Lec 03- General Sensory Mechanisms I Flashcards
What are the 5 basic types of sensory receptors?
- mechanoreceptors
- thermoreceptors
- nociceptors
- electromagnetic receptors (photo)
- chemoreceptors
What do mechanoreceptors include?
both free and encapsulated endings receiving skin tactile sensibilities
What are the expanded tip endings of mechanoreceptors that receive skin tactile sensibilities?
- Merkel’s discs
- Other varients
What are the encapsulated endings of mechanoreceptors that receive skin tactile sensibilities?
- Meissner’s corpuscles
- Kraus’ corpuscles
What are the spray endings of mechanoreceptors that receive deep tissue sensibilities?
Ruffini’s corpuscles
What are the encapsulated endings of mechanoreceptors that receive deep tissue sensibilities?
- Pacinian corpuscles
- Other variants
What are the mechanoreceptor for hearing?
sound receptors of cochlea
What are the mechanoreceptor for equilibrium?
vestibular receptors
What are the mechanoreceptor for arterial pressure?
baroreceptors
What are the receptors for thermoreceptors?
cold and warm receptors
What are the nociceptors?
free nerve endings responding to pain
What are the electromagnetic receptors?
Rods and cones of the eye for vision
What are the chemoreceptors?
- taste
- smell
- arterial oxygen
- osmolarity
- blood CO2
- blood glucose, amino acids, and FA
What is differential sensitivity?
each type of receptor is highly sensitive to one type of stimulus and is almost non-responsive to other types
What is modality?
refers to each of the principal types of sensation
touch, pressure, …
What is the labeled line principle?
the specificity of nerve fibers for transmitting only one modality of sensation
What are the 4 mechanisms of stimulation for receptors?
- mechanical deformation
- application of a chemical
- temperature change
- electromagnetic radiation
What are the 3 characteristics of tonic receptors?
- Slow adapting
- Detect continuous stimulus strength
- Transmit impulses as long as stimulus is present
What are the 5 types of tonic receptors?
- Muscle spindles
- Golgi tendon organs
- Macula and Vestibular receptors
- Baroreceptors
- Chemoreceptors
What are the 4 characteristics of phasic receptors?
- Rapidly adapting
- Do not transmit a continuous signal
- Stimulated only when stimulus strength changes
- Transmit information regarding rate of change
What are Type A nerve fibers?
- Subdivided into a,b,y,d
- Large and medium myelinated fibers of spinal nerves
What are Type C nerve fibers?
- Small, unmyelinated fibers
- Conduct signals at low velocity
- Make up more than half of all sensory fibers in most peripheral nerves and all postganglionic autonomic fibers
Which nerve fibers are from annulospiral endings of muscle spindles?
Group Ia
Type Aa
Which nerve fibers carry pain, itch, temperature, and crude touch?
Group IV
Type C
Which nerve fibers are from cutaneous tactile receptors and flower-spray?
Group II
Type Ab,y
Which nerve fibers are from Golgi tendon organs?
Group Ib
Type Aa
Which nerve fibers carry pricking pain, temperature, and crude touch?
Group III
Type Ad
What happens when using progressively greater numbers of fibers?
Signal strength is increased
What is the receptor field for a given fiber?
the entire cluster of nerve endings from one pain fiber that covers an area of skin
Where is the number of nerve endings large?
in the center of the receptor field
Number is reduced in the periphery
Nerve endings from one pain fiber ______ those of other pain fibers
overlap
What is temporal summation?
increasing signal strength by increasing the frequency of nerve impulses in each fiber
What are examples of neuronal pools?
- cerebral cortex
- basal nuclei
- thalamic nuclei
- cerebellum
- mesencephalon
- pons
- medulla
- gray matter of spinal cord
What is a neuronal pool?
all the neurons in an area that you are studying
What is the stimulatory field of neuronal pool?
neuronal area within the pool that is stimulated by each incoming nerve fiber
Where do terminals for each input fiber lie?
on the nearest neuron in its field
What is the discharge zone?
all output fibers stimulated by the incoming fiber
What are facilitated/inhibition zones?
- Neurons further from the discharge zone
- Facilitated
- NOT excited
Are facilitated/inhibition zones inhibitory or excitatory?
depends on the input fiber
What are diverging neuronal pathways?
- Result = Amplification of initial signal
- Allow transmission of original signal to separate areas
What are converging neuronal pathways?
- Multiple input fibers converge onto a single output neuron
- Input fibers can be from one or more separate sources
What are reverberatory/oscilatory circuits?
- Caused by (+) feedback within neuronal circuit
- May discharge repetitively for a long time once it is stimulated
What are the 3 types of somatic senses?
- mechanoreceptive
- thermoreceptive
- pain
Where do the somatic senses collect sensory information from?
all over the body
What are the 5 types of special senses?
