Anatomy and Physiology of the Integumentary System PDF

**HOMEOSTASIS** **Anatomy --** structure **Physiology --** function **Morphology --** form / unique features or structure **[Approaches to the study of Anatomy]** **Systemic --** study of body by systems **Regional --** study of body by areas **[Areas of Specialization]** **Gross Anatomy --** l...

**HOMEOSTASIS** **Anatomy --** structure **Physiology --** function **Morphology --** form / unique features or structure **[Approaches to the study of Anatomy]** **Systemic --** study of body by systems **Regional --** study of body by areas **[Areas of Specialization]** **Gross Anatomy --** large structures of the body. **Microscopic Anatomy --** small structure of the body. **Cytology --** study of cell **Histology --** study of tissue **PHYSIOLOGY --** processes and function of living things. **Atom --** single **Molecule - structure** **Goals:** - Understand and predict body's responses to stimuli - Understand how the body maintains conditions within a narrow range of values in the presence of continuality changing internal and external environment. **[Levels of Organization]** 1. Chemical 2. Cellular 3. Tissue 4. Organs 5. Organ System 6. Organism **Metabolism --** usage and production of energy. **Cell --** smallest unit of life **Specialized Cells --** function of identity, function, specific **Unspecialized Cells --** no specific function, structure, stem cells **TISSUE** **Skeletal Muscle Cells** (voluntary) -- skeletal tissue **Cardiac Muscle Cells --** striation, disks **Smooth Muscle Cells** (involuntary) -- we cannot control **Blood --** connective tissue, connects your body **ORGANS --** made up of different types of tissue and cells - Two or more organs working together to accomplish a particular task. When the organ system combined, it becomes **organism.** **BASICS OF LIFE** **Characteristics of life:** **Organization -** refers to the specific interrelationships among the parts of an organism and how those parts interact to perform specific functions. **Metabolism --** ability to use energy to perform vital functions **Anabolism --** build molecules from smaller ones to create muscle **Catabolism --** breaks down large molecules to produce energy **Responsiveness --** respond to different stimuli **Growth --** increase in size **Development --** develop changes **Reproduction Vs. Production** **Reproduction --** making your own copy **Production --** IVF **HOMEOSTASIS --** internal balance, failure: death. **Physiological parameter -- BP, Temperature** **Homeostatic Mechanism --** to become balance again the homeostasis. - Set point / normal range **Fluctuation --** difference from the normal value **Negative Feedback --** brings back body to normal value Examples: sweating, shivering, diabetes **Positive Feedback --** intensifies the change Example: contractions during child birth **TISSUE** - Group of cells with similar structure and function. - The microscopic study of tissue structure is called **histology.** - Changes in tissues can result in development, growth, aging, trauma, or disease. **Epithelial Tissues** - Covers external and internal surfaces throughout the body. - Also forms most glands. - Consists almost entirely of cells with very little extracellular material between them. - **Basement Membrane --** function as a filter and a barrier to the movement of cells. **Functions of Epithelia** - Protecting underlying structures - Acting as barrier - Permitting the passage of substances - Secreting substances - Absorbing substances **Classification of Epithelia** - Epithelia are classified according to the number of cell layers and the shape of the cells. - **Stratified cuboidal epithelium --** sweat gland ducts, ovarian follicular cells, and salivary glands. - **Stratified columnar epithelium --** mammary gland ducts, larynx, and a portion of the male urethra. This epithelium carries out secretion, protection, and some absorption. - **Transitional epithelium --** stretch, urinary bladder +-----------------------------------+-----------------------------------+ | **Number of Layers or Category** | **Shape of Cells** | +===================================+===================================+ | **Simple (single layer of | **Squamous, Cuboidal, Columnar** | | cells)** | | +-----------------------------------+-----------------------------------+ | **Stratified (more than one layer | **Squamous** | | of cells)** | | | | **Nonkeratinized (Moist)** | | | | | | **Keratinized** | | | | | | **Cuboidal (very rare)** | | | | | | **Columnar (very rare)** | +-----------------------------------+-----------------------------------+ | **Pseudostratified (modification | **Columnar** | | of simple epithelium)** | | +-----------------------------------+-----------------------------------+ | **Transitional (modification of | **Roughly cuboidal to columnar | | stratified epithelium)** | when not stretched and squamous | | | like when stretched** | +-----------------------------------+-----------------------------------+ **Glandular Epithelium** **Endocrine Glands --** ductless gland - Towards the inside of the body - Hormones **Exocrine Glands --** has ducts - Outside of the body **Methods of Secretion: Exocrine** - **Merocrine --** secrete their products through exocytosis without losing any cellular material (sweat glands)  - **Apocrine --** release their secretions along with a portion of the cell's cytoplasm (mammary glands) - **Holocrine --** involves the rupture and destruction of the entire gland cell (sebaceous glands)  **Structural and Functional Relationships** - Cell layers and Cell shapes - The number of cell layers and the shape of the cells in a specific type of epithelium reflect the function the epithelium performs. - **Simple Epithelium --** is found in organs that primarily function to **move materials.** - **Stratified Epithelium --** is well adapted for its protective function. - Cells are not normally **flat and thin** when the function is diffusion - Cells with the major function of secretion or absorption are usually **cuboidal or columnar.** They are larger because they contain more organelles. - Free Surfaces - **Microvilli --** increase free surface area - **Cilia --** propel materials along the free surface of cells - **Goblet Cells --** produces mucus - The constant movement of mucus helps keep the airways clean. **Connective Tissue --** found throughout the body **Connective Tissue has 4 basic types** **Loose Connective Tissue --** fewer fibers, more ground substance - Areolar - Adipose - Reticular **Dense Connective Tissue -** more fibers, less ground substance - Dense, regular collagenous - Dense, regular elastic - Dense, irregular collagenous (not shown) - Dense, irregular elastic (not shown) **Supporting Connective Tissue** **Cartilage --** Semi solid matrix - Hyaline - Fibrocartilage - Elastic **Bone --** solid matrix - Spongy - Compact **Fluid Connective Tissue** - Blood - Hemopoietic Tissue - Red Marrow - Yellow Marrow  **Muscle Tissues**  **Summary** - A **tissue** is a group of cells with similar structure and function. - **Histology** is the study of tissues. - **Epithelial Tissue --** covers surfaces - **Connective Tissue --** connect, support, and bind - **Muscle Tissue --** contract **INTEGUMENTARY SYSTEM** **Integumentary System -- Covering** **SKIN** **3 major tissue layers:** - **Epidermis --** most superficial (avascular -- no blood vessels) - **Dermis --** thickest structure (vascular) - **Hypodermis --** connect the skin to underlying muscle or bone (subcutaneous layer)  **EPIDERMIS --** thin, thick skin -- 5 layers - **Thin Skin --** all over your body (4 layers) basale, spinosum, granulosum, and corneum. - **Thick Skin --** palms and soles (5 layers) basale, spinosum, granulosum, corneum, lucidum. - **Keratinization --** movement, cells change shape and chemical composition - **Keratinocytes --** a cell that manufactures and stores the protein keratin - **Keratin --** intracellular fibrous protein that gives hair, nails, and skin their hardness and water-resistant properties. - bond to the dermis via intertwining collagen fibers, referred to as the **basement membrane --** nutrient exchange - **Basal cell --** precursor - **Merkel cell --** receptor - **Melanocytes --** produces melanin (color) - **Desmosomes** (bind cells) - Keratinocytes are dead and flattened - Keratinization begins - **Langerhans cells --** immune cells - acts as a barrier - facilitates the exchange of nutrients and waste products between the avascular epidermis and the vascular dermis. **DERMIS** - contains hair follicles and sweat glands **Cleavage Lines --** more collagen fibers are oriented in some directions than in others. - Scar formation - **Dermal Papillae --** (finger prints and footprints) **HYPODERMIS / SUBCUTANEOUS TISSUE** - Attached skin to the underlying bone and muscle - Has **adipose tissue (fat)** **SKIN ACCESSORY** **Hair** - **Hair Shaft** - **Hair Follicle --** produce new cells - **Arrector Pili --** goosebumps **Nails --** keratinized (hard type of keratin) **Glands** - sebaceous glands - **Sweat glands** - **Eccrine --** sweat (merocrine); most numerous -- palm and soles **thermoregulation** - **Apocrine --** armpits and genitalia **body odor** **PHYSIOLOGY** **Protection** - reduces water loss - prevents microorganisms and other foreign substances from entering the body - protects underlying structures against abrasion - melanin absorbs UV light - Hair protection - Hair on the head acts as a heat insulator - Eyebrows keep sweat out of the eyes - Hair in the nose and ears prevents the entry of dust and other materials - Nails protects fingers and toes and can be used for defense **Sensation** - Receptors in the epidermis and dermis can detect pain, heat, cold, and pressure - Hair does not have a nerve supply, sensory receptors around hair follicle can detect the movements of a hair. **Vitamin D** - When the skin is exposed to ultraviolet light, a precursor molecule of vitamin D is formed - The precursor is carried by the blood to the liver, where it is modified, and then to the kidneys, where the precursor is modified further to form active vitamin D. **Temperature Regulation** - In order to maintain homeostasis, the body must rid itself of excess heat. - Blood vessels in the dermis dilate and enable more blood to flow within the skin (vasodilation) **Excretion** - Minor role - In addition to water and salts, sweat contains small amounts of waste products, such as urea, uric acid, and ammonia **DISEASES AND DIAGNOSTIC AID** **Diagnosis** - The integumentary system is useful in diagnosis because it is observed easily and often reflects events occurring in other parts of the body. - **Cyanosis (bluish color of skin)** -- decreased oxygen content - **Jaundice (yellowish color) --** liver is damaged by a disease - Liver secretes bile pigments which are yellow and their buildup on the blood and tissue can mean liver dysfunction - The condition of the skin, hair and nails is affected by nutritional status - **Vitamin A deficiency -- skin produces extra keratin and assumes sandpaper texture** - **Iron deficiency --** deficiency anemia affects nail contour and become flat or concave **Burns --** injury to a tissue caused by heat, cold, friction, chemicals, electricity, or radiation **Skin Cancer --** most common type of cancer - Chemicals and radiation are known to induce cancer, most often it is associated to exposure to UV light. - Light-skinned people over the age of 50 if they have long exposure to the sun **Effects of Aging** - As the body ages, the skin is more easily damaged because the epidermis thins and the amount of collagen in the dermis decreases - A decrease in the number of elastic fibers in the dermis and loss of adipose tissue to sag and wrinkle. - Melanocytes decrease but increases in some area to produce age spots or freckles. **Skull** - 22 bones of the skull, divided into 2 - **Braincase (cranial bones) -- 8 bones** - **Facial Bones 14 bones** - Only 1 is freely movable -- Mandible (jaw) **Skull: Cranial Bones** - **Frontal Bone** - **Parietal Bone** - **Temporal Bone** - **Occipital Bone** - **Ethmoid Bone** - **Sphenoid Bone (**Butterfly) **Skull: Facia Bone** - Entrance to the respiratory and digestive tracts **Skull Sutures** - **Coronal Suture (frontal and parietal)** - **Squamous Suture (temporal and parietal)** - **Lambdoid Suture (occipital and parietal)** - **Sagittal Suture (two parietal)** - **Frontanelle -- connective tissue (protect babies brain)** - **Nasal -- nose (2)** - **Lacrimal (2)** - **Inferior nasal concha (2)** - **Maxilla (2)** - **Mandible -- jaw (1)** - **Zygomatic -- cheekbones (2)** - **Vomer** - **Palatine -- mouth palette (2)** **VERTEBRAL COLUMN** - Backbone - Central axis of the skeleton - Regions - 7 cervical vertebra - 12 thoracic vertebra - 5 lumbar vertebra - 1 sacral bone - 1 coccyx bone **VERTEBRAL COLUMN: CURVATURES** - **Cervical Region --** anterior curve (C1-C8) - **Thoracic Region --** posterior curve (T1-T12) - **Lumbar Region --** anterior curve (L1-L5) - **Sacral and coccygeal region --** posterior curve (S1-S5) **Kyphosis (kuba) --** abnormal posterior curvature of the spine, mostly in the upper thoracic region. **Lordosis (duck-like) --** abnormal posterior curvature of the spine, mainly in the lumbar region, resulting in a sway back conditon. **Scoliosis --** is an abnormal lateral curve of the spine **RIB CAGE** - Protects the vital organs within the thorax - The 12 pairs of ribs can be divided into true ribs and false ribs - **True Ribs --** 1-7, attach directly to the sternum by means of costal cartilages. - **False Ribs --** 8-12, attach to the sternum by a common cartilage. - **-** ribs 11 and 12 do not attach at all to the sternum and are called **floating ribs.