Flashcards in Nervous System Deck (126):
What are the two major parts of the nervous system?
- Peripheral NS
- Central NS
What are the two parts of the peripheral nervous system?
- Somatic NS
What are the two parts of the autonomic nervous system?
- Sympathetic NS
- Parasympathetic NS
What are the three parts/regions of the brain?
What are the two parts of the forebrain?
- telencephalon ( Cerebral cortex, basal ganglia, hippocampus, amygdala)
- Diencephalon (Thalamus, hypothalamus)
What are the two parts of the hindbrain?
- Metencephalon (Pons, Cerebellum)
- Myelencephalon (medulla)
What is found in the midbrain?
Mesencephalon (Tectum, tegmentum)
What are two types of nervous tissue?
What are the types of neurons?
What are the types of neuroglia in the CNS?
What are thetypes of neuroglia in the PNS?
- Schwann cells
- Satellite cells
What is grey matter?
parts of CNS rich in cell bodies but limited numbers of myelinated axons
What is white matter?
region rich in myelinated axons
What components of the CNS have ectodermal origins?
True or false? Components of the CNS that have ectodermal origins are sensitive to hypoxia
What components of the CNS have mesodermal origins?
- Vascular Endothelium
True or flase? Components of the CNS that have mesodermal origins are sensitive to hypoxia
False. They are not as sensitive to hypoxia as components with ectodermal origins
What is another name for the cell body of a neuron?
How are Neurons distributed?
- in Layers
- In Ganglia (PNS)
- In Nuclei (CNS) (just like ganglia but in the CNS)
What are the structural characteristics of the Neuron Soma?
- Euchromatic nucleus with prominent nucleolus
- Basophilic cytoplasm = Nissl substance: RER and ribosomes
- They are long living cells
What is the wear and tear (age) pigment of neurons?
What is neuropil?
everything surrounding neurons
What do the dendrites of a neuron do?
recieve stimuli at synapses
What do the axons of a neuron do?
transmit signals and terminate on other neurons (dendrites), skeletal muscle, smooth muscle, cardiac muscle, or glands. (some secrete hormones into a blood capillary - special case -- neurosecretion
What is it called when neurons make contact with other neurons and/or effector cells?
What are the different shapes of a perikaryon? Where are these shapes usually found?
- Round or oval (pyriform) - pseudounipolar neurons and purkinje cells in cerebellum
- Pyramidal (pyramid shaped) - in brain cortex
- Stellate - multipolar motor neurons in spinal cord
what is found in the cell body (soma/perikaryon) of a neuron?
Round nucleus, nucleolus, nissl substance, golgi apparatus, mitochondria, lipofuscin granules, lysosomes, axon hillock
What are the parts of an axon?
- telodendron (location of synapse)
What is an axosomatic synapse?
synapse on cell body
What is an axodendritic synapse?
synapse on a dendrite
What is an axoaxonic synapse?
synapse on axon hillock (rare)
What arethe three parts of a nerve synapse?
- Presynaptic part (termination of axon) (Bouton terminaux)
- Intersynaptic cleft
- Postsynaptic part (dendritic thorn)
What are the types of synaptic vesicles and what do they contain?
- Small, pale, and round - contain acetylcholine
- Large dense core vesicles - contain noradrenaline + adrenaline (norepinephrine and epinephrine)
- Pale, oval vesicles - contain GABA or glycine
- Other vesicles - contain other neurotransmitters (eg: dopamine)
What neurons release acetylcholine into the synaptic cleft and what does it do?
- stimulates muscle contraction
What do the vesicles of stimulatory synapses contain?
What do the vesicles of inhibitory synapses contain?
What nerve endings are free/naked?
- nociceptors (pain, itch)
- Thermoreceptors (temp.)
What nerve endings are encapsulated? What do these nerve endings do/sense?
- Mechanoreceptors for touch and pressure
-- Meissner's corpuscle (fine touch)
-- Krause corpuscle (pressure)
-- Pacinian corpuscle (deep pressure)
-- Gogli organ (concious proprioception)
-- Muscle spindle (concious proprioception
Which nerve endings have an onion appearance?
Where are pacinian corpuscles found?
found in skin, pancreas (cats), bulbs of horse heels, mesenteries, deep CT, tendons
Where are golgi organs found? What do they do?
located at the insertion of skeletal muscle fibers into the tendons
- Proprioceptive sensory receptor organ/senses stretching
What is a muscle spindle?
a specialized sensory receptor for muscle stretch and position sense, as related particularly to unconscious maintenance of skeletal muscle tone and proper balance of postural muscle activity
What is the structure of a muscle spindle?
a number of small specialized infrafusal muscle fibers (nuclear bag fibers and nuclear chain fibers) are surrounded by a capsule of connective tissue within the perimyceum
What are neuroglia?
supporting cells within the brain
What are the types of neuroglia?
