Sensory Receptors and PNS

Frage	Antworten
Sensory receptors detect what?	Various stimuli and produce receptor potentials
Sensory receptors are based on?	Type of stimuli they are most sensitive to
Chemoreceptors sense?	smell, taste, PH, metabolite concentration (chemical)
Photoreceptors are for what?	Retina
Thermoreceptors sense what?	Temperature
Mechanoreceptors sense what?	physical deformation, touch, muscle tension, auditory vestibular receptors
Noriceptors sense what?	pain
Which of the receptors is most varied?	Mechanoreceptors
When multiple receptors combine, what kind of sensation is produced?	Richer and more complex
Is somatosensation varied?	Yes
What are some divisions of somatosensation?	Mechanical, chemical, thermal
Somatic sensory system mediates what?	The most diverse range of sensations
What are examples of somatic sensory sensations?	fine touch, crude touch, pressure, proprioception, heat, cold, pain
What are the most sensitive types of receptors?	Mechanoreceptors
All sensations are transducer by specialized PNS/CNS receptors?	PNS
How are sensations transducer?	From PNS to specific CNS targets
What are anatomically and functionally distinct for the variety of receptor systems?	Their neural pathways.
Where does somatic sensation arise?	from activity at endings of sensory nerve fibers - denritic process
Somatic sensation arises from nerve fibers in two places... __ and __.	Skin and muscle
Where do cell bodies of sensory neurons reside? (two places)	ganglia alongside spinal cord and brainstem
What are the two ganglia where sensory neurons reside?	Dorsal root ganglia and cranial nerve ganglia
Action potentials generated at the peripheral end along what fiber past a cell body and terminate where?	In the terminal CNS structure
What is transduction?	Conversion of one form of energy into another
Transduction converts ___ into ___. (electrical stimulus, physical stimulus, mechanical stimulus, chemical stimulus)	physical stimulus into electrical signal
Transduction requires a stimulus to be converted so what system can understand it's impulse?	Nervous system
What is sensory transduction?	Conversion or pressure, touch, heat, etc. into neural impulse
What is one form of energy?	Stimulus
What are examples of receptor potentials?	heat, pressure, pain, touch...
Nature and location of a stimulus indicate what?	What receptors will respond
What is needed to indicate the size and duration of the receptor potential produced?	Intensity and duration
Intensity can be?	low or high
Are all receptors the same in sensitivity?	No; some are more and some are less.
Do all receptors produce long or short responses?	Varied.
Can a receptor produce a short response even if the stimulus is maintained?	Yes.
Do receptors respond to a variety or stimuli?	No; they respond to only one kind.
How are receptor potentials produced? (ion channels)	Opening and closing of channels.
Sensory receptors are analogous to what?	postsynaptic membranes
Most post synaptic membranes and their adequate stimulus can be analogous to what?	Neurotransmitters
If a receptor contacts the next cell that is close to the site of transduction, what happens?	the receptor potential can modulate the rate of neurotransmitter released, causing a postynaptic potential and a change in action potential frequency.
If a receptor is far from the next cell, the receptor potential will do what?	Die out; but usually it can cause an action potential in the receptor. The frequency of the action potential is also modulated by the receptor potential.
What is the difference between a close and far receptor potential?	Whether a synapse will occur.
Can a receptor potential become an action potential?	Yes.
Define what a receptive field is?	particular areas in the periphery where application of an adequate stimulus causes them to respond.
Does a receptive field respond to everything?	No; stimulus must be big enough to trigger the field.
Are receptive fields the same size?	No; can be big or small.
When there is no obvious spatial domain in a receptive field, how does it sense stimuli?	the array of receptors have a systematic representation of parameters (i.e.: sound in the cochlea and auditory cortex).
What does a receptive field require to notice a stimulus? (2)	1. have to be big enough to be detected 2. has to be within the receptive field to be detected.
Receptive fields correspond to: efferent/afferent fibers?	Afferent.
