neuro - Nervous System Chapters (12-15) Overview or Plan of...

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Unformatted text preview: Nervous System Chapters (12-15) Overview or Plan of Attack Overview and new terminology Chap 12.1 Spinal Cord Anatomy Chap 12.2 Peripheral Nerves Chap 12.3 Functional Anatomy of the Brain Chap 13.1-13.8 Cranial Nerves Chap 13.9-13.10 "Wiring" of the nervous system (circuits & pathways) Principles of Functional Organization Chap 12.4 Simple circuits Spinal Reflexes Chap 12.4-12.5 (maybe 12.6) Overview of Sensory and Motor Pathways 14.1 (read in text) Somatic Sensory Pathways Chap 14.2-14.3 Somatic Motor Pathways chap 14.4 Visceral Motor Pathways (ANS Autonomic Nervous System Chap 14.5-14.9 3 lectures Special Senses Vision 15.3 Hearing / Equilibrium 15.4 Smell and Taste read in text Chap 15.1-15.2 2 lectures Neural Circuits Neurons can "connect" to one another in a variety of ways to pass signals along the nervous system Often referred to as how the nervous system is "wired" Pattern of interaction between neurons gives insight into function of the circuit Neural Circuits 5 common arrangements of neurons in a circuit: Neural Circuits Simplest circuits = REFLEXES (Chap 12.4-12.5) Mediate rapid, automatic responses to various stimuli Many ways to classify types of reflexes Neural Circuits "Wiring" of a single reflex = reflex arc We will begin by examining the simplest reflex arc: THE STRETCH REFLEX monosynaptic, somatic, spinal reflex Sensor = MUSCLE SPINDLE (senses stretch of muscle) Neural Circuits Now a bit more complicated: THE WITHDRAWAL (FLEXOR) REFLEX polysynaptic, somatic, spinal reflex Sensor = PAIN RECEPTORS To brainstem and brain Notice: 1. DIVERGENCE 2. ROLE OF INTERNEURONS Neural Circuits On a larger scale, can discuss circuitry of PATHWAYS Nerves, nuclei, tracts, etc. that carry sensory info into the CNS or motor commands out of the CNS (Chap 14.1-14.4) Somatic Sensory pathways touch, temperature, pain Begin at peripheral receptors Pass along nerves (spinal or cranial) into spinal cord Follow specific routes along spinal cord (we will name these!) Relayed to specific parts of the brain (most to the POSTCENTRAL GYRUS) Somatic Motor Pathways voluntary control of skeletal muscles Begin in the brain (mostly PRECENTRAL GYRUS) Follow specific routes along spinal cord Exit spinal cord and pass along nerves (spinal or cranial) to reach muscle) Visceral Motor Pathways involuntary control of smooth muscle, heart, glands Also called AUTONOMIC NERVOUS SYSTEM (ANS) Somatic Sensory Pathways 1. Posterior Column Pathway MECHANORECEPTORS 1. Tactile Receptors THALAMUS MEDIAL LEMNISCUS (purple) Posterior Column NUCLEI MIDBRAIN 2. Proprioceptors POSTERIOR COLUMN (blue) MEDULLA DECUSSATION Somatic Sensory Pathways 2. Anterior Spinothalamic Pathway MECHANORECEPTORS 1. Tactile Receptors THALAMUS MIDBRAIN ANTERIOR SPINOTHALAMIC TRACT (green) DECUSSATION Somatic Sensory Pathways 3. Lateral Spinothalamic Pathway NOCICEPTORS THERMORECEPTORS THALAMUS MIDBRAIN LATERAL SPINOTHALAMIC TRACT (green) DECUSSATION Somatic Motor Pathways 1. Corticospinal Tracts MIDBRAIN Visceral Motor Pathways The AUTONOMIC NERVOUS SYSTEM Control of: 1. smooth muscle 2. cardiac muscle 3. glands Not controlled voluntarily - automatically regulated by nervous sys. - Hypothalamus and brainstem nuclei provide most control Visceral Motor Pathways The AUTONOMIC NERVOUS SYSTEM General Circuitry or "Wiring Scheme" 2 neuron pathway 1. Preganglionic Neuron (red) - goes from brainstem or spinal cord to ganglion outside CNS 2. Postganglionic Neuron (white) - goes from ganglion to target organ Autonomic Nervous System 2 Divisions of the Autonomic System with reciprocal innervations mediate opposing effects on targets will have individual variations in the wiring scheme SYMPATHETIC FEAR FIGHT FLIGHT PARASYMPATHETIC REST DIGEST Sympathetic Division Short preganglionic neurons (red) - cell bodies found in thoracic and lumbar region of spinal cord - axons go from spinal cord to sympathetic chain ganglia or close by ganglia Long postganglionic neurons (black) - sympathetic chain to target organ - Norepinepherine (NE, noradrenaline) mostly used as neurotransmitter (sometimes ACh) NE RECEPTORS PRESENT IN TISSUE MEDIATE EFFECT: -receptors 1 2 -receptors 1 2 Adrenergic Receptors 1 incr. heart rate and force of contraction - blood vessels of skin and GI Tract - blood vessels of the nasal mucosa - arrector pili muscle (skin hair) - urethral sphincter - thick salivary gland secretion - iris muscle (pupil dilation) 2 - bronchioles (airway dilation) - blood vessels of skeletal muscle - coronary blood vessels - intestinal relaxation - bladder wall relaxation Interestingly, increase in production of sweat mediated by release of ACh onto ACh receptors on sweat glands Parasympathetic Division Long preganglionic neurons (red) - cell bodies found in brainstem and sacral cord - axons go from spinal cord to distant ganglia Short postganglionic neurons (black) - ganglia to target organ - ACh as neurotransmitter ACh RECEPTORS PRESENT IN TISSUE MEDIATE EFFECT Not as complex as NE receptors, so we won't specifically cover Interestingly: - Blood vessels NOT innervated - Skeletal muscles NOT innervated ...
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