Topic 3: Sensory Receptors Flashcards
A ________ ________(organ) is a structure that recognizes a stimulus.
Sensory receptor
A ________ is a detectable change in the internal or external environment.
Stimulus
Under the appropriate circumstances, a receptor can transducer (convert) the stimulus into a _____ signal. These signals are then carried into the CNS to be analyzed.
Nerve
T/F: A sensory receptor may be a specialized portion of the neuronal membrane, a separate cell associated with a neuron ending, or a group of such cells. Sometimes the receptor and the neuron itself are together referred to as a receptor.
True
Each sensory receptor responds most readily to one particular form of energy. This is called its ________ ________.
Adequate stimulus
__________ : the magnitude or intensity that must be exceeded for a certain reaction or condition to occur.
Threshold
T/F: Receptors can only respond to their adequate stimulus.
False: Receptors also respond to forms of energy other than the adequate stimulus, but the threshold for these nonspecific responses is much higher.
__________ is the process by which stimuli are converted to action potentials (APs) by sensory receptors.
Transduction
__________ is the process by which nerve signals enter and ascend the CNS in various tracts.
Transmission
_________ is the process by which electrochemical activity from other ascending inputs for example, touch, or signals descending from the brain (via emotions) can increase or decrease sensory transmission. In this manner the intensity of sensory input to the cerebral cortex can be controlled.
Modulation
__________ is the process which results in subjective feelings. It is a poorly understood combination of transduction, transmission, and modulation. It can be altered by many phenomena including sleep and emotions such as fear, rage, and depression.
Perception
T/F: All unipolar neurons are attached to some sort of
sensory receptor.
True
All unipolar cell bodies form a cluster called a ______ ____ ________ at every level of the spinal cord.
Dorsal root ganglion
Unipolar neurons enter the ______ ____ at each level and on both sides of the spinal cord.
Dorsal horn
Unipolar neurons in cranial nerves that have a sensory component, for example CN V, also have _______.
Ganglia
__________ _________ is the smallest amount of change needed in a stimulus before a change is noticed.
Difference threshold
_______’s ___ states that the change needed to notice a difference between two stimuli is proportional to the original intensity of the stimulus.
Weber’s Law
Every receptor has a defined area in the periphery, over which it can receive input. This is called the _______ _________, and each one is the responsibility of a single axon.
Receptive Field
_______ __________ is the ability to accurately locate the site of stimulation and to detect that neighbouring stimuli are actually separate.
Spatial discrimination
_______ _________ depends in part on the density of receptors and the size of the receptive fields in a particular skin region.
Tactile sensitivity
More sensitive areas have _______ fields and a _______ concentration of receptors.
More sensitive areas have smaller fields and a higher concentration of receptors.
The ____-______ threshold is the minimal distance in which two separate stimuli can be distinguished as separate.
Two-point
In different parts of the skin, the concentration of the various sensory receptors changes and this accounts for varying abilities in _______ _________ in different regions.
spatial discrimination
On the back, the density of tactile receptors is greatly _______, and spatial discrimination is relatively ____.
On the back, the density of tactile receptors is greatly reduced, and spatial discrimination is relatively poor.
A ___________ is an area of the skin that is a combination of the adjacent receptive fields of the sensory receptors of a single nerve. They are named according to the peripheral nerve which supplies them.
Dermatome
T/F: Dermatome maps are incredibly accurate and there is very little overlap.
False!! There is considerable overlap. This means that the loss of a single nerve root rarely produces significant loss of skin sensitivity.
_________ _____s are found in small patches in the distal extremities.These are distinct and non- overlapping areas of skin.
Autonomous zones
_____ __________ have a confusing arrangement stemming from limb rotation during development at about 5 weeks as an adaptation to the erect position.
Limb dermatomes
Dermatomes are useful in localizing the site of damage in the spinal cord and brainstem particularly in __________ (caused by compression, inflammation and/or injury to a spinal nerve).
Radiculopathy
A _______ ____ with nerve compression is by far the most common cause of a radiculopathy.
Herniated disc
Viruses that infect spinal nerves, such as herpes zoster infections (shingles), can reveal their origin by showing up as a painful (unilateral) _________ area.
Dermatomic
______ _____, a virus that can be dormant in the dorsal root ganglion, migrates along the spinal nerve to affect only the area of skin served by that nerve (dermatome).
Herpes zoster
The receptors that respond best to change are called fast adapting receptors or ______ receptors, for example, olfactory receptors.
Phasic
_________ is the decrease in sensory receptor sensitivity during a long-lasting stimulus.
Adaptation
_____ receptors or fast adapting receptors are in part responsible for the fact that we can cease paying attention to constant stimuli.
Phasic
Receptors which continue to respond throughout the duration of a prolonged stimulus are termed slow adapting or _____ receptors.
Tonic
In this way they convey information about the duration of the stimulus. An example of a tonic receptor is a _________.
Nociceptor
______________ are the largest category of sensory receptors and respond to a deformation in a body part. This group includes haptic receptors, receptors that are involved in contributing to the perception of touch.