**  **APPENDICULAR SKELETON (Upper and Lower Limbs)** **Pectoral Girdle or Shoulder Girdle** - Consists of 4 bones - 1 scapula or shoulder blade - 2 clavicle - **Arm** - **Humerus --** bone of the arm - **Forearm** - **Ulna --** medial side - **Radius --** lateral - **Wrist** - 8 carpal bones - **Hands** - **5 metacarpal bones** - **Phalanges** **Pelvic Girdle** - Place where the lower limbs attach to the body - The right and left coxal bones, or hip bones, join each other anteriorly and the sacrum posteriorly to form a ring of bone called **pelvic girdle.** **Coxal Bone** - Three bones fused to form a single bone - **Ilium --** superior - **Ischium --** inferior and posterior - **Pubis --** inferior and anterior - Coxal bones are joined anteriorly at the pubic symphysis  **Lower Limb** - Thigh - **Femur** - **Patella --** knee cap - **Leg** - **Tibia --** larger, weight-bearing bone - **Fibula** - **Ankle** - **Tarsal** - **Foot** - **Metatarsal** - **Phalanges**  **JOINTS OR ARTICULATION** - Place where two bones come together. - Movable, but not always - Two systems of classifying bones - Functional / degree of motion - Type of connective tissue **TYPES OF CONNECTIVE TISSUE** - Fibrous - Cartilaginous - Synovial **Fibrous Joints** - Two bones that are united by fibrous tissue and that exhibit little or no movement **Basis of structure** - **Suture --** between the bones of the skull - **Syndesmoses --** separated by some distance and held together by ligaments - **Gomphoses --** pegs to sockets **Cartilaginous Joints** - Slight movement; cartilage - Fibrocartilage **Synovial Joints** - Freely movable joints that contains fluid in a cavity - Most joints of the appendicular skeleton **TYPES OF MOVEMENT** - **Flexion and Extension** - Foot movement - **Plantar Flexion --** towards the plantar - **Dorsiflexion --** towards the shin - **Abduction --** away from the median - **Adduction --** towards the median When the elbow is flexed, - **Pronation --** is rotation of the forearm so that the palm is down. - **Supination --** is rotation of the forearm so that the palm faces up - **Rotation** - **Circumduction --** limbs move in a circle **Functions** - **Support** - **Bone --** bearing weight, major support - **Cartilage --** firm yet flexible support within certain structures - **Ligaments --** attach to bones and hold them together - **Protection --** protects the organs - **Movement** - **Storage --** minerals (calcium and phosphorus) - **Blood cell production** **Extracellular Matrix** - **Collagen --** tough, ropelike protein. - **Proteoglycan --** large molecules consisting of polysaccharides attached to core proteins. Help retain water and provide resilience to the bone. - **Calcium** - **Phosphate** **GENERAL FEATURES** **Bone Categories** **4 categories** - **Long Bones --** most of the upper and lower limbs - **Short Bones --** bones of the wrist and ankle - **Flat Bones --** thin and flattened, skull, ribs - **Irregular Bones --** vertebrae and facial bones **Long Bones** - **Diaphysis --** central shaft - **Epiphysis --** two ends - **Articular Cartilage --** covers the end of epiphysis - **Epiphyseal plate --** growth plate, bone grows in length - **Epiphyseal line --** present in adults, bone stops growing - **Medullar Cavity --** - **Yellow Marrow --** mostly in adults **-- adipose tissue** - **Red Marrow --** mostly in children **-- blood-forming cells** - **Periosteum --** dense connective tissue - Around the bone - **Endosteum --** surface of the medullary cavity is lined with a thinner connective tissue membrane - inside the bone - Periosteum and endosteum contain **osteoblasts** (bone-forming cells) - **Osteocytes --** mature bone cells - **Osteoclasts --** destroys old bone tissue - **Ossification --** formation of bone by osteoblasts - **Lamellae --** thin sheets of extracellular matrix - **Lacunae --** spaces inside the lacunae where osteocytes are found. - **Canaliculi --** small passageway **Bone Tissue** - **Compact Bone --** mostly solid matrix and cells - **Spongy Bone (cancellous bone) --** consists of a lacy network of bone with many small, marrow-filled spaces. **Compact Bone** - Forms most of the