Chapter 13

What relevance does the sea squirt have for our understanding of the nervous system?

The observation that both sensory and motor neurons are lost when an animal no longer needs them to move, suggests that the brain is primarily a motor system

What are the three general types of coordinated movements?

Voluntary, reflexive, and repetitive

The basic unit of motor control is the __ It consists of what two components

Motor unit: motor neuron and the muscle fibers it innervates

Name the three types of skeletal muscle

Slow, fast fatigue resistant, and fast fatigable

What are the three ways in which skelatal muscles differ?

They differ in terms of speed, Force of contraction, and fatigability

Name the three types of excitable tissues

Muscle Neurons glands

Skeletal muscle is made up of bundles of

Muscle fibers

What are muscle fibers made of?

myofibrils

What is the smallest contractile unit of skeletal muscle?

Sacromere

What type of muscle is a chicken breast? What type of muscle is a chicken leg?

Fast or white muscle: slow or red muscle

What is the literal meaning of sarcophagus

Flesh eater: Greek origin

Myoblast

An embryonic cell that develops into muscle tissue

Because of their size, extrafusal motor neurons are referred to as

Alpha motor neurons

In situations requiring precise, muscle control, are there more or fewer muscle fibers per motor neuron

Fewer

Does Muscle tissue undergo action potentials when stimulated

Yes, they are often called muscle potential’s

What is the name of the synapse between a muscle and nerve?

Neuromuscular junction

what neurotransmitter is released at the neuromuscular junction?

Acetylcholine ACh

Does the release of ACh at neuromuscular junction always cause contraction

Normally, yes

The neurotransmitter released onto the muscle, causes what channels to open

What ion is then released within the muscle fiber

Sodium (Na+)

Muscle fiber, depolarizes, and calcium is released within the fiber

The level of muscle force is controlled by what two factors

Rate of action potential’s, and number of motor neurons (or motor units) firing

Is the contraction of a sacromere all or none

No, it can contract partially

After ACh binds with a receptor, it is removed from the synapse by the chemical

Acetylcholinesterase AChE

In one word, what is the effect of curare or Botox on the muscles?

Paralysis

What are the Mechanisms of CURARE, or Botox

Curare Binds at the muscle receptor and prevents ACh from stimulating Botox permanently blocks the release of ACh from the nerve terminal

What does ALS stand for?

Amyotrophic lateral sclerosis

What is the cause of ALS

Both the upper motor neurons in the brain and the alpha motor neurons in the spinal cord die

What is the cause of myasthenia gravis

Immune system destroys the receptors on the skeletal muscles

Given the cause of myasthenia you should be able to suggest two treatments

Suppress the immune system, and or administer an anticholinesterace What slows the removal of ACh from the neuromuscular junction

What is the cause of muscular dystrophy

Genetic disorders in which the muscles degenerate in many cases, it is due to lack of a particular protein needed by the muscle tissue

What researcher won a Nobel prize for his work on reflexes? Was he awarded the prize before or after World War I?

Charles Sharington after World War I

What two neurons are involved in the monosynaptic portion of the stretch reflex

Muscle spindle, neuron and alpha motor neuron

What is the term for a muscle that works together with another muscle?

Synergistic

Does a Muscle spindle fire, when a muscle lengthens or shortens

When it lengthens

Name three causes of a reduced stretch reflex

A problem with the muscle spindle afferent, problem with the alpha motor neuron or axon, muscle problem (atrophy or stiffness)

Name two causes of an exaggerated stretch reflex

Loss of descending inhibition to the motor neuron or patient less than a year old

Is The function of the stretch reflects to maintain a constant muscle length or a constant limb position

limb position. Synergistic Muscles that were not stretched also shorten

Give an example of a suprasegmental reflex

withdrawal to a painful stimulus by a four-legged animal

Would you expect a reflexive withdrawal to a painful stimulus to be faster than a stretch reflex?

slower because stretch reflex has fewer synapses, which slows down neural transmission (also, the sensory fiber to the muscle spindle is a faster fiber than the pain fibers)

Flexion or extension? Bending an elbow_________ Reaching out with a hand

flexion; extension

The neural networks in the central nervous system involved in coordinating repetitive movements are referred to as what

central pattern generators

Studies in which the output of motor neurons is recorded, but actual movement is blocked are said to study what type of locomotion?

fictive

Figure 13.13 illustrates the pattern of motor neuron firing to the muscles involved in swimming. What muscle contracts right after the hip extensor?

hip flexor

Although human walking involves spinal pattern generators, the fact that we are walk on two legs means that the motor neurons also require sensory input from what sensory system?

vestibular system (balance)

The fact that number of muscles involved in a withdrawal reflex depends on the intensity of the painful stimulus indicates what?

the spinal cord is able to take the intensity of a sensory stimulus into account without the involvement of the brain

There are __________ main motor pathways that descend from the brain. They are grouped together in __________ main systems, which are named for what? _________

four; two; location of tracts in the spinal cord

In Figure 13.14, what is the plane of section of the top brain illustration (a)? ______________ Of the bottom illustration (e)? __

frontal (or coronal)

cross sectional

In Figure 13.14a, why are some areas colored more lightly than others?

The lightly colored areas indicate fiber tracts that normally look lighter than the nuclei, which contain cell bodies, because the fibers have myelin sheaths

In Figure 13.14e, why has the artist colored the central portion of the spinal cord darker than the surrounding portion?

