Anatomy and Physiology: Chapter 9B (Muscular System) and Chapter 11 (Nervous System)

Comprehensive review flashcards covering Chapter 9B (Muscle Contraction, Energy Pathways, and Fiber Types) and Chapter 11 (Nervous System Fundamentals, Neurophysiology, Synaptic Transmission, and Circuits).

Muscle Contraction (Cells vs. Tissue)

An individual muscle cell contracts entirely or not at all, whole muscle tissue can be partially contracted since the cells are the part and the tissue is the whole.

Motor Unit

A motor unit is defined as one motor neuron and all the muscle fibers it innervates (or controls)

Recruitment

Recruitment: summating, or adding, motor units together (used to lift heavy objects)

Hypertrophy vs. Hyperplasia

Hypertrophy: is an increase in the size of existing muscle cells,

Hyperplasia: is an increase in the total number of muscle cells.

Isometric Contraction

Muscle tension increases, but muscle length does not change and no joint movement occurs. (The impossible object.)

Isotonic Contraction

Muscle tension is constant while the length of the muscle changes (Able to lift the object).

DOMS

Delayed Onset Muscle Soreness; muscle pain, stiffness, and tenderness that typically peaks $24$ to $72\,\text{hours}$ following unaccustomed or strenuous exercise. (Soreness after lift)

Muscle Tone

A state of partial, continuous, and involuntary contraction of skeletal muscles that stabilizes joints and maintains posture.

Sources of ATP and Their Order of Usage

First, pre-existing stored ATP

Second, creatine phosphate

Third, anaerobic glycolysis

Fourth, aerobic respiration

Aerobic vs. Anaerobic Respiration

Aerobic respiration requires oxygen to produce a high amount of ATP inside mitochondria,

Anaerobic respiration produces ATP rapidly without oxygen through glycolysis, making lactic acid.

Exercise Intensity and Fuels

Low intensity exercise uses fatty acids as fuel through aerobic respiration,

High intensity exercise uses glucose through anaerobic and aerobic glycolysis.

EPOC

Excess Post-Exercise Oxygen Consumption: the amount of oxygen required to restore the body to its normal, resting metabolic state after exercise. It reflects the recovery processes including restoring ATP and phosphocreatine levels, clearing lactate, and reoxygenating hemoglobin.

Velocity of Muscle Contraction

The speed of muscle shortening, which is inversely related to the load placed on the muscle and directly influenced by the predominant muscle fiber type and motor unit recruitment.

Slow Oxidative Muscle Fibers

Fatigue-resistant muscle fibers with high myoglobin and capillary content that contract slowly and depend primarily on aerobic respiration for endurance activities.

Fast Glycolytic Muscle Fibers

Fatigable muscle fibers with large glycogen stores and low myoglobin content that contract rapidly and powerfully via anaerobic glycolysis for short bursts of speed or power.

Neurons vs. Supporting Cells

Neurons are electrically excitable cells that generate and transmit nerve impulses, while supporting cells (neuroglia) protect, insulate, nourish, and support neuronal function.

Structural Classification of Neurons

The categorization of neurons based on the number of processes extending from the soma: multipolar (many dendrites, one axon), bipolar (one dendrite, one axon), and unipolar/pseudounipolar (single process dividing into two branches).

Functional Classification of Neurons

The categorization of neurons based on impulse direction: sensory (afferent) neurons carrying signals toward the CNS, motor (efferent) neurons carrying signals away from the CNS, and interneurons connecting neurons within the CNS.

Dendrites

Branch-like parts of a neuron that receive messages from other neurons and carry them toward the cell body.

Axon

A long, specialized neuronal process that conducts action potentials away from the cell body toward target cells or synaptic terminals.

Production of Myelin in CNS and PNS

In the central nervous system (CNS), myelin is produced by oligodendrocytes wrapping around multiple axons; in the peripheral nervous system (PNS), myelin is produced by Schwann cells wrapping around a single axon segment.

Leakage Ion Channels

Nongated channels that remain permanently open, allowing specific ions to passively diffuse across the plasma membrane down their electrochemical gradient.

Chemically Gated Ion Channels

gated channels that open or close in response to the specific binding of a chemical messenger, such as a neurotransmitter.

Voltage-Gated Ion Channels

Ion channels that open or close in direct response to changes in membrane potential.

Resting Membrane Potential

The electrical voltage difference across the plasma membrane of an unstimulated, resting neuron, typically around $-70\,\text{mV}$.

Threshold

The critical membrane potential (typically around $-55\,\text{mV}$) that must be reached to trigger the opening of voltage-gated channels and generate an action potential.

Depolarization

A change in membrane potential that makes the inside of the cell less negative (more positive) relative to the resting membrane potential.

Repolarization

The restoration of the negative membrane potential back toward resting levels following depolarization, mainly due to the efflux of potassium ions ($K^+$).

Hyperpolarization

A change in membrane potential that makes the inside of the cell more negative than the standard resting potential, decreasing neuronal excitability.

Synaptic Potential

A graded, local change in the membrane potential of the postsynaptic membrane produced by the binding of neurotransmitters to receptor channels.

Electrical-Chemical-Electrical Transmission

The sequence of neural signaling where an electrical action potential travels down the axon, is converted into chemical neurotransmitter release across the synapse, and triggers a new electrical graded potential in the postsynaptic cell.

EPSPs

Excitatory Postsynaptic Potentials; local graded depolarizations of the postsynaptic membrane that bring the membrane potential closer to threshold.

IPSPs

Inhibitory Postsynaptic Potentials; local graded hyperpolarizations of the postsynaptic membrane that drive the membrane potential farther below threshold.

Refractory Periods

The absolute refractory period is the interval when a second action potential cannot be initiated regardless of stimulus strength; the relative refractory period is when an action potential can be triggered only by an unusually strong stimulus.

Action Potential Velocity

The speed at which an action potential propagates along an axon, primarily determined by axon diameter (larger is faster) and the presence of a myelin sheath (saltatory conduction).

Chemical Synapse

A specialized functional junction between a presynaptic neuron and a postsynaptic cell where communication occurs via the release and reception of chemical neurotransmitters across a synaptic cleft.

Removal of Neurotransmitters

The termination of neurotransmitter effects accomplished by enzymatic degradation, cellular reuptake by presynaptic terminals or glial cells, or simple diffusion away from the synaptic cleft.

3 Criteria to be a Neurotransmitter

The chemical must be synthesized and stored in the presynaptic neuron, released in response to presynaptic depolarization, and produce a specific biological response by binding to receptors on the postsynaptic target.

Dopamine

A biogenic amine (catecholamine) neurotransmitter involved in motor control, motivation, reward pathways, and emotional regulation.

NO

Nitric Oxide; an atypical gaseous neurotransmitter (gasotransmitter) that freely diffuses across membranes to activate intracellular target enzymes rather than binding membrane receptors.

Ach

Acetylcholine; a major neurotransmitter released by motor neurons at the neuromuscular junction and found throughout the central and peripheral nervous systems.

G-Protein Receptors

Metabotropic transmembrane receptors that activate intracellular G-proteins and secondary messenger cascades when a neurotransmitter binds to them.

Summation (Temporal and Spatial)

• Temporal summation: One neuron sends signals repeatedly and quickly, causing the signals to build up.

• Spatial summation: Multiple neurons send signals at the same time, combining their effects on one neuron

Diverging vs. Converging Circuits

• Diverging circuit: One neuron sends signals to many other neurons.

• Converging circuit: Many neurons send signals to one neuron.