Flashcards in SDL-7 Sensory Receptors Deck (61):
It takes an average of _____ms to appreciate and react to an incoming stimulus.
_______________ are receptors that respond to stimuli arising from outside the body. May be divided into two subgroups:
II. Contact receptors
______________ are receptors that detect signals originating some distance from the receptor (e.g. light detected by the eye, sound by the ear, and chemicals by the nose).
_____________ are receptors that detect signals impinging on the external skin such as touch, pressure, heat, and cold.
_____________ are receptors that are sensitive to signals from within the body, such as viscera, blood vessels, etc.
_____________ are receptors that detect signals from somatic structures which contribute to our sense of orientation and movement of the body in space (e.g. angle of limbs).
A specific modality of stimulus that a receptor is highly sensitive to is referred to as the ______________.
Adequate stimulus or specific energy
The theory that receptors are highly sensitive to one specific modality of stimulus is known as the ____________ theory.
Specific nerve energy
The ___________ theory states that sensation results from differing patterns of action potentials produced in a single sensory fiber.
The intensity of a stimulus is coded in a single nerve fiber by the (amplitude/frequency) of action potentials.
Most neurons are spontaneously active even when an action potential is not present. This rate of spontaneous activity represents a set point and is referred to as ______________.
As the strength of a stimulus increases, receptors with (higher/lower) thresholds are recruited to the synapse.
The absolute intensity of a stimulus involves the _______________________ and ___________________________.
I. Firing frequency of receptor nerve fibers
II. Number of receptor fibers carrying the signal
The initial signal that depolarizes a membrane is the ______________.
TRP receptors are non-specific, but the inward driving force for (Na+/K+/Cl-) is greater than the others, resulting in membrane depolarization.
_____________ is either a decrease or complete cessation of response of a receptor to a continuing or repeated stimulus.
Receptors capable of completely adapting to a stimulus are (phasic/tonic) receptors.
Receptors that continue their activity as long as the stimulus is present are (phasic/tonic) receptors.
____________ refers to a decrease in reflex action or to a decrease in awareness of a continuing or repeated stimulus due to decreased responsiveness of central neurons.
(T/F) Habituation involves changing the strength of associated synapses which results in altered afferent input.
The ____________ of a single neuron is the area of body from which stimulation influences the neuron's discharge rate.
How is the two point discrimination test conducted?
Two point discrimination is done by touching the skin with one or two points and asking the subject to tell how many points were used. When the two points are less than a threshold distance apart, the subject will report feeling one point.
What is an example of the wide variety of two point discrimination thresholds in the body?
Two point discrimination threshold distance is about 1mm on the fingers, compared to about 40mm on the back.
The cell body of each primary somatosensory neuron is located in a (dorsal root/ventral root) ganglion of the ______________.
Dorsal root ganglion of the spinal cord
Primary somatosensory neurons are (unipolar/bipolar/pseudounipolar).
Mechanoreceptors are exteroreceptors that detect the ___________ and/or ____________ of the skin by mechanical stimuli.
Displacement and/or velocity (rate of displacement) of skin
Nociceptors are exteroreceptors that detect ____________ stimuli.
Mechanoreceptors have afferent fibers in the ____ range.
Aβ (group II)
Aα(Ia) fibers are sensitive to ___________ and ___________.
I. Limb position
Aβ(II) fibers are sensitive to _________, _________, and _________.
Aδ(III) fibers are sensitive to ____________ and __________.
I. Fast pain
C(IV) fibers are sensitive to _____________ and __________.
I. Slow pain
Nociceptors have fibers in the ____ and ____ range.
(T/F) Mechanoreceptors are only present in glabrous skin.
False. Mechanoreceptors are present in both hairy and glabrous skin.
Merkel's disks and Ruffini's endings are examples of (nociceptors/thermoreceptors/mechanoreceptors).
_____________ are slowly adapting mechanoreceptors that respond to small displacements of the skin.
____________ are mechanoreceptors that respond to indentation of the skin directly over their receptor.
In hairy skin, _________ and _________ detect velocity of displacement in skin.
I. Hair follicle endings
In glabrous skin, ____________ detect velocity of displacement of skin.
Meissner's corpuscles detect (low/high) frequency vibrations, typically between __-__ Hz.
Low frequency vibrations; 5-40Hz
A ____________ is a mechanoreceptor that detects primarily vibration of higher frequencies, between ranges of __-__Hz.
Pacinian corpuscle; 60-400Hz
The most sensitive of the tactile mechanoreceptors is (Merkel's disk/Pacinian corpuscle/Ruffini's endings).
Most unmyelinated nociceptors respond to mechanical, thermal, and chemical stimuli. Since they respond to multiple stimuli, they are referred to as ___________ receptors.
(Aching/Burning/Pricking) pain is quickly felt, transmitted by Aδ fibers, can be accurately localized, and subsides quickly.
(Aching/Burning/Pricking) pain arises from deeper tissues and is often difficult to localize.
(Aching/Burning/Pricking) pain is slow in onset, transmitted by C fibers, less able to be precisely localized, and can persist for many seconds after removal of the stimulus.
(T/F) Pricking pain is often more difficult to endure than the other types of pain, evoking reflex increases in heart rate and respiration.
False. Burning pain is more difficult to endure and responsible for these effects.
A skin injury is often followed by the triple response which entails:
I. Local reddening
II. Red flare
III. Formation of a wheal on the skin
(T/F) The nerve fibers for both warm and cold sensation are myelinated.
False. The nerve fibers for cold sensation consist of myelinated and unmyelinated fibers, while the fibers for warm sensation are not.
Visceral receptors primarily respond to:
II. Noxious stimuli
Muscle stretch receptor organs (muscle spindles) contain modified skeletal muscle fibers known as _________________.
Intrafusal muscle fibers
Intrafusal muscle fibers are innervated near both ends by (alpha/beta/gamma) motoneurons, while extrafusal muscle fibers are innervated by (alpha/beta/gamma) motoneurons only at the midpoint of the fibers.
Intrafusal - Gamma motoneurons
Extrafusal - Alpha motoneurons
________________ are the larger intrafusal muscle fibers in which cell nuclei are concentrated in a central region.
Nuclear bag fibers
________________ are the smaller intrafusal muscle fibers in which cell nuclei are arranged in a chain.
Nuclear chain fibers
Intrafusal fibers have two types of sensory nerve endings: _____ and _____.
Ia and II
In intrafusal muscle fibers, there is(are) typically (one/two/three/many) type Ia fiber(s) per spindle.
In the muscle, intrafusal fusal fibers are arranged (in parallel/perpendicular) to extrafusal muscle fibers.
In parallel to
When a muscle contracts and shortens, tension on the intrafusal muscle fibers is reduced and firing decreases. How is optimal tension maintained in this situation?
When tension on intrafusal muscle fibers is decreased due to muscle contraction, gamma motor neurons that are linked with alpha motor neurons activate the intrafusal muscle fibers and cause them to shorten in proportion with the length of the contracted muscle.
(T/F) The sense of limb position is most likely signaled by only cutaneous receptors in the skin.
False. The best information is that limb position is signaled by a combination of skin, muscle, and joint receptors.
Local anesthetics, such as procaine, block __ fibers first in the transmission of an action potential.