* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Presentation 5: The Role of the Nervous System
Clinical neurochemistry wikipedia , lookup
Neuropsychopharmacology wikipedia , lookup
Electromyography wikipedia , lookup
Development of the nervous system wikipedia , lookup
Molecular neuroscience wikipedia , lookup
Nonsynaptic plasticity wikipedia , lookup
Neural coding wikipedia , lookup
Embodied language processing wikipedia , lookup
Psychophysics wikipedia , lookup
End-plate potential wikipedia , lookup
Biological neuron model wikipedia , lookup
Neuroscience in space wikipedia , lookup
Neurotransmitter wikipedia , lookup
Feature detection (nervous system) wikipedia , lookup
Neuroregeneration wikipedia , lookup
Chemical synapse wikipedia , lookup
Circumventricular organs wikipedia , lookup
Caridoid escape reaction wikipedia , lookup
Neuroanatomy wikipedia , lookup
Nervous system network models wikipedia , lookup
Central pattern generator wikipedia , lookup
Premovement neuronal activity wikipedia , lookup
Synaptic gating wikipedia , lookup
Neuromuscular junction wikipedia , lookup
Proprioception wikipedia , lookup
Synaptogenesis wikipedia , lookup
The Role of the Nervous System Applied Kinesiology 420:151 Agenda Introduction to the nervous system Structural considerations Motor efferents and gradations of force Sensory afferents Reflex movement Introduction to the NS Functions: Sensory input afferent neurons Integration Motor output efferent neurons Properties: Irritability Conductivity Introduction to NS Levels of Control: Cerebral cortex Basal ganglia Timing and intensity smooth and precise motion Brain stem Homeostasis posture and equilibrium Cerebellum Consciousness Arousal and cardiorespiratory function Spinal cord Link b/w CNS and PNS interneurons and synapses Cerebral cortex Basal ganglia Cerebellum Brain stem Spinal cord Overide? Figure 4.14, Hamilton Introduction to the NS Basic divisions of the nervous system: Figure 14.1, Marieb & Mallett (2003) Agenda Introduction to the nervous system Structural considerations Motor efferents and gradations of force Sensory afferents Reflex movement Structural Considerations The The The The neuron nerve synapse motor unit The Neuron Functional unit of nervous tissue Three main types of neurons Sensory/afferent neurons Motor/efferent neurons Interneurons Common structures Figure 12.11, Marieb & Mallett (2003) Dendrites Cell Body Axon Differences: Peripheral body, location of dendrites/synaptic knobs, direction of transmission The Neuron Other considerations Cell body Dendrites Nucleus Almost all cell bodies are in spinal cord (ganglia?) Afferents cell body via peripheral body Efferents cell body via axon Axon Myelin sheath Axon collaterals Extensive terminal branching (10,000) Synaptic knobs Figure 12.4, Marieb & Mallett (2003) Structural Considerations The The The The neuron nerve synapse motor unit The Nerve Nerve = bundle of neurons Not unlike skeletal muscle architecture Figure 12.17, Marieb & Mallett (2003) The Nerve Nerves can contain both afferent and efferent neurons. Spinal/peripheral nerves connect to the spinal cord via: Anterior root (motor efferent neurons) Posterior root (sensory afferent neurons) Posterior root Anterior root The Nerve Thirty one pairs of spinal/peripheral nerves: Cervical 8 Thoracic 12 Lumbar 5 Sacral 5 Coccygeal 1 Figure 13.29, Marieb & Mallett (2003) Structural Considerations The The The The neuron nerve synapse motor unit Figure 12.7, Marieb & Mallett (2003) The Synapse Synapse: Area between the synaptic knob of one neuron and the membrane of another neuron Neurons have thousands of synaptic knobs Some neurons are excitatory, some inhibitory Competition between excitation and inhibition occurs Threshold stimulus reached? NMJ or motor end plate Neurotransmitter Figure 12.8, Marieb & Mallett (2003) Excitatory and Inhibitory Postsynaptic Potentials: EPSP, IPSP EPSP - IPSP = Stimulus Stimulus > Threshold = Excitation of impulse Stimulus < Threshold = Inhibition of impulse Impulse itself can be excitatory or inhibitory in nature Structural Considerations The The The The neuron nerve synapse motor unit The Motor Unit Functional unit of neuromuscular system Consists of: Neuron + all muscle fibers Eye muscles vs. gastrocnemius (10-2000) Fewer fibers/neuron = precision More fibers/neuron = force Figure 14.6, Marieb & Mallett (2003) Agenda Introduction to the nervous system Structural considerations Motor efferents and gradations of force Sensory afferents Reflex movement Efferents: Gradations of Force Motor efferent: Sends signal away from the CNS (skeletal muscle) Dendrites in spinal cord Synaptic knobs muscle Excitatory or inhibitory Gradation of force: Concept: Muscles are able to activate with varying degrees of force Efferents: Gradations of Force Two factors influence the gradation of force: Number coding: The number of motor units participating Rate coding: The frequency of stimulation Number Coding All-or-none principle of single motor units threshold Gradation of force Small force = fewer motor units or motor units with less fibers Large force = more motor units or motor units with more fibers Orderly sequence Size principle Resting muscle tonus achieved via alternating activation of some muscle fibers Figure 19.13, Plowman & Smith (2003) Rate Coding Effects of different stimulus frequencies on motor units: Single stimulus twitch Second stimulus added prior to full relaxation temporal summation Multiple stimuli added so that any relaxation is prohibited irregular and fused tetanus Maximum number coding + maximum rate coding = maximum force • Temporal Summation – increase in tension with increased frequency of stimuli • Tetanus – sustained tension between stimulus