A and Pi Chapter 15

Describe the condition of shingles.

Shingles is a unique viral infection that almost always affects the skin of a single dermatome. It is caused by the varicella zoster virus. If the body's immunological protective mechanism becomes weakened, the virus may reactivate. The virus will travel down the sensory nerve to the skin of a single dermatome. It results in a painful eruption of red, swollen plaques or vesicles that eventually rupture and crust over in about 2 to 3 weeks. In severe cases extensive inflammation, hemorrhagic blisters, and secondary bacterial infection can occur. In most cases of shingles, the eruption of vesicles is preceded by 4 or 5 days of pain, burning, and itching.

Classification of reflex arcs According to effector tissue

Somatic reflex: skeletal muscle contraction Autonomic (visceral) reflex: smooth or cardiac muscle contraction, gland secretion

Phrenic nerves (R and L)

Source: from cervical plexus (C1-C5) Controls: the diaphragm, the main muscle for respiration

Connection between dermatomes and myotomes

Spinal nerves can receive input from dermatomes and control myotomes

Babinski sign & Plantar reflex

Stimulus: stimulation of margin of outer sole leads to either the Babinski sign/reflex OR the plantar reflex Babinski sign/reflex: extension of great toe, with or without fanning of other toes, Present in normal infants (<1½ year old) Absent in normal humans > 1½ year old of age due to myelination of corticospinal fibers (myelination causes plantar reflex instead) When present In humans > 1½ year old: due to destruction of corticospinal (myelinated) fibers

Dorsal ramus types of nerves and location

Type of nerves: somatic motor and sensory nerves Location: muscles and skin of dorsal surface of head, neck, and trunk

Location and functions of Sacral plexus

anterior pelvic, intermingling of fibers from L4-S4 Function: innervate skin of leg, muscles of posterior thigh, leg and foot via tibial, common peroneal, and sciatic nerves

Cauda equina:

nerves that start at the lower end of the spinal cord and it's spinal nerves, starting from L1

Ankle jerk (Achilles reflex)reflex

2 neuron reflex arc; spinal reflex; somatic; ispilateral; segmental; stretch reflex; extensor reflex; superficial

Classification of reflex arcs acording to Number of neurons

2 neuron: no interneuron 3 neuron: includes one interneuron

Knee jerk structure and function

2 neuron; spinal reflex; somatic reflex; ipsilateral; segmental; stretch reflex; extension reflex; superficial reflex

spinal nerves Sensory function

: cell bodies in dorsal root ganglion and enters through dorsal horn

Location and functions of Cervical plexus,

: deep within the neck, ventral rami of C1-C5 (part) innervate muscles and skin of neck, upper shoulders, part of head, diaphragm

Location and functions of Brachial plexus

: deep within the shoulder, ventral rami of C5-T1 innervate lower shoulder, entire arm

Location and functions of Lumbar plexus

: lumbar region of back, intermingling fibers of L1-L4 Function: innervates thigh and leg via femoral nerve

Reflex General definition

Action that results from a nerve impulse passing over a reflex arc Leads to a predictable response to a stimulus Leads to either muscle contraction or glandular secretion Often is subconscious

with age, the _______- reflex typically fades

Babinski reflex

The four major pairs of plexuses are

Cervical plexus, Brachial plexus, Lumbar plexus, Sacral plexus, Coccygeal plexus

Two functional divisions of the peripheral nervous system (PNS)

Classification according to direction of information flow: Afferent (sensory) division Efferent (motor) division Classification according to type of inputs and effectors: Somatic nervous system (SNS) Autonomic nervous system (ANS)

Describe what happens when the fifth cranial nerve is compressed.

Compression of the fifth cranial nerve results in a condition called trigeminal neuralgia. This condition is characterized by recurring episodes of intense stabbing pains radiating from the angle of the jaw along the branch of the trigeminal nerve.

Classification of reflex arcs According to location of the processing center

Cranial reflex: center of reflex arc is the brain Spinal reflex: center of reflex arc is in the spinal cord

Explain the correlation between a myotome and a specific movement of the body.

Each myotome is a segment of the body muscles supply by a specific spinal nerve. Therefore specific motions are possible or not possible, depending on the ability of specific spinal nerves to function.

Can you predict the respiratory consequences of an injury that damaged the spinal cord between the third and fifth cervical segments? What specific mechanism would cause these consequences?

Injury at this level of the spinal cord might injure the phrenic nerve. This nerve supplies the diaphragm, which permits inspiration and expiration. If this nerve is damaged, the impulses no longer reach the diaphragm and the diaphragm stops contracting. Unless artificial respiration is provided, the person dies of respiratory paralysis.

Other classifications

Ipsilateral: contained entirely on one side Contralateral: crosses over to the opposite side Segmental reflex: contained within one spinal cord segment Intersegmental: spans more than one spinal cord segment Stretch reflex: started by stretching of a muscle Extensor reflex: produced by muscles that cause extension Superficial reflex: sensory receptors are located superficially on skin surface Deep reflex: sensory receptors are located deep within a muscle

Location and functions of Coccygeal plexus

Location: S4-S5, connects with coccygeal nerve Function: supplies skin over coccyx bone

Dermatome

Location: a region of skin surface area Type of nerve: sensory fibers of a given spinal nerve Dermatome regions overlap considerably

Myotome

Location: specific sets of skeletal muscle Type of nerve: motor fibers of a given spinal nerve

Ventral ramus? types of nerves and loacation

More complex than dorsal ramus (can form plexus) Types of nerves: somatic and autonomic motor and sensory fibers Location: muscles and glands in the extremities and lateral and ventral portions of the neck and trunk Autonomic fibers: can connect with sympathetic rami and sympathetic chain ganglion

Identify the areas supply by the individual nerves emerging from the cervical plexus.

