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INCOMING INFORMATION-RECEPTORS CENTRAL NERVOUS SYSTEM Central nervous system (CNS) Functions of the spinal cord brain and spinal cord enclosed in bony coverings Respond to stimuli: nerve endings (dendrites of neurons) sense organs (taste) Sensory Pathway (PNS) spinal cord reflexes i t g ti ((summation integration ti off iinhibitory hibit and d excitatory) it t ) nerve impulses highway for upward and downward travel of sensory and motor information Afferent neurons somatic and visceral sensory neurons Brain functions sensations, memory, emotions, decision making, behavior 14-1 MOTOR PATHWAY (PNS) 14-2 OVERVIEW OF SPINAL CORD Efferent neurons Stimulate and control effectors somatic motor neurons visceral motor neurons Autonomic Nervous System (ANS) • Sympathetic • Parasympathetic They both control the same effectors (with few exceptions) but have opposite responses in the effectors Information highway between brain and body Each pair of spinal nerves receives sensory information and issues motor signals to muscles and glands Spinal cord is a component of the CNS while the spinal nerves are part off the h PNS 14-3 FUNCTIONS OF THE SPINAL CORD bundles of fibers passing information up and down spinal cord Locomotion ANATOMY OF THE SPINAL CORD Conduction 14-4 repetitive, coordinated actions of several muscle ggroups p p central pattern generators are pools of neurons providing control of flexors and extensors (walking) Reflexes Cylinder of nerve tissue within the vertebral canal (thick as a finger) vertebral column grows faster so in an adult the spinal cord only extends to L1 31 pairs of spinal nerves arise from cervical, thoracic, lumbar and sacral regions of the cord each cord segment gives rise to a pair of spinal nerves involuntary, stereotyped responses to stimuli (remove hand from hot stove) involves brain, spinal cord and peripheral nerves 14-5 14-6 1 MENINGES OF THE SPINAL CORD 3 Fibrous layers enclosing spinal cord Dura mater tough collagenous membrane surrounded by epidural space filled with fat and blood vessels epidural anesthesia utilized during childbirth Arachnoid mater MENINGES OF VERTEBRA AND SPINAL CORD layer of simple squamous epithelium lining dura mater and loose mesh of fibers filled with CSF (creates subarachnoid space) Pia mater delicate membrane adherent to spinal cord 14-7 14-8 AREAS IN THE SPINAL CORD CROSS-SECTIONAL ANATOMY OF THE SPINAL CORD Central area of gray matter shaped like a butterfly and surrounded by white matter in 3 columns Gray matter = neuron cell bodies with little myelin White matter = myelinated axons White column = bundles of myelinated axons that carry signals up and down to and from brainstem 3 pairs of columns or funiculi 14-10 14-9 WHITE MATTER IN THE SPINAL CORD Pair of dorsal or posterior horns dorsal root of spinal nerve is totally sensory fibers Pair of ventral or anterior horns ventral root of spinal nerve is totally motor fibers Connected by gray commissure punctured by a central canal continuous above with 4th ventricle dorsal, lateral, and anterior columns REFLEXES Automatic response to change in environment Integration center for spinal reflexes is gray matter of spinal cord Examples Each column is filled with named tracts (fibers with a similar origin, destination and function) Ascending and descending tract head up or down Contralateral means origin and destination are on opposite sides while ipsilateral means on same side somatic reflexes result in skeletal muscle contraction autonomic (visceral) reflexes involve smooth & cardiac muscle and glands. g 14-11 heart rate, respiration, digestion, urination, etc Reflexes can be: simple involve peripheral nerves and the spinal cord spinal reflexes learned (acquired) involve peripheral nerves and the brain 14-12 2 REFLEX ARC Specific nerve impulse pathway 5 components of reflex arc Receptor Registers stimuli Sensory neuron Integrating center Transmits stimuli to the CNS Part of the CNS that processes the information and generates response Motor neuron Effector THE PATELLAR TENDON REFLEX ARC Transmits the response to the effector Muscle or gland 4 important somatic spinal reflexes stretch, tendon, flexor(withdrawal) & crossed extensor reflexes 14-13 CENTRAL NERVOUS SYSTEM-THE BRAIN 14-14 THE BRAIN Longitudinal fissure - cerebral hemispheres. gyri = folds; sulci = grooves cortex = surface layer of gray matter nuclei = deeper masses of gray matter tracts = bundles of axons (white matter) 14-15 MEDIAN SECTION OF THE BRAIN 14-16 GRAY AND WHITE MATTER Gray matter = neuron cell bodies, dendrites, and synapses forms forms White matter = bundles of axons forms 14-17 cortex over cerebrum and cerebellum nuclei deep within brain tracts that connect parts of brain 14-18 3 VENTRICLES AND CEREBROSPINAL FLUID MENINGES OF THE BRAIN Internal chambers within the CNS lateral ventricles in cerebral hemispheres ventricle = single vertical space under corpus callosum cerebral aqueduct runs through midbrain fourth ventricle = chamber between pons and cerebellum central canal runs down through spinal cord third Lined with ependymal cells Choroid plexus produce CSF 14-20 14-19 CEREBROSPINAL FLUID BRAIN VENTRICLES Fills ventricles and subarachnoid space Brain produces and absorbs 500 ml/day Functions choroid plexus