A & P 337 (Module 1)

Fascicle Arrangements (Muscle Fiber Direction)

- Parallel Muscles (Biceps, Abs, Supinator) - Convergent Muscle (Pecs) - Pennate (Unipennate, Bipennate, Multipennate) - Circular (Sphincters)

31 Spinal Nerves and Regions

8 pairs of cervical nerves designated C1 to C8 12 thoracic nerves designated T1 to T12 5 pairs of lumbar nerves designated L1 to L5 5 pairs of sacral nerves designated S1 to S5 1 pair of coccygeal nerves

CNS vs PNS

- central nervous system (CNS) consists of the brain and spinal cord. - peripheral nervous system (PNS) consists of all nervous tissue outside of the brain and spinal cord.

Connective Tissue Basics

- connective tissue cells are dispersed among an extracellular matrix (substances in the space around the cells) of ground substance and protein fibers produced by the cells of that connective tissue. The ground substance is usually a fluid, but it can also be mineralized and solid, as in bones. - connective tissues come in a vast variety of forms, yet they typically have in common three characteristic components: cells, large amounts of ground substance, and protein fibers. The amount and structure of each component correlates with the function of the tissue.

Humoral vs Hormonal vs Neural

- different nutrient levels in blood regulate the production and secretion of hormones - one hormone causes a gland to secrete another hormone - nerve impulse causes a gland to secrete its substance

Myofibrils, Actin, Sacromere

- each muscle fiber contains many myofibrils, and each myofibril runs the entire length of the muscle fiber. Myofibrils contain many myofilaments, which are actin and myosin proteins. The actin and myosin are organized into repetitive groupings, and each unique grouping is called a sarcomere. The sarcomere is the functional unit of the muscle fiber.

Hypertrophy vs Atrophy

- hypertrophy, and ultimately an increased size of the muscle. However, exercise does NOT result in the formation of new muscle fibers. - conversely, a lack of use can result in a decrease in muscle mass, called atrophy.

Subcorticospinal Pathways

- motor pathways running from the brainstem or cerebellum to the spinal cord - help regulate and control the pattern of somatic motor activity through indirect pathways - can excite or inhibit LMNs - may modulate spinal reflexes, regulate muscle tone and posture, or control orienting reflexes to visual or auditory stimuli

Basal Lamina vs Reticular Layer

- superficial layer that restricts movement of proteins and other large molecules from the underlying connective tissue into the epithelium - deep layer that anchors the basement membrane to the underlying connective tissue

Skin Sensory Receptors

- tactile (Meissner) corpuscle, which responds to light touch (papillary dermis, especially in the fingertips and lips) - lamellated (Pacinian) corpuscle, which responds to deep pressure located in the deep dermis, subcutaneous tissue - tactile (Merkel) discs, seen scattered in the stratum basale and superficial papillary layer of the dermis, are light-touch receptors, Tactile cell = epidermis, Tactile disc = Epidermal-dermal junction, mucosal membranes - bulbous (Ruffini) corpuscles found in the dermis and subcutaneous layers are sensitive to deep pressure and skin distortion - root hair plexus wrapped around hair follicles in the dermis and stimulated by light touch or hair movement - free nerve endings located in the deep epidermis and the papillary layer of dermis, cornea, tongue, joint capsules, visceral organs respond to pain and temperature - muscle spindle fibers in line with skeletal muscle fibers and stimulated by contraction and stretch - golgi tendon organs in line with tendons and stimulated by tendon stretch - motor nerves that innervate the arrector pili muscles and glands.

Motor Units and Neuromuscular Junction

- the neuromuscular junction is the site where a motor neuron meets the muscle fiber. Each muscle fiber is innervated by only one motor neuron, but one motor neuron can innervate several skeletal muscle fibers. The group of muscle fibers in a muscle innervated by a single motor neuron is called a motor unit. - small motor unit = one motor neuron supplies a small number of fibers in a muscleSmall motor units permit very fine motor control of the muscle. Examples: muscles that move the eye (extraocular muscles) or muscles of the hand, where a single motor neuron can supply less than ten muscle fibers - large motor unit = one motor neuron supplies a large number of muscle fibers in a muscleLarge motor units are concerned with simple, or "gross" (large), movements.Examples: thigh muscles or back muscles, where a single motor neuron will supply thousands of muscle fibers

All or None Principle

- when a motor neuron is stimulated, all muscle fibers in its motor unit will contract. This is the all-or-none principle. The number of and specific motor units in a muscle recruited to contract at a given time will vary depending on the motion and strength required to complete an action.

Five Functions of Epithelial Tissue

1) Protection - provides the body's first line of protection from physical, chemical, and biological wear and tear. 2) Selective Permeability - the cells of an epithelium act as gatekeepers of the body controlling permeability and allowing selective transfer of materials across a physical barrier. All substances that enter the body must cross an epithelium. Some epithelia often include structural features that allow the selective transport of molecules and ions across their cell membranes. - Diffusion: selective, simple transport of substances through a thin layer of tissue - Absorption (transcellular transport): absorption of substances through the cell, where it is processed to some degree before being released into the blood and/or underlying tissue. This is called transcellular transport because it is going through the cell. 3) Secretion - many epithelial cells are capable of producing and secreting specific chemical compounds onto their apical surfaces. 4) Sensation - specialized epithelia can detect light, taste, sound, smell, and hearing. 5) Surface Parallel Transport - transport of substances across the free surface of the epithelium.

