:: Slide 1 :::: Slide 2 :: :: Slide 3 :::: Slide 4 :: :: Slide 5 :::: Slide 6 :: Left blankYour nervous system is a complex communication network in which signals are constantly being received, integrated, and transmitted. The nervous system handles information, just as the circulatory system handles blood. There are two major types of cells in the nervous system: glia and neurons. Neurons are cells that receive, integrate, and transmit information. In the human nervous system, the vast majority are interneurons – neurons that communicate with other neurons. There are also sensory neurons, which receive signals from outside the nervous system, and motor neurons, which carry messages from the nervous system to the muscles that move the body. The soma, or cell body, contains the cell nucleus and much of the chemical machinery common to most cells. The branched structure is called a dendritic tree, and each individual branch is a dendrite. Dendrites are the parts of a neuron that are specialized to receive information. The long fiber is the axon. Axons are specialized structures that transmit information to other neurons or to muscles or glands.

:: Slide 7 :::: Slide 8 :: :: Slide 9 :::: Slide 10 :: :: Slide 11 :::: Slide 12 :: Most human axons are wrapped in a myelin sheath. Myelin is a white, fatty substance that serves as an insulator around the axon and speeds the transmission of signals. In people suffering from multiple sclerosis, some myelin sheaths degenerate, slowing or preventing nerve transmission to certain muscles. The axon ends in a cluster of terminal buttons, which are small knobs that secrete chemicals called neurotransmitters. These chemicals serve as messengers that may activate neighboring neurons. The points at which neurons interconnect are called synapses. A synapse is a junction where information is transmitted from one neuron to another. Glia come in a variety of forms. Their main function is to support the neurons by, among other things, supplying them with nutrients and removing waste material. In the human brain, there are about ten glia cells for every neuron. The neuron at rest is a tiny battery, a store of potential energy. Inside and outside the axon are fluids containing electrically charged atoms and molecules called ions. Positively charged sodium and potassium ions and negatively charged chloride ions are the principal molecules involved in the nerve impulse. When the neuron is not conducting an impulse, it is said to be in a resting state. The cell membrane is polarized–negatively charged on the inside and positively charged on the outside. The charge difference across the membrane can be measured with a pair of microelectrodes connected to an oscilloscope. In a resting neuron, this difference, called the resting potential, is about –70 millivolts. Click to play animation. Make sure volume is turned up.

:: Slide 13 :::: Slide 14 :: :: Slide 15 :::: Slide 16 :: :: Slide 17 :::: Slide 18 :: When the neuron is stimulated, channels in its cell membrane open, briefly allowing positively charged ions to rush in. For an instant, the neuron’s charge is less negative, or even positive, creating an action potential. An action potential is a very brief shift in the neuron’s electrical charge that travels along an axon. Click to play animation. Make sure volume is turned up. The size of an action potential is not affected by the strength of the stimulus – a weaker stimulus does not produce a weaker action potential. If the neuron receives a stimulus of sufficient strength, it fires, but if it receives a weaker stimulus, it doesn’t. This is referred to as the “all-or-none law.” The neural impulse is a signal that must be transmitted from a neuron to other cells. This transmission takes place at special junctions called synapses, where terminal buttons release chemical messengers. The two neurons are separated by the synaptic cleft, a microscopic gap between the terminal button of one neuron and the cell membrane of another neuron. Signals have to cross this gap for neurons to communicate. The neuron that sends a signal across the gap is called the presynaptic neuron. Click to continue. The neuron that receives the signal is called the postsynaptic neuron. Neurotransmitters are chemicals that transmit information from one neuron to another. Within the buttons, most of these chemicals are stored in small sacs, called synaptic vesicles.

:: Slide 19 :::: Slide 20 :: :: Slide 21 :::: Slide 22 :: :: Slide 23 :::: Slide 24 :: The neurotransmitters are released when a vesicle fuses with the membrane of the presynaptic cell and its contents spill into the synaptic cleft. After their release, neurotransmitters diffuse across the synaptic cleft to the membrane of the receiving cell. When a neurotransmitter and a receptor molecule combine, reactions in the cell membrane cause a postsynaptic potential, or PSP – a voltage change at the receptor site on a postsynaptic cell membrane. After producing postsynaptic potentials, some neurotransmitters either become inactivated by enzymes, or drift away. Most neurotransmitters, however, are reabsorbed into the presynaptic neuron through reuptake – a process in which neurotransmitters are sponged up from the synaptic cleft by the presynaptic membrane. Most neurons are interlinked in complex chains, pathways, circuits, and networks. Our perceptions, thoughts, and actions depend on patterns of neural activity in elaborate neural networks. Click to see a video that shows how neural networks work. Specific neurotransmitters work at specific kinds of synapses – the study of which has led to interesting findings about how specific neurotransmitters regulate behavior. One example is acetylcholine, which is released by motor neurons controlling skeletal muscles, and contributes to the regulation of attention, arousal, and memory. An inadequate supply of acetylcholine is associated with the memory losses seen in Alzheimer’s patients. Here are a few other examples of neurotransmitters, and how their dysregulation is associated with certain disorders. The multitudes of neurons in your nervous system have to work together to keep information flowing effectively. The peripheral nervous system is made up of all the nerves that lie outside the brain and spinal cord. Nerves are bundles of neuron fibers – or axons – that are routed together in the peripheral nervous system.

