chapter 4

What are the two major divisions of the nervous system?

Central nervous system (CNS) and peripheral nervous system (PNS).

What structures make up the CNS?

Brain and spinal cord.

What structures make up the PNS?

All nerves outside the brain and spinal cord.

What is the primary function of the CNS?

Process information and coordinate responses.

What is the primary function of the PNS?

Transmit information to and from the CNS.

What are afferent pathways?

Sensory pathways carrying information to the CNS.

What are efferent pathways?

Motor pathways carrying commands from the CNS.

Afferent means what?

Sensory input to the CNS.

Efferent means what?

Motor output from the CNS.

What is membrane potential?

The electrical charge difference across a cell membrane.

What is resting membrane potential?

The membrane potential of a neuron at rest.

What is depolarization?

The membrane becomes less negative and more positive.

What is repolarization?

The membrane returns toward resting membrane potential.

What is hyperpolarization?

The membrane becomes more negative than resting potential.

What is an action potential?

A rapid electrical signal that travels along a neuron.

What causes an action potential?

The membrane reaching threshold.

What is threshold?

The membrane potential required to trigger an action potential.

What is a synapse?

The junction between two neurons or a neuron and muscle fiber.

What is a neurotransmitter?

A chemical messenger released at a synapse.

What is the synaptic cleft?

The space between communicating cells.

What is a presynaptic neuron?

The neuron releasing neurotransmitter.

What is a postsynaptic neuron?

The neuron receiving neurotransmitter.

What is an EPSP?

Excitatory postsynaptic potential.

What does an EPSP do?

Makes a neuron more likely to fire.

What ion movement commonly causes EPSPs?

Na⁺ entry.

What does depolarization do to action potential likelihood?

Increases it.

What is an IPSP?

Inhibitory postsynaptic potential.

What does an IPSP do?

Makes a neuron less likely to fire.

What does hyperpolarization do to action potential likelihood?

Decreases it.

What is temporal summation?

Repeated stimulation from one neuron over time.

What is spatial summation?

Simultaneous stimulation from multiple neurons.

What neurotransmitter is released at the neuromuscular junction?

Acetylcholine (ACh).

What enzyme breaks down acetylcholine?

Acetylcholinesterase.

Why is acetylcholinesterase important?

It prevents continuous stimulation.

What is the somatic nervous system?

The division controlling voluntary movement.

What neurons control skeletal muscle?

Alpha motor neurons.

What is a motor unit?

One alpha motor neuron and all muscle fibers it innervates.

What is innervation ratio?

The number of muscle fibers controlled by one motor neuron.

What does a low innervation ratio allow?

Fine motor control.

What does a high innervation ratio allow?

Greater force production.

What is the size principle?

Motor units are recruited from small to large.

Which motor units are recruited first?

Small motor units.

Which motor units are recruited last?

Large motor units.

Why are small motor units recruited first?

They require less stimulation.

What is the exception to the size principle?

Explosive movements may recruit large motor units earlier.

What is the autonomic nervous system?

The division controlling involuntary functions.

What are the two divisions of the autonomic nervous system?

Sympathetic and parasympathetic.

What is the sympathetic nervous system?

The fight-or-flight division.

What is the parasympathetic nervous system?

The rest-and-digest division.

What spinal regions are associated with the sympathetic nervous system?

T1–L2.

What spinal regions are associated with the parasympathetic nervous system?

Brainstem and S2–S4.

What neurotransmitter is released by sympathetic preganglionic neurons?

Acetylcholine.

What neurotransmitter is typically released by sympathetic postganglionic neurons?

Norepinephrine.

What neurotransmitter is released by parasympathetic preganglionic neurons?

Acetylcholine.

What neurotransmitter is released by parasympathetic postganglionic neurons?

Acetylcholine.

What is the fight-or-flight response?

The body's response to stress requiring rapid action.

What is the rest-and-digest response?

The body's recovery and maintenance state.

What is the primary motor cortex responsible for?

Voluntary movement.

Where is the primary motor cortex located?

Cerebral cortex.

What is the cerebellum responsible for?

Coordination, balance, and motor learning.

What role does the cerebellum play in movement?

Fine-tuning movements.

What is the brainstem responsible for?

Reflexes, posture, equilibrium, and autonomic control.

What role does the brainstem play in exercise?

Controls vital autonomic functions.

What is the central governor theory?

The theory that the brain regulates exercise performance to protect homeostasis.

According to central governor theory, where does fatigue originate?

Partly in the brain.

Why does the brain limit exercise performance?

To prevent catastrophic physiological failure.

What are proprioceptors?

Sensory receptors that provide information about body position and movement.

Where are proprioceptors found?

Muscles, tendons, and joints.

What is a muscle spindle?

A proprioceptor that detects muscle stretch.

What does a muscle spindle measure?

Muscle length and rate of stretch.

What reflex is associated with the muscle spindle?

Stretch reflex.

What is an example of the stretch reflex?

The knee-jerk reflex.

What happens during a stretch reflex?

A stretched muscle contracts.

What is a Golgi tendon organ (GTO)?

A proprioceptor that detects muscle tension.

Where is the GTO located