CNS: Sensory Review Flashcards
What do afferent (sensory) neurons do?
Afferent neurons carry information from the body’s tissues via receptors about internal and external environments to the central nervous system (CNS).
How many times more afferent neurons are there compared to efferent neurons in the human body?
There are about 20 times more afferent neurons than efferent neurons.
What is the purpose of afferent data in the CNS?
The purpose is to inform the CNS about internal and external events so responses can be properly designed and initiated, ensuring good conscious perception as needed.
What is a reflex?
A reflex is an automatic efferent reaction triggered by incoming sensory information without the need to reach the brain.
What is the neural pathway called that describes a reflex?
The neural pathway is called a reflex arc, consisting of Afferent -> Interneuron -> Efferent.
What happens to afferent information that arrives in the brain processing centers?
It receives more complex analysis, allowing for customized, situation-specific responses that can involve emotional and cognitive aspects.
What is sensory input or afferentation?
Data that is carried as afferent transmission along the neurons of the sensory system into the CNS for interpretation and response.
How do sensation, sensory experience, and sensory perception differ?
• Sensation: The conscious awareness of sensory input.
• Sensory Experience: The subset of afferentation that rises to consciousness and is interpreted.
• Sensory Perception: The individual’s impression or interpretation of sensory input (e.g., olfactory receptors detecting molecules and perceiving them as scent).
What is the difference between nociception and pain perception?
• Nociception: The process of detecting tissue stress/damage and conveying this information to the CNS.
• Pain Perception: Occurs when the brain assigns a sensory experience to the nociceptive data, resulting in the conscious experience of pain.
Does the presence of afferentation from tissues guarantee sensation?
No, the presence of afferentation does not guarantee sensation, as all sensation is assigned by the brain.
How do olfactory receptors contribute to sensory perception?
Olfactory receptors detect ambient molecules and inform the CNS. If this data is selected for experience, the perception of it is referred to as a scent.
What role do nociceptors play in sensory transmission?
Nociceptors detect tissue stress/damage and convey this information to the CNS. At this stage, it is called nociception; it is only referred to as pain or pain perception when the person has a sensory experience of it.
What are the specialized receptors in the somatosensory system responsible for?
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 First Order Neurons.
What are the specialized receptors in the somatosensory system responsible for?
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 First Order Neurons.
What is the function of First Order Neurons in the somatosensory system?
First Order Neurons convey the transmission of stimuli to the spinal cord. Their synapses occur either in the dorsal horn of the spinal cord or farther up in the brainstem, with some arriving at the brainstem via cranial nerves.
Who are the secondary or second order (2°) sensory neurons and what is their role?
Secondary or second order (2°) sensory neurons carry the afferentation from the First Order Neurons to the thalamus.
What is the role of the thalamus in the somatosensory system?
The thalamus acts as a reception/relay station for the brain. Its crucial role in sensation is to convey data, via the tertiary or third order (3°) neurons, to the Somatosensory Cortex and related brain areas for memory, emotion, cognition, and autonomics.
How does the anatomy of the somatosensory system differ from that of special senses and visceral sensation?
While the focus is on somatosensation, there are anatomical differences for the special senses and visceral sensation that will arise when relevant in the study of the somatosensory system.
What is a typical First Order (1°) Neuron attached to?
A typical First Order Neuron is attached to one or more specific type of receptors embedded in tissue.
What determines if an action potential is initiated in a First Order Neuron?
The receptors have stimulus thresholds; if the stimulus is strong enough, an action potential is initiated.
Describe the process of depolarization in First Order Neurons.
The resulting depolarization wave travels along the axon toward the cell body, which is located in the dorsal root ganglion.
What is the peripheral branch/process of a First Order Neuron?
The axon from the receptor to the cell body is called the peripheral branch/process of the neuron. These branches are located in the peripheral nerve and then the spinal nerve that corresponds with their supply tissue.
How does transmission move into the CNS from a First Order Neuron?
From the cell body, the transmission moves quickly into the CNS at the spinal cord’s dorsal horn. The axon that enters the dorsal horn is called the central process of the 1° neuron.
Where is the receptor of each First Order (1°) neuron located?
The receptor is located in the tissue it is responsible for sensing and reporting about, generating information about a specific stimulus type occurring in a discrete location, known as its Receptive Field.
How are the peripheral branches of First Order Neurons organized?
The peripheral branches are bundled together into fascicles, which are then grouped into a peripheral nerve responsible for that tissue zone.
What is meant by a nerve’s “Supply Tissue”?
The identified pattern of sensation responsibility that a nerve has, typically consisting of smaller areas where the nerve exclusively carries afferent neurons and larger zones where it is the primary but not exclusive supplier.
How do peripheral branches of First Order Neurons change upon entering a spinal nerve?
Once their peripheral branches enter a spinal nerve, the same neurons are in a different configuration; many peripheral nerves carry a group of neurons that sense the same tissue zone but do not all report to the same spinal cord segment.
What are examples of peripheral nerves that carry neurons sensing the same tissue zone?
Various plexuses, including cervical, brachial, lumbar, sacral, etc.
What does a spinal nerve contain?
A spinal nerve contains all the neurons whose functions correspond to one spinal cord level.
What is a dermatome?
A spinal nerve’s pattern of skin responsibility.
What is a sclerotome?
A spinal nerve’s sclerotome includes deeper structures such as bone, periosteum, and joints.
What does the term “Ridcular” refer to?
“Ridcular” means “of the root,” referring to the nerve roots from a specific spinal segment.
What does the spinal nerve consist of?
The spinal nerve is the combination of the nerve roots from that spinal segment.
What do the illustrations of peripheral and spinal nerve supply tissue patterns depict?
The illustrations show the dermatomal patterns for the skin of the whole body, including anterior and posterior views.
How many identified sensory modalities are there in humans?
There are at least 17 identified sensory modalities.
What is the term used for senses with receptors distributed throughout various tissue types?
General Sense.
What distinguishes Special Senses from General Senses?
Special Senses have receptors located in one part of the body with dedicated sense organs, often with specific interpretation areas in the brain (e.g., vision, smell, hearing, taste).
How are senses like touch and equilibrium categorized by experts?
They are considered principal sensory categories but do not have distinct receptors; they integrate data from several receptor types.
