ascending tracts Flashcards
- What do sensory nerve fibers in the spinal cord form?
Sensory nerve fibers in the spinal cord form bundles or tracts in the white matter.
- What are the two types of afferent sensory information?
The two types of afferent sensory information are exteroceptive and proprioceptive.
- What is exteroceptive sensory information?
Exteroceptive sensory information originates outside the body (e.g., pain, temperature, touch).
- What is proprioceptive sensory information?
Proprioceptive sensory information originates inside the body (e.g., from muscles and joints).
- How many neurons typically make up a sensory pathway?
A sensory pathway typically involves a three-neuron chain.
- Where is the cell body of the first-order neuron located?
The first-order neuron’s cell body is in the posterior root ganglion.
- Where does the first-order neuron transmit sensory signals?
The first-order neuron transmits sensory signals from receptors to the spinal cord.
- Where does the second-order neuron project?
The second-order neuron’s axon decussates and ascends to the thalamus.
- Where does the third-order neuron project?
The third-order neuron projects from the thalamus to the cerebral cortex.
- What additional structures can sensory pathways connect to?
Sensory pathways can connect to the reticular formation and motor neurons.
- What is the function of the lateral spinothalamic tract?
The lateral spinothalamic tract carries pain and temperature sensation.
- What is the function of the anterior spinothalamic tract?
The anterior spinothalamic tract carries light touch and pressure.
- What are the functions of the posterior white columns?
The posterior white columns carry discriminative touch, vibration, and proprioception.
- What do the spinocerebellar tracts transmit?
The spinocerebellar tracts transmit unconscious proprioception to the cerebellum.
- What is the function of the spinotectal tract?
The spinotectal tract relays sensory information for spinovisual reflexes.
- What is the function of the spinoreticular tract?
The spinoreticular tract sends muscle, joint, and skin input to the reticular formation.
- What does the spino-olivary tract do?
The spino-olivary tract provides indirect afferent input to the cerebellum.
- What type of receptors detect pain and temperature?
Pain and thermal receptors in the skin use free nerve endings.
- What are the two types of fibers carrying pain impulses?
Pain impulses travel through fast-conducting Aδ fibers and slow-conducting C fibers.
- What type of pain do Aδ fibers transmit?
Aδ fibers transmit sharp pain.
- What type of pain do C fibers transmit?
C fibers transmit burning and aching pain.
- Where does pain perception occur?
Pain perception occurs in the thalamus and cerebral cortex.
- What is the first step in the lateral spinothalamic tract pathway?
First-order neurons enter the spinal cord and travel via Lissauer’s tract.
- Where do first-order neurons of the lateral spinothalamic tract synapse?
First-order neurons synapse in the posterior gray column (substantia gelatinosa).
- What happens to second-order neurons in the lateral spinothalamic tract?
Second-order neuron axons decussate within one spinal segment.
- Where do second-order neurons ascend?
Second-order neurons ascend contralaterally in the lateral spinothalamic tract.
- Where are the third-order neurons of the lateral spinothalamic tract located?
Third-order neurons are located in the ventral posterolateral nucleus of the thalamus.
- Where do third-order neurons project?
Third-order neurons project to the somatosensory cortex.
- How is fast pain processed in the CNS?
Fast pain travels directly to the thalamus and sensory cortex for precise localization.
- How is slow pain processed in the CNS?
Slow pain is relayed through multiple neurons and is poorly localized.
- What neurotransmitter is responsible for fast pain transmission?
Glutamate is the fast excitatory neurotransmitter for pain.
- What neurotransmitter is involved in slow pain?
Substance P is slowly released and affects multiple neurons in pain transmission.
- What is the “winding up” phenomenon?
The “winding up” phenomenon is an increased response to persistent noxious stimuli.
- What is the gating theory of pain modulation?
The gating theory states that non-painful stimuli can inhibit pain signals via large myelinated afferents.
- How does excessive tactile stimulation affect pain transmission?
Excessive tactile stimulation “closes the gate,” preventing pain transmission.
- What chemicals help modulate pain in the posterior gray column?
Endorphins and enkephalins help modulate pain in the posterior gray column.
- What are the main functions of the ascending tracts?
