sensory systems Flashcards
Functions of the sensory system
provide the CNS with representation of the external and internal environment
functions of sensory system- external environment
provides information about the external environment that is crucial for survival (location of food and sources of danger)
functions of sensory system- internal environment
state of internal environment constantly monitored as a part of homeostatic feedback
somatic senses provide information from the body surface like
touch, pressure, vibration, temp, pain, proprioception
what is proprioception
position of the body in space
what is nociception
pain receptors that have varying degrees of sensitivity to mechanical, thermal, and chemical stimuli
what do visceral senses do
provides information from internal organs that does not reach our consciousness, but is essential for maintenanceof homeostasis
example of visceral sense
blood pressure, pH, and temperature
what are special senses
receptors that are concentrated on specific organs located on the head
example of special sense
olfaction, vision, taste, hearing, and equilibrium
our conscious interpretation of the external word as created by the brain from a pattern of nerve impulses delivered from sensory receptors
perception
sensory information can be suppressed, attenuated, or ignored and perception can be affected by our past (T/F)
True
stimulus
a change detectable by the body
stimuli exist in a variety of
energy forms or modalities
process of conversion of nonelectrical forms of environmental energy into electrical events that can be transmitted and processed by the NS
sensory transduction
adequate stimulus
a stimulus that has the lowest threshold of detection and every sensory receptors has this
example of adequate stimulus
photoreceptors in the retina= light
chemoreceptors= pH, O2, smell, and taste
mechnoreceptors= stretch, tissue displacement, and vibration
thermorecpetors= hot/cold
nociceptors
the simplest receptors are
free nerve endings (temp and pain)
pacinian capsule
connective tissue capsule that surrounds nerve endings
stimulation of sensory receptor alters its membrane permeability, leading to a graded
receptor potential (generator potential)
receptor potential is
localized depolarization due to an influx of positive charges
higher stimulus intensity means a higher
frequency of action potentials in a sensory neuron
population coding
it is supplemented by the stems intensity information and it refers to the # of receptors that respond to the same stimulus
adaption prevents
a flood of irrelevant sensory information to the CNS
what receptor does not adapt to maintained stimuli
nociceptors- can make it more sensitive
fast action potential does what to adaption
rapid adaptation
a receptor can only transduce a stimulus that is applied to
a restricted area or receptive field of the receptor
3 primary sensory neurons overlap to form a
sensory receptive field
primary sensory neurons converge where
on one secondary sensory neuron
information form the secondary receptive field goes where
the brain
convergences allows multiple stimuli to sum where
postsynaptic (secondary) neuron
The size of the secondary receptive field determines
how sensitive the given area is to the stimulus
two point discrimination varies with
size of the secondary receptive field
small areas like fingertips relationship with receptive fields
smaller field, 1:1 relationship between primary and secondary neurons
clinically two point discrimination is used
to test the integrity of the dorsal column system
what is the dorsal column system
central pathway for touch and proprioception
where is the site of decussation for the DCML
level of the medulla
spinothalamic (anterolateral) tract function
conveys pain and temperature sensory input
where is the site of decussation for the spinothalamic tract
level of the spinal cord
clearinghouse for all information that wants to get into the cortex besides olfactory
thalamus
DCML and ST relay info via
thalamus
what do lesions in somatosensory cortex do
impair somatic sensation, and electrical stimulation evokes somatic sensations in specific parts of the body contralaterally
somatotopic map represents
aka homunculus, body surface
the amount of cortex representing a given area reflects
importance of the sensory input
most common symptoms patients seek medical attention for
pain
sensation of pain alerts to
real or impeding tissue injury and triggers appropriate protective responses
pain involves what complex experiences
transduction of noxious environmental stimuli and cognitive/emotional processing of the brain
delta fibers
relay primary pain, myelinated, and have a larger diameter that C fibers
acts as major neurotransmitters in nociceptive pathways
substance P, glutamate, and calcitonin
free nerve endings responsible for transduction of painful stimuli express a large array of _____ and ______
receptors and channels
transduce into electrical activity by specific ion channels sensitive to heat, mechanical stimuli, protons and cold
noxious stimuli
Noxious stimuli pathway
spinal cord- central pathways- cortex
TRP (transient receptor potential) channels
most aggressively pursued drug target, modulated by low pH, activated by noxious heat and capsaicin
chronic exposure to capsaicin can cause
degeneration of epidermal nerve fibers
capsaicin exposure
first stimulates, then desensitizes TRPV1 channel
chronic nociceptive pain can be referred to as
inflammatory pain
nociceptive pain is caused by
tissue injury and stimulation of nociceptors
components of “inflammatory soup”
bradykinin, prostaglandins, serotonin, nerve growth factor, ATP, H+
what does inflammatory soup do
activates specific receptors of nocioceptive fibers igniting neurogenic inflammation
nociceptive fibers relay painful stimuli to brain and participate in inflammatory response
neurogenic inflammation
stimulation of C fibers releases
substance p and calcitonin gene
what does substance P and calcitonin gene release do
induce vasodilation, leakage of proteins and fluid from blood vessels, edema, activation of mast cells,
what is substance P
peptide neurotransmitter that functions as the vomitting center in the medulla
substance P receptor
Neurokinin 1
substance P works with what in the nociceptive pathway
calcitonin and glutamate
Brain has a built in
analgesic system
stimulation of the analgesic pathway leads to release of
endogenous opioids