A Group of Neuronal Cell Bodies (CNS vs PNS) vs Bundle of Axons (CNS vs PNS)

A group of neuronal cell bodies CNS = nucleus PNS = ganglion (ganglia is plural) Bundle of axons (fibers) CNS = tract (most common), also fascicle, lemniscus, commissure PNS = nerve

Vertebral Bones

24 Individual Bones or 26 Distinct Bones 7 Cervical 12 Thoracic 5 Lumbar Sacrum (5 Fused Vertebrae) Coccyx (3-4 Fused Vertebrae)

Connective Tissue Proper

A primary cell type of connective tissue proper is the fibroblast, which secretes the ground substance and protein fibers in the extracellular matrix. Three main types of fibers are secreted by fibroblasts: collagen fibers, elastic fibers, and reticular fibers. Collagen fibers - collagen fibers, while flexible, have great tensile strength, resist stretching, and give ligaments and tendons their characteristic resilience and strength. These fibers hold connective tissues together, even during the movement of the body. Elastic Fibers - these fibers contain the protein elastin along. The main property of elastin is that after being stretched or compressed, it will return to its original shape. Reticular Fibers - reticular fibers are found throughout the body, but are most abundant in the reticular tissue of soft organs, such as liver and spleen, where they anchor and provide structural support to the organ while allowing space for blood and cells to move through the structure.

Sebaceous Glands

A sebaceous gland is a type of oil gland found all over the body and helps to lubricate and waterproof the skin and hair. Most sebaceous glands are associated with hair follicles.

Gland

A structure made up of one or more cells modified to synthesize and secrete chemical substances. Most glands consist of groups of epithelial cells, though some cells themselves are considered glands.

Goblet Cell

A unicellular exocrine "gland" interspersed between the columnar or pseudostratified columnar epithelial cells of mucous membranes ((Figure)). Goblet cells secrete mucin, which becomes mucous when mixed with water.

Sweat Glands (Eccrine vs Apocrine)

An eccrine sweat gland is a type of gland that produces a hypotonic sweat for thermoregulation. Coiled glands lying deep in the dermis, with the duct rising to a pore on the skin surface, where the sweat is released. An apocrine sweat gland is usually associated with hair follicles in densely hairy areas, such as armpits and genital regions. Apocrine sweat glands are larger than eccrine sweat glands and lie deeper in the dermis, sometimes even reaching the hypodermis, with the duct normally emptying into the hair follicle.

Anterior Spinal Artery vs Posterior Spinal Arteries

Anterior - single artery that supplies 2/3 of the blood supply to the spinal cord Posterior - two arteries that supply 1/3 of the blood supply to the spinal cord

Loose Connective Tissue

Areolar Connective Tissue - areolar tissue shows little specialization. It contains all the cell types and fibers distributed in a random, web-like fashion. It fills the spaces between muscle fibers, surrounds blood and lymph vessels, and supports organs in the abdominal cavity. Areolar tissue underlies most epithelia, including between our skin and our muscles or bone. (highly vascularized) Adipose Tissue - this tissue consists mostly of fat storage cells, called adipocytes, with little extracellular matrix ((Figure)). A large number of capillaries allow rapid storage and mobilization of lipid ("fat") molecules. The number and type of adipocytes depends on the tissue and location, and vary among individuals in the population. (highly vascularized) Reticular Tissue - this tissue is a mesh-like, supportive framework for soft organs such as lymphatic tissue, the spleen, and the liver ((Figure)). It functions like a scaffolding that gives shape to these organs while also allowing space for blood and cells to pass through it. Reticular cells produce the reticular fibers that form the network onto which other cells attach.

Ascending Pathways vs Descending Pathways

Ascending pathways of nervous system fibers in these columns carry sensory information up to the brain, whereas descending pathways carry motor commands from the brain.

Astrocytes (CNS)

Astrocytes - are the most abundant glial cells in the CNS. They have many processes extending from their main cell body. Those processes extend to interact with neurons and blood vessels. Astrocytes have many functions, most of which serve to support neurons, including: - regulate the environment around neurons and takes up and/or breaks down some neurotransmitters or ions in the fluid surrounding the neurons. - contribute to the blood-brain barrier, a physiological barrier that keeps many substances that circulate in the rest of the body from getting into the central nervous system, restricting what can cross from circulating blood into the CNS. Certain molecules, such as glucose, can pass through, but other molecules cannot (tight junctions). - act like the "connective tissue of the brain, filling spaces and holding things together - form scar tissue of the brain by proliferating and surrounding damaged regions to separate it from the healthy neurons. This protects healthy neurons from chemical cascade that occurs as a result of the damage. - regulate the inflammatory response to damage. - involved in synapse formation and neuronal growth in developing nervous tissue. - propagate calcium signals involved with memory.

