RE CH28 Part 1 Flashcards
What is the peripheral nervous system composed of?
Cranial/spinal nerves and their receptors
What is the central nervous system composed of?
Brain and spinal cord
What are the divisions of the peripheral nervous system?
Somatic and autonomic
What is the somatic nervous system?
Sensory neurons for the control of skin, muscles and joints
What is the autonomic nervous system?
Consists of sympathetic, parasympathetic, and enteric subdivisions which are responsible for involuntary innervation of various organs.
What is gray matter of the CNS composed of? What is white matter composed of?
Gray - neuron cell bodies
White - myelinated axons
What are pseduounipolar neurons?
Neurons with one cytoplasmic process that exits the cell and decides into two branches, one serving as the dendrite, the other as the axon.
Give examples of pseduounipolar neurons
Dorsal root/cranial ganglia - they enable sensory impulses to travel from the dendrite directly to the axon without passing through the cell.
What are multipolar neurons?
Multiple dendritic processes but only one axon, constitute the majority of the CNS
What are the four types of glial cells?
- Astrocytes
- Oligodendrocytes
- Microglial cells
- Ependymal cells
What is the function of astrocytes?
- Provide structural support, group and pair neurons, regulate the metabolic environment, and active in neuronal repair after injury.
- Fibrous astrocytes are found in white matter and protoplasm if astrocytes are found in gray matter
What is the function of oligodendrocytes?
Forms the myelin sheath of axons in the brain and spinal cord. They are capable of myelinating more than one axon.
What forms the myelin sheath in the peripheral nervous system?
Schwann cells - myelinated only one axon
What is the function of microglial cells?
Proliferate and develop into large macrophages that phagocytize neuronal debris
What is the function of ependymal cells?
Line the roof of the 3rd and 4th ventricles of the brain and central spinal canal to form the choroid plexus which secretes CSF
What is the node of Ranvier?
Non-myelinated junctions between Schwann cells and the site of impulse propagation. Impulses in myelinated axons travels from one node to another (saltatory conduction)
Which brain structures lack a blood-brain barrier?
Circumventricular organs: area of poster a, pituitary gland, pineal gland, choroid plexus, and portions of the hypothalamus.
What may cause blood brain barrier disruption?
TBI, subarachnoid or Intracerebral hemorrhage, cerebral ischemia, brain lesions, inntracaroitd injection of hyperosmolar solution (shrinks endothelial cells of BBB).
What are gyri and sulci?
Gyri - elevated convolutions of the cerebral cortex
Sulci - shallow groves of the cerebral cortex
What is the somatosensory cortex?
Located in the postcentral gyrus of the parietal lobe controls the sensations of touch, pain, limb position and the perception of grasped objects.
What is the function of the basal ganglia?
Control of movement
What is the function of the amygdala?
Regulation of emotional behavior, response to pain, appetite, and forming the response to stressors.
What is the function of the hippocampus?
Essential for memory formation and learning.
What is the diencephalon?
Located midline between the two cerebral hemispheres and contains the thalamus and hypothalamus.
What is the function of the thalamus?
Intergrated and transmits sensory information to various cortical areas of the cerebral hemispheres via separate thalamic nuclei
What is the hypothalamus?
The master neurohormonal organ.
Which structures make up the brainstem?
Midbrain, pons, and medulla.
What is the recticular activating system (RAS)
Located in the brainstem and functions to maintain consciousness, arousal, and alter news.
What is contained in the medulla?
Ascending and descending fiber tracts, respiratory and cardiovascular control centers, and nuclei to CN VII, IX, X, and XI
What are the three functional areas of the cerebellum?
- Flocculonodular lobe (archeocerebellum) - maintenance of equilibrium
- Paleocerebellum (anterior lobe and part of vermis) - regulates muscle tone
- Neocerebellum (posterior lobe and most of vermis) - coordinating voluntary muscle activity
What are the three meningeal layers?
Dura mater, arachnoid mater, and Pia mater.
