Copyright 2003 Prentice Hall2-1 Behavioral Neuroscience Chapter 2
Copyright 2003 Prentice Hall2-2 The Evolutionary Perspective The evolutionary perspective stresses the role of physiological structures and behaviors in an organism's adaptation to the environment and ultimate survival. Natural SelectionThe principle of natural selection states that the most fit organisms survive because they adapt best to the environment and thus pass on their genes to future generations.
Copyright 2003 Prentice Hall2-3 Biology and Behavior The term behavioral neuroscience describes the work of scientists from several disciplines who work to understand how the nervous system is related to behavior.
Copyright 2003 Prentice Hall2-4 The Nervous System We use the processes of sensing, processing, and responding to interact with the environment. The nervous system is divided into the central nervous system (CNS-brain and spinal cord) and the peripheral nervous system (PNS-all parts of the nervous system outside the CNS), coordinates these three activities.
Copyright 2003 Prentice Hall2-5 The CNS The spinal cord is composed of sensory (afferent or ascending) and motor (efferent or descending) nerves. Interneurons may connect sensory and motor neurons.
Copyright 2003 Prentice Hall2-6 CNS Nerves
Copyright 2003 Prentice Hall2-7 The PNS The PNS is composed of the somatic division and the autonomic division. The somatic division consists of afferent (sensory) nerves that run from the receptors to the brain and efferent (motor) nerves that run to the glands and muscles. The autonomic division consists of the sympathetic division, which mobilizes the body's resources, and the parasympathetic division which returns the body to a normal state of homeastasis.
Copyright 2003 Prentice Hall2-8 Divisions of the Nervous System Central Nervous System –Brain –Spinal cord Peripheral Nervous System –Somatic –Autonomic
Copyright 2003 Prentice Hall2-9 Neurons: The Basic Cells The cells that make up the nervous system are called neurons. Neurons are composed of: –dendrites that receive signals from adjacent neurons –a cell body or soma –an axon that transmits signals –terminal buttons that contain neurotransmitters.
Copyright 2003 Prentice Hall2-10 Structure of a Neuron
Copyright 2003 Prentice Hall2-11 Neurotransmitters Neurotransmitters enable the signal from one neuron to be relayed to other neurons across the synapse, a small gap that separates neurons. A myelin sheath covers the axons of some neurons to increase the speed of transmission of the neural signal.
Copyright 2003 Prentice Hall2-12 The Synapse
Copyright 2003 Prentice Hall2-13 Key Neurotransmitters Acetylcholine (ACh): excitatory or inhibitory Dopamine: inhibitory or excitatory Serotonin: inhibitory or excitatory Endorphins: inhibitory Norepinephrine: Generally excitatory Gamma amino butryic acid (GABA): inhibitory
Copyright 2003 Prentice Hall2-14 Neurotransmitters Among the key neurotransmitters, dopamine has been implicated in the development of Parkinson's disease (low levels) and certain types of schizophrenia (high levels). Acetycholine seems to play a role in Alzheimer's disease (low levels). Serotonin has been implicated In a variety of disorders, including depression and obsessive- compulsive disorder.
Copyright 2003 Prentice Hall2-15 How Neurons Communicate Ions (electrically charged particles) are found on the inside and outside of the neuron's semipermeable cell membrane When a neuron is in a resting state, more negative ions are on the inside of the cell (measured at -70 mV) than on the out side.
Copyright 2003 Prentice Hall2-16 How Neurons Communicate
Copyright 2003 Prentice Hall2-17 How Neurons Communicate Neurotransmitters stimulate the cell membrane to allow ions to enter the neuron resulting in –depolarization (positive ions move inside the neuron resulting in excitation) or –hyperpolarization (additional negative ions move inside resulting in in hibition).
Copyright 2003 Prentice Hall2-18 How Neurons Communicate If depolarization of the dendrite and soma reaches the threshold level (-65 to -60 mV), the axon quickly reverses electrical charge (to about +40 mV), and the signal is transmitted to the next neuron. This reversal in electrical charge known as the action potential.
Copyright 2003 Prentice Hall2-19 The Action Potential
Copyright 2003 Prentice Hall2-20 How Neurons Communicate Neurotransmitters must be removed from the synapse be fore another signal can be transmitted. Removal is accomplished either by destroying the neurotransmitter (breakdown) or by taking it back into the terminal buttons (reuptake).
