Bio basis behavior and components of CNS
Biological basis of behavior (e.g., genetics, neurobiology)
The nervous system has two principal divisions:
- the central nervous system (CNS), composed of the brain and spinal cord
- the peripheral nervous system, which encompasses all nerves and ganglia.
Information moves between these divisions through two types of neurons:
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efferent neurons carry signals from the CNS to the body
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afferent neurons carry signals from the body to the CNS
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When you decide to move a limb or respond to an external cue, the CNS sends signals through efferent neurons to the relevant muscles.
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If your hand senses heat from a stove, afferent neurons carry that sensory information back to the CNS, which interprets it as warmth or potential pain.
Components of the CNS
Brain (the control center): The brain processes sensory data, initiates motor functions, and supports cognition (such as thinking and memory). It is subdivided into the forebrain, midbrain, and hindbrain:
Forebrain: Includes the cerebrum, thalamus, limbic system, and hypothalamus, and is essential for abstract thinking, logical reasoning, and emotional processing.
Cerebrum: Governs higher functions such as thought, action, and sensory processing. It is split into lobes:
- Frontal lobe: Involved in decision-making, problem-solving, and planning.
- Parietal lobe: Handles sensory information like touch, temperature, and pain.
- Occipital lobe: Central for visual processing.
- Temporal lobe: Manages auditory processing and supports memory.
Midbrain: Composed of the tegmentum, tectum, and cerebral peduncles.
- It plays a crucial role in dopamine production, affecting habituation and motivation, and assists with vision and hearing.
Hindbrain: Consists of the cerebellum, pons, and medulla (collectively forming the brainstem).
- It oversees vital functions like motor control, respiratory reflexes, digestive reflexes, and sexual arousal.
- Cerebellum: Coordinates voluntary movements, balance, and posture.
- Brainstem (the medulla and pons): Regulates life functions such as heart rate, breathing, and sleep cycles.
- Medulla oblongata: Governs autonomic nervous system actions like blood pressure and heart rate.
- Pons: Serves as a “bridge” linking the hindbrain to the rest of the brain, also aiding in sleep regulation.
Cortical function lateralization
Some functions are primarily managed by one hemisphere of the brain.
The left brain usually controls the right visual field, as well as grammar, speech, writing, and positive emotions.
The right brain tends to oversee the left visual field, recognizing emotions, spatial skills (including facial recognition), and negative emotions.
Spinal cord
The spinal cord carries signals between the brain and the rest of the body. It can also direct reflexes without input from the brain.
Neuronal communication and its influence on behavior
Dopaminergic neurons are triggered by dopamine, a neurotransmitter that plays a vital part in mood and behavior.
When neurons malfunction, conditions like Parkinson’s disease (marked by impaired motor function and sensory loss) or Alzheimer’s disease (involving memory difficulties, mood shifts, and movement difficulties) can emerge.
Influence of neurotransmitters on behavior
Neurotransmitters are chemical messengers in the nervous system. They travel between neurons to relay information. When neurotransmitter levels or functioning are disrupted, behavior and overall well-being can change.
Major neurotransmitters and how they affect behavior
| Neurotransmitter | Involved in | Potential effect on behavior |
|---|---|---|
| Acetylcholine | Muscle action, memory | Increased arousal, enhanced cognition |
| Beta-endorphin | Pain, pleasure | Decreased anxiety, decreased tension |
| Dopamine | Mood, sleep, learning | Increased pleasure, suppressed appetite |
| Gamma-aminobutyric acid (GABA) | Brain function, sleep | Decreased anxiety, decreased tension |
| Glutamate | Memory, learning | Increased learning, enhanced memory |
| Norepinephrine | Heart, intestines, alertness | Increased arousal, suppressed appetite |
| Serotonin | Mood, sleep | Modulated mood, suppressed appetite |
Table adapted from OpenStax