Neuroscience and Behavior
KEY POINTS
Introduction: Neuroscience and Behavior
Psychological and biological processes are closely linked. Biological psychologists investigate the physical processes that underlie psychological experience and behavior. Neuroscience is the study of the nervous system, especially the brain.
The Neuron: The Basic Unit of Communication
Information in the nervous system is transmitted via cells specialized for communication, called neurons. There are three basic types of neurons: sensory neurons, motor neurons, and interneurons.
Most neurons have three basic components: a cell body, dendrites, and an axon.
Glial cells help neurons by providing structural support, removing waste products, and producing the myelin sheath, which helps insulate one axon from other axons. Glia are also involved in brain development and the communication of information between neurons.
Within the neuron, information is communicated in the form of brief electrical messages called action potentials. The minimum level of stimulation required to activate a neuron is called the stimulus threshold. A neuron’s resting potential is the state in which it is ready to activate and communicate its message if sufficiently stimulated. According to the all-or-none law, either a neuron is sufficiently stimulated and an action potential results, or it isn’t sufficiently stimulated and an action potential doesn’t occur.
The point of communication between two neurons is called the synapse. Neurons communicate information to other neurons either electrically or chemically. In chemical communication, neurotransmitters cross the synaptic gap and affect neighboring neurons. These neurotransmitters are held within synaptic vesicles, which float in axon terminals. The entire process of transmitting information at the synapse is called synaptic transmission. Reuptake is the process in which neurotransmitter molecules detach from the receptor and are reabsorbed and recycled.
There are many different kinds of neurotransmitters, which send either excitatory or inhibitory messages to the receiving neuron. Some drugs influence behavior and mental processes by influencing neurotransmitter activity. Important neurotransmitters include acetylcholine, dopamine, serotonin, norepinephrine, GABA, glutamate, and endorphins.
Drugs can mimic specific neurotransmitters. An agonist is a drug or other chemical that binds to a receptor. A drug can also act as an antagonist by blocking the effect of neurotransmitters.
The Nervous System and the Endocrine System: Communication Throughout the Body
The nervous system is divided into two main divisions: the central nervous system (CNS) and the peripheral nervous system. The central nervous system is composed of the brain and the spinal cord. The spinal cord can produce spinal reflexes.
The peripheral nervous system consists of all the nerves outside the central nervous system. The two main subdivisions of the peripheral nervous system are the somatic nervous system and the autonomic nervous system. The autonomic nervous system is divided into the sympathetic nervous system and the parasympathetic nervous system.
The endocrine system is composed of glands that secrete hormones into the bloodstream, regulating many body functions, including physical growth, stress response, and sexual development. The endocrine system itself is regulated by the hypothalamus in the brain. Under the direction of the hypothalamus, the pituitary gland directly controls hormone production in other endocrine glands as well as hormones that act on physical processes. Oxytocin is a hormone involved in reproduction, social motivation, and social behavior. Another set of glands, called the adrenal glands, which include the adrenal cortex and the adrenal medulla, produce hormones that are involved in the human stress response. The gonads are endocrine glands that secrete hormones that regulate sexual characteristics and reproductive processes.
A Guided Tour of the Brain
Most psychological processes involve the integrated processing of information via neural pathways in multiple brain structures and regions.
The human brain can change in response to environmental stimulation, training, or experience, displaying both functional plasticity and structural plasticity.
Evidence suggests that neurogenesis, the development of new neurons, can occur in the adult brain.
The major regions of the brain are the hindbrain, the midbrain, and the forebrain. Combined, the hindbrain and midbrain structures constitute the brainstem. Sensory and motor pathways cross over in the hindbrain. The key structures of the hindbrain are the medulla, the cerebellum, and the pons. The reticular formation is located in the core of the medulla and the pons.
Auditory and visual information is integrated and coordinated in the midbrain. The substantia nigra is involved in motor control and contains a concentration of neurons that produce dopamine.
The outer portion of the forebrain is called the cerebral cortex. The cerebral cortex is divided into the left and right cerebral hemispheres, with the corpus callosum serving as the main communication link between them. Each hemisphere is divided into four lobes. The temporal lobe contains the primary auditory cortex. The occipital lobe contains the primary visual cortex. The parietal lobe contains the somatosensory cortex. The frontal lobe contains the primary motor cortex. The remainder of the cerebral cortex is composed of association areas.
