Biology, Behavior, And Mind Essay Examples

Chapter 2: The Biology of Mind

A person’s self is made up of their brain, and all behavior is influenced by biological factors.
Phrenology studied bumps on a person’s skull to determine mental abilities and traits, during the early 1800’s, which led to the idea of localization of function.

Localization of function: idea that different brain regions have specific functions.

Biological perspective: studies the links between biological activity and behavior.
Discoveries of Biological perspective:
The body is made of cells.
Nerve cells communicate with chemical messages sent using electricity across small gaps between them.
Specific brain systems do specific things.
Information in these systems creates all of our experiences.
Brain adapts and works based on experience.
Neural Communication
Human nervous systems are similar enough to other animals’ that we can study theirs to understand ours.
Neurons
Neurons: nerve cells that all have cell body and branching fibers.
Dendrite: fibers that receive information and send it to cell body.
Axon: fibers that send information to muscles, glands, or other neurons.
Myelin sheath: fatty tissue on surrounding some axons that speeds up communication.
Action potential: brief electrical charge that moves down axon.
Contributions to action potential:
Resting potential: axon with positive ions outside, negative ions inside.
Selectively permeable: axon only allows certain things through surface.
Depolarizes: when neuron fires, axon gates open and let positive ions in.
Refractory period: neuron pumps positive ions back out so neuron can fire again.
Excitatory: signal that accelerates neuron.
Inhibitory: signal that keeps neuron from firing.
Threshold: minimum level of signal intensity required to cause action potential.
When threshold is reached, neuron has all-or-none response: neuron always fires with same intensity.
Strong stimulus can increase number of firing neurons and how often they fire.
How Neurons Communicate
Synapse: gap between neurons with a dendrite on one side and an axon on the other.
Neurotransmitters: chemical messengers that move across synaptic gap from axon to dendrite.
Reuptake: when unused neurotransmitters are reabsorbed by the neuron that sent them.
How Neurotransmitters Influence Us
Certain neurotransmitters may affect specific behaviors and emotions, and be divided by brain pathways, but neurotransmitter systems interact.
Types of Neurotransmitters:
Acetylcholine (Ach): Enables muscle action, learning, and memory.
Dopamine: Influences movement, learning, attention, and emotion.
Serotonin: Affects mood, hunger, sleep, and arousal.
Norepinephrine: Helps control alertness and arousal.
GABA (gamma-aminobutyric acid): A major inhibitory neurotransmitter.
Glutamate: A major excitatory neurotransmitter; involved in memory.
Endorphins: types of neurotransmitters similar to morphine, released in response to pain and vigorous exercise.
How Drugs and Other Chemicals Alter Neurotransmission
Drugs and other chemicals either excite or inhibit neurons at synapses by binding to neurotransmitter receptors.
Agonist: mimics neurotransmitter and its effects.
Antagonists: blocks neurotransmitter functioning.
The Nervous System
Nervous system: network in the body that allows fast electrochemical communication; made up of peripheral and central nervous systems.
Central nervous system (CNS): made up of brain and spinal cord.
Peripheral nervous system (PNS): gathers information from the body and sends CNS decisions to the rest of the body.
Nerves: electrical cables made up of bundles of axons; link CNS to sensory receptors, muscles, and glands.
Types of Neurons:
Sensory neurons: send messages from body tissue and sensory receptors to CNS.
Motor neurons: send instructions from CNS to the body’s muscles.
Interneurons: reside within the CNS and communicate internally, acts between sensory and motor communication.
The Peripheral Nervous System
Somatic nervous system: controls the body’s skeletal muscles.
Autonomic nervous system (ANS): controls the glands and muscles of internal organs; divided into sympathetic and parasympathetic.
Sympathetic nervous system: arouses body and expends energy in stressful situations.
Parasympathetic nervous system: calms the body, and conserves energy.
The Central Nervous System
Neural networks: clusters of the brain’s neurons into work groups.
Spinal cord: two-way connection between peripheral nervous system and the brain; sends sensory information up to brain and motor-control information back.

Reflexes: simple, automatic responses to sensory stimuli; often communicate through interneurons in the spinal cord.

