Lecture 6: sensory systems Flashcards
Sensation can be categorized into what 2 main types
Conscious and nonconcious
What are the 2 main divisions of conscious sensation
Exteroreceptiom and proprioception
What are the 2 divisions of the non conscious sensation
Enteroreception and proprioception
True of false: proprioception can be conscious and non conscious
True
What is general external stimuli called
Exteroreceptiom
What is general internal stimuli called
Enteroreception
Explain exteroreception
External stimuli
Eg: sensations detected by cutaneous receptors
Explain enteroreception
Internal stimuli
Eg. visceral sensation related to homeostasis (bp, hr)
True or false: external stimuli is felt by enteroreceptors
False, by cutaneous receptors
What does kinesthesia mean
Body’s location and movement in space
Explain concious sensation
Pathways to cerebral cortex (typically via thalamus)
awareness and ability to move body parts without visual cues
Concious sensation have pathways to cerebral cortex or cerebellum
Cerebral cortex
Concious sensations have pathways to the cerebral cortex via what structure typically
Thalamus
Explain non conscious sensation
Pathways to the cerebellum
Coordination of complex movements (eg ealking, riding a bike)
Non conscious sensation has pathways to cerebral cortex or cerebellum
Cerebellum
Somatosensatio. Includes what types of modalities
Vibration
Light touch
Pain
Temp
Proprioception
What are some general categories of receptors in somatosensatio
Mechanoreceptors
Nociceptors
Thermoreceptors
What do mechanoreceptors detect in terms of internal stimuli
Proprioception, stretch in blood vessels
What do mechanoreceptors detect in terms of external stimuli
Light touch, vibration, stretch , pressuee
What do nociceptors detect
Damaged (or potentially damaged) tissue and associated chemical changes (ex, burns)
What do thermoreceptors detecr
Relative changes in temperature (within normal range)
In the change in temp is outside the normal range, which receptor detects it
Nociceptors
What are the 6 cutaneous receptors
Free nerve ending
Lamellar (pacinian) corpuscle
Type 1 cutaneous mechanoreceptor (merkel disk)
Tactile/touch receptor (Meissener corpuscle)
Type 2 cutaneous mechanoreceptos (ruffini corpuscle)
Hair follicle receptor
What 3 cutaneous receptors are un encapsulated
Free nerve endings
Type 1 cut mechanoreceptor (merkel)
Hair follicle receptor
What 3 cutaneous receptors are encapsulated
Lamellar (pacinian) corpuscle
Tactile/touch (meissner) corpuscle
type 2 cuteanous mechanoreceptors
Tru or false : if a receptor is encapsulated (connective tissues surrounding it) , it is not as sensitive to light sensations
True
Explain free nerve endings
Unencapsulated
Detect pain and temp
Which cut receptor is Unencapsulated and
Detect pain and temp
Free nerve ending
True or false, free nerve endings are located deep
False, they go into the epidermis and are close to surface
Explain lamellar (pacinian) corpuscle
Encapsulated
Detect high frequency vibration and sudden changes in pressure
Which receptor is Encapsulated and
Detect high frequency vibration and sudden changes in pressure
Lamellar corpuscle
Explain type 1 cutaneous mechanoreceptor (merkel)
Unencapsulated
Sense light touch and pressure
Which receptor is Unencapsulated and
Sense light touch and pressure
Type 1 cutaneous mechanoreceptor (merkel)
Explain tactile/touch corpuscle (meissner)
Encapsulated
Sense light and low frequency vibration
Which receptor is Encapsulated and
Sense light and low frequency vibration
Tactile/touch corpsucle (meissner)
Wxplain type 2 cutaneous mechanoreceptor (ruffini)
Encapsulated
Sense stretch and sustained pressure
Which receprr is. Encapsulated and
Sense stretch and sustained pressure
Type 2 cutaneous mechanoreceptor (ruffini)
Explain hair follicle receptor
Unencapsulated
Sense movement on skin surface that disturbs hair
Which receptor is Unencapsulated and
Sense movement on skin surface that disturbs hair
Hair follicle receptor
what are the two encapsulated proprioceptors
muscle spindles and golgi tendon organs
How many neuron pathways are in typical somatosensory pathways
Primary (1o; first order) neuron = cell bodies in dorsal root ganglia
• Secondary (2o; second order) neuron= axons decussate
• Tertiary (3o; third order) neuron=cell bodies in thalamic nuclei
Where are the cell bodies of primary neutrons located
Cell bodies in dorsal root ganglia
Where do the axons decussate
At secondary neuron
Where are the cell bodies of tertiary neutrons located
cell bodies in thalamic nuclei
true or false: tertiary neutron cell bodies are located in the dorsal root ganglia
false, in the thalamic nuclei
the somatosensory pathways are broadly divided into what 2 systems
1) dorsal Column system
2) anterolateral sustem and non conscious proprioception pathways
the dorsal column system is mainly responsible for what sensations
fine touch, vibration, and conscious proprioception
what is the pathways of the dorsal column system
dorsal column-medial leminscus
the anterolateral system and non conscious proprioception pathways are mainly responsible for what sensations
pain, temperature, crude touch, and non conscious proprioception
be able to recognize general areas where the different somatosensory
the dorsal and ventral spinocerebellar pathways are responsible for concious or unconscious sensation
unconscious
what are the spinocerebellar pathways
dorsal and ventral spinocerebellar pathways
what are the spinothalamic pathways
