chapter 10

muscles

what is motor neuron?

the cells in the brain and spinal cord that allows us to move, speak, swallow and breath by sending commands from the brain to the muscles.

what does the axon terminal do in the **Motor End-Plate and Innervation?**

The part of the axon that releases the neurotransmitters that relay signals across a synaptic terminal.

what happens after the axon terminal?

It triggers the movement of synaptic vesicles towards the membrane releasing its neurotransmitter in the synaptic cleft.

what is the role of the Acetylcholine in the neuromuscular junction?

diffuse across the sympatric cleft and binds receptors in the sarcolemma.

than broken down into 2 components

The neurotransmitter in the neuromuscular junction

causes depolarization, which is when the membrane becomes more permeable to sodium.

explain the steps of Depolarization.

1. generation of the end plate potential on the sarcolemma
2. generating and propagation of action potential

what is a sympatic cleft?

a narrow space that separates the axon terminal of the neuron from the motor end plate.

explain the steps of Action potential.

1. A propagated along the sarcolemma and down the T tubules
2. calcium ions are released.

what are the steps of muscle relaxation in order?

1. calcium is absorbed, beginning relaxation cycle; ATP is required.
2. muscle lengthens and relaxes

define sarcomere.

•The region from one Z-line to the next Z-line, functional unit of a skeletal muscle fiber.

what is myofilaments?

Protein filaments that make up the myofibrils of skeletal muscle cells.

responsible for muscle contraction

what’s the name of the two types of myofilaments?

Thick (myosin) filaments, **Troponin, Tropom**

Thin (actin) filaments

what’s the layer that surrounds the muscle organ?

Epimysium

What’s the layer that surrounds the muscle fascicles?

permiysium

muscle fibers contain many ?

myofibrils

What surrounds each muscle fibers?

endomysium (The innermost layer)

what does a muscle fiber contain?

many myofibrils

Myofibrils is surrounded by?

sarcoplasmic reticulum which is the cytoplasm of a muscle cell

sarcoplasmic peculium consists of?

sarcomeres that contain thick and thin filaments

Define tendon.

a fibrous connective tissue that attaches muscles to bone.

aponeurosis is.

a thin sheath of connective tissue that helps connect your muscles to your bones similar to tendons.

What are the 4 common properties of muscle tissue?

Excitability

contractibility

Extensibility

Elasticity

What are the functions of muscle?

Movement

posture Maintenace

joint stability

heat generation

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How does excitability work?

responds to certain stimuli by producing action potentials or impulses of electrical signals.

define contractibility.

ability of the muscle to shorten.

what is extensibility?

muscle and muscle cell to be stretched.

define elasticity?

ability to return to normal size and shape after being stretched.

when Active Sites Exposed what happens?

Calcium interacts with troponin causing a conformation change in tropomyosin, which exposes actin’s active site. \n

what’s the cross-bridge form?

myosin heads attach to actin at active site. \n

How is Myosin Heads Pivot ? \n

resulting in the movement of the actin filaments towards the Z-disc. Then the attached ADP and phosphate group are released.

explain Cross-Bridges Detach?

A new molecule of ATP attaches to the myosin head, causing the cross-bridge to detach

Reactivate the Myosin Head is when

The myosin head hydrolyzes ATP to ADP and phosphate, which returns the myosin to the cocked position. \n

what happens in the latent period?

A single muscle twitch has a latent period, During the latent period, the action potential is being propagated along the sarcolemma

what happens in the contraction phase?

a contraction phase when tension increases, and During the contraction phase, Ca++ ions in the sarcoplasm bind to troponin, tropomyosin moves from actin-binding sites, cross-bridges form, and sarcomeres shorten

what happens in the relaxation period?

relaxation phase when tension decreases as Ca++ ions are pumped out of the sarcoplasm and cross-bridge cycling stops.

what is a motor unit?

all muscle fibers controlled by one motor neuron

Motor units can be recruited to increase muscle tension

explain what a muscle tone is.

some muscle units are always active (even during relaxation)

what causes muscle tension?

depends on number of muscle fibers stimulated + tension produced by each muscle fiber

what is a treppe?

When muscle tension increases in this manner it looks like a set of stairs, it is called treppe. The bottom of each wave represents the point of stimulus

wave summation is

muscle stimulated before complete relaxation

Whats a tetanus?

if the frequency increases to the point where maximum tension is generated and no relaxation is observed then the contraction is called tetanus

type of muscle contracts:

muscle length does not change.

isometric contraction (no movement)

define concentric contractions.

the muscle tension rises to meet the resistance then remains stable as the muscle shortens. (shortening)

(lengthening) length of muscle increase tension

what’s eccentric contraction?

What are the types of muscle fibers?

fast twitch and slow twitch

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define slow twitch

fibers contain more mitochondria which means produce more energy

don’t require much oxygen.

suited for short, fast brusts of activity

fast twitch

enlargement of muscle (in size)

**Hypertrophy**

– decrease in size of muscle

atrophy

what is paralysis?

loss of voluntary control of muscle

disease where motor neurons are destroyed

**Polio**

muscle do not relax (problem with neurons)

**Tetanus**

what is **Botulism?**

blocks release of ACh into NMJ

loss of ACh receptors, weakness in the muscle for eye movement, facial expressions, and swallowing

**Myasthenia gravis**

destroys shape of neurons is a disease of the central nervous system.

**Multiple Sclerosis**

expain what **Rigor mortis is**

sustained muscle contraction (due to no ATP), stiffing of the body’s muscles following death

what is a cardiac muscle?

•Intercalated discs are part of the cardiac muscle sarcolemma, and they contain gap junctions and desmosomes.

define smooth muscle.

•Smooth muscle tissue is found around organs in the digestive, respiratory, reproductive tracts and the iris of the eye.