Sensory Receptors And Perception Flashcards
What are receptors that respond to stimulus within the body?
What aRe the four major types?
Interoreceptors
- Proprioceptors
- Visceroreceptors
- Chemoreceptors
- Baroreceptors
What are receptors that respond to stimuli from the outside environment?
What are four examples?
Exteroreceptors
- Cutaneous sense
- Vision
- Olfaction
- Hearing
What does a proprioceptor respond to?
Movement or change in position
What does a visceroreceptor respond to?
Stretching of internal organs or muscular contraction
What does a chemoreceptor respond to?
Changes in the chemical environment
What do baroreceptors respond to?
Changes on pressure
What is the difference between sensation and perception?
What do people in a coma have?
Sensation is the conscious and unconscious awareness of external or internal stimuli
Perception is the conscious awareness AND interpretation of sensation
People in comas have sensation without perception
What is meant by modality?
The specific type of sensation (vibration and thermal pain)
What is transduction?
The conversion of one form of energy to another (light to electrical signal that can be processed in the visual cortex)
What is conduction?
The propagation of a signal to a distant site in the nervous system.
When a receptor potential reaches a threshold at the trigger zone, the receptor can initiate one or more nerve impulses
Why does a sensory exam of light touch yield incomplete information?
Because touch is carried in both small and large fibers
What are the three major components of the somatic sensory system?
- A subsystem for detection of mechanical stimuli such as touch vibration and pressure
- Subsystem for sensation of position
- Subsystem for painful stimuli and temperature
How do peripheral nevers vary in myelin content, diameter, and speed of conduction?
Large diameter fibers are heavily myelinated and conducted impulse quickly (50 m/sec or faster)
What kind of stimuli is transmitted by large caliber fibers?
Mechanical stimuli and somatic motor axons
What signals are transmitted by unmyelinated fibers?
What is the speed of transmission and diameter?
pain and temperature Slow transmission (few m/sec) and small diameter
What is the morphology, sensory modality and conduction for a Ia fiber?
Large myelinated
Proprioception (muscle spindle)
Fast (90m/sec)
What is the morphology, sensory modality and conduction for an Abeta fiber? (type II)
Large myelinated
Vibration pressure touch and stretch
50 m/sec
What is the morphology, sensory modality and conduction speed for an Adelta fiber? (type III)
Small myelinated
Touch, cold, pain
20 m/sec
What is the morphology, sensory modality and conduction speed for a B fiber?
Small myelinated
Autonomics
10 m/sec
What is the morphology, sensory modality and conduction speed for a C fiber? (type IV)
Small unmyelinated
Temperature, pain, itch
1m/sec
What is the difference between type Ia and type Ib fibers?
Ia- sensory afferent for muscle spindle (muscle stretch)
Ib- sensory afferent for Golgi tendon organs (muscle tension)
Both are proprioceptive fibers
A process that affects large, myelinated sensory fibers (Ia) will be associated with what presentation?
The absence of a deep tendon reflex
A monosynaptic deep tendon reflex does what?
A polysynaptic deep tendon reflex does what?
Mono- excites motor agonists
Poly- inhibits motor antagonists
What is tabes dorsalis?
What fibers are selectively damaged by it?
What does this cause?
Syphilis
Large, myelinated fibers
This makes sensory ataxia (due to affected deep tendon reflex) and loss of joint position sense
If large myelinated sensory fibers are damaged, why are people more sensitive to pain?
Because the large fibers suppress painful stimuli.
Which sensory fibers are activated at the lowest threshold ?
The larger the fiber, the lower the threshold for activation so if you stimulate the large fibers with non-painful electrical currents, it can suppress pain.
Where do cell bodies of sensory neurons lie?
What type of neuron is it?
Outside of the spinal cord in the dorsal root ganglion.
These are bipolar neurons with two long axons.
Where does large fiber sensation enter the spinal cord?
What senses are carried by these large fibers?
Where do they travel and synapse?
Medial part of the dorsal root and ascend in the ipsilateral dorsal column.
Proprioception, Vibration, stretch, pressure
The first synapse is with the nucleus gracilis or cuneatus in the medulla.
Where do small fibers enter the spinal cord?
What sensations are these?
Where do they travel and synapse?
They enter in the lateral division of the dorsal root and ascend in the dorsal horn a level or two (lissaurs tract) before synapsing with w a secondary neuron in the substantia gelatinosa.
Pain and temperature
The secondary neuron from the substantia gelatinosa crosses and ascends in the anterolateral part of white matter on the contralateral side of the sensation (Spinothalamic tract)