Signal Processing and The Somatic Senses Flashcards
What do the sensory pathways convey?
The type and location of the sensory stimulus.
What determines the “type” of sensory pathway taken?
The type of receptor activated.
What determines the “location” of the sensory pathway?
The brain has a map of the location of each receptor.
How does the neuron travel through the sensory pathway?
Neuron >receptor> afferent neuron> spinal cord/brainstem> second order neuron> thalamus>third order neuron>cortex
Why do most sensory pathways project to the thalamus?
The thalamus modifies and relays information to cortical centers.
Where do the equilibrium pathways project to?
cerebellum
The olfactory pathway projects from the now to where?
The olfactory cortex
What is the definition of somatic sensation?
Sensation from the skin, muscles, bones, tendons, and joints.
What initiates the somatic sensation?
activation of a number of distinct somatic receptors that response specifically to changes in heat, cold, touch, pressure, limb position, movement, or pain.
What does the somatic sensation enable the body to feel?
to feel, ache, and chill
What is the somatic sensory system is responsible for?
Touch and pain.
Why is the somatic sensory system different from other systems?
It has receptors that broadly distributed and responds to many stimuli.
What are the 5 somatic special senses?
Vision, Hearing, Taste, Smell, Equilibrium.
What are the general somatic senses?
Touch, temperature, pain, itch, proprioception.
What is proprioception?
It is the sense of the orientation of one’s limbs in space.
What are three ways somatic senses classified?
1) Mechanoreceptic somatic sense, thermoreceptive senses, and the pain sense.
What is exteroreceptive sensations?
A way to classify somatic sense. Sensations on the surface of the body.
What is proprioceptive sensations?
A way to classify somatic sense. It is the physical state of the body.
What are Visceral Sensations?
A way to classify somatic senses. It is sensation in the internal organs: heart, liver, lungs.
What are deep sensations?
A way to classify somatic senses. It is “deep” pressure, pain, and vibration.
What are the types of skin?
Hairy and glabrous.
What is glabrous skin?
Hairless skin like your palms
What are the layers of the skin?
Epidermis and dermis
Which is the outer layer of the skin?
The epidermis
What is the inner layer of the skin?
The dermis
What is the function of the skin?
Protective, prevents evap of body fluid, and provides direct contact with world.
What are mechanoreceptors?
Most somatosensory receptors
What is the sensory pathway for transmitting somatic signals into CNS?
Neuron enters the spinal cord > through the dorsal column > dorsal column nuclei, medial meniscus, medula, the thalamus, and primary somatosensory cortex.
Explain the dorsal column-medial lemniscal pathway?
Mechanoreceptors or proprioceptors> first order neurons (Afferent) through the dorsal columns> trigeminal nerve> decussation of medial meniscus> dorsal column nuclei in medula oblongata>second order neuron> thalamus>third order neuron>primary somatosensory cortex
Explain the Anterolateral system?
nociceptors or thermoreceptors> first order neuron (Afferent) go through the anterolateral quadrant> through the leisure’s tract> through the medulla oblongota> second order neuron > thalamus > third order neuron > primary somatosensory cortex.
In the dorsal column-medial lemniscal system requires touch sensations to be what?
a high degree of localization of the stimulus.
In the dorsal column-medial lemniscal system requires touch sensations requiring transmission of what?
fine gradations of intensity.
What are phasic sensations in the dorsal column-medial lemniscal system?
vibratory sensations
In the dorsal column-medial lemniscal system the sensations that signal movement against what?
The skin
Dorsal column-medial lemniscal system deals with position sensations from what?
the joints
The dorsal column medial lemniscal deals with pressure sensations related to what?
fine degrees of judgment of pressure intensity.
What does the anterolateral system?
- Pain
- Thermal sensations
- Crude touch and pressure sensations
- Tickle and itch sensations
- Sexual sensations
How does the dorsal column-medial lemniscal system carry signals?
Carry signals upward tot he medulla of the brain
How does the anterolateral system carry signals?
Carry signals to the opposite site.
Dorsal column medial lemniscal system has a high degree of what?
spatial orientation of the nerve fibers-
Why does the dorsal column medial lemniscal system has such a high degree of spatial orientation?
