The Brain and Behavior PDF

THE BRAIN AND BEHAVIOR It is only fairly recently in human history that people have come to understand the actual location of the mind. Hippocrates and later Rene Descartes and Aristotle Plato...

THE BRAIN AND BEHAVIOR It is only fairly recently in human history that people have come to understand the actual location of the mind. Hippocrates and later Rene Descartes and Aristotle Plato Leonardo da Vinci taught that our thoughts and suggested that the brain was introduced theories about feelings arose from the where the mind resides and how the nervous system heart. that it served as the source operated of all thought and action. While these early theories were later proven wrong, they did establish the important idea that external stimulation could lead to muscle responses. Descartes introduced reflexes 2 Dualism The idea that the mind and the body are two separate entities. Rene Descartes famously theorized that the mind and body were separate Thus, the central claim of what is called Cartesian dualism is that the mind and the body are two separate substances that interact. 3 Phrenology One early attempt at understanding this led to the development of a pseudoscience known as phrenology. Certain human faculties could be linked to bumps and indentations of the brain, which could be felt on the surface of the skull. Soon dismissed by other scientists. However, the idea that certain parts of the brain were responsible for specific functions played an important role in the development of future brain research. 4 Phineas Gage A railroad worker who suffered a devastating brain injury also influenced our understanding of how damage to certain parts of the brain could impact behavior and functioning. His mind was radically changed, so decidedly that his friends and acquaintances said he was "no longer Gage.” 5 Neuroscience Also known as Neural Science, is the study of how the nervous system develops, its structure, and what it does. Neuroscientists focus on the brain and its impact on behavior and cognitive functions. The key interests of psychological study—are intimately intertwined with activity in the brain. Studying damaged brains is one of the most useful ways to increase our understanding of the links between the brain and behavior. 6 Broca’sArea Damage to a part of the brain called Broca’s area causes patients to lose the ability to speak; knowing this, we can infer that that part of the brain is in some way related to language production. This gives us more information about neuroanatomy and also about the influence the brain has on behavior. 7 NERVOUS SYSTEM PARTS OF THE NERVOUS SYSTEM. The Central Nervous System The central nervous system (CNS) comprises the brain and spinal cord. 9 Brain The brain is the most complex and sensitive organ in the body. It is responsible for all body functions, including serving as the coordinating center for all sensations, mobility, emotions, and intellect. Protection for the brain is provided by the bones of the skull, which in turn are covered by the scalp. 10 Scalp The scalp is composed of an outer layer of skin, which is loosely attached to the APONEUROSIS, a flat, broad tendon layer that anchors the superficial layers of the skin. The PERIOSTEUM, below the aponeurosis, firmly encases the bones of the skull and provides protection, nutrition to the bone, and the capacity for bone repair. It is the membrane of blood vessels and nerves that wraps around most of your bones 11 Meninges Meninges are three layers of membranes that cover and protect your brain and spinal cord (your central nervous system [CNS]). 12 Meninges The meningeal layer closest to the bones of the skull is called the DURA MATER (literally meaning tough mother). Below the dura mater lies the ARACHNOID MATER (literally spider-like mother). The innermost meningeal layer is a delicate membrane called the PIA MATER (literally tender mother). The pia mater firmly adheres to the convoluted surface of the brain. 13 Meninges Between the arachnoid mater and pia mater is the SUBARACHNOID SPACE. The subarachnoid space within this region is filled with CEREBROSPINAL FLUID (CSF). The CSF serves to deliver nutrients and remove waste from neural tissues. 14 Blood Brain Barrier The blood vessels that supply the brain with nutrients and other chemical substances lie on top of the pia mater. The capillaries associated with these blood vessels in the brain are less permeable than those in different locations in the body. The capillary ENDOTHELIAL CELLS form tight junctions that control the transfer of blood components to the brain. This phenomenon is referred to as the blood-brain barrier. 