Anatomy and Physiology Exam 4

What are the 3 types of muscle tissue?

Skeletal, cardiac, smooth

Which muscle types are striated?

Skeletal and cardiac

Which muscle type is voluntary?

Skeletal

Which muscle types are involuntary?

Cardiac and smooth

What is muscle tension?

Force generated by contraction

What are myokines?

Hormones released by muscle

What is glycemic control?

Regulation of blood glucose

Role of muscles in heat?

Heat production

What is sphincter control?

Regulating passage through openings

What is joint stabilization?

Maintaining joint position

What is excitability?

Respond to stimulus

What is conductivity?

The ability to spread electrical signal

What is contractility?

Ability to generate force

What is extensibility?

Ability to stretch

What is elasticity?

Recoil

What are the five properties of muscle?

Excitability, conductivity, contractility, extensibility, elasticity.

List smallest → largest muscle structure.

Myofilament, Sarcomere, Myofibril, Fiber, Fascicle, Muscle

List connective tissues smallest → largest.

Endomysium, Perimysium, Epimysium

What is fascia?

Anchors muscle groups.

What is a tendon?

Connects muscle to bone.

What is a myocyte?

Muscle cell.

What is the sarcoplasm?

Cytoplasm.

What is the sarcolemma?

Cell membrane of the muscle fiber.

What is the sarcoplasmic reticulum?

Stores calcium.

What are myofibrils?

Bundles of myofilaments.

What is a triad?

T-tubule and 2 terminal cisterns.

What is the thick filament?

Myosin.

What is the thin filament?

Actin.

What are examples of contractile proteins?

Actin and myosin.

What are examples of regulatory proteins?

Troponin and tropomyosin.

What is the function of troponin?

Binds calcium.

What is the function of tropomyosin?

Blocks actin sites.

What exposes actin?

Calcium binding troponin.

What is titin?

An elastic stabilizer.

What binds actin?

Myosin heads during contraction.

What produces tension?

Actin-myosin crossbridge.

What is a sarcomere?

Functional unit (from z-band to z-band).

What is the z-band?

Looks like a zigzag, marks sarcomere boundaries and anchors actin filaments.

What is the i-band?

A light colored band that only has thin filaments.

What is the a-band?

A dark colored band that spans the entire length of the thick filaments.

What is the H-zone?

The pale central region within the a-band where only thick filaments are.

What is the m-line?

The center line of the sarcomere that splits the H-zone.

Which zones/bands shorten during muscle contraction? Which are unchanged?

The i-bands and h-zones shorten, and the a-bands and m-line are unchanged.

What is membrane potential?

The difference in electrical charge between the inside and outside of a cell membrane, typically measured in millivolts.

Which side of the membrane is negative, and which is positive?

Inside is negative, outside is positive.

What is resting membrane potential?

-70mV.

Where are sodium and potassium?

Sodium is outside and potassium is inside.

Explain the sodium potassium pump.

3 potassiums leave for 2 sodiums that enter. It requires ATP and enables signaling.

What are the parts of the neuromuscular junction?

Axon terminal, synaptic cleft, motor end plate.

What is the neurotransmitter that opens ligand channels? Which ion enters?

Acetylcholine, sodium enters.

What triggers release of acetylcholine? What breaks ACh down?

Calcium, acetylcholinesterase breaks it down.

What is the effect of botulism?

Blocks acetylcholine, results in paralysis.

What is botox used for?

Muscle relaxation.

What is an action potential?

Rapid voltage change.

What is the depolarization ion and what is the repolarization ion?

Sodium and potassium (respectively).

What propagates the action potential?

The sarcolemma and t-tubules.

What triggers the contraction?

The action potential at t-tubules.

What are the steps from the neuromuscular junction to the muscle action potential?

Action potential arrives at axon terminal, calcium enters axon terminal through voltage gated channels, calcium causes synaptic vesicles to release ACh, ACh diffuses across synaptic cleft and binds to ligand gated sodium channels on motor end plate, sodium enters muscle fiber, local depolarization creates end plate potential, and when the threshold is reached, voltage gated sodium channels open and action potentials spread along sarcolemma.

What are the steps of excitation-contraction coupling?

Action potential travels along sarcolemma and down t-tubules, t-tubules activate voltage sensitive proteins, calcium is released from sarcoplasmic reticulum and enters sarcoplasm, calcium binds to troponin which changes shape, tropomyosin shifts off actin binding sites, myosin binds to actin, muscle is ready for cross-bridge formation.

What are the steps of the cross-bridge cycle?

Myosin head is cocked with ADP and Pi, myosin head binds to actin, Pi is released, power stroke occurs, ADP is released, new ATP binds, myosin detaches from actin, ATP is hydrolyzed, myosin head returns to cocked position.

What are the steps of muscle relaxation in skeletal muscle?

