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

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College of Dupage: A & P 1551; Skarbek; Chapters 12 & 13 (Principles of A & P, 12th edition, Tortora)

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

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