Animal Phys Ch. 13

Specialized Muscles

What are the three specialized muscle systems in Lecture 13?

Superfast muscles, electric organs, and brain heaters

What makes superfast muscles unusually fast?

Rapid myosin ATPase activity and calcium cycling

Name three uses of superfast muscles.

Sound production, echolocation, and rattlesnake rattling

What do superfast muscles produce in fish and birds?

Sound

What do superfast muscles help bats perform?

Echolocation

What do superfast muscles produce in rattlesnakes?

The rattle

Which muscles are highlighted as the fastest known vertebrate superfast muscles?

Bird sonic muscles

How fast can bird sonic muscles twitch?

About 250 times per second

What happens when calcium binds troponin C?

Tropomyosin shifts and exposes actin-binding sites

What causes myosin to detach from actin?

Binding of a new ATP molecule

What are electrocytes?

Modified skeletal muscle cells lacking myofibrils

What do electrocytes produce?

Electrical discharges

How do electrocytes respond to neural signals?

Membrane potential changes produce electrical discharges

What maximum electric discharge is cited in Lecture 13?

Up to 600 volts

What are three functions of electric organs?

Stunning prey, communication, and navigation

Which fish are examples of animals with brain heaters?

Swordfish and other predatory fish

What are brain heaters derived from?

Modified eye muscles lacking myofibrils

Why do some fish have brain heaters?

To keep eyes and brain functioning in cold deep water

What process generates heat in heater cells?

Prolonged calcium cycling at the SR

Why are heater cells rich in mitochondria and myoglobin?

To support ATP production and oxygen supply

What is reaction time?

Time from stimulus presentation to the response

Can voluntary reaction times improve with learning?

Yes

What is a reflex arc?

Neural pathway producing an involuntary response

Why do reflex arcs minimize synapses?

To produce rapid protective responses

Name three reflexes from Lecture 13.

Stretch, flexion withdrawal, and crossed extension

What is the stretch reflex?

Muscle contraction in response to stretch

What is the flexion withdrawal reflex?

Pulling a body part away from a harmful stimulus

What is the crossed extension reflex?

Opposite limb extends to help support the body

Can a spinal reflex occur before conscious awareness?

Yes

What structures connect cardiac muscle cells?

Intercalated discs

What are two functions of intercalated discs?

Mechanical strength and rapid cell communication

What allows cardiac cells to communicate electrically?

Gap junctions

Why does cardiac muscle not undergo tetanus?

Its long absolute refractory period prevents summation

Can cardiac muscle initiate its own excitation?

Yes

Which nervous system regulates cardiac muscle?

Autonomic nervous system

Does smooth muscle contain troponin?

No

Does smooth muscle contain sarcomeres?

No

Which calcium-binding protein regulates smooth muscle contraction?

Calmodulin

Why can smooth muscle maintain long contractions efficiently?

Slow myosin ATPase and slow calcium removal

What is a muscular hydrostat?

A muscular structure that moves without bones or joints

Name three muscular hydrostats.

Tongue, elephant trunk, and octopus arms

What principle allows muscular hydrostats to change shape?

Muscle tissue is nearly incompressible

What causes bending in a muscular hydrostat?

Asymmetric contraction of longitudinal muscles

What do helical muscles help an elephant trunk do?

Twist