Nerve Regeneration in CNS vs PNS

CNS - when nervous cells are damaged in the CNS, astrocytes will cover the damaged areas and ogliodendrocytes will inhibit the regeneration of the nervous cells (Wallerian degeneration) PNS - when nervous cells are damaged in the PNS, Schwann cells will start to rebuild the damaged sections of nervous cells (Axon regeneration)

Dense Connective Tissue

Dense Regular Connective Tissue - fibers are parallel to each other, enhancing tensile strength and resistance to stretching in the direction of the fiber orientations (and only that direction). For example, tendons are made of dense regular connective tissue. Avascular. Dense Irregular Connective Tissue - the direction of collagen fibers is random. This arrangement gives the tissue greater strength in all directions and less strength in one particular direction. The dermis of the skin is an example of dense irregular connective tissue rich in collagen fibers. Elastic Connective Tissue - elastic tissue contains elastin fibers in addition to collagen fibers, which allows the tissue to return to its original length after stretching. This tissue can be found in the ligaments that form the vocal cords and the walls of large blood vessels, for example.

Compare and Contrast Three Muscle Tissue Types

Cardiac Muscle - myocyte shape = small, short, branched - straited? = yes - Voluntary or Involuntary? = voluntary - Location = heart wall - Function = circulate blood - Connected by Intercalated Disks w/ Gap Junctions = Y - Capable of Cell Division to Produce More Cells = N Smooth Muscle - myocyte shape = Small, spindle-shaped (wide in the middle & tapered on each end, somewhat like a football) - straited? = no - Voluntary or Involuntary? = involuntary - Location = walls of many internal organs and passageways (digestive, respiratory, blood vessels, etc.), eye, skin, and more - Function = move food, urine, reproductive secretions through their respective systems. Control the diameter of blood vessels, respiratory tracts, iris. - Connected by Intercalated Disks w/ Gap Junctions = N - Capable of Cell Division to Produce More Cells = Y Skeletal Muscle - myocyte shape = large, long, cylindrical - straited? = yes - Voluntary or Involuntary? = voluntary - Location = muscles acting on the limbs & trunk, muscles of facial expression, external sphincters regulating passage out of the body - Function = movement or stabilization of the skeleton, guard entrances and/or exits for the digestive, respiratory, and urinary systems. Heat production. Protects internal organs. - Connected by Intercalated Disks w/ Gap Junctions = N - Capable of Cell Division to Produce More Cells = N

Structure of Neurons

Cell Body (soma) - the cell body includes most of the cytoplasm, the organelles, and the nucleus. It is the processing or "thinking" part of the neuron. Dendrite - these branches receive most of the input from other neurons and carry it to the cell body. The dendrites are usually highly branched processes, providing locations for other neurons to communicate with the cell body. Axon - neurons typically have one, and only one, axon—a fiber that emerges from the cell body and projects to target cells. It is the axon that propagates the nerve impulse, which is communicated to one or more cells. The single axon can branch repeatedly to communicate with many target cells. That target could be another neuron, a muscle fiber, or a gland. Where the axon emerges from the cell body, there is a special region referred to as the axon hillock. This is a tapering of the cell body toward the axon fiber.

Apical Epithelial Cell Surface Features (Two Types)

Cilia - extensions from the apical surface of the cell that beat in unison to move fluids as well as trapped particles across the surface of the epithelium (surface parallel transport). Microvilli - extensions that serve to increase the surface area of the apical aspect of the cell for absorption. More surface area means more space for substances to contact the apical surface and be absorbed into the cell.

Dorsal Root, Ventral Root, and Dorsal Root Ganglion

Dorsal Root - contain only the axons of sensory neurons carrying information to the CNS from the periphery. Ventral Root - contain only the axons of motor neurons carrying information away from the spinal cord to muscles and glands. Dorsal Root Ganglion - for each nerve is seen as an enlargement of the dorsal root near the spinal nerve, and it it contains the cell bodies for pseudounipolar sensory neurons.

Spinal Column Motor vs Sensory Parts

Dorsal Root - sensory afferent Dorsal Ramus (<) - both sensory and motor Dorsal Column - sensory Dorsal Horn - sensory Ventral Root - motor efferent Ventral Ramus (>) - both sensory and motor Ventral Column - motor Ventral Horn - motor -------------------------------------------------------------- Spinal Nerve - both sensory and motor Lateral Horn - visceral motor (thoracic levels only) Lateral Column - visceral motor (thoracic levels only)

Ependymal Cells (CNS)

Ependymal Cells - these glial cells filter blood to make cerebrospinal fluid (CSF), the fluid that circulates through the CNS. They line each ventricle, the open spaces in the brain, and the cilia on their surface help to move CSF through the CNS.

