Central Nervous System (CNS) and Peripheral Nervous System (PNS): Structures and Functions

Central nervous system (CNS) Main structures Protective structures Functioning structures Connection structures
The brain (<-> cranial nerves), spinal cord ( <-> spinal nerves) Blood-brain barrier: prevents poisonous substances from entering into the brain; Skull: shield the brain from external; pia mater, dura mater: protect the brain from within Cortex: gray, wrinkled, with higher surface area – cognitive processes (thinking, remembering); structure under the cortex – emotion, memory, etc. The spinal cord: links the CNS to the PNS; sends and transmits messages; Afferent/sensory nerves: carry information from the receptors -> the spinal cord, brain; efferent/motor nerves: carry information from the CNS -> other body structures
Peripheral nervous system (PNS) Divisions Subdivisions/


Functions Connection
Somatic nervous system (SNS) Receptors, tracts in the skin, muscles, joints Transmit information for voluntary movements/reflexes  
Autonomic nervous system (ANS) Involuntary muscles, cardiac muscles, glands Self-regulation: the respiratory, circulatory, and digestive, etc.  
Sympathetic system (from preganglionic nerves – postganglionic nerves) “crisis management”: reactions to dangers -> send signals to organs/glands -> the heart beating faster, pupils dilate, faster respiration ->

dilates pupil; stimulates weak salivation; relaxes bronchi; accelerates heartbeat; inhibits activity, relaxes bladder

Sympathetic system turned on -> inhibits parasympathetic system
Parasympathetic system Transmit information for promoting digestion, rest, and restorative functions:

Contracts pupil; stimulates strong salivation; constricts bronchi; slows heartbeat; stimulates activity; contracts bladder; stimulates sex organs

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