Nerve signal stops so no ACh is released, ACh is broken down by acetylcholinesterase, sodium channels close, calcium is pumped back into the SR and leaves troponin, tropomyosin covers actin binding sites, cross bridge cycling stops.

What are the phases of twitch?

Latent, contraction, relaxation.

What happens during the latent phase?

Action potential spreads.

What happens during the contraction phase?

Tension builds.

What happens during the relaxation phase?

Calcium decreases.

What is the refractory period?

The brief time interval following an action potential during which a muscle fiber cannot be re-stimulated to contract.

What is wave summation?

The phenomenon where rapid, successive neural stimuli cause muscle fibers to produce a stronger, sustained contraction by adding to previous twitches before complete relaxation

What is tetanus?

A sustained, maximum contraction caused by rapid, repeated stimulation from a motor neuron, preventing muscle relaxation between impulses.

What are the contraction types?

Isometric, concentric, eccentric.

What are the ATP sources in order of most immediate to slowest?

ATP, CP, anaerobic glycolysis, aerobic respiration.

What is recruitment?

Increasing motor units for larger force.

Where is smooth muscle found and what are its main functions?

Found in walls of hollow organs, eye, skin, and some ducts. Functions include peristalsis, sphincter control, and regulating flow.

Why does smooth muscle lack striations?

Because it does not have sarcomeres. Instead, actin and myosin are arranged diagonally/spirally, not in organized bands.

What structures replace Z discs in smooth muscle, and what is their function?

Dense bodies replace Z discs. They anchor actin filaments and transmit force across the cell.

Compare structural features of smooth muscle vs skeletal muscle.

Smooth muscle has no sarcomeres, no T-tubules, less developed SR, and relies more on extracellular Ca, while skeletal muscle has organized sarcomeres, T-tubules, and extensive SR.

Where does Ca²⁺ come from in smooth muscle and why is this important?

Mostly from extracellular fluid (not just SR). This makes contraction slower but longer-lasting.

What protein replaces troponin in smooth muscle, and what does it do?

Calmodulin replaces troponin. It binds Ca²⁺ and initiates contraction.

What is MLCK and what role does it play?

Myosin light-chain kinase (MLCK) is activated by Ca-calmodulin and activates myosin ATPase, allowing cross-bridge cycling.

List the steps of smooth muscle contraction (simplified but complete).

Calcium enters cell, binds calmodulin, activates MLCK, activates myosin,cross-bridge cycling, contraction

How does smooth muscle relaxation occur?

Calcium is removed from cytosol, calmodulin inactivates, MLCK inactive, cross-bridges stop, muscle relaxes

What is the latch state and why is it important?

A state where smooth muscle maintains contraction with very little ATP use, important for things like blood vessel tone and sphincters.

What are the two types of smooth muscle?

Unitary (visceral) and multiunit

Describe unitary smooth muscle.

Most common type; cells are connected by gap junctions, allowing them to contract as a single unit. Found in hollow organs and can be self-stimulating (autorhythmic).

Describe multiunit smooth muscle.

Cells act independently (no gap junctions), allowing precise control. Found in eye, large airways, and arteries.

How is smooth muscle control different from skeletal muscle control?

Smooth muscle is involuntary, controlled by the autonomic nervous system, hormones, and local signals, and does not require nervous stimulation to contract.

What is the nervous system?

A system that provides rapid, short-term control using electrical and chemical signals via neurons.

What are the main functions of the nervous system?

Receiving sensory input, integrating information, controlling muscles and glands, maintaining homeostasis, and enabling mental activity.

What is the difference between the nervous system and endocrine system?

The nervous system uses fast electrical signals for short-term control, while the endocrine system uses hormones for slower, long-term control.

What are the two anatomical divisions of the nervous system?

Central nervous system (CNS) and peripheral nervous system (PNS).

What structures make up the CNS?

The brain and spinal cord.

What structures make up the PNS?

Nerves, ganglia, sensory receptors, and plexuses.

What are cranial and spinal nerves?

Cranial nerves (12 pairs) connect to the brain; spinal nerves (31 pairs) connect to the spinal cord.

What is the sensory (afferent) division?

Carries signals from receptors to the CNS.

What is the motor (efferent) division?

Carries signals from the CNS to muscles and glands.

What is the difference between somatic and visceral sensory divisions?

Somatic = skin, muscles, joints; visceral = internal organs.

What are the two motor divisions?

Somatic motor (voluntary) and autonomic (involuntary).

What is a neuron?

An excitable cell that sends and receives signals via action potentials.

What are the three main parts of a neuron?

Cell body, dendrites, and axon.

What is the function of the cell body (soma)?

Metabolic center that produces proteins and maintains the neuron.

What are dendrites?

Branched processes that receive signals and carry them toward the cell body.