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A & P 1551 - Nervous Tissue & The Spinal Cord and Spinal Nerves-College of Dupage

College of Dupage: A & P 1551; Skarbek; Chapters 12 & 13 (Principles of A & P, 12th edition, Tortora)
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Three functions of Nervous System:
Sensory, integrative & motor function
Sensory Function:
sensory receptors that detect stimuli
Integrative function:
Processing of information
Motor function:
carries out the responses
Two divisions of Neverous system:
Central and Peripheral Nervous Systems
Central nervous system:
Made up of brain and spinal cord
Peripheral Nervous system:
all nervous tissue outside the central nervous system; two catagories
Two categories of Peripheral Nervous system:
Somatic and autonomic nervous systems
Somatic nervous system:
mostly responsible for voluntary functions; skeletal muscles
Autonomic Nervous System:
involuntary automatic functions; heart, digestion, respiration; to subdivisions
Two subdivisions of autonomic nervous system:
Sympathetic and parasympathetic divisions
Neurons:
one nerve cell
Cell body:
Part of neuron that has nucleus, cytoplasm and typical organelles
Dendrite:
part of neuron-projections that send messages to the cell body
Axon:
part of neuron-long projection that sends messages away from cell body; every neuron has one one "of these"
Axon terminals:
part of neuron-branches at end of axon
Synaptic end bulbs:
part of neuron-bulb shaped structures filled with neurotransmitters
Astrocytes:
a type of neuroglia of CNS that physically protects neurons ; plays role in learning and memory
Oligodendrocytes:
a type of neuroglia of CNS; responsible for productin the myelin sheath
Microglia:
a type of neuroglia of CNS; phagocytes that help fight foreign substances
Ependymal Cells:
a type of neuroglia of CNS; produce cerebrospinal fluid; helps with circulation
Schwann cells:
type of neuroglia of PNS; cells that surround axons
Satellite cells:
type of neuroglia of PNS; provides structural support; involved with nutrient exchange between cells and interstitial fluid
Two types of neuroglia that produce myelin sheaths:
Schwann cells and oligodendrocytes of CNS
Myelin sheath:
A multi-layered lipid and protein covering that surronds axons
Neurolemma:
the outer nucleated cytoplasmic layer of the schwann cell, which encloses the myelin sheath
Nodes of ranvier:
gaps in myelin sheath that occur between schwann cells; increases nerve signal transmission
Myelin:
white fatty substance produced by oligodendrocytes and schwann cells
Potassium ion:
K+
Sodium ion:
Na+
Ion channels:
4 types of chanels that allow ions (K+ and Na+) to pass in and out of a cell
Electrochemical gradient:
Ions move from areas of higher concentration to areas of lower concentration
Resting membrane potential:
an excess of unused ions that store potential energy, that line the outer wall of the plasma membrane
Unequal distribution of ions in Extra Cellular Fluid & Cytosol:
contributes to resting membrane potential; plasma membrane has more K+ leakage channels that allow for more K+ to diffuse down concentration gradient out of cell into ECF
Inability of anions to leave cell:
contributes to resting membrane potential because they are attached to nondiffusible molecules such as ATP
Electrogenic nature of Na/K ATPases:
contributes to resting membrane potential by pumping out Na+ as fast as it leaks in
The two main phases of an action potential:
depolarizing and repolarizing phases
Depolarizing Phase:
negative membrane potential becomes less negative, reaches 0, then becomes positive
Repolarizing Phase:
membrane potential is restored to resting state
Refractory period:
perior of time after action potential when another impulse can not be generated
Two types of propagation of nerve impulses:
continuous and saltatory conduction
Continuous conduction:
step by step depolarization and repolarization of each adjacent segment of the plasma membrane
Saltatory conduction:
special mode of action potential propagation that occurs along myelinated axons because of uneven distriution of voltage-gated channels
Electrical Synapses:
have gap junctions that have connexons which connect cytosol of two cells, which allows faster communication
Chemical synapses:
synaptic cleft w/neurotransmitters that chemically transmit messages from one neuron to another
Excitatory and Inhibitory postsynaptic potentials:
are types of action potentials that neurotransmitters will cause
Excitatory postsynaptic potential:
causes excitation of the effector (which is the structure that carries out the response)
Inhibitory postsynaptic potential:
Neurostansmitter moves post synaptic further away from threshold
Acetylcholine:
A small molecule neurotransmitter that works at the neuromuscular junction; excitatory or inhibitory
