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Nervous System: Peripheral Nerves
I). Cranial Nerves
A). 12 nerves Have both somatic and autonomic functions.
B). Summary Anterior of the Brain to Posterior
nerves for smell
nerve for vision.
Somatic & Parasympathetic:
control of extrinsic eye muscles and pupil dilation.
control of muscles that surround the eye.
Sensory & Somatic
control of facial nerves and muscles for chewing.
muscle control of lateral movement of the eyeball.
Sensory, Somatic & Parasympathetic
control over facial expression and taste.
or Auditory Nerve
nerve for hearing.
Sensory, Somatic & Parasympathetic
control over taste, the tongue and the pharynx.
nerve with some Somatic and Sensory functions. Controls visceral organs.
control over larynx, pharynx and sternocleidomastoid muscles
control over the tongue.
II). Spinal Nerves
A). 31 pairs of spinal nerves
|Nerve Plexus are interlaced nerve networks that form when the rami join together.|
B). Somatic and Sensory nerves
1). C1 to C8 cervical nerves
a). Cervical plexus
|Deep in neck under sternocleidomastoid muscle.|
|Works muscles in the neck, scapulae, trapezius, and diaphragm. (C3 to C4)|
|Sensory skin in neck, ear, and chest.|
b). Brachial plexus
|Found partly in the neck and axilla.|
|All of the nerves that innervate the upper limbs. (C5 to C8)|
i). Axillary nerve: Deltoid & Teres minor
ii). Musculocutaneous nerve: Biceps brachii, brachialis and skin.
iii). Median nerve: Flexor muscles, wrist & fingers.
iv). Ulnar nerve: flexors not covered by median nerve. (Funny bone pain)
v). Radial nerve: Extensor muscle and skin.
2). T1 to T 12 thoracic nerves
a). Intercostal nerves
|Supply intercostal muscles, abdominal wall and branch into the skin.|
3). L1 to L 5 lumbar nerves
a). Lumbar plexus
|L1 to L4 Innervates abdominal wall and interior and medial thigh.|
i). Femoral nerve: Skin and quadriceps.
ii). Obturator nerve: Adductor muscles
iii). Saphenous nerve
4). S1 to S5 sacral nerves
a). Sacral plexus
|L4 to S4 Buttock and lower limb|
i). Sciatic nerve: Posterior thigh, hamstrings, flexors and extensors
ii). Tibial nerve: part of sciatic Posterior calf and foot.
iii). Common fibular nerve (peroneal): part of sciatic. Knee joint and anterolateral lower leg muscles.
5). C0 coccygeal nerve
III). Innervation of joints
Any nerve serving a muscle producing
movement at a joint also innervates the
joint itself and the skin over that joint.
IV). Innervation of skin
V). Reflex Arc
|sensory neuron||integration center|
A reflex is involuntary rapid predictable motor response to a stimulus.
It is a spinal response that occurs without any input from the brain.
B). Necessary Components
2). Sensory neuron
3). Integration Center:
4). Motor neuron:
1). Spinal reflexes
a). Stretch & Deep Tendon
Control the rate and amount of stretch by contracting and relaxing muscle. Muscle tone is adjusted reflexively in response to posture
i). Stretch Reflex:
Muscle contraction in response to muscle stretch or increased length.
ii). Deep Tendon Reflex:
Muscle lengthening in response to muscle contraction or shortening.
ie. Patellar (Knee jerk response)
Strike patellar tendon (stimulus)
Stretches the quadriceps muscle (receptor)
Stimulates muscle spindle (sensory neuron)
Afferent impulse to spinal column (integration center) Impulses inhibit contraction of antagonist muscle (motor neuron)
Results in contraction of quadriceps and inhibition of hamstring. (effector)
b). Flexor Reflex
Withdrawal of body part in response to a painful stimulus. (either real of perceived)
c). Crossed Extensor Reflex
Withdrawal of body part while simultaneously extending the opposite of the body to maintain support.
d). Superficial Reflexes
Response to gentle cutaneous stimulation.
ie. Plantar Reflex:
VI. Autonomic Nervous System
(parasympathetic & sympathetic)
if you could control this system think in terms of:
Fight or flight: what do you do when there is a tiger in the room
Maintenance: what do you do when you are "vegging out" on the Lazy Boy.
Involuntary nervous system or visceral motor nervous system. Functions in coordination with the somatic and sensory system and higher brain functions.
Both systems are fully integrated.
Dual system with the parasympathetic and sympathetic system innervating the same organs but causing opposite effects.
Sympathetic: Fight or Flight (tiger in the room) Parasympathetic: Maintenance ("vegging out" on the Lazy Boy)
B). Comparison to Somatic Nervous System
Skeletal muscle (only)
Smooth muscle Cardiac muscle Glands
2). Efferent Pathways
Somatic: cell body in CNS axon attaches to skeletal muscle.
Conduction of impulses very fast
Autonomic: 2 neuron chain
Cell body of first neuron in the CNS 2nd neuron outside CNS and attached to effector organ. Conduction of impulses slower.
2). Neurotransmitter Effects
Somatic: Always excitatory
Autonomic: Excitation or Inhibition
C). Differences in Parasympathetic & Sympathetic Divisions
1). Functional Role
Parasympathetic: Maintenance functions
Conserves & stores energy
Sympathetic: Prepares the body for emergencies
Intense muscular activity Fight or Flight
2). Origin sites
Parasympathetic: Brain & Sacral Spinal Cord
Sympathetic: Thoracic-Lumbar Spinal Cord
3). Length of ganglionic fibers
Sympathetic: Some Acetylcholine in preganglia (first neuron that connects to the second neuron) but postganglia release Norepinephrine (common term Adrenaline) this goes to the effectors.
D). Parasympathetic Division (Maintenance division)
(When you are "vegging out" on the lazy boy you do not want your heart racing. This is a time to digest your hamburger and lounge around)
1). Parasympathetic fibers do not run in spinal nerves. (Vagus nerve is a cranial nerve, so are many of the parasympathetic nerves)
2). Nerves arise from the cranial, (brainstem) and the sacral region.
3). Nerves involved
i). Oculomotor nerves: constrict pupils focus on objects
ii). Facial nerves: activates glands
lacrimal glands & salivary glands
(Think of the oppisite when you are exicited your mouth dries up because the last thing you need is to process food)
iii). Glossopharyngeal nerves: salivary glands
iv). Vagus nerves:
Serves most of the visceral organs
Cardiac plexus: Slows the heart rate Pulmonary plexus Esophageal plexus: liver, gallbladder, stomach, small intestine, kidneys, pancreas, large intestine. (This is independent of the spinal cord)
5). Sacral nerves: pelvic organs, bladder, genitals & large intestine.
E). Sympathetic Division (fight or flight)
Innervates visceral organs, adrenal glands, sweat glands and hair raising glands and vascular smooth muscle.
When the tiger is in the room you do not want blood and energy going tot he visceral organs to digest your dinner you want blood going to the muscles (vascular dilation) and when you are running you are producing heat so you need to sweat)
Functions of Sympathetic and Parasympathetic Divisions
Look at this table and think of how to balance resources when there is a tiger in the room.
Relaxing in the lazy boy
There is a tiger in the room
Hair raising muscle
Dilates skeletal muscle