general senses, exam #$

General senses:

• Sensory receptors not concentrated in special organs

• Include detection of, temp, pain, touch, pressure. Vibration, proprioception

Perecption:

The conscious awareness of a sensation

Sensation:

The Arriving information

Receptive field:

•  when strong stimulus arrives in the receptive field , the CNS receives the info 

• The larger the receptor field, the poorer your ability to localize a stimulus

Adaption:

• Reduction in sensitivity in the presence of a constant stimulus, ex: steppeing into a hot bath or jumping into a cold lake 

Classifying sensory receptors: NOCICEPTORS

• Common in:

  • Superficial portions of the skin

  • Joint capsules

  • Bone periosteum

  • Walls of blood vessels

• May be senstive many stimuli:

  • Temp extremes

  • Mechanical damage

  • Dissolved chemicals (injured cells)

• Free nerve endings with large receptive fields 

Classifying sensory receptors: THERMORECEPTORS (temperature receptors)

• Free nerve endings located in:

  • Dermis 

  • Skeletal muscles liver 

  • Hypothalamus 

• Temperature sensations conducted along the same pathways as pain sensations

Classifying sensory receptors: CHEMORECPTORS 

• Detect chemicals in the body

• Respond to only dissolved

  • Water soluble substances

  • Lipid soluble substances

• Unconscious viceral receptors

• Adapt quickly (period of seconds)

  • A change happens, they send a signal, adapts to change quickly

Classifying sensory receptors: MECHANORECPTORS

• Sensitive to stimuli that distort their plasma membranes

• Contain mechanically gated ion channels

  • Gates open or close in response to, stretching, compression, twisting, and other distortions of the membrane

Three classes of merchanoreceptors:

1. Barocrecptors

2. Prorioceptors

3. Tactile receptors

Mechanoreceptors class: BARORECEPTOR

• Free nerve endings that branch within elastic tissues

• Respond to chain in pressure, adapt rapidly

• Walls of blood vessels, digestive, respiratory, and urinary tracts

Mechanoreceptors class: PROPRIOCEPTORS

• monitor:

  • Position of joints

  • Tension in tendons and ligaments

  • State of muscular contraction 

Mechanoreceptors class: TACTILE RECEPTORS

• Touch sensations (shape or texture)

• Pressure sensations (degree of mechanical distortion)

• Vibration sensations (pulsing or oscillating pressure)

Tactile receptor,  fine touch and pressure receptors:

• Narrow receptive field, precise location of detection and this gives detailed information about the stimulus

Tactile receptor, crude touch and pressure receptors:

• Large receptive fields

  • Poor localization meaning it doesnt tell you a lot, and cant narrow to a specific spot

• Little info about stimulus

Free nerve endings:

• Branching tips of dendrites

• Sensitive to many type of stimuli

• Provide little receptor specificity

Root hair plexus:

Made up of free nerve endings stimulated by hair movement

Tactile discs:

Fine touch and pressure receptors sensitive to shape and texture

Tactile corpuscles:

Gives sensations of fine touch and pressure and lower frequency vibration, abundant in eyelids, fingertips, and external genetalia

Lamellar corpuscles or Pacinian corpuscle:

• Large receptors sensitive to deep pressure and to pulsing or high frequency vibrations

Ruffinis corpuscle:

• Sensitive to pressure and distortion of the deep dermis