Describe the dura mater
Thickest outermost layer of the meningeal layers
What folds does the dura mater form?
Falx cerebri - functionally separates cerebral hemisphere
The teorium cerebelli - separates the occipital lobe and cerebellum.
Describe the arachnoid mater
Thin avascular membrane joining the dura mater. The subdural space is located between the dura and arachnoid mater.
Describe the Pia mater
Thin avascular membrane adherent to the brain and spinal cord. The subarachnoid space is between arachnoid and Pia mater.
What levels does the subarachnoid space extend to in the spinal cord?
S2 to S3
Describe the epidural space
Located outside the dura but inside the spinal canal. Contains a venous plexus and fat that provides protection from the neural structures.
What is the distance from skin to epidural space?
3 - 8 cm
What is the total volume of CSF in the adult
150 mL
CSF is secreted by the epidural cells of the choroid plexus at a rate of _____ mL/hr and the total volume is replaced every ___ to ____ hours
30 mL/hr
3-4 hours
What is the normal CSF pressure?
5-15 mmHg
Describe CSF flow starting at the lateral ventricles
Lateral ventricles -> foramen of Monro -> third ventricle -> aqueduct of sylvius -> fourth ventricle -> formen of Lushka and foramen of magendie (openings in roof of fourth ventricle)-> subarachnoid space
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CSF drains into the venous blood via the _________ and is absorbed by ______
Saggital sinus
Arachnoid granulations
How many spinal nerves exist?
31 pairs (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, & 1 coccygeal)
Dorsal roots are _______(sensory/motor) fibers and ventral roots are _______ (sensory/motor)fibers
Dorsal = sensory Ventral = motor
Rexed laminar I through VI are located in the ________(dorsal/ventral) horn and contain cell bodies that receive _______(sensory/motor) information from the periphery
Dorsal
Sensory
Rexed laminae VII, VIII, and IX are located in _________(dorsal/ventral) horns and contain ________(motor/sensory) neurons
Ventral
Motor
Which laminae are interneurons located?
V, VI, and X
Define epineurium perineurium and endoneurium.
Epineurium - outermost covering of peripheral nerve
Perineurium - covers bundles of axons
Endoneurium - covers each axon in a fascicle
Intermediolateral gray horns are found between levels _____to ____. Why are they important?
T1 to L2
Preganglionic neurons of the SNS originate here.
Do Preganglionic axons exit the spinal cord via the dorsal or ventral nerve roots?
Ventral
SNS Preganglionic axons secrete which neurotransmitter At their ganglionic synapses? What about Postganglionic axons?
Preganglionic - Acetylcholine
Postganglionic - Norepinephrine
Where do parasympathetic preganglionic nerves originate?
Exit the midbrain and medulla via CN II, VII, IX, and X and the lateral horns of S2-S5
What neurotransmitters do parasympathetic preganglionic cells secrete? What about postganglionic?
Both secrete acetylcholine
The brain receives _____% of the cardiac output, or approximately _____mL/100g/min
15%
50 mL/100g/min
Which arteries make up the circle of Willis?
Both carotid arteries (anterior circulation) and both vertebral arteries (posterior circulation)
The artery of adamkiewicz enters the spinal cord and which level? What does it perfuse?
T7, the lumbosacral segment
What is the resting membrane potential of nerve cells?
-60 to -90 mV
The resting membrane potential is created through excess _____ charges on the extracellular surface and excess _______ charges on the interior of the cell membrane
Positive charges on extracellular surface
Negative charges on interior cell membrane
At resting membrane potential _____ ions are rich in the extracellular medium and _____ ions are rich in the intracellular medium
Sodium ions extracellular
Potassium ions intracellular
Depolarization is the result of increased permeability to which ion?
Sodium, causing an inward movement and more positive membrane potential to 30-50 mV at its peak
Excitatory neurotransmitters increase the permeability of the axolemma to _____ ions. Give examples.
