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Stephanie Bobbitt Chapter 48) Nervous Systems p. 1040-1053 - Vertebrate Nervous Systems o Vertebrate nervous systems have central and peripheral components have distinct central and peripheral elements and lots of cephalization CNS: brain (integrative power) + spinal cord (integrates simple responses and transmits info to and from brain PNS: transmits info to and from cns and regulates internal environment cns derived from embryo’s hollow nerve cord – brain and spinal cord have fluid filled spaces central canal: part of spinal cord that is continuous with brain ventricles: spaces full of cerebrospinal fluid: formed in brain by blood filtration, conveys nutrients, hormones, and wbcs across blood-brain barrier, also a shock absorbed meninges: connective tissues protecting the brain and spinal cord white matter: bundles of axons with myelin sheath gray matter: dendrites, unmyelinated axons, and nerve-cell bodies (nuclei) o The divisions of the peripheral nervous system interact in maintaining homeostasis cranial nerves: made in brain; innervate organs in upper body; have motor and sensory neurons spinal nerves: made in spinal cord; innervate entire body; have motor and sensory neurons sensory division: sensory or afferent neurons that communicate info to CNS from sensory receptors; motor division: motor or efferent neurons that communicate signals from CNS to effector cells somatic nervous system: carries signals to skeletal muscles in response to external stimuli; more voluntary autonomic nervous system: carries signals that regulate internal environment; control smooth and cardiac muscles and organs; more involuntary sympathetic division: arousal and energy generation (faster heartbeat, liver changes glycogen to glucose, bronchi dilate, digestion inhibited, adrenaline secreted) parasympathetic division: calming and return to self-maintenance drop in temperature = hypothalamus signals ANS to constrict blood vessels to lose less heat and SNS to cause shivering o Embryonic development of the vertebrate brain reflects its evolution from three anterior bulges of the neural tube forebrain, midbrain, and hindbrain are obvious when the neural tube differentiates more dividedness = more complex integration possible cerebrum: center of homeostatic control and integration; from forebrain later in development – telencephalon and diencephalon from forebrain, mesencephalon from midbrain, and metencephalon and myelencephalon from hindbrain quick growth of telencephalon makes to halves of cerebrum – left and right cerebral hemispheres; has white matter, internal gray matter, and outer gray matter (cerebral cortex) thalamus, epithalamus, and hypothalamus develop from diencephalon brainstem from mesencephalon (midbrain), metencephalon (pons; also cerebellum), and myelencephalon (medulla oblongata) o Evolutionary older structures of the vertebrate brain regulate essential automatic and integrative functions The Brainstem brainstem function: homeostasis, movement coordination, conduction of information The Medulla and Pons o brainstem centers have nerve cell bodies that send axons to cerebral cortex and cerebellum, releasing neurotransmitters (norepinephrine, dopamine, serotonin, acetylcholine) – cause attention, alertness, appetite, and motivation changes o medulla oblongata: aka medulla; has centers for visceral (automatic) functions (breathing, swallowing, digestion, etc.) o pons: similar activities as medulla; ex: have nuclei to regulate medulla breathing centers o other functions: data conduction (for complex movements like walking); axons carry instructions from midbrain and forebrain to spinal cord by crossing from one CNS side to the other while passing through medulla The Midbrain o midbrain: has sensory receipt and integration centers; sends sensory info along neurons to forebrain parts o midbrain nuclei are inferior and superior colliculi (part of auditory and visual systems) The Reticular System, Arousal, and Sleep arousal: state of awareness of external world; counterpart is sleep reticular formation: system of neurons pass through brain stem core reticular activating system (RAS): regulates sleep and arousal; chooses which info reaches cerebral cortex – more received = more alert brain stem can regulate sleep and wakefulness; serotonin may be neurotransmitter of sleepproduction centers; drinking milk induces sleep since it has tryptophan (makes serotonin) electroencephalogram (EEG): records electrical activity in brain less mental activity usually means more synchronous brain waves sleep may be involved in consolidation of learning and memory The Cerebellum cerebellum: coordination and error checking; probably involved in learning and remembering motor responses receives sensory info about joint position and muscle length, auditory and visual systems receives motor info and provides automatic coordination (ex: hand-eye coordination) The Thalamus and Hypothalamus epithalamus: has choroids plexus (capillary cluster that makes cerebrospinal fluid) and pineal gland (has