Psychology: Biological Foundations of Behavior

The Whole Brain Atlas 

Biological Foundations of Behavior

Neurons

Neurons are the basic building blocks of the nervous system—the body’s wiring through which messages are transmitted within the nervous system. 

Our neural network has 100 billion neurons

An increase in myelin helps speed up reactions and helps make movements smoother and more sophisticated

Each neuron is a single cell, consisting of a cell body (or soma), an axon, and dendrites. The soma is the main body of the cell and contains the Nucleus. The nucleus performs metabolic, or life-sustaining, functions of the cell. The axon,is a long cable that projects from the soma and conducts outgoing messages to other neurons. Axons may branch off like the stems of plants, fanning out in different directions. At the ends of these branches are knoblike swellings called terminal buttons. It is here that chemicals called neurotransmitters are stored and released.Neurotransmitters are chemical messengers that transport nerve impulses from one nerve cell to another

 Dendrites are treelike structures that project from the soma. Dendrites have receptor sites, or docking stations, that enable them to receive neurotransmitters released by neighboring neurons.

The Neural Impulse

• At rest, a neuron is negatively charged (resting potential)
• As an electrical message sweeps through, it changes the neuron to positive for just a blip of time, then the neuron is back to negative (action potential)
• All-or-nothing Principle: neuron either fires or does not fire
• Must reach a threshold before firing
• Strength does not vary
• Speed can vary and  is controlled by how thick the myelin is and the length of the axons. The longer the axon, the slower the electrical message

The nervous system has three types of neurons: sensory neurons, motor neurons, and interneurons.

• sensory neurons: Neurons that transmit information from sensory organs, muscles, and inner organs to the spinal cord and brain.
• motor neurons: Neurons that convey nerve impulses from the central nervous system to muscles and glands.
• interneurons: Nerve cells within the central nervous system that process information.

A nerve is a bundle of axons from different neurons.

Both inside and outside the neuron are electrically charged atoms and molecules called ions.

The Nervous System

nervous system The network of nerve cells and support cells for communicating and processing information from within and outside the body.

The nervous system has two major divisions which include:

• the central nervous system: consists of the brain and spinal cord, processes information it receives from the peripheral nervous system and issues commands carried through the peripheral nervous system to muscles and other organs in the body.
• the peripheral nervous system: a network of nerves connecting the central system to sensory organs, muscles, and glands throughout the body.
  • Divided into two parts
    • the somatic nervous system
      • composed of sensory and motor neurons.
    • the autonomic nervous system (ANS).
      • Divided into two branches
        • sympathetic nervous system 
        • parasympathetic nervous system 

The Brain

The brain is divided into three major parts:

The hindbrain: The lowest part of the brain. The hindbrain includes the medulla, pons, and cerebellum. These structures control such basic life-support functions as breathing and heart rate. The medulla and pons contain sensory neurons that transmit information from the spinal cord to the forebrain. The cerebellum is involved in controlling balance and coordination.

The midbrain lies above the hindbrain. The midbrain contains nerve pathways that connect the hindbrain with the forebrain. Structures in the midbrain perform important roles, including control of automatic movements of the eye muscles, which allows you to keep your eyes focused on an object as your head changes position in relation to the object.

• Reticular formation is a weblike formation of neurons involved in regulating states of attention, alertness, and arousal.

The forebrain is located toward the top and front of the brain and is the largest part of the brain. The major structures in the forebrain are the thalamus, the hypothalamus, the limbic system, and the cerebral cortex.

• thalamus: A structure in the forebrain that serves as a relay station for sensory information and that plays a key role in regulating states of wakefulness and sleep
• basal ganglia: An assemblage of neurons lying in the forebrain that is important in controlling movement and coordination.
• hypothalamus: A small, pea-sized structure in the forebrain that helps regulate many vital bodily functions, including body temperature and reproduction, as well as emotional states, aggression, and responses to stress.
• limbic system: A formation of structures in the forebrain that includes the hippocampus, amygdala, and parts of the thalamus and hypothalamus.
  • amygdala: A set of almond-shaped structures in the limbic system believed to play an important role in aggression, rage, and fear.
  • hippocampus A structure in the limbic system involved in memory formation.
• cerebral cortex: The wrinkled, outer layer of gray matter that covers the cerebral hemispheres; controls higher mental functions, such as thought and language

Brainstem, the “stem” or “stalk” that connects the spinal cord to the higher regions of the brain

Broca’s area in the left frontal lobe that is egg-shaped and plays a key role in the production of speech

Wernicke’s area, which is located in the temporal lobe, enables us to understand written or spoken language. 

