The brain and spinal cord form the central nervous system, controlling your thoughts, movements, and bodily functions. The spinal cord transmits signals between the brain and body, while the brain's specialized regions handle complex tasks like memory, emotions, and decision-making. Understanding how these structures work is central to biopsychology because it connects physical brain activity to the behaviors and mental processes you study throughout the course.
The Brain and Spinal Cord
Functions of the Spinal Cord
The spinal cord is a long bundle of nerves running from the base of the brain down through the vertebral column. It has two main jobs: relaying information and producing reflexes.
- Signal transmission: The spinal cord carries messages between the brain and the rest of the body. Ascending pathways send sensory information up to the brain (like pain from a stubbed toe), while descending pathways carry motor commands down from the brain to the muscles (like telling your hand to wave).
- Reflex center: Some responses are too urgent to wait for the brain. In a spinal reflex, sensory neurons send a signal to the spinal cord, which immediately sends a motor response back. When you touch a hot stove, your hand pulls away before the pain signal even reaches your brain. The knee-jerk reflex works the same way.
- Basic processing: The spinal cord also does some initial processing of sensory and motor information, helping coordinate simple movements and filtering signals before they reach the brain.
Regions and Roles of the Brain
The brain is organized into three major divisions: the hindbrain, midbrain, and forebrain. As you move from hindbrain to forebrain, the functions generally shift from basic survival to higher-level thinking.
Hindbrain
The hindbrain sits at the base of the brain, just above the spinal cord. It handles functions you don't consciously think about but can't live without.
- Medulla oblongata: Regulates vital functions like breathing, heart rate, and blood pressure. Damage here can be life-threatening.
- Pons: Acts as a relay station between the cerebral cortex and the cerebellum. It also plays a role in sleep and arousal.
- Cerebellum: Coordinates voluntary motor movements, fine-tunes them for accuracy, and maintains balance and posture. Think of it as the part that lets you walk smoothly instead of stumbling with every step.
Midbrain
The midbrain is a small region between the hindbrain and forebrain that helps with sensory processing and movement.
- Tectum: Processes visual and auditory information and controls orienting responses (like turning your head toward a sudden noise).
- Tegmentum: Involved in motor control, arousal, and sleep regulation.
Forebrain
The forebrain is the largest and most complex part of the brain. It's responsible for everything from processing sensory input to forming memories to making plans.
- Thalamus: The brain's relay station. Almost all sensory information (except smell) passes through the thalamus on its way to the cerebral cortex. Think of it as a switchboard directing signals to the right place.
- Hypothalamus: A small but powerful structure that regulates homeostasis and motivated behaviors like hunger, thirst, body temperature, and sexual drive. It also links the nervous system to the endocrine system through the pituitary gland.
- Limbic system: A group of structures involved in emotion, memory, and learning.
- Amygdala: Processes emotional responses, especially fear and anxiety. It's what triggers your fight-or-flight feeling in a threatening situation.
- Hippocampus: Critical for forming and consolidating new memories. Damage to the hippocampus can prevent a person from creating new long-term memories.
- Cerebral cortex: The wrinkled outer layer of the brain, responsible for higher cognitive functions, perception, and voluntary movement. It's divided into two hemispheres (left and right), each with some specialized functions, and four lobes:
- Frontal lobe: Executive functions, planning, decision-making, personality, and voluntary motor control. The motor cortex sits at the back of this lobe.
- Parietal lobe: Processes touch and body-position information (somatosensory processing), spatial awareness, and attention. The somatosensory cortex sits at the front of this lobe.
- Temporal lobe: Auditory processing, language comprehension (Wernicke's area is here), and memory.
- Occipital lobe: Visual processing and perception. Located at the very back of the brain.
Brain Imaging Techniques in Psychology
Psychologists use imaging tools to study the brain's structure and activity. These fall into two categories: structural (what the brain looks like) and functional (what the brain is doing).
Structural Imaging
| Technique | How It Works | Strengths | Limitations |
|---|---|---|---|
| CT scan | Uses X-rays to create cross-sectional images of the brain | Quick, relatively inexpensive | Limited resolution; exposes patient to radiation |
| MRI | Uses strong magnetic fields and radio waves to produce detailed images of brain structures | High spatial resolution; no radiation | Expensive; time-consuming; patient must remain still |
| Functional Imaging |
| Technique | How It Works | Strengths | Limitations |
|---|---|---|---|
| fMRI | Measures changes in blood flow and oxygenation during mental tasks | High spatial resolution; shows brain activity in real time | Expensive; slight delay between neural activity and the blood flow it measures |
| PET scan | Uses radioactive tracers to measure metabolic activity or neurotransmitter levels | Can study specific neurotransmitter systems | Invasive (requires injection of tracer); expensive; radiation exposure |
| EEG | Measures electrical activity via electrodes on the scalp | Excellent temporal resolution (tracks activity millisecond by millisecond); non-invasive; inexpensive | Low spatial resolution; only detects activity near the brain's surface |
| A quick way to remember the trade-off: fMRI is great at showing where activity happens, while EEG is great at showing when it happens. |
Neural Communication
This section connects to the broader picture of how the brain actually sends and receives information.
- Neurons are the basic cells of the nervous system, responsible for transmitting information through electrical and chemical signals.
- Synapses are the tiny gaps between neurons where one neuron communicates with the next. Signals don't jump directly from cell to cell; instead, they cross the synapse chemically.
- Neurotransmitters are the chemical messengers released into the synapse. When a neuron fires, it releases neurotransmitters that bind to receptors on the next neuron, either exciting it or inhibiting it.
- Brain plasticity (also called neuroplasticity) refers to the brain's ability to reorganize and form new neural connections throughout life. This is how you learn new skills, recover from brain injuries, and adapt to new experiences. Plasticity is greatest during childhood but continues into adulthood.