Central Nervous System 2 Flashcards
Detections of Stimuli: Receptors
- detects a stimulus and converts to an action potential which travels to the CNS via sensory neurons (receptor has to be activated to threshold (-55 - 60 mV)
- each stimulus has a specific receptor
- a stimulus can be one of many forms
- MODALITY eg. light, touch and sound are all modalities
Dectection of Stimuli: General Senses
Sensory receptors are located throughout the body
- touch
- pressure
- temperature
- pain
- awareness of body position (proprioception)
Information is projected to the somatosensory cortex
Detection of Stimuli: Special Senses
- receptors are complex
- located in sense organs
- sight
- smell
- taste
- balance
- hearing
- information projected to specific areas of cortex
Detection of Stimuli: General Sensory Receptors
Nociceptor -pain (also itches) Thermoreceptor -temperature (cold or heat) Mechanoreceptor -Tactile receptors: touch, pressure, vibration -Baroreceptors: organ pressure (located within vessels, detect blood pressure) -Proprioceptors: position of joints Chemoreceptors -chemical concentration (pH in blood)
Detection of Simuli: Receptive Field
- detection of a stimulus within a specific area surrounding a receptor
- large receptor fields are less precise than small ones
e. g. back vs finger tip - two point discrimination is clinically relevant
Detection of Stimuli: Labelled Line
- detected information follows a specific neuronal pathway to the cortical region of the brain
- used in neurosurgery and explains why many amputees still experience pain
Detection of Stimuli: Adaptation
Changes in sensitivity in the presence of a stimulus
-Tonic Receptors eg. proprioceptors
adapt slowly
-Phasic Receptors
rapidly adapting
eg. put watch on and forget that it’s there
Somatosensory Pathways
Conscious Somatic Sensations
- touch
- proprioception
- temperature
- nociception
- pain
- itch
Discrete pathway between stimulus and final brain region
Somatosensory Pathways: Sensory/Afferent Division
Sensory information form the skin, head, neck limbs and muscles of the body wall
Posterior Column Pathway: -fasciculus gracilis -fasciculus cuneatus Spinocerebellar Tracts: -posterior spinocerebellar tract -anterior spinocerebellar tract Spinothalamic Tracts: -lateral spinothalamic tract -anterior spinothalamic tract
Somatosensory Pathways: Spinothalamic Pathway
- from spine to thalamus
- responsible for crude feelings, can’t exactly locate where the sense it
Crude touch and pressure sensations, first order neuron, second order neuron, anterior spinothalamic tract, midbrain, third order neuron, thalamus
Pain and temperature sensations, first order neuron, second order neuron, lateral spinothalamic tract, midbrain, third order neuron, thalamus
Somatosensory Pathways: Column Pathway
Fine touch, vibration, pressure and proprioception sensations, first order neuron, fasciculus gracilis and cineatus, in nucleus gracilis and cuneatus synapses to second order neuron, medulla oblongata, medial lemniscus, midbrain, synapse to third order neuron in ventral nuclei in thalamus
Somatosensory Pathways: Spinocerebellar Pathway
Proprioceptive input from golgi tendon organs, muscle spindles, and joint capsules , first order neuron, synapses to second order neuron in grey matter, up anterior spinocerebellar tract to cerebellum (can also go up posterior spinocerebellar tract)
Visceral Sensory Pathways
- Sensory information from internal viscera
- Blood pressure and carbon dioxide concentration
- Never reaches level of conscious awareness
Sensory Information Processing: Primary Sensory Areas vs Somatic Sensory Association Areas
Primary sensory areas
-most direct connection with peripheral sensory receptors
Somatic sensory association areas
-integrate sensory information to generate meaningful patterns of recognition and awareness
Motor Information Processing: Primary Motor Area vs Somatic Motor Association Area
Primary motor area: -control of specific skeletal muscles Somatic motor association area: -communicates with other motor areas -coordinates movement of several muscle groups -controls learned skilled movements -stores movement programs
