Psychology Chapter 2 - The Biological Perspective

Nervous system

A network of cells that carries information to and from all parts of the body

Neuroscience

Field of study that deals with the structure of the brain and components of the nervous system

Glial cells

• Provide physical and metabolic support to neurons

• Communicate with other cells

• Specific types have stem cell-like properties

• Influence thinking, memory, and other forms of cognition

Oligodendrocyte (glial cell)

Produce myelin in the central nervous system

Schwann cell (glial cell)

Produce myelin in the peripheral nervous system

Myelin

Insulates axons and speeds up transmission of neural message

• A nerve is a bundle/”cable” of myelinated axons

Neurons

Specialized cells in nervous system; send and receive messages within that system

Major components of a neuron

• Dendrites: receive input

• Soma

• Axons: carry the neural message to other cells

• Axon terminals: are the site of neurotransmitter release

Dendrite

Branchlike structures of a neuron that receive messages from other neurons

Soma

The cell body of the neuron responsible for maintaining the life of the cell

Axon

Tubelike structure of a neuron that carries the neural message from the cell body to the axon terminals for communication with other cells

Axon terminals

Enlarged ends of axonal branches of the neuron, specialized for communication between cells

Resting potential of a neuron

• Negative electrical charge at rest (resting potential)

• Made possible by balance between ions in and outside of the cell

• Membrane is semipermeable; inside is negatively charged as compared to outside

Action potential

Change in the electrical charge can result in an action potential

• Cell fires; inside becomes positive relative to outside

• Fire in an all-or-none fashion; it is the firing rate and number of neurons firing that conveys the strength of the stimulus

• Cell firing is dependent on sum of excitatory and inhibitory messages received by the cell

Synapse

Neurons are separated by this gap

• When the nerve impulse reaches axon terminals, neurotransmitter (NT) is released into synaptic space

• NTs move across synapse and activate ion channel receptor sites on adjacent cells; some NTs are agonistic/excitatory, others are antagonistic/inhibitory

How are neurotransmitters “cleaned” from the synapse?

NTs end back up in the releasing cell through reuptake or broken down by enzymes, stopping their action

Neurotransmitters

Chemicals that have an effect on neurons

Acetylcholine (ACh)

• Excitatory or inhibitory

• involved in arousal, attention, memory; controls muscle contractions

Norepinephrine (NE)

• Mainly excitatory

• Involved in arousal and mood

Dopamine (DA)

• Excitatory or inhibitory

• Involved in control of movement and sensations of pleasure

• Associated with Parkinson’s disease and schizophrenia

Serotonin (5-HT)

• Excitatory or inhibitory

• Involved in sleep, mood, anxiety, and appetite

Gamma-aminobutyric acid (GABA)

• Major inhibitory neurotransmitter

• Involved in sleep; inhibits movement

• High amounts are released when drinking alcohol

Glutamate

• Major excitatory neurotransmitter

• Involved in learning, memory formation, nervous system development, and synaptic plasticity

Endorphins

• Inhibitory neural regulators

• Involved in pain relief

Older methods of brain studies

• Often relied on dissection techniques after death

• Were unable to directly observe function

Gray matter

Dendrites, neuronal cell bodies; responsible for conducting, processing, and sending info to various parts of the body

Found in outer brain regions

White matter

Myelinated axons; responsible for sensory info interpretation from various parts of the body

Found in inner brain regions

Lesioning studies

• Study nonhuman animals or humans with brain damage; damage may be by accident, injury, or in animals, deliberate

• An invasive technique

• Brain areas can be studied according to location of lesions (injured or destroyed areas)

• Not easily generalized from one case to another

Brain stimulation studies

Brain areas can be studied through a variety of stimulation methods, including methods using electricity (ESB) or light

Invasive brain stimulation studies

• Deep brain stimulation (DBS)

• Optogenetics

Noninvasive brain stimulation studies

• Repetitive transcranial magnetic stimulation (rTMS)

• Transcranial direct current stimulation (tDCS)

Neuroimaging

Methods for studying structures and/or activity of the living brain

• Mapping function: electroencephalogram (EEG), positron emission tomography (PET), functional MRI (fMRI), functional near-infrared spectroscopy (fNIRS)

• Mapping structure: computed tomography (CT), magnetic resonance imaging (MRI)

Computed tomography (CT)

Based on x-ray technology; good for imaging brain structure, especially when there is metal in the body

