Anatomy Intro

* Central nervous system (CNS) – brain and spinal cord

* Peripheral nervous system (PNS) – everything else

* Afferent neurons – neurons delivering signals to the CNS from the periphery

* Situated in the dorsal region of the spinal cord

* Called the afferent gray or sensory gray

* Sensory neurons – a subset of afferent neurons which transmit signals that we are aware of

* i.e. sense of pain

* Efferent neurons – neurons sending signals to the periphery from the CNS

* Situated in the ventral region of the spinal cord

* Called the efferent gray or motor gray region

* Motor neurons – a subset of efferent neurons which go to muscles and glands

* Somatic structures – skin, fascia, striated muscle, bone

* Signals from here are part of the somatic afferent system

* We are aware of these signals

* Signals to here are part of the somatic motor system

* i.e. signals to striated muscle

* Visceral structures – glands, smooth muscle, cardiac muscle

* Signals from here are part of the visceral afferent system

* We are not aware of these signals

* Signals to here are part of the visceral motor system, also called the autonomic system

* i.e. glands, smooth muscle, cardiac muscle

* Three qualities of sensation:

* Quality

* Visceral = always uncomfortable or painful

* i.e. your heart never feels “good”

* Somatic = can be painful or pleasant

* Localizability

* Visceral = poorly localized

* i.e. a broad area of your “chest” hurts

* Somatic = clearly localized

* Stimuli that elicit pain

* All of the following are somatic pain, and pains that are also visceral are italicized:

* Cutting

* Temperature extremes

* Crushing

* Stretching

* Cramping

* Inflammation...