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Spinal Cord
- Connects to brain thru Foramen Magnum
- Encircled by vertebral column
- Contains aprox 100 million neurons
- 31 pairs of Spinal Nerves
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Ganglia
Small masses of nervous tissue consisting primilary of neuron cell bodies located outside the brain & spinal cord (PNS)
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Enteric Plexuses
- Extensive network of neurons that help regulate the digestive system
- Located in walls of GI tract
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Nervous System's two main subdivisions are...
- Central Nervous System (CNS)
- Consists of brain & spinal cord
- Peripheral Nervous System (PNS)
- Consists all nervous tissue outside CNS
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Nerve Cells aka ________ possess Electrical Excitability which is...
Neurons
Ability to respond to stimulus & convert it into an action potential
Stimulus - Any change in enviroment strong enough to initiate an action potential
- Action Potential aka Nerve Impulse
Electrical signal that propogates (travels) along surface of neuron
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Three main parts of a neuron are
- Cell Body aka Perikaryon or Soma
- Contains nucleus surrounded by cytoplasma
- Has lysosomes, mitochondria, golgi complex
- Contain Nissl Bodies
- Dendrites
- "Little trees"
- Receives impulses
- Cytoplasm contain nissel bodies, mitochondria
- Axon
- Popogates nerve impulses toward another neuron
- Long, thin, cylindrical
- Joins cell body at cone shaped elevation called Axon Hillock
- No protein synthesis
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The cytoplasm of an Axon is called ________. It is surrounded by a plasma membrane called ___________.
Axoplasm
Axolemma
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Side braches along the length of an axon are...
Axon Collaterals
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Site of communication between two neurons or between a neuron & effector cell is a ___________
Synapse
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The tip of axon terminals can swell into bulb-shaped strctures called __________ or exhibit a string of swollen bumps called ________. Both contain ________, tiny membrane enclosed sacs that store a chemical ________.
- Synaptic End Bulbs
- Varicosities
- Synaptic Vesicles
- Neurtransmitter
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GABAergic neurons located in the cerebellum
Purkinje cells aka Purkinje neurons
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a type of neuron found in areas of the brain including cerebral cortex and sometimes in the hippocampus, and in the amygdala
Pyramid Cells
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Sensory, Motor, & Inter-neurons
- Also called...
- Afferent, Efferent, & Association Neurons
- Sensory / Afferent
- Contain sensory receptors
- Conveys action potentials to CNS thru cranial or spinal nerves
- Most are unipolar
- Motor / Efferent
- Convey action potentials away from CNS to Effectors (muscles & glands)
- Must are multipolar
- Interneurons / Association Neurons
- Located within CNS between sensory & motor neurons
- Process incoming sensory info & elicit motor response
- Most are multipolar
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Neuroglia or Glia
- Make up half volume of CNS
- Smaller than neurons & more numerous
- Do NOT generate / propagate action potentials
- Can multiple & divide in mature nervous systems
- Multiple to fill in spaces formerly occupied by neurons
- Gliomas - Brain tumors derived from glia
- Grow rapidly & highly malignant
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Neuroglia of the CNS are...
Neuroglia of the PNS are...
- Astrocytes
- Oligodendrocytes
- Microglia
- Ependymal
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Astrocytes
- Neuroglia found in CNS
- Star shaped cells
- Largest & most numerous of neuroglia
- Microfilaments give strength to enable supporting neurons
- Wrap around blood capparies isolating neurons from harmful substances in blood
- Blood-Brain Barrier of endothelial cells
- Regulate growth, micrgration, & interconnection
- Maintain chemical enviroment for nerve impulses
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Myelin Sheath
- Multilayered lipid & protein covering around axons
- Insulates them for increased speed of nerve impulse conduction
- Such axons are Myelinated
- Amount of myelin increases form birth to maturity
- Presence of myelin increases speed of nerve impulse conduction
- Example:
- Infant's response to stimuli not as rapid nor coordinated as those of an older child because myelination still in progess at infancy
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Oligodendrocytes
- Neuroglia found in CNS
- Resemble astrocytes but smaller
- Form & maintain Myelin Sheath
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Microglia Cells
- Neuroglia found in CNS
- Small cells with spinelike projections
- Function as phagocytes removing debris & danaged nervous tissue
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Ependymal Cells
- Neuroglia found in CNS
- Cuboidal to columnar arranged in single layer
- Have microvilli & cilia
- Line ventricles of brain & central canal
- Produce & mointor CSF
- Form blood-cerebrospinal fluid barrier
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Schwann Cells
- Neuroglia found in PNS
- Form myelin sheath around axons
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What is the difference between how Schwann Cells & Oligodendrocytes myelinate?