:: Slide 25 :::: Slide 26 :: :: Slide 27 :::: Slide 28 :: :: Slide 29 :::: Slide 30 :: The peripheral nervous system can be divided into two parts. The somatic nervous system is made up of nerves that connect to voluntary skeletal muscles and sensory receptors. They carry information from receipts in the skin, muscles, and joints to the CNS, and from the CNS to the muscles. The autonomic nervous system is made up of nerves that connect to the heart, blood vessels, smooth muscles, and glands. It controls automatic, involuntary, visceral functions that people don’t normally think about, such as heart rate, digestions, and perspiration. When a person is autonomically aroused, automatic functions speed up. This speeding up is controlled by the sympathetic division of the autonomic nervous system – the sympathetic nervous system mobilizes the body’s resources for emergencies and creates the fight-or-flight response. The parasympathetic nervous system, on the other hand, conserves bodily resources to save and store energy. The central nervous system, or CNS, consists of the brain and spinal cord. It is protected by enclosing sheaths called meninges, as well as cerebrospinal fluid, which nourishes the brain and provides a protective cushion for it. The spinal cord houses bundles of axons that carry the brain’s commands to peripheral. Neuroscientists use many specialized techniques to investigate connections between the brain and behavior. Lesioning involves the destruction of a piece of the brain in order to observe what happens. Electrical stimulation of the brain sends a weak electric current into the brain to stimulate it. Brain imaging devices allow neuroscientists to look inside the human brain, such as in a CT (computerized tomography or MRI (magnetic resonance imaging) scan. Another new research tool in neuroscience is transcranial magnetic stimulation, which allows scientists to temporarily enhance or depress activity in a specific area of the brain. This news video shows an example of how TMS may impact patients with depression.

:: Slide 31 :::: Slide 32 :: :: Slide 33 :::: Slide 34 :: :: Slide 35 :::: Slide 36 :: The hindbrain includes the cerebellum and two structures found in the lower part of the brainstem: the medulla and the pons. The cerebellum is critical to the coordination of movement and to the sense of equilibrium, or physical balance. Damage to the cerebellum disrupts fine motor skills, such as those involved in writing or typing. The pons contains several clusters of cell bodies that contribute to the regulation of sleep and arousal. The medulla, which attaches to the spinal cord, has charge of largely unconscious but essential functions, such as regulating breathing, maintaining muscle tone, and regulating circulation. The midbrain is concerned with certain sensory processes, such as locating where things are in space. The midbrain is the origin of an important system of dopamine-releasing axons. Among other things, this dopamine system is involved in the performance of voluntary movements. The abnormal movements associated with Parkinson’s disease are due to the degeneration of neurons in this area. Running through both the hindbrain and the midbrain is the reticular formation. Lying at the central core of the brainstem, the reticular formation contributes to the modulation of muscle reflexes, breathing, and the perception of pain. It is best known, however, for its role in the regulation of sleep and wakefulness. Activity in the ascending fibers of the reticular formation is essential to maintaining an alert brain. The forebrain is the largest and most complex region of the brain, encompassing a variety of structures, including the thalamus, hypothalamus, limbic system, and cerebrum. The thalamus is a structure in the forebrain through which all sensory information, except smell, must pass to get to the cerebral cortex. This way station is made up of a number of clusters of cell bodies, or nuclei. Each cluster is concerned with relaying sensory information to a particular part of the cortex. The hypothalamus is made up of a number of distinct nuclei. These nuclei regulate a variety of basic biological drives, including the so-called “four Fs” – fighting, fleeing, feeding, and mating. The limbic system is a loosely connected network of structures involved in emotion, motivation, memory, and other aspects of behavior.

