologically when stimulated

Question 3

What are the 3 layers of skin?

Answer 3

• Epidermis
• Dermis
• Hypodermis

Question 4

Describe the epidermis

Answer 4

• From greek word for over
• Outermost layer
• Waterproof + protective layer over body = barrier from infection
• Made of stratified squamous epithelium + basal lamina

Question 5

Describe the dermis

Answer 5

• Made of epithelial tissue
• Cushions body from stress+ strain
• Tightly connected to epidermis via basement membrane
• Nerve endings = sense of touch + heat

Question 6

Describe the hypodermis

Answer 6

• Not part of skin
• Below dermis of cutis
• Purpose = attach skin + bone/muscle + supply with blood vessels/nerves

Question 7

Describe tactile receptors and function

Answer 7

• Nerve fibers + nerve corpuscles = target detect stimuli on skin
• Different sensory receptors = sensitive to particulr stimuli = when detect = generate nerve impulses
• Impulses -> spinal cord = lower part of body
• Impulses -> brain via cranial nerves = upper body/face

Question 8

Where in the brain are stimulations felt?

Answer 8

• Sensory cortex
• If right side of body = left sensory cortex = parietal lobe
• If left side of body = right sensory cortex = parietal lobe

Question 9

Describe Merkel cells

Answer 9

• Bottom of epidermis
• Connected to Merkel cell disks
• Only nerve fiber in epidermis = sensitive to light touch
• Provide info on = pressure + position + shape

Question 10

Describe Meissner corpuscles

Answer 10

• Mechanoreceptors = detect mechanical stimulus
• Small corpuscles located surface of dermis
• Transmit = fine + discriminative touch + vibrations

Question 11

Describe Pacinian corpuscle

Answer 11

• Deep dermis/hypodermis = large receptors
• Made of many layers + Schwann cells
• Sense vibration + pressure
• Connected to sensory neurons = take info to brain as pressure is detected

Question 12

Describe thermoreceptors

Answer 12

• 2 types = detect heat/cold
• Free nerve endings in dermis

Question 13

Describe pain receptors

Answer 13

• AKA nociceptors
• Detect stimulus by extent of pain
• Also free nerve endings in dermis = dermis sensitive to pain not epidermis