- Schwann Cells
- Located in PNS
- Each Schwann Cell myelinates a single axon
- Can enclose many unmyelinated axons
- Nodes of Ranvier appear at intervals along axon
- Participate in axon regeneration
- This is why axon regeneration easier in PNS
- Oligodendrocytes
- Locatedin CNS
- A single oligodendrocyte myelinates parts of several axons
- No neurolemma is present
- Thus injury axons in CNS display little regrowth post injury
- Nodes of Ranvier are present but in fewer numbers
Notes of Ranvier - Gaps in myelin sheath
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Satellite Cells
- Neuroglia located in PNS
- Flat cells surround cell bodies of neurons
- Provide structural support
- Regulate exchanges of materials between neuronal cell bodies & interstitial fluid
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Bundle of axons located in the PNS is called a ______, in the CNS is called a ______
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White Matter vs Gray Matter
- White Matter
- Composed of mostly myelinated axons
- White color comes from myelin
- Gray Matter
- Neuronal cell boies, dendrites, unmyelinated axons, axon terminals, & neuroglia
- Appears gray because of Nissl Bodies
- Blood vessels are present in both
- In spinal cord, gray matter looks like "H" or butterfly
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Cluster of neuronal cell bodies in the PNS is _______, in the CNS is ________
- Ganglion (singular: Ganglia)
- Nucleus
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Three subdivisions of the Peripheral Nervous System (PNS) are
- Somatic Nervous System (SNS)
- Consist of sesory neurons conveying info\
- Motor neuron send impulses from CNS to ONLY skeletal muscles
- Voluntary
- Autonomic Nervous System (ANS)
- Sensory & motor neurons conveying info & conducting nerve impulses
- Motor portion of ANS consist of sympathetic & parsympathetic divisions
- Involuntary
- Enteric Nervous System (ENS)
- Consist of neurons in enteric plexuses
- Extend length of GI tract
- Many function indepdently of ANS & CNS
- Do communicate with CNS via sympathetic & parasympathetic neurons
- Govern contractions of HI tract smooth muscle popeling food
- "Brain of the Gut"
- Involuntary
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The motor part of the Autonomic Nervous System are
- Sympathetic
- Increase heart rate
- "Fight or Flight" responses
- Parasympathetic
- Decrease heart rate
- "Rest & Digest" activities
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Demyelination
- Loss of destruction of myelin sheath around axons
- Results from disorders such as MS or Tay-Sachs
- May result from radiation of chemo
- Any single episode of demyelination may cause deterioration of affected nerves
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Acetylcholine (ACh)
- Neurotransmitter released by PNS neurons
- Excitatory
- Slows heart rate
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Glutamate (Glutamic Acid) & Asparate
- Neurotransmitter
- Excitatory effects
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Norepinephrine (NE) & Epinephrine
- Biogenic Amine neurotransmitter
- Arousal, dreaming, regulating mood
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Dopamine
Active during emotional responses, addictive behavior, pleasurable experiences
- Parkinson's Disease
- Muscular stiffness is ude to degeneration of neurons that release dopamine
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Catecholamines
- Group of neurotransmitters include amino group NH2 & catechol ring
- Norepinephrine, Epinephrine, Dopamine
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Serotonin aka 5-Hydroxytrptamine (5-HT)
- Concertrated in neurons in brain called raphe nucleus
- Involved in sensory perception, temperature regulation, mood control, appetite, & sleep induction
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Endorphins & Dynorphins
- Neuropeptide
- Opiod Peptides
- Body's natural painkillers
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