Anatomy & Physiology Lab Practical 2 Study Guide: Muscle Tissue, Nervous Tissue, Brain, Spinal Cord, and Sensory Receptors

Muscle Tissue

Types of Muscle Tissue

Muscle tissue is specialized for contraction and is classified into three main types: skeletal, cardiac, and smooth muscle. Each type has unique structural and functional characteristics.

• Skeletal Muscle: Voluntary, striated muscle attached to bones; responsible for body movement.

• Cardiac Muscle: Involuntary, striated muscle found only in the heart; features intercalated discs for synchronized contraction.

• Smooth Muscle: Involuntary, non-striated muscle found in walls of hollow organs (e.g., intestines, blood vessels).

Key Structures to Identify:

Skeletal Muscle	Cardiac Muscle	Smooth Muscle
Muscle fiber Nucleus Striations Endomysium	Nucleus Striations Intercalated disc Endomysium	Nucleus Smooth muscle cell Endomysium

Neuromuscular Junction: The synapse between a motor neuron and a skeletal muscle fiber, essential for muscle contraction.

Skeletal Muscle Microanatomy

The skeletal muscle unit and sarcomere are the fundamental contractile structures. The sarcomere is the basic functional unit of striated muscle fibers.

• Sarcomere: The segment between two Z lines; contains actin (thin) and myosin (thick) filaments.

• Key Components: A band, I band, H zone, M line, Z line, actin, myosin, titin, troponin, tropomyosin, sarcolemma, sarcoplasmic reticulum, T tubule, triad.

Example: During muscle contraction, the sarcomere shortens as actin and myosin filaments slide past each other (sliding filament theory).

Nervous Tissue

Neurons and Neuroglia

Nervous tissue consists of neurons (nerve cells) and supporting glial cells. Neurons transmit electrical impulses, while neuroglia provide support and protection.

• Neuron Structures: Cell body, nucleus, nucleolus, Nissl substance, axon, dendrite, axon hillock, myelin sheath, Schwann cell, node of Ranvier, synaptic end bulb, synaptic cleft.

• Neuroglia: Supportive cells such as astrocytes, oligodendrocytes, microglia, and ependymal cells in the CNS; Schwann cells and satellite cells in the PNS.

Example: The myelin sheath increases the speed of nerve impulse conduction along the axon.

Gross Muscles

Major Muscles of the Human Body

Muscles are organized by region and function. Identification of major muscles and their associated structures is essential for understanding movement and anatomy.

• Muscles of the Head and Neck: Occipitalis, frontalis, temporalis, masseter, sternocleidomastoid.

• Muscles of the Trunk: Pectoralis major, rectus abdominis, external oblique, latissimus dorsi, trapezius, deltoid.

• Muscles of the Upper Limb: Biceps brachii, triceps brachii, brachialis, flexor carpi, extensor carpi.

• Muscles of the Lower Limb: Gluteus maximus, quadriceps group (rectus femoris, vastus lateralis, vastus medialis, vastus intermedius), hamstrings group (biceps femoris, semitendinosus, semimembranosus), gastrocnemius, tibialis anterior.

Muscle Actions: Each muscle produces specific movements at joints, such as flexion, extension, abduction, and adduction.

Brain

Major Brain Structures

The brain is divided into several major regions, each with distinct structures and functions.

• Cerebral Hemispheres: Frontal, parietal, temporal, occipital lobes; gyri and sulci; corpus callosum; white and gray matter.

• Diencephalon: Thalamus, hypothalamus, pineal gland.

• Brain Stem: Midbrain, pons, medulla oblongata.

• Cerebellum: Coordinates voluntary movements and balance.

• Ventricles: Lateral, third, and fourth ventricles; contain cerebrospinal fluid (CSF).

Functional Areas: Primary motor cortex, primary somatosensory cortex, primary visual cortex, primary auditory cortex.

Spinal Cord

Spinal Cord Anatomy

The spinal cord is organized into gray and white matter, with distinct regions and tracts for sensory and motor information.

• Gray Matter: Dorsal horn, ventral horn, lateral horn, gray commissure.

• White Matter: Dorsal, lateral, and ventral funiculi; ascending and descending tracts.

• Other Structures: Dorsal root, ventral root, dorsal root ganglion, central canal, anterior median fissure, posterior median sulcus.

Reflex Arc

Components of a Reflex Arc

A reflex arc is the neural pathway that mediates a reflex action. It typically involves a sensory neuron, interneuron, and motor neuron.

• Key Structures: Sensory neuron, interneuron, motor neuron, effector.

Example: The patellar reflex (knee-jerk) is a simple monosynaptic reflex arc.

General Sensory Receptors

Types of Sensory Receptors

Sensory receptors detect changes in the environment and transmit information to the nervous system.

• Pacinian (lamellar) corpuscle: Detects deep pressure and vibration.

• Meissner's (tactile) corpuscle: Detects light touch and texture.

Example: Meissner's corpuscles are abundant in fingertips, allowing for fine tactile discrimination.