Anatomy Lecture Test #3 Review Questions

What are the functions of skeletal muscle?

drive movement, maintain posture, stabilize joints, and regulate body temperature

What are the three connective tissue sheaths associated with skeletal muscle?

epimysium, perimysium, and endmysium

What is the difference between direct and indirect muscle attachments?

Direct muscle attachments occur when the muscle's outer tissue fuses almost imperceptibly with the bone's outer membrane, while indirect attachments use a distinct intermediate structure—like a tendon or aponeurosis—to bridge the gap between muscle and bone

Name the proteins a-d in the figure below. What is the function of each?

A: Troponin - binds to calcium ions

B: Actin - contains specific active binding sites where myosin heads attach

C: Tropomyosin - blocks the myosin binding sites on actin (when relaxed,

prevents contraction)

D: Myosin - acts as a molecular motor

Where is Ca2+ stored in a relaxed muscle fiber?

sarcoplasmic reticulum

What is a muscle triad and what is its function?

a specialized cellular structure in skeletal muscle fibers formed by a central transverse tubule (T-tubule) flanked by two terminal cisternae of the sarcoplasmic reticulum

Which of the following about the sliding filament model of contraction is true?

A. The I bands stay the same length

B. The A band shorten

C. The H zone disappears

D. The 2 Z discs of a sarcomere move closer together

E. The degree of overlap between thick and thin filaments increases

F. Thick and thin filaments become shorter

C, D, E

What are the two myofilaments? Which is thick and which is thin?

Myosin (thick), Actin (thin)

What is the role of troponin?

controls the calcium-mediated interaction between actin and myosin to regulate muscle contraction and relaxation

What happens to the Z discs during the sliding filament model of muscle contraction?

Z discs move closer together

What are the 2 requirements needed to establish a membrane potential?

an ion concentration gradient across the cell membrane and selective ionic permeability of the membrane

Why are resting membrane potentials negatively charged?

potassium ions (K+) leak out of the cell faster than other positive ions leak in

What types of ion channels are responsible for producing electrical signals?

gated and non gated ion channels

Explain how communication across the neuromuscular junction occurs?

a chemical and electrical process that allows a motor neuron to signal a skeletal muscle fiber to contract

What is excitation-contraction coupling?

the physiological process that converts an electrical stimulus (an action potential) into a mechanical response (muscle contraction

How does an action potential cause the terminal cisterns to release Ca2+ into the cytosol?

through a direct mechanical coupling process

How does a rise in cytosolic Ca2+ lead to the binding of myosin heads to actin?

through a regulatory chain reaction involving the troponin-tropomyosin complex

What are the 4 steps of the cross bridge cycle?

1. Cross Bridge Formation

2. The Power Stroke

3. Cross Bridge Detachment

4. Reactivation of the Myosin Head

How does the return of Ca2+ to the terminal cisterns cause a muscle to relax?

Ca²⁺ to detach from troponin, which shifts tropomyosin back to block the myosin-binding sites on actin

What causes rigor mortis to develop during death?

muscle cells run out of adenosine triphosphate (ATP)

What is a motor neuron?

a specialized nerve cell that transmits signals from the central nervous system (the brain and spinal cord) to muscles and glands to control both voluntary and involuntary actions

What is the size principle of motor unit recruitment?

motor units are recruited in a strict, orderly rank from smallest to largest based on the amount of force required by the muscle

What are the three sources of ATP used by muscle fibers to sustain a contraction?

immediate energy from creatine phosphate, rapid anaerobic energy from glycolysis, and long-term aerobic energy from cellular respiration

During the first 10-15 seconds of skeletal muscle contraction, what process provides the main source of ATP?

Creatine phosphate system

What process is the primary source of ATP used to sustain light to moderate activity for extended periods of time?

Oxidative phosphorylation

How does skeletal muscle fibers adapt to regular aerobic exercise?

causes deep structural and metabolic changes in skeletal muscles, particularly in slow-twitch (Type I) and Type IIa fibers, to boost endurance and delay fatigue

How do skeletal muscle fibers adapt to regular resistance exercise?

through structural enlargement, protein accumulation, and functional remodeling

How does the structure of a smooth muscle cell differ from a skeletal muscle fiber?

While skeletal muscle fibers are massive, multi-nucleated, and highly organized into striated, voluntary sarcomeres, smooth muscle cells are small, spindle-shaped, involuntary cells with a single central nucleus and a non-striated arrangement of contractile filaments

How does a rise in cytosolic Ca2+ trigger a smooth muscle contraction?

through a phosphorylation cascade

What factors are involved in regulating the contraction of smooth muscle cell?

electrical, chemical, mechanical, and intracellular enzymatic factors

What are some differences between unitary and multiunit smooth muscle?