Receptive fields correspond to single/multiple afferent fibers?	single
Which has smaller receptive fields: fine touch/crude touch	Fine
Where do fine touch have small receptive fields than crude touch?	because of fewer branches and denser innervation
What receptive fields are the finest?	lips, tongue, fingers
Give an example of a receptor field with spatial domain?	Fingers, lips, tongue.
give an example of an area with no spacial domain?	hair cells (the respond to frequency)
Do neuros in high orders (such as the thalamus or cortical neurons) have receptive fields?	Yes
Are higher order RF more or less complex?	More.
What does the visual cortex respond to?	edges with particular orientation
How can you test for a receptive field?	A two point discrimination test
What do you use to do a two-point discrimination test?	Calipers
If a caliper has a perception of two points, what does this indicate?	Activation of different fibers
If a caliper has only one point indicated, what does this mean?	The two points are within one receptive field
Sensory receptor adaptation: become more/less sensitive during maintained stimulus?	Less
What is the exception of becoming less sensitive to a stimulus with continued exposure?	Pain (nociceptors)
What are slowly adapting receptors suitable for?	static position, size, shape, duration
What are rapidly adapting receptors good for?	change and movement of stimuli
Adaptation takes place at CNS/PNS level?	PNS
Does the CNS regulate sensitivity of receptors?	Yes; moment-to-moment basis
What does the CNS do to regulate moment-to-moment sensitivity?	controls amount of light to retinas
CNS control over sensitivity or receptors is bottom up / top down / both?	Top down control
Slowly adapting sensitivity, is short/long; continual/fades?	Long, continual
Rapidly adapting sensory response is short/long, continual/brief?	short, brief
Afferent fibers of different receptors also differ in what?	diameter myelination
What does the largest afferent supply?	Receptors in muscles
What do intermediate diameter fibers mediate?	touch
What do the smallest afferent fibers mediate?	Temperature and pain
How many kinds of touch receptors do we have?	4
What are the four kinds of touch receptor sensory function?	proprioception, touch, pain/temperature, pain/temperature/itch
Receptor type: muscle spindle function?	proprioception
receptor type: free nerve ending and the smallest kind. function?	pain/temperature/itch
receptor type: merkel, meissner, pacinian, and ruff ini cells. function?	touch
Receptor type: free nerve ending, A theta function?	pain and temperature
What is the largest receptor type based on axon diameter?	muscle spindle
Second largest sensory fiber axon diameter belongs to what receptor type?	merkel, meissner, pacinian, ruffini
Do both free nerve endings have myelin?	No; smallest does not
Are all afferent fiber endings covered in myelin?	No. Some are and some aren't.
Encapsulated means?	have layers of myelin
What do capsules serve to do?	mechanical filter, modifying the mechanical stimuli before it reaches the end.
Afferents with specialized/encapsulated receptors are: slow/rapidly adapting and generally have lower/high thresholds for AP?	rapidly, lower
Where ar free nerve endings (non encapsulated) found?	formed by branching terminations of sensory fibers in the skin... no obvious specialization around them. Found throughout the body.
What are the four kinds of tactile receptors in the skin?	Meissner, merkel, ruffini, pacinan
If a receptor has a bigger field, density will be higher/lower?	Lower
If a receptor has a high density, the field will be bigger/smaller?	Smaller
What are the two big receptor field cells?	Pacinian and Ruffini
What are the two smaller receptor fields?	Merkel and Meissner
Merkel sensory function?	Form and texture perception
Meissner sensory function?	Motion detection; grip control
Pacinian sensory function?	Tool use; perception of distant events
Ruffini sensory function?	Hand shape, motion, direction
Which has a smaller receptive field, merkel or meissner?	Merkel (9mm)
Which cell has a receptor field of the entire finger/hand?	Pacinian
Merkel cells are rapidly/slowly adapting fibers?	Slowly
Merkel cells account for 15, 25, 35 % of mechanoreceptors in the hand?	25%
Where are Merkel cells most densely located?	fingertips
Merkel cells have high spatial resolution for detecting what? (3)	edges points curvature (texture)
Meissner cells are slowly/rapdily adapting?	Rapidly
Meissner account for 10, 30, 40, 60% of receptors in hand?	40%
