Lecture 24- The Peripheral Nervous Sytem Flashcards
What is the PNS?
Peripheral nervous system
All neural structures outside the brain and spinal cord
Sensory receptors
Peripheral nerves
Efferent motor endings
Sensory receptors
Specialized receptors that respond to changes in environment called stimuli
Non encapsulated dendritic endings
Free nerve endings that detect temp., pain, itch, light touch or are located at base of hair follicles.
Encapsulated dendritic endings
Consist of dendrite enclosed in a connective tissue capsule and detect discriminatory touch,initial, continuous and deep pressure and stretch of muscle , tendons and joint. Capsules
What can graded receptor potentials trigger?
Action potentials that travel along the axon to the CNS
Mechanoreceptors
Stimulated by mechanical force, such as touch,pressure, vibration and stretch
Thermoreceptors
Detect changes in temperature
Photoreceptors
Detect light
Generally in the eyes
Chemoreceptors
Stimulated by chemicals such as odours,tastes or chemical components of body fluids
Nolcireceptors
Respond to painful stimuli
Where exteroceptors located?
Near the body surface
And detect stimuli from outside body- touch, pressure, pain
Where are interceptors located?
Associated with internal organs and vessels
Monitor chemical changes, stretch or temperature
Where are proprioreceptors located?
Within skeletal muscles, joints and associated connective tissues
Relay information about body movements
Sensation
Awareness of changes in internal and external environment
Perception
The conscious interpretation of sensation stimuli
First order sensory neurons
Carry impulses from receptors
Second order neurons
Transmit to the cerebellum
Third order neurons
Carry impulses to postfrontal gyrus
Perception of Pain
Protects body from damage
Stimulate by extremes of pressure and temperature as well as chemicals releases from damaged tissues
Pain threshold
Stimulus intensity at which we begin to perceive pain
Same for most people
Pain tolerance
Genetically determined trait with learned aspects that varies from person to person
Perceived pain can be affected by environment
Visceral pain
Results from stimulation of receptors within internL organs from stimuli such as extreme stretch, ischemia, chemical irritation and muscle spasms
What does visceral pain travel along?
The same fibre tracts as somatic pain impulses, giving rise to reffered pain
Reffered pain
Pain that feels as though it is located in an area different from the affected body region
