Intergrative Sensory System SEM2 Flashcards
What are the different sensory systems
External environment - vision, hearing, taste, smell
Position and movement - balance
Interoceptors - visceral mechanical, thermal + chemical detection
What are characteristics of bipolar sensory neurones
Cell body in dorsal root ganglia
Peripheral terminals in dermis/epidermis
Central terminals in dorsal horn of spinal cord
What is the types of mechanosensors for touch, vibration, stretch and pressure
Specialised sensory endings - myelinated A β axons for fast conduction of sensory signals
What is the type of mechanosensor for pinches, high pressure and trauma
Bare nerve endings - thinly myelinated for faster transmission of pain
What do pacinian corpuscles detect
Detect vibrations and deep pressure
What is the role of thermal sensors in skin
Distinct sensors for different temperature ranges
Innocuous and noxious ranges covered
How do touch pathways ascend
Ascend in ipsilateral dorsal column
Where are touch pathways relayed at
Relayed at cuneate/gracile nuclei in medulla
Where do touch pathways cross over into
Cross over into the medial lemniscus
Where are touch pathways relayed in following being crossed over into the medial lemniscus
Relayed into thalamus and projected to SI cortex
Where do pain pathways cross over into
Cross over in the spinal cord
Where do pain pathways ascend in
Ascend in contralateral ventrolateral column (spinothalamic tract)
Where are pain pathways relayed in
Relayed in thalamus and projected to SI cortex
What does stretching of a muscle spindle drive
Drives excitatory input to same muscle to contract and inhibits input to opposing muscle
What is the visual pathway
Projection via lateral geniculate nuclei to visual cortex (occipital lobe)
What are V1 cells in visual information processing
V1 cells are retinotopic and binocular and important to initial stages of visual processing
What causes the movement of the basilar membrane
Inside the cochlea sound waves causes the fluid to move which vibrates the basilar membrane and can respond to different frequencies
What is the auditory pathway
Largely crossover in the lower brain stem
Projects to inferior colliculus then medial geniculate nucleus and to auditory cortex A1 (temporal lobe)
What does fluid movement in auditory/sensory transduction cause
Fluid movement induced stretch of link fibres opens K+ channels causing depolarisation
What does the vestibulo-oculomotor reflex do
Maintains direction of gaze during head rotation
What does the righting reflex do
Maintains balance during tilt-induced activity in muscles
What is touch processed through
The dorsal column tract
What is pain processed through
Ventral spinothalamic tract
What does lesions at the forebrain level cause
Contralateral paralysis in the limbs
What does lesions at the spinal cord level cause
Ipsilateral paralysis in the limbs
What are the three regions of the motor cortex
Primary motor
Premotor
Supplementary motor area (SMA)
What does the motor cortex evoke
Evokes muscle contraction directly through the control of lower motor neurones and alters strength of spinal reflexes
What is the premotor area involved in
Involved in postural preparation for movement
What is the supplementary motor area (SMA) involved in
Involved in planning co-ordinated movements
What are properties of the corticospinal tract
Controls voluntary movement
Projects through internal capsule in midbrain
Controls contralateral lower motor neurons in ventral spinal cord
What are the effects of a stroke
Occurs near the internal capsule lesioning one or both corticospinal tracts
Causes impairment of voluntary movement with increased muscle tone - spasticity
What does the pyramidal pathway control
Controls fine/purposeful movement
What tract is used for the pyramidal pathway
Corticospinal tract from motor cortex which descends through the brainstem into the spinal cord
What is the purpose of the extrapyramidal pathway
Achieves refelx adjustments of posture/balance
Modulates muscle tone
Delivers coordinated movement
What is the pathway of the extrapyramidal pathway
Indirect pathway relaying in the brain stem and regulated by feedback loops from basal ganglia and cerebellum
How is the basal ganglia involved in a feedback loop
Forms feedback loop to cerebral cortex to adjust motor output
What is the core region of basal ganglia controlled by
The striatum (core region) is controlled by dopamine (DA) contraning neurons that project from substantia nigra
