exam deck 8 Flashcards
What do ascending sensory pathways do?
They transmit sensory information from the skin, joints, muscles, and viscera to the brain for processing.
What sensory inputs do the specific ascending pathways convey?
Tactile discrimination, vibratory sense, and position sense.
Describe the path of 1st order neurons in specific ascending pathways.
They receive input from receptors, travel ipsilaterally in the spinal cord to the medulla oblongata, and synapse with 2nd order neurons.
What do 2nd order neurons do in specific ascending pathways?
Their axons cross to the contralateral side of the spinal cord and project to the thalamus.
What is the role of 3rd order neurons?
They relay sensory signals from the thalamus to the primary somatosensory cortex for integration.
How do non-specific ascending pathways differ from specific ones?
They lose modality specificity and primarily serve alerting and arousal functions.
How is sensory information represented in the somatosensory cortex?
Input from one side of the body projects to the opposite cortex, with areas proportional to sensory discrimination.
What role does the thalamus play in sensory pathways?
It acts as a relay center for sensory input before signals are sent to the cortex.
What determines spatial discrimination of sensory input?
The size of receptive fields and overlap between adjacent fields.
What is referred pain?
Pain perceived at a location other than the stimulus origin, due to shared pathways in the somatosensory system.
How is the somatosensory cortex organized?
It is topographically organized, with larger areas devoted to parts of the body with higher sensitivity.
What are modality-specific receptors, and what do they do?
These receptors respond to specific stimuli and have discrete receptive fields that contribute to spatial discrimination.
How does the thalamus contribute to sensory pathways?
It integrates sensory input from different modalities and relays it to the somatosensory cortex.
How was knowledge about sensory pathways derived?
From cortical stimulation in conscious subjects, revealing the topographical representation of sensory inputs.
What is the primary function of non-specific ascending pathways?
To contribute to arousal and alerting responses by integrating mixed modalities.
How do hair cell afferents respond to bending?
The discharge rate changes depending on the direction in which the hair bundles are bent.
What happens to endolymph during head rotation?
Endolymph displacement bends hair cells in the semicircular canals.
How does head rotation affect firing frequencies in the semicircular canals?
Rotation increases firing on one side and decreases it on the opposite side.
What do otolith organs detect?
They detect linear acceleration and gravitational forces.
How do otolith organ hair cells respond to gravity?
They respond to shifts caused by gravity or head tilts, indicating orientation.
What is the role of CNS vestibular pathways?
To process signals for balance, spatial orientation, and postural control.
What do blue, pink, and green circles represent in taste receptor distribution?
Blue: Common AAs in receptor families. Pink: Variable AAs. Green: AAs in ‘taster’ mice.
What type of receptors do bitter and sweet ligands use?
G-protein-coupled receptors.
How do bitter ligands transduce signals?
By activating transducin, which releases Ca²⁺ from intracellular stores.
How do sweet ligands transduce signals?
By activating gustducin, using a cAMP pathway to close K⁺ channels and depolarize the cell.
How do sour and salt ligands transduce signals?
They alter ion channels, causing depolarization and triggering extracellular Ca²⁺ entry.
What triggers neurotransmitter release in taste transduction?
Increased intracellular Ca²⁺.
What is gustatory processing?
The sensory processing of input from taste receptors to produce taste perception.
What stimuli do T1R receptors detect?
T1Rs sense sweet stimuli.
What stimuli do T2R receptors detect?
T2Rs sense bitter stimuli.
What is the candidate receptor for umami taste, and what does it detect?
The t-mGluR4 receptor is the candidate umami receptor and detects glutamate.
Which receptors are implicated in sodium salt and acid sensation?
MDEG/ENaC receptors, part of a superfamily of ion channels.
