Unit 5 The Nervous System Lecture1 Nervous system functions 1 Collecting information Receptors monitor inside and outside 2 Evaluating decision making Integrate sensory input and make decisions 3 Triggers responses Activating muscles and glands Peripheral nervous system Arises Cranial nerves from the brain Table 14 1 p 551 558 Spinal nerves from the cord 31 pairs 1st cervical between occipital condyle and atlas 8th cervical between c7 and t1 Arise pairs of roots Rootlets come together form roots Roots combine to form spinal nerves Exit from vertebral column through intervertebral foramen Cell bodies form dorsal root ganglion enlargement of dorsal root Dorsal root sensory receptors to cord Ganglion group of neuron cell bodies in the PNS slide10 Ventral root efferent fibers cord to skeletal muscles Gives rise to peripheral nerves Peripheral nerves carry afferent efferent and visceral efferent fibers Spinal nerves in cervical lumbar sacral regions form plexuses Plexus network of converging and diverging nerve fibers Thoracic region Do not enter plexuses except t1 t2 t12 Form single nerves to muscles of chest and abdomen Sensory portions all spinal nerves organized into dermatomes cutaneous region of sensation specific spinal nerve Autonomic nervous system Efferent Involuntary part of PNS Innervates Smooth muscle of blood vessels Abdominal and thoracic visceral organs Many glands Cardiac muscle of heart Importance maintain homeostasis Without conscious control Efferent system Sensory input from visceral sensory neurons via afferent divisions of PNS Anatomically and physiologically 2 divisions 1 Sympathetic or thoracolumbar ventral roots all thoracic and L1 3 2 parasympathetic or craniosacral CN 3 7 9 10 and ventral roots of S2 3 4 Both 2 neuron chain ganglion between Preganglionic neuron in cord of brain Sends myelinated axon out of CNS part of CN or SN To autonomic ganglion Synapses in ganglion with postganglionic neuron Sends fibers to effector organ ex Smooth muscle cardiac muscle gland Both have cell bodies in CNS Somatic NS 1 neuron CNS to effector Fibers myelinated Neurotransmitter at effector synapse ACh NT effect always excitatory stimulates contraction ANS sympathetic 2 neurons CNS to effector Preganglionic fibers lightly myelinated NT for preganglionic synapse ACh Postganglionic fibers unmyelinated NT at effector norepinephrine ANS parasympathetic 2 neurons CNS to effector Preganglionic fibers lightly myelinated Postganglionic fibers unmyelinated NT at both synapses ACh Autonomic Somatic comparison Signals travel faster in somatic system Fewer synapses Fibers heavily myelinated NT effect in ANS depends on receptors on target organ May inhibit or excite Somatic versus autonomic pathways Sympathetic parasympathetic comparison Preganglionic cell bodies Sympathetic cell body lateral horn of cord Parasympathetic cell body brain stem sacral cord In sympathetic chain ganglia along vertebral column Also in 3 cervical ganglia superior to chain Postganglionic cell bodies Sympathetic Parasympathetic In effector organ wall Length of fibers Sympathetic Parasympathetic Preganglionic short Postganglionic long Preganglionic long Postganglionic short NT at the effector Sympathetic Norepinephrine Widespread in the body Fight or flight arousal Parasympathetic response generally antagonistic Eye Sweat Glands ACh Single response at effector Synapse close to effector Rest and repair Organ System Sympathetic Parasympathetic Dilated More Sweating Constricted None Heart Rate Respiration Digestive Tract Digestive Secretions Decrease Increased Rapid deep Inhibits salivary gastric Decreased Slow Excites Increase Afferent and efferent functions Central nervous system Spinal cord brain Spinal cord Cross sectional view Gray matter cell bodies H shape varies along length of cord Lateral horn Found only in thoracic region Has preganglionic neurons of sympathetic division Dorsal horn Smaller of gray regions Contain cell bodies of association neurons Synapse with sensory fibers from dorsal root ganglia Ventral horn Cell bodies of motor neurons Larger in plexus regions Correspond to cervical lumbar enlargements Motor neuron Cell bodies organized by region innervated Medial part of ventral horn proximal limb Lateral part of ventral horn distal limb Dorsal flexors Ventral extensors Somatotopic representation Point to point correspondence between body structures and brain or spinal cord regions Called somatotopy or somatotopic representation White matter Outside gray matter Contains myelinated fibers Ascending sensory Descending motor Divided into 3 regions funiculus or column Anterior lateral posterior Funiculi organized into fasciculi or tracts Carry information Cord to brain Brain to cord Cord to cord Tracts named carry specific information Fasciculi Examples Name Location in cord Function sensory or motor Information carried Between cord levels fasciculi close to gray matter Fiber tracts Lateral spinothalamic Cord to thalamus Sensory pain temperature deep pressure touch Fasciculus cuneatus From upper extremity to thalamus Sensory proprioception touch light pressure Fasciculus gracilis From lower extremity to thalamus Sensory proprioception touch light pressure Dorsal spinocerebellar Cord to cerebellum Sensory from muscle spindle Reticulospinal Reticular formation of pons medulla to cord Motor extensor motor neurons tone Rubrospinal Red nucleus to skeletal muscle Motor flexor motor neurons tone nucleus mass of nerve cell bodies in CNS like ganglia Lateral and ventral corticospinal Cerebral cortex motor region to each spinal level for muscles Motor skilled movements voluntary contraction Largest most important motor tracts In medulla Lateral CS decussate or crossover Connect motor cortex with muscles on opposite side of body Pyramids pyramidal motor tracts Both synapse With association neurons Or directly with motor neurons Summary Name Motor descending or sensory ascending Where in CNS to and form Passes through many structures Synapses occur opportunity to spread information Can make decisions Actions transmitted to effectors List of some structures tracts pass through Medulla Pyramids Reticular formation Pons Crus cerebri Inferior cerebellar peduncle Midbrain Red Nucleus Cerebral cortex Thalamus Internal capsule Sensory cortex Cerebellum Hypothalamus Motor cortex Lecture2 The brain General structure Embryological development procedures 3 regions of enlargement of the neural tube Developed brain many