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71 terms

25 March Lecture

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What are the two components of the nervous system?
-central nervous system (CNS)
-peripheral nervous system (PNS)
What is the CNS made of?
-brain
-spinal cord
What are the two divisions of the peripheral nervous system?
-afferent division
-efferent division
What are the two divisions of the efferent branch?
-somatic nervous system
-autonomic nervous system
Describe the somatic nervous system?
-motor output branch
-motor neurons connect to skeletal muscle at neuromuscular junctions
-nerve pathway uses only ONE neuron
Describe the autonomic nervous system
-motor output branch
-motor neurons connect to smooth muscle, cardiac muscle, or gands
-nerve pathway uses TWO neurons
What are the two divisions of the autonomic nervous system?
-sympathetic nervous system
-parasympathetic nervous system
What system (parasympathetic or sympathetic) dominates during "rest and digest" scenarios?
-parasympathetic
What system (parasympathetic or sympathetic) dominates during "fight or flight" scenarios?
-sympathetic
Where are the brain and the spinal cord found?
-within the dorsal body cavity
Where specifically is the brain found?
-within the neurocranial vault
Where specifically is the spinal cord found?
-within the vertebral column/spinal canal
What is a cranial nerve?
-a nerve that exits from the brain
What is a spinal nerve?
-a nerve that exits from the spinal cord
What are three ways to describe a neuron that carries information to the CNS?
-afferent neuron
-sensory neuron
-unipolar neuron
What are three ways to describe a neuron that carries information from the CNS?
-efferent neuron
-motor neuron
-multipolar neuron
List the important components of a spinal nerve
-dorsal gray horn
-lateral gray horn
-ventral gray horn
-dorsal root
-ventral root
-dorsal root ganglion
-mixed nerve
What is a mixed nerve?
-a nerve that contains both afferent/sensory neurons and efferent/motor neurons
Are most spinal nerves mixed nerves?
-yes!
What does each spinal nerve arise from?
-a dorsal root
-a ventral root
What is the dorsal root? Where does it come from? Where does it go?
-structure emerges from the dorsal gray horn within the posterior surface of the spinal cord
-joins with the ventral root to form a spinal nerve
What does the dorsal root contain?
-afferent/sensory neurons
What important structure lies in the dorsal root?
-the dorsal root ganglion
What is the dorsal root ganglion?
-a structure that contains the cell bodies of sensory neurons
What is the ventral root? Where does it come from? Where does it go?
-structure that emerges from the ventral gray horn within the anterior surface of the spinal cord
-joins with the dorsal root to form a spinal nerve
What does the ventral root contain?
-efferent/motor neurons
Does the ventral root contain a ganglion? Explain
-no
-efferent/motor pathways only contain one neuron
-the cell bodies of the efferent/motor neurons are found in the ventral gray horn
Which neurons innervate skeletal muscle fibers?
-somatic motor neurons
Which neurons form motor units?
-somatic motor neurons
Which neurons innervate smooth muscle, cardiac muscle, and gland cells?
-autonomic motor neurons
Which neurons use varicosities?
-autonomic motor neurons?
Which branch of the nervous system uses 2-neuron chains?
-autonomic nervous system
How many pairs of cranial nerves do humans have?
-12
Which is the only cranial nerve that leaves the head and neck region?
-vagus nerve
-CNX
What is this nerve responsible for? What branch of the autonomic system does it innervate?
-innervating many internal organs in the ventral body cavity
-parasympathetic nervous system
How many pairs of spinal nerves do humans have?
-31
What five regions do the spinal nerves exit from?
-cervical region
-thoracic region
-lumbar region
-sacral region
-coccygeal region
Where is the cervical region located?
-neck
Where is the thoracic region located?
-chest
Where is the lumbar region located?
-lower back
How many pairs of cervical nerves are there? Where are they found?
-8 pairs
-C1-C8
How many pairs of thoracic nerves are there? Where are they found?
-12 pairs
-T1-T12
How many pairs of lumbar nerves are there? Where are they found?
-5 pairs
-L1-L5
How many pairs of sacral nerves are there? Where are they found?
