Chapter 13 Anatomy and Physiology (McGraw Hill)

Cranial Nerves

12 pairs of nerves from the neck, up

Spinal nerves

31 pairs of nerves from the neck, down

What are the functions of the spinal cord?

conduction, neural integration, locomotion, reflexes

Where is the spinal cord in the vertebral canal?

In the upper two thirds

Where does the inferior margin of the spinal cord end?

At L1 (or slightly beyond)

How many pairs of spinal nerves are there?

31 pairs, 62 total (8, 12, 5, 5, 1)

Cauda Equina

"horse's tail", a fan of nerve fibers below the spinal cord

Medullary cone

shape at the end of the spinal cord with nerves that continue coming off

What are the meninges?

dura mater, arachnoid mater, pia mater

Where is the lateral horn found in the spinal cord?

Only from T2-L1

Where is cerebrospinal fluid found?

subarachnoid space

What is the posterior median sulcus?

a groove on the dorsal surface of the spinal cord

What is the anterior median fissure?

a deep, wide groove on the anterior (front) side of the spinal cord.

spina bifida

birth defect in which one or more vertebrae fail to form a complete vertebral arch for enclosure of the spinal cord (most serious form: spina bifida cystica)

What reduces the risk of spina bifida?

folic acid before conception

where is white and gray matter found in the brain?

Gray matter is superficial to white matter

where is white and gray matter found in the spinal cord?

white matter is superficial to gray matter

what makes up gray matter?

neuron cell bodies with little myelin

what makes up white matter?

myelinated axons

posterior (dorsal) root of the spinal cord carries only what?

sensory information

anterior (ventral) root of the spinal cord carries only what?

motor information

gray commissure

connects the right and left sides of the gray matter in the spinal cord

what does the lateral horn do?

connects neurons of sympathetic nervous system

What is gray matter called?

Horns (ventral, lateral and dorsal)

What is white matter called?

columns or funiculi (ventral, lateral and dorsal)

Where are spinal tracts found?

in the CNS

where are spinal nerves found?

in the PNS

What do ascending tracts do?

carry sensory information up

What do descending tracts do?

carry motor information down

decussation

The anatomical crossing over of neurons from left to right (right brain controls left side of body)

contralateral

when the origin and destination of a tract are on opposite sides of the body

ipsilateral

when the origin and destination of a tract are on the same side of the body

sensory signals travel across how many neurons from origin to destination in the sensory areas of the brain?

3

What are first order neurons?

detect stimulus and transmit signal to spinal cord or brainstem

what are second order neurons?

continues to the thalamus at the upper end of the brain

what are third order neurons?

carries the signal the rest of the way to the sensory region of the cerebral cortex

Descending tracts involve how many motor neurons?

2

upper motor neuron

originates in cerebral cortex or brainstem and terminates on a lower motor neuron

lower motor neuron

soma is in brainstem or spinal cord

schwann cells

form neurilemma and myelin sheath around the axon

endoneurium

loose connective tissue external to neurilemma

perineurium

layers of overlapping squamous cells that wrap fascicles: bundles of nerve fibers

Epineurium

dense irregular connective tissue that wraps entire nerve

what penetrates connective tissue coverings?

blood vessels

Poliomyelitis and ALS causes

both diseases cause destruction of motor neurons leading to skeletal muscle atrophy from lack of innervation

poliomyelitis

caused by poliovirus

Amyotropic Lateral Sclerosis (Lou Gehrig's Disease)

damage to motor neurons - muscles stop working but brain is still fine

ganglion

A cluster of nerve cell bodies, often of similar function, located in the PNS.

Sensory (affarent) nerves

carry signals from sensory receptors to the CNS

Motor (efferent) nerves

carry signals from CNS to muscles and glands

mixed nerves

contain both sensory and motor fibers

somatic or visceral senses

things we aren't aware of (blood pressure, heart rate, body temperature)

general senses

temperature, pain, touch, stretch, and pressure

special senses

vision, hearing, taste, smell, equilibrium

spinal nerves are _________________, roots are ________________

mixed; not

which is larger, the ventral or dorsal ramus?

Ventral

What does the cervical plexus -C3, C4 And C5 do?

Keep the diaphram alive

What does the brachial plexus innervate?

Entire upper limb

What is under the brachial plexus?

intercostal nerves with NO thoracic plexus

axillary nerve innervates

deltoid

radial nerve innervates

Extensors

Ulnar nerve innervates

flexor carpi ulnaris

median nerve innervates

pronator

lumbar plexus supplies

quads and adductors

the sacral and coccygeal plexuses supply

hamstrings (sciatic nerve)and reproductive activity (pudendal nerve)

Radial nerve injury

Passes through axilla, crutch paralysis, wrist drop

Sciatic nerve injury

Sciatica: sharp pain that travels from gluteal region along the posterior side of the thigh and leg to ankle

90% of cases result from herniated intervertebral disc or osteoporosis of lower spine

dermatome

a specific area of skin that conveys sensory input to a spinal nerve

Shingles

herpes zoster, caused by varicella-zoster virus (chicken pox)traveling down the sensory nerves when immuse system is compromised

reflexes

quick, involuntary, stereotyped reactions of glands or muscle to stimulation

reflexes include:

glandular secretion and contraction of all three types of muscle

Pathway of a somatic reflex arc

1. somatic receptors

2. afferent nerve fibers

3. integrating center

4. efferent nerve fibers

5. effectors

Patellar tendon reflex steps

Stimulation

Information Sent

Decision Make

Information Out

Something Happens

flexor reflex

the quick contraction of flexor muscles resulting in the withdrawal of a limb from an injurious stimulus

crossed extension reflex

contraction of extensor muscles in the opposite limb from the one being withdrawn - maintains balance by extending other leg

flexor relex uses an _______________ reflex arc, whereas crossed extension reflex uses a ____________________ reflex arc

ipslipateral; contralateral

intersegmental reflex

one in which the input and output occur at different levels (segments) of the spinal cord (pain in foot causes contraction of abdominal muscles)

propioceptors

monitor the position and movement of body parts (know where your body and all parts of it are is in three dimensional space)

muscle spindle

stretch receptors embedded in skeletal muscles (helps you keep upright when standing on a boat)

Stretch (myotatic) reflex

when a muscle is stretched, it "fights back" and contracts (helps maintain equilibrium and posture)

paraplegia

paralysis of both lower limbs

quadriplegia

paralysis of all four limbs

hemiplegia

paralysis of one side of the body

paresis

partial paralysis or weakness of the limbs

in the spinal cord, what is the space within the gray commissure that contains CSF?

central canal

somatic nerve fibers innervate:

skin, skeletal muscles, bones and joints

All spinal nerves except C1 pass through which structure to emerge from the vertebral column?

Intervertebral Foramen

layer of loose connective tissue that surrounds a nerve fiber

endoneurium

In an adult, the spinal cord ends at which vertebra?

L1

Within a nerve, each fascicle is wrapped in a layer called a ________

perineurium

the __________________ ramus of the spinal cord innervates the muscles, joints, and skin of the back

posterior