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79 terms

A&P Chapter 11

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Nervous System Functions
Sensory Input, Integration, Control of Muscles and Glands, Homeostasis, Center for Mental Activities
Central Nervous System
brain and spinal cord, encased in bone, processes integrates stores and responds to information from the PNS
Peripheral Nervous System
nervous tissue external to the CNS, consists of sensory receptors and nerves, detects stimuli and transmits info to the CNS and receives information from the CNS
Sensory Receptors
part of PNS, ending of neurons or separate, specialized cells that detect such things as temperature, pain, touch pressure, light, sound,and odors
Nerve
part of PNS, a bundle of axons and their sheaths that connect CNS to sensory receptors muscles and glands
Cranial Nerves
originate from the brain; 12 pairs
Spinal Nerves
originate form spinal cord; 31 pairs
Ganglion
part of PNS, collection of neuron cell bodies located outside the CNS
Plexus
part of PNS, extensive network of axons and sometimes neuron cell bodies, located outside the CNS
Sensory Division
division of PNS, afferent, transmits action potentials from receptors to CNS
Motor Division
division of PNS, efferent, transmits action potentials from CNS to effectors
Somatic Nervous System
system of motor division, innervates skeletal muscles
Autonomic Nervous System
system of motor division, innervates cardiac muscle, smooth muscle, and glands, subconscious control, two neuron system-from CNS to ganglion and from ganglion to effector
Sympathetic Nervous System
system of autonomic nervous system, always active at basal levels but is most active during states of heightened stress, fight or flight response
Parasympathetic Nervous System
system of autonomic nervous system, regulates resting functions
Enteric Nervous System
system of autonomic nervous system, located with in and controls the digestive tract
Neurons
excitable cells that receive stimuli and transmit action potentials to other neurons or effector organs
Cell Body (Soma)
contains nucleus, a nucleolus, and nissl substance (site of protein synthesis), golgi apparatus mitochondria and other organelles, clusters in CNS called nuclei, in PNS ganglia
Dendrites
short branched cytoplasmic extensions of the cell body, conduct electric signals toward the cell body
Axons
cytoplasmic extensions of the cell body, transmit action potentials away from cell body to other cells
Trigger Zone
part of neuron where axon originates, action potential generated
Presynaptic Terminal
branched terminal of an axon, form sun apses, contain vesicles with neurotransmitters
Sensory (afferent) Neurons
conduct action potentials toward the CNS
Motor (efferent) Neurons
conduct action potentials away from CNS towards muscle or glands
Interneurons (association)
conduct action potentials from one neuron to another neuron within the CNS
Multipolar
neurons with several dendrites and a signal axon, interneurons and motor neurons
Biopolar
neurons with a single axon and dendrite, components of sensor organs
Unipolar
neurons with a single axon, most sensory neurons
Neuroglia
provide a supportive scaffolding for neurons, segregate and insulate neurons, guide young neurons to proper connection, promote health and growth
Neuroglia of CNS
Astrocytes, Microglial, Ependymal cells, Oligodendrocytes
Neuroglia of PNS
Satellite cells, Schwann cells
Astrocytes
neuroglia of CNS, clings to neurons and cover capillaries, support and brace neurons and blood vessels, influence the functioning of the blood brain barrier
Blood Brain Barrier
protects neurons from toxins, allows exchange of nutrients and waste between neurons and blood, prevents fluctuations of blood from affecting brain
Ependymal Cell
neuroglia of CNS, line the ventricles of the brain and the ventral canal of the spinal cord, some form choroid plexuses; found in regions of ventricles, secrete cerebrospinal fluid, cilia help move fluid through brain cavities
Microglia
neuralgia of CNS, specialized macrophages, become mobile and phagocytic when inflammation, phagocytes monitor the health of neurons
Oligodentrocytes
neuroglia of CNS, forms myelin sheaths around the axons of CNS neurons, can form sheaths around several axons
Schwann Cells
neuroglia of PNS, from myelin sheath around part of the axon of PNS neuron, unlike oligodentrocytes only around portion of one axon
Satellite Cells
neuroglia of PNS, support and nourish neuron cell bodies within ganglia, protect neurons from heavy metal poisons by absorbing them and reducing their access to neuron cell bodies
Myelinated Axon
plasma membrane of schwann cells or oligodentrocytes repeatedly warp around segment of axon to form myelin sheath, protects electrically insulates increases speed of impulse and conducts action potential rapidly
