Lab Exam 2 Review: Muscles, Nervous System, and Brain Anatomy

Muscles of the Head, Trunk, Arm, and Leg

Head and Trunk Muscles

The muscles of the head and trunk are essential for facial expression, mastication, neck movement, and core stability. Understanding their names, locations, and functions is crucial for anatomy students.

• Orbicularis oculi: Closes the eyelids; important for blinking and winking.

• Orbicularis oris: Encircles the mouth; allows for puckering and closing lips.

• Epicranius (frontalis/occipitalis): Raises eyebrows and moves scalp.

• Buccinator: Compresses cheek; aids in chewing and blowing.

• Zygomaticus: Elevates corners of mouth (smiling).

• Masseter: Elevates mandible; primary muscle of mastication.

• Temporalis: Elevates and retracts mandible.

• Sternocleidomastoid (SCM): Flexes neck; rotates head to opposite side.

• Trapezius: Elevates, retracts, and rotates scapula; extends neck.

• Pectoralis major: Flexes, adducts, and medially rotates arm.

• Rectus abdominis: Flexes vertebral column; compresses abdomen.

• External/Internal oblique: Rotate and laterally flex trunk; compress abdomen.

• Transversus abdominis: Compresses abdominal contents.

• Serratus anterior: Protracts scapula; assists in upward rotation.

• Latissimus dorsi: Extends, adducts, and medially rotates arm.

• Levator scapulae: Elevates scapula.

• Rhomboids: Retract scapula.

Arm and Leg Muscles

These muscles are responsible for movement and stabilization of the limbs. They are grouped by their anatomical location and function.

• Biceps brachii: Flexes elbow and supinates forearm.

• Brachialis: Primary flexor of the elbow.

• Brachioradialis: Flexes forearm at elbow.

• Triceps brachii: Extends elbow.

• Deltoid: Abducts arm; assists in flexion and extension.

• Flexor/extensor carpi group: Flex and extend the wrist.

• Flexor/extensor digitorum group: Flex and extend the fingers.

• Thenar group: Controls thumb movements.

• Hypothenar group: Controls little finger movements.

• Quadriceps group (Rectus femoris, Vastus lateralis, Vastus medialis, Vastus intermedius): Extends knee.

• Hamstrings group (Biceps femoris, Semitendinosus, Semimembranosus): Flexes knee and extends hip.

• Gluteus maximus: Extends and laterally rotates hip.

• Gluteus medius: Abducts and medially rotates hip.

• Tensor fascia lata (TFL): Abducts and stabilizes hip.

• Adductor group: Adducts thigh.

• Gastrocnemius: Plantar flexes foot; flexes knee.

• Soleus: Plantar flexes foot.

• Tibialis anterior: Dorsiflexes and inverts foot.

• Fibularis (peroneus) group: Everts and plantar flexes foot.

Nervous System Anatomy

Neuron Structure

Neurons are the functional units of the nervous system, responsible for transmitting electrical and chemical signals.

• Neuron: A nerve cell consisting of a cell body, dendrites, and an axon.

• Axon: Conducts impulses away from the cell body.

• Dendrite: Receives incoming signals.

• Myelin sheath: Insulating layer around axons; increases speed of impulse conduction.

• Node of Ranvier: Gaps in myelin sheath; facilitate rapid conduction (saltatory conduction).

• Axon terminal: Releases neurotransmitters to communicate with other cells.

Brain Anatomy

The brain is divided into several regions, each with specialized functions. Understanding the major structures is essential for studying the central nervous system.

• Cerebrum: Largest part; responsible for higher brain functions (thought, memory, voluntary movement).

• Cerebellum: Coordinates voluntary movements and balance.

• Diencephalon: Contains thalamus and hypothalamus; relays sensory information and regulates autonomic functions.

• Brainstem: Includes midbrain, pons, and medulla oblongata; controls vital functions (breathing, heart rate).

• Gyri and sulci: Ridges (gyri) and grooves (sulci) increase surface area of the cortex.

• Precentral/postcentral gyrus: Primary motor and sensory areas, respectively.

• Longitudinal fissure: Divides left and right cerebral hemispheres.

• Arbor vitae: Tree-like white matter in cerebellum.

• Lateral ventricles: Cavities containing cerebrospinal fluid (CSF).

Spinal Cord Anatomy

The spinal cord transmits neural signals between the brain and the body and is protected by meninges and vertebrae.

• Pia mater, dura mater, arachnoid mater: Three protective membranes (meninges) surrounding the spinal cord.

• Spinal nerve: Mixed nerve carrying motor, sensory, and autonomic signals.

• Ventral root: Contains motor neuron axons.

• Dorsal root: Contains sensory neuron axons.

• Dorsal root ganglion (DRG): Contains cell bodies of sensory neurons.

• Central canal: Contains cerebrospinal fluid.

Cranial Nerves I-XII

Cranial nerves are twelve pairs of nerves that emerge directly from the brain, each with specific sensory, motor, or mixed functions.

Number	Name	Function
I	Olfactory	Sensory (smell)
II	Optic	Sensory (vision)
III	Oculomotor	Motor (eye movement, pupil constriction)
IV	Trochlear	Motor (eye movement)
V	Trigeminal	Mixed (facial sensation, chewing)
VI	Abducens	Motor (eye movement)
VII	Facial	Mixed (facial expression, taste)
VIII	Vestibulocochlear	Sensory (hearing, balance)
IX	Glossopharyngeal	Mixed (taste, swallowing)
X	Vagus	Mixed (autonomic control of heart, lungs, digestion)
XI	Accessory	Motor (shoulder and neck muscles)
XII	Hypoglossal	Motor (tongue movement)

Nerve Anatomy

Nerves are composed of bundles of axons, surrounded by connective tissue layers that provide structure and protection.

• Fascicle: Bundle of nerve fibers within a nerve.

• Perineurium: Connective tissue surrounding each fascicle.

• Epineurium: Outermost connective tissue covering the nerve.

• Endoneurium: Surrounds individual nerve fibers.

• Myelin sheath: Insulates axons, increasing conduction speed.

• Axon: Transmits electrical impulses.

Additional info:

• Muscle groups are often tested using images; knowing both anatomical location and function is essential for lab exams.

• Latin abbreviations are commonly used in anatomical labeling.