Questions and Answers
What are spinal nerves?
31 pairs of mixed nerves named for point of issue from spinal cord.
What is a mixed nerve?
A mixed nerve contains both sensory and motor neurons.
What do spinal nerves do?
Supply all body parts but head and part of neck (cranial nerves).
Where do spinal nerves exit?
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What are the two roots that connect to the spinal cord?
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How do spinal nerves form?
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What are the branches of spinal nerves called?
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What does RRNR stand for?
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What are the ventral rami except T2-T12 known for?
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What are the two types of paralysis mentioned?
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What happens to mature neurons regarding regeneration?
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What causes gait problems related to a herniated disc?
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What is the autonomic nervous system?
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What are the two arms of the autonomic nervous system?
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What is the craniosacral division?
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Sympathetic motor nerves originate from thoracic and lumbar spinal nerves. It is also called the _____________ division.
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What are the two types of neurons in the autonomic nervous system?
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Where do parasympathetic pre-ganglionic neurons travel?
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Where do sympathetic pre-ganglionic neurons travel?
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What neurotransmitter is released by preganglionic axons of both parasympathetic and sympathetic divisions?
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What neurotransmitter do postganglionic axons of parasympathetic neurons release?
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What neurotransmitters do postganglionic axons of sympathetic neurons release?
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What do cholinergic fibers release?
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What type of receptors bind acetylcholine (ACh)?
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What are the two types of cholinergic receptors?
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Study Notes
Spinal Nerves
- 31 pairs of spinal nerves; mixed nerves named for their exit point from the spinal cord.
- Contain both sensory and motor neurons, making them mixed nerves.
- Supply all body regions except the head and part of the neck.
- Distribution includes 8 cervical (C1-C8), 12 thoracic (T1-T12), 5 lumbar (L1-L5), 5 sacral (S1-S5), and 1 coccygeal (C0) nerve.
Exit and Structure of Spinal Nerves
- Spinal nerves exit the spinal column through the intervertebral foramen.
- Neuronal connections to the spinal cord are through ventral and dorsal roots.
- Dorsal and ventral roots unite to form spinal nerves.
Rami of Spinal Nerves
- Each spinal nerve branches into mixed rami: a shorter dorsal ramus and a larger ventral ramus.
- Ventral rami, except T2-T12, form interlacing nerve networks known as nerve plexuses (cervical, brachial, lumbar, sacral).
- Dorsal rami do not form plexuses, ensuring different muscle innervation.
Nerve Plexuses and Their Importance
- Nerve fibers within plexuses criss-cross, resulting in branches containing fibers from various spinal nerves.
- Each limb muscle typically receives nerve innervation from multiple spinal nerves, providing redundancy in case of damage.
Paralysis Conditions
- Quadraplegia refers to paralysis from the neck down, as seen in Christopher Reeve's case.
- Paraplegia refers to paralysis from the waist down, exemplified by Franklin D. Roosevelt.
Nerve Fiber Regeneration
- Mature neurons do not divide; damage to cell bodies prevents regeneration.
- Peripheral axon damage may allow regeneration; the closer the severed ends, the higher the chance of success.
Autonomic Nervous System (ANS)
- ANS is the motor division of the peripheral nervous system controlling involuntary activities.
- Consists of two arms: sympathetic (fight or flight) and parasympathetic (rest and digest).
- Most tissues receive innervation from both sympathetic and parasympathetic neurons, which have opposing effects.
Autonomic Nervous System Divisions
- Parasympathetic division: originates from cranial nerves and sacral spinal nerves; also called the craniosacral division.
- Sympathetic division: originates from thoracic and lumbar spinal nerves; referred to as the thoracolumbar division.
Neuron Structure in the ANS
- Efferent motor neurons follow a two-neuron circuit: pre-ganglionic neuron and post-ganglionic neuron.
- Parasympathetic pre-ganglionic neurons are longer, reaching distant ganglia close to the target tissue.
- Sympathetic pre-ganglionic neurons are shorter, mainly connecting to ganglia in the sympathetic trunk.
Neurotransmitters in the ANS
- Both divisions' pre-ganglionic axons release acetylcholine (ACh).
- Parasympathetic post-ganglionic axons also release ACh.
- Sympathetic post-ganglionic axons release epinephrine and norepinephrine (adrenaline and noradrenaline).
Receptors and Their Functions
- Cholinergic fibers release acetylcholine; all parasympathetic post-ganglionic axons are cholinergic.
- Adrenergic fibers release norepinephrine.
- Two types of cholinergic receptors exist: nicotinic (binds ACh) and muscarinic (also binds ACh); both are named after drugs that mimic ACh effects.
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Description
This quiz focuses on spinal nerves and mixed nerves, crucial components of the nervous system. It includes definitions and functions, providing key insights into how these nerves contribute to bodily functions. Perfect for students looking to enhance their understanding of nervous system anatomy.
