Lecture 11: Peripheral Nervous System Flashcards
Where do Cranial Nerves emerge?
From the brainstem
Where do Spinal Nerves emerge?
From the spinal cord
What are the two types of Peripheral Ganglia?
- Somatic sensory cell bodies
* Autonomic ganglia
How many Cervical Vertebrae and Nerves are there?
7 Cervical Vertebrae and 8 Cervical Nerves
How many thoracic Vertebrae and Nerves are there?
12
How many lumbar vertebrae and nerves are there?
5
How many Sacral vertebrae and nerves are there?
5
How many coccygeal nerves are there?
1
What is a Ganglia?
A collection of neuronal cell bodies in the peripheral nervous system
What do Somatic neurons innervate?
- Skin
- Muscle
- Bone
- Parietal membrane
What type of muscles does the Somatic Nervous system innervate?
Skeletal muscle
What Sensory aspects can the somatic nervous system detect?
Pain, Temperature, Touch, Proprioception
How does the Somatic Nervous system perceive pain?
It perceives pain directly arising from the site of an injury in a sharp, focussed and well-localized manner
What is the Parietal membrane innervated by?
The somatic nervous system
Which organs does the Autonomic Nervous System innervate?
•Visceral: Glands, Smooth muscle, Cardiac muscle, visceral membrane
What are the two components of the Motor Autonomic Nervous System?
Sympathetic and Parasympathetic
How does the Autonomic Nervous system perceive pain?
Pain is vague and ill defined or ache like and indirect/referred
What do Visceral Afferent detect?
Pain
What are the two types of General Afferents?
Somatic Afferent and Visceral Afferents
What are the two types of General Efferents?
Somatic Efferents and Visceral Efferents
What do Somatic Afferents sense?
Pain, temperature, touch, proprioception from body wall
What do Visceral Afferents sense?
Pain, distension, chemical from visceral structures
What are Somatic Efferents?
Motor neurons in the ventral horn projections to skeletal muscles
What are Visceral Efferents?
Autonomic fibres innervating smooth muscle, cardiac muscle and glands
What type of axon does the Dorsal Root contain?
Sensory Axons
What kind of axons does the Ventral root contain?
Motor Axons
What can it be called when the dorsal root and ventral root come together?
A spinal nerve
What are the two branches of a nerve known as after they came together to form a nerve?
The Ventral Primary Ramus and the Dorsal Primary Ramus
What does the Ventral Primary Ramus and the Dorsal Primary Ramus contain?
Both sensory and Motor axons
What axons does the Dorsal Primary Ramus have?
Somatic Motor axons and Somatic Afferents
Where does the Dorsal Primary Ramus inneravte?
The strip on the side of the vertebral column
What does the Ventral Primary Ramus innervate?
Everything but the strip on the sides of the vertebral column
Which part of the vertebrae do nerves exit?
The intervertebral foramen
What wraps around each individual axon?
Endoneurium
What wraps around bundles of axons?
Perineurium
What wraps around bundles of bundles of axons?
Epineurium
What is the layering of nerve wrapping from outside to inside?
Epineurium
Perineurium
Endoneurium
What wraps around individual axons?
Endoneurium
What is a fascicle?
A bundle of axons
What does the Perineurium wrap around?
Fascicles (bundles of axons)
What does the Epineurium wrap around?
The entire nerve
Where are blood vessels found in nerves?
In between the different fascicles
What is a Dermatome?
An area of skin in which a single spinal nerve innervates it
What are the 3 Somatic Nerve Plexuses?
- Brachial Plexus
- Lumbar Plexus
- Lumbosacral Plexus
What does the Brachial Plexus innervate?
Upper extremities
What does the Lumbar Plexus innervate?
- Lower anterior abdominal wall
- Medial and anterior thigh
- Inguinal region
What does the Lumbosacral Plexus innervate?
- Gluteal region
- Lower extremities
- Perineal region and genitals
Which spinal nerves is the Brachial Plexus made of?
C5 - T1
What 5 main nerves does the Brachial plexus form?
