7. The Peripheral Nervous System (PNS)
- 12 pairs of cranial nerves (connect brain to the head) and 31 pairs of spinal nerves (connect spinal cord to the body).
- Divided into the somatic (voluntary) nervous system and the autonomic (involuntary) nervous system.
- The autonomic system has sympathetic (fight-or-flight) and parasympathetic (rest-and-digest) divisions, plus the enteric system controlling the gut.
|
Parasympathetic (rest & digest) |
Sympathetic (fight & flight) |
|
Constricts pupil |
Dilates pupil |
|
Slows heartbeat |
Increases heartbeat |
|
Stores sugar in liver |
Releases sugar from liver |
|
Accelerates peristalsis |
Slows peristalsis |
|
Constricts bronchi |
Dilates bronchi |
|
Neurotransmitter: acetylcholine |
Neurotransmitter: noradrenaline |