The Endocrine System
Set of glands that secrete hormones into the bloodstream; slow chemical communication system.
Hormones: chemical messengers that affect other tissues, including the brain.
Types of glands:
Adrenal glands: helps trigger the “fight-or-flight” response.
Pituitary gland: located in brain and secretes many different hormones, some of which affects other glands; (sort of master gland).
The Brain
The brain enables the mind and consciousness.
The Tools of Discovery: Having Our Head Examined
Lesions: destroying tissue; can be naturally or experimentally caused.
Neuroscientists can now stimulate different parts of the brain and study the effects.
Technologies that retrieve signals from mental activity:
Electroencephalogram (EEG): amplifies and records waves of electrical activity that sweep across the brain’s surface.
PET (positron emission tomography) scan: shows brain activity by detecting where radioactive glucose is used for a given task.
fMRI (functional MRI): compares successive MRI scans which reveals blood flow, and shows brain function.

Older Brain Structures

The Brain Stem: oldest part of the brain; it’s at the core of the brain and begins where spinal cord enters skull.

Allows automatic survival functions.

Medulla: the slight swelling where brainstem begins; controls heartbeat and breathing.
The Thalamus: sensory switchboard on top of the brainstem.
Sends sensory messages to receiving areas in the cortex, and sends replies to cerebellum and medulla.
Reticular formation: nerve network that travels through the brainstem; helps control arousal.
The Cerebellum: the “little brain” at the back of the brainstem
Enables nonverbal learning and memory.
Coordinates voluntary movement and balance.
Processes sensory input.
The Limbic System: neural system that sits between the brain’s older parts and its cerebral hemispheres.
Structures of the limbic system:
Hippocampus: processes conscious memories.
The Amygdala: two lima-bean-sized neural clusters; linked to emotion.
The Hypothalamus: neural structure below thalamus;
Directs maintenance activities such as eating and drinking.
Helps control endocrine system using the pituitary gland.
Linked to emotion and reward.
The Cerebral Cortex: a thin surface layer of interconnected neural cells covering the cerebral hemispheres; body’s ultimate control and information-processing center.

Structure of the Cortex:

Glial cells (glia): cells in the nervous system that support, nourish, and protect neurons; may play a role in learning and thinking.

Frontal lobes: lies just behind the forehead; involved in speaking and muscle movements and in making plans and judgments.

Parietal lobes: lies at the top of the head toward the back; receives sensory input for touch and body position.
Occipital lobes: lies at the back of the head; receives information from the visual fields.
Temporal lobes: lies roughly above the ears; receives auditory information from the opposite ears.
Functions of the Cortex
Motor Functions: movement of specific body parts are controlled by specific areas on the motor cortex; each hemisphere controls the opposite side of the body.

Motor cortex: at the back of the frontal lobe; it controls voluntary movements.

Mapping the Motor Cortex
Body areas that require precise control, like fingers, take up the most space on the motor cortex.
Brain-Computer Interfaces
Researchers have developed computer programs that can monitor brain signals that control, plan, and initiate movement; then the computer acts according to these signals.

This research is currently being used to develop cognitive neural prosthetics.

Sensory Functions
Sensory cortex: at the front of the parietal lobes; registers and processes body touch and movement sensations.
Association Areas: areas not involved in primary motor or sensory functions; they are involved in higher mental functions and found in all four lobes.

Examples of Association areas:

In frontal lobes: enable judgment, planning, and processing of new memories.
In parietal lobes: enable mathematical and spatial reasoning.
Under right temporal lobe: enables us to recognize faces.
The Brain’s Plasticity
Brains are not just sculpted by genes, but also by experience.
Plasticity: the brain’s ability to modify itself after damage, especially during childhood.
Two reasons for brain damage:
Severed neurons usually do not regenerate.
Some brain functions seem preassigned to specific areas.
Some neural tissue can reorganize in response to damage.
Allows blind or deaf people to use unused brain areas for other functions.
Neurogenesis: the formation of new neurons.
Our Divided Brain
The left and right hemispheres serve different functions (lateralization).
Splitting the Brain
Corpus Callosum: the large band of neural fibers connecting the two hemispheres and carrying messages between them.
Split Brain: a condition that results from cutting the corpus callosum; it isolates the brain’s two hemispheres.
Researchers learned that conscious left hemisphere rationalizes behavior performed by the right hemisphere.
Right-Left Differences in the Intact Brain
Left hemisphere
Involved in perceptual tasks.
Used to process speech or sign language.
Right hemisphere
Excels in making inferences; recognizes subtleties of language such as context.
Helps us modulate our speech so our meaning is clear; such as intonation.
Helps orchestrate our sense of self; such as awareness of paralyzed limbs.