Nerves Connective Tissue Layers

Epineurium (CT around entire nerve) > Perineurium (CT around individual fascicles) > Endoneurium (CT around an axon)

Where is Epithelial Tissue Located?

Epithelial tissues line all surfaces of the body. This includes the surfaces exposed to the outside world, the surface of organs, and the openings within hollow organs. Epithelium also forms much of the glandular tissue of the body.

Muscle Cells Four Characteristics

Excitability - can respond to a stimulus. Contractility - can contract and shorten the length of the fiber. The contraction of muscle tissue can be under voluntary, or conscious control, or involuntary, unconscious control. Extensibility - can stretch or extend beyond its resting length. Elasticity - can return to its original length when relaxed.

Spinocerebellar Pathways (Dorsal and Ventral)

Function: proprioception and muscle sense information Dorsal: individual muscles Ventral: limb as a whole Receptors: muscle spindles and golgi tendon organs 1st Order Neuron: dorsal root ganglion 2nd Order Neuron: synapse at the level of entry to the spinal cord, ascend ipsilaterally or decussate and then cross back. Decussation: all information stays ipsilateral

General Nervous System Fibers Based on Functions

General somatic sensory: our sense of touch, pressure, pain, temperature, and proprioception General somatic motor: voluntary movement by skeletal muscles General visceral motor: involuntary movement of our cardiac and smooth muscle and secretion from glands General visceral sensory: monitoring and sensing unconscious information primarily coming from our organs and glands

Glial Cells

Glial Cells - or neuroglia, are cells that support neurons. Many glial functions are directed at helping neurons complete their function of communication. There are six different glial cells, with four found in the CNS and two found in the PNS (can divide throughout life and make more).

Gray Matter and White Matter Organization

Gray Matter Horns and White Matter Columns

Hair

Hair is a keratinous filament growing out of the epidermis. It is primarily made of dead, keratinized cells. Strands of hair originate in an epidermal penetration of the dermis called the hair follicle. Hair Root is connected to a smooth muscle called the arrector pili that contracts in response to nerve signals from the sympathetic nervous system, making the external hair shaft "stand up."

CNS White Matter

In the CNS, regions composed primarily of myelinated axons are called white matter

CNS Gray Matter

In the CNS, regions with many cell bodies and dendrites are referred to as gray matter.

Dermis Layers

It contains blood and lymph vessels, nerves, and other structures, such as hair follicles and sweat glands. The dermis comprises two layers of connective tissue that compose an interconnected mesh of elastin and collagenous fibers produced by fibroblasts. Papillary Layer - made of loose, areolar connective tissue, which means the collagen and elastin fibers of this layer form a loose mesh. This superficial layer of the dermis projects into the stratum basale of the epidermis to form finger-like dermal papillae. Reticular Layer - composed of dense, irregular connective tissue. This layer is well vascularized and has a rich sensory and sympathetic nerve supply. Hypodermis - directly below the dermis and consists of well-vascularized, loose, areolar connective tissue and adipose tissue, which functions as a mode of fat storage and provides insulation and cushioning for the integument.

Microalgia (CNS)

Microglia - these glial cells are the smallest and least-abundant in the CNS. They can be considered the immune cells of the brain. White blood cells, which are a primary line of defense in the body, cannot get through the blood brain barrier. Instead, microglia are constantly patrolling the CNS, extending and retracting their processes to inspect the brain and spinal cord tissue. If there is damage to nervous tissue in the CNS, chemicals are sensed by the microglia and draw them to the injury site. The microglia then phagocytize debris from the dead or dying cells and invading microorganisms.

Lumbar Puncture Needle Insertion Site

LP needles are inserted between the pia mater layer and arachnoid mater layer where the CSF is located. spinal cord protective outside layers from innermost to outermost (pia mater then arachnoid mater then dura mater)

Skeletal Muscle Functions

Maintain Posture and Stabilize Joints - contraction allows us to maintain our posture, resist gravity, and adds dynamic stability to our joints (vs. static stability that comes from ligaments, for example). This contraction is occurring even though the muscle isn't actively shortening. Generate Heat - skeletal muscle generates heat as a byproduct of its contraction. Shivering is an involuntary contraction of skeletal muscles in response to perceived lower than normal body temperature. Protect Internal Organs - forms a physical barrier between our internal organs and the outside world (i.e. the muscles of our trunk).

Types of Reflexes

Monosynaptic stretch reflex: In this reflex, when a skeletal muscle is stretched, a muscle spindle receptor is activated. The axon from this receptor structure will cause direct contraction of the muscle. A common example of this reflex is the knee jerk that is elicited by a rubber hammer struck against the patellar ligament in a physical exam. Golgi tendon reflex: In this reflex, lower motor neurons are inhibited in response to too much tension on a muscle, as sensed by a Golgi tendon organ. This prevents excessive tension, such as trying to lift too much weight, in order to protect the muscle and tendon. Polysynaptic withdrawal reflex: When you touch a hot stove, you pull your hand away. Sensory receptors in the skin sense extreme temperature and the early signs of tissue damage. This signal travels along the sensory fiber from the skin, through the dorsal root to the posterior horn, where it synapses on an interneuron. The interneuron then signals a ventral horn motor neuron, which innervates the muscles needed to pull your hand away from the stove. It also inhibits the muscles that would oppose that movement and activates muscles involved in balancing posture while the arm is forcefully withdrawn.