Copyright 2003 Prentice Hall2-21 Agonists and Antagonists Agonists are drugs that promote the action of a neurotransmitter. Antagonists are drugs that oppose or inhibit the action of a neurotransmitter.
Copyright 2003 Prentice Hall2-22 Agonists and Antagonists
Copyright 2003 Prentice Hall2-23 Agonists and Antagonists
Copyright 2003 Prentice Hall2-24 The Brain: A Closer Look Phrenology is a pseudoscience popularized in the 1800s by Franz Joseph Gall Gall believed we could determine a person's skills and characteristics by identifying bumps on the skull.
Copyright 2003 Prentice Hall2-25
Copyright 2003 Prentice Hall2-26 The Brain: A Closer Look Early studies of brain functioning involved stimulating or removing portions of the cortex. The stereotaxic instrument allowed examination of subcortical structures without damaging the cortex.
Copyright 2003 Prentice Hall2-27 The Brain: A Closer Look The electroencephalograph (EEG) provides an investigator with a chart of a person's brain waves. lmages of the structures of the brain can be produced by computerized techniques such as: –the PET (positron emission tomography), –the CT or CAT (computerized axial tomography), –the MRI (magnetic resonance imaging), –and the fMRl (functional magnetic resonance imaging).
Copyright 2003 Prentice Hall2-28 The Brain The brain is divided into the hindbrain, the midbrain, and the forebrain.
Copyright 2003 Prentice Hall2-29 The Hindbrain The oldest of the three main divisions of the brain. Its major structures are the medulla, pons, and cerebellum.
Copyright 2003 Prentice Hall2-30 The Midbrain A major division of the brain that contains fibers known as the reticular formation.
Copyright 2003 Prentice Hall2-31 The Forebrain A major division of the brain that consists of subcortical structures and the two hemispheres of the cerebral cortex The hemispheres of the cerebral cortex are joined by the corpus collosum
Copyright 2003 Prentice Hall2-32 The Corpus Callosum Millions of myelinated axons connecting the brain’s hemispheres Provides a pathway for communication between the hemispheres If surgically severed for treatment of epilepsy, hemispheres cannot communicate directly
Copyright 2003 Prentice Hall2-33 The Cortex The cerebral cortex covers the forebrain and is divided into four lobes: –frontal, –parietal, –temporal, –and occipital.
Copyright 2003 Prentice Hall2-34 Lobes of the Cerebral Cortex
Copyright 2003 Prentice Hall2-35 Subcortical Structures A group of subcortical structures involved in emotion, memory, eating, drinking, and sexual behavior are located beneath the cortex. These structures include the limbic system, thalamus, and hypothalamus.
Copyright 2003 Prentice Hall2-36 Limbic System
Copyright 2003 Prentice Hall2-37 More About the Brain The brain has been described as plastic, which means it can change over time and recover to some degree even from removal of an entire hemisphere.
Copyright 2003 Prentice Hall2-38 Plasticity in Brain and Behavior Some rats are housed alone in empty cages Their littermate twins are group-housed in cages with toys, which are changed frequently Richer environments led to heavier, thicker brains, more synapses, and better learning
Copyright 2003 Prentice Hall2-39 More About the Brain Studying the human brain yields information about aphasias (language deficits) and apraxias (nonverbal deficits).
Copyright 2003 Prentice Hall2-40 Sperry’s Split-Brain Experiment Split-brain subjects could not name objects shown only to the right hemisphere If asked to select these objects with their left hand, they succeeded The right side of the brain doesn’t control speech
Copyright 2003 Prentice Hall2-41 The Endocrine System The endocrine system affects behavior by producing and secreting hormones, which are chemicals that regulate body functions. Among the major endocrine glands are the pineal gland, hypothalamus pituitary gland, the thyroid gland, the pancreas, the gonads, and the adrenal glands.
Copyright 2003 Prentice Hall2-42 The Endocrine System Endocrine system: –Ductless glands that regulate growth, reproduction, metabolism, mood, and some behavior Hormones: –Chemical messengers secreted into the bloodstream