Lecture 24 Flashcards
What is skin?
our heaviest organ and protects us by keeping damaging agents from
penetrating the body
What is the epidermis?
outer layer of the skin, which is made up of dead skin cells
Describe the dermis
below the epidermis and contains mechanoreceptors that
respond to stimuli such as pressure, stretching, and vibration
Describe the Merkel Receptor
(one of two types of)
mechanoreceptors located close to surface of the skin
- Have relatively small cutaneous receptive fields
- They fire continuously while stimulus is present (hence
‘slowly adapting’, or ‘SA1’) - Responsible for sensing fine details
Describe the Meissner corpuscle
- Meissner corpuscle are the other kind of
mechanoreceptor located close to the skin’s surface
(and also have relatively small cutaneous receptive
fields) - These fire only when a stimulus is first applied and
when it is removed (hence ‘rapidly adapting’, or ‘RA1’) - Responsible for controlling hand-grip
Describe Ruffini cylinder
- Ruffini cylinder are one (of two types of)
mechanoreceptors located deeper in the skin - They fires continuously to stimulation (hence ‘SA2’)
- Associated with perceiving stretching of the skin
Describe Pacinian corpuscles
- Pacinian corpuscles fire only when a stimulus is first
applied and when it is removed (hence ‘RA2’) - Associated with sensing rapid vibrations and fine
texture
Describe a challenge for the cutaneous system
One major challenge for the cutaneous
senses is the distance the signals from
these receptors must travel (to the brain),
as compared to other senses with more
‘localized’ receptors (e.g. the eye, the
ear, etc.)
- Two major pathways for these signals
exist in the spinal cord (with signals
entering via the dorsal root) - These crossover to the opposite side of
the body and synapse in the thalamus (in
the ventrolateral nucleus), i.e.
contralateral wiring
What is the medial lemniscal pathway?
The medial lemniscal pathway
consists of large fibres that carry
proprioceptive and touch information,
and send high-speed signals
What is the spinothalamic pathway?
The spinothalamic pathway consists
of smaller fibres that carry
temperature and pain information
How do somatosensory signals travel?
From the thalamus to parietal lobe, specifically the somatosensory
receiving area (S1) (and possibly directly to the secondary receiving
area, S2)
What is the homunculus?
Body map
What is somatotopy?
Concept of somatotopy (like
retinotopy and tonotopy)
- Plasticity in neural functioning
leads to multiple homunculi and
changes in how cortical cells are
allocated to body parts
What is two point threshold?
minimum separation needed between two points to
perceive them as being separate/distinct
What is grating acuity?
placing a grooved stimulus on the skin and asking the
participant to indicate the orientation of the grating
What is raised pattern identification?
can also use various raised patterns (like
Braille) to determine the smallest size that can be identified
What is a corpuscle?
- The corpuscle (a minute body or cell in an
organism) structure surrounding Pacinian receptors
is responsible for the selective response to vibration - It only transmits repeated pressure (like vibration)
to the actual receptor, not continuous pressure - Can be likened to an onion in form
- Consists of a series of layers, with fluid between
each layer
What is surface texture?
the physical surface created by peaks and valleys
on a given material
What are spatial cues?
determined by the size, shape, and distribution of surface elements
What are temporal cues?
determined by the rate of vibration as skin is moved across finely textured surfaces
Describe ventral posterior nucleus
Neurons in the ventral posterior nucleus
have centre-surround receptive fields
(like in the LGN)