Nervous System vs Endocrine System

Nervous - communication (neurotransmitters released into synaptic cleft) - target (other neurons, muscle cells, and glands) - response time (rapid) - range of effect (localized/specific) - response duration (fast) Endocrine - communication (hormones released into the blood) - target (any cell in the body with a receptor for that hormone) - response time (slow) - range of effect (widespread throughout the body) - response duration (long lasting, minutes to days to weeks)

Oligodendrocytes (CNS)

Oligodendrocytes - these glial cells myelinate axons in the central nervous system. They contain a few processes (far fewer than astrocytes), each extending out from the cell body to myelinate a portion of an axon. One oligodendrocyte will provide the myelin for multiple axon segments, either for the same axon or for separate axons. Myelination will be discussed more later in this module.

Integument Functions

Protection Water regulation Temperature regulation Vitamin D synthesis Sensory perception Excretion by secretion (discussed in lecture) Storage (discussed in lecture) Non-verbal communication (discussed in lecture)

Shapes of Neurons for Classification

Pseudounipolar Neurons - true unipolar cells are only found in invertebrate animals, so the unipolar cells in humans are more appropriately called "pseudo-unipolar" cells. Pseudounipolar cells have an axon that emerges from the cell body, but it splits so that the axon can extend along a very long distance. At one end of the axon are dendrites, and at the other end, the axon forms synaptic connections with a target. Pseudounipolar cells are exclusively sensory neurons and have two unique characteristics. Bipolar Neurons - these neurons have two processes, which extend from each end of the cell body, opposite to each other. One is the axon and one the dendrite. Bipolar cells are not very common. They are found mainly in the olfactory epithelium (where smell stimuli are sensed), and as part of the retina. Multipolar Neuron - multipolar neurons are all of the neurons that are not unipolar or bipolar. They are by far the most common neurons in the body. They have one axon and two or more dendrites (usually many more).

Features of Epithelial Tissue

Regeneration - continuously replace dead or damaged cells with new ones Polarity - basal and apical sides of epithelial cells have different functions partly because of this Avascular - receive nutrients from diffusion or absorption instead of blood supply and there is barely any or no extracellular space between epithelial cells

Satellite Cells (PNS)

Satellite Cells - these glial cells surround the cell bodies of neurons in the PNS, isolating them and protecting them from the surrounding tissue. They provide support, performing similar functions in the periphery as astrocytes do in the CNS.

Schwann Cells (PNS)

Schwann Cells - they myelinate axons in the periphery. Schwann cells are different than oligodendrocytes, in that a Schwann cell wraps its entire self around one part of only one axon segment.

Three Types of Muscle Tissue

Skeletal Muscle Tissue - forms the muscles that move our bones and joints. Skeletal muscle fibers, or muscle cells, are long, cylindrical fibers that span the entire length of a muscle. (can't divide, but satellite cells can generate new skeletal muscle cells) Cardiac Muscle Tissue - is found in the heart. Cardiac muscle fibers, are much smaller and shorter than skeletal muscle fibers, and they are extensively branched. They contain intercalated discs with gap junctions that form communication channels between adjacent cardiomyocytes, allowing cardiac muscle cells to contract in a wave-like pattern so the heart can work as a coordinated pump. Both skeletal and cardiac muscle tissue appears striated, or striped, due to the arrangement of their contractile proteins. (can't divide and can't regenerate) Smooth Muscle Tissue - is named so because the cells do not have striations. They are thousands of times shorter than skeletal muscle fibers. Unlike other muscle tissue, smooth muscle tissue can also divide to produce more cells, a process called hyperplasia. (capable of dividing and generating new smooth muscle cells)

Skeletal Muscle Organization

Skeletal muscle fibers are organized into individual bundles, called fascicles. Each skeletal muscle has three layers of connective tissue that enclose it, provide structure and support to the muscle as a whole, and compartmentalize the muscle fibers within the muscle. Epimysium - a sheath of dense, irregular connective tissue that surrounds each muscle Perimysium - a sheath of connective tissue surrounding each individual fascicle Endomysium - a sheath of connective tissue surrounding each individual muscle fiber

Thin Skin vs Thick Skin

Skin that has four layers of cells is referred to as "thin skin." These layers are the stratum basale, stratum spinosum, stratum granulosum, and stratum corneum from deep to superficial. "Thick skin" is found only on the palms of the hands and the soles of the feet. It has a fifth layer, called the stratum lucidum, located between the stratum corneum and the stratum granulosum.

