Sensory Pathways & The Somatic Nervous System

Flashcards based on lecture notes about sensory pathways and the somatic nervous system.

Receptor Field

Area monitored by a specific receptor. Larger the field, the less fine tuned the sensation

Sensation

Awareness of stimuli, the information that is arriving from the sensory receptors.

Perception

Interpretation of meaning of stimulus, conscious awareness.

Adaptation

Reduction in sensitivity in the presence of constant stimuli.

Peripheral Adaptation

Sensory receptors subjected to an unchanging stimulus become less responsive over time.

Central Adaptation

Conscious awareness of a stimulus disappears; restricts information reaching the CNS.

Tonic Receptors

Always active; increase or decrease in stimulus changes rate of action potential generation; slow adapting; nociceptors.

Phasic Receptors

Normally inactive, but become active when changes in condition occur; fast adapting receptors; thermoreceptors.

Mechanoreceptors

Generate nerve impulses when deformed by touch, pressure, vibration, or stretch.

Baroreceptors

Detect pressure changes in wall of blood vessels & structures of urinary, reproductive, & digestive tracts.

Proprioceptors

Monitor body position, no adaptation.

Thermoreceptors

Sense changes in temperature, 3-4X more cold than hot, phasic.

Chemoreceptors

Sense changes in chemical concentration dissolved in fluid.

Nociceptors

Cause the sensation of pain, tonic.

Exteroceptors

Receive stimuli from outside the body, most found near the body surface.

Interoceptors

Respond to stimuli from inside the body, viscera and blood vessels.

First Order Neuron

Carries impulse to the CNS; cell body in dorsal root ganglion or cranial nerve ganglion.

Second Order Neuron

Located in spinal cord or brain stem; interneuron which synapses with a first order neuron; decussation occurs here.

Third Order Neuron

Located in the thalamus; synapses with a 2nd order neuron.

Spinocerebellar Tract

Begin in spinal cord and end in the cerebellum.

Spinocerebellar Pathway

Muscle tone & posture; info arrives at the cerebellar cortex, not conscious awareness.

Lateral Spinothalamic Tract

Pain & temperature.

Anterior Spinothalamic Tract

Crude touch & pressure.

Posterior Column Pathway or Dorsal White Column

Fine touch, pressure, two-point discrimination, body position; info comes from skin, muscles, tendons, and joints.

Somatic Motor System

controls skeletal muscles (SNS).

Upper Motor Neuron

Cell body located in the CNS.

Lower Motor Neuron

Cell body in nucleus, of brain stem or spinal cord.

Corticobulbar Tracts

Synapse with lower motor neurons in cranial nerves III- VII, IX, XI, XII, conscious control over skeletal muscles of eye, jaw, face, neck, and pharynx.

Corticospinal Tracts

Synapse on lower motor neurons in anterior gray matter horns of spinal cord.

Medial Pathways

Control of gross movements of trunk and proximal limbs to maintain balance and posture.

Lateral Pathways

Control of upper distal limb muscles.

Motor and Sensory Homunculus

Graphical representation of motor or sensory areas of the brain.

Basal Nuclei

Deep in the white matter of cerebrum are subcortical nuclei.