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180 Cards in this Set

  • Front
  • Back
What does the spinal cord occupy?
The spinal canal of the vertebral column.
In adults were does the spinal cord begin and end?
It begins at the foramen magnum and ends at the conus medullaris (L1-L2).
How many spinal cord segments are there total?
31
What is another name for dorsal?
Posterior
What is another name for ventral?
Anterior
How does sensory information interact with the spinal cord?
Sensory information is afferent(ENTERS) the cord through the posterior (dorsal) roots.
How does motor activity interact with the spinal cord?
Motor activity is efferent (LEAVES) the cord through the ANTERIOR (VENTRAL) roots.
What does gray matter contain and how is it shaped?
It is an H-shaped or butterfly shaped central region of the spinal cord; It contains nerve cell bodies, axons, and synapses.
Where are the gray matter lateral horns located?
T1-T12 and L1-L2
The sensory relay neurons, anterior motor neurons, and inter neurons are part of what?
Several million neurons in the gray matter.
What do the axons leave the ventral anterior roots where do they innervate?
Skeletal muscle fibers
What are the two types of motor neurons?
Alpha and Gamma
What is the role of the alpha motor neurons and how much of the motor pool do they take up?
Alpha motor neurons are faster and they give a rise to Large A alpha nerve axons which innervate the extrafusal skeletal muscle fiber (ability of muscle to do work). It comprises of 2/3 of the total motor neuron pool.
What is the role of the gamma motor neurons and how much of the motor pool do they take up?
Gamma motor are much smaller neurons than alpha. They innervate intrafusal fibers in muscle spindles. They make up about 1/3 of total motor neurons in the anterior horns.
Is gray matter myelinated or unmyelinated?
Unmyelinated
Where do the motor neurons receive most of their input?
Interneurons
Where are the inter neurons found and they synapse with what?
Interneurons are present in all areas of the gray matter. They are the most abundant cell in the matter (30times more than alpha). There is both excitatory and inhibitory interneurons. They synapse with motor neurons.
What is the function of the interneurons?
They synapse with alpha motor neurons. Most motor activity descending from the brain is directed first to the interneurons, not directly to the alpha motor neurons.
Where do interneurons receive input from?
Certain sensory nerves.
What gives the color to white matter?
It being myelinated
What does the white matter contain?
It contains numerous bundles or tracts of nerve axons.
What are the two types of ascending tracts?
Lateral spinothalamic tracts

Posterior spinothalamic tracts
What are the Lateral spinothalamic tracts for?
Principal pathway for transmission of pain and temperature sensations.
What are the Posterior spinothalamic tracts (dorsal) for?
Principal pathway for transmission of tactile and proprioceptive sensations.
What is the function of proprioceptors?
A sensory receptor, found chiefly in muscles, tendons, joints, and the inner ear, that detects the motion or position of the body or a limb by responding to stimuli arising within the organism.
What are the two descending tracts in the spinal cord?
Corticospinal (pyramidal)tracts and nerve tracts associated with the sympathetic nervous system.
Where are the corticospinal (pyramidal)tracts?
They originate in the motor cortex and terminate primarily on interneurons in the spinal cord gray matter.
Where do the cords associated with the sympathetic nerve system originate?
Originate in the brainstem and terminate in spinal T1-T12 and L1-L2
What are the three layers of connective tissue around the cord?
Pia mater, arachnoid mater, and dura mater.
Where does the dura and arachnoid extend too?
S2
What space contains CSF?
Subarachnoid space
What is contained in the epidural space?
It contains fat, connective tissue, and venous plexuses. It extends from the foramen magnum to the sacral hiatus.
Where does the epidural space start and finish?
Foramen magnum to the sacral hiatus
What are the ligaments in the spinal column?
Ligamentum flavum-lies jsut poserterior to the epidural space.

Interspinous ligament

Supraspinous ligament
Where does the spinal cord receive its blood supply?
Vertebral arteries and thoracic and abdominal aorta.
What supplies the anterior two thirds of the cord with blood? It is a single midline vessel, which originates from the vertebral arteries.
Anterior spinal artery
What supplies the posterior one third of the cord? It arises from the posterior cerebellar arteries.
Posterior spinal arteries.
What does the radicular arteries supply blood too?
Anterior and Posterior spinal arteries.
Where does the artery of adamkiewicz arise from and what does it supply?
It is a single branch off the left side of the aorta and almost always arises off the left.