- vision
- hearing
- smell
- taste
- equilibrium
Where are the exteroreceptive sensations from?
the surface of the body
What are the 4 proprioceptive sensations?
“physical state of the body”
- position sensations
- muscle and tendon sensations
- pressure sensations
- equilibrium
What are the 3 deep sensations?
- deep pressure
- deep pain
- deep vibrations
What somatic senses include both tactile and position senses that are stimulated my mechanical displacement of some tissues of the body?
mechanoreceptive somatic senses
What are the 3 Ascending neuronal pathways?
- primary sensory neurons
- secondary neurons
- tertiary neurons
Where do the primary sensory neurons extend from and go through?
- From external receptors
- Through dorsal roots of spinal cord
Which ascending pathway neurons make up tracts in the spinal cord and brainstem?
secondary neurons
What do the tertiary neurons extend from and travel through?
- From thalamus
- To primary sensory cortex
- To post-central gyrus
- Through internal capsule
What are the 2 systems used for conscious perception (2* neurons)?
- Spinothalamic system
- Medial Lemniscal system
What are the 4 systems used for unconscious perception?
- Spinocerebellar (cerebellum)
- Spino-olivary (medulla)
- Spinotectal (roof of midbrain)
- Spinoreticular (brainstem/reticular system)
What are the 2 tracts of the spinothalamic system?
- Lateral spinothalamic tract
- Anterior spinothalamic tract
What does the Lateral Spinothalamic tract carry?
pain and temperature
In the Lateral Spinothalamic tract, primary fibers ascend/descend 1-2 spinal cord segments before ____________
synapsing with secondary fibers
In the Lateral Spinothalamic tract, what do secondary axons decussate through?
anterior gray and white commisures
ONLY 2* neurons can decussate
__________ axons make up the lateral spinothalamic tract traveling in the lateral column of the spinal cord
secondary
In the Lateral Spinothalamic tract, what tract joins the secondary fibers in the brainstem?
trigeminothalamic tract
In the Lateral Spinothalamic tract, what is the trigeminothalamic tract responsible for?
paina and temperature from face and teeth
In the Lateral Spinothalamic tract, where do the secondary fiber collaterals project to?
reticular formation
What do the reticular formation do?
stimulate wakefulness and consciousness
In the Lateral Spinothalamic tract, where do the secondary fibers project to?
ventral posterolateral (VPL) nucleus of thalamus
In the Lateral Spinothalamic tract, what do the secondary fibers synapse with in the VPL?
tertiary fibers
In the Lateral Spinothalamic tract, where do the tertiary fibers (corticopetal fibers) synapse?
in post-central gyrus
What are the sensory areas of the post-central gyrus?
1, 2, 3
In the Lateral Spinothalamic tract, what fibers form part of the internal capsule (myelinated fiber tracts)?
tertiary fibers
What 4 things does the Anterior Spinothalamic tract carry?
- light touch (crude touch)
- pressure
- tickle
- itch
In the Anterior Spinothalamic tract, the primary neurons may ascend __________ spinal cord segments before synapsing with secondary neurons.
8-10
In the Anterior Spinothalamic tract, where do the secondary fibers decussate?
in anterior gray or white commissures
In the Anterior Spinothalamic tract, the secondary fibers ascend to synapse with tertiary fibers in ____________________
VPL nucleus of thalamus
In the Anterior Spinothalamic tract, where do the tertiary fibers ascend through to the primary sensory cortex?
through internal capsule
What are the 3 differences between the Lateral and Anterior Spinothalamic tract?
- level of synapse
- type of sensation
- location of secondary fibers
What is another name for the Medial Lemniscus System?
Posterior Column System
What does the Medial Lemniscus System carry?
Sensations for:
- Two-point sensation (fine touch)
- Pressure
- Vibration
In the Medial Lemniscus System, where do the primary fibers ascend?
entire length of spinal cord
In the Medial Lemniscus System, what do the primary fibers synapse with?
secondary neurons in the medulla
What are the 2 secondary fibers in the medulla for the Medial Lemniscus System?
- Fasciculus gracilis (narrow)
- Fasciculus cuneatus (wedge shaped)
What do the fibers of the fasciculus gracilis convey in the Medial Lemniscus System?
sensations from below mid thoracic level
ex: lower limbs, abdomen…
What do the fibers of the fasciculus cuneatus convey in the Medial Lemniscus System?
- sensations from above mid thoracic level
- proprioceptive sensation from arms to cerebellum
Where do the secondary fibers of the Medial Lemniscus System decussate?
in the medulla
Where do the secondary fibers of the Medial Lemniscus System ascend to synapse?
in VPL of thalamus
What do the tertiary fibers of the Medial Lemniscus System ascend through?
internal capsule to primary sensory cortex
