CNS Class 2 - Sensory Review Flashcards
Information carried from the body’s tissues via receptors (about its internal and external environments) to the CNS.
Afferent/Sensory
T/F - There are about 20 times more efferent than afferent neurons in the human body.
False - There are about 20 times more AFFERENT than EFFERENT neurons in the human body.
Transmission of directive signals from the CNS to effectors in the body tissues, such as muscles or glands.
Efferent/Motor
The purpose of ________ data is to inform the CNS about what is happening inside the body and external to it so that this information can be processed or evaluated.
Afferent Data
The most straight forward type of response where incoming sensory information triggers an automatic efferent reaction without having to reach the brain.
Reflex
Reflexes can be very simple or more complex and their neural pathway of afferent neuron to interneuron to efferent neuron is called a ______ ___.
Reflex Arc
T/F - Spinal or withdrawal reflexes are able to initiate a response without input from the brain.
True
Afferent information that arrives in the brain processing centres receives more complex types of analysis relating to _______ and cognition.
Emotion
Data that is carried as afferent transmission along the neurons of the sensory system into the CNS for interpretation and response.
Sensory Input/Afferentation
Conscious awareness of sensation.
Sensory Experience (aka. Sensory Perception)
Since most afferentation does not rise to consciousness because it is filtered out or suppressed, only a percentage results in sensory __________.
Sensory Experience (aka. Sensory Perception)
_________ receptors detect ambient molecules and inform the CNS. If this data is selected for experience, the perception of it is called a _____.
Olfactory Receptors
Scent
___________ detect tissue stress or damage and convey this information to the CNS. At this transmission stage it is referred to as __________. Only when the person has a sensory experience of it is it called ____.
Nociceptors
Nociception
Pain
T/F - The presence of afferentation from the tissues means there will be sensation.
False - The presence of afferentation from the tissues DOES NOT mean there will be sensation.
All sensation is assigned by the _____.
Brain
Stimuli are detected in the tissues by receptors that are specialized for specific stimulus types. These receptors are the distal ends of afferent neurons called the _______ or _____ _____ neurons.
Primary/First Order
Neurons that convey the transmission to the spinal cord and their synapses occur either in the dorsal horn or farther up in the brainstem via cranial nerves.
Primary/First Order Neurons
Neurons in the chain that carry the afferentation data to the thalamus.
Secondary/Second Order Sensory Neurons
A reception or relay station for the brain and its crucial role in sensation is to convey data via the ________ or _____ _____ neurons.
Thalamus
Tertiary/Third Order Neurons
Neurons in the chain that convey data to the somatosensory cortex, which is part of the system that consolidates sensory experience, as well as to related brain areas for memory, emotion, cognition and autonomics.
Tertiary/Third Order Neurons
The anatomy can be different for the special senses and ________ sensation, compared to the pathway for somatosensation.
Visceral Sensation
The typical first order neuron is attached to one or more receptors (its specific type) that are embedded in tissue. These receptors have stimulus __________, and if the stimulus is strong enough an ______ _________ is initiated.
Stimulus Thresholds
Action Potential
The resulting depolarization wave from a stimulus travels along the axon of a first order neuron, which sits in the dorsal ____ ________.
Dorsal Root Ganglion
The axon from the receptor to the cell body of a first order neuron located in the peripheral nerve, and then the spinal nerve, that corresponds with their supply tissue.
Peripheral Branch/Process
The axon of a first order neuron that enters the spinal cord’s dorsal horn in the CNS.
Central Process
Each first order neuron’s receptor is located in the tissue it is responsible for sensing and reporting about, meaning that it generates information about a specific stimulus type occurring in a discrete location, referred to as its _________ _____.
Receptive Field
The peripheral branches of the first order neurons for a tissue area are bundled together into _________, which are then grouped together into a __________ nerve that is responsible for that tissue zone.
Fascicles
Peripheral Nerve
A tissue zone and its associated peripheral nerve give rise to an identified pattern of sensation responsibility that is called the nerve’s “______ _______.”
Supply Tissues
In relation to nerve supply tissues, there are smaller areas for which the nerve exclusively carries the ________ neurons, and larger zones where the nerve is the primary but not _________ supplier.
Afferent Neurons
Exclusive Supplier
First order neurons are in a different configuration once their __________ branches enter a ______ nerve.
Peripheral Branches
Spinal Nerve
Each ascending dorsal root axon, before reaching the spinal cord, __________ into ascending and descending branches entering several segments _____ and _____ their own segment.
Bifurcates
Below
Above
T/F - Peripheral nerves each carry a group of neurons that do not sense the same tissue zone, but report to the same spinal cord segment.
False - Peripheral nerves each carry a group of neurons that DO sense the same tissue zone, but DO NOT report to the same spinal cord segment.
The nerve that contains all the neurons whose functions correspond to one spinal cord level.
Spinal Nerve
The supply zone pattern is different for the same body tissues, depending on whether the ______ nerve or the __________ nerve pattern is what is clinically relevant in a case.