diaphysis of a long bone and the thinner surfaces of all other bones - **Osteons --** predictable pattern of repeating units - Rings of lamellae surround a central canal - **Haversian canal --** central canal **Spongy Bone** - **Trabeculae --** delicate interconnecting rods or plates of bone - Scaffolding - No blood vessels penetrate the trabeculae, and the trabeculae have no central canals **Bone Calcium and Homeostasis** - Calcium moves into bone as osteoblasts build new bone and out of bone as osteoclasts break down bone - When blood calcium levels are too low, osteoclast activity increases, osteoclasts release calcium from bone into blood, and blood calcium levels increase. **MUSCULAR SYSTEM** **Functions:** - Movement of the body - Maintenance of posture - Respiration - Production of body heat - Communication - Constriction of organs and vessels - Heart contraction **Skeletal Muscle --** multiple nuclei **Cardiac Muscle** **Smooth Muscle**  **SKELETAL MUSCLE --** most of the muscles are attached to the skeletal system - Striated Muscles **Functional Characteristics** - **Contractility --** shorten with force - **Excitability --** respond to a stimulus - **Extensibility --** stretch - **Elasticity --** recoil to their original resting length after they have been stretched **Structure** - **Epimysium --** connective tissue that surrounds the skeletal muscle - **Perimysium --** connective tissue that subdivides a whole muscle cell - **Fasciculi (fascicle) --** bundles - **Endomysium --** each fascicle is then subdivided by a loose connective tissue - **Sarcolemma --** cell membrane of the muscle fiber - **Transverse Tubules (T-tubules) --** connects sarcolemma to the sarcoplasmic reticulum - **Sarcoplasmic Reticulum --** specialized organelle in muscle cells **Sarcoplsm --** cytoplasm **Myofibrils --** actin and myosin **Sarcomeres --** organized, repeating units of actin and myosin **Physiology of Contraction** - **Sarcomere --** functional contractile unit of a striated muscle. - **Actin --** thin filaments - **Myosin --** thick filaments - **Z-lines --** actin attached; sarcomere end - **M-line --** holds thick filaments **Actin myofilaments** - **Actin** - **Troponin** - **Tropomyosin** **Myosin myofilaments -- myosin heads** **Sliding Filament Theory** - Muscle contraction is initiated when muscle fibers are stimulated by a nerve impulse - This causes calcium ions to be released - When calcium ions are released, they bind to troponin, displacing tropomyosin and exposes the myosin binding sites - At this stage, the head myosin unit is bound to an ADP and a phosphate molecule (decomposed ATP) from previous contraction     \\  **Smooth Muscle --** small and spindle shaped - Less actin and myosin than skeletal - No sarcomere -- not striated - Contracts more slowly - Involuntary control **Cardiac Muscle --** long striated and branching - Connected by intercalated disks - This cellto-cell connection allows cardia muscle cells to function as a unit **Naming Skeletal Muscle** - Location of the Muscle - Shape - Size - Direction / orientation - Number of origins - Location of attachment - Action **LOCATION** - **Frontalis --** frontal (occipitofrontalis) - **Lateralis --** lateral or on the side (vastus lateralis) - **Tibialis anterior --** front of tibia - **Supra --** above (suprahyoid) - **Infra --** below (infrahyoid) - **Sub --** underneath (subscapularis) **SHAPE** - **Deltoid --** triangle - **Latissimus --** wide - **Teres --** round - **Trapezius --** trapezoid - **Serratus --** saw-tooth (serratus anterior) - **Orbicularis --** circular **SIZE** - **Maximus --** largest (gluteus maximus) - **Minimus --** smallest (gluteus minimus) - **Vastus --** huge - **Longus --** longest - **Brevis --** short - **Major --** large (pectoralis major) - **Minor --** small (teres minor) **DIRECTION OF FIBERS** - **Rectus (straight) --** parallel to the muscle - **Transversus (transverse) --** at right angle to the muscles long axis - **Oblique --** diagonal  **ACTION** - **Flexor carpi radialis --** flexes wrist - **Abductor magnus --** abducts the thigh - **Extensor digitorum --** extends the fingers - **Levator --** lifts a structure - Receiving sensory input - Integrating information - Controlling muscles and glands - Maintaining homeostasis - Establishing and maintaining mental activity **Division of the Nervous System** - **Central Nervous System** - **Brain** - **Spinal Cord** - **Peripheral Nervous System** - **Nervous tissue outside CNS** - PNS