Download Nursing Students notes for Anaphy and more Study notes Biology in PDF only on Docsity!
ANATOMY AND PHYSIOLOGY
Anatomy – The study of the structures of the body
Physiology – The study of the processes and functions of the body.
What does the human body consist of?
Water – is found in the extracellular fluids of the body.
Proteins – serve as the major structural component of the body. An important constituent of the cell membrane.
Carbohydrates – are present in the human body largely as fuels. A storage compound found in the liver and the muscles.
Nucleic Acids – make up the genetic materials of the body.
6 Levels of Organization in the Human Body
- Chemical Level – a combination of atoms to form molecules.
- Cellular Level – Molecules combine to form cells, the basic structural and functional units of an organism that are composed of chemicals.
- Tissue Level – is a group of cells that work together to perform a particular function.
- Organ Level – two or more different types of tissues to perform a specific function.
- Organ System Level – related organ with a common function.
- Organismal Level – All the parts of the human body functioning together constitute the total organism, 11 Organ Systems in the Body integumentary Skeletal muscular
nervous respiratory urinary digestive reproductive lymphatic endocrine cardiovascular
6 essential characteristics of life
1. Organization - the specific relationship of individual parts of an organism 2. Metabolism - the ability to use energy to perform vital functions such as growth movement and reproduction 3. Responsiveness - the ability of an organism to sense change and adjust to maintain its life 4. Growth- an increase in the size of an organism 5. Development - the changes an organism undergoes over time 6. Reproduction - the formation of new cells or new organisms
Homeostasis- It is a self-regulation process of an organism to maintain stability while adjusting for survival. The cause of death means the loss of homeostasis Autopsy- examination of the body and deception of its internal organs to confirm or determine the cause of death.
BODY PARTS ANTERIOR AND
POSTERIOR VIEW
Anatomical- refers to a person standing upright with the face directed forward the upper limbs hanging to the side and the palms of the hands facing forward
Directional terms- always refer to the anatomical position regardless of the body's actual position
Superior – Towards the head, or the upper part of a structure.
Inferior – Away from the head, lower part of a structure.
Anterior – Nearer to or at the front of the body.
Posterior – Nearer to or at the back of the body.
Medial – Nearer to the midline
Lateral – Farther from the midline
Intermediate – Between two structures
Ipsilateral – On the same side of the body as another structure.
Contralateral – On the opposite side of the body from another structure
Proximal – Nearer to the origination of the structure.
Distal – Farther from the origination of the structure.
Superficial (external) – Towards or on the surface of the body
Deep (Internal) – Away from the surface of the body
PLANES AND SECTIONS
Sagittal plane - (medium plane) comes down vertically and divides a body organ into left and right parts.
Parasagittal plane - a plane parallel to the sagittal plane but off to one side.
Coronal plane - (frontal plane) splits everything vertically into the front and back.
Transverse - (horizontal plane) divides the body top and bottom.
Feedback system - it is a cycle of events in which the status of body condition is monitored, evaluated, changed, monitor reevaluated, and so on. There are three basic components of a feedback system these are the receptor, control center, and effector.
- Receptor - monitor changes in a controlled condition to the control center.
- Control Centre - sets the range of values within which a control condition should be maintained. Evaluate the input it receives from the receptor.
- Effector - receives the output from the control center and produces a response.
- Response - alters the controlled condition. Negative feedback system - reverse or change in a controlled condition ex. (High bp) Positive feedback system - strengthens or reinforces a change in one of the body's controlled conditions. ex. (normal childbirth)
Disorder - any abnormality of structure or function. Disease - is a more specific term for illness. It alters body structures and functions Local disease - affects in part or limited region of the body Systemic disease - either the entire body or several parts of it. Symptoms (subjective) - changes in body functions that are not apparent to an observer Signs (objective) - can be clinically observed. Epidemiology - it is the science that deals with how, why, and when diseases occur and how they are transmitted among individuals in a community.
