Peripheral Nervous System Flashcards
What do dorsal rami inervate?
What do Ventral Rami inervate?
Dorsal rami inervate muscle and skin of the back
Ventral Rami inervate muscle and skin everything else including limbs
RAMUS-Branch
Ramus-A branch, as of a nerve or blood vessel, or a projecting part,
What is neuropraxia?
Neuropraxia: involves a reversible conduction block characterized by selective demyelination of the axon sheath - endoneurium and axon still intact - e.g., nerve compression
What nuerons form the sympathetic system?
Formed by neurons from spinal nerves T1 to L2
Where do parasympathic ganglia lie?
They lie near the organs they innervate
What are the arrangement of nuerons in the ANS?
Involve two (pre and post) ganglionic neurons
What do Rami form?
Plexuses
Cutaneous innervation refers to the area of the skin which is supplied by a specific cutaneous nerve.
Dermatomes are similar; however, a dermatome only specifies the area served by a spinal nerve. In some cases, the dermatome is less specific (when a spinal nerve is the source for more than one cutaneous nerve), and in other cases it is more specific (when a cutaneous nerve is derived from multiple spinal nerves.)
Nerve supply to the skin. Cutaneous innervation refers to the area of the skin which is supplied by a specific cutaneous nerve. Dermatomes are similar; however, a dermatome only specifies the area served by a spinal nerve.
cutaneous- relating to or affecting the skin.
In each dermatome you find different peripheral nerves responsible for sensation and contraction.
Name the types of electromyographs and state what they entail?
Intramuscular EMG and surface EMG
- Intramuscular EMG - involves inserting a needle electrode through the skin into the muscle
- Surface EMG - placing electrodes on the skin over the muscle
What does the motor division of the PNS do?
The motor division of the PNS carries motor commands from the CNS to periheral tissues and systems.
Spinal nerves exit the ………………………. ……………… to form nerve plexuses
Define nerve plexuses?
Name 6 types of plexuses?
- Spinal nerves exit the intervertebral foramina to form nerve plexuses
- Nerve plexuses: networks of intersecting spinal nerves
- Include: cervical, brachial, lumbar, sacral, celiac, and coccygeal plexuses
What neurotransmitters are released by the sympathetic system?
Acetlycholine (ACh) and noradrenaline release at the synapse
What are the features of Group A neurons?
What are the features of Group B neurons and what do they do?
What are the features of Group C neurons and what do they do?
A group: large diameter, high conduction velocity, and are myelinated - alpha, beta, delta, gamma types
• B group: myelinated, small diameter, low conduction velocity - conduct autonomic information •
C group: unmyelinated, small diameter, low conduction velocity - dull, aching, burning pain and temperature sensation
Summary
What are neurons grouped on?
• Neurons grouped based on the diameter, signal conduction velocity and myelination state
Where do the gonglia from the sympathetic system lie near to?
Ganglia form near the vetebrae colomn
List 3 symptoms of sensory peripheral neuropathy?
What happens when you have a motor peripheral neuropathy?
What happens when you have a Autonomic peripheral neuropathy- what changes can it cause?
Sensory nerves (sensation): cause tingling, pain, numbness
- Motor nerves (movement): cause weakness to hands and feet
- Autonomic nerves (involuntary functions): cause changes in heart rate or blood pressure
What are dermatomes and what are there clinical significance?
State 4 differences between the parasympathetic system and sympathetic system?
What nerves make up the parasympathetic nervous sytem of the ANS?
Formed by neurons from cranial (III,XII,IX,X) and sacral (S2-S4) nerves
Name the 3 ways PNS Nerve Injuries are classified?
Image below shows nerve compression
Neuropraxia: involves a reversible conduction block characterized by selective demyelination of the axon sheath - endoneurium and axon still intact - e.g., nerve compression
- Axonotmesis: demylination and axon loss - epineurium and perineurium remain intact - still some continuity within the nerve - degeneration occurs below and slightly proximal to the site of injury
- Neurotmesis: most severe form of nerve injury - associated with complete nerve division and disruption - e.g., commonly seen after lacerations or ischemic injuries Ø Damage to the epineurium (around the entire nerve) - no nerve growth
What are mononeuropathy and polyneropathies?
Peripheral Neuropathies
Has many causes
- Mononeuropathy: refers to a single nerve being affected
- Polyneuropathy: refers to several nerves being affected
- Causes can be metabolic, toxic, inflammatory, traumatic, genetic
- ~30% of neuropathies are “idiopathic” - i.e. of unknown origin
What phrase is associated with the sympathetic system?
“fight or flight”
What phrase is linked with the parasympathetic system?
Resting and digesting
What are peripheral neuropathies and what do they impare?
Damage or disease affecting PNS nerves
May impair sensation, movement, gland or organ function
What is neurotmesis?
Image below wallerian degeneration
Neurotmesis: most severe form of nerve injury - associated with complete nerve division and disruption - e.g., commonly seen after lacerations or ischemic injuries Ø Damage to the epineurium (around the entire nerve) - no nerve growth
Are neurons in the PNS are myelinated or unmyelinated or both?
What cells provide myelin in the PNS?
Neurons in the PNS are myelinated or unmyelinated
• Myelin in the PNS is derived from Schwann cells
What type of neuron or neurons do Rami carry?
Both motor and sensory fibres
What can slower than normal nerve conduction studies indicate?
