Sensory (ascending) pathways Flashcards
(18 cards)
What are the two main types of receptors classified in sensory input systems?
Encapsulated and unencapsulated
Receptors can be classified based on their structure and function.
What do exteroreceptors sense?
External environment stimuli such as touch, pain, thermal, vision, audition, olfaction, gustation
Exteroreceptors are specialized for sensing external stimuli.
What do interoreceptors sense?
Internal conditions such as visceral sensations, stretch, pH, CO2
Interoreceptors monitor internal body states.
What are proprioreceptors responsible for sensing?
Spatial orientation, located in head, body, and vestibular apparatus
Proprioreceptors include tactile/pressure receptors, joints, muscle spindles, golgi tendon organs, and ear hair cells.
What is the role of General Somatic Afferent (GSA) pathways?
Convey sensory information from body and limbs to higher centres of CNS
GSA pathways are crucial for conscious perception of sensation.
Where is sensory information perceived in the brain?
Somatosensory cortex in the cranial part of the parietal cortex
The cruciate sulcus serves as a useful landmark in the somatosensory cortex.
What does the mapping of the somatosensory cortex represent?
A ‘map’ of the body surface formed by connections in the parietal lobe
This mapping shows disproportionate somatotrophic representation.
What is a homunculus?
A representation of the body’s surface map in the brain
Homunculi vary across species, reflecting lifestyle and adaptations important for survival.
What is the dorsal columns pathway responsible for?
Touch and kinaesthesia via a 3-neuron relay
This pathway includes synapses with second and third order neurons.
What does the spinothalamic tract convey?
Pinprick pain and temperature sensations
This pathway is characterized by a diffuse bilaterally symmetric pathway.
How many neurons are in the spinocervicothalamic tract relay?
Minimum 4 neurons
This tract is prominent in carnivores and includes specific synapses at the cervical nucleus.
What is the medial lemniscal system composed of?
Heavily myelinated axons from gracile-cuneate and spinothalamic tracts
The medial lemniscal system is involved in the contralateral relay of sensory information.
Which sensory modalities do spinoreticular tracts encompass?
All sensory modalities except muscle/joint proprioception
This pathway uses a diffuse bilaterally symmetric pathway and is non-specific to the cortex.
What is the function of the spinocerebellar tract?
Subconscious proprioception for fine-tuning motor coordination
This tract is well-developed in domestic species.
What is the significance of understanding sensory pathways in a neurological exam?
Aids in lesion localisation
Knowledge of anatomy and physiology enhances understanding of observed symptoms.
Define pain in terms of sensory perception.
Conscious perception of noxious stimulus plus unpleasant emotional response
Pain can activate reflexes and be transmitted to the brain via sensory pathways.
What is hyperalgesia?
Increased sensitivity of nociceptors due to tissue-released chemicals
This condition can cause light touch to induce a pain response.
How is visceral pain characterized?
Poor localisation and can be referred to somatic areas served by the same spinal nerve
Visceral pain can also lead to extreme sensations like distension and induce muscle spasms.