- Axillary (shoulder)
- Musculocutaneous (biceps)
- Median (forearm flexors, thenar)
- Radial (posterior arm and forearm)
- ulnar (hand muscles)
What does the Axillary Nerve of Brachial Plexus control?
Shoulder
What does the Musculocutaneous nerve of the Brachial Plexus control?
The Biceps
What does the Media nerve of the Brachial Plexus control?
The forearm flexors and thenar
What does the Radial nerve of the Brachial Plexus control?
Posterior arm and forearm
What does the Ulnar nerve of the Brachial Plexus control?
Hand muscles
What does the Brachial Plexus originate from?
The Ventral Primary Rami
Which nerves form the Lumbar Plexus?
L1-L4
What nerve originates from the Lumbar Plexus?
Femoral (anterior compartment thigh)
Which nerves form the Lumbosacral Plexus?
L4-S3
Which nerves originate from the Lumbosacral Plexus?
- Tibial (posterior thigh, toe muscles)
* Common Peroneal (lateral leg. ‘foot drop’)
What does the Tibial nerve of the Lumbosacral Plexus control?
The Posterior Thigh and toe muscles
What does the Common Peroneal nerve of the Lumbosacral Plexus control?
Lateral leg, ‘foot drop’ (dorsiflexion)
What are the steps in a Reflex arc?
A stimulus arrives at a receptor and a neuron is activated and the impulse travels to the dorsal root and the sensation is relayed to the brain but it also travels to a motor neuron that causes a response
Which pathway does a reflex arc take?
The spinothalamic tract
Where do Sympathetic nerves originate?
In the Thorax and Lumbar region
Where do Parasympathetic nerves originate?
In the Cranium and Sacrum
Which nerves are sympathetic nerves?
T1-L2
Which nerves are Parasympathetic nerves?
- CN III, VII, IX, X
* S2, S3, S4
How many neurons are there in the Somatic Motor Neuron?
From the CNS to the effector is one motor neuron (LMN)
How many neurons are in the Autonomic motor system?
2 neurons (Preganglionic and Postganglionic)
Which part of the Nervous system are Preganglionic and Postganglionic fibers found?
The autonomic motor system
Where is the ganglia of the autonomic nervous system found?
Outside the CNS
What is the relative length of Preganglionic and Postganglionic neurons in the Autonomic nervous system?
Sympathetic: Short Preganglionic neuron, long postganglionic neuron
Parasympathetic: Long preganglionic neuron, short postganglionic neuron
What neurotransmitter do all Autonomic preganglionic neurons use?
Acetylcholine
What neurotransmitter do Postganglionic sympathetic neurons use?
Norepinephrine and Epinephrine
What transmitter do Postganglionic Parasympathetic neurons use?
Acetylcholine
What is the one exception of neurotransmitters in Sympathetic nervous system?
Sweat glands use acetylcholine instead of adrenaline and noradrenaline
Where is the only place in the entire body where there isn’t a corresponding Parasympathetic system?
The Skin
What path do Sympathetic nerves go to innervate the skin?
The exit from the Ventral root (originally in the lateral horn) and go through the White ramus communicans find the postganglionic sympathetic nerve and then the grey ramus communicans
Where do preganglionic sympathetic neurons arise?
In the lateral horn of the spinal cord
Where does Direct (Somatic) pain arise from?
The body walls and limbs
How is Somatic pain perceived?
It perceived as sharp and well focused, arising directly from the site of injury
How does the sympathetic nervous system innervate the heart?
The preganglionic neuron exits the lateral horn and goes through the ventral route then joins the white ramus communicans and then goes up to the heart
Which nerves innervate the abdominal viscera?
T5-L2
How do Sympathetic nerves get to the abdominal viscera?
The nerve originates in the lateral horn and takes the ventral root to the white ramus communicans and synapses in front of the aorta to the postganglionic neuron to the organs of the gut
Where do Visceral Sensory axons synapse?
In the spinal cord
Where do sensory neurons from the viscera synapse?
In the spinal cord before they go to the brain
How does referred pain occur?
Sensory afferents combining