Node of Ranvier
gap in myelin sheath
Unmyelinated Axon
rest in invaginations of schwann cells and oligodentrocytes, surround each axon but do not wrap around it, conduct action potentials slowly
White Matter
nervous tissue, consists of myelinated axons, propagates action potentials, forms nerve tracts in CNS and nerves in PNS
Gray Matter
nervous tissue, collection of neuron cell bodies, unmyelinated axons, dendrites, neuroglia, forms cortex and nuclei in CNS and ganglia in PNS, integrative functions
Action Potential
Electrical signals produced by cells, can result in sensation of sight, hearing or touch, complex mental activities;conscious thought, memory, emotions, contraction of muscles, and secretion of glands
Electrical Properties
properties of cells resulting from; ionic concentration differences across membrane, permeability of membrane
Na, Ca, and Cl
greater concentration outside cell, make it positive
K and negative molecules
greater concentration in the cell, make it negative
Concentration Gradient
results from Na-K pump and permeability characteristics of membrane
Na-K Pump
moves ions by active transport, 2 K into cell, 3 Na out of cell
Permeability Characteristics
Leak channels, and Gated Ion channels
Leak Channels
located in membrane, always open, more K than Na, membrane more permeable to K than Na when at rest
Gated Ion Channels
open and close in response to stimuli, change the permeability of the cell membrane when open, include ligand gated, voltage gated, and other ion channels
Ligand Gated Ion Channels
open or close with the binding of a specific ligand, common in nervous and muscle tissue and glands
Voltage Gated Ion Channels
open and close in response to small voltage changes across the plasma membrane, common in nervous and muscle tissue
Other Gated Ion Channels
open and close in response to physical deformation of receptors, touch and temperature receptors
Depolarization
decrease in resting membrane potential caused by; decrease in K concentration gradient or membrane permeability, increase in membrane permeability to Na or Ca, decrees in extracellular Ca concentrations
Hyperpolarzation
increase in resting membrane potential cause by; increase in K concentration gradient or membrane permeability to K or Cl, in membrane permeability to Na, increase in extracellular Ca concentrations
Graded Potentials
small changes in resting membrane potential, confined to small area of plasma membrane, can summate
Depolarization Phase
inside of the membrane becomes more positive, Na diffuses into the cell through voltage gated ion channels
Repolarization Phase
return of the membrane potential toward the resting membrane potential, voltage Na channels close, voltage K channels open K diffuses out
Afterpotential
brief period of hyper polarization following repolarization
Absolute Refractory Period
time during and action potential when a second stimulus cannot initiate another action potential, also prevents reversal of direction of action potential
Relative Refractory Period
time during which a stronger than threshold stimulus can evoke another action potential
Action Potential Frequency
number of action potentials produced per unit of time in response to stimuli, proportional to stimulus strength and size of graded potential
Subthreshold Stimulus
causes graded potential
Threshold Stimulus
causes single action potential
Submaximal Stimulus
action potential frequency increases as the strength of the stimulus increases
Maximal Stimulus
produces a maximum frequency of action potential
Saltatory Conduction
in myelinated axons, action potentials jump from one node of randvier to the next
Synapse
junction between two cells where communication takes place, site where acton potential in one cell causes action potential in another cell
Presynaptic cell
cell that transmits a signal towards a synapse
Postsynaptic cell
cell that receives a signal
Electrical Synapse
type of synapse, action potentials are conducted rapidly between cells allowing for synchronized activity among a group of cells, found in cardiac muscle
Chemical Synapse
type of synapse, composed of presynaptic terminals, postsynaptic membranes, and synaptic cleft, found in skeletal muscles
Presynaptic Terminals
part of chemical synapse, the enlarged end of the axon that contains synaptic vesicles
Postsynaptic membranes
part of chemical synapse, contain receptors for the neurotransmitters
Synaptic Cleft
the space that separates the presynaptic and postsynaptic membrane
Spatial Summation
occurs when two or more presynaptic terminals simultaneously stimulate a postsynaptic neuron
Temporal Summation
occurs when two or more action potentials arrive in succession at a single presynaptic terminal