The limbic system structures are found beneath the cerebral cortex and form neural circuits that play critical roles in learning, memory, and emotional control. The limbic system includes part of the frontal cortex and the hippocampus, thalamus, hypothalamus, and amygdala.
Specialization in the Cerebral Hemispheres
The notion that particular areas of the brain are associated with particular functions is called cortical localization. In the mid-1800s, it was discovered that damage to the left hemisphere produced disruptions in speech and language called aphasia. Different forms of aphasia include Broca’s aphasia and Wernicke’s aphasia. Damage to the same areas of the right hemisphere did not produce aphasia. The notion that specific psychological or cognitive functions are processed primarily on one side of the brain is called lateralization of function.
More evidence for the specialized abilities of the two hemispheres has resulted from the split-brain operation, in which the corpus callosum connecting the two hemispheres is cut. Roger Sperry and his colleagues demonstrated the different strengths of each hemisphere in split-brain patients. The left hemisphere is specialized for language tasks, and the right hemisphere is specialized for visual-spatial tasks.
Match each of the terms on the left with its definition on the right. Click on the term first and then click on the matching definition. As you match them correctly they will move to the bottom of the activity.
biological psychology neuroscience neuron sensory neuron motor neuron interneuron cell body dendrites axon glial cells myelin sheath action potential stimulus threshold resting potential synapse synaptic gap axon terminals synaptic vesicles neurotransmitters synaptic transmission reuptake acetylcholine dopamine serotonin norepinephrine glutamate GABA (gamma-aminobutyric acid) endorphins agonist antagonist nervous system nerves central nervous system (CNS) spinal reflexes peripheral nervous system somatic nervous system autonomic nervous system sympathetic nervous system parasympathetic nervous system endocrine system hormones pituitary gland oxytocin adrenal glands adrenal cortex adrenal medulla gonads phrenology cortical localization functional plasticity structural plasticity neurogenesis brainstem hindbrain medulla pons cerebellum reticular formation midbrain substantia nigra forebrain cerebral cortex cerebral hemispheres corpus callosum temporal lobe occipital lobe parietal lobe frontal lobe limbic system hippocampus thalamus hypothalamus amygdala cortical localization lateralization of function aphasia split-brain operation | Chemical messengers manufactured by a neuron. An area on each hemisphere of the cerebral cortex, near the temples, that is the primary receiving area for auditory information. The notion that specific psychological or cognitive functions are processed primarily on one side of the brain. The multiple short fibers that extend from a neuron’s cell body and receive information from other neurons or from sensory receptor cells. A network of nerve fibers located in the center of the medulla that helps regulate attention, arousal, and sleep; also called the reticular activating system. Neurotransmitter that causes muscle contractions and is involved in learning and memory. The nearly symmetrical left and right halves of the cerebral cortex. A highly specialized cell that communicates information in electrical and chemical form; a nerve cell. The branch of the autonomic nervous system that maintains normal bodily functions and conserves the body’s physical resources. A brief electrical impulse by which information is transmitted along the axon of a neuron. The process through which neurotransmitters are released by one neuron, cross the synaptic gap, and affect adjoining neurons. The pair of endocrine glands that are involved in the human stress response. The division of the nervous system that includes all the nerves lying outside the central nervous system. A region of the brain made up of the hindbrain and the midbrain. Chemical messengers secreted into the bloodstream primarily by endocrine glands. The branches at the end of the axon that contain tiny pouches, or sacs, called synaptic vesicles. The wrinkled outer portion of the forebrain, which contains the most sophisticated brain centers. Neurotransmitters that regulate pain perceptions. Hormone involved in reproduction, social motivation, and social behavior. Neurotransmitter involved in learning, memory, and regulation of sleep; also a hormone manufactured by adrenal glands. The study of the nervous system, especially the brain. The type of neuron that signals muscles to relax or contract. The system of glands, located throughout the body, that secrete hormones into the bloodstream. An area at the back of each cerebral hemisphere that is the primary receiving area for visual information. Neurotransmitter that usually communicates an inhibitory message. A group of forebrain structures that form a border around the brainstem and are involved in emotion, motivation, learning, and memory. A pseudoscientific theory of the brain that claimed that personality characteristics, moral character, and intelligence could be determined by examining the bumps on a person’s skull. The branch of the autonomic nervous system that produces rapid physical arousal in response to perceived emergencies or threats. The notion that different functions are located or localized in different areas of the brain; also called localization of function. A large, two-sided hindbrain structure at the back of the brain; responsible for muscle coordination and maintaining posture and equilibrium. The primary internal communication network of the body; divided