Biology

Biology and Behavior

Chapter 2: Key Concepts

Basic Definitions

  • Neuroscience: The study of the brain and other parts of the nervous system.

  • Biological Psychology: A branch of psychology focusing on how the brain and other biological systems influence human behavior.

Neurons and Neural Communication
Neurons

  • Specialized cells of the nervous system.

  • Function: Communicate with each other via electrical and chemical signals.

Types of Neurons

  1. Sensory Neurons:

    • Function: Receive information from sensory systems and send it to the brain for processing.

    • Role: Input.

  2. Motor Neurons:

    • Function: Transmit information from the brain and spinal cord (central nervous system) to muscles and glands.

    • Role: Output.

  3. Interneurons:

    • Location: Found in the brain or spinal cord.

    • Function: Act as connector neurons.

Parts of a Neuron

  • Dendrites:

    • Function: Receive information from other neurons.

  • Cell Body:

    • Includes nucleus; performs basic cellular activities.

  • Axon:

    • Function: Sends messages to other neurons.

  • Myelin Sheath:

    • Composition: Fatty insulation around the axon.

    • Function: Speeds up transmission of electrical impulses.

  • Axon Terminals:

    • Structure: Small branches at the end of the axon.

    • Function: Form connections with other neurons.

Glial Cells

  • Definition: Cells that support and protect neurons throughout the brain.

How Neurons Communicate
Action Potentials

  • Action Potential:

    • Definition: The release or firing of an electrical impulse that travels through the axon.

    • Process: Dendrites receive a message, leading to axon firing, which then sends the message to other neurons.

Neurotransmitters

  • Definition: Chemical messengers that travel across synapses from one neuron to the next.

  • Synapse: The gap between two neurons.

  • Neurotransmitters are located in vesicles of the axon terminal, with roughly ~100 different types currently identified.

Neurotransmitters Overview

  1. Acetylcholine:

    • Function: Relays messages from neurons to muscles, enabling movement.

    • Imbalances:

      • Too much: Muscle spasms.

      • Too little: Paralysis.

  2. Glutamate:

    • Type: Excitatory neurotransmitter.

  3. GABA:

    • Type: Inhibitory neurotransmitter.

    • Role: Plays a crucial role in preventing overstimulation of the brain.

  4. Norepinephrine:

    • Function: Prepares the body for stressful situations ("fight or flight").

    • Related functions: Attention, arousal, sleep regulation.

  5. Serotonin:

    • Functions: Controls appetite, aggression, and mood; regulates sleep and breathing.

    • Mental health link: Low serotonin levels are linked to depression.

  6. Endorphins:

    • Definition: Naturally produced opioids released in response to pain.

    • Increase in levels with brisk exercise; associated with the phenomenon called "runner's high."

  7. Dopamine:

    • Function: Involved in the body's reward system.

    • Role in attention and learning through reinforcement.

    • Implications in substance abuse disorders.

Agonists and Antagonists

  • Agonists:

    • Definition: Increase the normal activity of a neurotransmitter.

  • Antagonists:

    • Definition: Reduce the activity of a neurotransmitter.

The Nervous System
Central Nervous System (CNS)

  • Components:

    • Brain.

    • Spinal Cord.

Peripheral Nervous System (PNS)

  • Components:

    • Areas outside CNS including ganglia and nerves.

  • Role: Connects the central nervous system to limbs and organs.

The Reflex Arc

  1. Heat activates sensory neurons.

  2. Sensory neurons carry information from the environment to interneurons in the spinal cord.

  3. Interneuron in spinal cord activates motor neuron.

  4. Motor neuron excites muscle, initiating motion that pulls hand away.

  5. Brain receives the message.

Nervous System Divisions

  • Somatic Nervous System:

    • Type: Not automatic; voluntary control.

  • Autonomic Nervous System:

    • Type: Automatic; involuntary control.

    • Further divided into:

      • Sympathetic Nervous System:

      • Function: Prepares the body for action ("fight or flight") by increasing heart rate, dilating pupils, and decreasing digestion.

      • Parasympathetic Nervous System:

      • Function: Returns the body to a resting state ("rest and digest") by decreasing heart rate, constricting pupils, and activating digestive processes.

The Endocrine System

  • Definition: A communication system utilizing glands to release hormones into the bloodstream.

  • Functions: Hormones influence mood, cognition, appetite, and other processes and behaviors.

  • Pituitary Gland: Master gland that influences other glands and promotes growth, located under and controlled by the hypothalamus.

The Brain
Neuroplasticity

  • Definition: The brain's ability to heal, grow new connections, and reorganize to adapt to new environments.

The Cerebrum

  • Description: Largest part of the brain; divided into two distinct hemispheres.

    • Corpus Callosum: Connects the two hemispheres.

    • Hemispheric Control:

    • Right hemisphere controls the left side of the body.

    • Left hemisphere controls the right side of the body.

Lateralization

  • Definition: The tendency for the left and right hemispheres to excel in different activities while still working together.

    • Left hemisphere: Excels in language processing.

    • Right hemisphere: Excels in visual-spatial tasks, facial recognition, and detecting emotion.

Language and the Brain

  1. Left Hemisphere:

    • Critical for language production and comprehension.

    • Broca’s Area: Important region for speech production.

    • Wernicke’s Area: Important for language comprehension.

Cerebral Cortex

  • Description: The wrinkled, outermost layer of the cerebrum, responsible for higher mental functions such as decision making, language, and visual processing.

Four Lobes of the Brain

  1. Frontal Lobe:

    • Functions: Higher-level cognitive functions like thinking, planning, and personality characteristics.

  2. Parietal Lobe:

    • Functions: Integration of sensory information like touch and temperature.

  3. Temporal Lobe:

    • Functions: Hearing and language comprehension.

  4. Occipital Lobe:

    • Functions: Processing of visual information.

The Limbic System

  • Description: A collection of structures regulating emotions and basic drives (e.g., hunger) and aiding in the creation of memories.

Key Structures:

  1. Hippocampus:

    • Function: Processing and forming new memories.

  2. Amygdala:

    • Function: Processes aggression, basic emotions such as fear, and associated memories.

  3. Thalamus:

    • Function: Processes and relays sensory information to appropriate cortical areas.

  4. Hypothalamus:

    • Function: Maintains internal environment, regulating sleep-wake cycles, sexual behavior, and appetite; also connects to the autonomic nervous system.

Structures in the Midbrain and Hindbrain

  1. Midbrain:

    • Contains the reticular formation centralized for arousal and sensory analysis.

  2. Hindbrain:

    • Includes the pons, cerebellum, and medulla.

    • Medulla (Medulla Oblongata): Oversees vital functions like breathing, digestion, and heart rate.

    • Cerebellum: Referred to as the "little brain"; responsible for muscle coordination and balance.