Peripheral Nervous System PDF

5. Peripheral Nervous System Course Human Anatomy & Physiology Status Complete Materials 5. Peripheral Nervous System - Slides Textbook Chapter 14 &15 Date...

5. Peripheral Nervous System Course Human Anatomy & Physiology Status Complete Materials 5. Peripheral Nervous System - Slides Textbook Chapter 14 &15 Date @September 24, 2024 The Peripheral Nervous System Receptors Nerves Plexus The Dermatome Subdivisions of PNS Comparison of Somatic & Autonomic NS The Somatic NS Ascending and Descending Spinal Tracts Sensory Path for Touch & Pressure Motor Path for Precise Voluntary Skeletal Muscle Control Brain function The Autonomic NS Sympathetic Nervous System 5. Peripheral Nervous System 1  Sympathetic Chain Parasympathetic Nervous System ANS Neurotransmitters and Receptors Cholinergic Receptors: Nicotinic & Muscarinic Adrenergic Receptors: Alpha or Beta Sympathetic & Parasympathetic Summary: The Peripheral Nervous System Structure: Consists of receptors, nerves, ganglia and motor nerve endings Function: Provides links to and from the outside Receptors Function: detect stimuli Structures: Complex receptor: include eye or ear Simple receptor: dendrite ending Types of simple receptors Mechanoreceptor: respond to membrane distortion Baroreceptor: pressure of fluid Interceptors (inside) and against vessel wall Exteroceptors (outside) Chemoreceptor: chemical Proprioceptors: body position Thermoreceptor: temperature Nociceptor: pain Nerves 5. Peripheral Nervous System 2  Nerve: a grouping of axons that travel together in PNS connecting receptors & effectors to CNS Axons are grouped and wrapped in membranes Epineurium around fascicles Perineurium is around a fascicle Endoneurium is around axons Fascicle = bundle Plexus 5. Peripheral Nervous System 3  Plexus: a branching and rejoining of nerves creating alternative paths Function: Ensures that info to and from limbs is not carried in one path but many Incase of injury, not all function to that area is lost Brachial plexus Nerves & Plexus Cervical C1-C4 Neck & breathing Phrenic nerve (diaphragm) Brachial C5-C8 Controls arm & hands Thoracic T1-T12 chest, back, abdomen (intercostal n / intercostal m) The Dermatome Lumbar L1-L5 Dermatome: Specific segment or hips & thigh, Femoral nerve area of skin that is supplied by a single nerve Sacral S1-S5 Derma: skin thigh & lower leg, sciatic n. Tome: a cutting All spinal nerves are associated with a dermatome except C1 5. Peripheral Nervous System 4  Dermatome map follows a segmental pattern because are derived from cells of a somite these cells develop into 1. myotome or skeletal muscle 2. dermatome connective tissue including skin 3. sclerotome which gives rise to vertebrae Subdivisions of PNS Afferent Division: consists of receptors and nerves carrying sensory info to CNS Efferent Division: consists of nerves carrying motor info from CNS to effectors and is further subdivided into: Somatic: skeletal muscles Autonomic: smooth muscles and glands, cardiac muscles 5. Peripheral Nervous System 5  Comparison of Somatic & Autonomic NS Somatic Autonomic Smooth & Cardiac Muscle or Effector Skeletal Muscle Gland Cerebral Cortex (Primary Control Center Hypothalamus Motor) # Motor Neuron Path 2 (1 in PNS) 3 (2 in PNS) NT Acetyl Choline Acetyl Choline & Epinephrine The Somatic NS Ascending and Descending Spinal Tracts 5. Peripheral Nervous System 6  Motor Corticospinal: voluntary motor control Sensory Dorsal columns: (fasciculus gracilis & cuneatus): fine touch & pressure Spinocerebellar: proprioceptors going to cerebellum Spinothalamic: pain Sensory Path for Touch & Pressure Neuron 1: Sensory receptor of unipolar neuron produces an action potential Axon enters spinal cord via dorsal root and travels up in dorsal columns Neuron 2: Synapses in the medulla and crosses over Neuron 3: Synapses in the thalamus (crude sensation) Travels to primary somatosensory in cerebral cortex (precise body awareness) 5. Peripheral Nervous System 7  Motor Path for Precise Voluntary Skeletal Muscle Control Neuron 1: Axon of pyramidal cell of motor cortex travels down brain stem in cerebral peduncles and pyramids Crossing over in medulla (80%) Travelling down the spinal cord in the anterolateral corticospinal tract Neuron 2: Synapses in the ventral horn of spinal cord and exits via ventral root Travelling to the muscle Brain function 1. Sensory info arrives from body via depends on the connections thalamus and is sent to primary between functional areas somatosensory cortex 2. Is interpreted in somatosensory association 3. Is sent to prefrontal cortex to establishes intent 4. Premotor cortex along with basal nuclei (& midbrain) sets up motor action 5. Peripheral Nervous System 8  5. Primary motor sends out command to skeletal muscles and spinal cord 6. Cerebellum corrects ongoing movement: receives info from proprioceptors and intent from cerebral cortex 7. Spinal cord directs motor movements not involving higher brain (reflexes) The Autonomic NS Effectors: Cardiac muscle, Smooth muscle, Glands (i.e. visceral organs) Control centers: Hypothalamus or Medulla Two subdivisions: Sympathetic and Parasympathetic Maintain homeostasis 5. Peripheral Nervous System 9  Most organs are dual innervated and effects are antagonistic Some organs are solely innervated Two systems can cooperate (sexual response) Sympathetic