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exphys ch7

The Nervous System and Control of movement

Summary of functions of nervous system 1) control of internal environment 2) voluntary control of movement 3) programming of spinal cord reflexes 4) assimiliation of experiences necessary for memory and learning
CNS components? brain and spinal cord
PNS components? neurons, afferent and efferent fibers
structure of the neuron (3 parts) cell body, dendrites, and axon
the cell body is important because.. it contains the nucleus
the dendrites have what role? contains receptive area and conduct impulses toward cell body
what does the axon do? carries electrical message
what is a synapse? contact point between axon of one neuron and the dendrite of another neuron
what are schwann cells? insulating layer cells that cover axons
irritability- the ability of dendrites and neuron cell body to respond to a stimulus and convert it to a neural implulse
conductivity- transmission of an impulse along the axon
afferent fibers conduct information toward CNS receptors --> CNS
efferent fibers conduct information away from CNS CNS---> effector organs
2 subcategories of peripheral nervous system (PNS) Sensory and Motor
2 subcategories of Motor PNS somatic and autonomic
somatic= skeletal muscles, voluntary
autonomic= smooth and cardiac muscles, glands; involuntary
what is multiple sclerosis? neurological disease that destroys myelin sheaths of axons, causes progressive loss of NS, exercise can improve functional capacity
synaptic trasmission dendrites ---> axon ----> synapse
what is resting membrane potention (RMP)? the voltage difference measured across a membrane
2 main factors of RMP 1) related to concentration of ions on each side 2) permeability of membrane to ions
Magnitude range/ neurons general range -5 to -100 mv / -45 to -75 mv
Alan Lloyd Hodgkin? received nobel peace prize for Physiology - his research on chemical process that allow neurons to transmit impulses from periphery to brain
steps for a neural message to be generated: 1) stimulus with sufficient strength reaches neuron membrane 2) opens sodium gates 3) sodium ions diffuse neuro 4) cell is depolarized (becomes more and more positive)
Threshold the critical value that when reached sodium gates open wide and an action potential is formed. (nerve impulse)
what occurs immediately following depolarization to return to RMP? repolarization
The 4 steps of repolarization are: 1) depolarization causes brief increase in permeability to potassium 2) potassium leaves cell rapidly (inside becomes more negative 3) depolarization stimulus removed 4) sodium gates inside cell close and entry is slowed
At rest, neurons.. have a negative charge determined by concentrations of Na+, K+, Cl-
As sodium enters the neuron, the charge becomes more and more positive
EPSP Excitatory Postsynaptic potentials, causes depolarization, may or may not reach threshold
IPSP Inhibitory Postsynaptic potentials, causes hyperpolarization
2 ways EPSP can bring postsynaptic neuron to threshold 1) temporal summation 2) spatial summation
what is temporal summation? summing several EPSPs from one presynaptic neuron
what is spatial summation? summing from several different presynaptic neurons
proprioception- ability to determine position of joint
kinesthesia- sensation of joint motion or acceleration
3 types of proprioception free nerve endings, golgi-type, pacinian corpuscles
free nerve endings are sensitive to what?? touch and pressure
golgi-type detect... ligaments and joints
pacinian corpuscles tissues around joints, detect rate of joint rotation
GTO detect tension!
muscles spindles detect length!
three steps of muscle reflex 1) sensory nerve sends impulse to spinal column 2) interneurons activate motor neurons 3) motor neurons control movement of muscles
innervation ration= # of fibers/ motor neuron
vestibular apparatus- organ of inner ear responsible for maintaining general equilibrium
Brain is subdivided into.. brain stem, cerebrum, and cerebellum
brain stem- nerve tracts and nuclei (clusters of neurons), responsible for metabolic factors, cardiorespiratory control, and some highly complex reflexes
cerebrum- large dome of brain divided into R and L hemisheres, cerebral cortex- outer layer
what does the cerebral cortex do? organizes complex movement, stores learned experiences, and reception of sensory info
cerebellum- behind pons and medulla, complete knowledge about it is not available, important role in coordinating and monitoring complex movement.
primary role of cerebellum- aid in control of movement in response to feedback from proprioceptors, may initiate ballistic movement
spinal tuning= spinal mechanism by which a voluntary movement is translated into appropriate muscle action
what does the autonomic nervous system do? maintains constancy of body's internal environment
autonomic motor nerves innervate... cardiac and smooth muscle (effector organs) in general, the ANS operates below conscious level
Two divisions of the autonomic nervous system (ANS) sympathetic and parasympathetic
sympathetic division of ANS- tends to activate, cell bodies of preganglionic neurons are in thoracic and lumbar regions of spinal cord
parasympathetic division of ANS- tends to inhibit, cell bodies are in brain stem and sacral part of spinal cord
neurotransmitter in sympathetic ANS norepinephrine
neurotransmitter in parasympathetic ANS acetylcholine
How does exercise enhance brain health? enhances learning and memory, stimulates neurogenesis, improves brain vascular function and blood flow, attentuates mechanisms driving depression
motor unit a motor neuron and all the fibers it innervates
functions of muscle spindles 1. detect stretch of muscle 2. conduct action potentials to spinal cord 3. sensory neurons synapse w/ alpha neurons 4. causes muscle to contract and resist stretch
general design and physiological function of muscle spindle composed of several thin muscle cells surrounded by sheath, run parallel w/ muscle fibers, detect length, observe rapid stretching
function of GTo in monitoring muscle tension continuously monitor the tension developed during muscular contraction; serve as safety devices that help prevent excessive force during muscular contraction
Created by: sbush0804