Meissner receptor field is bigger/smaller than Merkel?	Bigger
Meissner is most sensitive to skin ___?	Deformation
Meissner is highly sensitive to ___?	Vibration (motion detection when things move across the skin)
Detecting slippage between skin and object is a role for: Merkel, Meissner?	Meissner
Pacinian receptor field is slowly/rapidly adapting?	Rapidly
Pacinian accounts for , 5, 10, 15% of receptors in the hand?	15%
Pacinian is an onion like structure found where in the hand?	Deep
Pacinian is most sensitive to what?	Tiny skin displacements, such as detecting tiny vibrations from tool use
Ruffini is a slowly/rapidly adapting receptor?	Slowly
Ruffini accounts for 10, 15, 20, 25% of receptors?	20%
Ruffini provides information about what?	hand shape and finger position; sensitive to movements
Do non-nociceptive thermal receptors discharge at greater rates if pain is induced?	no
When do nociceptors respond?	When stimulus reaches intensive levels and continues to increase
How many types of pain conduction fibers are there?	2
What are the two types of nociceptors?	A delta and C fiber
Which pain fiber is this: rapidly conducting; respond to dangerously intense mechanical and/or thermal stimuli; thinly myeliniated; more selective to the type of stimuli?	A delta; "first pain" or "delta pain"
Which pain fiber is this? is unmyelinated, polymodal and respond to thermal, mechanical, and chemical stimuli	C fiber - "slow pain" or "aching pain"
Which responds to more kinds of stimulus: a delta or c fiber? why?	C fiber. Unmyelinated and slower.
Which respond to sharp first pain?	A delta
Which pain is diffused and lasts longer?	C fiber pain
Pain pathways are located where?	Dorsal root ganglia and cranial nerve ganglia
Pain enters the spinal cord, processes run up and down several levels to provide contact with what?	1st neuron
What do second order neurons do in pain pathways?	Decussate and ascent in ventrolateral quadrant of spinal cord
Spinal cord carries pain to where?	Medulla
Pain ends in the ___ (location) call ___ (tract)	anterolateral system and spinothalamic tract
Does the pain pathway always/sometimes/never decussate?	Always
Does pain decussate in dorsal?	No... in spinal cord 2nd neuon
Proprioception is about information received from?	limbs, muscle force, muscle tension, joint stress
What is another meaning for proprioception?	receptors for self
Vestibuloreceptors convey information about what?	head position
We understand proprioception from studying what?	Muscle spindles
Muscle spindles are found in most skeletal muscles EXCEPT? (2)	Face and larynx
Muscle spindle is a capsule of what?	specialized muscle fibers
Muscle spindles are activated how?	stretching of fibers
Jaw/tongue have sparse/dense muscle spindles?	Dense
Golgi tendon organs are activated how?	Changes in muscle tension
Are golgi tendon organs activated with high or low threshold mechanoreceptors?	low
Golgi tensors are between what?	muscle fibers and tendons
Muscle contraction ___ golgi tendon organs	stretches
there are few/many golgi tendon organs in the face/pharynx	few
Somatosensory information is _ neuron pathway?	3
Neuon pathway for somatosensory information is?	1. muscle spindle 2. spinal cord 3. thalamus
The spinal cord has how many types of sensation? What are they?	3. 1. propreoception 2. touch/pressure 3. pain
Which decussate? proprioception/pain/touch and pressure?	pain
Primary afferents carrying tactile and proprioceptive information synapse where?	posterior column nuclei of ipsilateral medulla
second-order neurons then cross the midline and form the?	meial lemniscus, and ascent to the VPL nucleus of thalamus
Third order neurons project the somatosensory information ?	cortex of the post central gyrus
Spinothalamic tract: has what	pain, temperature, and some touch/pressure afferents
spinothalamic tract: 2nd order fibers cross the midline forming? and ascent to?	spinothalamic tract VPL nucleus of the thalamus
Spinothalamic tract: thalamic cells project somatosensory cortex of the	postcentral gyrus, insula, and other cortical areas
Damage to the spinal cord at level of the ventral horn will cause diminution of ___ on the ___ side to the lesion and diminution of ___ to the ___ side of the lesion	touch on the ipsilateral pain to the contralateral
Damage rostral to the medulla would cause diminution of ___ and ___ on the ___ side of the lesion	pain and touch on the contralateral

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Sensory Receptors and PNS

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