Peroxisomes - are small, membrane- bound vesicles containing enzymes that break down fatty acids, amino acids, and hydrogen peroxide (H2O2)
Mitochondria - are small organelles with inner and outer membranes separated by a space.
Cytoskeleton - like the skeleton of the body, acts as the internal framework of the cell.
Centrosomes - a specialized area of cytoplasm close to the nucleus where microtubule formation occurs.
Cilia - move substances over the surface of cells.
Flagella - are much longer than cilia and propel sperm cells.
Microvilli - increase the surface area of cells and thus aid in absorption.
The Tissue Level of Organization
A tissue is a group of specialized cells that share a common structure and function. The microscopic study of tissue structure is called histology.
4 Types of Tissues
1. Epithelial Tissues - covers and protects surfaces, both outside and inside the body. Characteristics of Epithelial Tissues
- Mostly composed of cells.
- Covers body surfaces.
- Distinct cell surfaces.
- Cell and matric connections.
- Nonvascular
- Capable of regeneration.
Major Functions of Epithelial Tissues
- Protecting underlying structures.
- Acting as a barrier.
- Permitting the passage of substances.
- Secreting substances.
- Absorbing substances.
Classifications
1. Simple epithelium consists of a single layer of cells, with each cell extending from the basement membrane to the free surface. 2. Stratified epithelium consists of more than one layer of cells, but only the basal layer attaches the deepest layer to the basement membrane 3. Pseudostratified columnar epithelium is a special type of simple epithelium. The prefix pseudo- means false, so this type of epithelium appears to be stratified but is not. **Types of Epithelial Cells
- Squamous** (skwā ′mŭs) cells are flat or scalelike. 2. Cuboidal (cubelike) cells are cube-shaped—about as wide as they are tall. 3. Columnar (tall and thin, similar to a column) cells tend to be taller than they are wide.
Simple squamous epithelium is a single layer of thin, flat cells. Simple cuboidal epithelium is a single layer of cubelike cells that carry out active transport, facilitated diffusion, or secretion. Simple columnar epithelium is a single layer of tall, thin cells. The large size of these cells enables them to perform complex functions.
Pseudostratified columnar epithelium secretes mucus, which covers its free surface. Stratified squamous epithelium forms a thick epithelium because it consists of several layers of cells. Stratified cuboidal epithelium consists of more than one layer of cuboidal epithelial cells. Stratified columnar epithelium consists of more than one layer of epithelial cells, but only the surface cells are columnar. The deeper layers are irregular or cuboidal in shape. Glands are secretory organs. Glands are composed primarily of epithelium, with a supporting network of connective tissue. Exocrine Glands – glands with ducts. Both the glands and their ducts are lined with epithelium. Endocrine Glands – glands with no ducts. Endocrine glands have extensive blood vessels. Hormones – are products of endocrine glands.
3 Types of Exocrine Glands
Merocrine gland – produces vesicles that contain secretory products and exit through exocytosis. Apocrine gland – a portion of the cell with secretory products is pinched of the cell and joins secretion produced by the merocrine process. Holocrine gland – entire cells are shed by the gland and become part of secretion.
2. Connective Tissue – is a diverse primary tissue type that makes up part of every organ in the body. Functions
- Enclosing and separating other tissues
- Connecting tissues to one another.
- Supporting and moving parts of the body.
- Storing compounds.
- Cushioning and insulating.
- Transporting
- Protecting
TYPES OF IMMUNE CELLS THAT CAN
RESIDE IN CONNECTIVE TISSUE
- FIBROBLAST - They are present in all general connective tissues and usually are the most numerous
- MACROPHAGES - develop from monocytes (a type of white blood cell) - They have an irregular shape and are capable of engulfing bacteria and cellular debris by phagocytosis • Fixed macrophages reside in a particular tissue
- Wandering macrophages- have the ability to move throughout the tissue and gather at sites of infection or inflammation to carry out phagocytosis.
