Nervous System & Adaptations to Training

What makes up the Central Nervous System (CNS)?

The brain and spinal cord.

What is the function of the CNS?

Processes information and sends information to cells.

What makes up the Peripheral Nervous System?

Nerves that carry messages between the CNS and the rest of the body.

What do sensory neurons do?

Send messages from tissues to the CNS for processing.

Where does the sensory neuron axon travel?

Up the dorsal root.

What are muscle spindles?

Proprioceptors coiled around muscle fibers.

What do muscle spindles detect?

Rapid changes in the length of muscle fibers.

What reflex do muscle spindles activate?

The stretch reflex.

What happens during the stretch reflex?

The CNS receives a signal and sends a motor message causing muscle contraction.

What are Golgi Tendon Organs (GTOs)?

Sensory receptors located at the musculotendinous junction.

What do GTOs detect?

Tension in the tendon.

What happens when GTOs detect excessive tension?

They stop signaling to the muscles and allow them to relax.

What do motor neurons do?

Send messages from the CNS to tissues.

Where is the motor neuron cell body located?

In the gray matter of the spinal cord.

Where does the motor neuron axon travel?

Down the ventral root.

What is the somatic nervous system?

Voluntary control of the musculoskeletal system.

What is the autonomic nervous system?

Involuntary control of cardiovascular, pulmonary, digestive, and endocrine systems.

What happens during a sympathetic response?

Increased HR, respiration, SV, cardiac output, BP, and metabolic activity.

What happens to digestion during a sympathetic response?

Digestive processes decrease.

What happens during a parasympathetic response?

Digestive activity increases while HR, respiration, and metabolic activity decrease.

What is the epineurium?

The outer covering of a peripheral nerve.

What is the perineurium?

The connective tissue surrounding nerve fascicles.

What is the endoneurium?

The inner connective tissue layer surrounding individual nerve fibers.

What are the three main parts of a neuron?

Cell body, dendrites, and axon.

What do dendrites do?

Receive messages from other neurons.

What does the axon do?

Sends messages to muscles, tissues, and glands.

What is the myelin sheath?

Fatty tissue that insulates the neuron.

What are Nodes of Ranvier?

Spaces between myelin sheaths containing voltage-gated channels.

What are axon terminals?

Endings that connect with muscle fibers, tissues, or glands.

What is a motor unit?

One motor neuron and all the muscle fibers it innervates.

What is a motor unit pool?

All motor units that innervate an individual muscle.

What is the all-or-nothing principle?

A stimulus either triggers an action potential or it does not.

What determines the force produced by a muscle?

The number of motor units recruited and the signals they receive.

What is the size principle?

Motor neurons are recruited from smallest to largest.

What happens as exercise intensity increases?

More muscle fibers are recruited, including higher-threshold fast-twitch fibers.

What is an action potential?

An electrochemical signal traveling down the axon to the axon terminals.

What happens during the resting state of a neuron?

The membrane potential is maintained at approximately -70 mV.

What does the Na/K ATPase pump do?

Pumps 3 sodium ions out and 2 potassium ions into the neuron.

At what voltage does depolarization begin?

Approximately -55 mV.

What happens during depolarization?

Sodium voltage-gated channels open and sodium enters the neuron.

What happens at approximately +30 mV?

Sodium channels close and potassium channels open.

What happens during repolarization?

Potassium leaves the neuron, making the charge more negative.

What is hyperpolarization?

When the membrane potential drops below its resting level.

How is resting potential restored after hyperpolarization?

The Na/K ATPase pump moves 3 Na out and 2 K in.

What is the neuromuscular junction (NMJ)?

The connection between a motor neuron and a muscle fiber.

What neurotransmitter is released at the NMJ?

Acetylcholine (ACh).

What happens after acetylcholine is released?

It crosses the synaptic cleft and binds to ACh receptors.

What carries the action potential into the muscle fiber?

The sarcolemma and T-tubules.

What does calcium do at the NMJ?

It is released from the sarcoplasmic reticulum to help initiate muscle contraction.

What are the main neural adaptations to resistance training?

Increased fast-twitch motor unit recruitment, firing frequency, and synchronization.

How does resistance training change the NMJ?

Increases surface area and ACh receptors, improving muscle fiber excitation.

How does resistance training affect the stretch reflex?

Increases muscle spindle activation and decreases GTO activation during concentric movement.