Three Types of Muscle Fibers

Slow Oxidative (SO) Fibers - these fibers contract relatively slowly. They are aerobic, meaning they primarily use oxygen in the energy-producing process. As a result, they need a greater blood supply to bring oxygen to them. These fibers produce less power, but have greater endurance, meaning they can contract for longer periods of time than other types of fibers. The ability to function for long periods without fatiguing makes them useful in maintaining posture, producing isometric contractions, stabilizing bones and joints, and making small movements that happen often but do not require large amounts of energy. As a result, they are the predominant fiber type used in endurance (aerobic) exercise. Fast Oxidative (FO) Fibers - these are often called intermediate fibers. They have relatively fast contractions, and they fatigue more quickly than slow oxidative fibers. They primarily use oxygen to produce energy, but they can switch to using glucose (anaerobic). These fibers are used primarily for movements, such as walking, that require more energy than postural control but less energy than an explosive movement, such as sprinting. Fast Glycolytic (FG) Fibers - these fibers have fast contractions and primarily use glucose in the energy-producing process, which is located within the muscle. Fast glycolytic fibers are used to produce rapid, forceful contractions to make quick, powerful movements. However, they fatigue more quickly than the other fiber types (anaerobic).

Pseudostratified Columnar Epithelium (Structure, Function, Location)

Structure - a single layer of cells of different shapes and sizes, with only some of the cells reaching the free surface of the tissue. This gives it a stratified appearance despite actually being a single layer of cells. It contains cilia on the apical surface. Function - surface parallel transport (moving substances across the free surface of the epithelium). Also secretion of mucous Location - the cilia function to move substances along the surface of the epithelium primarily in locations without smooth muscle to move the substances through a tract. Example: Trachea

Simple Columnar Epithelium (Structure, Function, Location)

Structure - a single layer of cells that are taller than they are wide. These epithelial cells sometimes have microvilli. Function - absorption & secretion Location - the columnar shape allows ample space for intracellular processing of absorbed substances or production of substances to be secreted. It is located in areas that benefit from this structure-function relationship. Example: Digestive tract

Simple Cuboidal Epithelium

Structure - a single layer of cuboidal-shaped cells, as wide as they are tall. May have microvilli on the surface in some locations. Function - Secretion and Absorption Location - the cuboidal shape allows for some space for intracellular processing of absorbed substances or production of substances to be secreted without being overly-thick. It is located in regions that benefit from this structure-function relationship. Example: Certain glands, kidney tubules

Simple Squamous Epithelium (Structure, Function, Location)

Structure - a single layer of flat, thin cells. Function - allows materials to pass through quickly via simple diffusion or filtration. Location - located in places where we need substances to pass quickly and relatively easily through the epithelium. Example: The alveoli, or air sacs, in our lungs.

Stratified Columnar Epithelium (Structure, Function, Location)

Structure - multiple layers of cells with the most superficial cells being columnar in shape. ***This epithelium is rare, and we will not as you about it on an exam. Function - protection and secretion Location - male urethra, some glands

Stratified Cuboidal Epithelium (Structure, Function, Location)

Structure - multiple layers of cells with the most superficial cells being cuboidal in shape. ***This epithelium is rare, and we will not ask you about it on an exam. Function - Protection Location - found in some glands

Stratified Squamous Epithelium (Structure, Function, Location)

Structure - multiple layers of flat, thin cells. Cells at the basal surface may be thicker, more cuboidal in shape, but they flatten as they reach the apical surface. Function - Protection Location - more layers means more layers to lose before damage reaches the underlying tissue. Therefore, it is found in places exposed to physical and chemical wear and tear. Example: Skin (keratinized epithelium, keratin is found in the cells in the superficial layers), esophagus (non-keratinized)

Transitional Epithelium (Structure, Function, Location)

Structure - special epithelium with layers of epithelial cells that stretch when the organ is distended. Function - allows urinary organs to expand and stretch, such as when the bladder fills with urine. Location - bladder, ureters, urethra

Five Function of Connective Tissues

Supporting and Connective Tissues - connective tissues support and connect other tissues; from the connective tissue sheath that surrounds muscle cells, to the tendons that attach muscles to bones, and to the skeleton that supports the positions of the body. Protection - connective tissues provide cushioning as well as bony protection of organs. Defense - specialized cells in connective tissue defend the body from microorganisms that enter the body. Transport - transport of fluid, nutrients, waste, and chemical messengers is ensured by specialized fluid connective tissues, such as blood and lymph. Energy Storage - adipose cells store surplus energy in the form of fat and contribute to the thermal insulation of the body.

Spinocerebellar Pathway (Ascending/Sensory Pathway)

The first order neuron begins like the other sensory pathways, with an axon entering the spinal nerve, then the dorsal root, with a cell body in the dorsal root ganglion. It then enters the posterior horn and synapses there. From there, all we want you to know is that a portion of this pathway stays ipsilateral for its entire path, while the other portion of the pathway decussates at the level it enters the spinal cord and then crosses back over to the side it originated from in the brainstem.