- Ependymal cells
True or false? Neuroglia outnumber neurons.
What are the two types of astrocytes?
- protoplasmic (grey matter)
- Fibrilar (white matter)
What are astrocytes?
the CNS counterparts of the fibroblast
- important in healing
What are the functions of an astrocyte?
- transport of nutrients
- Maintenance of extracellular matrix ion content
- Neurotransmitter uptake
- Part of blood brain barrier
- Antigen presentation
What are oligodendrocytes? What do they do?
small dark nuclei (between myelin sheaths or around neurons) that develop and maintain myelin in the CNS
What can oligodendrocytes be destroyed by? What does it result in?
viruses/toxins resulting in primary demyleination
What are microglia?
resident macrophages of the CNS that are derived from blood-borne monocytes.
- often have cytoplasmic vacuolation due to ingestion of cellular debris
What are gitter cells?
Microglia that have been activated during necrosis or inflammation
What do microglia look like and what do they originate from?
they are the smallest cells and have dark elongated nuclei
- Mesodermal origin
What is the function of a microglial cell?
- Eg lipid
- Myoeophagues/gitter cells
What are myeolophages?
activated microglial cells in a myelin sheath
What are ependymal cells?
ciliated cuboidal cells lining neural canal, ventricles, choroid plexus, central canal of spinal cord
- Aid formation of the CSF (cerebrospinal fluid)
Capillaries with overlying ependymal cells form ____1____ and produce ____2____.
1. choroid plexus
2. cerebrospinal fluid
What do central canal ependymal cells have and why?
cilia to circulate CSF (cerebrospinal fluid)
What synthesizes myelin in the CNS? PNS?
PNS: Schwann cells
How many internodes do oligodendrocytes connect to? Schwann cells?
What is myelin? What does it do?
complex phospholipid, lamellar arrangement around axon
- 75% lipid, 25% protein
- Responsible for conduction and speed of impulses
- confers white color to brain and cord (white matter)
Are non-myelinated autonomic nerve fibers wavy or straight?
Are myelinated somatic nerve fibers wavy or straight?
True or false? Myelin is almost complete in the foal at birth but not in mice at birth.
True - amount of myelin reflects the mobility of the animal at birth
What are peak periods of myelination?
How much % of cardiac output does the brain receive? Total body oxygen consumption? Total body glucose utilization?
Cardiac output = 15%
Body O2 = 20%
Body Glucose = 25%
What does white matter contain?
contains myelinated axons and glial cells, blood vessels
How is white matter arranged in the spinal cord and brain?
Spinal cord: in the periphery
Brain: in the center
What does grey matter contain?
neurons, glial cells, and axons, blood vessels
How is grey matter arranged in the spinal cord and brain?
Spinal cord: at the center
Brain: at the periphery
What does the cerebrum arise from?
Pia matter is directly adherent to the _____________
Vessels within the _______1_______ course over the pia matter and dive into the outer grey matter
Elevations of the cerebrum are called what? Depressions?
Elevations = gyri
Depressions = sulci
What is another name for the forebrain, hind brain and midbrain?
Forebrain = proencephalon
Midbrain = mesencephalon
Hindbrain = rhombencephalon
What is another name for the cerebral cortex?
What are the layers of the neocortex?
- lamina zonalis
- lamina granularis externa
- lamina pyramidalis externa
- lamina granularis interna
- lamina pyramidalis interna
- lamina multiformis
What does the hippocampus and detnate gyrus do?
portion of the brain that is involved with laying down memory tracks
- contains numerous glutamate receptors
True or false? The hippocampus and dentate gyrus are sensitive to hypoxia and hypoglycemia.
What is the cerebellum involved in?
coordination of body movements
What are the elevations of the cerebellar parenchyma called?
What are the depressions between the folia of the cerebellum called?
What are the layers of the cortex of the cerebellum? What is found in each layer?
- Molecular layer - basket cells in stratum coleculare
- Purkinje cell layer (ganglionic layer) - purkinje cells in stratum gangliosum
- Granular cell layer - granule cells in stratum granulosum
- White matter core - myelinated nerve fibers
What are the only nerve fibers leaving the cerebellum?
efferent neurons of purkinje cells
Is the cortex of the cerebelum white or grey matter?