15 Blood Brain Barrier The blood-brain barrier protects the cerebrospinal fluid from contamination, and can be quite effective at excluding potential microbial pathogens. As a consequence of these defenses, there is no normal microbiota in the cerebrospinal fluid. The blood-brain barrier also inhibits the movement of many drugs into the brain, particularly compounds that are not lipid soluble. 16 Meningitis Meningitis is an inflammation (swelling) of the protective membranes covering the brain and spinal cord. A bacterial or viral infection of the fluid surrounding the brain and spinal cord usually causes the swelling. Even with early diagnosis and adequate treatment, 5% to 10% of patients die, typically within 24 to 48 hours after the onset of symptoms. Bacterial meningitis may result in brain damage, hearing loss or a learning disability in 10% to 20% of survivors. 17 Spinal Cord The spinal cord is the tube-like structure that runs from your brain to your lower back. The three primary roles of the spinal cord are to send motor commands from the brain to the body, send sensory information from the body to the brain, and coordinate reflexes. The spinal cord also has protective structures similar to those surrounding the brain. Within the bones of the vertebrae are meninges of dura mater (sometimes called the dural sheath), arachnoid mater, pia mater, and a blood-spinal cord barrier that controls the transfer of blood components from blood vessels associated with the spinal cord. 18 The Peripheral Nervous System The PNS is formed of the nerves that connect the body's organs, limbs, and other anatomic structures to the brain and spinal cord. 19 Peripheral Nervous System Unlike the brain and spinal cord, the PNS is not protected by bone, meninges, or a blood barrier; consequently, the nerves of the PNS are much MORE SUSCEPTIBLE TO INJURY AND INFECTION. 20 Peripheral Nervous System Microbial damage to peripheral nerves can lead to tingling or numbness, known as neuropathy. These symptoms can also be produced by trauma and noninfectious causes such as drugs or chronic diseases like diabetes. 21  THE CELLS OF THE NERVOUS SYSTEM BASIC UNITS OF THE NERVOUS SYSTEM. The Cells of the Nervous System Tissues of the PNS and CNS are formed of cells called GLIAL CELLS (neuroglial cells) and NEURONS (nerve cells). 23 GLIAL CELLS Astrocytes The most common type of glial cell in the CNS is the astrocyte or astroglia. The "astro" part of the name is because the cells have projections that make them look star-shaped. 24 GLIAL CELLS Astrocytes Forming the blood-brain barrier (BBB): It only lets in substances that are supposed to be in your brain while keeping out things that could be harmful. Regulating neurotransmitters: Neurons communicate using chemical messengers called neurotransmitters. Once the message is delivered, neurotransmitters hang around until an astrocyte recycles them. Cleaning up: Astrocytes also clean up what's left behind when a neuron dies, as well as excess potassium ions. Regulating blood flow to the brain. An active region gets more blood than an inactive one. Synchronizing the activity of axons: Axons are long, thread-like parts of neurons and nerve cells that conduct electricity to send messages between cells. Brain energy metabolism and homeostasis: One of the most important roles of astrocytes is to regulate metabolism in the brain by storing sugar (glucose) from the blood and providing it as fuel for neurons. 25 GLIAL CELLS Oligodendrocytes Oligodendrocytes come from neural stem cells. The word is made up of a few Greek terms that mean "cells with several branches.“ The primary purpose of oligodendrocytes is to help information move faster along axons in the brain. Oligodendrocytes look like spikey balls. On the tips of their spikes are white, shiny membranes that wrap around the axons of nerve cells and form a protective layer, like the plastic insulation on electrical wires. This protective layer is called the myelin sheath. 26 GLIAL CELLS Microglia Microglia are tiny glial cells ("micro" means small). They act as the brain's own dedicated immune system. The brain needs its own immune system because the blood-brain barrier isolates the brain from the rest of your body. Microglia are alert to signs of injury and disease. When they detect a problem, they charge in and take care of it—whether it means clearing away dead cells or getting rid of a toxin or pathogen. When microglia respond to an injury, it causes inflammation as part of the healing process. 