It supplies blood flow to the lower thoracic and lumbar cord
Where is the origin of the artery of adamkiewicz in 60% of individuals?
T9-T12
Where is the artery of adamkiewicz in 25% of individuals?
L1-L2
Where is the artery of adamkiewicz in 15% of individuals?
T5-T8
What happens if the artery of adamkiewicz is injured?
Paraplegia
What system are the the spinal nerves apart of?
Peripheral nervous system
The spinal nerves are formed by the joining of the ______and _______ at each spinal cord segment.
Anterior and Posterior
How are the spinal nerves formed?
The joining of the anterior and posterior roots.
Where do spinal nerves exit the vertebral column?
The intervertebral foramina and between the vertebrae.
How many pairs of spinal nerves are there?
31
How many cervical nerves are there?
8
How many thoracic nerves are there?
12
How many lumbar nerves are there?
5
How many sacral nerves are there?
5
How many coccygeal nerves are there?
1
The lower lumbar and sacral nerves descend descend as the ______ _______before exiting the vertebral column.
Cauda equina
Why are the spinal nerves considered mixed nerves?
They contain somatic (sensory and motor) and autonomic nerve fibers.
What does dermatome mean?
Each spinal segment supplies a specific region of skin and skeletal muscle.
What are the two major branches of spinal nerves (rami)?
Anterior primary division


Posterior primary
Anterior primary division
Major portion of the spinal nerve
Posterior primary division
Supplies long muscles of the back and tissue overlying them
What is a plexus?
Intermingling collection of nerves that emanate from different cord segments.
What does a plexus usually contain?
Typically contains sensory and motor nerve fibers that innervate a particular region of the body, limbs, and neck
Cervical plexus
It comes from the anterior plexus of spinal nerves C1-C4 and forms in the neck.

It supplies skin and muscles of the neck and posterior scalp. ALSO, PHRENIC NERVE emerges to innervate the DIAPHRAGM.
Brachial plexus
It comes from the anterior plexus of C5-C8 and T1.

It emerges from the plexus to innervate the upper limb, shoulders, and pectoral muscles.
Lumbosacral plexus
Anterior rami of spinal nerves L1-L5 and S1-S4.

Peripheral nerves emerge from this plexus to innervate the lower limbs and pelvis.
What are proprioceptors (muscle receptors)?
They provide continuous feedback information to the CNS with respect to muscle length and tension, and the rates of change of muscle length and tension during movements.
Where is the feed back of the proprioceptors directed towards?
spinal cord, cerebellum, and motor cortex.
What are the two types of muscle receptors?
Muscle spindles and Golgi tendon organs.
What is the function of muscle spindles?
The spindles function as stretch and receptors and detect changes in muscle length.(dynamic and static)
What are muscle spindles made of and where are they attached?
Each spindle is MADE UP of several INTRAFUSAL muscle fibers and are attached to the glycocalyx of surrounding EXTRAFUSAL fibers
The central region of the spindle is innervated by sensory nerves, which ones? This central region is extremely sensitive to ______of the muscle.
Type 1A and II. They are sensitive to stretch of the muscle.
What do they end portions of intrafusal fibers contain?
Actin and Myosin
What are sensory receptors located in the muscle tendons near the point of attachment of the tendons to the skeletal muscle fibers?
Golgi Tendon organs
What are these receptors sensitive too?
Tension
Type __ sensory nerves transmit information from the golgi tendon organs to the CNS. From there the signals are directed towards what?
Type 1B

Directed towards spinal cord, cerebellum, and cerebral cortex.
What type of reflex is the stretch reflex? Is it slow or does it occur rapidly?
The stretch reflex is monosynaptic and it occurs very rapidly with minimal delay.
Trace the Stretch reflex.
First the stretch muscle activates muscle spindles.

Sensory information delivered via type 1A sensory fibers to the dorsal root of the spinal cord segment.

From there it is delivered to the alpha motor neuron. Which the alpha motor neuron is then activated.