Nerve Conduction Study (NCS)
- Technique for evaluating the speed of nerve impulses - nerve conduction velocity (NCV)
- Nerves are stimulated with small electrical impulses by one electrode while other electrodes detect the electrical impulse “down-stream” from the first electrode
- Distance between electrodes and time taken for electrical impulses to travel between electrodes are used to calculate the speed of nerve signals
- Slower than normal speed could indicate nerve damage from direct trauma, diabetic or peripheral neuropathy, viral nerve infection or nerve entrapment diseases like the Carpal Tunnel Syndrome among other conditions
What is axonotmesis?
Image below is wallerian degeneration
• Axonotmesis: demylination and axon loss - epineurium and perineurium remain intact - still some continuity within the nerve - degeneration occurs below and slightly proximal to the site of injury
What type of effector is found in the Autonomic NS?
How many neurons are involved in the Autonomic nervous system from the spinal cord to target organ?
Is the ANS always simulatory, inhibatory or both?
What neurotransmitters does the ANS releases?
Does the SNS fire at rest?
Involuntary effectors (e.g., cardiac muscle, glands)
- Usually two neurons from spinal cord to target organ (ganglionic synapse)
- Stimulatory or inhibitory
- ACh and/or NE released at the synapse
- Have a baseline firing
What are myotomes and what are there clinical significance?
Groups of muscles supplied by a single spinal nerve root - motor equivalent of a dermatome
Clinical significance: important part of neurological examination (e.g., testing for muscle weakness)
Sate how many cranial nerves there are?
State the names of all the Cranial Nerves and state wheather they are sensory or motor or both?
If the mnuemonic isn’t gd use a dirty one
Draw a diagram showing the various types of nervous systems in the human body.
Start of with nervous system and break of from that point into the two types of nervous sytems and break of again
Name two types of nuerons and state if they are afferent or efferent?
Name 3 types of nerves and state what type of nuerons they are composed of?
What does the sensory division of the PNS do?
The sensory division of the PNS brings information to the CNS from receptors in peripehral tissues and organs.
What diagnostic technique is used to Distinguish between muscle conditions that begin in the muscle and nerve disorders that cause muscle weakness?
Electromyography (EMG)
Somatosensory Evoked Potential (SEP)
Why are SEP’s used?
Somatosensory Evoked Potential (SEP)
- SEP are measured to assess whether sensations (pain, temperature and touch) in the periphery are being transmitted to the brain
- Stimulating electrodes are placed on the arm and/or leg
- Recording electrodes are placed on the head and/or spine
- Evoked potentials in the recording electrodes can indicate the integrity of transmission at peripheral mechanoreceptors to the cerebral cortex
- Usually combined with EMG and NCV tests to assess the patient for generalized disorders of the nervous system like multiple sclerosis (MS)
What neurotransmitter is released in the Parasympathetic system
ACH
What is the PNS a network of?
Network of cranial and spinal nerves outside the CNS
Where are ganglia located ( PNS or CNS) and what do they consist of?
- Each spinal nerve is attached to the spinal cord by ………… roots
- Dorsal (posterior) root - brings …………………. signals from the………………… to the ……………..
- Ventral (anterior) root - takes ……………………….. signals from the ……………………………. to the …………………………….
- The two roots join to form a …………….., spinal nerve
Ganglia - cell bodies, dendrites and synapses in the PNS
- Each spinal nerve is attached to the spinal cord by two roots
- Dorsal (posterior) root - brings afferent (sensory) signals from the periphery to the CNS
- Ventral (anterior) root - takes efferent (motor) signals from the CNS to the periphery (motor neurons)
- The two roots join to form a mixed, spinal nerve
What type of nerves make up the SNS? Afferent or Efferent
Where does the basic route of nerve signals befin at?
Can the SNS be autonomic (reflexive)?
Somatic Nervous System
- Consists of efferent nerves responsible for stimulating muscle contraction
- Basic route of nerve signals begins in the primary motor cortex
- Can be voluntary or automatic (reflexive)
- Nerves terminate at the neuromuscular junction to produce the motor response
Somatic= SKELETAL MUSCLE CONTROL
Define Endoneurium, Perineirium and Epineurium
Endoneurium: around each individual neuron
Perineurium: around bundles of neurons
Epineurium: around the entire nerve
Autonomic Nervous System
Consists of ……………. nerves stimulating …………….. outside our control (e.g., heart rate)
Basic route of nerve signals begins in the nuclei of the ………………… that travel to the ……………….. nuclei
What type of nuerons are involved in the ANS?
What are the two divisions if the ANS?
Consists of efferent nerves stimulating effectors outside our control (e.g., heart rate)
- Basic route of nerve signals begins in the nuclei of the hypothalamus that travel to the brainstem nuclei
- Involve two (pre and post) ganglionic neurons
- Consists of two divisions: Ø Sympathetic Ø Parasympathetic
Nerve Conduction Velocity (NCV)
What features of a nerve determine nerve conduction velocity?
How do newborn values of NCV compare to adults?
NCV is related to the diameter of the nerve and the degree of myelination (the presence of a myelin sheath on the axon) of the nerve
• Newborn infants have values that are approximately half that of adults • Adult values are normally reached by age 3 or 4 years of age
How many pairs of nerves does the PNS consist of and state how you would calculate it?
Cranial Nerves + Peripheral nerves=12 +31= 43
What type of effector is found in the Somatic NS?
How many neurons are involved in the somatic nervous system from the spinal cord to target organ?
Is the SNS always simulatory, inhibatory or both?
What neurotransmitter is released at the synapse?
Does the SNS fire at rest?
SNS
- Voluntary effectors (e.g., striated muscle)
- Single motor neuron from spinal cord to target organ
- Always stimulatory
- ACh released at the synapse
- Do not fire at rest
