include both free and encapsulated endings receiving skin tactile sensidbility
mechanoreceptor expanded tip endings
mechanoreceptors spray endings
Name the two specific mechanoreceptors which feature encapsulated endings:
meissner's corpuscles kraus corpuscles
sound receptors of cochlea
mechanoreceptors with encapsulated endings, responsible for sensitivity to pressure and vibrations
mechanorepectors arterial pressure
cold and warm receptors
free nerve endings responding to pain
include rods and cones of the eye for vision
taste, smell, arterial oxygen, osmolarity, blood CO2, Blood glucose, amino acids, fatty acids
each type of receptor is highly sensitive to one type of stimulus and is almost nonresponsive to toher types
refers to each of the principal types of sensation
adaption of receptors
-all sensory receptors adapt either partially or completly to any constant stiumuls after a period of time -some receptors adapt to a far greater extent than others
the specificity of nerve fibers for transmitting only on modality of sensation
Labeled Line Principle
characteristics of tonic receptors
-slow adapting -detect continous stimulus strength -transmit impulses as long as stimulus is present
Types of tonic receptors
muscle spindles golgi tendon organs macula and vestibular receptors baroreceptors chemoreceptors
characteristics of phasic receptors
rapidly adapting do no transmit a continuous signal stiumlated only when stimulus strength changes transmit informaiton regarding rate of change
Type A fibers
further subdivided into, alpha, gamma, beta, delta lg and medium sized myelinated fibers of spinal nerves
small, unmyelinated fibers conduct signals at low velocity make up more than half of all sensory fibers in most peripheral nerves and all post ganglionic autonomic fibers
fibers from annulospiral endings of muscle spindles
Group Ia (Type Aalpha fibers)
Fibers from golgi tendon organs
Group Ib (Type Aalpha fibers)
from cutaneous tactile receptors and flower spray
group II ( type Abeta, gamma fibers)
carry temp, crude touch, and pricking pain
group III (type A delta fibers)
carry pain, itch temperature, and crude tough
group IV (type C fibers)
-increase signal strength by increasing frquencey of nerve impulses in each fiber
Explain/describe the concept of Spatial summation
increasing signal strenth in transmittted by using progressively greater number of fibers -entire cluster of nerve endings from one pain fiber covers an area of skin referred to as the receptor field for that fiber -number of endings is lg in center of field buy is reduced in periphery -nerve endings from one pain fiber overlap those of other pain fibers
stimulatory field of nueronal pool
-stimuatled by each incoming nerve fiber -terminals for each input fiber lie on the nearest neuron in its field - fewer terminals for each input fiber lie on neurons further away
give examples of a neuronal pool
cerebral cortex basal nuclei thalmaic nuclei cerebellum mesencephalon pons medulla gray matter of spinal cord
includes all the output fibers stimulated by the incoming fiber
faciliated inhibition zone
-neurons further from the discharge zone that are facilitated but not excited -may be inhibitory or excitatory depending on the input fiber
diverging neuronal pathways
may result in amplification of initial signal may allow transmission of original signal to separte areas
converging neuronal pathways
multiple input fibers converge onto a single output neuron input fibers may be from a single source or from multiple separate sources
Reverberatory circuits or oscillatory circuits
caused by postivie feedbback within neuronal circuit circuit once stimulated may discharge repetitively for a long time
What are somatic senses?
collect sensory information from all over the body
What are three types of somatic senses?
mechanoreceptive thermoreceptive pain
What are some examples of special senses?
vision, hearing, smell, taste, equilibrium
What are exteroreceptive sensations?
From the surface of the body
What is proprioceptive sensations?
refer to physical state of the body -position sensations -muscle and tendon sensations -pressure sensations -equilibrium
What are deep sensations
deep pressure, pain, and vibrations
What are mechanoreceptive somatic senses?
include both tactile and position senses that are stimulated by mechanical displacement of some tissue of the body
What are physiological types of somatic senses?
mechanoreceptive somatic senses thermoreceptive senses pain sense
What are three neuron ascending pathways?
primary sensory neurons secondary neurons tertiary neurons
What are primary sensory neurons?
from external receptors travel through dorsal roots of spinal cord
What are secondary neurons?
make up tracts in spinal cord and brainstem
What are tertiary neurons?
from thalamus to primary sensory cortex travel through internal capsule
What are two examples of ascending pathways for conscious perception?
spinothalamic system medial lemniscal system
What are ascending pathways that are unconscious perception?
spinocerebellar spino olivary spinotectal spinoreticular
What makes up the spinothalmaic system?
