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What is the nervous system anatomically and fuctionally?

Central nervous system (CNS)
CNS is composed of the brain and spinal cord

Peripheral nervous system (PNS)
PNS consists of cranial nerves from brain and Spinal Nerves From spinal cord
Somatic fibers connecting to skin and skeletal muscles and autonomic fibers connecting to vicsera divisions


What does the nervous tissue do?

Nervous tissue is excitable.
Conduct an electrical impulse also known as an “action potential” to communicate with other nerves, muscles, or glands


What does the brain do?

Thought, emotions, behavior, and memory


What does the spinal cord and nerves do?

Process stimuli that may be harmful and the body responds with a protective reflex action


What do the sensory receptors do?

Sensory receptors
Smell, touch, sight, and hearing
Regulating appetite and body temperature


What do neurons do?

Transmit electrochemical messages
Called nerve impulses or action potentials
To other neurons and effectors
Permanent cells
Do not have the ability to divide
Cell body, cell membrane, nucleus, and many of the same organelles found in other types of cells


What do axons do?

Usually only one axon
Carries an action potential away from the cell body
In the CNS, these nerve fibers form tracts
In the PNS, they form nerves


What do dendrites do?

Usually many dendrites from a single cell body
Transmit an electrical signal toward the cell body


What are Multipolar neurons ?

Most numerous
One axon and many dendrites
Brain and spinal cord
Efferent (motor) neurons - Carry messages from the CNS to the muscles and glands in the PNS
Interneurons or association neurons - Connect sensory and motor neurons and direct the impulse to other areas of the brain or spinal cord


What are bipolar neurons?

Fewest in number
One dendrite and one axon
parts of nose, eyes and ears
Afferent (sensory) Carry impulses from the periphery to the CNS


What are unipolar neurons?

Single extension that divides into two processes
Found of ganglia outside the brain and spinal cord
Afferent (sensory) Carry impulses from the periphery to the CNS


What are NeurOglia?

Also referred to as neuroglial cells or simply “glia”
Do not transmit impulses
Act as supportive cells for other neurons
Able to reproduce and replace themselves


What are astrocytes?

Neuroglia in CNS
star shaped between neurons and blood vessels
Functions - structural support, forms scar tissue, transports, communicates


What are oligiodendrocytes?

Neuroglia in CNS
star shaped not as common
Produce nerve growth factors, myelin sheaths in the brain and spinal cord


What are microglia?

Neuroglia in CNS
Small cells , found throughout CNS
Structural support and phagocytosis (immunity)


What are ependyma?

Neuroglia in CNS
cuboidal and columnar cells in lining of ventricles of brain form a porous layer where substances are able to diffuse between brain fluid, spinal cord and CSF


What are Schwann cells?

Neuroglia in PNS
Cells with lipid rich membranes wrapped around axons
F- speed neurotransmission


What are satellite cells?

Neuroglia in PNS
Cubodial cells that surround cell bodies of neurons in ganglia
Support ganglia in PNS


What is Myelin?

Fatty substance which insulates axons
Allows them to send nerve impulses more rapidly than that of unmyelinated nerves
When coated these axons are referred to as “white matter”.
Unmyelinated nerve cell bodies make up the “gray matter”


What is nerve transmission?

-action potential travels down an axon and reaches the synaptic knob (vesicles that are either excitatory or inhibitory) at the end of each axon branch
-cause the vesicles to fuse with the presynaptic membrane of the axon terminal
Causing the neurotransmitters to be released into a space called the synaptic cleft
-Neurotransmitters then combine with receptors on the postsynaptic membrane
Allows the impulse to continue on the structures on the other side of the synaptic cleft


What is Acetylcholine?

In CNS - control skeletal muscle actions
in PNS - stimulates muscle contractions


What is norepinephrine?

Biogenic amines
CNS- creates sense of well being- low levels may cause depression
PNS- May excite or inhibit autonomic actions


What is dopamine?

Biogenic amines
CNS- Creates sense of well being. Not enough of it leads to Parkinsons
PNS - Limited actions in autonomic nervous system


What is seratonin?

Biogenic amines
CNS - Inhibitory . sleepyness, blocked by LSD. enhanced by antidepressants


What is histamine?

Biogenic amines
CNS - Release in hypothalamus promotes alertness


What are amino acids in the CNS?

GABA (inhibit), Glutamate (excitatory),


What are some neuropeptides ?

Endorphins (cns - inhibitory reduce pain), Substance P - PNS (Excitatory - pain perception)


What are some gases?

Nitric oxide - CNS - memory
PNS - vasodialation


What is action potential propagation?

Speed of conductance down an axon
Larger-diameter axon will conduct an impulse faster than smaller diameter axons
Myelinated nerve will conduct an action potential faster than an unmyelinated axon
In myelinated nerves, there are bare areas on the axon called Nodes of Ranvier.
Action potential jumps from node to node.
Called saltatory conductance


What is the Blood brain barrier?

Protects the brain by not allowing harmful substances to enter it from the blood
Tight junctions between endothelial cells of the brain capillaries
Astrocytes help maintain the tight junctions
BBB restricts most large molecules and hydrophilic substances from entering the cerebrospinal fluid (CSF
Develops early in embryonic life
CNS begins as a simple tubelike structure called the neural tube