To transmit signals rapidly and with temporal and spatial fidelity.
The anterolateral system has less what than the dorsal column medial lemniscal?
Less spatial orientation of the nerve fibers.
Why does the anterolateral system has less spatial orientation of the nerve fibers?
it transmits signals less rapidly and with less temporal and spatial fidelity.
The anterolateral system transmits a broad what?
spectrum of sensory modalities.
Who was Brodmann?
histologist that made a map of human cortex and divided it into 50 distinct areas.
What were the areas that Brodmann divided the human cortex into called?
Brodmann’s Area
Bordmann’s area was divided into 50 distinct sections based on what?
areas based on histological, structural differences.
How has mapping been carried out in intact humans?
PET and fMRI (Functional)
In Brodmann’s area which areas constitute the primary somatosensory area I?
Areas 1,2,3
In Brodmann’s area which areas constitute the secondary somatosensory area II?
40
In Brodmann’s area which areas constitute the somatosensory association area?
areas 5 and 7
Ablation of SI area in animals cause what?
Localization but still touch is felt.
Loss of stereognosis
loss of fine touch
loss of proprioception
What is stereognosis?
inability to judge size or shape of the object
Where is the somatosensory area II located?
Superior wall of the sylvan fissure, that separate the temporal lobe from the frontal. and parietal
Why is the SI more important than the SII?
Removal of parts of SII has no apparent effect on neurons in SI. Therefore SI is more important.
Somatosensory association area receives signals from where?
- SomatosensoryareaI
- Thalamus
- Visualcortex
- Auditorycortex
Where is the somatosensory association area located?
Located in parietal lobe behind area SI
Which brodmann area is the somatosensory association area?
5 and 7 of cerebral cortex
What is amorphosynthesis?
Person looses the ability to recognize objects felt on the apposite side of the body, he looses the sense of form of his own body on the opposite side also
What are the 6 layers of the cerebral cortex?
- Molecular Layer
- External Granular Layer
- External Pyramidal Layer
- Internal Granular Layer
- Internal Pyramidal Layer
- MulFform Layer
What does each vertical column of the sensory cortex detect?
a different sensory spot on the body with a specific sensory modality
Each layer of the sensory cerebral cortex has vertical columns, what do each column have?
10,000 neuronal cell bodies.
Sensory cortex contain 6 separate layers of what?
neuron arranged in vertical columns.
Incoming sensory signals excites which neuronal layer of the sensory cortex?
The IV first
After incoming sensory signal excites the IV layer what happens?
the signals spreads both towards the surface of the cortex & towards deep layer.
What does layers 1 and 2 receive?
diffused signals, nonspecific input.
Layers II and III send what?
axons to cerebral cortex on the opposite side of the brain
What is the region of the brain that layer 2 and 3 sends the axons to?
The corpus callosum
Where does layers V and VI of the sensory cortex sends its axons?
to the deeper part of the brain (from V to basal ganglia, brain stem, spinal cord.)
Layer VI axons extend to what region of the brain?
the thalamus
Compare the amount of cold receptors to warm spots?
Cold receptors are 4-10 times more than warm sensitive spots.
Cold receptor responds to what degrees?
10-38 degrees C
Warm receptors respond to what degrees?
from 30-45 degrees C
Afferent from cold receptors?
Aδ & C fibers
Afferent from Warm receptors?
C Fibers
How is temperature sensation carried?
via lateral spinothalamic tract
Pain receptors are also known as what?
Noiciceptors
What do pain receptors or nociceptors have?
Free nerve endings
What are the characteristics of Aδ (myelinated)?
2 – 5 μm.in diameter, conduction velocity – 12 – 30 m/sec.
What is usually for fast pain (sharp and localized)?
Aδ (myelinated)
What are characteristics of C fibers?
0.4 – 1.2μm. in diameter,
conducFon velocity – 0.5 – 2 m/sec
What is usually for slow pain dull and diffuse?
C Fibers
Where do Aδ & C fibers terminate?
In the dorsal horn.
Pain is carried via what?
lateral spinothalamic tract.