Exam 1: Lectures 1-5

What type(s) of muscle are striated?

Skeletal, cardiac

What type(s) of muscle are mononucleated?

Cardiac, visceral/smooth

What type(s) of muscle are under involuntary control?

Cardiac and smooth

What layer divides the individual fascicles?

Perimysium

What layer divides/separates the individual muscle cells/fibers?

The endomysium

What layer surrounds the entire muscle?

The epimysium (then fascia on top of that)

What is a fascicle?

A group of muscle cells

What is the contractile unit of individual muscle cells?

Myofibril

Muscle fibers contain CHO and Hb in the form of what?

Glycogen

Myoglobin

What is the triad as it is referred to in the muscle fiber/cell?

The terminal cisterns (2 of them) Transverse tubule

The terminal cisterns are part of which cellular organelle?

The endoplasmic reticulum

What is the thick filament?

Myosin

What is the thin filament?

Actin

What is the elastic filament?

Titin

What are the contractile proteins of muscle?

Actin and myosin

What are the regulatory proteins in muscle?

Troponin and tropomyosin

What are the structural proteins in muscle?

Titin and dystrophin

What is the function of dystrophin?

It is the protein that binds the myofibril to the sarcolemma, this is crucial for force generation

What is the role of myoglobin?

Binds oxygen in muscles

With contraction, what happens with respect to the M line?

Does not change

What can be found in the A band?

The entire length of myosin and some actin

What can be found in the I band? AKA light band

Strictly actin, titin and the Z disc

What helps to connect myosin to the z discs?

Titin

What can be found in the H zone?

The M line and strictly myosin

What happens to the H zone and I band during contraction?

They shorten

The first step in cross bridge cycling is the

binding of calcium to troponin, moving tropomyosin and exposing the active binding sites on actin

Once the myosin head is bound to the actin molecule, what happens next?

ATP will come in and get hydrolyzed , releasing the actin/myosin bond and cocking the head in a new position

At the NMJ, where does ACh bind?

The nicotinic ACh receptor

What is the resting membrane potential of the muscle cell?

-90mV

Are there any inhibitory inputs directly to the skeletal muscle?

No

the influx of what ion at the presynaptic axon terminal will result in ACh release?

Calcium

Once ACh binds to nAChR what occurs?

Na+ influx and K+ efflux—> triggers action potential that travels along sarcolemma and down the t tubules, causing a conformational change in DHPR and RYR causing Ca+ release

The dihydropyridine receptor is physically linked to ________, which helps regulate

ryanodine receptor calcium release from the SR

What role does Ca+ play in cross bridge cycling?

Binds to troponin and swivels tropomyosin out of the way, exposing the actin myosin binding site

What is the stored form of calcium in the SR? Why?

Ca++ bound to calsequestrin

This prevents precipitation in the SR

How is Ca+ sequestered after release?

the Calcium ATPase pump (SERCA)

The rate of muscle relaxation is determined by the

rate of sequestration

What do cardiac cells phosphorylate that helps increase the rate of sequestration/SERCA activity which in turn helps relax faster?

Phospholamban

The force of a muscle contraction is largely dependent on the

length of the sarcomeres prior to contraction

Motor units recruited

Generally, optimum length occurs at approx:

2.2 microns where there is optimal overlap between actin and myosin

The strength of the contraction increases with increasing

recruitment of motor units

What order do you recruit motor units?

Smallest to largest

How do motor units contract to sustain longer contractions?

By contracting alternatively over the period of time

At rest, what is the partial contraction of skeletal muscle known as?

Tonus

What are the phases of a twitch contraction?

Latent period

Contraction phase

Relaxation phase

Refractory period

What is a muscle twitch contraction?

The brief contraction of all muscle fibers in a single motor unti in response to a single action potential

When may wave summation occur?

When a second action potential triggers muscle contraction before the first one is finished. This results in a stronger contraction

What is unfused tetanus?

Sustained but wavering contraction

What is fused tetanus?

Maximum frequency of stimulation of a muscle resulting in maximum force

Where does the calcium come from that drives skeletal muscle contraction?

Sarcoplasmic reticulum

Where does the calcium come from that drives smooth muscle contraction?

