Unit 3: Brain and Behavior Flashcards
The Biological Perspective
Focuses on the biological bases of behavior and mental processes
The Central Nervous System
The brain and spinal cord. The brain interprets and stores information and sends orders to muscles, glands, and organs. Spinal cord connects the brain and the peripheral nervous system.
The Peripheral Nervous System
Transmit information to and from the central nervous system, and consists of the autonomic nervous system and somatic nervous system.
The Autonomic Nervous System
Automatically regulates glands, internal organs, and blood vessels, pupil dilation, digestion, and blood pressure, and consists of the parasympathetic division (maintains body functions under ordinary conditions, saves energy) and sympathetic division (prepares the body to react and expand energy in times of stress).
The Somatic Nervous System
Carries sensory information and controls movement of the muscles and consists of the sensory system (afferent), which carries messages from senses to CNS, and the motor system (efferent), which carries messages from CNS to muscles and glands.
Neurons
•Cells that make up the nervous system (brain, spinal cord, etc.)
•100 billion+ neurons
•Cell body (soma) – nucleus with chromosomes
•Dendrites – receive information from other neurons
•Axon – transmits information to other neurons, muscles, and glands
•Myelin:
o Insulating layer of fatty material
o Composed of glial cells
o Helps transmit information down the axon
o Gaps in myelin sheath are called nodes of Ranvier
Types of Neurons
- Sensory (or afferent) neurons: Carry messages from sense organs to spinal cord or brain.
- Motor (or efferent) neurons: Carry messages from spinal cord or brain to muscles and glands.
- Interneurons (or association neurons): Carry messages from one neuron to another.
- Mirror neurons: Specialized neurons (in the frontal and parietal lobes) that become activated when we observe others perform a behavior or express an emotion
- Glial cells (or glia): Cells that insulate and support neurons by holding them together, provide nourishment and remove waste products, prevent harmful substances from passing into brain, and form myelin sheath
The Action Potential
- Neurons communicate through electrochemical impulses.
- A neuron contains charged particles called ions.
- When at rest, the neuron is negatively charged on the inside and positively charged on the outside (the resting potential); at this point, the neuron is in a state of polarization.
- When stimulated, the charge is reversed by allowing positive sodium ions to enter the cell, a process called depolarization.• The action potential is the sequence of electrical charges moving down the cell – the firing of the nerve cell.
- Neurons do not fire in response to a single message from another neuron. A single message causes a small, temporary shift in the electrical charge, called a graded potential. For a neuron to fire, impulses from many neurons must exceed a certain minimum threshold of excitation.
Summary of an Action Potential
- Cell membrane of axon opens
- Positive ions flow into the axon
- Initiates the firing of the neuron
- Transmits the information down the axon
Synapse
- Junction between one neuron’s axon and another’s dendrites/cell body
- Neurotransmitters cross the synapse
- Plays a fundamental role in the communication between neurons
- Presynaptic neuron’s axons end in terminal buttons
- Terminal buttons contain synaptic vesicles
- Synaptic vesicles contain neurotransmitters
- Neurotransmitters are chemicals that transmit information across the synaptic gap (cleft)
- Postsynaptic neuron’s dendrites contain receptor sites
- Receptor sites fit certain neurotransmitters
- Neurotransmitters bind to specific receptor sites in a lock-and-key system
Reuptake
Neurotransmitters are absorbed back into the presynaptic neuron
Enzyme Deactivation (Disassembly)
Neurotransmitters are broken down by enzymes in the synapse
Autoreceptors
- Neurotransmitters bind to autoreceptor sites
* Neurotransmitters passively drift out of the synaptic gap
Neurotransmitters
- Acetylcholine (Ach)
- Dopamine
- Serotonin
- Norepinephrine
- Endorphins
Acetylcholine (Ach)
Enables muscle action, learning and memory. With alzheimers, Ach producing neurons deteriorate.
Dopamine
Influences movement, learning, attention and emotion. High levels linked to schizophrenia, low levels linked to Parkinson’s disease.
Serotonin
Affects mood, hunger, sleep arousal. Low levels linked to depression.
Norepinephrine
Helps control alertness and arousal. Low levels depress mood.
Endorphins
Boosts mood, lessens pain. Artificial opiates cause brain to stop producing endorphins.
Parkinson’s Disease / Symptoms
- Results from the death of neurons that produce dopamine (influences movement)
- Symptoms: Difficulty moving, tremors
The Brain
The brain is the core of the nervous system, the part that makes sense of the information received from the senses, makes decisions, and sends commands out to the muscles and the rest of the body.
Lesioning and brain stimulation studies
We can study the brain by using deep lesioning to destroy certain areas of the brain in laboratory animals or by electrically stimulating those areas. We can also use case studies of human brain damage to learn about the brain’s functions but cannot easily generalize from one case to another.
Mapping brain structure
CT scans are computer-aided X-rays of the brain and show the skull and brain structure. MRI scans use a magnetic field, radio pulses, and a computer to give researchers an even more detailed look at the structure of the brain.
Mapping brain function
The electroencephalograph (EEG) allows researchers to look at the electrical activity of the surface of the brain, through the use of electrodes placed on the scalp that are then amplified and viewed using a computer. PET scans use a radioactive sugar injected into the bloodstream to track the activity of brain cells, which is enhanced and color-coded by a computer. SPECT allows for the imaging of brain blood flow. fMRI tracks changes in the oxygen levels of the blood and can tell researchers what areas of the brain are active.
