Chapter 13- The peripheral nervous system Flashcards
PNS general function
The PNS links the brain to the outside world as well as the body’s internal environment- includes all nerves that leave/enter the spinal cord. Without the PNS, the brain would have no real function.
How do sensory deprivation tanks work?
Sensory deprivation tank gets rid of all sensory input- the brain will start making stuff up to have something to do- causes massive hallucinations. If you’re nervous beforehand, the hallucinations can be bad/scary.
What are the general structures of peripheral nervous tissue? (3)
- Sensory receptors
- Afferent fibers
- Efferent fibers
Function of sensory receptors
respond to changes in the environment (stimuli)
How are sensory receptors classified? (3)
- Stimulus type- what change in the environment activates the receptor
- Location- either location in the body, or where the location of the source of the stimulus (inside or outside the body)
- Receptor structure- non encapsulated vs encapsulated
Receptor classifications by stimulus type (5)
- Mechanoreceptors
- Thermoreceptors
- Photoreceptors
- Chemoreceptors
- Nociceptors
Mechanoreceptors
Receptors that respond to mechanical force.
Ex- touch, vibration, stretch
Thermoreceptors
Receptors that respond to temperature changes
Photoreceptors
Receptors that respond to light
Chemoreceptors
Respond to chemicals in solution (will only respond if they’re in solution). Ex- smell, taste, changes in blood composition
Nociceptors
Respond to damaging stimuli- activation of this receptor usually results in painful sensation. Ex- extreme temperatures, excessive pressure/stretch
Receptor classifications by location (3)
- Exteroceptor
- Interoceptor
- Proprioceptors
Exteroreceptor
Mostly found at or near the body surface. Receptor is sensitive to stimuli that arise outside the body. Ex- vision, hearing, smell, taste, touch, pressure, pain, etc.
Interoceptor
Receptors that are found deeper in the body-responds to stimuli that arise deep in the body. Ex- chemical change, tissue stretch, internal temperature
Proprioceptors
Found in skeletal muscle, tendon, joints, ligaments. Receptor responds to changes in body movement/position. These receptors are technically interoceptors but are much more limited in their location.
Nerve endings
Dendritic endings of sensory neurons that compose the simple receptors of the general senses. Nerve endings can be non encapsulated or encapsulated.
Encapsulated nerve endings
Tissue covering wrapped around the nerve endings.
Non encapsulated (free) nerve endings
Exposed nerve endings- no tissue covering. They are essentially the peripheral end of a sensory axon.
Where are free (non encapsulated) nerve endings typically found?
Mostly abundant in epithelia and connective tissue
Non encapsulated nerve endings function
Respond mostly to pain (nociceptors) and temperature (thermoreceptors). Heat or cold outside the “range” of a thermoreceptor activates nociceptors. Extreme pressure (ex- pinching the arm) and chemicals are released from damaged tissue to activate nociceptors .
Which sensations are allowed by free nerve endings? (5)
- Temperature
- Pain
- Itch
- Light pressure
- Light touch
What causes the itch sensation?
Detected by a chemoreceptor. Histamine release activates free nerve endings
What causes the light pressure sensation?
Detected by a mechanoreceptor. Merkel cells in the integument are responsible for light touch, pressure, and vibration
What causes the light pressure sensation specifically for hair?
Detected by a mechanoreceptor. Free nerve endings wrap around the hair follicle and respond to change in position