Muscle contraction occurs to oppose stretching of muscles.
Show an example of stretch reflex?
Patellar reflex
What reflex is elicited by painful stimulus?
Flexor (withdrawal) reflex
Trace the flexor reflex
Activation of sensory receptors

Sensory information directed to the interneurons in the spinal cord

excitation of alpha motor neurons that innervate appropriate flexor muscles

contraction of flexor muscles to remove affected body area from the painful stimulus.
What happens during crossed extension? Is it immediate? Pertinent?
Flexion of one limb accompanied by extension of the opposite limb. Delayed reflex (200-500 msec). Helps to maintain balance from the flexion.
What are muscle spasms?
Possibly a response to irritation of muscle. Painful stimulus goes to the spinal cord then muscle contraction occurs.
What can cause muscle spasms?
Fractures which cause local spasm

peritonitis, abdominal surgery which cause contraction of abdominal muscles

Ischemia, excess exercise which local spasms or cramps
What are some insults that can lead to lesions?
Trauma

Degenerative and demylinating disorders such as multiple sclerosis and ALS

Tumors

Infections

Ischemia
What happens during spinal cord transection?
Initial period of spinal shock---both somatic and autonomic reflexes below the lesion are temporarily interrupted. Blood pressure can fall dramatically but usually recovers within a few days.

Over a period of several weeks or more, spinal neurons below the lesion regain excitability and atleast some reflexes return. There is loss of sensation and voluntary movements below the transection.
What is autonomic hyperreflexia?
It is overactivity of the sympathetic nervous system. Commonly seen in cord transection at T5 of above and unusual below T10.
What cause autonomic hyperreflexia?
A cutaneous (incision) or visceral (bladder) stimulation below the level of transection can trigger strong autonomic responses.
Strong autonomic responses include?
Sympathetic discharge cause intense vasoconstriction below the lesion

Reflex bradycardia and vasodilatation occur above the lesion

Hypertension is the NET RESULT

Cardiac dysrhythmias may occur
What causes Brown sequard syndrome?
Hemisection of spinal cord
What are the characteristics?
Loss of all sensation and tone near the site of injury

Below the lesion on the same side, there is loss of tactile discrimination, loss of sensation and spastic paralysis

Below the injury opposite side there is a loss of pain and temperature sensation-impair tactile sense with no loss of motor function
Where are local anesthetics injected during a spinal block?
Subarachnoid space (CSF) of the spinal cord but BELOW the end of the spinal cord usually L3-L4 or L4-L5
What effect does CSF circulation have on the effect of the drug?
None
What is the uptake of local anesthetics into?
Spinal nerve roots-main site of action

Dorsal root ganglia-motor

Spinal cord itself-autonomic
What are the complications spinal blocks? (2)
Hypotension from the sympathetic nervous system blockade can cause venous pooling of blood and decreased venous return and cardiac output.

Post spinal headache may occur as a result of CSF leakage from the puncture site. Reduction of CSF pressure in the subarachnoid space like causes tension or collapse in the meninges.
In epidurals blocks where is it usually at? How fast is it? Can hypotension still occur?
Lumbar region in the spinal nerve roots.

Epidural blocks are slower than spinal blocks.

An abrupt fall in blood pressure usually does not occur but is still a potential complication.
What does the epidural space contain?
fat, connective tissue, and venous plexuses but not free moving fluid as in the subarachnoid space.
In epidural blocks what blockade occurs?
sympathetic, sensory, and motor nerve.
Sensory receptors are usually what?
Nerve ending that acts as a transducer which CONVERTS the natural from of the stimulus into ELECTRICAL impulses or action potentials.
The magnitude of the receptor potential is determined by what?
Stimulus strength or intensity
If the receptor potential reaches threshold, then what?
Action potential will be generated.
What is a receptive field?
An area over which the receptor will detect a stimulus.
Adjacent receptive field _______, which allow for very precise localization of a stimulus.
Overlap
The frequency of action potentials produced by the receptor is proportional to the ________ of the receptor potential.
Magnitude
All sensory receptors show some degree of _______ to a stimulus. Some very rapidly while others slowly.
Adaptation
What are the five types of sensory receptors?
Mechanoreceptors

Thermoreceptors

Nociceptors

Electromagnetic receptors

Chemoreceptors
What do mechanoreceptors detect?
Mechanical deformation of tissues
What do thermoreceptors detect?
Detect changes in tissue temperature, both cold and warmth
What do nociceptors detect?
Detect tissue injury-pain or potential injury
Electromagnetic receptors
Detect light waves-retina
Chemoreceptors
Detect changed in the chemical composition of the local environment. Changes in PO2 PCO2
Sensory nerves transmit action potentials from the sensory receptors to the ___?
CNS
What are the two types of sensory fibers?
Type A

Type C
Type A fibers are _______ fibers of the spinal nerves, and the subgroups are _____,_____,_____,and ______.
Myelinated

Alpha, beta,gamma, and delta
Type C fibers are _______ in diameter and are __________ fibers. They have low conduction velocity. Comprise more than ___% of peripheral somatic sensory nerve fibers.
Smaller

