Unit 4 Lecture 2 Notes I Smooth Muscles II Nervous System control and communication center of body A Afferent toward a structure or SENSORY information A Single Unit or Visceral smooth muscle examples hollow organs such as stomach and intestine s i Outer longitudinal layer runs the length of the structure and contracts to dilate expand and shorten muscle Inner circular layer contracts to constrict and elongate organ ii iii Rhythmicity repeated contractions without external stimulation self exciting fibers act as pacemakers depolarize 1 Gap junctions transmit stimulus to adjacent fibers 2 Fibers contract as a single unit iv Peristalsis wave like series of contractions that move material through digestive track B Multiunit smooth muscle occurs in separate fibers and require stimulation by motor nerves examples irises of eyes arrector pili of muscles large airways of lungs i i Info being sent and the structures carrying it to the brain or spinal cord ii Visceral afferents information from visceral organs iii Somatic afferents information from body muscle joints and skin B Efferent away from a structure or motor information Information and structures carrying it FROM brain spinal cord TO muscles glands ii Somatic Nervous System SNS conducts impulses to skeletal muscles voluntary iii Autonomic Nervous System ANS regulates smooth muscle cardiac muscle and glands involuntary 1 Sympathetic and Parasympathetic one excitation one C Functions inhibition i Collecting information receptors monitor changes inside and outside the body gathers afferent input ii Evaluating decision making processes and interprets sensory iii Triggers responses activate muscles and glands motor or efferent D Central Nervous System Function integration and command centers i Dictate response based on past experience reflexes and current E Peripheral Nervous System PNS carry sensory information to and motor information from the brain spinal cord i Cranial nerves peripheral nerves of brain ii Spinal nerves innervate most skeletal muscle input output conditions F Supporting Cells i 9X more numerous and provide support for neurons framework or scaffolding assist segregate insulate neurons 1 undergo mitosis repair and reproduce iii Satellite cells ii Schwann cells in PNS form myelin Sheaths and wrap around in PNS Arranged around cell bodies of neuron in nerves phagocytes peripheral ganglia help control chemical environment neurons electrically insult neurons regulate fluid ad gas exchange with neurons and environment CNS supporting cells framework for iv Neuroglial or glial cells 1 Astrocytes Largest most elaborate most numerous lots of radiating projections with bulbous ends to cling to neurons and capillaries a forma a living barrier between capillaries and neurons function in neuron metabolism control chemical environment around neurons 2 Microglia 3 Ependymal cells squamous to columnar shape and ciliates scavengers of CNS increase with injury phagocytize microorganisms and dead tissue line central ventricles form permeable barrier between cerebrospinal fluid and tissue fluid CNS and produce myelin sheaths small cells that wrap around nerve fibers in 4 Oligodendrocytes G Neuron or Nerve cells conducting cells basic functional unit of NS conduct impulses throughout system information i Long lived high metabolic rate requires lots of O2 and Glucose ii Amitotic cant reproduce iii Cell body usually in CNS and protected by cranial bones and vertebrae 1 Plasma membrane regulates exchange of materials in and out of cell a Assist in reception propagation and transmission of nerve impulse 2 Nucleus contains DNA 3 Nucleolus large amounts of RNA 4 Cytoplasm mitochondria Golgi complex lysosomes no centrioles no mitosis rough ER or Nissl Bodies a Neurofibrils bundles of microtubules and microfilaments that intracellular transport from body to processes iv Processes extend out from cell body 1 Dendrites Afferent process info to cells in body a Spines thorn like extensions that increase surface area to receive impulses 2 Axon efferent process info away from cell body a Arises from axon hillock b Telodendria branching filaments at distal end end in bulbous ends called axon terminal or synaptic knobs c May contain contralateral branches d Axolemma plasma membrane of axon myelinated 3 Myelin whitish fatty segmented sheath covering some nerve fibers ex Schwann cells and Oligodendrocytes a Protects and insulates fibers b Increases propagation speed c Creates Nodes of Ranvier spaces nodes between cells d Extends to telodendria e Myelination in PNS i Schwann cells indent to receive axon myelin wraps around axon ii Cytoplasm and nucleus squeeze to outer part forming plasma membrane and cytoplasm iii Neurilemma iv Unmyelinated fibers partly encloses axons surrounds myelin sheath Schwann cells indents and f Myelination in CNS many axons i Oligodendrocyte extensions coil around axon 1 H Neuron Structural Classes i Bipolar Neurons axon and dendrites on opposite ends 1 Always afferent ex Retina Olfactory mucosa ii Unipolar neurons single process from cell body divides axon dendrite 1 Always afferent ex found in PNS ganglia 2 Carry sensory impulses from receptors to CNS iii Multipolar neurons many processes 1 axon any dendrites 1 BOTH afferent and efferent I Neuron Functional Classes i Afferent or Sensory unipolar ii Association between afferent and efferent multipolar iii Efferent or Motor muscles and glands multipolar J Nerve Bundle of nerve fibers in PNS connective tissue sheath surrounds each nerve fiber group of nerve fibers held together by Perineurium CT i Endoneurium ii Fascicle sheath iii Epineurium hold together nerves or groups of fascicles K Nerve Tract bundle of nerve fibers in CNS fibers are axon and dendrites both myelinated and unmyelinated