Spinal Nerve
Peripheral Nerve
A spinal nerve’s pattern of skin responsibility.
Dermatome
A spinal nerve’s pattern of responsibility relating to deeper structures such as bone, periosteum and joints.
Sclerotome
A term meaning “of the root.”
Radicular
The spinal nerve is the combination of the nerve _____ from that spinal segment.
Nerve Roots
The idea that humans have 5 senses has been around since Aristotle, but in fact there are at least __ identified sensory modalities.
17
Sometimes sensory modalities are viewed by the experts as ________ senses (e.g. itch), while other believe in _________ senses that integrate several sub-modalities (e.g. itch is a sub-category of pain).
Separate Senses
Principal Senses
The term used when a sense has receptors distributed throughout the body in various tissue types.
General Sense
T/F - Pain, temperature and motion are all examples of special senses.
False - Pain, temperature and motion are all examples of GENERAL senses.
These senses have receptors located in one part of the body and have a special sense organ dedicated to them. They often have specific dedicated interpretation areas in the brain as well.
Special Sense
T/F - Vision, smell, hearing and tase are all examples of special senses.
True
Experts often disagree about how to categorize senses such as _____ and equilibrium because they are clearly principal sensory categories, but they don’t have distinct _________.
Touch
Receptors
A sense that integrates data from several receptor types, including temperature, light/deep pressure, vibration, stretch, hair movement and nociception.
Touch (aka. Somatosensation)
A sense that integrates data from several receptor types, including body position, effects of movement and balance/centre of gravity forces.
Equilibrium
T/F - Whether a general, specific or integrated sense, all are premised on information collected by receptors located in the body’s tissues.
True
Receptors in the body’s tissues are in contact with and impacted by _______.
Stimuli
_________ are the sensory end-organ that registers stimuli, and they have the capacity to _________ the energy of the stimulus.
Receptors
Transduce
A process in which stimulus energy is transformed into an action potential that travels along the first order neuron towards the CNS.
Sensory Transduction
Each receptor has sensitivity to a particular stimulus type called its ________ stimulus.
Adequate Stimulus
Receptors can be __________ in a number of ways, including:
- Adequate stimulus
- Morphology
- Rate of adaptation
- Firing threshold
Classified
Receptor type associated with mechanical forces as applied to tissue (e.g. pressure, stretch/distortion, tension).
Mechanoreceptors
Receptor type associated with temperature relative to tissue temperature (e.g. heat, cold).
Thermoreceptors
Receptor type associated with potential or actual tissue damage, as well as potential damage from beyond threshold stimuli (e.g. extremes of cold/hot, excess pressure/mechanical deformation, range of chemicals)
Nociceptors
Receptor type associated with sense of position (e.g. placement, stretch, effects of movement).
Proprioceptors
Receptor type associated with sense of movement.
Kinaesthetic Receptors
Receptor type associated with humidity.
Hydroreceptors
Receptor type associated with fluid osmolality (e.g. solute concentration, water-electrolyte balance).
Osmoreceptor
Receptor type associated with pressure in blood vessel walls (e.g. increased/decreased wall deformation).
Baroreceptors
Receptor type associated with range of chemicals, ions and macromolecules (e.g. taste/odour, noxious).
Chemoreceptors
Receptor type associated with electrical fields.
Electroreceptors
Receptor type associated with electromagnetic fields (e.g. light, infrared, ultraviolet).
Electromagnetic Receptors
Receptor type associated with magnetic fields.
Magnetoreceptors
Receptor type associated with chemoreceptors and mechanoreceptors in organs (e.g. report information about visceral structures via ANS reflexes or directly to hypothalamus).
Visceroreceptors
T/F - Sensory experience of viscera usually only occurs when there is something functioning properly, never the result of nociception.
False - Sensory experience of viscera usually only occurs when there is something WRONG , USUALLY the result of nociception.
Sensory receptors fall in 3 main groupings based on their __________:
1) Free Nerve Endings
2) Encapsulated Receptors
3) Specialized Cells
Morphology
These receptors are very common and are found extensively in the skin, as well as most other structures. They are used to sense nociception, temperature and hair follicle movement. They typically have several sensing ends per neuron that are embedded directly in their tissues.
Free Nerve Endings (aka. Bare, Naked, Unmyelinated)
These receptors have “bare” endings, but they are encapsulated in a structure that acts to attune them to specific stimuli. This helps lower their firing threshold for it (e.g. detecting the vibration caused by light touch, sensitivity to ranges of deformation, pressure & stretch).
Encapsulated Receptors (aka. Protected, Bulbous, Lamellar/Lamellated, Tactile)
These receptors are complex distinct cells that synapses with first order neurons and are used for special senses (e.g. vision, taste).
Specialized Cells
A term referring to the priority of the sensory system to keep track of new or worrisome stimuli (e.g. an identified benign stimulus typically loses signal intensity quickly).
Adaptation
This receptor adapts slowly to a stimulus and continues to produce action potentials for the duration of the stimulus (e.g. nociception, joint capsule stretch, baroreception). Monitor parameters that must be continually evaluated.