Nonmyelinated

50%
Sensory Classification

Group 1A
Muscle spindles
Group 1B
Golgi tendon organs
Group II
Muscle spindles and most tactile receptors (descrete touch)
Group III
Thermoreceptors and some nociceptors (fast pain)
Group IV
thermoreceptors and some nociceptors (slow pain)
What are the 5 special senses?
Vision

Hearing

Taste

Smell

Equilibrium
What are the five somatic sensations?
Tactile sensation:touch, pressure,
vibration

Proprioceptive sensation:limb position and joint angle

Kinesthesis: body and limb movements

Temperature

Pain
Where are free nerve endings found extensively and what do they detect?
In the skin and they detect touch and pressure. Also found in cornea
Most tactile sensory receptors transmit sensory signals to the CNS through what?
A-beta (group II) sensory fibers
Free nerve endings transmit signals through small what fibers?
A-delta fibers and unmyelinated type C fibers (itch, tickle)
Trace the transmission of tactile signals to within the CNS
Sensory information enters the spinal cord via the dorsal roots and directed to the brain via the dorsal column.

Sensory nerves branch after entering the cord. Medial branch enters the dorsal column and proceeds towards the brain.

Ascending fibers synapse in the dorsal column in the medulla, second order fibers decussate and pass upward to the thalamus through the medial lemniscus pathway

Fibers in the medial lemniscus synapse with specific sensory relay nuclei in the thalamus. 3rd order fibers project from the nuclei to the somatic sensory cortex (postcentral gyrus of the parietal lobe).

The representation of the body areas is mapped within the dorsal column lemniscal system as it proceeds towards that thalamus where it is preserved.

A signal originating in a peripheral sensory nerve is transmitted all the way to the cerebral cortex where the intensity of the signal is preserved.
Where is the somatic sensory cortex?
Lies in the anterior portions of the parietal lobes
What are the two areas involved in somatic sensory cortex?
SS area 1 and SS area II
Where is somatic sensory area 1
the Post central gyrus
How are the areas of the boy represented?
By the density of their sensory receptors.
Which areas are highly represented?
LIPS

FACE

HANDS

The trunk and lower parts of the body have small representation relative to their actual body size
The neurons of the somatic sensory cortex are arrange how? How big are they?
0.3 -0.5mm in diameter. Extend through all six layers of the cortex. Each column contains 10,000 neuron and responds to a specific sensory modality.
Injury to SSI can cause what? (4)
LOSS OF DISCRETE TACTILE SENSES

INABILITY TO JUDGE PRESSURE AGAINST THE BODY SURFACE

INABILITY TO JUDGE THE SHAPES OF OBJECTS

INABILITY TO JUDGE TEXTURE OF AN OBJECT
Where is the somatic association cortex located?
In the parietal lobe behind SSI
Where does the somatic association cortex receive input from?
Thalamus

visual cortex

auditory cortex
What is an important role of the SAC?
Interpretation of sensory information
Damage to ones Somatic association cortex can cause one to what?
Astereognosis (inability to identify objects by touch)

Forget that one side of the body exists. (amorphosynthesis)
Position sense and kinesthesis are what kind of sensation?
Proprioceptive
Where are proprioceptors located?
Sensory endings in joint capsules and ligaments. Tissue around joints and in muscle spindles.
What are some examples of joints and capsule and ligament receptors?
Ruffini end organs

Golgi tendon receptors
How are proprioceptors info transmitted?
The the dorsal column-lemiscal system.
Define Pain (IASP)
An unpleasant sensory and emotional experience associate with actual or potential tissue damage or describe in terms of such damage.
Why is pain not just physiological?
Because it is affected by past events, suggestions, and emotional arousal.
What are the two types of pain and list the differences?
Fast (first pain) aka acute pain, sharp pain, prickling pain. RAPID ONSET (0.1 sec). Arises primarily in skin. Generally not felt in deeper tissues and is well localized.



Slow (second pain) aka throbbing pain, burning pain, aching pain, chronic pain. SLOW ONSET (1sec or more). Sensation can increase with time. Can arise in skin and deeper tissues and is often poorly localized.
How do fast and slow pain transmit?
fast-TYPE A-delta myelinated

Slow-TYPE C non myelinated
What are the majority of free nerve ending called? Are they encapsulated?
Pain receptors (nociceptors).