functions to link the CNS with the various parts of the body - **Sensory (afferent division** conducts action potentials from sensory receptors to the CNS - **Sensory neurons** - **Motor (efferent) division** conducts action potentials from the CNS to effector organs, such as muscles and glands - **Motor neurons** **Sensory (afferent division) --** nerve fibers that carry information to the central nervous system **Motor (efferent) division --** nerve fibers that carry impulses away from the nervous system - Motor division is divided based on the type of effector being innervated - **Somatic NS --** transmits action potentials from the CNS to **skeletal muscles** - **Autonomic NS --** transmits action potentials from the CNS to **cardiac muscle, smooth muscle and glands.** - Divided into sympathetic and para sympathetic nervous system **Enteric Nervous System** - Has both sensory and motor neurons contained wholly within the digestive tract - Can function without input from the CNS or other parts of the PNS  **CELLS OF THE NERVOUS SYSTEM** - **Neurons** - **Glial Cells** **Neurons or Nerve Cells** - Receive stimuli, conduct action potentials, and transmit signals to other neurons or effector organs. - Parts: - Cell body - Dendrites - Axons - **Cell body --** contains a single nucleus - nucleus of the neuron is the **source of information** for gene expression - **Dendrites -- receive information** from other neurons or from sensory receptors and transmit the information toward the neuron cell body - **Axon --** single long cell process extending from the neuron cell body - Conduct action potential - **Axon hillock --** area where the axon leaves the neuron cell body **Types of Neurons** - **Multipolar --** most motor and CNS neurons - To receive input from many different source - **Bipolar --** special senses - **Pseudo unipolar --** most sensory neurons **Glial Cells or Neuroglia** - Primarily supportive cells of the CNS and PNS - These cells **do not conduct action potentials** - Most neuroglia retain the ability to divide, whereas neurons do not. - **Astrocytes -- major supporting cell** - Can stimulate or inhibit the signaling activity of nearby neurons - Participate with the blood vessel endothelium to form a permeability barrier, called the **blood brain barrier,** between the blood and the CNS **Blood-brain barrier --** separates blood from the brain's extracellular fluid - **Ependymal cells --** line the fluid-filled cavities (ventricles and canals) wuthin the CNS - Some cells produce cerebrospinal fluid - Some with cilia on the surface, help move the cerebrospinal fluid through the CNS - **Oligodendrocytes (CNS); Schwann Cells (PNS)** - Provides an insulating material that surround the axons - Forms the myelin sheath - **Microglia --** immune cells of the CNS - Help protect the brain by removing bacteria and cell debris **Myelin Sheaths** - Specialized laters that wrap around the axons of some neurons - Axons with these myelin sheaths are called **myelinated axons** - Prevents almost all ion movement across the cell membrane. - Gaps are called **nodes of Ranvier --** ion movement can occur at the nodes of ranvier - Myelination of an axon increases the speed and efficiency of action potential **Organization of the Nervous Tissue** - **Gray Matter** consists of groups of neuron cell bodies and their dendrites, where there is very **little myelin** - **White Matter --** parallel axons **with myelin sheaths** **Electrical Signals and Neural Pathways** **Resting Membrane Potential** - Cells exhibit chemical properties - **Polarized** - Inside of most cell membranes is negatively charged - Outside of the cell membrane is positively charged - **Generated by 3 main factors** **Factors -- RMP** - Higher concentration of K+ immediately inside the cell membrane - A higher concentration of Na+ immdiately outside the cell membrane - Greater permeability of the cell membrane to K+ than to Na+ - Difference in membrane permeability is due to the difference in the number of open ion channels. **Ion Channels** - **Leak Channels** are always open - When a cell is at rest, the membrane potential is established by diffusion of ions through leak channels. - Because there are 50-100 times more K+ leak channels than Na+ leak channels, the resting membrane has much greater permeability to K+ than to Na+ - **Gated Channels** are closed until opened by specific signals - **Chemically gated channels** are opened by neurotransmitters or other chemicals - **Voltage-gated channels** are opened by a change in membrane potential **Action Potentials** - Rapid sequence of changes in the voltage across a membrane - Muscle and nerve cells are **excitable cells,** meaning that the **resting membrane potential changes in response to stimuli** that activate gated ion channels - The opening and closing of gated channels can change the premeability characteristics of the cell    **Action Potential** - In summary, the resting membrane potential is set by the activity of the leak channels. **On stimulation,** chemically gated channels are opened and initiate local potentials. If sufficiently strong, the local potentials activate voltage-gated channels to initiate an action potential. - **All-or-none** - **Threshold is reached = action potential** - **Threshold is not reached = no action potential** - **Continuous Conduction --** action potential propagation across unmyelinated axons - **Saltatory Conduction --** in myelinated axons, action potentials "jump" from one node of Ranvier to the next along the length of the axon. **SYNAPSE** - Junction where the axon of one neuron interacts with another neuron or with cells of an effector organ, such as a muscle gland - End of the axon forms a **presynaptic terminal** - The membrane of the dendrite or effector cell is the **postsynaptic membrane** - Space separating the presynaptic and postsynaptic membranes is the **synaptic cleft** - Chemical substances called **neurotransmitters** are stored in **synaptic vesicles** in the presynaptic terminal. **Reflexes** - Involuntary reaction in response to a stimulus applied to the periphery and transmitted to the CNS - Allow a person to react to stimuli more quickly than is possible if conscious thought is involved - **Reflex arc --** basic functional unit of the nervous system because it is the smallest, simplest pathway capable of receiving a stimulus and yielding a response **CENTRAL AND PERIPHERAL NERVOUS SYSTEM** - **Central Nervous System** - **Brain** - **Spinal Cord** - **Peripheral Nervous System** - **Nerves** - 12 cranial nerves - 31 spinal nerves - **Ganglia (cells of PNS) outside the brain and the spinal cord** **SPINAL CORD** - Extends from the foramen magnum at the base of the skull **SPINAL NERVES** - Arise along the spinal cord from the union of the dorsal roots and ventral roots - Contain axons of both sensory and somatic motor neurons and thus are called **mixed nerves** - Categorized by the region of the vertebral column from which they emerge - Cervical (C), Thoracic (T), Lumbar (L), Sacral (S), and Coccygeal (Co) - 31 pairs of spinal nerves - C1 through C8 - T1 through T12 - L1 through L5 S1 through S5 - Co - **Dermatome** is the area of skin supplied with **sensory innervation** by a pair of spinal nerves except C1  **SPINAL CORD: PLEXUS** - Plexus is a network of nerves - Spinal nerves T2 through T11 do not join a plexus because they directly control the muscles and skin is the chest and abdomen - Three major plexus - **Cervical plexus --** neck, upper shoulders - **Phrenic nerve --** **diaphragm** - **Brachial plexus --** upper limbs - **Lumbosacral plexus --** lower limbs and pelvic region **BRAIN** **Major Regions:** - **Brainstem** - **Cerebellum** - **Diancephalon** - - **Cerebrum**  **BRAINSTEM** - Connects the spinal cord to the remainder of the brain - Control of heart rate, blood pressure, and breathing - Damage to small areas of the brainstem can cause death **Medulla Oblongata** - Most inferior portion of the brainstem and is continuous with the spinal cord - Regulation of heart rate and blood vessel diameter, breathing, swallowing, vomiting, coughing, sneezing, balance, and coordination **Pons** - Functional bridge between the cerebrum and cerebellum - Breathing, swallowing, balance, chewing and salivation **Midbrain** - Smallest region of the brainstem - Coordinating eye movements and controlling pupil diameter and lens shape - **Inferior colliculi --** major relay centers for the auditory nerve pathways - **Superior colliculi --** visual reflexes and receive touch and auditory input **Cerebellum** - Involved in maintaining balance and muscle tone and in coordinating fine motor movement **Diencephalon** - Part of the brain between the brainstem and the cerebrum - **Thalamus --** largest part of the diencephalon. - Processes and send sensory information to the appropriate areas of the cerebral cortex for interpretation. - **Hypothalamus --** body homeostasis - Linking the nervous system to