Tonic Receptor
T/F - Some tonic receptors are permanently active to convey a background level of firing, such as the 1a sensory neuron in muscle spindles.
True
This receptor adapts rapidly to a stimulus by communicating it, then the response diminishes quickly and often stops. It will fire again to signal significant changes in speed/intensity of the stimulus and often fires again when the stimulus stops (e.g. tissue indentation, vibration).
Phasic Receptor
T/F - Tonic receptors allow the body to ignore constant unimportant information.
False - PHASIC receptors allow the body to ignore constant unimportant information.
T/F - Most exteroreceptors are phasic.
True
A term referring to how sensitive a receptor is to it’s adequate stimulus.
Firing Thershold
These sensitive receptors are immediately activated by their adequate stimulus. They are generally sensing innocuous, everyday types of stimuli and convey all kinds of afferent information that represent routine sensory functions.
Low Threshold Receptors
These receptors have a higher activation threshold and are used to detect harm or potential for harm in their tissues. They are sensitive to a variety of chemicals and to extremes of temperature and mechanical stress.
High Threshold Receptors
The size or ________ of first order neuron axons and whether or not they are __________ determines the speed at which they conduct their information to the spinal cord.
Diameter
Myelinated
Match the following fibre types with the corresponding axon size.
1) A-Delta Fibres
2) C-Fibres
3) A-Beta Fibres
A) Smallest size axon
B) Medium size axon
C) Largest size axon
1) A-Delta Fibres = B) Medium size axon
2) C-Fibres = A) Smallest size axon
3) A-Beta Fibres = C) Largest size axon
Match the following fibre types with the corresponding level of myelination.
1) A-Delta Fibres
2) C-Fibres
3) A-Beta Fibres
A) Heavily myelinated
B) Lightly myelinated
C) Unmyelinated
1) A-Delta Fibres = B) Lightly myelinated
2) C-Fibres = C) Unmyelinated
3) A-Beta Fibres = A) Heavily myelinated
T/F - The smaller the diameter and the more heavily myelinated an axon, the faster it conducts.
False - The LARGER the diameter and the more heavily myelinated an axon, the faster it conducts.
______________ are the largest, most thickly myelinated first order neurons, followed by cutaneous A-Beta fibres, which are majority of the tactile/touch ______________ neurons.
Proprioceptors
Discrimination
A-Delta fibres are mostly ___________, but some are cold-sensing neurons and others communicate ____ movements.
Nociceptors
Hair
C-Fibres are either nociceptors or conveyors of the type of _____ best described as diffuse, gentle and pleasant.
Touch
T/F - The more a first order neuron’s information is needed for functional reflex responses and/or fine motor control, the faster it will conduct back to the CNS.
True
First order afferent neurons synapse with ______ order neurons in the spinal cord, and these neurons are responsible for conveying the data into the brain, mostly to the ________.
Second
Thalamus
______ order neurons are organized into ______, in which neurons of the same sensation types travel together.
Second
Tracts
A much larger number of _____ order neurons converges on a much smaller number of ______ order neurons in the spinal cord. This means that the incoming signals are ____________/summarized before they travel to the brain.
First
Second
Consolidated
Each sensory situation results in the ______ of a cluster of first order neurons that communicates a specific “_______,” based on a number of factors (e.g. proportion of slow/fast adaptors, mix of thresholds & transmission speeds).
Firing
“Picture”
The process in which second order neurons carry afferent information contralaterally where it is interpreted in the somatosensory cortex areas on the opposite side of the brain.
Decussation
Most afferent information enters the spinal cord and travels up it _____________, meeting its second order neurons in the medulla oblongata in the _________. They then _________ and carry it to the contralateral third order neurons in the thalamus.
Ipsilaterally
Brainstem
Decussate
Data about nociception, temperature and _____ touch meets it second order neurons right away upon entering the ______ ____, and they immediately cross and transmit up the _____________ side.
Crude
Spinal Cord
Contralateral
As information enters the ______ horn, it is organized into modality-specific tracts and is also subdivided within them into the ____ areas from which it is coming.
Dorsal
Body
T/F - The dorsal horn itself is divided into four layers, which are referred to as laminae.
False - The dorsal horn itself is divided into SIX layers, which are referred to as laminae.
Incoming first order neurons enter in different _______ based on their type and most of these layers also contain ____________ that have the capacity to boost or inhibit second order neuron transmission.
Laminae
Interneurons
The ____________ are situated between incoming first order neurons and the cell bodies of the second order neurons, ready to carry data to the brain.
Interneurons
T/F - All second order neuron transmission heads to the brain to undergo analysis and response processes.
False - NOT all second order neuron transmission heads to the brain to undergo analysis and response processes.
Some afferent information goes directly to the cerebellum in the _______________ tracts, and this data is never experienced as sensation.
Spinocerebellar
The central receiving area is the ________ and its involvement/relationship with the _____________ cortex along with other brain association areas is crucial to sensory perception.
Thalamus
Somatosensory
T/F - Third order neurons are the thalamus’ communication channels.
True