27 GLIAL CELLS Ependymal Cells Ependymal cells make up the thin membrane lining the central canal of the spinal cord and the passageways (ventricles) of the brain (ependyma). They also make cerebrospinal fluid and have an important role in the blood-brain barrier. Ependymal cells are very small and line up tightly to form the membrane. Inside the ventricles, they have little hairlike projections (cilia) that wave back and forth to keep the cerebrospinal fluid circulating. 28 GLIAL CELLS Radial Glia Radial glia is believed to be a type of stem cell. This type of cell can create other cells. In the developing brain, stem cells are the "parents" of neurons, astrocytes, and oligodendrocytes. When you were an embryo, these cells also provided the "scaffolding" for developing neurons. They provide the long fibers that guide young brain cells into place as your brain forms. Later in life, these cells contribute to your brain's ability to change and adapt (neuroplasticity). 29 GLIAL CELLS Radial Glia Radial glia is believed to be a type of stem cell. This type of cell can create other cells. In the developing brain, stem cells are the "parents" of neurons, astrocytes, and oligodendrocytes. When you were an embryo, these cells also provided the "scaffolding" for developing neurons. They provide the long fibers that guide young brain cells into place as your brain forms. Later in life, these cells contribute to your brain's ability to change and adapt (neuroplasticity). 30 GLIAL CELLS Schwann Cells Schwann cells are named for Theodor Schwann, the physiologist who discovered them. They function a lot like oligodendrocytes by providing myelin sheaths for axons. However, Schwann cells are found in the peripheral nervous system (PNS) rather than the CNS. Instead of being a central cell with membrane-tipped arms, Schwann cells form spirals directly around the axon. The nodes of Ranvier sit between them, just as they do with oligodendrocytes, and assist in nerve transmission in the same way. Schwann cells are also part of the PNS's immune system. When a nerve cell is damaged, it can "eat" the nerve's axons and provide a protected path for a new axon to form. 31 GLIAL CELLS Satellite Cells Satellite cells get their name from the way they surround certain neurons, with several "satellites" forming a sheath around the cellular surface. We're just beginning to learn about satellite cells but many researchers believe they're similar to astrocytes. However, they're found in the PNS, not the CNS. Satellite cells' main purpose appears to be regulating the environment around the neurons, keeping chemicals in balance. 32 Neurons A neuron is the basic unit of the nervous system. The signals between the brain and the other parts of the body comprising internal organs are mediated by the neurons which make up the nervous system. Neurons are specialized cells found throughout the nervous system that transmit signals through the nervous system using electrochemical processes. 33 Neurons The cell body (or soma) is the metabolic center of the neuron and contains the nucleus and most of the cell’s organelles. The many finely branched extensions from the soma are called dendrites. The soma also produces an elongated extension, called the axon, which is responsible for the transmission of electrochemical signals through elaborate ion transport processes. Axons of some types of neurons can extend up to one meter in length in the human body. 34 Neurons To facilitate electrochemical signal transmission, some neurons have a myelin sheath surrounding the axon. Myelin, formed from the cell membranes of glial cells like the Schwann cells in the PNS and oligodendrocytes in the CNS, surrounds and insulates the axon, significantly increasing the speed of electrochemical signal transmission along the axon. The end of an axon forms numerous branches that end in bulbs called synaptic terminals. 35 Synapses Neurons form junctions with other cells, such as another neuron, with which they exchange signals. The junctions, which are actually gaps between neurons, are referred to as synapses. At each synapse, there is a presynaptic neuron and a postsynaptic neuron (or other cell). 36 Synapses The synaptic terminals contain vesicles filled with chemicals called neurotransmitters. When the electrochemical signal moving down the axon reaches the synapse, the vesicles fuse with the membrane, and neurotransmitters are released, which diffuse across the synapse and bind to receptors on the membrane of the postsynaptic cell, potentially initiating a response in that cell. That response in the postsynaptic cell might include further propagation of an electrochemical signal to transmit information or contraction of a muscle fiber. 37 Next Topic Sensation 38