Exam 4 IUN P261- Learning Objectives

What are the physiological properties common to all muscle types?

All muscle types exhibit excitability, contractility, extensibility, and elasticity.

What are the defining characteristics of skeletal muscle?

Skeletal muscle is striated, voluntary, multinucleated, and attached to bones.

What are the structural components of a muscle fiber?

Muscle fibers consist of myofibrils, sarcoplasm, sarcolemma, and connective tissue.

How do the striations of a muscle fiber relate to its protein filaments?

Striations are due to the alternating arrangement of thick (myosin) and thin (actin) filaments.

What are the major proteins of a muscle fiber and their functions?

Major proteins include actin (thin filament), myosin (thick filament), and troponin/tropomyosin (regulatory proteins).

What is a motor unit and its role in muscle contraction?

A motor unit consists of a motor neuron and the muscle fibers it innervates, coordinating muscle contraction.

What are the structural features of the neuromuscular junction?

The neuromuscular junction includes the presynaptic terminal, synaptic cleft, and postsynaptic membrane (motor end plate).

Why does a cell have an electrical charge difference across its plasma membrane?

The charge difference, or membrane potential, is due to the distribution of ions, crucial for muscle contraction.

How does a nerve fiber stimulate a skeletal muscle fiber?

A nerve fiber releases acetylcholine at the neuromuscular junction, triggering an action potential in the muscle fiber.

How does stimulation of a muscle fiber activate its contractile mechanism?

Stimulation causes calcium ions to be released, enabling cross-bridge formation between actin and myosin.

What is the mechanism of muscle contraction?

Muscle contraction occurs through the sliding filament theory, where actin filaments slide over myosin filaments.

How does a muscle fiber relax?

Muscle fiber relaxation occurs when calcium ions are reabsorbed, and cross-bridges between actin and myosin are broken.

Why does the force of a muscle contraction depend on the muscle's length prior to stimulation?

The length-tension relationship indicates that optimal overlap of actin and myosin maximizes force production.

What are the stages of a muscle twitch?

The stages of a muscle twitch include the latent period, contraction phase, and relaxation phase.

How can successive muscle twitches produce stronger contractions?

Successive twitches can lead to summation, where the force of contraction increases due to rapid stimulation.

What is the difference between isometric and isotonic contraction?

Isometric contraction occurs without muscle length change, while isotonic contraction involves muscle shortening or lengthening.

What is the difference between concentric and eccentric contraction?

Concentric contraction shortens the muscle, while eccentric contraction lengthens the muscle under tension.

How does skeletal muscle meet its energy demands during rest and exercise?

During rest, skeletal muscle primarily uses fatty acids; during exercise, it shifts to glucose and creatine phosphate.

What is the basis of muscle fatigue and soreness?

Muscle fatigue results from depletion of energy sources and accumulation of lactic acid; soreness is due to microtears in muscle fibers.

Why is extra oxygen needed even after exercise has ended?

Extra oxygen is required to restore ATP levels, clear lactic acid, and replenish oxygen stores in myoglobin.

What are the two physiological types of muscle fibers?

The two types are slow-twitch (Type I) fibers, which are endurance-oriented, and fast-twitch (Type II) fibers, which are power-oriented.

What factors affect muscular strength?

Factors include muscle size, fiber type distribution, neural activation, and training status.

What are the effects of resistance and endurance exercises on muscles?

Resistance training increases muscle size and strength, while endurance training enhances aerobic capacity and muscle endurance.

What are the structural and physiological differences between cardiac muscle and skeletal muscle?

Cardiac muscle is striated, involuntary, and has intercalated discs; skeletal muscle is striated, voluntary, and multinucleated.

Why are the differences between cardiac and skeletal muscle important to cardiac function?

These differences allow cardiac muscle to contract rhythmically and continuously, essential for effective heart function.

What are the structural and physiological differences between smooth muscle and skeletal muscle?