Emergence Location of 31 Spinal Nerves

The spinal nerves are numbered from the superior to inferior positions, and each emerges from the vertebral column through the intervertebral foramen at its level. The first nerve, C1, emerges between the first cervical vertebra and the occipital bone. C2 through C7 emerge superior to the vertebrae of the same number, but C8 emerges between the seventh cervical vertebra and the first thoracic vertebra. For the thoracic and lumbar nerves, each one emerges inferior to the vertebra of the same number. The sacral nerves emerge from the sacral foramina along the length of that unique vertebra.

Four Types of Junctions

Tight Junction - holds cells together so there is no extracellular space between them. Tight junctions prevent substances from moving between the cells, instead forcing them to go through the cells. This enables the epithelia to act as a selective barrier. Adhering Junction (adherens) - acts like a belt holding the epithelial cells together for support and stability of the tissue. Desmosome - holds cells together like a push button on a jacket to provide support and stability of the tissue. Gap Junction (cell to cell communication) - forms an intercellular passageway between the membranes of adjacent cells to facilitate the movement of small molecules and ions between the cytoplasm of adjacent cells. These junctions allow electrical and metabolic coupling of adjacent cells, which coordinates function in large groups of cells.

Descending Motor Neurons

Upper Motor Neurons: These neurons originate in the brain and descend through the spinal cord until they reach the level that the pathway will exit the spinal cord. At that point they enter the anterior (ventral) horn and synapse with the lower motor neuron. The upper motor neuron can either excite or inhibit the lower motor neuron, meaning it can cause the lower motor neuron to send a signal to the muscle to contract or it can prevent the lower motor neuron from sending that signal. Lower Motor Neurons: The lower motor neurons originate in the anterior (ventral) horn of the spinal cord. The axon travels through the ventral root to join the spinal nerve on its way out to a skeletal muscle. The axon is relatively long because it needs to reach muscles in the periphery of the body. Some axons are a meter in length, such as the lumbar motor neurons that innervate muscles in the feet. The axons will also branch to innervate multiple muscle fibers forming a motor unit, as discussed in Module 2. If a lower motor neuron is excited by an upper motor neuron, the muscle will contract. (The lower motor neuron cannot inhibit the muscle.)

Neoplasia

abnormal new cell growth and reproduction due to loss of regulation

Unencapsulated vs Capsulated Tactile Receptors

are not wrapped in myelin or a modified myelin sheath. These include: Free Nerve Endings Tactile (Merkel) discs Root Hair Plexus are wrapped in a modified myelin sheath. These receptors include: Tactile (Meissner) corpuscles Lamellated (Pacinian) corpuscles Bulbous (Ruffini) corpuscles

Necrosis vs Apoptosis

bad cell death vs good cell death

Conus Medularis

bottom end of spinal cord at L1

Dorsal Column-Medial Lemniscus (DCML) (Ascending/Sensory Pathway)

carries information about fine, discriminative touch and light pressure. It begins with the sensory axon carrying information from receptors in the periphery through the spinal nerve and dorsal root. The first order neuron in this pathway has a cell body in the dorsal root ganglion. The axons of the first order neuron enter the dorsal column of white matter in the spinal cord. The second order neuron starts after decussate occurs in the brain stem.

Chonrocytes and Perichondrium

chondrocytes or cartilage cells, and the spaces they occupy are called lacunae (singular = lacuna). A layer of dense irregular connective tissue, the perichondrium, encapsulates the cartilage. Cartilaginous tissue is avascular.

Sharpey's Fibers

collagen fibers penetrating deep into cortical bone to securing in place

Cauda Equina

collection of spinal nerves below the end of the spinal cord

Monosynaptic vs Polysynaptic

direct communication between sensory and motor neuron interneuron facilitates between sensory and motor neuron

Spinal Nerve, Dorsal Ramus, Ventral Ramus

dorsal and ventral roots merge a short distance from the spinal cord to form the spinal nerve spinal nerve then branches into a dorsal ramus, which carries both sensory and motor information from or to the posterior trunk, and the ventral ramus, which carries both sensory and motor information from or to the extremities and anterior trunk.

Polysnaptic Withdrawal Reflex

ex: touching something hot interneurons receive the sensory information and direct flexor muscles to contract and extensor muscles are also inhibited so that the traumatized body part can be quickly withdrawn

Corticospinal Tract (Descending Pathway)

execute and control voluntary motor activity Decussate in the brain stem then synapse with lower motor neuron in the anterior horn but stay ipsilateral after the initial brain stem decussate (in the lateral column). (upper and lower motor neurons because it's a descending neuron)

Proprioceptors

location: skeletal muscle (muscle spindles) tendons (golgi tendon organs) joints (free nerve endings) function: - monitor tension, pressure, and movement at the joint - send input on body movements to the CNS - your sense of body position results from the integration of this information with sensory information from the internal ear

Carcinoma vs Adenocarcinoma

malignant tumor of the epithelium malignant tumor from glandular epithelial cells

Patellar Tendon Reflex

muscle spindle is the receptor for the patellar tendon reflex) (muscle spindles are activated when too much stretch is being picked up and it causes contraction

Nails

nail bed is a specialized structure of the epidermis found at the tips of our fingers and toes. The nail body is formed on the nail bed and protects the tips of our fingers and toes as they are the farthest extremities and the parts of the body that experience the maximum mechanical stress.

