Lab Exam 2 Review: Muscles, Nervous System, and Neuroanatomy

Head and Trunk Muscles

Overview of Major Muscles

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

• Orbicularis oculi: Encircles the eye; responsible for closing eyelids.

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

• Epicranius: Composed of the frontalis and occipitalis; raises eyebrows and moves scalp.

• Buccinator: Compresses cheek; aids in chewing.

• Zygomaticus: Elevates corners of mouth (smiling).

• Platysma: Tenses skin of neck; depresses mandible.

• Temporalis: Elevates and retracts mandible.

• Masseter: Elevates mandible; main chewing muscle.

• Sternocleidomastoid (SCM): Flexes and rotates head.

• Trapezius: Moves scapulae and supports arm.

• External/Internal intercostals: Aid in respiration by moving rib cage.

• Rectus abdominis: Flexes vertebral column; compresses abdomen.

• Transversus abdominis: Compresses abdominal contents.

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

• Levator ani: Supports pelvic organs.

• Coccygeus: Supports pelvic floor.

Arm and Leg Muscles

Major Muscle Groups

Muscles of the limbs are responsible for movement, posture, and stability. They are organized into groups based on their location and function.

• Biceps brachii: Flexes elbow and supinates forearm.

• Brachialis: Flexes elbow.

• Brachioradialis: Flexes forearm at elbow.

• Triceps brachii: Extends elbow.

• Flexor carpi radialis/ulnaris: Flexes wrist.

• Extensor carpi radialis/ulnaris: Extends wrist.

• Flexor digitorum: Flexes fingers.

• Extensor digitorum: Extends fingers.

• Gluteal group: Includes gluteus maximus, medius, minimus; extends and abducts hip.

• Quadriceps group: Extends knee; includes rectus femoris, vastus lateralis, vastus medialis, vastus intermedius.

• Hamstrings group: Flexes knee; includes biceps femoris, semitendinosus, semimembranosus.

• Adductor group: Adducts thigh.

• Gastrocnemius: Plantar flexes foot.

• Soleus: Plantar flexes foot.

• Tibialis anterior: Dorsiflexes foot.

Nervous System: Neuron and Brain Anatomy

Neuron Structure and Function

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

• Cell body (soma): Contains nucleus and organelles.

• Dendrites: Receive signals from other neurons.

• Axon: Transmits impulses away from cell body.

• Myelin sheath: Insulates axon, increases speed of impulse transmission.

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

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

Brain Regions and Landmarks

The brain is divided into several regions, each with specialized functions. Key anatomical landmarks help identify these regions.

• Cerebrum: Largest part; responsible for higher brain functions.

• Cerebellum: Coordinates movement and balance.

• Brainstem: Includes midbrain, pons, medulla oblongata; controls vital functions.

• Corpus callosum: Connects left and right cerebral hemispheres.

• Thalamus: Relay station for sensory information.

• Hypothalamus: Regulates homeostasis, endocrine functions.

• Pineal gland: Produces melatonin; regulates sleep.

• Gyri and sulci: Folds and grooves that increase surface area.

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

• Longitudinal fissure: Separates cerebral hemispheres.

Spinal Cord Anatomy

Structure and Function

The spinal cord is a major pathway for information traveling between the brain and the body. It is protected by vertebrae and surrounded by meninges.

• Pia mater: Innermost meningeal layer.

• Arachnoid mater: Middle meningeal layer.

• Dura mater: Outermost meningeal layer.

• Ventral root: Contains motor neuron axons.

• Dorsal root: Contains sensory neuron axons.

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

• Gray matter: Contains neuron cell bodies.

• White matter: Contains myelinated axons.

Cranial Nerves I-XII

Names and Functions

The twelve cranial nerves are responsible for sensory and motor functions of the head and neck. Each has a specific name and number.

Number	Name
I	Olfactory
II	Optic
III	Oculomotor
IV	Trochlear
V	Trigeminal
VI	Abducens
VII	Facial
VIII	Vestibulocochlear
IX	Glossopharyngeal
X	Vagus
XI	Accessory
XII	Hypoglossal

Nerve Anatomy

Components of a Nerve

Nerves are bundles of axons in the peripheral nervous system. They are organized into fascicles and surrounded by connective tissue layers.

• Endoneurium: Surrounds individual axons.

• Perineurium: Surrounds fascicles (bundles of axons).

• Epineurium: Surrounds entire nerve.

• Nerve fiber: Refers to the axon itself.

• Myelin sheath: Insulates axons, increases conduction speed.

• Axon: Transmits electrical impulses.

Additional info:

• The myelin sheath is produced by Schwann cells in the peripheral nervous system and oligodendrocytes in the central nervous system.

• Motor neurons transmit impulses from the CNS to muscles, while sensory neurons carry information from sensory receptors to the CNS.