A&P Exm 4 Chpt 13
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. What would you like to do?
A) Name the 3 Meninges layers that protect & cover the spinal cord.
B) Give Locations of each
- A) Dura mater, Arachnoid mater, & Pia mater
- B) Dura mater is the outermost layer, Arachnoid is the layer in the middle and Pia mater is the innermost layer located on the Spinal cord.
Name the 6 structures that help protect & stabilize the spinal cord.
- 1) 3 Meninges layers
- 2) Cerebrospinal Fluid
- 3) Adipose
- 4) Vertebrae
- 5) Denticular ligaments
- 6) Filium terminale
A) Define Meningitis and what causes it .
B) What problems does it cause?
- A) Inflammation of the meninges caused by trauma, bacterial infections and/or viral infections.
- B) It can cause pressure to build up around the brain and b/c skull bones don't move much it can crush the brain & cause nerve damage.
A) What is a lumbar puncture (spinal tap).
B) Why is it useful medically?
A) Extraction of CSF from the epidural space.
B) The fluid is studied looking for elements such as WBC, antibodies and blood which should not be there. It is also tested for abnormal chemical levels.
Describe the size, shape, & length of a spinal cord.
3/4 inch diameter, oval & approx 18 inches long
Besides the cord, what other structure made of nerve root extensions is protected by the lower lumbar & sacral vertebrae?
Name the 2 enlargements of the cord & their locations.
The Cervical Enlargement located at the lower end of the cervical region & Lumbar Enlargement located at the lower end of the thoracic region. (lumbar enlrgmt in lumbar reg until 4yrs old, then in thoracic)
Why are the 2 enlargements of the cord thicker than other parts?
B/C they contain larger surface areas of gray matter and the actual enlargements contain both motor & sensory neorons for the limbs.
What does it mean when there is more gray area/matter?
That there is just more non-myelinated area.
What structures are innervated by the fibers associated w/the enlargements?
The upper & lower limbs.
A)What is gray matter?
B) What is it composed of?
- A) The processing center of the cord.
- B) Made up of neuron cell bodies.
What are nuclei in the Central Nervous System (CNS)?
Gray matter which contains groups of neuron cell bodies called nuclei
What substance is found in the central canal of the spinal cord?
CSF – cerebrospinal fluid
A) Describe the 3 horns of gray matter & what info is processed in each.
- Anterior – Somatic motor nuclei – skeletal muscleLateral – Visceral motor nuclei – NOT skeletal
- muscle, but is smooth muscle, glands, vessels
- Posterior – Somatic and visceral sensory
What insulating marterial is covers white matter?
How is gray & white matter in the spinal cord different than gray & white matter in the brain?
Brain: Gray matter is on the outer surface of the brain & white matter is in the inner layer of the cortex, the optic nerves, the central and lower areas of the brain (notably the Brainstem) and surrounding the central shaft of grey matter in the spinal cord.
SC: Gray matter is in the center of cord shaped like a butterfly w/White matter surrounding it.
Describe the 3 columns of white matter.
Actually 3 sets of columns: 2 anterior, 2 lateral and 2 posterior
What type of neural fibers are found in Ascending tracts?
Afferrent neurons = Sensory input
What type of neural fibers are found in Descending tracts?
Efferent neurons =Motor control
A) Compare/contrast tracts to nerves. Which are found in the CNS and which in the PNS?
Tracts are a bundle of axons in the CNS that are relatively uniform w/ respect to size and the info they carry.
Nerves are bundles of axons or nerve fibers, along with the assoc. blood vessels and connective tissues in the PNS that carry sensory info and motor commands.
What are spinal roots?
Spinal roots are spinal nerve attachments to the cord. They can be either dorsal or ventral roots.
What types of neurons are in the dorsal roots?
Dorsal roots contain sensory neurons and Ventral roots contain motor neurons.
What structures are found in the dorsal root ganglion?
Somas of sensory neurons
What types of neurons are found in the ventral roots?
Where are the cell bodies for the neurons exiting the cord through the ventral roots
In Gray matter of cord
Name and describe the three layers of connective
tissue associated with nerves
Endoneurium, Perineurium and Epineurium
Why do we say that all spinal nerves are mixed
Dorsal and ventral roots come together to make nerves therefore resulting in nerves having both sensory and motor neurons
Describe the dorsal ramus, ventral ramus and
rami communicantes. Tell where they are and what structures they innervate.