-5 pairs
-S1-S5
How many pairs of coccygeal nerves are there?
-1 pair
-Co1
What is a nerve plexus?
-network of intersecting nerves
-combine sets of spinal nerves that serve the same area of the body into one large grouped nerve
What nerve plexuses are found in the body?
-cervical plexus
-brachial plexus
-lumbar plexus
-sacral plexus
Where does the cervical plexus arise from?
-C1-C5
Where does the brachial plexus arise from?
-C5-T1
Where does the lumbar plexus arise from?
-L1-L4
Where does the sacral plexus arise from?
-L4-S4
What important nerve comes from the cervical plexus?
-phrenic nerve
What important nerves come from the brachial plexus?
-musculocutaneous nerve
-radial nerve
-median nerve
-ulnar nerve
What important nerves come from the lumbar plexus?
-femoral nerve
-obturator nerve
What important nerves come from the sacral plexus?
-sciatic nerve
What are the major events of neurulation?
-neuroectoderm appears along the length of the embryo
-neuroectoderm thickens to form a neural plate
-neural plate sinks and the edges thicken, forming a neural groove with a raised neural fold
-cells along the lateral margins of the fold become specialized neural crest tissue
-neural folds fuse, beginning with the cervical region and progressing rostrally (towards the head) and caudally (towards the tail)
-at 4 weeks, the neural tube is formed
Where do they signals for neurulation originate?
-from the notochord
In what germ layer does the neural tube form?
-ectoderm
In what germ layer does the notochord sit?
-mesoderm
What is the developmental fate of the prosencephalon (forebrain)?
-during the fifth week, the prosencephalon divides into the telencephalon and the diencephalon
What is the developmental fate of the telencephalon?
-persists in the fully developed brain, forming part of the forebrain
-has a pair of lateral outgrowths that later become the cerebral hemispheres
What is the developmental fate of the diencephalon?
-persists in the fully developed brain, forming part of the forebrain
-exhibits a pair of small cuplike optic vesicles that become the retinas of the eyes
What is the developmental fate of the mesencephalon (midbrain)?
-during the fifth week the midbrain remains undivided
What happens to the mesencephalon (midbrain) after the fifth week?
-persists in they fully developed brain, forming the midbrain
What is the developmental fate of the rhombencephalon (hindbrain)?
-during the fifth week, the rhombencephalon divides into the metencephalon and the myelencephalon (medulla oblongata)
What structures ultimately form the fully developed hindbrain?
-metencephalon, including the pons and the cerebellum
-myelencephalon (medulla oblongata)
What is the role of myelin in postnatal brain growth?
-myelination proceeds rapidly in infancy
-myelination is not complete until late adolescence
-as such, myelination is responsible for most postnatal brain growth
What is spinal bifida?
-a neural tube defects
-occurs when one or more vertebrae fail to form a complete neural arch for enclosure of the spinal cord
Which region of the spinal cord is most commonly affected by spina bifida?
-especially common in the lumbosacral region
Does maternal folic acid supplementation increase or decrease the risk of neural tube defects?
-decreases neural tube defects only if taken habitually before the egg is fertilized
Describe the nervous system route from finger to spinal cord to brain and back down...
1. unipolar sensory neuron detects stimulus
2. sensory neuron conveys signal from finger to the dorsal gray horn through the dorsal root ganglion and dorsal route
3. sensory neuron synapses with interneuron within the dorsal gray horn
4. interneuron conveys signal from dorsal gray horn to the thalamus within an ascending tract
5. interneuron synapses with third-order neuron within thalamus
6.third-order conveys signal to the cerebral cortex through a projection tract
7. cerebral cortex decides how to proceed
8. interneuron passes from cerebral cortex to the ventral or lateral gray horn through a descending tract
9. interneuron synapses with an efferent neuron (either somatic or autonomic) within the ventral or lateral gray horn
10. efferent neuron exits the spinal cord through the ventral root
11. ventral root and dorsal route combine to become a spinal nerve
12. spinal nerve carries neuron to effector organ