Two excitatory Amino Acids:
glutamate and asparate; act in CNS
Two inhibitory Amino Acids:
Gamma aminobutyric acid and glycine; act in CNS
Biogenic amines:
modified and decarboxylated amino acids that excite or inhibit receptors
Norepenephrine:
excitatory or inhibitory; role in regulating mood
Dopamine:
excitatory or inhibitory; very active in emotional responses, including addictive behaviors
Serotonin:
excitatory or inhibitory; involved in mood, sleep cycle, appetite , sensory perception
Protective structures of the spinal cord:
Vertebral column and meninges
Vertebral column:
provides bony protection
Meninges:
connective tissue of spinal cord
Dura mater:
outer layer of the meninges; dense irregular connective tissue
Arachnoid mater:
middle layer of the meninges; made of collagen and elastic fibers
Pia Matter:
inner most layer of meninges; made of bundles of collagen fibers and elastic fibers; helps supply blood to cord
Internal anatomy of the spinal cord:
Anterior median fissure, posterior median sulcus, Central canal, Gray matter, White matter
Anterior median fissure:
very deep groove of internal spinal cord
Posterior median sulcus:
very shallow groove of internal spinal cord
Central canal:
tunnels through center of spinal canal; filled with CSF
Anterior gray horns:
gray matter of spinal cord containing somatic motor nuclei
Posterior gray horns:
gray matter of spinal cord containing somatic (voluntary) and automatic (involuntary) sensory nuclei
Lateral gray horns:
gray matter of spinal cord present in thoracic area, upper lumbar and sacral parts of spine; autonomic motor nuclei
White matter:
tracts that extend entire length of spinal cord; bundles of axons faciliate more efficient communication;
Sensory tracts of white matter:
carry information toward the brain
Motor tracts of white matter:
carry information away from the brain
Three tracts of white matter:
Anterior, posterior and lateral white columns
Formation of spinal nerves:
the anterior and posterior roots unite to form the spinal nerves
Posterior root of spine:
contains only sensory axons
Anterior root of spine:
contains only motor axons
Connective tissue of spinal nerves:
Epineurium, Perineurium, Fascicles & Endoneurium
Endoneurium:
connective tissue wrapping of individual axons (neurons)
Fascicles:
bundles of wrapped axons
Perineurium:
connective tissue that wraps fascicle of spinal nerves
Epineurium:
connective tissue wrapping of entire spinal nerve
Rami:
branches of spinal nerves
Posterior ramus:
branch of spinal nerve that serves muscles in the skin of posterior trunk
Anterior Ramus:
branch of spinal nerve that serves anterior trunk and some structures of the limbs
Meningeal branch:
branch of spinal nerves that enters and exits vertebral cavity to supply vetebrae, ligaments, blood vessels of spinal cord
Plexuses:
divisions of the anterior rami
Intercostal nerves:
Anterior rami of spinal nerves T2-T12
Lateral & Anterior spinothalamic tracts:
convey impulses for temperature sensation, pain, etc
Proprioception:
perception of the position of a body part, independent of vision
Discriminative touch:
ability to feel what part of body is being touched
Two point discrimination:
ability to distinguish the touching of two points of body, even when close together
Integration centers:
where info is processed by interneurons, determines response and sends to motor neurons
Direct pathways:
send impulses for precise voluntary movements
Three Direct Pathways:
lateral corticospinal , anterior corticospinal tract, and cortiobulbar tract
Indirect pathways:
involved with coordination of body movements, skeletal muscle tone, posture & equilibrium
Three Indirect Pathways:
Rubrospinal, tectospinal and vestibulospinal tracts
Reflex:
fast automatic sequence of actions in response to a stimulus
Spinal reflex:
integration takes place in spinal cord; no brain process required
Cranial reflex:
integration takes place in lower portion of brain; tracking portion of reading
Somatic reflex:
involves contraction of skeletal muscles
Autonomic visceral reflex:
reflexes not consciously perceived; heart rate
Mechanoreceptors:
sensory receptor sensitive to mechanical stimuli, stretching of blood vessels, stretching or bending of deformation of tissue
Thermoreceptors:
sensory receptor that responds to change in temperature
Nociceptors:
sensory receptor that responds to pain
Photoreceptors:
sensory receptor that responds to light
Chemoreceptors:
sensory receptor that responds to chemicals
Osmoreceptors:
sensory receptors responds to changes in osmotic pressure
Sensory Neurons:
carries sensory information
Integration center:
where information is processed and decisions are made
Motor neurons:
carries response information to effectors
Effector:
Part of body that carries out responses
Three protective coverings of brain:
dura mater, arachnoid mater and pia mater