physio 2

• nervous system is fast, short acting
• endocrine system is slower, but longer lasting
• nervous system is the most complex system in the body

• monitors the body's internal and external environments
• integrates sensory information
• coordinates voluntary and involuntary responses

• CNS integrates and coordinates input and output
• PNS serves as connection between the CNS and organs

• afferent division: sensory receptors and neurons that send information to CNS
• efferent division: neurons that send info to effectors which are the muscles and glands
• -SNS (somatic)
• -ANS (automatic)

• dendrites receive signals
• axons carry signals to the next cell
• axon terminals synapse with the next cell
• cell bodies contain mitochondria, free and fixed ribosomes, and rough ER

• multipolar: 2 or more dendrites and one axon (most common)
• unipolar: hae cell body off to one side
• bipolar: one dendrite and one axon withthe cell body in the middle

• sensory (afferent neurons) receive information from sensory receptors (somatic vs. visceral receptors)
• motor (efferent) carry information to peripheral targets called effectors (somatic vs. visceral)
• interneurons (association neurons) function as links between sensory and motor processes 
• -located entirely in CNS and serve higher functions such as memory, planning and learning

• astrocytes: large, numerous neuroglia that maintain blood-brain barrier
• microglia: smallest and least numerous; phagocytic cells
• ependymal cells: line the fluid filled central canal of the spinal cord and ventricles of the brain (this lining is involved in producing and circulating cerebrospinal fluid)
• oligodendrocytes: insulating membranous wrapping around axons (myelin)

nodes of ranvier

• gray matter is regions of CNS composed of cell bodies
• white matter is myelinated axons

• satelite cells surround and support neuron cell bodies; similar in function to astrocytes
• schwann cells cover every axon in the PNS and produce insulating myelin; surface of the cell is called neurilemma

• neurons of the nervous system tend to group together in organized bundles
• cell bodies of neurons are clustered together into ganglia in PNS and nuclei/centers in CNS
• axons of neurons are bundled together to form nerves in PNS and tracts/pathways in CNS

excessive positive charge on the outside and negative charges on the inside (difference is called a membrane potential)

• types of stimuli
• -cellular exposure to chemicals 
• -mechanical changes
• -temperature changes
• -changes in ECF ion concentration
• stimuli alter membrane permeability to Na+ or K+ or alter activity of the Na+/K+exchange pump

• chemical binds and gate opens
• membrane voltage changes and activation gate opens

• activation gate closed
• depolarization happens when activation gate open and inactivation gate open
• inactivation closed

• opening Na+ channels lets Na+2 in; move membrane toward OmV (depolarization)
• opening K+channels results in efflux of K+that moves membrane away from 0mv (hyperpolarization)

• local changes in the membrane that fade over distance
• all cells experience graded potentials when stimulated
• graded potentials by themselves cannot trigger activation of large neurons and muscle fibers

• det. whehter or not an action potential will occur
• some are excitatory (depolarizing) white others are inhibitory (hyperpolarizing)
• a threshold level of depolarization ned to be reached for action potential to occur?

change in the membrane that travels the entire length of neurons

• depolarization to threshold (-60)
• activation of sodium channels and rapid depolarization (10)
• inactivation of sodium channels and activation of potassium channels (30)
• closing of potassium channels (90)
• return to resting potential

local changes in the membrane in one site result in the activation of voltage gated channels in the next adjacent site 

• saltagtaory propagation: occurs in myelinated axons and is much faster than continous conduction
• continuous propagation or conduction occurs in unmyelinated fibers and is relatively slow