Peripheral nervous system: efferent division overview

Central nervous System (CNS)

Includes the brain and spinal cord

Peripheral nervous system (PNS)

Nerves outside the CNS, including cranial and spinal nerves

Efferent division

Transmits motor commands from CNS to effectors

somatic nervous system

Controls voluntary skeletal muscle movements

Autonomic nervous system

Regulates involuntary control of organs and muscles

Sympathetic nervous system

Prepares body for fight-or-flight response

Parasympathetic nervous system

Promotes “rest-and-digest” activities

Dual intervention

Single organ innervated by both sympathetic and parasympathetic

Adrenal medulla

Modified sympathetic part secreting catecholamines

Catecholamines

Hormones released by adrenal medulla during stress

Motor neurons

Transmit signals from CNS to skeletal muscles

Neuromuscular junction

Connection between motor neurons and muscle fibers

Acetylcholine (ACh)

Neurotransmitter at neuromuscular junction for muscle contraction

Terminal button

Enlarged end of axon terminal releasing neurotransmitters

Motor end plate

Muscle fiber region where ACh receptors are located

Action potential

Electrical signal triggering muscle contraction

Acetylcholinesterase

Enzyme that deactivates ACh at neuromuscular junction

Final common pathway

Motor neurons are the last step in signal transmission

Skeletal muscle fiber

Long, cylindrical cells responsible for muscle contraction

Voltage-gated channels

Open in response to changes in membrane potential

Calcium ions (Ca2+)

Trigger ACh release at the neuromuscular junction

Sodium ions (Na+)

Enter muscle cells, initiation action potentials

Potassium ions (K+)

Exit muscle cells, helping to depolarize membrane

Nonspecific cation channels

Allow Na+ and K+ movement during muscle activation

End-plate potential

Local depolarization at the motor end plate