Lecture 7- Somatosensory Flashcards
SOMATOSENSORY OVERVIEW
SOMATOSENSORY OVERVIEW
Somatosensation is divided into _____ sensation and __________ sensation.
- skin sensation
- musculoskeletal sensation
What are the 3 components of skin sensation?
- touch
- pain
- temperature
What are the 2 components of musculoskeletal sensation?
- proprioception (muscle and tendon stretch, joint position, vibration)
- pain
Describe the somatosensory pathway.
- sensory stimulus
- receptor
- threshold stimulation
- AP on peripheral (distal) axon/process of pseudounipolar sensory neuron in perpheral nerve
- pseudounipolar neuron soma located in dorsal root ganglia
- central (proximal) axon/process in dorsal root
- brainstem/spinal cord
1. withdraw reflex or
2. ascending tract- lower brain (REFLEX)
- cerebral cortex (VOLUNTARY RESPONSE)
- The sensory pathway involves a _____ of neurons.
- Signal movement through the pathway is dependent on what 2 things?
- Signals often ____ to the other side.
- series
- diameter of axons, degree of axon myelination
- cross
PERIPHERAL SOMATOSENSORY SYSTEM
PERIPHERAL SOMATOSENSORY SYSTEM
What are the 6 types of receptors located in the Peripheral Somatosensory System and their function?
- ) Mechanoreceptors (stretch)
- respond to stimuli such as touch, pressure, stretch, vibration - ) Chemoreceptors
- detects changes in normal environment - ) Thermoreceptors
- detect temperature - ) Nociceptors
- detect pain - ) Tonic Receptors
- SLOW adapting to stimulus - ) Phasic Receptors
- RAPID adapting to stimulus
What is the difference between tonic and phasic receptors?
- Tonic= slow adapting
- Phasic= rapid adapting
What are the 3 types of sensory neurons and what signals do they carry?
- viscerosensory (general visceral afferent; GVA)- carry unconscious signals
- somatosensory (general visceral afferent; GSA)- carry conscious signals
- special sensory (special sensory afferent; SSA)
Sensory neurons are ___________ in structure.
pseudo-unipolar
What is the structure of a pseudo-unipolar neuron?
- peripheral (distal) axon
- soma
- central (proximal) axon
Where are the soma of sensory neurons located?
- dorsal root ganglia (DRG)
- cranial nerve sensory ganglia
If a sensory neuron is classified as a Aα it has a ______ conduction velocity.
If a sensory neuron is classified as a Ia it has a ________ fiber diameter.
- fast
- large
- Most sensory neurons will be type __-__ nerve fibers.
- Pain is type __ neuron.
- II-III
- IV
Skin sensation is ______sensory
somato
- What is the receptive field?
- Are they the same as dermatomes?
- Area of skin innervated by a single sensory neuron
- No
______ receptor fields and ________ density of sensory neurons give some body regions (finger tip) greater 2 point discrimination.
- smaller
- greater
What are the fine touch receptors from superficial skin to deep?
- Merkel’s (touch)
- Meissner’s (touch, vibration)
- Pacinian (touch, vibration)
- Hair follicle receptor
- Ruffini (skin stretch)
_______ receptor is the most sensitive to things touching the skin while _______ is the least.
- Merkel’s
- Ruffini
Fine touch receptors allow good _________ of stimuli.
resolution
All fine touch receptors transmit signals on ___ axons; so what can you conclude about the speed of transmission?
- Aβ
- generally quick conduction velocity in regards to sensory neurons
- Course touch are ____ nerve endings.
- Course touch involves _______ localization. What is this?
- free
- crude, crude touch allows the subject to sense something has touched them without them being able to localize it
Course touch receptors transmit signals on ___ axons, so are they faster or slower than fine touch receptors?
- Aδ
- slower
Pain (tissue damage) are carried by ________ which have ____ nerve endings that detect extremes of mechanical, chemical, and temperature stimuli.
- nociceptors
- free
Pain receptors transmit signals on ___ and ___ neurons, are they fast?
- Aδ and C
- No, they are the slowest signals
Proprioception is primarily determined by __________ receptors from stretch (_______) and pressure changes associated with changing the position of body segments.
- musculoskeletal
- Ruffini
What is a dermatome?
area of skin with sensory innervation by a particular dorsal root
Muscle spindle fibers are __________ located inside muscle _______ to muscle fibers= intrafusal fibers.
- proprioreceptors
- parallel
What are the 2 fibers that make up muscle spindles?
- nuclear chain muscle fiber
- nuclear bag muscle fiber
The annulospiral receptor/group Ia sensory neurons detect ____________=rate of change. They are associated with both the nuclear chain and bag intrafusal fibers.
-dynamic length/stretch
The flower spray/ group II sensory neurons detect ____________. They are associated with ______ fibers more that ______.
- static length/stretch
- chain, bag
What causes motor stimulation of intrafusal fibers
gamma motor neuron
Brain takes signals from muscle spindles in ALL muscles crossing a given joint to determine whether the body part at that joint is moving and where it is in space=___________.
proprioception
When whole muscle (_________ fibers) contracts via ________ motor neurons the muscle spindle fibers (__________ fibers) may also contract via ________ motor neurons to keep the spindle stretched/tense so it will remain _________ even when the whole muscle is shortening during contraction.
- extrafusal fibers
- alpha
- intrafusal
- gamma
- sensitive
Muscle spindles are capable of ________ and ____ signaling via Type Ia (annulospiral) and II (flower spray) afferent sensory neurons.
phasic and tonic
Golgi tendon organs are __________ organs located inside ________. These organs are very sensitive to ______ of the tendon.
- proprioceptive
- tendon
- tension (stretch)
Golgi tendon organs are Type ___ afferent neurons. They are part of a reflex that ________ muscle contraction to reduce stretch on muscle tendon.
- Ib
- inhibit
Joint receptors respond to ________ deformation of joint capsule and ligaments= mechanoreceptors responding to stretch
-mechanical
What are the 4 joint receptors and their function?
- Paciniform- movement
- Ruffini- indicate end range; and passive movement
- Free nerve endings- pain from inflammation
- Ligament receptors- tension (stretch) receptors (golgi tendon organs)
What is proprioception and what are the 3 things it is a result of?
Awareness of joint position and movement
- muscle spindles
- joint receptors
- cutaneous mechanoreceptors
PATHWAYS OVERVIEW
PATHWAYS OVERVIEW
What is a tract?
bundle of axons in CNS with a common origin and destination
Pathway includes the _________ neuron that delivers information to the CNS tract and carries information from the tract to its final destination.
peripheral
Only neurons with long axons (___________ neurons) are included in pathway descriptions; pathways also contain __________ that interconnect pathways.
- projection
- interneurons