creates by filtration of blood floats brain so it is neutrally buoyant from hitting inside of skull chemical stability -- rinses away wastes cushions Escapes (4th ventricle) to surround brain Absorbed into venous sinus by arachnoid villi 14-22 14-21 HINDBRAIN - MEDULLA OBLONGATA Cardiac center Nuclei control rate and depth of breathing for coughing, sneezing, gagging, swallowing, vomiting, salivation, sweating, movements of tongue and head Most of the fibers are crossing over Reflex centers adjusts blood vessel diameter Respiratory p y centers Bulge in brainstem, superior to medulla Ascending sensory tracts Descending motor tracts Pathways in and out of cerebellum adjusts rate and force of heart Vasomotor center PONS concerned with posture, sleep, hearing, balance, taste, eye movements, facial expression, facial sensation, respiration, swallowing, and bladder control Left cortex controls right side of body 14-23 14-24 4 CEREBELLUM CEREBELLUM Two hemispheres connected by vermis Cortex = surface folds called folia Output comes from deep gray nuclei White matter (arbor vitae) visible in sagittal section Evaluation of sensory input granule and purkinje cells coordination and locomotor ability spatial perception Timekeeping center predicting movement of objects 14-25 MIDBRAIN - CROSS SECTION connects to cerebellum and helps control fine movements through red nucleus Scattered nuclei in medulla, pons & midbrain Reticular activating system Substantia nigra RETICULAR ACTIVATING SYSTEM Tegmentum 14-26 sends inhibitory signals to basal ganglia and thalamus (degeneration leads to tremors and Parkinson disease) Central gray matter = pain awareness alerts cerebral cortex to sensory signals ( (sound d off alarm, l flash fl h light, light smoke k or intruder) to awaken from sleep maintains consciousness & helps keep you awake with stimuli from ears, eyes, skin and muscles Motor function is involvement with maintaining muscle tone 14-27 DIENCEPHALON: THALAMUS AND HYPOTHALAMUS CEREBRUM -- GROSS ANATOMY Thalamus Functions 14-28 Relays signals from cerebellum to motor cortex Emotional and memory functions Hypothalamus Functions h ti hormone secretion autonomic NS control thermoregulation food and water intake (hunger and satiety) sleep and circadian rhythms memory (mammillary bodies) emotional behavior Cerebral cortex - 3mm layer of gray matter 14-29 extensive folds increase surface area - divided into lobes 14-30 5 FUNCTIONS OF CEREBRUM - LOBES TRACTS OF CEREBRAL WHITE MATTER Frontal voluntary motor functions planning, mood, smell and social judgement Parietal and integrates sensory information Occipital visual projection tracts receives Most of cerebrum is white matter Types of tracts f b i tto spinal i l cord, d fforms from brain internal capsule commissural tracts cross to opposite hemisphere center of brain Temporal corpus callosum anterior and posterior commissures association tracts areas for hearing, smell, learning, memory, emotional behavior 14-31 connect lobes and gyri within a hemisphere 14-32 MEMORY LIMBIC SYSTEM Information management Amnesia requires learning, memory and forgetting anterograde retrograde Loop of cortical structures Role in emotion and memory amygdala, pleasure sensory and cognitive information into a new memory 14-33 14-34 SYMPATHETIC DIVISION Visceral motor neurons control heart rate breathing rate digestion blood pressure salivation Nerve impulses of these motor neurons start in the CNS (medulla oblongata and pons) Pathway through: Cerebellum – helps learn motor skills Amygdala - emotional memory AUTONOMIC NERVOUS SYSTEM Hippocampus organizes hippocampus and cingulate gyrus and aversion centers amnesia - no new memories amnesia – can’t remember old ones Spinal cord Cranial nerves 14-35 The sympathetic division is called the “fight or flight” system when the body needs to generate energy exercise, excitement, emergency, and embarrassment Fight or flight response increases heart rate, blood pressure, respiration rate, blood flow to skeletal muscles, glucose metabolism decreases the activities that are not essential at the moment (digestive system organs are subdued- decreased blood flow to that system 14-36 6 PARASYMPATHETIC DIVISION activated when the body needs to conserve energy ORGANIZATION OF THE SYMPATHETIC DIVISION The parasympathetic division is called the “rest and digest” digestion, defecation, and diuresis (urination) Promotes necessary changes during these activities rate blood pressure, press re respiration rate, rate decreases heart rate, blood flow to skeletal muscles, glucose metabolism increases the activity of and blood flow to the digestive system organs 14-37 14-38 EFFECTS OF NEUROTRANSMITTERS OF THE AUTONOMIC NERVOUS SYSTEM EFFERENT SYMPATHETIC VS. PARASYMPATHETIC 14-39 The cells of each organ controlled by the ANS have both ACh and NE receptors organs are dually controlled The response of the organ is determined by the identity of the neurotransmitter released the binding of ACh to its receptor will cause the effector to respond in one way the binding of NE to its receptor will cause the effector to respond in the opposite way The effect of ACh and NE is effector specific NE increases heart rate, ACh decreases heart rate NE decreases the secretion of saliva, ACh increases the secretion of saliva 14-40 7