Sensory and Proprioception: Module 3.1-3.2 Flashcards
What type of information is Sensory Input?
Afferent
What type of information is motor output?
Efferent
Are autonomic neurons affernet or efferent?
Both
What are the different sensory systems and their receptor classes and cells?
What are sensory modalities?
Include the familiar ones of seeing, hearing, touching, smelling, and tasting as well as our senses of pain, balance, body positionk and movement.
Also, intricate sensory systems of which we are not conscious monitor the internal milieu and report on the body’s chemical and metabolic state.
Sensory receptors convert ____ into ____.
Sensory receptors convert environmental energy into neural signals.
What are the 3 major functions of the somatosensory system?
- Proprioception (Sense of Onself): Receptors in skeletal muscle, joint capsules, and the skin generated a conscious awareness of the posture and movements.
- Exteroception (Direct Interaction with External World): Sensory Modalities = Touch, Pain
- Interoception (Sense of the function of the major organ systems/internal state): Primarily Chemoreceptors (Blood Gases and pH)
What are the primary sensory afferent cells of the somatosensory system?
DRG (Dorsal Root Ganglia) Neurons
The cell bodies of neurons tha tbring sensory information from the skin muscles, and joines lie in the DRG.
Where is the DRG located?
Found adjacent to the spinal cord.
The neurons are bifurcated into peripheral and central branches. the central branch enters the dorsal portion of the spinal cord.
What are the 5 functional zones of the DRG?
- Distal Terminals: contain specialized receptor-channels that convert specific types of stimulus energy (mechanical, thermal,, or chemical) into a depolarizing receptor potential (graded potential).
- Spike Generation Site: Contains Nav and Kv channels, located near the initial segment of the axon. conversion of the receptor potentials in APs.
- Peripheral Nerve FIber (Branch): Transmits action potentials from the spike initiation site to the DRG cell body.
- Cell Body: Contained within DRGs
- Spinal or Cranial Nerve: Connects the DRG or trigeminal neuron to the ipsilateral spinal cord of brain stem.
DRG neurons are _____.
DRG neurons are pseudo-unipolar.
What is the function of the Thalamus?
The Thalamus links sensory receptors and the cerebral cortex for all modalities exept olfaction.
Also Acts as a gatekeeper for information to the cerebral cortex, prevening or enhancing the passage of speciic information depending on the behavioral state of the animal.
What nerves do Vision and Taste sensory input use?
Cranial Nerves
What nerves do Somatosensory input use?
Spinal Nerves
What are the 2 pathways in which somatosensory information from the limbs and trunk ascend from?
- Dorsal Column-medial lemniscal system.
- Anterolateral System
Explain the Dorsal Column Medial Lemniscal System.
Explain the Anterolateral System.
How is the somatosensory cortex organized?
Somatotopically Organized
Amount of surface area of cortex devoted to each body part proportional to density of innvervation of sensory fibers (fineness of discrimination in the body).
How are sensory nerves classified?
Classified into functional groups based on properties related to axon diameter and myelination, conduction, velocity.
What are the different classification of sensory fibers?
What do the different types of fibers innervate and how are they activated?
Aa: in muscle, nerves innervate muscle spindle receptors and Golgi tendon organs (proprioception).
AB: innvervate secondary spindle ending and receptors in joint capsules (proprioception).
AD: the smallest myelinated muscle afferents.
C Fiber: signal trauma or injuries in muscle and joints that are sensed as painful
Activation of what fibers result in pain?
Ad and C fibers.
Neuronal communication depends on PSP with ligand gated channels
What does sensory transduction depend on?
Receptor Potentials mediate by the effect of an environmental stimulus acting on a receptor molecule.
What type of channels are many types of sensory transduction mediated by?
TRP Channels (Transient Receptor Potential)
What are TRP Channels and its characteristics?
Thermal Receptors
Plays central roles in sensory transduction pathways (pain, itch, heat, taste, and touch).
Genetic subfamily: vanilloid (V), melastatin (M), and ankyrin (A).
- Are cation non-selective channels, composed of 4 subunits (tetramers), each containing 6 transmembrane domains. The pore region is between S5 and S6. May be permeable to Ca.
- Some (TRPV1 and TRPM8) have a voltage-sensor.
- TRPs are tetramers (4 subunits)
- Different sensitivity to heat or cold.
What can TRP channels can be activated by?
What is proprioception and how does it work?
Sense of Onself
Receptors in skeletal muscle, and joint capsules, and the skin enable us to have conscious awareness of the posture and movements of out own body, particularly the four lumbs and the head.
Measures activity and joint positions.
Can people move body without sensory propriceptor feedback?
Yes, however movements are clumsy if there is no visual aid.
Where do group 1 and 2 sensory muscle fibers innervate and what are they sensitive to?
What are muscle spindles?
Small encapsulated sensory receptors.
They signal changes in the length of the muscle in which they reside.
They sense changes in length associated to changes in joint angles that the muscle cross.
Muscle spindles are used by the central nervous system to sense relative positions of the body.
The Muscle Spindles run ____ to the extrafusal muscle fibers.
The Muscle Spindles run parallel to the extrafusal muscle fibers.
What are the 3 components of Muscle Spindle?
- A group of specialized intrafusal muscle fibers with noncontractile central reigions.
- Sensory fibers that terminate on the cntral regions of the intrafusal fibers
- Motor axons that terminate on the contractile polar regions of the intrafusal fibers.
What type of neuron adjusts the sensitivity of muscle spindles?
Gamma Motor neurons
The CNS can independently adjust the ____ and ____ sensitivity of sensory endings.
The CNS can independently adjust the dynamic and static sensitivity of sensory endings.
Explain the loading and unloading of muscle spindle.
Stretching a muscle, stretches the intrafusal fibers, which also stretches the sensory
endings, which increase their firing.
When a muscle shortens, the spindle is unloaded and the activity decreases.
Activation of Gamma motor neurons during active muscle contraction ____ muscle spindle ____ to muscle length.
Activation of Gamma motor neurons during active muscle contraction maintains muscle spindle sensitivity to muscle length.
