Lecture 2 Flashcards
What are the types of somatic sensations?
1) Mechanoreceptive: detect mechanical displacement
2) Thermoreceptive: detect hear and cold (changes in stimulus)
3) Nociceptive: detect pain and tiddue damage
What are the two types of mechanoreceptors?
1) Tactile: touch, pressure, vibration, tickle, itch
2) Proprioception (position): static position and dynamic position (rate of change)
What are the types of tactile receptors?
1) Free nerve endings (Aδ and C)
2) Meissner‘s corpuscles (Aβ)
3) Merkel’s discs (Aβ)
4) Hair end organ
5) Ruffini’s end organ
6) Pacinian corpuscles
7) Golgi tendon apparatus and muscle spindles
8) Iggo dome receptors
What do free nerve endings detect? Where are they found?
Touch and pressure; everywhere in the skin and tissues.
What do Meissner‘s corpuscles detect? Where are they found?
Movement of light objects over skin and low frequency vibrations; hairless skin (glabrous skin), fingertips, and lips down in the epidermis.
Which tactile receptors are encapsulated (rapidly adapting) receptors?
1) Meissner‘s corpuscles
2) Pacinisn corpuscles
3) Merkel’s discs
4) Ruffini’s corpuscles
What do Merkel’s discs detect? Where are they found?
“Steady state” and touch; found on hairy and hairless (glabrous) skin.
Which tactile receptors respond rapidly at first and then slowly adapt?
Merkel’s discs
What do hair end organs detect? Where are they found?
Acts rapidly to detect movement of hair; found around hair shafts.
What do Ruffini’s end organs detect? Where are they found?
Changes in pressure and joints formation; found deep in the dermis
Which tactile receptor is slowly adapting and responds to continual deformation of the skin and joint rotation?
Ruffini’s end organ
What do Pacinian corpuscles detect? Where are they found?
High frequency vibration, pressure, and other rapid changes in the skin; found down in the dermis.
Which tactile receptor is rapidly adapting, stimulated only by rapid movement, and looks like onion rings?
Pacinian corpuscle
Where are golgi tendon apparatus and muscle spindles found?
Skeletal muscles
Which receptors transmit signals in type Aβ nerve fibers at 30-70 m/s?
1) Meissner’s corpuscles
2) Hair receptors
3) Pacinian corpuscles
4) Ruffini’s end organs
Which receptors transmit signals in type Aδ nerve fibers at 5-30m/s and some C at 0.5-2m/s?
Free nerve endings
Why is fine touch transmitted very fast through Aβ or Aα fibers?
Because the faster the rate of transmission, the more critical the information.
Almost all sensory information enters the spinal cord through which roots?
The dorsal roots
What are the two pathways for the transmission of sensory information?
1) Dorsal column-medial lemniscal system
2) Anterolateral (spinothalamic) system
The dorsal column medial lemniscal system’s tract ascends in the:
Dorsal column of the spinal cord and forms medial lemniscus
The dorsal column medial lemniscal system contains ____(small/medium/large) ____(myelinated/unmyelinated) fibers for ____(slow/fast) transmission with which kind of fibers?
Large; myelinated; fast (30-110m/s); Aβ
What is the difference between spatial and temporal?
Spatial: position/space
Temporal: time
What does spatial fidelity mean?
The fibers come from each part of the body and are arranged in a highly organized way.
What does temporal fidelity mean?
Faithfulness
The dorsal column medial lemniscal system has a high degree of what?
Spatial orientation that is maintained throughout the tract.
The dorsal column medial lemniscal system transmits information rapidly with a high degree of:
Spatial and temporal fidelity
What are the modalities of the dorsal column medial lemniscal system?
1) Fine touch & fine pressure: because rapidly transmitting neurons.
2) Vibration and weight discrimination
3) Two point discrimination: the ability to distinguish if the stimulus is at 2 different points or not.
4) Stereognosis: determine shape without sight (braille)
5) Conscious proprioception: sensation of position
What is the pathway of the dorsal tract? (Up to the second order neuron)
1) The afferent neurons (first order neurons) enter the spinal cord through the posterior horn (their cell bodies are found in the dorsal root ganglia)
2) The first order neurons send their afferent fibers through two dorsal columns (Fasciculus gracilis, Fasciculus cuneatus)
3) They ascend until they reach their respective nuclei in the medulla (cuneatus nucleus and gracilis nucleus) where each tract synapses in its nucleus with the second order neuron.
The dorsal tract consists of two parts:
1) Fasciculus gracilis (medially): Transmits information from the lower part of the body
2) Fasciculus cuneatus (laterally): Transmits information from the upper part of the body
Which two tracts are found on both sides of the spinal cord and then cross over?
1) Fasciculus gracilis
2) Fasciculus cuneatus
The information that comes from the right side of the body goes to the ___(right/left) side of the cortex.
Left
What is the pathway of the dorsal tract? (After the second order neuron and until the third order neuron)
1) The second order neuron decussates (crosses over the midline) in the medulla oblongata and ascends as medial lemniscus to the thalamus.
2) In the thalamus, it goes to the ventrobasal complex to synapse in VPL (ventral posterolateral nucleus) with the third order neuron.
What is the pathway of the dorsal tract? (After the third order neuron)
The third order neuron ascends to the primary somatosensory cortex.
The ventrobasal complex consists of two parts:
1) Ventral posterolateral (VPL)
2) Ventral posteromedial (VPM)
What are the three sulci of the brain?
1) Central sulcus
2) Lateral fissure
3) Parieto-occipital notch
Which lobe is anterior to the central sulcus?
Frontal lobe
Which lobe is posterior to the central sulcus?
Parietal lobe
Which lobe is inferior to the lateral fissure?
Temporal lobe
Which lobes does the parieto-occipital notch separate?
The parietal lobe from the occipital lobe
In the parietal lobe, posterior to the central sulcus, what do we have?
Postcentral gyrus
What is the postcentral gyrus?
The primary somatosensory area which has a very high level of organization
What is a gyrus?
The area between two sulci
The right side of the cortex represents the ____ (right/left) side of the body. This means it is:
Left; contralateral
The area of cerebral cortex that represents any part of the body is proportional to:
The number of receptors in that area.
Which area of the cortex is bigger: the hand or the leg area? Why?
The hand, because the number of receptors in the hand is greater than the number of receptors in the leg.
What does the size of the cortical region representing a body part depend on?
1) Density of the receptors in that part
2) Sensory impulses received from that part
Which area of the cortex is bigger: the face or the trunk area? Why?
The face, because the number of receptors in the face is greater than the number of receptors in the trunk.
What is a dermatome?
An area of the skin that is mainly supplied by branches of a single spinal sensory nerve root.
The nerves of the nervous system develop from:
The ectoderm
The soft tissue develops from:
The mesoderm
The epithelium develops from:
The endoderm
Which spinal segments supply the medial aspect of the hand and the heart?
C8, T1, T2
Afferent sensory fibers from the appendix are carried on the sympathetic nerve fibers to enter the spinal cord at ___ which corresponds to ___.
T10; Umbilical dermatome.
