chapter 15 sensory pathways & somatic nervous system Flashcards
(47 cards)
what are the 3 sensory receptor types
1) exteroreceptor: monitor external environment
2) interoreceptor: monitor visceral orgnas/ internal environment
3) proprioreceptor: monitor position of skeletal muscles & joints
Where in the brain does this sensory info & visceral sensory info go to?
- the sensory info goes to “cerebrum” & cerebellum
- the visceral sensory info goes to brain stem & diencephalon
how does the sensory pathway work in somatic nervous system?
the tract:
1. general sensory receptor goes to sensory pathways and the sensory processing in centers in brain (afferent)
2. concious and subconscious motor centers in brain to motor pathways (efferent)
- somatic nervous system (SNS)»_space; skeletal muscles
- autoomic nervous system (ANS)»_space; visceral effectors (smooth muscles, glands, cardiac muscle,a dipocytes etc)
what are sensory receptors?
Structures that monitor changes in specific variabels inside & outside the body
- usually specific receptors are at end of an afferent neuron
- each receptor responds to specific type of stimulus
= receptor specificitiy (e.g. pressure receptors are stimulated by pressure)
- you have 2 types of senses: general & special
what are general senses?
temeprature, pain, touch, pressure, vibration & proprioception (muscle stretch)
general sense receptors: are usually teh dendrites ends of an affernet (sensory) neuron in dermis or in stratum basale (the deepest epidermis layer)
the types of general sense receptors
- free nerve endings: pain, touch, pressure, temp (e.g. tactile receptors)
- root hair plexus
- merkal cells and tactile discs: fine touch & pressure
- tactile corpuscle (Meissner’s) [=little body]: light touch & pressure
- lamellated corpuscle (pacinian): deeper pressure/ wrapped by fibrobalst
- ruffini corpuscle (bulbous): distortion
What are special senses?
olfaction (smell), vision, gustation (taste), equilibrium (balance), hearing
- receptors are more complex; & are located in sense organs (e.g. eye, ear and tongue)
what is a detection of the stimulus
an adequate stimulus acting on a sensory receptor causes a change in the membrane’s permeability
- which leads to the generation of the receptor cell’s graded depolarizaiton/ hyperpolarization = receptor potential
- Generator potential = a depolarization of the sensory neuron (= the receptor cell in general senses, 2nd cell in special senses)
- transduction = process of translating stimulus into an action potential (change the chemical info into electrical info)
where is stimulli detected in general senses
in general senses:
- stimuli detected at the receptive endings of sensory neruons
- unipolar
where is stimuli detected in special senses
in special senses:
- specialized receptor cells are required
- receptive endings of olfactory neruons (smell)
what is range of detection
- the number and type of sensory receptors we have limit what we can sense and become aware of
- each of us is unique in our sensory abilities
what is a receptive field?
area of body monitored by “one” particular afferent neuron and all its receptors
- 2-point discrimination test: to assess if the patient is able to identify 2 close points on a small area of skin, how fine the baility to discriminate this are
3 interpretation types of sensory information: sensation, perception and not perceived
to generate conscious sensations, sensory info must be transmitted to the cortex (cerebral cortex):
- sensation: raw experience; may be unconscious/ activity in any & all sensory neurons
(every sense coming into brain)
- perception: SNS (1% of all sensation); interpretation, meaning given to sensation, conscious awareness of sensation / activity in cerebral cortex and not just spinal cord & brain stem
not perceived: visceral sensory info delivered to diencephalon, spinal cord & brain stem only (reflex)
- labelled line: pathway that conducts sensory info from a receptor to specific neurons in cortex
what is modality interpreted by?
modailty (type) of stimulus (e.g. touch, pressure, temp., sound) is interpreted by labelled line
- information ab the type, strength, duration and variation of the stimulus is coded by:
1) type of sensory receptor cell activated
2) the rate of action potentials generated (e.g. frequency, how long the sensation lasted)
e.g. the harder/ stronger the stimulus, the more action potentials generated (APs are more frequent)
where does sensory conding begin at?
what are the 2 general types of receptors
sensory conding begins at the sensory receptors
1. tonic receptors: always acticve; provide info about
- background level of stimulation
- changes indicated by frequency of action potentials generated
- called **slow adapting **receptors because they show little peripheral adaptation
- phasic receptors: not always active fire, only when stimulated, provide information ab:
- intensity and rate of ahcnge of stimulus
- called fast-adapting receptors becuase they respond strongly at first & then show decline in activity = peripheral adaptation
tonic receptor: e.g. the stimulation for pain; never be adapated
the receptors catagorized as tonic receptors
- ruffini corpuscle (pain receptors)
- merkel tactile receptors
- nociceptors
- joint capsule proproceptor
- muscle spindle (stretch centres)
the receptors categorized as phasic receptors
- pacinian corpuscles
- meissner’s corpuscles
- thermoreceptors
- root hair plexuses
what are the difference between peripheral/ central adaptations?
adaptation: reduction in sensitivity of nervous system to constant stimulus
1) perpheral adaptation: phasic sensory receptors become less responsive (e.g. become used to background noise, feeling of clothing, room temp)
2) central adaptation: receptors still responding but central adaptation, involved inhibition at various nuclei
- sensory info may still generate reflex responses, but no conscious sensation or perception; awareness is reduced (e.g. you get used to new odours in a room)
=higher centers can increase receptor sensitivity or facilitate transmission (e.g. RAS heightens awareness - listen carefully)
why does adaptation take place?
it’s theory!!!
: so that the brain is not overwhelmed and is not using up resources paying attention tothings that are not important»_space; allows the brain to focus on more important things
4 types of receptors of general senses
1) nociceptors: pain receptor
2) thermoreceptors: temperature monitor
3) mechanoreceptors: cell membrane (e.g. ion channel) stimuli
4) chemoreceptors: detect changes in pH, [O2], [CO2]
what is nociceptors?
= pain receptors, free nerve ending (dendrites)
location: superficial skin, joint capsules, periostea of bones, around the walls of blood vessels (pain)
respond to: extreme temp, mechanical damge, dissolved chemicals (e.g. chemicals released by damged cells)
- very strong stimuli will excite all 3 receptor types and lead to awareness of the same sensation: “burning feeling”
- slow adapting: tonic, feeling will last as long as stimuli
2 axon types carry pain info
1) type A fibers (faster, myelinated): prickling pain
2) type C fibers (slower, unmyelinated): burning/ aching pain
what is a themoreceptor?
= free nerve endings in the dermis, liver & hypothalamus- info sent along lateral spinothalamic pathway to thalamus and reticular formation (same as with nociceptors)
what is a mechanoreceptor?
respond to: stimuli that distort cell membrane, and mechanically open ion channel
1) tactile receptor: detect touch, pressure & vibration
2) baroreceptors: free nerve endings within elastic tissue, detect pressure changes in walls of blood vessels and in portions of the digestive, reproductive & urinary tract
3) proprioceptors: detect position of joints & muscles
- muscle spindles
- golgi tendon organs
- receptors in joint capsules = free nerve endings that detect pressure, tension & movement
what is a chemoreceptor?
detect changes in pH, [O2] and [CO2]