What is present on the fetal cerebellum?
an additional exterior cortical lamina layer. These cells populate the internal granular cell layer during early postnatal development
What does in-utero infection by feline panleukopenia virus cause? What does it result in?
damage to granular cell stem cells which results in cerebellar hypoplasia
Animals with cerebellar disease often have what clinical signs?
- attention tremors
- hypermetric gait
- ataxia (wide stance)
- relatively normal mentation
What does the brain stem contain?
colections of neurons known as nuclei (eg: dorsal and ventral respiratory groups)
What are the important regions of the brain stem?
- medulla oblongata
- thalamus (integration center)
- Hypothalamus (principle control center of hypophysis (pituitary gland))
What is a collection of neurons in the CNS having a common function?
What is found in the dorsal horns, intermediate grey, and ventral horns of the grey matter of the spinal cord?
Dorsal horns - sensory neurons and glia
Intermediate grey - autonomic neurons
Ventral horns - motor nerves and glia
What are the layers of the spinal cord from outside to inside?
- Dura mater
- Pia Mater
- White matter
- Grey matter
Where are multipolar motor neurons located in the spinal cord, what do they leave as and what do they innervate?
In ventral horns, their long axons leave spinal cord as ventral roots. Innervate skeletal muscle
Where are funicular neurons found?
in dorsal horns; axons go in dorsal funicles to brain
What are associating neurons?
small nerve cells with short axons which do not leave grey matter
Where are autonomic neurons found?
small nerve cell bodies in lateral horns
What tracts/pathways do motor and descending neurons take (efferent)
- Pyramidal tracts
What are the types of pyramidal tracts?
- lateral corticospinal tract
- Anterior corticospinal tract
What are the types of extrapyramidal tracts?
- rubrospinal tract
- reticulospinal tracts
- olivospinal tract
- vestibulospinal tract
What are the tracts/systems taken by sensory and ascending (afferent) neurons?
- Dorsal column medial lemniscus System
- Spinocerebellar tracts
- Anterolateral system
What are the types of spinocerebellar tracts?
- posterior spinocerebellar tract
- anterior spinocerebellar tract
What are the types of tracts in the anterolateral system?
- lateral spinothalamic tract
- Anterior spinothalamic tract
What are the two parts of the dorsal column medial lemniscus system?
- gracile fasciculus
- cuneate fasciculus
What are meninges?
membranous coverings of brain and spinal cord
What is pachymeninx?
(gr. pachys - thick) dura mater
What is leptomeninx?
arachnoid and pia mater
True or false? The arachnoid membrane is attached to the pia mater.
False. the membrane is attached to the dura mater
What does the subarachnoid space contain?
What are the characteristics of pia mater?
highly vascular, adherent to brain and spinal cord
What are the characteristics fo cerebrospinal fluid and what does it do?
- transudate, formed by capillaries and ependymal cells, the choroid plexuses of the lateral, 3rd and 4th ventricles of the brain
- Nourishes the CNS tissue, acts as a cushion
- produced and must be drained away at a constant rate
How often is the CSF renewed?
three times a day
What is the choroid plexus?
a cluster of arborizing blood vessels covered by a thin connective tissue and ependymal cells.
- site of CSF production
- are simple squamous to cuboidal
Where is the choroid plexus located?
in ventricles (aqueducts and canals lack a choroid plexus)
What are the sites of CSF drainage?
the arachnoid granulations/villi
- dorsal saggital sinus
What kinds of nerves are found in the peripheral nervous system and what are the nerve fibers invested by?
- sensory, motor, or mixed
- invested by CT of endoneurium, fascicles by perineurium, nerves by epineurium
What ganglia are sensory? (no synapses occur in them)
cranial and spinal ganglia
What ganglia have synapses occur in them?
autonomic ganglia = motor ganglia
What are nerves and what do they consist of?
- are collections of axons/dendrites outside the CNS
- consist of axons, dendrites, blood vessels, glial cells, and connective tissue (CT) investments (endoneurium, perineurium, epineurium)
What cells are present in a nerve?
- endothelial cells
- schwann cells
What are the cells of a ganglion?
neurons, neuroglial cells (amphicytes), schwann cells, endothelial cells. also axons
What are two types of ganglia?
- sensory (craniospinal)
- autonomic (vertebral, prevertebral, intramural or terminal)
How many neurons are used in the autonomic nervous system?
2 neuron chain
Where are the two neurons of the autonomic nervous system located?
first neuron is in the CNS, second neuron (cell body) is in a ganglion