Magnetic resonance imaging (fMRI)

Superior spatial resolution for structure

Electroencephalogram (EEG)

• Has good temporal but relatively poor spatial resolution

• Records the electrical activity of the brain through the use of scalp electrodes

• Both spontaneous activity and event-related potentials (ERP) can be studied

• Activity can be classified according to frequency and morphology; traditional bands include delta, theta, alpha, and beta

Positron emission tomography (PET)

• Used for imaging function

• Involves injection of a radioactive tracer that binds to glucose

• Records activity of cells that use radioactive glucose

Functional MRI (fMRI)

• Images brain function over a time period through tracking changes in blood oxygen levels

• Increases in oxygen levels are associated with increased functioning

Functional near-infrared spectroscopy (fNIRS)

Uses near-infrared light to measure cortical blood oxygen levels

MCQ: What part of the nervous system takes info from the senses and sends commands to the muscles and the rest of the body?

Peripheral nervous system (PNS)

MCQ: What are the functions of the right hemisphere?

Processes info in a more global sense (perception, visualization, spatial perception, recognition of patterns, faces, and emotional expression)

MCQ: What part of the autonomic nervous system stimulates rest and response when one is calm and relaxing?

Parasympathetic nervous system (PSNS)

MCQ: What is the brain’s ability to adapt to damage or change input?

Neuroplasticity

What part of the nervous system is activated when biking, walking, smelling a flower, or scratching an itch?

Somatic nervous system

Compared to the male brain, why do female brains have more gray matter?

To help process information; hormones and genetics

Hindbrain

Involved in heart rate, breathing, arousal, and gross motor movements

• Medulla

• Pons

• Reticular formation

• Cerebellum

Medulla

The first large swelling at the top of the spinal cord, forming the lowest part of the brain, which is responsible for life-sustaining functions such as breathing, swallowing, and heart rate.

Pons

The larger swelling above the medulla that connects the top of the brain to the bottom and that plays a part in sleep, dreaming, left–right body coordination, and arousal.

Reticular formation (RF)

An area of neurons running through the middle of the medulla and the pons and slightly beyond that is responsible for general attention, alertness, and arousal.

• Contains the reticular activating system (RAS)

Cerebellum

Part of the lower brain located behind the pons that controls and coordinates involuntary, rapid, fine motor movement and may have some cognitive functions

Limbic system

Involved in emotions, memory, learning, and motivation

• Thalamus

• Hypothalamus

• Hippocampus

• Amygdala

• Cingulate cortex

Thalamus

Part of the limbic system located in the center of the brain, this structure relays sensory information from the lower part of the brain to the proper areas of the cortex and processes some sensory information before sending it to its proper area.

Hypothalamus

Small structure in the brain located below the thalamus and directly above the pituitary gland, responsible for motivational behavior such as sleep, hunger, thirst, and sex.

Hippocampus

Curved structure located within each temporal lobe, responsible for the formation of long-term declarative memories.

Amygdala

Brain structure located near the hippocampus, responsible for fear responses and memory of fear.

Cingulate cortex

Found right above the corpus callosum in the frontal and parietal lobes and plays an important role in both emotional and cognitive processing.

Cortex

Outermost covering of the brain consisting of densely packed neurons, responsible for higher thought processes and interpretation of sensory input.

• Comprised of left and right hemispheres, connected by corpus callosum

• Each hemisphere can be further divided into four lobes

Frontal lobe

Areas of the brain located in the front and top, responsible for higher mental processes and decision-making as well as the production of fluent speech.

• Contains prefrontal cortex (responsible for executive functions), motor cortex, and mirror neurons

• Left frontal lobe contains Broca’s area

Temporal lobe

Areas of the cortex located along the side of the brain, starting just behind the temples, containing the neurons responsible for the sense of hearing and meaningful speech.

• Contains primary auditory cortex, auditory association area, hippocampus, and amgydala

• Left temporal lobe contains Wernicke’s area

Parietal lobe

Sections of the brain located at the top and back of each cerebral hemisphere containing the centers for touch, temperature, and body position.

• Contains somatosensory cortex

Occipital lobe

Section of the brain located at the rear and bottom of each cerebral hemisphere containing the primary visual centers of the brain.

• Contains primary visual cortex and visual association cortex

Association areas

Areas within each lobe of the cortex responsible for the coordination and interpretation of information, as well as higher mental processing.