3. PLASMA CELLS - are small cells that develop from a type of white blood cell called a B lymphocyte. For immune response. They are abundant in salivary glands, lymph nodes, spleen, and red bone marrow
vessels, sweat glands, nerves). Thicker than epidermis. Subcutaneous (under the skin) tissue, which is a layer of connective tissue.
Types of Injection Administration
Intradermal Injection – is administered by drawing the skin taut and inserting a small needle at a shallow angle into the dermis; an example is the tuberculin skin test. Subcutaneous Injection – is achieved by pinching the skin to form a “tent” and inserting a short needle into the adipose tissue of the subcutaneous tissue; an example is an insulin injection. Intramuscular Injection – is accomplished by inserting a long needle at a 90-degree angle into the skin into a muscle deep in the subcutaneous tissue.
Skin Color Melanin (black) is the group of pigments primarily responsible for skin, hair, and eye color. Produced by melanocytes (black cells) Albinism is a recessive genetic trait that causes a deficiency or an absence of melanin.
Accessory skin structures – hair, glands, and nails
Physiology of the Integumentary System
- Protection
- Sensation
- Vitamin D Production
- Temperature Regulation
- Excretion
Integumentary System as a Diagnostic Aid
- Cyanosis
- Jaundice
- Rashes and lesions
- Sandpaper texture (skin)
- Spoon-shaped (nails)
Skeletal System
The entire framework of bones and their cartilages, along with ligaments and tendons, constitutes the skeletal system.
Composition
Bone - is composed of several different tissues working together.
OSTEOLOGY - The study of bone structure and the treatment of bone disorders.
Major Functions
- It provides the major SUPPORT for the body.
- Bone PROTECTS internal organs.
- Joints ALLOW/ASSISTANCE IN MOVEMENT between bones.
- Bones store and release MINERALS as needed by the body.
- Bone marrow gives rise to blood cells and platelets.
- Triglyceride storage.
Extracellular Matrix:
Collagen – a tough, ropelike protein.
Proteoglycans – large molecules consisting of many polysaccharides attaching to core proteins; can attract and retain large amounts of water.
Mineral component – gives the bone compression strength which includes calcium & phosphate.
Four Categories/Structure of Bone
- Long Bones – longer than they are wide; includes bones of upper and lower extremities.
Structure of Long Bones
Description
Diaphysis central shaft; compact bone tissue on the outside Epiphysis ends; spongy bone tissue Articular Cartilage
covers the ends of epiphyses; reduces friction
Epiphyseal Plate
site of bone growth; between diaphysis & epiphysis Medullary Cavity
center of diaphysis; spaces are filled with marrow
Red Marrow – location of blood- forming cells; found in most bones in newborns & for adults, mainly in epiphyses of femur & humerus
Yellow Marrow – replaced the red marrow in adults; mostly Periosteum dense connective tissue around the bone’s outer surface Endosteum membrane that lines the medullary cavity
- Short Bones - approximately as wide as they are long; includes bones of wrist and ankles.
- Flat Bones - have a relatively thin, flattened shape; well-suited to provide a strong barrier around soft organs; includes skull bones, ribs, scapula, and sternum.
- Irregular Bones - shapes do not fit readily into the other categories; specialized functions provide protection while
COMPONENT EXTRACELLULAR
MATRIX
Bone – flexible & able to bear weight
Collagen & Minerals
Cartilage – good shock absorber
Collagen & Proteoglycans
Tendons & Ligaments – very tough
Large amounts of Collagen
EPIPHYSEAL ARTERIES - enter the epiphyses of a long bone and supply the red bone marrow and bone tissue of the epiphyses.
TYPES OF OSSIFICATION
Intramembranous Ossification - This occurs within the connective tissue membranes; primarily in skull bones.
Endochondral Ossification – This occurs inside hyaline cartilage; primarily in all bones (except the skull).