lateral and anterior spinothalamic
which pathways take the signal rom spine to cerebellum
dorsal and ventral spinocerebellar pathways
which pathways take the signal from spine to thalamus
lateral and anterior spinothalamic
primary neurone are what type of neurons
pseudo unipolar
where is the location of the cell body is pseudounipolar
centrally
primary neurone synapse with secondary neurone where (2 areas)
in the brain stem nucleus or dorsal horn (depending on the pathway)
at the end of the primary neurone what receptors are tehre
cutaneous
which are the neurons that cross the midline (decussate)
secondary neuron
the synapse between secondary and tertiary neurons always happens where
thalamus
secondary and tertiary neurons are what type
multipolar
what is the general pathways for the dorsal column medial lemiscus
1) primary sensory neuron enters doorsla horn (cell. body in dorsal root ganglion)
2) ipsilateral dorsal (post column)
=t6 above: fasciculus cuneatus,
=below T6 :fasciculus gracilis
3) synapse with secondary neurone (either in nucleus cuneatus or gracilis)
4) decussation (internal arcuate fibers)
5) medial lemniscus
6) synapse with tertiary neurone (in VPL or VPM nucleus of thalamus)
7) internal capsule (posterior limb)
8) corona radiata
9) primary sensory gyrus (post central gyrus)
in the DCML, primary sensory neurons (that come form periphery) axons enter where
enter the dorsal horn
true or false: primary sensory neurons synapse in the dorsal horn
false, immediately enter the dorsal columnb
in DCML, what happens to the primary seocnsry neurone immediately after enter the dorsal horn
immediately enters the dorsal poster horn
in DCLM, what happens the the primary sensory neuron signal immediately after entering the dorsal COLUMB
ascends spinal cord in fascicles cuneatus or fasculis gracilis
in the DCML, if the signal comes from spinal level T6 and above, where does it ascend the spinal cord
ascends in the fasciculus cuneatus
in the DCML, if the signal comes from below T6, where does it ascend the spinal cord
ascends in the fasciculus gracilis
in the DCLM, what is the division between the fasciculus cuneatus and gracilis called
dorsal (posterior) intermediate septum
in DCML, fasciculis cuneatus is associated with what spinal levels
t6 and above
in DCML< fasciculis gracilis is associated with what spinal levels
below t6
explain the somatotropin organization of dorsal (posterior) column
primary sensory neurons from lumbosacral region = more medial
from cervical region= lateral
in the dorsal (posterior) column, primary sensory neurons from the lumbosacral region are more lateral or medial
medial
in the dorsal (posterior) column, primary sensory neurons from the cervical region are more lateral or medial
lateral
explain why primary sensory neurons from lumbosacral are more lateral in the dorsal columb
axons are pushed more medially as more dorsal rootlets enter spinal cord at each level (from caudal to rostral)
in DCLM, where do primary neurons synapse with secondary sensory neurons
in the nucleus cuneatus or nucleus gracilis, depending on origin of the sensory info
in DCML, if the signal is from t6 and above, where do primary neurons synapse with secondary neurons
nucleus cuneatus
in DCLM< if the signal is from below t6, where do primary neurons synapse with secondary neurons
nucleus gracilis
in DCML, level of sensory decussation is where
near the centre of the medulla oblongata in the longitudinal direction (rostral to the decussation of the pyramids, (motor pathway) but caudal to the level of the open medulla
in DCML, decussating secondary sensory neuron axons form what
the internal arcuate fibres
where is the ML tract located in relation to the rostral medulla
medial lem dorsal to the pyramids, near the midline
in DCML, secondary sensory neurons synapse with tertiary sensory neurons where (be specific)
in one of the ventral posterior nuclei of the thalamus (either lateral or medial)
in DCML, for secondary sensory neurons coming from the body (including axial and appendicular tissues), where do they synapse
in the ventral posterior lateral nuclei of the thalamus
in DCML, for secondary sensory neurons coming from the face (via trigeminal), where do they synapse
in the ventral posterior medial nuclei of the thalamus
true or false,in DCML, for secondary sensory neurons coming from the body (including axial and appendicular tissues), they synapse inin the ventral posterior medial nuclei of the thalamus
false, in the ventral posterior lateral nuclei of the thalamus
true or false: the thalamus is the relay centre
true
what is the thalamus (in general)
large, paired nuclei in the diencephalon
what part of the brain is the thalamus located
diencephalon
true or false: all conscious and non conscious must be relayed thru the thalamus en route to the primary cortices except olfaction
false, only ALL CONCIOUS (except olfactory)
=no nonconcious
all concious sensation is relayed thru the thalamus en route to the primary cortices except what sensation
olfaction
true or false, only sensory Information goes thru thalamsu
false, also accessory motor pathways (ex: control and coordination)
axons of the tertiary sensory neurons contribute to what
the internal capsule (white matter tract) =specifically the posterior limb and genu
is the internal capsule white or grey matter
white matter trasht
what is the location of the internal capsule
it is situated lateral to the thalamus and caudate nucleus, and medial to the lentiform nucleus.
