OVERVIEW NERVOUS SYSTEM Flashcards
What makes up the structural part of the Nervous System?
The Peripheral Nervous System (ganglia and nerves) and Central Nervous System (gray matter and nuclei, white matter and tracts)
What makes up the functional part of the Nervous System?
Visceral and Somatic, which both consist of motor (efferent) and sensory (afferent)
parasympathetic
The parasympathetic nervous system affects the same body functions as the sympathetic nervous system, but in a completely different way. It works to slow down certain responses and bring about a state of calm to the body, allowing it to rest, relax, and repair itself. The primary function of the parasympathetic nervous system is to maintain long-term health and a healthy balance across all of the body’s functions. Parasympathetic responses include an increase of digestive enzymes, decreased heart rate, constriction of bronchial tubes in lungs, and more relaxed muscles.
Sympathetic
The fight or flight response is commonly known, but what may be lesser known is that this reaction to external stimuli is based completely on the sympathetic nervous system. When we are faced with a perceived threat of any kind, whether physical or emotional, our sympathetic nervous system kicks into gear and brings about automatic and involuntary responses, such as increased heart rate, elevated blood pressure, heightened awareness, elevated respiratory rate, and more sweating. The sympathetic nervous system also shuts down many parasympathetic responses in order to utilize more energy for the fight or flight response.
CNS
Brain and Spinal Cord
central sulcus
The sulcus between the frontal and parietal lobes
Lateral fissure (Sylvian fissure)
The fissure superior to the temporal lobe
Parieto-occipital sulcus
The sulcus that runs between the parietal and occipital lobes
calcarine fissure
Fissure in the occipital lobe
How many pairs of spinal nerves are in the spinal cord?
31 pairs of spinal nerves
How many nerves are there in the cervical cord?
8 cervical nerves
How many nerves are in the thoracic cord?
12 thoracic nerves
How many nerves are in the lumbar cord?
5 lumbar nerves
How many nerves are in the sacral cord?
5 sacral nerves
How many nerves are in the coccygeal?
1-2 coccygeal
What is conus medullaris?
The conus medullaris is the bundled, tapered end of the spinal cord nerves. Situated near the first two lumbar vertebrae, the conus medullaris ends at the cauda equina, a bundle of spinal nerves and nerve roots. Consequently, problems with the conus medullaris often affect the cauda equina.
What is cauda equina?
The cauda equina is the continuation of these nerve roots in the lumbar and sacral region. These nerves send and receive messages to and from the lower limbs and pelvic organs. Cauda equina syndrome (CES) occurs when there is dysfunction of multiple lumbar and sacral nerve roots of the cauda equina.
posterior root
sensory neurons (pseudounipolar)
posterior root ganglion
cell bodies of sensory neurons
anterior root
motor neurons (multipolar)
ANS =
sympathetic + parasympathetic
neuron =
functional unit
of the nervous system
Types of neurons
multipolar neurons (99% of all neurons) pseudounipolar neurons (sensory ganglia) bipolar neurons (retina, cranial nerve I, cranial nerve VIII)
How many layers do the cerebral cortex have?
– six layers
Layers of the cerebral cortex-
I. Molecular (plexiform) layer II. External granular layer III. External pyramidal layer IV. Internal granular layer V. Internal pyramidal layer VI. Multiform (fusiform) layer
I. Molecular (plexiform) layer
Layer I is the molecular layer and contains a few scattered neurons, including GABAergic rosehip neurons.[22] Layer I consists largely of extensions of apical dendritic tufts of pyramidal neurons and horizontally oriented axons, as well as glial cells.
II. External granular layer
Layer II, the external granular layer, contains small pyramidal neurons and numerous stellate neurons.
III. External pyramidal layer
Layer III, the external pyramidal layer, contains predominantly small and medium-size pyramidal neurons, as well as non-pyramidal neurons with vertically oriented intracortical axons; layers I through III are the main target of interhemispheric corticocortical afferents, and layer III is the principal source of corticocortical efferents.
IV. Internal granular layer
Layer IV, the internal granular layer, contains different types of stellate and pyramidal cells, and is the main target of thalamocortical afferents from thalamus type C neurons (core-type )[28] as well as intra-hemispheric corticocortical afferents. The layers above layer IV are also referred to as supragranular layers (layers I-III), whereas the layers below are referred to as infragranular layers (layers V and VI).
V. Internal pyramidal layer
Layer V, the internal pyramidal layer, contains large pyramidal neurons. Axons from these leave the cortex and connect with subcortical structures including the basal ganglia. In the primary motor cortex of the frontal lobe, layer V contains giant pyramidal cells called Betz cells, whose axons travel through the internal capsule, the brain stem, and the spinal cord forming the corticospinal tract, which is the main pathway for voluntary motor control.
VI. Multiform (fusiform) layer
Layer VI, the polymorphic or multiform layer, contains few large pyramidal neurons and many small spindle-like pyramidal and multiform neurons; layer VI sends efferent fibers to the thalamus, establishing a very precise reciprocal interconnection between the cortex and the thalamus.[29] That is, layer VI neurons from one cortical column connect with thalamus neurons that provide input to the same cortical column. These connections are both excitatory and inhibitory. Neurons send excitatory fibers to neurons in the thalamus and also send collaterals to the thalamic reticular nucleus that inhibit these same thalamus neurons or ones adjacent to them.[30] One theory is that because the inhibitory output is reduced by cholinergic input to the cerebral cortex, this provides the brainstem with adjustable “gain control for the relay of lemniscal inputs”.
cell body
contains a nucleus, nucleolus,
Nissl bodies (ribosomes and endoplasmic reticulum), Golgi complexes,
mitochondria, neurofilaments, microtubules
dendrites
contains same organelles as cell body except nucleus
Nissl bodies and Golgi complexes only in proximal portion
axon
contains mitochondria, neurofilaments
and microtubules, but no protein-making machinery
oligodendrocytes
branched processes radiate from the cell body
myelination of CNS axons
multiple internodal segments on multiple axons
multiple sclerosis demyelinates neurons of the CNS
treatment includes interferon
to diminish the immune response
astrocytes
numerous thin stellate processes radiate from the cell body
regulation of the extracellular ionic environment
guidance of migrating neurons during brain development
blood-brain barrier
glioblastoma - a multiform severe type of brain tumor
Schwann cells
myelination of PNS axons
single internodal segment
axons can regenerate to target
sensory ganglia
sensory pseudounipolar neurons neuron density higher satellite cells greater no synapses
autonomic ganglia
motor multipolar neurons neuron density lower satellite cells fewer synapses
non -neuronal cells - CNS
oligodendrocytes - myelinate axons
ependymal cells - line ventricle (brain)
astrocytes - have numerous functions
microglial cells - phagocytose (swallow) foreign matter
non -neuronal cells -PNS
neurolemmocytes - (Schwann cells) myelinate axons
satellite cells - are support cells for PNS neurons
