The brain and nervous system form the body’s fast communication network, linking sensation, movement, emotion, memory, and decision making. In psychology and neuroscience, anatomy matters because mental processes depend on physical structures that receive, integrate, and transmit information. The central nervous system includes the brain and spinal cord, while the peripheral nervous system carries signals between the central nervous system and the rest of the body.
Understanding this organization helps explain behavior from reflexes to conscious thought.
Key Facts
- Central nervous system = brain + spinal cord.
- Peripheral nervous system = cranial nerves + spinal nerves + ganglia outside the brain and spinal cord.
- Resting membrane potential of many neurons is about -70 mV.
- Action potentials follow the all-or-none principle and typically peak near +30 mV.
- Signal speed depends strongly on myelination and axon diameter, with myelinated axons conducting faster by saltatory conduction.
- Basic synaptic sequence: action potential reaches terminal, Ca2+ enters, vesicles release neurotransmitter, receptors bind transmitter, postsynaptic potential changes.
Vocabulary
- Neuron
- A specialized nerve cell that receives, processes, and transmits information using electrical and chemical signals.
- Axon
- A long projection of a neuron that carries action potentials away from the cell body toward synaptic terminals.
- Synapse
- A junction where one neuron communicates with another neuron, muscle cell, or gland cell, usually through neurotransmitter release.
- Myelin
- A fatty insulating layer around many axons that increases the speed and efficiency of neural signaling.
- Brainstem
- The lower part of the brain that connects to the spinal cord and helps regulate vital functions such as breathing, heart rate, and arousal.
Common Mistakes to Avoid
- Calling the spinal cord part of the peripheral nervous system is wrong because the spinal cord is part of the central nervous system and serves as a major relay and reflex center.
- Thinking neurotransmitters always excite the next neuron is wrong because the same neurotransmitter can have excitatory or inhibitory effects depending on the receptor type.
- Drawing an action potential as a signal that fades with distance is wrong because a true action potential is regenerated along the axon and does not gradually decrease in size.
- Equating the cerebrum with the whole brain is wrong because the brain also includes the cerebellum and brainstem, which support coordination, balance, arousal, and vital autonomic functions.
Practice Questions
- 1 A myelinated axon conducts a signal at 80 m/s. How long does it take the signal to travel 1.6 m from the spinal cord to a muscle?
- 2 A neuron has a resting membrane potential of -70 mV and reaches a peak of +30 mV during an action potential. What is the total voltage change in millivolts from rest to peak?
- 3 A patient has damage mainly in the cerebellum but an intact cerebrum and brainstem. Predict two functions that may be impaired and explain why those impairments fit the anatomy.