KINE 433 Final Exam Study

Skeletal Muscle

Voluntary; regulated by the CNS

Muscle fibers are

Multinucleated

Sarcomere is the ________ of a myofibril

Functional unit

Thick filaments are composed of

Myosin

Thin filaments are composed of

Actin, tropomyosin, and troponin

The intent to exercise arises in the _______ of the brain

Motor cortex

Central Command activates which things simultaneously?

Muscle, cardiovascular system, and respiratory system

Motor Unit

An alpha motor neuron and all the muscle fibers it innervates

An alpha motor neuron releases

ACh, which turns an electrical signal into a chemical one

ACh binds to

A nicotinic receptor, turning a chemical signal into an electrical one

The sarcoplasmic reticulum releases

Ca++

Ca++ binds to

Troponin

In a fully contracted muscle contraction

Myosin head tilts; ATP binds to myosin head; myosin head detaches

Muscle contraction stops when

Central command is removed; ACh is degraded; Ca++ is pumped back into the SR

Type I fibers

High mitochondria; high capillary network

Type IIa fibers

Moderate mitochondria and capillary network

Type IIx fibers

Low mitochondria; low capillary density

Type I fibers make up what % of muscle?

50%

Type IIa fibers make up what % of muscle?

45%

Type IIx fibers make up what % of muscle?

5%

Which muscle fiber type is extremely hard to recruit?

Type IIx

Force developed is greater in type ____ motor units

Type II

Why do type II motor units generate more force?

Larger diameter; more muscle fibers are innervated per motor unit

Endurance athletes have a higher percentage of which fiber type?

Type I

Power athletes have a higher percentage of which fiber type?

Type II

When is fat the preferred fuel?

During rest and exercise

Why is fat the preferred substrate?

We have a lot of it; it generates more energy per gram

What is the problem with using fat as a substrate?

Rate of ATP production from fat is too slow

Crossover point

Shift from fat to CHO metabolism

What are 2 effects of recruiting fast-twitch fibers?

Increases lactate production; lactate inhibits fat metabolism/lipolysis

When is the ATP/PCr system dominant?

During the first 30 seconds of exercise

When is the glycolytic system dominant?

Between 30 and 120 seconds

When is the oxidative system dominant?

After 2 minutes

ATP-PCr system

Reaction occurs in the cytoplasm

Glycolysis

Breakdown of glucose to produce pyruvate

Where do glycolysis reactions occur?

Cytoplasm

In the energy investment phase

2 ATP are used to

In the energy payoff phase

4 ATP and 2 NADH are produced

Hexokinase

Phosphorylates glucose; traps glucose in cytoplasm; 1 ATP consumed

PFK

Phosphorylates fructose; 1 ATP consumed; rate-limiting enzyme

When O2 is deficient, PA is converted to LA by

Lactate dehydrogenase

When O2 is plentiful, PA and NADH

Enter mitochondria for oxidative metabolism

The Krebs cycle and electron transport chain occur in the

Mitochondria

Krebs cycle makes how many ATP per pyruvate?

15

Krebs cycle makes how many ATP per glucose?

2

The Krebs cycle produces what as a waste product?

CO2

NADH and FADH2 lose electrons to

The electron transport chain

Hydrogen ions are pumped

Across and out of membrane

Electron transport chain is located in the

Inner membrane

In a perfect world, oxidation of 1 glucose yields

38 ATP

In the real world, 1 glucose yields

32 ATP

Beta oxidation

Process by which FFA are converted to acetyl CoA

Endurance activity increases COX activity, which enhances the rate of

ATP produced

ACh released into NMJ binds to

Nicotinic receptors

Sympathetic nerves bind

Adrenergic receptors

Group III afferent nerves are

Mechanoreceptors

Group IV nerves are

Metaboreceptors

Goal of glucose regulation

To keep glucose levels at 70–110 mg/dL

Insulin promotes

Glucose uptake

Plasma glucagon ______ during exercise

Increases

ADH helps protect against

Dehydration

ADH release starts at about

50% VO2 max

Decreased plasma volume and blood pressure during prolonged exercise activates

Renin-Angiotensin-Aldosterone System

Angiotensin II constricts arterioles, protecting

Blood pressure

Aldosterone acts on kidneys to

Reabsorb Na+

What percent of energy from metabolism of fat and CHO is lost as heat?

60%

Indirect calorimetry estimates energy expended by measuring

O2 consumed and CO2 produced

Respiratory Exchange Ratio can be used to estimate

Percent kcal derived from fat vs. CHO

Steady-state VO2 is reached in

1–2 minutes

Steady state

Feedback from Group III and IV nerves allows precise matching

Alpha cells release

glucagon

Insulin and glucagon are both released by cells in the

Pancreas

Renin is secreted by the

Kidneys