Exercise Physiology: The Nervous System - Structure and Control of Movement

Vocabulary flashcards covering key terms and concepts from Chapter 7 on the structure, function, and motor control mechanisms of the nervous system.

Central Nervous System (CNS)

The division of the nervous system consisting of the brain and spinal cord, responsible for actively helping control the internal environment, integrating reflexes, and storing experiences for memory and learning.

Peripheral Nervous System (PNS)

The portion of the nervous system located outside the central nervous system, divided into a sensory (afferent) division and a motor (efferent) division.

Afferent Fibers

Sensory nerve fibers in the peripheral nervous system that transmit electrical impulses inward from sensory receptors to the central nervous system.

Efferent Fibers

Motor nerve fibers in the peripheral nervous system that transmit electrical impulses outward from the central nervous system to effector organs.

Dendrites

Branch-like extensions of a neuron cell body that conduct incoming nerve impulses toward the cell body.

Axon

The long, single process of a neuron that carries electrical impulses away from the cell body toward target cells or synapses.

Schwann Cells

Supporting cells in the peripheral nervous system that wrap around motor neuron axons to form a discontinuous myelin sheath.

Synapse

The specialized junction or contact point between the axon terminal of one neuron and the dendrite or cell body of another neuron.

Multiple Sclerosis (MS)

A neurological disease characterized by progressive destruction of axon myelin sheaths in the central nervous system due to an autoimmune attack, leading to progressive loss of functional capacity.

Irritability

The functional property of a neuron or excitable cell that allows it to respond to a stimulus and convert it into a neural impulse.

Conductivity

The functional property of a neuron that allows it to transmit a nerve impulse along the entire length of its axon.

Resting Membrane Potential

The negative electrical charge maintained inside a neuron relative to the outside at rest, typically ranging from $-40\text{ mV}$ to $-75\text{ mV}$.

Sodium-Potassium Pump ($Na^+/K^+$ Pump)

An active membrane transport pump that maintains resting potential by moving $2\text{ K}^+$ into the cell for every $3\text{ Na}^+$ pumped out, using energy from ATP.

Action Potential

An all-or-none nerve impulse produced when a threshold stimulus depolarizes the neuron membrane, rapidly opening voltage-gated sodium channels.

Depolarization

The initial phase of an action potential where voltage-gated $Na^+$ channels open, allowing $Na^+$ to diffuse into the cell and shift membrane potential from negative to positive ($+30\text{ mV}$).

Repolarization

The rapid restoration of a neuron's negative resting membrane potential following depolarization, driven by the closing of $Na^+$ channels and the opening of $K^+$ channels allowing $K^+$ to exit the cell.

All-or-None Law

The principle stating that once a nerve impulse is initiated, it will propagate down the entire length of the neuron without losing intensity.

Neurotransmitter

A chemical messenger released from presynaptic vesicles across the synaptic cleft that binds to specific receptors on the postsynaptic membrane.

Excitatory Postsynaptic Potential (EPSP)

A temporary localized depolarization of the postsynaptic membrane caused by neurotransmitter binding, bringing the neuron closer to firing threshold.

Temporal Summation

The accumulation of multiple excitatory postsynaptic potentials (EPSPs) delivered in rapid succession from a single presynaptic neuron.

Spatial Summation

The simultaneous sum of excitatory postsynaptic potentials (EPSPs) originating from several different presynaptic neurons onto a single postsynaptic neuron.

Inhibitory Postsynaptic Potential (IPSP)

A hyperpolarization of the postsynaptic membrane caused by inhibitory neurotransmitters, making the resting membrane potential more negative and resistant to depolarization.

Kinesthesia

The conscious perception of body part positions and joint movements, including the rate and speed of limb movement.

Pacinian Corpuscles

Joint proprioceptors situated in tissues surrounding joints that detect the rate of joint rotation.

Muscle Spindle

A muscle proprioceptor situated parallel to extrafusal fibers that detects changes in muscle length and rate of shortening.

Gamma Motor Neurons

Motor neurons that innervate intrafusal muscle fibers, causing them to contract in concert with extrafusal muscle fibers to maintain muscle spindle sensitivity.

Stretch Reflex

A protective reflex contraction of a muscle in response to rapid lengthening detected by muscle spindles, such as the knee-jerk reflex.

Golgi Tendon Organ (GTO)

A muscle proprioceptor located in series within tendon fibers that monitors force development and induces reflex muscle relaxation when excessive tension is generated.

Muscle Chemoreceptors

Free nerve endings in skeletal muscle sensitive to chemical changes ($H^+$ ions, $CO_2$, and $K^+$) that provide information to the CNS regarding muscle metabolic activity.

Motor Unit

A individual motor neuron and all of the specific muscle fibers it innervates.

Innervation Ratio

The number of muscle fibers innervated per motor neuron, which is low in muscles performing fine motor control and high in large limb muscles.

Henneman Size Principle

The concept that motor units are recruited in an orderly fashion during exercise based on size, starting with the smallest motor neurons (Type S) and progressing to larger ones.

Type S Motor Units

Small motor units containing slow, highly oxidative Type I muscle fibers that have the lowest recruitment threshold.

Type FR Motor Units

Intermediate motor units containing fast, fatigue-resistant Type IIa muscle fibers.

Type FF Motor Units

The largest motor units containing fast, fatigable Type IIx muscle fibers that produce maximum force output.

Vestibular Apparatus

An organ located in the inner ear responsible for maintaining general equilibrium, head position, and balance during static and dynamic conditions.

Central Governor Theory

A hypothesis stating that exercise-induced fatigue is regulated by a central control center in the brain that limits motor output to protect the body against catastrophic homeostatic failure.

Central Fatigue

Fatigue resulting from neuronal dysfunction or neurotransmitter depletion within higher brain centers or motor neurons, reducing central drive to working muscles.

Concussion

A complex traumatic brain injury resulting from direct or indirect physical force to the head, neck, or body, leading to transient impairment of neural function.

Second-Impact Syndrome

A life-threatening complication occurring when an athlete receives a second head injury before recovering from an initial concussion, causing rapid vascular congestion and severe brain swelling.

Chronic Traumatic Encephalopathy (CTE)

A progressive neurodegenerative disorder associated with repeated traumatic brain injuries, pathologically characterized by neuronal death, loss of axons, and brain inflammation.

Spinal Tuning

The process by which neural networks within the spinal cord refine motor commands received from higher brain centers prior to muscle execution.

Withdrawal Reflex

A spinal reflex mechanism designed to automatically retract a limb away from a noxious or painful stimulus via ipsilateral flexor muscle activation.

Crossed Extensor Reflex

A reflex arc accompanying the withdrawal reflex where collateral interneurons stimulate contralateral extensor motor neurons to support body weight.

Sympathetic Division

The autonomic division that prepares the body for action by releasing norepinephrine (NE), which binds to alpha or beta receptors on target effectors.

Parasympathetic Division

The autonomic division dominant during rest that releases acetylcholine (ACh) to regulate visceral effector organs.

Brain-Derived Neurotrophic Factor (BDNF)

A key brain growth factor increased by regular physical exercise that supports neurogenesis, synaptic plasticity, and cognitive function.