Sodium
Acetylcholine, glutamate
Inhibitory neurotransmitters hyperpolarize the membrane by increasing the permeability to ______ ions
Chloride
Depolarization stimulates the uptake of _______ by nerve terminals which causes fusing of intracellular vesicles that contain neurotransmitters to the presynaptic membrane
Calcium
Acetylcholine is synthesized from acetic acid, coenzyme A, and choline in the presence of which enzymes?
Acetyl kinase and choline acetylase (also referred to as choline acetyl transferase)
List the biogenic amines
Epinephrine, norepinephrine, dopamine, serotonin, and histamine
What is responsible for terminating the effects of catecholamines?
Monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT)
What is the primary excitatory neurotransmitter in the CNS?
Glutamate
What is the major inhibitory neurotransmitter found in the CNS?
GABA
What is the primary inhibitory neurotransmitter in the spinal cord?
Glycine
Opioid alkaloids interact with which type of opiate receptor?
A. Delta
B. Kappa
C. Mu
C. Mu
What is substance P?
An excitatory neurotransmitter found in the basal ganglia, hypothalamus, brainstem, and dorsal root ganglia of the spinal cord. IT is released by pain fiber terminals that synapse with the substantial gelatinous a of the spinal cord.
Are sensory pathways afferent or efferent?
Afferent
Pain and temperature receptors in the extremities send signals to the spinal cords via dorsal or ventral roots of spinal nerves?
Dorsal
Dorsal root sensory nerve fibers terminate in which laminae?
I, IV, V, VI
What is the name of the pain and temperature pathway that sends signals from the extremities/trunk, up the spinal cord, to the brain.
Anterolateral pathway.
In the pain/temperature pathway after entering the dorsal horn anterolateral fibers decussate to where?
To the opposite anterior and lateral white columns.
After decussating the fibers ascend cephlad via anterior and lateral spinothalamic tracts and synapse with 3rd order neurons where?
Ventral posters lateral thalamic nucleus.
3rd order neurons in the pain/temp pathways ultimately synapse where?
The postcentral gyrus of the cerebral cortex (primary somatic sensory area)
What are internucal neurons?
Neurons with axons that synapse with motor neurons in the ventral horn. The can crossover and travel up or down the spinal cord before syapsing. Part of the reflex response to nocioceptive stimuli.
Vibration, proprioception, touch (VPS) synapse with neuron cell bodies in the dorsal root. First order neurons then enter dorsal white column and immediately ascend to where?
The medulla
In VPS After leaving their medullary nucleus second order neurons decussate and form the medial lemniscus which terminates where?
In the ventral posters lateral thalamic nucleus.
In VPS third-order neurons from the ventral posterolateral nucleus terminate where?
Postcentral gyrus
What is the corticospinal tract?
Transmits information from the poscentral gyrus to voluntary muscles of the trunk and extremities.
In the corticospinal tract, axons travel from pyramidal cells in the postcentral gyrus to where?
Internal capsule (major pathway for ascending and descending fibers between the cortex and other sites in the CNS)
In the corticospinal tract, axons travel from the internal capsule to where?
The medulla
In the corticospinal tract what happens with 90% of fibers in the medulla?
They decussate forming the pyramids of the medulla and then form the lateral corticospinal tract.
Axons from the lateral corticospinal tract continue their descent to where?
The spinal cord.
In the corticospinal tract, what occurs with the 10% of fibers that do not decussate in the medulla?
Continue to the spinal cord as the ventral corticospinal tract, they cross over before synapsids with lower motor neurons in the gray matter.
What are the three nuclei that make up the basal ganglia?
Globes pallidus, the putamen, and the caudate. Collectively these are termed the corpus striata.
What is the important neurotransmitter in the basal ganglia?
Dopamine.
What Subcortical motor areas are affected by Parkinson’s disease?
Globus pallidus and substantia nigra.
Which subcortical motor area is affected by Huntington chorea?
Caudate nucleus