lateral spinothalamic tract anterior spinothalamic tract
What does the lateral spinothalamic tract
-carries pain and temperature -primary fibers ascend or descend 1-2 spinal cord segments before synapsing with secondary fibers -secondary axons decussate through anterior gray and white commissures -secondary axons make up the lateral spinothalamic tract traveling in the lateral column of the spinal cord
Where are the secondary fibers in the lateral spinothalamic tract joined?
in brainstem by fibers of the trigeminothalamic tract -pain and temperature from face an teeth
Where do secondary fiber collaterals project for the lateral spinothalamic tract?
stimulate wakefulness and consciousness
Where do secondary fibers project of the lateral spinothalamic tract?
to ventral posterolateral (VPL) nucleus of thalamus
Where do secondary fibers synapse in the lateral spinothalamic tract?
with tertiary fibers in VPL
Where does tertiary fibers (corticopetal fibers) of the lateral spinothalamic tract synapse?
in postcentral gyrus: somatic sensory areas 3,1,2
What does the tertiary fibers of the lateral spinothalamic tract form?
What caries light touch(crude touch), pressure, tickle, itch?
anterior spinothalamic tract
What is the medial lemniscus system also called?
posterior column system
What does the medial lemniscus system carry sensation for?
two point sensation (Fine touch), pressure, and vibration
Where does primary fibers ascend for medial lemniscus system?
entire length of spinal cord and synapse with secondary neurons in medulla
What are the secondary neurons in medulla?
fasciculus gracilis fasciculus cuneatus
Where do fibers of fasciculus gracilis synapse?
in nucleus gracilis -convey sensations from below midthoracic level
Where doe fibers of fasciculus cuneatus synapse?
in nucleus cuneatus -convey sensations from above midthoracic level -also conveys proprioceptive sensation from arms to cerebellum
What do medial lemniscus system secondary fibers do?
- decussate - ascend to synapse in VPL of thalamus, and then the tertiary will ascend through the internal capsule to the primary sensory cortex.
What do medial lemniscus system tertiary fibers do?
ascend through internal capsule to primary sensory cortex
What do the anterior spinothalamic tract primary neurons?
may ascend 8-10 spinal cord segments before synapsing with secondary neurons
What do the anterior spinothalamic tract secondary fibers do?
-decussate in anterior gray or white commissures - ascend to synapse with tertiary fibers in VPL nucleus of thalamus
What do the anterior spinothalamic tract tertiary fibers do?
ascend through internal capsule to primary sensory cortex.
All of the output neurons that are stimulated by an incoming fiber comprise the __________. A) Neuronal Pool B) Discharge Zone C) Zone of Facilitation D) Stimulatory field
Ans: B) Discharge Zone
Which tract is known for ascending or descending 1 to 2 vertebral segments before synapsing on a secondary neuron in the CNS? a) Anterior Spinothalamic Tract b)Medial Lemniscus System c) the Fasciculus Cuneatus d)the Fasciculus gracilis e) the Lateral Spinothalamic Tract
e) the Lateral Spinothalamic Tract
Which Tract system is sensitive to vibration, pressure and 2 point sensation? a) Anterior Spinothalamic Tract b)Medial Lemniscus System c) the Fasciculus Cuneatus d)the Fasciculus gracilis e) the Lateral Spinothalamic Tract
b)Medial Lemniscus System
Which specific tract conveys proprioceptive sensation from the arms to the cerebellum? a) Anterior Spinothalamic Tract b)Medial Lemniscus System c) the Fasciculus Cuneatus d)the Fasciculus gracilis e) the Lateral Spinothalamic Tract
c) the Fasciculus Cuneatus
Which tract specifically synapses in the nucleus gracilis and conveys sensations from below the mid thoracic level? a) Anterior Spinothalamic Tract b)Medial Lemniscus System c) the Fasciculus Cuneatus d)the Fasciculus gracilis e) the Lateral Spinothalamic Tract
d)the Fasciculus gracilis
T/F: The Temporal Summation is when an increased signal strength is increased by the number of neurons synapsing and thereby increasing the frequency of nerve impulses.
FALSE. The Temporal Summation is when there is an increase in signal strength by increasing the frequency of nerve impulses, but it will be from THE SAME presynaptic fibers... not additional ones
Define Discharge Zone:
includes all the output fires stimulated by incoming fibers
Ruffini Corpuscles can be remembered because "Ruffles have ridges." What type of endings do these Free Mechanoreceptors have?
Free expanded spray endings.