The central portion contains cell bodies that are darker than the surrounding tracts which contain myelinated fibers

In Figure 13.14e, why has the artist colored the ventral portion of the spinal cord darker than the dorsal border?

The artist made a mistake--both the dorsal and ventral portions of the spinal cord in this section are made up primarily of myelinated fibers and should be lightly colored

What three criteria are used to determine if an area of cortex is motor?

. it connects to other motor areas, damage to it affects movement, stimulation causes or affects movement

Name two electrophysiological techniques used to study motor cortex.

stimulate and observe movement, record neural responses during movement

In what lobe is motor cortex?

frontal

What are the different areas of motor cortex?

primary (or M1), supplementary, and premotor

Most of the descending motor projections come from which subdivision?

What is the name of the tract that carries these fibers?

primary or M1

corticospinal (or pyramidal) tract

does stimulation of motor cortex cause movement on the ipsilateral or contralateral side of the body?

contralateral

On what gyrus is primary motor cortex located? _____________________ What functional area is located posterior to it? ____

precentral; somatosensory cortex

Would a disorder resulting from damage to primary motor cortex be considered an upper motor neuron disorder?

yes

What is the name of the large neurons located in primary motor cortex?

Betz cells

What difference do you find when you stimulate motor cortex with ½-second electrical pulses as opposed to 1/20-second pulses?

longer pulses result in coordinated movement whereas shorter pulses result in muscle twitches

Does motor cortex control specific muscles? _____

no

How would you describe the role of motor cortex?

it codes movements

Is there much different between the effects of damage to the corticospinal tract and damage to primary motor cortex

no

What is the term for weakness on one side resulting from an upper motor neuron lesion?

Is such a lesion more likely to affect the proximal or distal muscles?

hemiparesis

distal

Define proximal and distal.

proximal means nearer the center of the body whereas distal means a body part that is further away (distant)

. What are the effects of a lesion of primary motor cortex?

initial paralysis and depression of reflexes followed by exaggerated reflexes and paresis

Following damage to motor cortex: Is maximum recovery of function achieved after 30 days, 6 weeks, or 6 months? __________ Which remaining neurons can help take over a function?

6 months; those serving the same body part

If the cortical area controlling the left arm is damaged, what can you do with the right arm to help recovery? ____________________________In what two ways can drugs aid recovery? _

. restrict its use; limit extent of neural damage and aid recovery of the neurotransmitter systems

. Rat studies have shown that overusing an impaired limb during the first 7 days following cortical damage has what effect on recovery?

can enlarge the cortical lesion, making the deficits worse

. Name two disorders caused by damage to the basal ganglia and their causes.

Huntington's disease (or Huntington's chorea) due to a genetic defect on chromosome 4, causing degeneration of the caudate nucleus and putamen, and Parkinson's disease due to loss of dopamine-producing neurons in the substantia nigra

Name five nuclei that make up the basal ganglia

. caudate nucleus, globus pallidus, putamen, substantia nigra, subthalamic nucleus (and, not mentioned in the book, nucleus accumbens)

What three factors indicate that the basal ganglia play a role in movement?

. damage causes motor disorders, they receive input and send output to motor structures, the response of some of their neurons are correlated with movement

Do the basal ganglia have non-motor functions?

yes

You notice that an elderly gentleman’s hand has a tremor that goes away when he picks up something. What do you call this tremor?

Name a chemical that can treat its symptoms. ____ ____________________________ What has been found to offer some protection from developing this disease?

. resting tremor sign of Parkinsons

; L-dopa; cigarette smoking

To what does “chorea” refer?

dance

Is Huntington’s disease sex-linked? _____________ Is it dominant or recessive?

no; dominant

What is one obvious sign of brain damage in Figure 13.20A? _______________________________ What is the plane of orientation of this figure? ____

enlarged ventricles; coronal (frontal)

Why is there no thalamus shown in Figure 13.20? __________________________________________ Does this figure appear to be stained with a cell or fiber stain? ______

the section is too far forward to pick up the thalamus; cell (the cortex is darker than the fibers going to it)

What large cell is found in the cerebellum?

Purkinje cell

In what layer is it found?

Purkinje layer

How many layers are there in cerebellar cortex?

How many of these layers contain cell bodies?

4

3

The input and output to the cerebellum flows through what structures?

cerebellar peduncles

The output from the cerebellum comes mainly from what neurons?

neurons in the deep cerebellar nuclei

. Name and briefly describe the type of tremor that is associated with damage to the cerebellum

. intention tremor; tremor begins when movement begins and stops when movement stops

The lack of coordination caused by cerebellar damage, referred to as a “drunken walk”, is technically known as what?

cerebellar ataxia

The breaking down of smooth movements into their component parts, which can occur following cerebellar damage, is known as what?

decomposition of movement

. Cerebellar damage impairs the ability to reach out and touch a moving object. Such movements are known as what?

ballistic movements

Which structure of the human brain contains the most neurons?

cerebellum

What is the largest neuron in the brain and where is it found?

Betz cell; motor cortex

what motor structure is involved in smoothing out movements?

cerebellum

. What do the following words or parts of words mean? Sclerosis

a hardening

myo

muscle

trophic

nourishment

a

without

dys

bad

sarco

flesh

phago

to eat

What causes a muscle to stay contracted?

Repeated stimulation by the motor neuron

Parkinson's disease progresses from a resting tremor to muscle

rigidity

Does a motor neuron innervate more than one muscle fiber? __________ More than one muscle? _________

yes; no

What is the term for muscle weakness due to upper motor neuron damage?

paresis