Unitary (single-unit) smooth muscle cells are connected by gap junctions to contract together as a coordinated sheet, whereas multiunit smooth muscle cells lack gap junctions and are individually innervated to allow fine, independent control

What structures are found in the cell body of a neuron?

The cell body, dendrites, and an axon

What is the primary function of a dendrite, and an axon?

receive incoming signals, and transmit electrical impulses

What part of an axon generates electrical impulses and which part releases neurotransmitters?

axon hillock, and axon terminals

What is the myelin sheath and what is its main function?

insulating covering that wraps around the axon, main function is electrical insulation

What cells make the myelin sheath?

schwann cells (PNS), and oligodendrocytes (CNS)

What are the 3 functional classes of neurons and what are their functions?

Sensory (move towards the CNS), Motor (move away from the CNS), Interneurons (connectors, signaler)

What is voltage?

measure of potential energy generated by the separation of opposite charge between 2 points

What is electrical current?

the flow of electrical charge from one point to another

In a neuron, what structures function as insulators? What functions as conductors?

phospholipid bilayer, and myelin sheaths

ion channels, and ECF/ICF

What are the 3 kinds of gated ion channels?

Mechanically Gated, Chemically Gated, and Voltage Gated

What controls the gates of each kind of gated ion channel?

MG - physical force

CG - chemical binds

VG - change in membrane potential

What 2 factors are needed to establish a resting membrane potential and what is responsible for each factor?

Concentration gradients, and sodium potassium pumps

Which types of gated ion channels are responsible for generating graded potentials?

ligand-gated ion channels and mechanically gated ion channels

What are properties of graded potentials?

Vary in strength, either depolarized or hyperpolarized

Which type of gated ion channels are responsible for generating action potentials

Voltage gated ion channels

What is required to initiate the generation of an action potential and where is the action potential generated?

They must reach threshold, initial segment of the axon

Explain what happens during depolarization phase of the action potential

Na+ channel open, sodium flowing down

What happens at the end of the depolarization phase and initial repolarization phase?

Ball and chain Na+ closes, K+ opens, potassium flows up

What happens during the hyperpolarization phase?

some K+ do not close, which causes to much potassium

What are the 3 ways the neurotransmitters can be removed from the synaptic cleft?

diffusion, enzymatic degradation, and reuptake

Which ions are involved in generating an EPSP? IPSP?

Na, Ca, and Cl, K

What is the function of an EPSP? IPSP?

allows Na to flow into the cell (depolarization), and allows Cl or K to flow out of the cell (hyperpolarization)

Where does synaptic integration occur?

the axon hillock

What is the first step in chemical synapse?

Action potential arrives at presynpatic axon terminal

What is the second step in chemical synapse?

Voltage gated Ca chennels open allowing Ca to enter axon terminal

What is the third step in chemical synapse?

Ca entry causes synaptic vesicles to release neurotransmitters by exocytosis

What is the fourth step in chemical synapse?

Neurotransmitters diffuse across the synaptic cleft and binds to neurotransmitter receptors found on the posysynaptic receptive surface

What is the fifth step in chemical synapse?

Binding of neurotransmitters open ion channels, resulting in graded potentials

What is the sixth step in chemical synapse?

Neurotransmitter effects are terminated by reuptake, enzymatic degradation, or diffusion away from synaptic cleft

Which neurotransmitter is deficient in Alzheimer’s disease? Parkinson’s disease?

Acetylcholine, and Dopamine

How do SSRIs enhance the effects of serotonin?

blocking its reabsorption into nerve cells (blocking reuptake)

What is the main excitatory neurotransmitter in the CNS?

Glutamate

The effects of which neurotransmitter is enhanced by benzodiazepines?

GABA

Which neurotransmitters have pain-relieving properties?

Substance P, and Endorphins

What are the four major regions of the brain?

Diencephalon, Cerebrum, Brain Stem, and Cerebellum

What is found in gray matter? White matter?

Cell Bodies/Dendrites, and Myelinated Axons

What are some functions of the cerebral cortex?

Memory and Learning, Speaking, Decision Making, and Forming Memories

Which cerebrum white matter fibers communicate with lower regions of the brain and spinal cord?

Projection Fibers

What are the functions of the thalamus?

Gateway to cerebral cortex

What are the functions of the hypothalamus?

Regulated body temp, initiates physical responses to emotional states, and regulates autonomic nervous system

What are the functions of the cerebellum?

Acts like an autopilot, and plays a role in motor

What are the functions of the brainstem?

Innervate the face muscles, and works with hypothalamus to regulate homeostasis

What is found in the dorsal, ventral, and lateral horns of the spinal cord?

Gray Matter

What structure carries sensory input into the spinal cord?

Dorsal Root

What structure carries motor output from the spinal cord?

What are 2 functions of the spinal cord?