The Endocrine System

The endocrine system is a grouping of glands located in various parts of the body that release secretions, called hormones, directly into the bloodstream.

Functions:

• The endocrine system regulates important bodily processes, such as growth, reproduction, and metabolism.
• One of the important functions of the endocrine system is helping to maintain an internally balanced state, or homeostasis, in the body

insulin: a hormone produced by the pancreas, regulates the concentration of glucose (sugar) in the blood.

pituitary gland: An endocrine gland in the brain that produces various hormones involved in growth, regulation of the menstrual cycle, and childbirth.

pineal gland: A small endocrine gland in the brain that produces the hormone melatonin, which is involved in regulating sleep–wake cycles.

adrenal glands: A pair of endocrine glands located just above the kidneys that produce various stress-related hormones.

The gonads are the sex glands—ovaries in women and testes in men.

• The gonads produce the germ cells—egg cells in women and sperm in men.
• The ovaries also produce the female sex hormones estrogen and progesterone, which help regulate the menstrual cycle. Progesterone also stimulates growth of the female reproductive organs and helps the uterus maintain pregnancy.
  • premenstrual syndrome (PMS): A cluster of physical and psychological symptoms occurring in the few days preceding the menstrual flow.
• The testes produce the male sex hormone, testosterone, which leads to the development of male sex organs in male fetuses.

Genes & Behavior

One of the oldest discussions in psychology is the nature–nurture debate. Is our behavior governed by nature (genetics) or nurture (environment and culture)?

Genes: a basic unit of heredity which is found at a specific point on a chromosome

Chromosome: a microscopic rod-shaped body in the cell nucleus carrying genes that transmit hereditary traits from generation to generation. humans normally have 46 chromosomes

• Dominant-recessive genes principle: dominant genes override recessive genes
• Recessive genes appear only if both genes in a pair are recessive
• Sex Chromosomes: the 23rd pair of chromosomes, whose genetic material determines the sex of the individual.
  • X shape chromosome from the mother and a X or Y from the father. If the baby receives an X from the father then the baby becomes female and if Y then baby becomes a male.

DNA: acronym for deoxyribonucleic acid, the substance that forms the basic material of chromosomes; takes the form of double helix and contains genetic code

allele is a specific version of a gene

Behavior genetics: the study of heredity’s influence on behavior

• Genes and environment will always depend on each other

Genetics: the area of biology that focuses on heredity

Heredity: the transmission of traits from parent to offspring by means of genes

A person’s genotype is the genetic makeup of that individual.

Phenotype refers to the individual’s inherited physical characteristics, which are a combination of genetic and environmental influences.

Charles Darwin published the Descent of Man, which made the case that humans, like other species, were a product of evolution.

He argued that apes and humans have a common ancestor.

natural selection: the concept that holds that adaptive genetic variations among members of a species enable individuals with those variations to survive and reproduce

the theory of evolution by natural selection: the theory states that organisms that are better suited for their environment will survive and reproduce, while those that are poorly suited for their environment will die off

Mutation: a sudden variation  in an inheritable characteristic, as distinguished from a variation that results from generations of gradual selection

Evolutionary Psychology: the branch of psychology that studies the ways in which adaptation and natural selection are connected with mental processes and behavior

Instinct: a stereotyped pattern of behavior that is triggered by particular stimulus and nearly identical among members of a species, even when reared in isolation

Multiple sclerosis (MS) is a chronic and often crippling disease of the central nervous system, affecting about one in one thousand adults, in which the body’s own immune system attacks and eventually destroys the myelin sheath.

aphasia: a disruption in the ability to understand or produce language

Wernicke's aphasia: a language disorder characterized by difficulty comprehending the meaning of spoken language

Epilepsy: temporary disturbances of brain functions that involve sudden neural discharges.

Down syndrome: a condition caused by an extra chromosome on the 21st pair and characterized by mental deficiency, a broad face, and slanting eyes