Mechanoreceptors
______ ________ (endings) detect skin stretch, deformation within joints. They monitor slippage of objects along the surface of the skin, allowing modulation of grip on an object.
Ruffini terminals
_______ corpuscles detect transient pressure and high-frequency vibration.
Pacinian
_______ corpuscles are rapidly adapting touch receptors.
Meissner’s
_ _______ _____have been linked to pleasant touch and are most responsive during slow gentle stroking in hairy skin.
C tactile fibres
_____ hair is the fine, wispy hair that covers most of the body. C-tactile touch receptors wrap half -way around the base of hair follicles. This enables them to detect deflection in one direction versus the other for example to help notice a potentially dangerous insect. That is why stroking against the grain feels different.
Vellus
The ______ is involved in processing pleasant, “slow” touch, taste (especially disgust), pain and emotion.
Insula
The ___________ cortex (of the parietal lobe) responds to spatial location, pressure and pinpricks.
somatosensory
__________ are receptors that detect noxious or potentially damaging stimuli. They are often called free nerve endings because unlike other receptors they are not surrounded by connective tissue.
Nociceptors
T/F: The term nociceptors can also include the afferent neuron attached to them.
True
Nociceptors respond to stimuli that could potentially ______ the body, such as extreme heat or cold, pressure, pinching, and chemicals.
Damage
T/F: Nociceptor is an AKA for a pain receptor.
False: The signals they pass on to the brain often but not always result in pain perception.
____________ refers to a signal arriving at the CNS as a result of stimulation of nociceptors. It is the physiological process by which body tissues are protected from damage.
Nociception
__________ pain implies damage to the nervous system itself, due to disease or trauma.
Neuropathic
________ ____ is defined as pain perceived at a location other than the site of the painful stimulus. In other words, your brain misperceives the location of the pain.
Referred pain
Your ________ is a four-inch, pear-shaped organ when full of bile. It is positioned under your liver in the upper-right section of your abdomen. It stores bile which allows some nutrients to be more easily absorbed into the
bloodstream.
Gallbladder
The gallbladder lies next to the right ________, therefore inflammation can spread to the __________.
Diaphragm
The right _______ nerve from the diaphragm enters the CNS via the right spinal nerves at C3, 4 & 5.
Phrenic
Afferent signals from the right shoulder, dermatome _, also converge on spinal nerve roots C3-5.
Dermatome 4
A _______ is a fast, predictable sequence of involuntary actions. It occurs in response to certain stimuli. The example above is the famous “Knee Jerk”
Reflex
Reflex ____ are anatomic pathways having afferent and efferent components that carry out reflex responses.
Arcs
In a reflex arc, a receptor transduces stimuli to APs, then an afferent neuron that carries APs to ___________ (the stretch reflex is the only monosynaptic reflex). Efferent neurons then carry APs to Effectors (muscles or glands).
Interneurons
Reflexes form the basis of all ____ motor activity. They occur at all levels of the _____. Important bodily functions such as respiration, digestion, posture, defensive movement, micturition, sexual function, and walking are controlled through reflexes.
CNS
Most powerful activities involve a ____________ during which the muscles involved are first stretched and then shortened to accelerate the body or limb.
Countermovement
___________ is the ability to know where your body is in space without the use of vision. The category of proprioceptors includes muscle spindles.
Proprioception
The ______ _______ is a sensory receptor that monitors a change in the length of a muscle and how fast it is being stretched.
muscle spindle
The ______ ______ is an involuntary muscular contraction in response to a fast stretch of the muscle.
stretch reflex
Muscle Spindles are ________ in shape meaning they bulge in the middle and taper at both ends.
fusiform
_________ fibres are tiny muscle fibres that are located inside the muscle spindle. They are miniture versions (4-10 mm) of extrafusal muscle fibres, all the same microspcopic stuffings - myofibrils, myofilaments (actin & mysosin).
Intrafusal
_________ muscle fibres are located outside the muscle spindle. In other words they are normal skeletal muscle fibres.
Extrafusal
Muscle spindles are found in greatest abundance in muscles capable of delicate, fine, contractile activity like in the ____ and ____.
Hand and foot
___ is the name given to the sensory neurons that carry a nerve impulse to the CNS. They respond to a change of length in the muscle spindle.
Ia
T/F: If the extrafusal fibres are being stretched then the Intrafusal fibres of the muscle spindle inside them are also being stretched.
True
_____ _____ ______ are motor neurons that innervate extrafusal muscle fibers. Extrafusal fibres are the normal skeletal muscle fibres that surround the muscle spindle and allow you to move.
Alpha Motor Neurons
_____ _____ _______ are motor neurons that innervate intrafusal fibres.
Gamma Motor Neurons
For patients with excess “_____ ____”, the 1a sensory endings within muscle spindles are discharging too frequently causing there to be more muscle activity than appropriate. This hyperactivity can cause spasticity.
“gamma bias”
___________ is defined as overresponsive reflexes.
Hyperreflexia
The _____ ______ _____ is a proprioceptive receptor that is located within the tendons found on each end of a muscle. It responds to increased contraction exerted on the tendon, by inhibiting further muscle contraction.
Golgi Tendon Organ
