Anatomy 4 Ascending Tracts Flashcards
What are the 3 skin sensations?
- Touch (superficial pressure or vibration)
- Pain
- Temperature
What are the 2 musculoskeletal sensations?
- Proprioception
2. Pain
What are the 4 types of musculoskeletal proprioception sensations?
- Muscle stretch (tension)
- Tendon stretch (tensions)
- Deep vibration
- Joint position (static and movement (kinesthetic))
Describe the somato-sensory pathway starting with sensory stimulus
- Sensory stimulus
- Receptor
- Threshold stimulation
- AP on peripheral (distal) axon/process of pseudounipolar sensory neuron in peripheral nerve
- Pseudounipolar neuron soma located in dorsal root ganglia
- central (proximal) axon/process in dorsal root
- brainstem/spinal cord (white or dorsal horn gray matter)
- Withdrawal reflex
or - Ascending tract to
a. lower brain (unconscious sensory input) reflex
b. cerebral cortex (conscious perception) voluntary response
Signal movement through the pathway is dependent on what 2 things:
- Diameter of axon
2. Degree of axon myelination
Mechanoreceptors are sensors/receptors of peripheral system that sense what?
- Touch
- Pressure
- Stretch
- Vibration
Chemoreceptors are sensors/receptors of peripheral system that sense what?
Viscerosensory
Thermoreceptors are sensors/receptors of peripheral system that sense what?
Temperature
Nocereceptors are sensors/receptors of peripheral system that sense what?
Pain
What is a tonic receptor in the peripheral system?
Fast/Slow adapting?
Tonic receptor - responds as long as a stimulus is present
-Slow adapting
What is a Phasic receptor in the peripheral system?
Fast/Slow adapting?
Phasic receptor - detect a change from stimulus then adapt to the changed state and stop responding before the stimulus ends
-Rapid adapting
What are these and what do they carry and where in brain?
GVA
GSA
SSA
GVA - general visceral afferent (viscerosensory)
- carry unconscious signals to diencephalon
GSA - General sensory afferent (somatosensory)
- carry conscious signals to post central gyrus
SSA - Special sensory
Where are the soma of sensory neurons located?
Dorsal root ganglia and cranial nerve sensory ganglia
Sensory neuron classification:
Ia or Aa
large diameter, myelinated (fastest)
- Primary muscle spindle afferents
- Motor efferents to extrafusal muscle
Sensory neuron classification:
Ib or Aa
Large diam, myelinated
- Golgi tendon organ afferents
- Contractile tension (force)
Sensory neuron classification:
II or Ab
Medium diam, myelinated
- Mechanoreceptors (discriminative touch, pressure, joint)
- Secondary muscle spindle afferents (static muscle length)
Sensory neuron classification:
III or Ad
Small diam, myelinated
- Mechanoreceptors (touch)
- Nocioception (discriminative pain)
Sensory neuron classification:
IV or C
Smallest diam, unmyelinated (slowest)
- Nocioception (inflammatory/visceral pain, thermal sense)
- Autonomic postganglionic axons
Skin sensation is what type of sensory?
Somatosensory
What is a receptive field?
Where will you have small receptive fields and why?
- Area of skin innervated by a single sensory neuron
- Small receptor fields and greater density of sensory neurons give some body regions (finger tip) greater 2 point discrimination
Whats the difference between receptive field and dermatome?
Receptive field - 1 single sensory nerve
Dermatome - 1 single spinal nerve
Innervation of skin:
Merkel’s -
fine touch, closest to surface so most sensitive
Innervation of skin:
Meissner’s -
fine touch and vibration
Innervation of skin:
Pacinian -
Subcutaneous
fine touch and vibration
Innervation of skin:
Hair follicle receptor -
Hair root plexus
Innervation of skin:
Ruffini -
skin stretch, furthest from surface
T/F:
Fine touch receptors have bad resolution of stimuli
False
Good resolution
All fine touch receptors transmit signals on what fiber size?
Ab axons (Medium diam, myelinated)
Innervation of skin:
Free nerve endings -
Course touch, pressure, tickle and itch
Innervation of skin:
Crude localization -
resolution
All course touch receptors transmit signals on what fiber size?
Ad
Are fine touch or course touch fibers faster?
Fine touch (travel on Ab axons while course touch travels on Ad axons)
Innervation of skin:
Nociceptors -
- Free nerve endings detect extremes of mechanical, chemical, and temp stimuli (tissue damage = pain)
What type of neurons (size) carries pain signals?
Ad and C neurons (slow)
Innervation of skin:
Temperature -
Free nerve endings
What type of neuron (size) carries temperature singals?
Ad neurons carry cooling sensation
C neurons carry heat sensation
Proprioception is primarily determined by what type of receptors and what type of changes?
- musculoskeletal - Ruffini (stretch)
and - pressure changes associated with changing the position of body segments
What is an intrafusal muscle fiber?
a muscle spindle (proprioceptor) located inside muscle parallel to muscle fibers
What two types of muscle fibers do an intrafusal fibers consist of?
Nuclear chain
Nuclear bag
Afferent Annulospiral receptor:
What axon group?
What does is detect?
Bag/chain or both?
annulospiral receptor
- Group Ia sensory neuron
- Detects dynamic length/stretch (rate of change)
- Associated with both bag and chain intrafusal fibers
Afferent Flower spray receptor:
What axon group?
What does is detect?
Bag/chain or both?