Primarily the ECF but small amount from SR

Isotonic contraction is

tension is constant with changing muscle length (concentric and eccentric)

Isometric contraction occurs when

the muscle contracts but does not change length

What are some ways ATP is produced for muscular contraction?

Creatine phosphate

Anaerobic glycolysis

Aerobic cellular respiration

During high intensity exercise what is a source of fatigue?

K+ accumulation in the t tubules

ADP and Pi accumulation block Ca+ release and reducing troponin sensitivity

During low intensity exercise what is a source of fatigue?

Glycogen depletion

Central fatigue (ammonia buildup, reduces ACh in vesicles) Electrolyte depletion

What is the result of EPOC?

Replenish CP

Convert lactate to pyruvate in liver

Reload O2 onto myoglobin

Inc temp—> inc rxn rate

Inc tissue repair

Heart and breathing muscles still working harder

Each motor unit has one type of fiber (t/f)

True

What differentiates skeletal muscle fiber types?

Presence/abundance of mitochondria

Slow oxidative (most)

Fast oxidative (intermediate)

Fast glycolytic (fastest, least myoglobin and mitoch)

What can mature skeletal muscle fibers NOT undergo?

Hyperplasia

What are some age related changes within muscle tissue?

Loss of muscle tissue and replaced by connective tissue and adipose tissue

What are some consequences of the age related decline in muscle mass?

muscle strength and flexibility decrease

Slowed reflexes

Slower muscle fibers increase

What is the threshold in skeletal muscle cells?

around -70 mV

The Nervous system can be divided into the

CNS and PNS

The CNS consists of

The brain and spinal cord

How many spinal nerves are there?

31

The dorsal root is responsible for the

Afferent/sensory axons

The afferent axons are otherwise known as

sensory

What is unique to the dorsal side of the spinal cord?

The presence of dorsal root ganglia

The ventral root is responsible for

efferent/motor axons

Efferent axons are otherwise known as

motor neurons

Where does the spinal cord terminate?

L 1 vertebral level

What is the cauda equina?

“Horse tail” of nerve roots extending down past the end of the spinal cord to exit through the appropriate vertebrae

How many cervical spinal nerves are there?

8

How many thoracic spinal nerves are there?

12

How many Lumbar spinal nerves are there?

5

How many sacral spinal nerves are there?

5

How many coxygeal spinal nerves are there?

1

The white matter is predominantly (CNS)

myelinated with some unmyelinated axons (myelination= fat = white appearance)

The gray matter is (CNS)

primarily neuronal cell bodies, dendrites, unmyelinated axons and neuroglia

A nucleus in the context of the CNS

bundle of neuronal cell bodies in the CNS

A ascending spinal tract relays what ?

sensory information

A descending tract relays what?

Motor signals

A nerve is a bundle of axons in the (CNS or PNS)

PNS

A tract is a bundle of axons in the (CNS or PNS)

CNS

What is the difference between a nerve and neuron?

A neuron is a single cell meanwhile a nerve is a bundle of axons in the PNS

A bundle of neuronal cell bodies in the PNS is known as?

ganglion EX: DRG (dorsal root ganglion)

A bundle of neuronal cell bodies in the CNS is known as?

Nucleus

Most sensory/afferent neurons are ________ (unipolar or multipolar)

Unipolar

Most motor/efferent neurons are ________ (unipolar or multipolar)

Multipolar

Which side of the body would the left side of the brain control?

Right (due to crossing/decussation in the medulla)

What is the role of inter/association neurons? where are they found?

In the CNS process sensory info and elicit a motor response

Help with reflexes!

What is a reflex?

A fast, predictable automatic response to changes in the environment

Where is the integration center for the spinal reflexes?

Spinal cord (gray matter)

A polysynaptic reflex would be

sensory —> interneruon—> motor to pull away EX: Holding hand over heat

A Monosynaptic reflex would be

Direct interface between the sensory and motor neuron

EX: patellar reflex

The distribution of sensory neurons to the skin are otherwise known as?

Dermatomes

What makes a neuron multipolar?

If its cell body has multiple neuronal processes that stem off of it

What makes a neuron unipolar?

If its cell body only has one neuronal process that stems off of it

Some examples of different neuronal process include:

Purkinje cell (cerebellum)Pyramidal cell (hippocampus)