which two structures what the lentiform nucleus
globus pallidus (medial) and putamen (lateral)
in DCLM, in the internal capsule, somatosensory info from the face contributes to what part of the internal capsule
contributes to the genu of the internal capsule (bend)
in the internal capsule, somatosensory info from the cervical to lumbar contributes to what part of the internal capsule
it is arranged from rostral (cerical) to caudal (lumbar)
in the DCML, do axons of tertiary sensory Hurons contribute more to the anterior or posterior limb of the internal capsule
posterior limb (and genu)
where is the posterior limb of the internal capsule locaeted
between the thalamus and lentiform nucleus (GP and P)
what is the lentiform nucleus
nuclei (collection of cell bodies) involved in motor control
is the lentiform nucleus involved in sensory or motor control
motor control
what is a nuclei
collection of cell bodies
axons of the tertiary sensory neurons join the BLANK before terminating in the primary somatosensory cortex
corona radiata
what is the corona radiate
sensory fibres somethimes reference to thalamocortical fibres)
where do axons of the tertiary sensory neurons terminate
in the primary somatosensory cortex (according to somatotropin arrangement)
going medial to lateral, what is the somatotropin organization of the lower limb, upper limb, trunk and face
medial to lateral =
lower limb (in the longutinatl median fissure), trunk, upper limb, face
be able to draw out the pathways for the DCML
what do lesions of the DCML pathway lead to deficits in
fine (discriminative) touch , vibration, and conscious proprioception
what is tabes dorsals (aka progressive locomotor ataxia)
a progressive degenerative disorder of the dorsal columns and dorsaal roots of the spinal cord
in tabes dorsalis, what is demyelination caused by
untreated neurosyphilis infection
which of these sensations are not carried by the DCML pathway
a) nociception
b) conscious proprioception
c) vibration
d) non conscious proprioception
a: nociception
d) non conscious proprioception
true or false: only golgi tendon organs and msucel spindles allow us to know our limb position in spavce
false
joint kinesthetic receptors in capsule of synovial joints are also believed to play a role in awreness of limb position and movement
what are msucles spindles made of
intrafusal muscle fibers
what do msucle spindles respond to
changes in msucle length
where are golgi tensons located
near myotendinous junctions
what is the function of golgi tendon organs
slow adapting response to tenssion (stretching) in tenson
what are the neurons that cause main movement of limb in proprioeception
alphamotor neuron
what neurons innervate the extrafusal fibers
alpha motor neurons
what neurons innervate the intrafusal msucle fibers
gamma motor neurons
what is function of gamma motor neurons
=innervate intrafusal fibers of msucle spindles to keep stretch receptors taut (ex; during concentric contraction)
=allow then the short in relation to extrafusal fibers (always taut)
explain the organization of the ML tract in the rostral (open) medulla
lumbar= ventral
cervical= dorsal
what is the location of the ML tract in the pons
licated in the dorsal aspect of the basilar (ventral pons)
what is the somato organization of the ML in the poons
lumboscarcal = lateral
cervical =medial
what is the location of the ML tract in the midbrain
ML is located medial to substantia nigra and dorsolateral to red nucleus
what is the somato organization of the ML tract in the midbrain oppsoite to
rostral medulla
what is the somato organization of the midbrain for the ML travt
cervical = ventral
lumbar=dorsal
after decussating, the tracts formed by 2 sensory neuron axons in the DCML are collectively called what
medial leminscus, until it converges on the nucleus of thalamus
what is the division between fasciculus gracilis and cuneatus called
dorsal (posterior) intermediate septum