As frequency increases, force/tension increases Agenda Introduction to the nervous system Structural considerations Motor efferents and gradations of force Sensory afferents Reflex movement Sensory Afferents Sensory afferents: Sends signal towards the CNS Dendrites are all over body (not in CNS) Synaptic knobs are in spinal cord Classifications of afferents: Exteroceptors Interoceptors (visceroceptors) Proprioceptors Figure 14.1, Marieb & Mallett (2003) Proprioceptors are main concern Proprioceptors Location: Tendons, skeletal muscle, ligaments, joint capsules and inner ear Functions: Transmit movement information CNS CNS integrates and initiates appropriate response (consciously/subconsciously) Provide sense of body awareness Provide stimulus for reflexes Proprioceptor Classification Muscle proprioceptors: Joint and skin proprioceptors Muscle spindles Golgi tendon organs Ruffini endings Pacinian corpuscles Labyrinthine and neck proprioceptors Labyrinthine proprioceptors Neck proprioceptors Muscle Proprioceptors: Muscle Spindles Location: Lay between and parallel to muscle fibers Structure: Tiny capsules (1 mm) Filled with fluid and intrafusal muscle fibers Nucleated and supplied with afferent neuron Function: Sensitive to stretch and tension of skeletal muscle tissue Transmit to CNS Excitatory impulse agonist and synergists Inhibitory impulse antagonists (reciprocal inhibition) Figure 14.5, Knutzen & Hamill (2004) Stretch Interneurons Excitatory activation of agonists Activation of synergists Reciprocal inhibition of antagonists Muscle Proprioceptors: GTOs Location: Musculotendon junction of skeletal muscle Structure: Mass of terminal endings in connective tissue capsule Connections both with tendon and fibers Function: Sensitive to tension in tendon due to both stretch and shortening of muscle Transmit to CNS: Inhibitory impulse agonists and synergists Excitatory impulse antagonists 1. High muscle tension 3. GTO activation 4. Inhibition of agonist 2. High tendon tension Joint and Skin Proprioceptors: Ruffini Endings Location: Beneath skin, joint capsules Structure: Spray of dendrites in flattened connective tissue capsule Functions: Sensitive to Rapid changes in joint angle Constant pressure resulting in deformation of capsule Skin and Joint Proprioceptors: Pacinian Corpuscles Location: Beneath skin, joint capsules, ligaments and tendons Structure: Relatively large (naked eye) Tip of single dendrite in connective tissue capsule Function: Sensitive to Rapid changes in joint angle Rapid, short-term changes in pressure resulting in deformation of capsule Pacinian corpuscle Ruffini endings Free nerve endings Labyrinthine Proprioceptors Location: Inner ear Structure: Several structures within the ear Function: Detect orientation and movements of the head Neck Proprioceptors Location: Ligaments of cervical vertebrae Function: Head/neck movement transmit opposite signals Prevents sense of imbalance Agenda Introduction to the nervous system Structural considerations Motor efferents and gradations of force Sensory afferents Reflex movement Reflexes Reflex: Specific pattern response that occurs without volition The reflex arc consists of: Receptor organ Afferent neuron Interneuron (sometimes) Efferent neuron Figure 12.18, Marieb & Mallett (2003) Classification of Reflexes Exteroceptive reflexes: Respond to external stimuli Extensor thrust reflex Flexor reflex Crossed extensor reflex Proprioceptive reflexes: Response to internal stimuli Stretch (myotatic) reflex Tendon reflex Righting reflex Tonic neck reflex Labyrinthine reflex Exteroceptive: Extensor Thrust Reflex General mechanism: Pressure stimulates pacinian corpuscles excitatory impulse to extensors Examples: Standing Shifting weight preparation for motion Hands cartwheel or back handspring Exteroceptive: Flexor Reflex General mechanism: Typically in response to pain excitatory impulse to flexors Examples: Pricking or burning hand Exteroceptive: Crossed Extensor Reflex General mechanism: Functions cooperatively with flexor reflex Contralateral limb is extended Examples: Stepping on tack Pricking or burning hand Proprioceptive: Stretch Reflex General mechanism: Stretched muscle results in stretched muscle spindle Excitatory impulse to agonist for protection Inhibitory impulse to antagonists Two types: Phasic: Rapid stretching rapid powerful contraction that ends rapidly Tonic: Slow stretching smooth, less powerful contraction that lasts as long as the stretch Elbow flexed 90 degrees while holding a bucket 1. Object dropped into bucket 2. Object dropped in from lesser height 3. Object placed into bucket Figure 14.12, Hamilton Explosive movements: Long and rapid prep phases (phasic stretch reflex) Precise movements: Short and slow prep phase (tonic stretch reflex) Proprioceptive: Tendon Reflex General mechanism: Sensitive to tension in tendon due to: Muscle lengthening Muscle shortening Tendon reflex vs. stretch reflex Very sensitive (low threshold) Threshold stimulus inhibitory impulse to agonists Extreme cases total relaxation Training or extreme stress can increase the threshold Proprioceptive: Righting Reflex General mechanism: Body tilting thrusting of limbs to restore balance Example: A gentle push with eyes shut Proprioceptive: Tonic Neck Reflex General mechanism: Head movement results in flexion or extension of limbs Obvious in infants Surpressed in adults evident under stress Examples: Symmetric vs. asymmetric Neck flexion: Upper extremities flex Neck extension: Upper extremities extend Neck rotation: Extension/Abduction of contralateral arm Flexion/abduction of ipsilateral arm. Proprioceptive: Labyrinthine Reflex General mechanism: Movements of the head activation of limbs to maintain balance