Body control systems. Let s start at the top: the human brain. The Cerebrum. The human brain. What parts of your brain are you using right now?

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1 What parts of your brain are you using right now? Body control systems Quick Sends message directly to target organ Endocrine system Frontal lobe Parietal lobe Movement and conscious thought; Frontal speech Nervous system Moto rco rte x Somato se ns ory co rte x Speech Somatosensory Reading Sends a hormone as a messenger to the target organ Can target several organs Slower acting Longer lasting response Senses and taste; reading Taste Speech Smell Work together to regulate body activities Hearing Auditory Hearing and smell Temporal lobe Visual Vision Vision Occipital lobe Figure Let s start at the top: the human brain What parts of the brain are active in reading and speaking? primary auditory cortex primary motor cortex visual cortex Wernicke s 1. The word is seen in 2. Information about the visual cortex. the word is interpreted; the word is understood Broca s 3. Governs the formation of words. 4. Information is transferred to the primary motor. The brain processes and acts on information It receives information from nerves and the spinal cord, integrates it and generates the appropriate response. PET (positron-emission tomography) scan of the brain Yellow and red indicate the most active s Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The human brain The Cerebrum Cerebrum largest part of the brain Central processing center where learning, remembering and reasoning takes place The cerebral cortex a highly folded layer of tissue that forms the surface of the cerebrum Cerebrum The cerebrum consists of right and left cerebral hemispheres Are you left-brained or rightbrained? Right = artistry? Left = logic? Little about life is that clear and distinct. The traits associated with each side of the brain are matters of degree

2 The brain: Cerebellum Coordinates basic movements: Maintains posture and balance Learns and remembers new motor skills (tying a shoe, playing the piano or hitting a baseball) Proprioception Knowing where the body is in space The brain stem Connects the brain to the spinal cord Controls automatic functions: Breathing Heart rate Blood pressure Brain stem The Central Nervous System The central nervous system (CNS) brain spinal cord What protects the CNS? Bone and protective membranes called the meninges The meninges are a series of 3 tissue coverings between the nervous tissue and bone Spaces filled with cerebrospinal fluid Liquid shock absorber Cerebrospinal fluid provides a constant environment Blood-brain barrier Supplies nutrients to the central nervous system (CNS) Collects waste products Cushions the brain Prevents the fragile surface of the brain from striking the skull astrocyte Separates the circulating blood from the brain extracellular fluid Tight junctions around the capillaries restrict the entry of bacteria and large molecules into the cerebrospinal fluid Protects the brain from bacterial and viral infections Glucose is actively transported across the barrier

3 Spinal cord relays information Neurons are unique types of cells Superhighway for nerve impulses traveling between the brain and rest of body nerves Direction of Movement Can be many feet in length! Conduct electrical signals Dendrites, Cell Body, Axon Vertebra protect the spinal cord Types of s Sensory receptor SENSORY INPUT Sensory MOTOR OUTPUT INTEGRATION Inter Neurons are not the only kind of cells Neuroglia Cells that support and nourish s Outnumber s 9 to 1 Effector cells Motor Peripheral nervous system (PNS) Brain and spinal cord Central nervous system (CNS) Myelin sheath Insulates axons Covering formed by a type of neuroglia called Schwann cells Cells wrap themselves around the axon several times What happens if the myelin sheath is damaged? Nerves no longer conduct impulses normally Multiple sclerosis Inflammatory disease that destroys the myelin sheath MS short circuits the nervous system

4 Nerves Organization of Nervous System Cables or bundles of axons Extend from the CNS to various parts of the body. What is the longest nerve in your body? Two main divisions: The central nervous system (CNS) Peripheral Nervous System: sensory and motor nerves brain and spinal cord The peripheral nervous system (PNS) nerves that carry signals into and out of the CNS PNS: motor nerves Sensory nerves bring info from the body to the CNS Some motor s take signals to skeletal muscles Conscious Impulses to Muscles Somatic nervous system PNS: motor nerves direction Others serve muscles and glands Structure of a motor Dendrites Cell body But not skeletal muscle Controls automatic functions of the body s internal organs Direction of electrical signal: Dendrite cell body axon Axon Involuntary Supporting cell pathway terminals Nucleus Myelin sheath Autonomic Nervous System Forms insulating material around an axon Increases the speed of the electrical signa l

5 direction Neurons work by carrying electrical signals An axon ends in a cluster of branches, each with a bulb-like synaptic terminal that relays signals to Dendrites Cell body Axon Supporting cell Another A muscle or other effector pathway terminals Neurons are specialized for carrying electrical signals from one part of the body to another axon cell body Nucleus dendrites Myelin sheath Figure 27.2 The electrical signals are called action potentials An action potential is a brief change in electrical conditions at a s membrane Action potentials spread down the axon axon When a fires, the charge across the s membrane suddenly reverses polarity Action potentials are all or nothing events cell body dendrites is propagated down the axon like an electrical current down a wire How is the action potential passed to the next cell? Electrical signals can t cross the gap between two s or synapse The signal is transmitted by chemicals called terminal of sending SYNAPSE Sending Action potential arrives. Vesicles terminal Receptor Ions neurotransmitters Dendrite of receiving Vesicle fuses with plasma membrane. Stored in vesicles at the end of the axon is released into synaptic cleft. cleft Receiving Ion channels molecules binds to receptor. Ion channel opens and triggers or inhibits a new action potential. Neurons and how they work 4:43 Ion channel closes. is broken down and released.

6 Dendrites Myelin sheath Receiving cell body Axon terminals Neurons integrate many signals Control of muscle contraction nerve impulse to a muscle fiber ACh is released, diffuses across the synapse and binds to receptors on muscle cell Muscle fiber contracts SEM A may receive input from hundreds of other s via thousands of synaptic terminals Motor s carry How do drugs work? Alcohol affects several neurotransmitters Many affect the levels of neurotransmitters. Mimic the action of a neurotransmitter Block its receptor Interfere with removal of a neurotransmitter from the synapse Your brain on alcohol Alcohol is a depressant Changes brain function at the synapse Increases the release of GABA, an inhibitor slower response time Decreases glutamate uncoordination, slurred speech, and memory disruption Cocaine Blocks reabsorption of dopamine at the synapse Dopamine remains in the synapse longer and continues to stimulate the postsynaptic cell. The user experiences a rush sensation

7 Methamphetamine Marijuana A synthetic drug made by adding a methyl group to amphetamine Its structure is similar to dopamine Increases stimulation of the postsynaptic effect like that of cocaine anandamide How do drugs work? Anandamide receptor Alzheimer s disease Most common form of dementia Neurodegeneration Entire brain regions are demolished Destroys memory and thinking skills Metabolic function of the brain PET scan noninvasive test of brain function using FDG tracers to measure metabolic activity Note the decrease in metabolic function in Alzheimer's patient Plaque marker Healthy THC binds to a receptor for the neurotransmitter anandamide feeling of peaceful contentment, mild euphoria Alzheimer's PET scan using labeled PiB protein marker to light up amyloid plaques High levels of plaque are seen in an Alzheimer s patient But some healthy people also have high levels of plaque