Bone Growth This occurs by the deposition of new bone lamellae onto existing bone or other connective tissue.
- Zone of resting cartilage. This layer is nearest the epiphysis and consists of small, scattered chondrocytes.
- Zone of proliferating cartilage. Slightly larger chondrocytes in this zone are arranged like stacks of coins.
- Zone of hypertrophic cartilage. This layer consists of large, maturing chondrocytes arranged in columns.
- Zone of calcified cartilage. The final zone of the epiphyseal plate is only a few cells thick and consists mostly of chondrocytes that are dead because the extracellular matrix around them has calcified.
Appositional Growth – This is a process in which the bone increases in width or diameter.
● Infancy & Youth : Long bones lengthen at the epiphyseal plate and widen by adding more lamella
● End of bone growth (in length ): The epiphyseal plate is replaced by an epiphyseal line.
Bone Remodeling
This is the removal of existing bone by osteoclasts and deposition of new bone by osteoblasts which occurs in all bones.
It is responsible for changes in bone shape, bone repair, adjustment of bone to stress, and calcium ion regulation.
▪ Too much is deposited – bones become thick or develop abnormal spurs or projections that can interfere with normal function.
▪ Too little bone formation / too much bone removal – weakens the bones & makes them susceptible to fracture.
Classification of Bone Fractures
Open Fracture – formerly called compound fracture; occurs when an open wound extends to the site of fracture or when a fragment of bone protrudes through the skin.
Closed Fracture – formerly called simple fracture; occurs when the skin is not perforated.
Complicated Fracture – occurs when the soft tissues around a closed fracture are damaged.
TYPES OF BONE FRACTURE
Incomplete – does not extend completely across the bone
Complete – the bone is broken into at least two fragments
Greenstick Fracture – is almost only
seen in children. Only the outside of the
bone is split.
Hairline Fracture – A very thin crack or
break in the bone.
Communicated Fracture – Complete
break where the bone is in pieces.
Impacted Fracture – Commonly occurs
when falling heights cause the long bone
to become compressed along the long
axis.
Linear Fractures – none branching lines
that are intensely radiolucent.
Transverse Fracture – the break is
across the bone.
Spiral Fracture – Breaks spiral around
the bone. Occurs when a bone is twisted.
Oblique Fractures – Broken at an angle
across the bone and is usually the result
of a sharp-angled blow to the bone.
Dentate - have rough, toothed, broken ends
Stellate - have breakage lines radiating from a central point
BONE REPAIR
During this process, cells move into the damaged area and form a callus, which is replaced by bone.
Hematoma formation : Broken bone causes bleeding and a blood clot forms
Callus formation : A fibrous network forms between two fragments
Callus ossification : Cartilage model forms first then osteoblasts enter the callus and form spongy bone (This continues for 4-6 weeks after injury)
Bone remodeling : Spongy bone is slowly remodeled to form compact and spongy bone.
Bone and Calcium (Ca2+) Homeostasis
Bone is a major storage site for calcium. The movement of calcium in & out of bone helps determine its blood levels.
▪ Calcium moves into bone as osteoblasts build new bones.
▪ Calcium moves out of bone as osteoclasts break down bone.
▪ Calcium homeostasis is maintained by parathyroid hormone (PTH), vitamin D from the skin or diet, and calcitonin.
Muscular System
Composed mainly of muscle tissue, the most abundant tissue of the body & one of the most adaptable.
Major Functions
- Movement of the body
Sarcomeres
The basic structural and functional contractile unit of a skeletal muscle that contains actin and myosin myofilaments.
