Anatomy Essentials: Prime Mover Muscles and Cranial Nerves

Prime Mover Muscles and Their Functions

• Iliopsoas: Prime mover of thigh flexion.
• Tibialis Anterior: Prime mover of dorsiflexion.
• Extensor Digitorum Longus: Prime mover of toe extension.
• Tibialis Posterior: Prime mover of foot inversion.
• Pectoralis Major: Primary arm flexor.
• Subscapularis: Prime medial rotator of the humerus.
• Serratus Anterior: Prime mover to protract and hold the scapula against the chest wall.
• Diaphragm: Prime mover of inspiration.
• Erector Spinae: Prime mover of back extension.
• Deltoid: Prime mover of arm abduction.
• Sternocleidomastoid: Prime mover of head flexion.
• Masseter: Prime mover of the jaw.
• Triceps Brachii: Prime forearm extensor.
• Extensor Digitorum Communis: Prime mover of finger extension.

Central Nervous System: The Hypothalamus

Vital Centers of the Hypothalamus

• ANS Control Center: Manages the Autonomic Nervous System.
• Emotional Response Center: Regulates emotional states.
• Body Temperature Regulation Center: Maintains thermal homeostasis.
• Food Intake Regulation Center: Controls hunger and satiety.
• Water/Thirst Regulation Center: Manages hydration levels.
• Sleep/Wake Cycle Regulation Center: Governs circadian rhythms.
• Endocrine System Regulation Control Centers: Oversees hormonal balance.

The 12 Cranial Nerves and Their Roles

• Olfactory (Sensory): Sensory filaments of smell run from the nasal mucosa to synapse with the olfactory bulb and tracts.
• Optic (Sensory): Develops as an outgrowth of the brain; carries afferent impulses for vision.
• Oculomotor (Motor): Eye mover; supplies four of the six extrinsic eye muscles and parasympathetic motor fibers to the sphincter.
• Trochlear (Motor): A pulley that innervates the extrinsic eye muscle that loops through a pulley-shaped ligament in the orbit.
• Trigeminal (Both): The largest of the cranial nerves; three branches spring from it to supply sensory fibers to the face and motor fibers to the chewing muscles.
• Abducens (Motor): Controls the extrinsic eye muscles that turn the eyeball laterally.
• Facial (Both): Controls muscles of facial expressions as well as the lacrimal, nasal, palatine, and salivary glands; conveys impulses from the taste buds via five branches.
• Vestibulocochlear (Sensory): Responsible for hearing and balance.
• Glossopharyngeal (Both): Contains some somatic motor fibers; carries impulses from receptors for the muscle that elevates the pharynx during swallowing and helps innervate salivary glands.
• Vagus (Both): Parasympathetic; carries sensory impulses from the thorax, abdominal viscera, and taste buds. This is the only cranial nerve to extend beyond the head and neck.
• Accessory (Motor): Innervates the pharynx, larynx, and soft palate, as well as some muscles that move the head and neck.
• Hypoglossal (Motor): Runs under the tongue and innervates the muscles that move the tongue.