Neurons

neurons, or nerve cells, transmit information through the body via electrochemical signals. There are many neurons in the nervous system—a number in the trillions. The synapse is the gap between two neurons, or between a neuron and its target, a muscle or a gland, across which the impulse is transmitted by chemical compounds known as neurotransmitters.

Metaplasia

normal epithelia from one area replaced by another form of epithelia not typical for that region (smoking trachea cells type switch and makes removing mucus harder without cilia on )

Lateral Horn

only found in the thoracic region (and less prominent in the very upper lumbar region), is the central component of the sympathetic division of the autonomic nervous system

Reflex Arc

rapid, automatic, involuntary reactions of muscle to a stimuli - ipsilateral both the receptor and effector are on the same side - contralateral the receptor and effector are on opposite sides

Golgi Tendon Reflex

receptor is the golgi tendon organ located within tendons, and it prevents us from damaging our muscles and tendons from by causing relaxation (polysynaptic reflex)

Dorsal or Posterior Horn

responsible for sensory processing

Ventral or Anterior Horn

sends out motor signals to the skeletal muscles

Spinal Cord Anatomy

spinal cord is located in the vertebral foramen at the center of the vertebral column. The central canal is located in the center of the spinal cord and contains cerebrospinal fluid. The spinal cord is also surrounded by cerebrospinal fluid, which provides nourishment and protection, as well as connective tissue layers called the meninges that also provide additional protection.

Epidermis Layers

stratum basale - is the deepest epidermal layer and attaches the epidermis to the basal lamina, below which lie the layers of the dermis. The cells in the stratum basale bond to the dermis via intertwining collagen fibers referred to as the basement membrane. A finger-like projection or fold, known as the dermal papilla (plural = dermal papillae), is found in the superficial portion of the dermis. Two other cell types are found dispersed among the basal cells in the stratum basale. The first is a tactile (Merkel) cell responsible for stimulating sensory nerves that the brain perceives as touch. These cells are especially abundant on the surfaces of the hands and feet. The second is a melanocyte, a cell that produces the pigment melanin. Melanin gives hair and skin its color and helps protect the epidermis' living cells from ultraviolet (UV) radiation damage. stratum spinosum - is spiny due to the protruding cell processes that join the cells via a structure called a desmosome. Interspersed among the keratinocytes of this layer are dendritic (Langerhans) cells, which function as macrophages by engulfing bacteria, foreign particles, and damaged cells that occur in this layer. stratum granulosum - has a grainy appearance due to further changes to the keratinocytes as they are pushed from the stratum spinosum. The cells (three to five layers deep) become flattened in this layer. Their cell membranes thicken, and they generate large amounts of the proteins keratin, which is fibrous, and keratohyalin, which accumulates lamellar granules within the cells. stratum lucidum - is a smooth, seemingly translucent layer of the epidermis located just above the stratum granulosum and below the stratum corneum. This thin layer of cells is found only in the thick skin of the palms, soles, and digits. The keratinocytes that compose the stratum lucidum are dead and flattened. These cells are densely packed, which gives these cells their transparent (i.e., lucid) appearance and provides a water barrier. stratum corneum - the most superficial layer of the epidermis and is exposed to the outside environment. There are usually 15 to 30 layers of dead cells in the stratum corneum. This dry, dead layer helps prevent the penetration of microbes and the dehydration of underlying tissues and provides mechanical protection against abrasion for the more delicate, underlying layers.

Anterolateral System (Ascending/Sensory Pathway)

the anterolateral system deals with pain, temperature, crude touch, deep pressure. It begins with neurons that travel through the spinal nerve and dorsal root, with a cell body in the dorsal root ganglion. These neurons extend their axons to the dorsal horn, where they synapse with the second neuron in their respective pathway before traveling up the dorsal column. Axons from these second neurons then decussate within the spinal cord at (or near) the level that they enter. From there they ascend to the brain.

Keratinocyte and Keratin

the cells in all of the layers except the stratum basale are called keratinocytes. A keratinocyte is a cell that manufactures and stores the protein keratin. Keratin is an intracellular fibrous protein that gives hair, nails, and skin their hardness and water-resistant properties. The keratinocytes in the stratum corneum are dead and regularly slough away, being replaced by cells from the deeper layers.

Decussate

to cross over to the other side of the brain

Spinal Cord Enlargements

two portions of the spinal cord that have a larger diameter in order to house more cell bodies for more neurons that will go out to innervate specific parts of the body. The cervical enlargement houses neurons that will innervate the muscles of the upper extremities, while the lumbar enlargement will innervate the muscles of the lower extremity. The cervical enlargement is particularly large because there is greater control over the fine musculature of the upper limbs, particularly of the fingers. The lumbar enlargement is not as significant in appearance because there is less fine motor control of the lower limbs.