:: Slide 37 :::: Slide 38 :: :: Slide 39 :::: Slide 40 :: :: Slide 41 :::: Slide 42 :: The cerebrum is the largest and most complex part of the human brain. It includes the brain areas that are responsible for our most complex mental activities, including learning, remembering, thinking, and consciousness itself. The cerebrum is divided into right and left halves, called cerebral hemispheres. If we pry apart the two halves of the brain, we see that this fissure descends to a structure called the corpus callosum. Each cerebral hemisphere is divided by deep fissures into four parts called lobes. To some extent, each of these lobes is dedicated to specific purposes. The occipital lobe includes the cortical area where most visual signals are sent and visual processing is begun – the primary visual cortex. The parietal lobe includes the area that registers the sense of touch – the primary somatosensory cortex. The temporal lobe contains an area devoted to auditory processing, the primary auditory cortex. In recent decades, an exciting flurry of research has focused on cerebral lateralization – the degree to which the left or right hemisphere handles various cognitive and behavioral functions. However, hints of cerebral specialization were found as early as the late 1800s. In 1861, Paul Broca, a French surgeon, performed an autopsy on a patient who had been unable to speak. The autopsy revealed a lesion on the left side of the man’s frontal lobe. Since then, many similar cases have shown that this area of the brain – which came to be known as Broca’s area – plays an important role in the production of speech. In 1874, Paul Wernicke discovered that damage to a portion of the temporal lobe of the left hemisphere leads to problems with the comprehension of language. Patients with damage in Wernicke’s area can speak normally but have difficulty understanding others. Each hemisphere’s primary sensory and motor connections are to the opposite side of the body – the left hemisphere controls and communicates with the right hand, arm, etc. and the right hemisphere controls and communicates with the left side. Vision is more complex. Stimuli in the right half of the visual field are registered by receptors on the left side of each eye that send signals to the left hemisphere. Similarly, stimuli in the left half of the visual field are registered by receptors on the right side of each eye that send signals to the right hemisphere. Roger Sperry and his colleagues found that the ability of split-brain subjects to name and describe objects depended on which side of the visual field the image was flashed in. When pictures of common objects were flashed in the right visual field and thus sent to the left hemisphere, the split-brain subjects were able to name and describe the objects depicted.

:: Slide 43 :::: Slide 44 :: :: Slide 45 :::: Slide 46 :: :: Slide 47 :::: Slide 48 :: In another experimental procedure, split-brain subjects were asked to reach under a screen to hold various objects. When objects were placed in the split-brain subjects’ right hand, which communicates most directly with the left hemisphere, the subjects had no problem naming the objects. When the objects were placed in the subjects’ left hand, which communicates most directly with the right hemisphere, the subjects had difficulty naming the objects. Research with split-brain subjects provided the first compelling evidence that the right hemisphere has its own special talents. Based on this research, investigators concluded that the left hemisphere usually handles verbal processing, whereas the right hemisphere usually handles nonverbal processing, such as that required by visual-spatial and musical tasks. Eventually, researchers wondered whether it was safe to generalize from split- brain subjects to normal individuals whose corpus callosum was intact. One method of studying cerebral specialization in an intact brain is by looking at perceptual asymmetries – left-right imbalances between the cerebral hemispheres in the speed of visual or auditory processing. Subtle differences in the abilities of the two hemispheres can be detected by precisely measuring how long it takes participants to recognize different types of stimuli. The endocrine system consists of glands that secrete chemicals – known as hormones – into the bloodstream that help control bodily functioning. Some hormones are released in response to changing conditions in the body and act to regulate those conditions. Hormones are secreted by the endocrine glands in a pulsatile manner – that is, several times per day in brief bursts or pulses. The levels of many hormones increase to a certain level, then signals are sent to the hypothalamus or other endocrine glands to stop secretion of that hormone – a negative feedback system. Much of the endocrine system is controlled by the nervous system through the hypothalamus, which also connects with the pituitary gland. The pituitary gland stimulates actions in the other endocrine glands. For example, in the fight or flight response, the hypothalamus sends signals through the pituitary gland and autonomic nervous system to the adrenal glands, which then secrete stress hormones.

:: Slide 49 :::: Slide 50 :: :: Slide 51 :::: Slide XX :: Every cell in your body contains information from your parents, found on the chromosomes that lie within the nucleus of each cell. Each chromosome contains thousands of genes, which also occur in pairs. Sometimes a member of a pair has a louder voice, always expressing itself and masking the other member of the pair – this is a dominant gene. A recessive gene is one that is masked when the paired genes are different. When a person has two genes in a specific pair that are the same, the person is homozygous for that trait. If the genes are different, they are heterozygous. Family studies, twin studies, and adoption studies are assess the impact of heredity on behavior. Family studies and twin studies focus on genetic relatedness and how it affects various traits in order to study the influence of nature on behavior. Adoption studies are able to assess the influences of both nature and nurture, as adopted children’s traits can be evaluated in relation to both their biological and adoptive parents. The field of evolutionary psychology is based on the work of Charles Darwin and the ideas of natural selection and reproductive fitness. Evolutionary theorists study adaptations, or inherited characteristics, that increase in a population because they help solve a problem of survival or reproduction during the time they emerge. Left blank