• Damage to right association areas can result in spatial neglect where individual fails to recognize the left side of the visual field

Broca’s area

Found in left frontal lobe

• Coordinates brain areas responsible for speech production

• Damage to this area can result in Broca’s aphasia

Broca’s aphasia

Condition resulting from damage to Broca’s area, causing the affected person to be unable to speak fluently, to mispronounce words, and to speak haltingly.

Wernicke’s area

Found in left temporal lobe

• Plays a role in understanding the meaning of words

• Damage to this area can result in Wernicke’s aphasia

Wernicke’s aphasia

Condition resulting from damage to Wernicke’s area, causing the affected person to be unable to understand or produce meaningful language.

Cerebral hemispheres

Some brain functions are governed by one hemisphere more than the other

• Differences found due to work of various researchers (e.g. split-brain studies)

Left hemisphere

Specializes in tasks that involve sequence and analysis (language, speech, handwriting, math)

Central nervous system

Part of the nervous system consisting of the brain and spinal cord.

Brain

True core of nervous system

• Takes info from senses, processes it, makes decisions, and sends commands to rest of body

• Exhibits a great deal of neuroplasticity

• May also change through neurogenesis

Spinal cord

A long bundle of neurons that carries messages between the body and the brain and is responsible for very fast, lifesaving reflexes.

Reflex arc

• Involve several different neurons (sensory neurons → interneurons → motor neurons)

• Enable fast, often lifesaving, actions that do not require conscious thought

Afferent (sensory) neuron

A neuron that carries information from the senses to the central nervous system.

Efferent (motor) neuron

A neuron that carries messages from the central nervous system to the muscles of the body.

Interneuron

A neuron found in the center of the spinal cord that receives information from the afferent neurons and sends commands to the muscles through the efferent neurons. Interneurons also make up the bulk of the neurons in the brain.

Neuroplasticity

The ability within the brain to constantly change both the structure and function of many cells in response to experience or trauma.

Neurogenesis

The formation of new neurons; occurs primarily during prenatal development but may also occur at lesser levels in some brain areas during adulthood.

Epigenetics

The interaction between genes and environmental factors that influence gene activity; environmental factors include diet, life experiences, and physical surroundings.

Peripheral nervous system (PNS)

Comprised of the nerves and neurons not contained in the brain and spinal cord

• Allows the brain and spinal cord to communicate with the sensory systems and to control the muscles and glands of the body

• Divided into somatic and autonomic nervous systems

Somatic nervous system

Controls voluntary/skeletal muscles of the body

• Involves the sensory and motor pathways

• Can move involuntarily as the result of a reflex response

Autonomic nervous system

Controls automatic functions of the body (organs, glands, involuntary muscles)

• Involves the sympathetic and parasympathetic divisions

• Controlled by clumps of neurons on/near the spinal column

Sympathetic division

“Fight or flight” functions; reacts to stressful events and body arousal

Parasympathetic division

“Eat, drink, and rest” functions; restores body to normal functioning after arousal and is responsible for day-to-day functioning of glands and organs

Glands

Organs in the body that secrete chemicals

• Some affect functioning of the body but not behavior

• Others have widespread influence on the body and behavior

Endocrine glands

Glands that secrete chemicals called hormones directly into the bloodstream.

• Affect behavior and emotions by influencing the activity of the brain and by controlling muscles and organs such as the heart, pancreas, and sex organs

Pituitary gland

Gland located in the brain that secretes human growth hormone and influences all other hormone-secreting glands.

Oxytocin

Hormone released by the posterior pituitary gland that is involved in reproductive and parental behaviors.

Pineal gland

Endocrine gland located near the base of the cerebrum; secretes melatonin.

Thyroid gland

Endocrine gland found in the neck; regulates metabolism.

Pancreas

Endocrine gland; controls the levels of sugar in the blood.

Gonads

Sex glands (ovaries in females, testes in males); secrete hormones that regulate sexual development and behavior as well as reproduction.

Adrenal glands

Endocrine glands located on top of each kidney.

Adrenal medulla

Releases epinephrine and norepinephrine when people are under stress and aids in sympathetic arousal.

Adrenal cortex

Secrete over 30 different hormones (corticoids — ex: cortisol) to deal with stress, regulate salt intake, and provide a secondary source of sex hormones affecting the sexual changes that occur during adolescence.