endocrine function) thalamus: main sensory input center for cerebrum and output for motor info hypothalamus: very important for homeostatic regulation; source of posterior pituitary hormones and hormones acting on anterior pituitary; has body thermostat hypothalamic nuclei: sexual and mating behaviors, fight-or-flight response, pleasure The Hypothalamus and Circadian Rhythms o biological clock: component of circadian rhythms o suprachiasmatic nuclei (SCN): in mammal’s hypothalamus; acts as biological clock o external sues for circadian rhythms, like light; ex: when squirrel is only in light or darkness, their internal clock’s timing is different than normal, so external cues are used to adjust their rhythms to be 24 hours The cerebrum is the most highly evolved structure of the mammalian brain cerebrum is divided into cerebral hemispheres basal nuclei: in white matter of cerebrum; centers for planning and learning movements cerebral cortex (gray matter): has neocortex (only in mammals; 6 sheets of neurons) bigger surface area of neocortex and size of cerebral cortex = greater cognitive abilities and more sophisticated movements left side of brain control right side of body, vice versa corpus callosum: band of fibers (white matter); communicates b/t right and left hemispheres cognition: process of knowing (awareness and judgment); cognitive brain functions: learning, decision making, consciousness, sensory awareness of surroundings Regions of the cerebrum are specialized for different functions four lobes of cerebral cortex: frontal, temporal, occipital, and parietal primary motor cortex and primary somatosensory cortex are boundary b/t frontal and parietal; motor = sends commands to skeletal muscles; somatosensory = receives and partially integrates signals from touch, pain, pressure, temperature receptors Integrative Function of the Association Areas o o sensory info enters cortex via thalamus goes to primary sensory areas in lobes (visual occipital, auditory temporal, somatosensory parietal, olfactory info inferior region of frontal) sent to association areas to be integrated bigger neocoretx = bigger association area Lateralization of Brain Function left hemisphere = language, math, logic, serial sequences of info, detail, speed-optimized activities, etc.; right hemisphere = pattern and face recognition, spatial relations, nonverbal ideation, emotional processing Language and Speech understand language, but not speak = frontal lobe damage (Broca’s area) o read a word out loud = instruction activates visual cortex and Broca’s area, frontal and temporal activated to attach meaning to words Emotion limbic system: hippocampus + olfactory cortex + inner cortex’s lobes + some hypothalamus and thalamus = ring around brain stem; generates emotions by interacting with sensory areas of neocortex and other centers limbic system responsible for infant nurturing, emotional bonding b/t individuals, laughing, crying, attaches feelings to brain stem’s feeding, aggression, and sexuality amygdala: nucleus in temporal lobe; recognizes emotion of facial expressions and lays down emotional memories hippocampus: important to emotional memory system Memory and Learning short-term memory: frontal lobes long-term memory: hippocampus and limbic system transfer from short-term to long-term = rehearsal, positive/negative emotional states mediated by amygdala, and associating new data with previous data (ex: easier to learn new card game if you have played other card games) areas of cerebral cortex store and retrieve words and images from mental dictionary memorization requires rapid changes in strength of nerve connections long-term depression (LTD): postsynaptic cell’s decreased responsiveness to action potential long-term potentiation(LTP): enhanced responsiveness to action potentials; associated with release of neurotransmitter glutamate (binds with receptors to open gated channels that let in a lot of calcium, which triggers more enzyme activity Human Consciousness more studies have been done about consciousness, may require understanding whole-brain activity patterns Research on neuron development and neural stem cells may lead to new approaches for treating CNS injuries and diseases CNS cannot repair itself when damaged like PNS can Nerve Cell Development molecular signposts direct the way an axon grows to reach its target cell growth cone: responsive region at leading edge of axon; has receptors on its membrane that bind to signal molecules released by target cells (axon may respond by growing towards or away from target cell) cell adhesion molecules (CAMs): on axon’s growth cone; attach to complementary CAMs on surrounding cells to provide a track nerve growth factor (released by astrocytes) and growth-promoting proteins stimulate growth of axons the basic method of axon guidance is similar b/t many organisms Neural Stem Cells new nerve cells are made during adulthood in hippocampus stimulating minds and exercising bodies may = greater learning capacity the new adult cells must come from stem cells; studying stem cells is limited