Z disk - a network of protein fibers that forms a stationary anchor for actin myofilaments to attach; separate one sarcomere from the next
I band - light-staining band that consists of only actin myofilaments; each includes a Z disk and extends toward the center of the sarcomere to the ends of myosin myofilaments
A band - the central dark-staining band where the actin & myosin filaments overlap for some distance; each band extends the length of the myosin filaments within the sarcomere
H zone - smaller, lighter-staining region at the center of each A band; contains only myosin myofilaments
M line - consists of fine protein filaments that anchor the myosin myofilaments in place
Resting Membrane Potential – a state where the cell membranes have a negative charge on the inside relative to the positive charge outside.
This exists because of the following:
✔Higher concentration of K+ on the inside of the cell membrane
✔Higher concentration of Na+ on the outside of the cell membrane
✔Many negatively charged molecules inside the cell
✔The cell membrane is more permeable to K+ than Na+ Action Potential – a brief reversal of the membrane charge that is carried rapidly along the cell membrane.
Depolarization : change in charges where the Na+ channels open causing the sodium ions to enter the inside of the cell membrane (become more positive). This increase in positive charge changes the membrane potential to a value called threshold (weakest stimulus needed to produce a response).
▪ Repolarization : returns the cell to its resting membrane conditions & action potential ends. This occurs due to the exit of K+ from the cell & closing of Na+ channels that stop the sodium movement.
Nerve Supply and Muscle Fiber Stimulation
Motor Neurons – are specialized nerve cells that carry action potentials to skeletal muscles & stimulate to contract.
Motor Unit – a group of muscle fibers that motor neuron stimulates.
Neuromuscular Junction / Synapse – where the neuron and muscle fibers meet; consists of several enlarged axon terminals (presynaptic terminal) resting in indentations of muscle fiber’s sarcolemma (postsynaptic membrane)
Synaptic Vesicle – located in each presynaptic terminal that contains the neurotransmitter called acetylcholine
(ACh) which stimulates or inhibits postsynaptic cells.
Adenosine Triphosphate (ATP) – is a high-energy molecule produced from the energy that is released during the metabolism of food which is used for muscle contraction.
Muscle Twitch – a single contraction of muscle fiber in response to a stimulus and has 3 phases:
▪ Lag Phase / Latent Phase: time between the application of a stimulus and the beginning of contraction
▪ Contraction Phase: time during which the muscle contracts
▪ Relaxation Phase: time during which the muscle relaxes
Two Ways in Increasing the Force of Muscle Contraction
- Summation – individual muscles contract more forcefully through rapid stimulation of muscle fibers preventing relaxation or detachment of cross- bridges
Tetanus : a sustained contraction that occurs when the frequency of stimulation is so rapid that no relaxation occurs.
- Recruitment – more motor units are stimulated which increases the total number of muscle fibers contracting
All or None Law : no in-between in muscle contraction, either the muscle contracts or does not
Fiber Types
Slow-Twitch Fibers
✔ Commonly found in postural muscles ✔ Contract slowly
✔ Fatigue slowly ✔ For long-distance running
✔ Use aerobic respiration ✔ Energy from fat
✔ Dark meat
✔ Red or dark in color due to myoglobin (stores oxygen temporarily) Fast-Twitch Fibers
✔Commonly found in upper limbs ✔ Contract quickly
✔ Fatigue quickly ✔ For sprinting
✔ Use anaerobic respiration ✔ Energy from glycogen
✔ White meat Processes of ATP Derivation
- Aerobic production during most exercise and normal conditions. ▪ Lactate - produced by skeletal muscles all the time, especially during exercise (alternate chemical form of lactic acid)
- Anaerobic production during intensive short-term work.
- Conversion of creatine phosphate to ATP. ▪ Creatine Phosphate – an energy- storage molecule from excess ATP which is broken down quickly to directly synthesize ATP in contracting muscle fibers
- Conversion of 2 ADP to one ATP & one adenosine monophosphate (AMP) during heavy exercise. ▪ This event occurs if the use of ATP is greater than the production – ATP: ADP ratio declines
subdivisions: the somatic nervous system and the autonomic nervous system. Somatic nervous system. The somatic nervous system allows us to consciously, or voluntarily , control our skeletal muscles. Autonomic nervous system. The autonomic nervous system regulates events that are automatic, or involuntary ; this subdivision, commonly called the involuntary nervous system, has two parts: the sympathetic and parasympathetic, which typically bring about opposite effects.
