Additional Nervous System Terms

Senses

General Senses

• senses with the receptors distributed throughout the body.

• include pain, temperature, pressure, vibration, and proprioception

Special Senses

• have specialized, complex receptors

• include olfaction (smell), gustation (taste), vision, and hearing.

Sensation

created when one is aware of a condition. There are several requirements that must be met to develop a sensation. There must be:
1. stimulus - a change in the environment
2. receptor - some structure in the body that is altered by the stimulus. The altered receptor must generate an action potential.
3. conduction - an impulse must be conducted to the appropriate portion of the brain.
4. translation, interpretation, or perception - conscious awareness of the condition

Sensory Modality- type of sensation. Is it pain, touch, pressure, etc.

Projection

• Projection- brain ability to determine where stimulus is located

  • You know which finger is hurt when you grab a thorn on the stem of a rose.

  • Sometimes this process doesn't work properly.

  • referred pain: A person with clogged heart arteries may sense pain in the left arm or jaw

Sensory Adaptation/accommodation

• some sensations decrease in intensity when stimulus applied after long period of time

• nose blindness

• after image- a sensation may persist after stimulus is removed

• phantom/ghost images- sensations persist after limb amputated

• analgesia- absence of pain

• anesthesia- absence of sensation

Location Receptors

• tonic- always active

  • frequency of action potentials change when receptor stimulated

• phasic receptor- only active when stimulated

• exteroceptor- sensitive to changes that occur outside body

  • touch receptors-

  • teloceptors-change far outside of body

• proprioceptor- sensitive to body postition and motion

  • kinesthetic sense

• interoceptors/visceroceptors- sensations of viscera

  • dont have good projection

  • malaise- “queasy”

Stimulus receptors

• chemical receptors- molecules and ions

  • taste and smell

• mechanical receptors- physically deformed

  • nocireceptors- pain

  • tactile receptors- touch

  • thermoreceptors- temp

  • photoreceptors- retina; light

  • pressoreceptors.baroreceptors- pressure changes; found in walls of blood vessels to monitor blood pressure