No they are not encapsulated.
Why are pain receptors called polymodal?
They respond to mechanical, thermal and most often chemical stimuli.
What are the two types of nociceptors and where are they located?
SOMATIC NOCICEPTORS are located in the skin and deep tissues such as muscle tendons, fascia, and bone.

VISCERAL nociceptors are located in the gi tract and kidneys
What are alogens?
Bradykinins

Prostaglandin

Excess hydrogen ions
Where does the myelinated type A-delta fibers axons synapse?

FAST
Mostly with Laminae 1 and also with laminae 5
Where do nonmyelinated type C axons synapse with?
Interneurons in laminae II (sustania gelatinosa) and III

THEN

they project second order neurons to lamina V
Wide dynamic range second order neurons are most abundant where? What is significant about the WDR?
Lamina V

These neurons increase their firing rate "wind up" in response to persistent painful stimuli.
Axons of the second order neurons immediately do what?
Cross over to the opposite side of the cord and ascend in the lateral spinothalamic tracts
Where is fast pain directed too?
Primarily to the ventrobasal nuclei of the thalamus and from there via 3rd order neurons to the somatic sensory cortex and then the localization of stimulus
Where is slow pain directed too?
Primarily to the midbrain reticular formation, the pariaqueductal gray area, intralaminar nuclei of the thalamus, and the limbic system

emotional arousal and activation of descending inhibitory pathways.
What are the chemical mediators of pain?
Alogens
What is the periaqueductal gray area?
gray matter that surrounds the acqueduct of sylvius
What alogens are released from injured tissues and directly stimulate free nerve endings?
Bradykinin

Prostaglandin E2
What alogens are released from injured tissues and histamine is released?
K+ and H+
What happens with persistent stimulation of nociceptors?
primary hyperalgesia which is enhanced response to painful stimuli
Primary hyperalgesia is mediated by what?
histamine and serotonin
local collateralaxon terminals of pain afferent nerves release what? which stimulates mast cells and platelets to release alogens?
Substance P
Alogen spread to tissue surrounding the area of injury causes _______ ______ manifested by enhanced pain response to stimuli outside the area of injury.
secondary hyperalgesia
Describe the central modulation of pain. (central sensitization)
Afferent pain fibers release GLUTAMATE AND SUBSTANCE P in the dorsal horn. GLUTAMATE activates post synaptic AMPA and NMDA receptors. SUBSTANCE P activated post synaptic NK-1 receptors.
What is the common mechanism of central sensitization?
Increased intracellular calcium
What does glutamate binding to the NMDA receptor cause?
Removal of MG block and increase calcium permeability.
Central sensitization greatly enhances what? Once central sensitization is established, it is difficult to what?
Pain signal transmission and pain perception

Very difficult to interrupt even with opioids.
How does the periaqueductal gray area work to inhibit pain transmission?
Receives ascending pain activity which activates descending adrenergic tracts to the spinal cord and descending enkephalin-secreting tracts to the raphe magnus nucleus.

Raphe magnus nucleus activates the descending serotoninergic tracts to spinal cord.
What events occur in the dorsal horn?
Descending adrenergic axons release norepinephrine which ACTIVATES pre and post synaptic alpha 2 receptors. which inhibit pain neurotransmission.

Descending serotoningergic azons stimulate interneurons to release enkephalins

enkephalins bind to presynaptic opioid receptors on pain afferents and inhibit substance p release.
Which enkephalins acting in the spinal cord to inhibit pain transmission?
cousins met and leu
what is the possible mechanism of referred pain?
Visceral pain fibers synapse in the spinal cord with the same neurons that receive pain afferent fibers from the body surface
what doesnt viscera contain?
No somatic receptors except for pain receptors.
Highly localized damage may cause little what?
visceral pain
Visceral pain typical involves diffuse activation of pain receptors due to?
Ischemia

Chemical irritation

distension/spasm (cramps) of visceral smooth muscle

Stretching of ligaments
What are some examples of visceral pain?
Cardiac ischemia pain

Esophageal pain- from heartburn
Visceral pain is transmitted to the CNS by what fibers?
Autonomic type C fibers
Parietal pain is transmitted to the spinal cord via???
somatic sensory nerves
Parietal pain sensation is localized to the area directly over the???
Painful stimuli
Appendicitis is what type of pain?
Parietal
Which receptors play a critical role in central sensitization?
NMDA receptors
What is a very potent NMDA antagonist?
Ketamine
How does pre emptive acetaminophen work?
Indirect inhibitor of NMDA