Neuroglia. Neuroglia includes many types of cells that generally support, insulate, and protect the delicate neurons; in addition, each of the different types of neuroglia, also simply called either glial or glial cells, has special functions.
Astrocytes. These are abundant, star- shaped cells that account for nearly half of the neural tissue; astrocytes form a living barrier between the capillaries and neurons and play a role in making exchanges between the two so they could help protect neurons from harmful substances that might be in the blood. Microglia. These are spider-like phagocytes that dispose of debris, including dead brain cells and bacteria.
Ependymal cells. Ependymal cells are glial cells that line the central cavities of the brain and the spinal cord; the beating of their cilia helps to circulate the cerebrospinal fluid that fills those cavities and forms a protective cushion around the CNS. Oligodendrocytes. These are glia that wrap their flat extensions tightly around the nerve fibers, producing fatty insulating coverings called myelin sheaths. Schwann cells. Schwann cells form the myelin sheaths around nerve fibers that are found in the PNS. Satellite cells. Satellite cells act as protective, cushioning cells.
Neurons , also called nerve cells, are highly specialized to transmit messages (nerve impulses) from one part of the body to another.
Cell body. The cell body is the metabolic center of the neuron. Nissl substances called the rough ER and neurofibrils are particularly abundant in the cell body. Processes. The arm-like processes, or fibers, vary in length from microscopic to 3 to 4 feet; Dendrons convey incoming messages toward the cell body Axons generate nerve impulses and typically conduct them away from the cell body. Axon hillock – a cone-like region of the cell body called the axon hillock.
Axon terminals. These terminals contain hundreds of tiny vesicles, or membranous sacs that contain neurotransmitters. Synaptic cleft. Each axon terminal is separated from the next neuron by a tiny gap called the synaptic cleft. Myelin sheaths. a whitish, fatty material; that protects and insulates the fibers and increases the transmission rate of nerve impulses. Nodes of Ranvier. The gap between myelin sheath and Schwann cells
Functional Classification
Sensory neurons (afferent). Neurons that carry impulses from sensory receptors to the CNS; keep us informed about what is happening both inside and outside the body.
Motor neurons (efferent). Neurons that carry impulses from the CNS to the viscera and/or muscles and glands.
Interneurons. The third category of neurons; connects the motor and sensory neurons in neural pathways.
Structural classification Multipolar neuron - several processes Bipolar neurons - neurons with two processes. Unipolar neurons - have a single process emerging from the cell’s body.
Central Nervous System
Brain - the largest and most complex mass of nervous tissue in the body
Parts of the Brain
Cerebrum The most superior part of the brain. Your cerebrum is the part of your brain that starts and manages conscious thoughts; meaning, things that you actively think about or do. 4 Lobes of cerebrum Parietal lobe. The primary somatic sensory area. Occipital lobe. The visual area Temporal lobe. The auditory area Frontal lobe. The primary motor area
Diencephalon. The diencephalon, or interbrain, sits atop the brain stem and is enclosed by the cerebral hemispheres.
The thalamus - is a relay station for sensory impulses passing upward to the sensory cortex.
Hypothalamus - The hypothalamus makes up the floor of the diencephalon; regulating body temperature, water balance, and metabolism.
Mammillary bodies. The mammillary bodies, reflex centers involved in olfaction (the sense of smell)
Epithalamus. Forms the roof of the third ventricle; important parts are the pineal body (part of the
and protected by the meninges; meningeal coverings extend well beyond the end of the spinal cord in the vertebral canal. Spinal nerves. In humans, 31 pairs of spinal nerves arise from the cord and exit from the vertebral column to serve the body area close by.