Muscles and skin of the neck, upper shoulders, and parts of the head are supply by nerves emerging from the cervical plexus. The phrenic nerve also exits at this plexus, and it innervates the diaphragm.

____ is a term referring to a skeletal muscle group innervated by motor neuron axons from a given spinal nerve.

Myotome

Spinal cord injury between C1 to C5

Paralysis of phrenic nerves Paralysis of diaphragm Cannot breathe independently

Abdominal reflex

Stimulus: stroking the side of the abdomen Reflex: drawing in of the abdominal wall Absence or decrease in reflex: indicate possible damage of motor neurons Type of reflex Superficial reflex Spinal reflex (T9-T12)

Knee jerk (patellar) reflex

Tap stretches patellar ligament and quadricep femoris tendon Stretch receptor activated Signal from stretch receptor sent via sensory nerve to spinal cord Activates lower motor neurons in L2-L4 Contracts quadriceps femoris muscle

Peripheral nervous System includes everything that is not in?

The Central nervous System

Can you distinguish between the reflexes that cause cardiac muscle to react and those that cause skeletal muscles to react?

The cardiac reflex would be an autonomic reflex. It would be mediated by impulses conducted over the autonomic reflex arcs. The skeletal reflex is a somatic reflex. The impulse would be conducted over somatic reflex arcs, that is, anterior horn neurons.

A single reflex can be classified in several ways. What example can you find that would show this? In what ways can this reflex be classified?

The knee reflex can be classified in a variety of ways. It can be classified as a spinal cord reflex, a segmental reflex, an ipsilateral reflex, a stretch (or myotatic) reflex, an extensor reflex, a tendon reflex, and a deep reflex.

Which cranial nerves transmit impulses that result in vision? In eye movement?

The optic nerve transmits impulses that result in vision. The oculomotor nerve, the trochlear nerve, and the abducens nerve transmit impulses that result in eye movement.

What pathways are found in the somatic motor nervous system?

The somatic motor nervous system includes all pathways outside the CNS. It involves the peripheral pathways to the skeletal muscles.

Ramus (rami) of spinal nerves

The spinal nerve divides into large branches, depending on the area that it will supply Rami, like spinal nerves, are mixed nerves (nerves which contain both sensory and motor nerves)

Identify the direction of the information carried by the ventral root of a spinal nerve.

The ventral root of a spinal nerve carries information away from the CNS toward the effector.

Which cranial nerves transmit impulses that result in hearing? In taste sensations?

The vestibulocochlear nerve transmits impulses that result in hearing. The facial nerve, the glossopharyngeal nerve, and the vagus nerve transmit impulses that result in taste.

An adult has an extension of the great toe and the fanning of the other toes in response to stimulation of the outer margin of the sole of the foot. Why is this a concern, and where would the problem most likely be?

This would be a Babinski reflex, which should not occur in an adult. This usually means that there has been damage to pyramidal tract (corticospinal) fibers.

spinal nerves Motor function

cell bodies in ventral horn of spinal cord and leaves spinal cord through ventral horn

Nerve Plexus definition

complex networks formed by the ventral rami of most spinal nerves (not T2 through T12) subdividing and then joining together to form individual nerves

dorsal (posterior) root:

contains only sensory neurons from that section of the spinal cord

ventral (anterior) root:

contains only ventral motor neurons from that section of the spinal cord

Which is FALSE of the dorsal nerve a- It is also called the posterior root. b- It includes a ganglion. c- It includes sensory fibers. d- It includes motor fibers. root?

d- It includes motor fibers. root?

The skin and muscle of the posterior surface of the head, neck and trunk are innervated by the branches of the

dorsal ramus

Plexus

groups of nerve that travels to and from the same location

Define mixed nerves.

is a nerve that contains both motor and sensory fibers.

Explain the concept of a dermatome.

is a section of the skin supply by a single spinal nerve. Each spinal nerve suplys a different area of the skin. By testing for sensitivity of the skin in different dermatomes, one can determine which, if any, spinal nerves have been damaged.

Dorsal and ventral roots

join together to form a mixed spinal nerve

The femoral nerve arises from the ?

lumbar plexus

All spinal nerves are

mixed nerves

Plantar reflex:

plantar flexion (curling under) of all toes and a slight turning in and flexion of the anterior part of the foot Present in normal humans > 1½ year old of age Absent in normal infants (<1½ year old)

The dorsal root ganglion contains

sensory neuron cell bodies.

Each spinal nerve attaches to

spinal cord via roots

Nerve Plexus organization

spinal nerves are rearranged according to their final destination, reducing the number of nerves needed to supply each body part Each individual nerve that emerges contains all the fibers that innervate a particular region of the body

________ is Not is the peripheral nervous system

the brain

Somatic nervous system (SNS) control? Sensory input from? Motor output to? function? excludes

voluntary from special senses (eyes, ears, equilibrium, smell), somatic sensory neurons to skeletal muscles Function is to regulate skeletal movements needed for survival, breathing, heat production Excludes: smooth muscle, cardiac muscle, glands