PNS day 2

Upcoming test on Monday covering Chapter 14 and Chapter 15 (Peripheral Nervous System).
Withdrawal date is the 31st; advised to consider options carefully.

Suggest to remain enrolled even if failing to gain experience before retaking.
Lab performance nearly counts for 50% of final grade; don’t give up if lab scores are better.

PNS divided into sensory and motor components.
Sensory neurons bring information into the CNS from receptors, with specificity in stimulation.

Three classification by location:
- Exteroceptors: external environment, mainly in skin.
- Interoceptors: internal environment sensors, e.g., in blood vessels.
- Proprioceptors: located in joints, muscles, and tendons.
Classifications by function:
- Nociceptors (pain receptors): respond to harmful stimuli like temperature extremes, mechanical damage, and chemicals.
- Thermal receptors: Four types (cold, cool, warm, hot) related to temperature perception.
- Mechanoreceptors: respond to physical disturbances (tactile, pressure).

Fast pain (immediate response, usually associated with sharp pain) travels via myelinated axons.
Slow pain (less immediate, dull, achy sensation) travels via unmyelinated axons.

Tactile receptors: sensitive to touch, pressure, vibration.
- Fine touch and crude touch/pressure distinctions made based on sensitivity and localization ability.
Proprioceptors: muscle spindle and Golgi tendon organs monitor stretch and position.

Sensory information travels via three neurons:
- First order: sensory neuron transmitting info to the spinal cord.
- Second order: carries info to the thalamus.
- Third order: transmits info to the cerebral cortex.
Sensation perception happens in the cerebral cortex, acting as the integration point.