The Nervous System
Key Notes & Overview
Two Main Divisions
• Central Nervous System (CNS): brain + spinal cord
• Peripheral Nervous System (PNS): nerves connecting the CNS to the rest of the body
PNS Subdivisions
• Somatic: voluntary control — skeletal muscles, senses
• Autonomic: involuntary control — organs, glands
◦ Sympathetic: “fight or flight” — increases heart rate, releases adrenaline
◦ Parasympathetic: “rest and digest” — slows heart rate, aids digestion
The Neuron (Basic Unit)
Part Function
Dendrites Receive signals
Cell body (soma) Contains nucleus; processes signals
Axon Transmits signal away from the cell body
Myelin sheath Insulates the axon; speeds up conduction
Synapse Junction where the signal passes to the next neuron via neurotransmitters
Signal Transmission
• Resting potential (~ –70 mV) — neuron at rest
• Stimulus triggers depolarization — action potential fires
• Signal travels down the axon
• Neurotransmitters are released at the synapse and bind to the next neuron’s receptors
Key Brain Regions
Region Role
Cerebrum Thinking, voluntary movement, sensory processing
Cerebellum Balance, coordination
Brainstem Vital functions (breathing, heart rate)
Hypothalamus Homeostasis, hormone regulation
Amygdala Emotion, fear response
Hippocampus Memory formation
Key Notes & Overview
Two Main Divisions
• Central Nervous System (CNS): brain + spinal cord
• Peripheral Nervous System (PNS): nerves connecting the CNS to the rest of the body
PNS Subdivisions
• Somatic: voluntary control — skeletal muscles, senses
• Autonomic: involuntary control — organs, glands
◦ Sympathetic: “fight or flight” — increases heart rate, releases adrenaline
◦ Parasympathetic: “rest and digest” — slows heart rate, aids digestion
The Neuron (Basic Unit)
Part Function
Dendrites Receive signals
Cell body (soma) Contains nucleus; processes signals
Axon Transmits signal away from the cell body
Myelin sheath Insulates the axon; speeds up conduction
Synapse Junction where the signal passes to the next neuron via neurotransmitters
Signal Transmission
• Resting potential (~ –70 mV) — neuron at rest
• Stimulus triggers depolarization — action potential fires
• Signal travels down the axon
• Neurotransmitters are released at the synapse and bind to the next neuron’s receptors
Key Brain Regions
Region Role
Cerebrum Thinking, voluntary movement, sensory processing
Cerebellum Balance, coordination
Brainstem Vital functions (breathing, heart rate)
Hypothalamus Homeostasis, hormone regulation
Amygdala Emotion, fear response
Hippocampus Memory formation