the endocrine system via the pituitary gland - Control of body temperature, hunger, and thirst. - Sensations such as sexual pleasure, rage, fear, and relaxation after a meal - **Epithalamus --** small area superior and posterior to the thalamus - Emotional and visceral response to odors (nausea or disgust), and the pineal gland - **Pineal gland --** regulating the body's circadian rhythms - Releases melatonin **Cerebrum** - Largest part of the brain - **Longitudinal fissure --** divides left and right hemisphere **Gyri --** folds **Sulci --** grooves - **Frontal Lobe --** control of voluntary motor functions, motivation, aggression, mood, and ofactory (smell) reception. - **Parietal Lobe --** principal center for receiving and consciously perceiving most sensory information, such as touch, pain, temperature, and balance - These two are separated by the **central sulcus** - **Occipital Lobe --** receiving and perceiving visual input - **Temporal Lobe --** involved in olfactory (smell) and auditory (hearing) sensations and plays an important role in memory **SENSORY FUNCTIONS** - The CNS constantly receives a variety of stimuli originating both inside and outside the body. - A small portion of the sensory input results in **perception,** the conscious awareness of stimuli **Ascending Tracts** - Transmit information via action potentials from the periphery to various parts of the brain - Sensory tracts typically **cross from one side of the body** in the spinal cord or brainstem to the other side of the body. Thus, the **left side of the brain receives sensory input from the right side** of the body and vice versa. - **Primary Sensory areas --** ascending tracts project to specific regions of the cerebral cortex; sensations from all senses are perceived - **Primary somatic sensory cortex --** involved in processing sensory information related to the body - **Association areas --** involved in the process of recognition - Have I seen this before? **MOTOR FUNCTIONS** - Responsible for maintaining the body's posture and balance, as well as moving the trunk, head, limbs, tongue, and eyes, and communicating through facial expressions and speech - Involuntary and voluntary movements **Descending Tracts** - Transmit information via action potentials from the brain to various parts of the body **Motor Aras of the Cerebral Cortex** - **Primary motor cortex --** action potentials initiated in this region control voluntary movements of skeletal muscle - **Premotor area --** where motor functions are organized before they are actually initiated in the primary motor cortex - **Prefrontal area --** motivation and foresight to plan and initiate movements **Meninges and Cerebrospinal fluid** **Meninges --** surround and protect the brain and spinal cord - **Dura mater --** most superficial and thickest of the meninges - **Arachnoid mater --** thin and mispy - **Sub --** **dural space** -- between dura mater and arachnoid mater - **Pia mater --** very tightly bound to the surface of the brain and spinal cord - **Subarachnoid space --** between the arachnoid mater and the pia mater **Cerebrospinal Fluid** - Bathes the brain and spinal cord, providing a protective cushion around the CNS **Cranial Nerves** - **Olfactory --** smell - **Optic --** vision - **Oculomotor --** eye movement, eyelid movement, pupillary constriction - **Trochlear and abducens --** eye movement but different eye muscles - **Trigeminal --** cutaneous (skin) sensation, controlling muscles of mastication - **Facial --** facial expressions - **Vestibulocochlear --** senses of hearing and balance - **Glossopharyngeal --** controlling muscles in the oral cavity and upper throat, as well as part of sense of taste and the production of saliva. - **Vagus --** responsible for contributing to homeostatic control of the organs of the thoracic and upper abdominal cavities. - **Spinal accessory --** controlling the muscles of the neck, along with cervical spinal nerves. - **Hypoglossal nerve --** responsible for controlling the muscles of the lower throat and tongue.  **AUTONOMIC NERVOUS SYSTEM** - **Sympathetic** - Fight-or-flight - Prepares the body for physical activity - **Parasympathetic** - Rest-and-digest - Stimulates involuntary activities of the body at rest **Spinal Cord** - Consists of a superficial white matter portion and a deep gray matter portion **White matter:** - **Dorsal (posterior) --** sensory (afferent nerves) - **Ventral (anterior) --** motor (efferent nerves) - **Lateral columns**