General sensory systems

Sensory receptors

• detect information (stimulus) in the internal or external environment

• The part of the CNS that process the information

Neural pathways

• convey information from the receptors to the CNS

• The part of the CNS that processes the information

Sensation

• When sensory information reaches an integration center in the CNS it becomes sensation

• Sensation may be consciously or unconsciously processed

Perception

• conscious interpretation of the sensation (recognition of taste, pain, warmth

Process of sensation

• sensory information needs to be transformed into neural information- action potentials

Stimulation

• sensory information, stimulus, must be presented to a sensory receptor

Transduction

• a sensory receptor converts the stimulus energy into a graded potential

Action potential generation

• if a graded potential is large enough, an AP is generated and carries the info to the CNS

Integration

• as the sensory information is transferred within the CNS it can be modified, left unchanged or deleted

Interoceptors

• respond to internal stimuli(visceral), ANS

Exteroceptors

• respond to external stimuli on the body surface

Proprioceptors

• body position/movement stimuli; occur in muscle, tendons, joints and inner ear

Types of sensory receptors

• sensory receptors are activated by a specific type of stimulus

Thermoreceptor

• heat/cold

Photoreceptor

• Light

Nociceptors

• pain

Chemoreceptors

• chemicals

Mechanoreceptors (baroreceptors)

• physical deformation

Peripheral endings of a sensory(afferent) neuron

• Free endings or encapsulated

Separate cells

• synapse onto a sensory neuron

Receptive field

• the receptive field of a neuron is the stimulus that best activates a neuron

• May be…. Physical area on the body, specific group of chemicals, particular set of sound frequencies

Sensory coding

• all sensory information is transmitted as action potentials which are all alike. How do we distinguish between stimuli?- sensory systems encode four attributes of a stimulus

Modality

• types of stimulus, pain, vision, touch

Labeled lines

• different stimuli have distinct pathways into the CNS and to specific sites within the CNS

Location

• where is the stimulus occurring

Intensity

• how strong is the stimulus

Duration

• how long does the stimulus last

Topographic map

• adjacent areas on the body(retina) project to adjacent areas in the cerebral cortex-homunculus

Receptive field size

• different sensory neurons innervate different sized areas of the body, sometimes overlapping- two point discrimination test

Acuity

• ability to discriminate between two stimuli