Peripheral Nervous System
The Peripheral Nervous System
Overview
Connection to Central Nervous System
Attached to the brain and spinal cord.
Comprises 12 pairs of cranial nerves (linked to the brain).
Comprises 31 pairs of spinal nerves (linked to the spinal cord).
Functions
Supplies skeletal muscles directly.
Major Divisions
Sensory (afferent) division: Transmits sensory information to the brain.
Motor (efferent) division: Transmits motor commands from the brain to muscles.
Sensory Division
Functionality
Purpose: Transmits information from peripheral organs to the brain.
Major Families of Sensory Receptors
Mechanoreceptors: Detect physical forces (e.g., touch, pressure).
Thermoreceptors: Detect temperature changes.
Nociceptors: Detect painful stimuli.
Photoreceptors: Respond to light stimuli.
Chemoreceptors: Respond to chemical stimuli.
Special Families of Sensory Receptors
Joint Kinesthetic Receptors
Sensitive to joint angles and movement rates, helping sense joint position.
Muscle Spindles
Sensitive to muscle length and changes, allowing detection of muscle stretch.
Golgi Tendon Organs
Sensitive to tension in tendons, sensing muscle contraction strength.
Motor Division
Functionality
Purpose: Transmits information from the brain to peripheral muscles and glands.
Subdivisions
Autonomic Nervous System: Regulates involuntary functions.
Somatic Nervous System: Stimulates skeletal muscle activity.
Autonomic Nervous System
Overview
Function: Controls involuntary bodily functions such as heart rate and digestion.
Exercise-Related Autonomic Regulation: Modulates heart rate, blood pressure, and lung function.
Divisions of Autonomic Nervous System
Sympathetic Nervous System
Function: Prepares the body for fight or flight (exercise response).
Effects: Increases heart rate and blood pressure, blood flow to muscles, airway diameter (bronchodilation), metabolic rate, glucose, fatty acid levels, and alertness.
Parasympathetic Nervous System
Function: Active during rest (rest and digest response).
Effects: Increases digestion, promotes urination, conserves energy by decreasing heart rate and the diameter of blood vessels and airways.
Effects of Sympathetic and Parasympathetic Nervous Systems
Target Organ/System | Sympathetic Effects | Parasympathetic Effects |
|---|---|---|
Heart Muscle | Increases rate and force of contraction | Decreases rate of contraction |
Coronary Blood Vessels | Causes vasodilation | Causes vasoconstriction |
Lungs | Causes bronchodilation; mildly constricts blood vessels | Causes bronchoconstriction |
Blood Vessels | Increases blood pressure; causes vasoconstriction | Has little or no effect |
Liver | Stimulates glucose release | Has no effect |
Cellular Metabolism | Increases metabolic rate | Has no effect |
Adipose Tissue | Stimulates lipolysis | Has no effect |
Sweat Glands | Increases sweating | Has no effect |
Adrenal Glands | Stimulates secretion of epinephrine and norepinephrine | Has no effect |
Digestive System | Decreases activity of glands and muscles; constricts sphincters | Increases peristalsis and glandular secretion; relaxes sphincters |
Kidneys | Causes vasoconstriction; decreases urine formation | Has no effect |
Note: Lipolysis refers to breaking down triglycerides into basic energy units.