A ramus is a spinal nerve branch. A dorsal ramus is the branch on the dorsal side after the dorsal and ventral roots mix. A ventral ramus is the branch on the ventral side after the dorsal and ventral roots mix. The dorsal ramus innervate skin and skeletal muscles of the back while the ventral rami innervate the ventrolateral body surface, structures in the body wall and the limbs.
What are dermatomes and why are they clinically useful?
An area of the skin innervated by sensory fibers from a single spinal nerve. For diagnosing damage or infection of a spinal nerve or dorsal root ganglion by a characteristic loss of sensation in corresponding region of the skin.
What is a plexus?
Interwoven network of ventral rami of adjacent spinal nerves. Because they are comprised of ventral rami, they contain both sensory and motor fibers.
What nerves form the Cervical, Brachial, Lumbar, & Sacral Plexus structures.
- Cervical– C1 – C5
- Brachial – C5 – T1
- Lumbar – T12-L4
- Sacral – L4 – S4
Where in the body do nerves of the Cervical, Brachial, Lumbar, & Sacral Plexus go?
Cervical– head, upper shoulders and phrenic nerve
Brachial– upper limbs
Lumbar– anterolateral abdominal wall, genitals, & part of legs
Sacral– sciatic nerve, buttocks and most of lower limbs
What nerves come out of each plexus?
Cervical plexus – phrenic nerve
Brachial plexus - musculocutaneous nerve
Lumbar plexus – genitofemoral nerve, femoral nerve & the lateral femoral cutaneous nerve
- Sacral plexus – sciatic nerve, pudendal nerve
A) What are the intercostal nerves?
B) Why don’t they form a plexus?
- A) Nerves of T2 – T12.
- B) B/C the ribs are in the way
What is a reflex and how do they help
Rapid, automatic responses to specific stimuli. Reflexes preserve homeostasis by making rapid adjustments in the fxn of organs or organ systems.
Define, compare/contrast cranial & spinal reflexes.
- Cranial processed in the brain and can involve thought or no thought and can be simple or complex.
- Spinal processes in the spine and involve no thought, therefore are simple.
Define, compare/contrast somatic, & visceral reflexes.
Define, compare/contrast innate & acquired reflexes.
Define, compare/contrast polysynaptic and monosynaptic reflexes.
What is a reflex arc and what are the 5 basic
components of it?
The complete path of a single reflex from start to finish. Receptor, sensory neuron, integration center, motor neuron and effector.
What happens at each step in the arc?
Define ipsilateral reflex arc & contralateral reflex arc.
Ipsilateral reflex arc is a reflex involving everything on the same side of body. (Everything = stimulus, processing & response)
Contralateral reflex arc is a reflex involving stimulus, processing or response between both sides of the body.( Ex:Balance)
What is a stretch reflex (what happens)?
Prevents muscle from over stretching. Muscle spindle detects overstreching, triggers stretch reflex to prevent pulls or tears. – tells muscle to contract when getting too long!
What type of injury does a stretch reflex protect against?
Prevents pulls & tears
A) What types of cells serve as receptors?
B) Is it monosynaptic or polysynaptic?
C) Is it ipsilateral or contralateral?
Give example of astretch reflex.
What happens in a withdrawl reflex?
Proactive reflex to move away from stimulus.
What types of injuries does a withdrawl reflex protect against?
Minimize damage to body - pain
What types of stimuli might initiate a withdrawal?
Is the withdrawal reflex monosynaptic or polysynaptic?
Is the withdrawal reflex Ipsilateral or contralateral?
Give examples of a couple withdrawal reflexes at work.
Drop hot pan
What happens in a crossed extensor reflex?
Is a crossed extensor reflex ipsilateral or contralateral?
Is a crossed extensor reflex monosynaptic or polysynaptic?
What is the purpose of the crossed extensor reflex?
In the ex of stepping on a tack, the Crossed Extensor Reflex works with the withdrawal reflex so when you pull the one foot up the other leg strengthens to hold the entire weight of your body. Without this reflex, you would fall right on your face.
What would you like to do?
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