into the central nervous system and the peripheral nervous system. A curved forebrain structure that is part of the limbic system and is involved in learning and forming new memories. The division of the nervous system that consists of the brain and spinal cord. Bundles of neuron axons that carry information in the peripheral nervous system. Neurotransmitter involved in the regulation of bodily movement, thought processes, and rewarding sensations. The type of neuron that conveys information to the brain from specialized receptor cells in sense organs and internal organs. A region at the base of the brain that contains several structures that regulate basic life functions. Drug or other chemical substance that binds to a receptor site and triggers a response in the cell. A white, fatty covering wrapped around the axons of some neurons that increases their communication speed. The largest lobe of each cerebral hemisphere; processes voluntary muscle movements and is involved in thinking, planning, and emotional control. The subdivision of the peripheral nervous system that communicates sensory information to the central nervous system and carries motor messages from the central nervous system to the muscles. The brain’s ability to shift functions from damaged to undamaged brain areas. A hindbrain structure that connects the medulla to the two sides of the cerebellum; helps coordinate and integrate movements on each side of the body. An area of the midbrain that is involved in motor control and contains a large concentration of dopamine-producing neurons. A surgical procedure that involves cutting the corpus callosum. Simple, automatic behaviors that are processed in the spinal cord. The tiny space between the axon terminal of one neuron and the dendrite of an adjoining neuron. The largest and most complex brain region, which contains centers for complex behaviors and mental processes; also called the cerebrum. The tiny pouches or sacs in axon terminals that contain chemicals called neurotransmitters. The notion that different functions are located or localized in different areas of the brain; also called localization of function. The outer portion of the adrenal glands. Neurotransmitter that usually communicates an excitatory message. An area on each hemisphere of the cerebral cortex located above the temporal lobe that processes somatic sensations. An almond-shaped cluster of neurons in the brain’s temporal lobe, involved in memory and emotional responses, especially fear. Neurotransmitter involved in sensory perceptions, sleep, and emotions. The development of new neurons. The type of neuron that communicates information from one neuron to the next. A drug or other chemical substance that blocks a receptor site and inhibits or prevents a response in the receiving cell. The state in which a neuron is prepared to activate and communicate its message if it receives sufficient stimulation. The long, fluid-filled tube that carries a neuron’s messages to other body areas. The specialized branch of psychology that studies the relationship between behavior and bodily processes and systems; also called biopsychology or psychobiology. A forebrain structure that processes sensory information for all senses except smell, relaying that information to the cerebral cortex. The middle and smallest brain region, involved in processing auditory and visual sensory information. The endocrine gland attached to the base of the brain that secretes hormones affecting the function of other glands as well as hormones that act directly on physical processes. The process by which neurotransmitter molecules detach from a post-synaptic neuron and are reabsorbed by a presynaptic neuron so they can be recycled and used again. The part of a cell that processes nutrients and provides energy for the neuron to function; contains the cell’s nucleus; also called the soma. The endocrine glands that secrete hormones that regulate sexual characteristics and reproductive processes; ovaries in females and testes in males. The point of communication between two neurons. The brain’s ability to change its physical structure in response to learning, active practice, or environmental influences. The inner portion of the adrenal glands, which secretes epinephrine and norepinephrine. A hindbrain structure that controls vital life functions such as breathing and circulation. The support cells that assist neurons by providing structural support, nutrition, and removal of cell wastes; glial cells manufacture myelin. A peanut-sized forebrain structure that is part of the limbic system and that regulates behaviors related to survival, such as eating, drinking, and sexual activity. The subdivision of the peripheral nervous system that regulates involuntary functions. The partial or complete inability to articulate ideas or understand spoken or written language because of brain injury or damage. The minimum level of stimulation required to activate a particular neuron. A thick band of axons that connects the two cerebral hemispheres and acts as a communication link between them. |
Pierre Paul Broca (1824-1880) French surgeon and neuroanatomist who in 1861 discovered an area on the lower left frontal lobe of the cerebral cortex that, when damaged, produces speech disturbances but no loss of comprehension. (p. 73)
Roger Sperry (1913-1994) U.S. psychologist who received the Nobel prize in 1981 for his pioneering research on brain specialization in split-brain patients. (p. 75)
Karl Wernicke (1848-1905) German neurologist who in 1874 discovered an area on the left temporal lobe of the cerebral cortex that, when damaged, produces meaningless or nonsensical speech and difficulties in verbal or written comprehension. (p. 73)