Chapter 7 The Nervous System
Control of the body’s cells is accomplished by 2 systems: Nervous System – transmits info by nerve impulses endocrine system – transmits info by chemicals (hormones)
Organs of the nervous system: Brain Spinal cord Nerves Sense organs (ears, eyes, tongue, nose, skin)
Functions of the nervous system: 1.) use sensory receptors to monitor stimuli inside & outside the body 2.) process & interpret sensory input then integrates the info to make a decision about what to do 3.) effects a motor output (response) be activating glands or muscles
Structural classification of the nervous system: There are 2 main divisions of the nervous system 1.) central nervous system (cns) – consists of the brain & spinal cord - acts as the integrating & command center - interprets incoming sensory info & issues instructions based on past experience & current conditions 2.) PERIPHERAL NERVOUS SYSTEM (pns) – CONSISTS OF ALL NERVES THAT EXTEND OUTWARD - ACTS AS THE COMMUNICATION LINES LINKING ALL PARTS OF THE BODY - CARRIES IMPULSES FROM SENSORY GLANDS TO CNS & FROM THE CNS TO APPROPRIATE GLANDS OR MUSCLES
THERE ARE 2 SUBDIVISIONS OF THE PNS: A.) SOMATIC NERVOUS SYSTEM – SKELETAL MUSCLE CONTROL B.) AUTONOMIC NERVOUS SYSTEM (ans) – REGULATE THE BODY’S INVOLUNTARY FUNCTIONS - THE ANS CONSISTS OF 2 SUBDIVISIONS: I.) PARASYMPATHETIC NERVOUS SYSTEM – DOMINATES CONTROL OF MANY VISCERAL EFFECTORS UNDER NORMAL CONDITIONS ii.) Sympathetic nervous system – serves as the emergency or stress system – “flight or Fight” syndrome
Nerve Impulses: Self-propagating wave of electrical disturbance that travels along the surface of the neuron’s plasma membrane Initiated by a stimulus Resting potential of each neuron is polarized – more (+) outside cell & more (-) on the inside In polarized state, Sodium is outside cell, & potassium is inside
How is a nerve impulse transmitted? 1.) a stimulation causes the cell membrane to become permeable to sodium which rushes into the cell – depolarization 2.) neuron is activated & an action potential (nerve impulse) is transmitted 3.) when an action potential is initiated, it changes the permeability of the adjacent membrane & the same depolarization occurs 4.) after the rush of sodium, membrane permeability changes again & sodium can’t get through but potassium can diffuse out – the outflow of (+) charges restores the electrical conditions of the cell - repolarization
What is a Reflex arc? a special type of neural pathway where action potentials are conducted from some receptors to effector organs over reflex arc that result in a reflex ( rapid, predictable & involuntary contraction by a muscle or a gland) 2 classifications: a.) autonomic reflex – regulate smooth muscle (digestion, sweating, etc) B.) somatic reflex – all those that stimulate skeletal muscle (withdrawing from a hot surface)
Components of simple reflex arcs: 1.) a sensory receptor 2.) an effector organ 3.) afferent neurons 4.) efferent neurons
Types: 2 neuron reflex arc – simplest – goes from sensory neuron to effector neuron Ex.) knee jerk 3neuron reflex arc - from sensory neuron to interneuron to motor neuron Ex.) withdrawal reflex
Other reflex arcs terms: Ipsilateral reflex arc – receptors & effectors are on the same side of the body Contralateral reflex arcs- receptors & effectors are on the opposite sides of the body
The synapse: Space separating the axon end on 1 neuron (presynaptic neuron) from the dendrite of another (postsynaptic neuron) Where impulses are transmitted
3 structures that make up the synapse: 1.) synaptic knob – contains the neurotransmitters Types of neurotransmitters are: a.) acetylcholine- stimulates muscle cells b.) dopamine – affects sleep, moos, attention, learning & muscle movement C.) serotonin – same as dopamine D.) norepinephrine – increase bp, metabolic activity, constrict certain blood vessels E.) endorphin – natural analgesics to decrease pain perception F.) Enkelphalin – pain killers
2.) Synaptic cleft – space btw a synaptic knob & the plasma membrane of a postsynaptic neuron 3.) plasma membrane