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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

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