Smooth muscle is non-striated, involuntary, and has a single nucleus; skeletal muscle is striated, voluntary, and multinucleated.

What is the overall function of the nervous system?

The overall function of the nervous system is to coordinate and control bodily functions by transmitting signals between different parts of the body.

What are the major anatomical subdivisions of the nervous system?

The major anatomical subdivisions of the nervous system are the central nervous system (CNS), which includes the brain and spinal cord, and the peripheral nervous system (PNS), which includes all the nerves outside the CNS.

What are the three functional properties found in all neurons?

The three functional properties found in all neurons are excitability (the ability to respond to stimuli), conductivity (the ability to transmit electrical impulses), and secretion (the ability to release neurotransmitters).

What are the three basic functional categories of neurons?

The three basic functional categories of neurons are sensory neurons (which carry signals to the CNS), motor neurons (which carry signals away from the CNS to muscles and glands), and interneurons (which connect neurons within the CNS).

What are the parts of a neuron?

The parts of a neuron include the cell body (soma), dendrites (which receive signals), and axon (which transmits signals away from the cell body).

How do neurons transport materials between the cell body and tips of the axon?

Neurons transport materials between the cell body and tips of the axon through a process called axonal transport, which involves motor proteins that move along the neuron's cytoskeleton.

What are the six types of cells that aid neurons, and what are their functions?

The six types of glial cells that aid neurons are astrocytes (support and nutrient supply), oligodendrocytes (myelin sheath formation in the CNS), Schwann cells (myelin sheath formation in the PNS), microglia (immune defense), ependymal cells (cerebrospinal fluid production), and satellite cells (support for neuron cell bodies in ganglia).

What are the features of the myelin sheath and its importance?

The myelin sheath is a fatty layer that surrounds the axon of some neurons, which increases the speed of electrical signal transmission and provides insulation to prevent signal loss.

Why does a cell have an electrical charge difference (voltage) across its membrane?

A cell has an electrical charge difference across its membrane due to the unequal distribution of ions (such as sodium and potassium) inside and outside the cell, creating a resting membrane potential.

How does stimulation of a neuron cause a local electrical response in its membrane?

Stimulation of a neuron causes a local electrical response in its membrane by opening ion channels, leading to a change in membrane potential, which can initiate an action potential if the threshold is reached.

How do local responses generate a nerve signal?

Local responses generate a nerve signal by depolarizing the membrane, which can trigger an action potential that propagates along the axon.

How is the nerve signal conducted down an axon?

The nerve signal is conducted down an axon through the propagation of action potentials, which involve the sequential opening and closing of voltage-gated ion channels along the axonal membrane.

How are messages transmitted from one neuron to another?

Messages are transmitted from one neuron to another through synapses, where neurotransmitters are released from the presynaptic neuron and bind to receptors on the postsynaptic neuron.

What are examples of neurotransmitters and neuromodulators, and what are their actions?

Examples of neurotransmitters include acetylcholine (which stimulates muscle contraction), dopamine (which is involved in reward and pleasure), and serotonin (which regulates mood). Neuromodulators can alter the strength of synaptic transmission and include substances like endorphins.

How is stimulation of a postsynaptic cell stopped?

Stimulation of a postsynaptic cell is stopped by the reuptake of neurotransmitters back into the presynaptic neuron, enzymatic degradation of neurotransmitters, or diffusion away from the synaptic cleft.

How does a neuron decide to generate action potentials?

A neuron generates action potentials based on the summation of excitatory and inhibitory signals it receives. If the net signal exceeds a certain threshold, an action potential is triggered.

How does the nervous system translate complex information into a simple code?

The nervous system translates complex information into a simple code through the use of action potentials and neurotransmitters, which encode information in terms of frequency and pattern of neuronal firing.

How do neurons work together in groups to process information?

Neurons work together in groups, forming networks that allow for the integration of signals and processing of information, leading to coordinated responses and effective output.