Nervous System Sympathetic NS: the Fight or Flight Response that prepares body for action exercise, emergency, emotions Location: thoracic lumbar regions Spinal cord origin Is Catabolic Pathway: Short preganglionic fiber, Long postganglionic ganglion distant from organ (i.e. Sympathetic Ganglion Chain) Innervates: both trunk & limbs and viscera NT Release: ACh (at ganglion), Epi (at target) (adrenergic) Dominated by: Adrenal Medulla Widespread effects: highly branched Long lasting: adrenal medulla releases epinephrine into blood stream affecting many targets 5. Peripheral Nervous System 10  Stress: amygdala receives sensory info and perceives it as danger, sends a distress signal to hypothalamus that initiates sympathetic response for a burst of energy Dry mouth, pupils dilate Sweat to dissipate heat for more efficient muscle action “ cold sweat” or perspiration and flushing Increase HR, BP, breathing providing extra oxygen for muscle and brain activity Release glucose for energy (mobilize energy reserves) Reroute blood to skeletal muscles and brain from skin (cold) Sharpening of senses and changes in brain wave activity Inhibition of digestive and urinary tract Other effects: palpitations, tachycardia, nausea, diarrhea, constipation Endocrine effects: adrenal medulla releases epinephrine Adrenal cortex releases cortisol with chronic or long term stress Sympathetic Chain Linked ganglion adjacent to spinal cord 3 paths through: 1. Synapses directly to postganglionic neuron and exits 2. Passes in and travels up or down before synapsing and exiting 3. Travels straight through, synapsing in periphery (collateral ganglion or adrenal medulla) 5. Peripheral Nervous System 11  Parasympathetic Nervous System 5. Peripheral Nervous System 12  Parasympathetic NS: Rest and Digest response that conserves energy Location: Cranial Sacral region spinal cord origin Is Anabolic supporting maintenance & repair Pathway: Long preganglionic, Short postganglionic fibers Innervates: viscera NT Release: ACh (at ganglion), ACh (at target) (cholinergic) Dominated by: Vagus nerve Effects: more localized and short-lived (less Branching) To Conserve Energy: Pupils constrict Heart slows Constricts bronchiole Contracts urinary bladder Gut is stimulated for digestion, absorption and excretion Increase in peristalsis (muscle contractions of GI tract that move food along), salivation, bile secretion ANS Neurotransmitters and Receptors 5. Peripheral Nervous System 13  Cholinergic synapses: release acetylcholine Adrenergic synapses: release epinephrine & norepinephrine each NT has a group of subtypes or different receptors that it can bind to resulting in different responses Drugs target receptor differences Cholinergic Receptors: Nicotinic & Muscarinic ACh binds to 2 different receptors plus their subtypes: 1. Nicotinic receptors: is an ion channel that opens or closes Found in: All skeletal muscles (Somatic NS) Preganglionic fibers (Autonomic NS) NS hormone producing cells of adrenal medulla 2. Muscarinic receptors: Found in: All post ganglionic fibers of PS and a few Sympathetic targets (sweat glands) M1: increases gland secretion, GI & CNS M2: decreases heart rate and force, decreases bronchiole dilation M3: smooth muscle contraction (Parasympathetic response), Increase GI motility, Eye (pupil) i.e. ciliary m. contracts for short focus, iris sphincter contracts pupil bladder wall relaxes smooth muscles of sphincters & blood vessels (blood is shunted to periphery) increases insulin and glycogen (energy conservation) increases secretion of glands i.e. saliva, tears, gastric and other glands of GI tract 5. Peripheral Nervous System 14  Adrenergic Receptors: Alpha or Beta Epi/Norepi binds to 2 different receptors plus their subtypes: mediated by second messenger G protein cascade that stimulates or inhibits cAMP or Calcium release 1. Alpha 1: results in a release of intracellular calcium constricts blood flow to periphery i.e. to skin and GI tract shunting blood to core sphincter constriction of GI tract and urinary system shuts down GI tract eye dilates (constriction of radial muscle of iris) 2. Alpha 2: receptors inhibit cAMP decrease in insulin release 2. Beta 1: cardiac muscle increase heart rate and force (positive inotropic & chronotropic effect) increases renin secretion in kidneys (increase volume i.e. BP) increase metabolism in liver & muscle & adipose 3. Beta 2: relax or dilate bronchioles of increasing air exchange of the respiratory system Dilates blood vessels to Coronary vessels (i.e. supply heart muscle) Dilate blood vessels to skeletal muscle and to brain Relaxes smooth muscle of bladder Stimulates peristalsis of GI tract and urinary tract 4. Beta 3: increase lipolysis of adipose tissue Acetyl Choline muscarinic receptors: sweat glands Sympathetic & Parasympathetic Summary: Two systems are usually antagonistic but can cooperate or act solo 5. Peripheral Nervous System 15  Sympathetic Parasympathetic Region Thoracic lumbar Cranial sacral Short preganglionic: Long Long preganglionic: Short Fibers postganglionic post ganglionic Hormones ACh, E&NE (adrenergic) ACh, ACh (cholinergic) Dominated by: adrenal medulla Vagus nerve Effects long-lasting & diffuse short-lived & local Function Mobilizes energy for action Maintenance and repair Metabolic Catabolic Anabolic 5. Peripheral Nervous System 16