CNS Flashcards
What do These cause
Threshold stimulus
Subnthreshold stimulus
Supra threshold stimulus
Action potential
Local potential
Increased frequency of action potential
What is adequate stimulus
It is the stimulus to which receptor is most sensitive or to which receptor responds at low energy levels
What is a receptor
A biological transducer (converts one form of energy into another form of energy
What do receptors code for (4)
- site/location
- modality
- intensity
- duration
What is adaptation
Stimulus is present but response of receptor decreased over time
Rapidly adapting receptor features
Phasic
Encapsulated nerve
Can detect rate of change of stimulus
Slowly adapting receptor features
Tonic
Expanded of brain nerve endings
Can detect a steady stimulus
Types of phasic receptors
Pacinian corpuscles
Meissners corpuscles
Hair end organs
Tonic receptors
Merkel’s disc Ruffini’s endings C-mechanoreceptors Receptors for position sense-joint capsule,muscle spindle,golfi tendon organs Thermoreceptors
Cold thermoreceptor fibre
Adelta and C
Cold thermoreceptors detect range of temperature
40 degree Celsius to 10 degree Celsius
Below 10 degree no activation of thermoreceptors
Activation of nociceptors
Cold thermoreceptors detect range of temperature
Can detect temperature up to 45 degree Celsius
After 45 degree stimulation of nociceptors
Types of nociceptors
Mechanical
Chemical
Thermal
Polymodal
Ascending sensory tracts
Posterior column
Spinothalamic tract
Spinocerebellar tract
Posterior column sensation
Conscious proprioception Fine touch localisation Two point discrimination Vibration Stereognosis Ability to judge different degrees of pressure
Spinothalamic tract sensation
Lateral – pain, temperature
Anterior – crude touch, itching, tickle, sexual sensation, detection of pressure
Spinocerebellar tract sensation
Unconscious proprioception
Tracts from lower limb and upper limb in spinocerebellar
Lower limb-
Dorsal/posterior/ fleschig’s (m. Spindle,GTO) uncrossed
Ventral/anterior/gower’s tract(GTO) crossed
Upper limb
Cuneocerebellar
Rostral spinocerebellar
(Similar to above)
Posterior column diagram
See it
Sensory homunculus sensitive areas
More sensitive areas have larger cortical representation
Eg face lips hand fingers
Spinothalamic tract diagram
See it
Spinal tumours type and sensation loss
Medullary and extra-medullary
Descending sensory loss and ascending sensory loss resp
Fast pain fibres and their stimulus
Adelta
Mechanical/thermal
Neurotransmitter of fast pain
Glutamate