Flower spray receptor
- Group II sensory neuron
- Detects static length/stretch
- Associated more with chain than bag
What is the efferent motor stimulator of intrafusal fibers?
What does it do?
Gamma motor neuron
-Keep bag/chain receptors loaded
What occurs when muscle spindle if a muscle is stretched at a joint?
Muscle spindle is stretched -> sends afferent signals to brain regarding change in length -> brain takes in signal to determine whether body part at that joint is moving and where it is in space (proprioception)
What type of motor neuron contracts whole muscle?
-Alpha motor neurons stretch whole muscle (extrafusal fibers)
What happens to muscle spindle fibers when whole muscle contracts?
-Muscle spindle fibers (intrafusal) will also contract via gamma motor neurons to keep spindle stretched/tense so it will remain sensitive when when whole muscle is shortening during contraction
T/F:
Muscle spindles only capable of Phasic signaling via type Ia (annulospiral) and II (flower spray) afferent sensory neurons
False
Capable of phasic and tonic signaling
What are golgi tendon organs?
What will it inhibit in muscle?
- Acts as proprioception
- Series arrangement of nerve endings in the dense regular CT of the tendon (sensitive to changes in tension/stretch of tendon)
- Part of reflex that inhibits muscle contraction to reduce stretch on muscle/tendon
What type of sensory neuron (size) is golgi tendon organs?
Type Ib afferent
What are joint receptors?
-Respond to mechanical deformation of joint capsule and ligaments
What are the 4 types of joint receptors and what do they do?
- Paciniform - movement
- Ruffini - indicate end range and passive movement
- Free nerve endings - pain from inflammation
- Ligament receptors - tension (stretch) receptors
What is proprioception and receptors?
-Awareness of joint position Results from: 1. Muscle spindles 2. Joint receptors 3. Cutaneous mechanoreceptors
What is the difference between a tract and a pathway?
Tract - bundle of axons in CNS with common origin and destination
Pathway - includes peripheral neuron that delivers information to the CNS tract and carries information from tract to final destination
T/F:
Only short axons are included in pathway descriptions
False: only neurons with long axons (projection neurons) are included in pathway descriptions
-Pathways also contain interneurons that interconnect pathways
What is a conscious pathway?
Ends in cerebral cortex
What is a divergent pathway?
branch to end at many CNS locations for both conscious and unconscious perception
What is an unconscious pathway?
End at brain locations below the cerebral cortex (brainstem, cerebellum, diencephalon, limbic)
What is a loop pathway?
- Neural connection between a receptor and effector
- Includes sensory pathway, CNS control center, and motor pathway
What is the difference between high fidelity and low fidelity?
High - pinpoint location of origin
Low - signals have a general origin
What is discriminative information?
Allows for precise identification of stimuli
What is required for high fidelity signals?
Somatotopic organization
What does slow pain result from?
Is slow pain localizable?
What fibers carry slow pain?
Where is slow pain’s destination?
- Results from tissue damage
- NOT localizable
- Carried by C fibers
- Destination:
1. Insula
2. Associative sensory cortex of parietal lobe
Is divergent pathway conscious/unconscious or both?
What is the medial pain system for divergent pathways?
Divergent pathways - both conscious and unconscious
Medial pain system - for pain modulation, motivational, withdrawal, arousal, and autonomic responses to pain
Nocireceptors become more/less sensitive with repetitive stimulus of the medial pain system of divergent pathways?
More sensitive
Describe divergent pathways of medial pain system:
Somatotopic?
Localizable?
# of Neurons?
Not somatotopic or localizable
Variable number of neurons
What NT does divergent pathways of medial pain system use?
Substance P at synapse in dorsal horn of Lamina I, II, V
Divergent neurons:
Spinomesencephalic -
What does it carry and to where?
What part of spinal cord carries descending?
Reflex movement tract -> superior colliculus
- Turn head to position eye on pain source
- Activate descending neurons that modulate pain sensation
- Periaquiductal gray found in mesencephalic: descending pain modulation
Divergent neurons:
Spinoreticular -
Intensity tract -> reticular formation such as raphe nucleus, locus ceruleus, to modulate pain sensation to thalamus
Divergent neurons:
Spinolimbic -
Conscious emotional response tract -> anterior cingulate cortex (links pain sensation to emotional response, negative feeling toward pain)
-> posterior insula: pain sensation
Unconscious pathways general:
Carry what from where to where to do what?
Carry proprioceptive and feedback info about activity in motor tracts (interneuron links) to cerebellum to adjust (refine) conscious movement
Unconscious pathways: Posterior spinocerebellar pathway - Somatotopic? Localizable? # of Neurons? Crossed?
2 Neuron pathway carrying high fidelity somatotopic information from the lower body to cerebellar cortex on ipsilateral side (uncrossed)
Unconscious pathways: Cuneocerebellar pathway - Somatotopic? Localizable? # of Neurons? Crossed?
2 Neuron pathway carrying high fidelity somatotopic info from upper body to cerebellar cortex in ipsilateral side (uncrossed)
Unconscious pathways: Anterior Spinocerebellar tract Somatotopic? Localizable? # of Neurons? Crossed?
1 Neuron pathway to provide cerebellum feedback from spinal cord ventral horn interneurons to monitor activity of lower body
- Crossed
- Low fidelity
Unconscious pathways: Rostrospinocerebellar tract Somatotopic? Localizable? # of Neurons? Crossed?
1 neuron pathway to provide cerebellum feedback from spinal cord interneurons and motor activity of upper body
- Ipsilateral
- Low fidelity