The ascending tracts relay sensory information such as pain, temperature, touch, vibration, and proprioception to the brain.
- How does pain perception involve cognitive and emotional factors?
Pain perception is influenced by emotional and cognitive factors, affecting its intensity and response.
- What are the main levels where pain modulation occurs?
Pain modulation occurs at different levels of the nervous system, involving inhibitory mechanisms and neurotransmitters.
- What brainstem areas are involved in the analgesia system?
The periventricular area, periaqueductal gray matter, and midline nuclei of the brainstem.
- How do fibers from the reticulospinal tract influence pain sensation?
They descend to the spinal cord and synapse on pain-related cells in the posterior gray column, suppressing pain sensations.
- What neurotransmitters are involved in the analgesic system?
Enkephalins, endorphins, and serotonin.
- How do enkephalins and endorphins modulate pain?
They inhibit substance P release in the posterior gray column.
- What is the primary function of the anterior spinothalamic tract?
It carries crude touch and pressure sensations.
- Where do first-order neurons of the anterior spinothalamic tract synapse?
In the substantia gelatinosa of the posterior gray column.
- Where do second-order neurons of the anterior spinothalamic tract decussate?
In the anterior gray and white commissures within several spinal segments.
- How are fibers arranged in the anterior spinothalamic tract as they ascend?
Sacral fibers are lateral, and cervical fibers are medial.
- Where do third-order neurons of the anterior spinothalamic tract project?
To the somesthetic cortex in the postcentral gyrus of the cerebral cortex.
- What are the two divisions of the posterior white column?
The fasciculus gracilis (lower body) and fasciculus cuneatus (upper body).
- Where do first-order neurons of the posterior white column terminate?
In the nuclei gracilis and cuneatus of the medulla oblongata.
- What forms the medial lemniscus?
Axons of second-order neurons after decussating as internal arcuate fibers.
- What sensations are carried by the posterior white column?
Fine touch, two-point discrimination, vibration, and proprioception.
- Where do third-order neurons of the posterior white column pathway project?
To the somesthetic cortex via the internal capsule.
- What is the function of the posterior spinocerebellar tract?
It conveys muscle joint sense from the lower limbs and trunk.
- Where does the posterior spinocerebellar tract originate?
From Clarke’s nucleus in the posterior gray column.
- Through which cerebellar peduncle does the posterior spinocerebellar tract enter the cerebellum?
The inferior cerebellar peduncle.
- How does the anterior spinocerebellar tract differ from the posterior spinocerebellar tract?
The anterior tract crosses the midline and ascends contralaterally before re-crossing in the cerebellum.
- Through which cerebellar peduncle does the anterior spinocerebellar tract enter?
The superior cerebellar peduncle.
- What information does the anterior spinocerebellar tract carry?
Muscle joint information from upper and lower limbs, as well as skin sensations.
- What is the function of the cuneocerebellar tract?
It transmits muscle joint sense from the upper limbs.
- Where does the cuneocerebellar tract originate?
In the nucleus cuneatus.
- What is the destination of the cuneocerebellar tract?
The cerebellum via the inferior cerebellar peduncle.
- What is the function of the spinotectal tract?
It is involved in spinovisual reflexes (eye and head movement toward stimuli).
- Where does the spinotectal tract synapse?
In the superior colliculus of the midbrain.
- What is the function of the spinoreticular tract?
It influences levels of consciousness.
- Where does the spinoreticular tract synapse?
In the reticular formation of the medulla, pons, and midbrain.
- What is the function of the spino-olivary tract?
It conveys cutaneous and proprioceptive information to the cerebellum.
- Where does the spino-olivary tract synapse?
In the inferior olivary nuclei of the medulla.
- Where do visceral sensory pathways enter the spinal cord?
Through the posterior roots.
- Where are the first-order neurons of the visceral sensory pathway located?
In the posterior root ganglia.
- Where do second-order neurons of the visceral sensory pathway synapse?
In the posterior or lateral gray columns.
- What tract carries visceral sensory information to the thalamus?
The spinothalamic tract.
- Where is visceral sensory information ultimately processed?
In the postcentral gyrus of the cerebral cortex.
- What is another function of visceral afferent fibers?
Some participate in reflex activity.