Cauda equina. The collection of spinal nerves at the inferior end of the vertebral canal is called cauda equina because it looks so much like a horse’s tail.
Gray Matter of the Spinal Cord and Spinal Roots (40% of the brain)
The gray matter of the spinal cord looks like a butterfly or a letter H in cross- section.
Projections. The two posterior projections are the dorsal , or posterior , horns ; the two anterior projections are the ventral , or anterior , horns. Central canal. The gray matter surrounds the central canal of the cord, which contains CSF. Dorsal root ganglion. The cell bodies of sensory neurons, whose fibers enter the cord by the dorsal root , are found in an enlarged area called the dorsal root ganglion; if the dorsal root or its ganglion is
damaged, the sensation from the body area served will be lost. Dorsal horns. The dorsal horns contain interneurons. Ventral horns. The ventral horns of gray matter contain cell bodies of motor neurons of the somatic nervous system, which send their axons out to the ventral root of the cord. Spinal nerves. The dorsal and ventral roots fuse to form the spinal nerves.
White Matter of the Spinal Cord (60% of the brain) Composed of myelinated fiber tracts- some running to higher centers, some traveling from the brain to the cord, and some conducting impulses from one side of the spinal cord to the other.
Regions. Because of the irregular shape of the gray matter, the white matter on each side of the cord is divided into three regions- the dorsal, lateral , and ventra l columns; each of the columns contains a number of fiber tracts made up of axon with the same destination and function. Sensory tracts. Tracts conducting sensory impulses to the brain are sensory, or afferent , tracts. Motor tracts. Those carrying impulses from the brain to skeletal muscles are motor, or efferent , tracts.
Peripheral Nervous System
Consists of nerves and scattered groups of neuronal cell bodies (ganglia) found outside the CNS.
Structure of a Nerve
A nerve is a bundle of neuron fibers found outside the CNS.
Endoneurium. Each fiber is surrounded by a delicate connective tissue sheath, an endoneurium. Perimeurium. Groups of fibers are bound by a coarser connective tissue wrapping, the perineurium, to form fiber bundles or fascicles. Epineurium. Finally, all the fascicles are bound together by a tough fibrous sheath, the epineurium, to form the cordlike nerve. Mixed nerves. Nerves carrying both sensory and motor fibers are called mixed nerves. Sensory nerves. Nerves that carry impulses toward the CNS only are called sensory, or afferent, nerves. Motor nerves. Those that carry only motor fibers are motor, or efferent, nerves.
Cranial Nerves The 12 pairs of cranial nerves primarily serve the head and the neck. Olfactory. Fibers arise from the olfactory receptors in the nasal mucosa and synapse with the
olfactory bulbs; its function is purely sensory, and it carry impulses for the sense of smell. Optic. Fibers arise from the retina of the eye and form the optic nerve; its function is purely sensory and carries impulses for vision. Oculomotor. Fibers run from the midbrain to the eye; it supplies motor fibers to four of the six muscles (superior, inferior, medial rectus, and inferior oblique) that direct the eyeball; to the eyelid; and to the internal eye muscles controlling lens shape and pupil size Trochlear. Fibers run from the midbrain to the eye; it supplies motor fibers for one external eye muscle (superior oblique). Trigeminal. Fibers emerge from the pons and form three divisions that run to the face; it conducts sensory impulses from the skin of the face and mucosa of the nose and mouth; and also contains motor fibers that activate the chewing muscles. Abducens. Fibers leave the pons and run to the eye; it supplies motor fibers to the lateral rectus muscle, which rolls the eye laterally. Facial. Fibers leave the pons and run to the face; it activates the muscles of facial expression and the lacrimal and salivary glands; which carry sensory impulses from the taste buds of the anterior tongue. Vestibulocochlear. fibers run from the equilibrium and hearing receptors of the inner ear to the brain stem; its function is purely sensory; the vestibular branch
