A & P I Exam 2 Lecture Cards

Front 1

The Tissue:

Back 1

A group of like cells
--Groups increase efficiency of work, cell/tissues have differing capabilities
--Each type of tissue has special function, location is chosen by its capability/function
--Tissues are used to make organs
--All adult tissues come from Ectoderm, Endoderm and Mesoderm

Front 2

Embryological Tissue-

Back 2

Makes up 4 adult tissue types
--Consists of 3 embryological germ layers

*ECTODERM: 1st layer- develps during first week after conception >Weights down embryo and ensures one side is determined as down
*ENDODERM- 2nd layer- develops during 2nd week and comes from ectoderm
*MESODERM- 3rd layer- develops during 2nd week and comes from ectoderm

At 4th week, 3 tissues types folds- placing ECTODERM on outside, MESODERM in middle, and ENDODERM on outside. *This determines organ set-up

Epithelial- Ectoderm and Endoderm
Connective Tissue- Mesoderm
Muscle Tissue- Mesoderm
Nerve Tissue- Ectoderm

Front 3

Epithelial Tissue-

Back 3

Found on the surface of the body (btw body and outside world)
--Cells are very tightly packed (no spaces), avascular (zero blood supply) get oxygen from CT, top layer is dead!

--Layers: Single layer- Simple (absorb and/or secrete, so protect); More than one layer- Stratified (only protect)

--3 Major Shapes: Squamous- Flat; Cubodial- cube-like; Columnar- Tall, column-shaped
--Below Epithelial and above CT is a Basement Membrane (chemical layer) that holds the two layers together
--Polarized- one side faces outside world, one side faces inside

Front 4

Simple Squamous-

Back 4

Description: Single layer, flat cells

Function: Absorption and Secretion

Location: found in protected places
i.e. aveoli of lung (airsacs), lining inside blood vessels (large and small)

Front 5

Stratified Squamous-

Back 5

Description: multiple layers; flat cells, lower layer is cube-like, flattening happens as cells are pushed up

Function: Protection only (best) more layers, more protection

Location: i.e. skin

*Keratinized- skin (thick,layer of keratin on top of cells)
*Non-Keratinized- mouth, esophagus, lining, just inside, vaginal & anal canal

Both VERY Protective, keratinized most protective

Front 6

Simple Cubodial-

Back 6

Description: Single layer, cube-like cells

Function: secretion/absorption (almost every secretion comes from these cells, greater volume of organelles), good gland cells/tissues

Location: i.e.renal tubes, and glands, makes up many ducts & tubes (i.e. kidney)

Front 7

Stratified Cubodial-

Back 7

Description: multiple layers, cube-like cells

Function: protection only

Location: i.e. lining of major ducts (In large sweat glands)

*Very little in body

Front 8

Simple Columnar-

Back 8

Description: single layer, tall cells; has ability to have many accessories (variable)
*Has microvilli (give surface area), in respiratory cells, has cilia to move mucous;
Has near, a Goblet Cell- produces mucous

Function: good with protection and secretion (stomach, large intestine, GI Tracts), some absorption

Location: 20 ft in body
i.e.lining of GI tract, genital tract, lower respiratory traact;

*Height makes it not as good at absorption (fairly good)

Front 9

Stratified Columnar-

Back 9

Description: Multiple layers, tall cells

Function: protection only

Location: i.e. mammary ducts, urethra (limited)

*Less common than stratified cubodial

Front 10

Pseudostratified-

Back 10

Description: Columnar and goblet cells

Function: protection and mucus secretion, gives protection of stratified and the cilia and goblet cells all in one tissue

Location: i.e. Bronchial tubes, found in upper trachea, upper bronchial system, and in lungs

Front 11

Transtional (cell type)-

Back 11

Description: Multiple layers, round to flat cells, elastic cells

Function: protection and stretching, stratified cells with flexible cytoskeleton; when bladder is empty, cells look stratified cubodial, when bladder is full, cells look stratified squamous

Location: i.e. urether (parts) and urinary bladder

Front 12

Connective Tissue (CT)- General-

Back 12

Used to hold or connect the body parts together by extracellular matrix (can be strong and rigid)
--has a lot of space btw CT cells
--has 3 major parts:
*CELLS- fibroblasts- make CT, by making protein fibers and extracellular matrix; also has WBC's >Primary Cell- very active chem cell (star shaped w/dark oval nucleus), can migrate thru most CT

*PROTEINS- fibers are arranged in different ways in different CT, long, stringy-like:
--Collagen- strong and thick, can be woven to make thicker, same tensile strenght as stainless steel, over time become less resilent
--Elastin- elastic fibers, makes up external ear, in the dermis (allows skin tone), stop making in 40's or 50's, as you get older, causing sagging skin
--Reticular- strong (as collagen) and very thin, used for strength with little space, can be interconnected but not woven,

*MATRIX- extracellular material that cell and fibers are in; glue that hold everything together; contains polysacc and proteins; typically a gel but can sometimes be solid (cartilage or bone) or fluid (blood)

Categorized by: >CT Proper- Loose CT and Dense >Specialized CT- Rigid CT, and Liquid CT

Front 13

3 types of Loose CT-

Back 13

Areolar CT
Adipose
Reticular tissue

Front 14

Areolar CT-

Back 14

Description: loose arrangement of fibers and cells, very vascular- supplies oxygen and nutrients to epithelial tissue

Function: holds epithelium tissues to body (provides strength); >1st battle ground (where bacteria is attacked by WBC's); >

Location: i.e. just inferior to most epithelium (right beneath, except gland tissue); > gland tissue is supported by reticular tissue

Front 15

Adipose Tissue (fat)-

Back 15

Description: collection of fibers and adipocytes (fat cells); large, round cells (fat cells)

Function: storage of vast amounts of lipids, mechanical cushion and thermal warmth; 2 types: Yellow fat: standard fat;
Brown fat (common in infants, used to generate heat; in adults, limited to btw shoulder blades) very vascular

Location: i.e. Mainly hypodermis

Front 16

Reticular Tissues-

Back 16

Description: collection of cells and reticular fibers; very vascular (provides blood and moves lipids (adipose)

Function: support gland cells (stroma); used where there are space problems (small, thin, compact; just enough strength

Location: i.e. liver plus other glands; only in gland tissue, spleen and liver

Front 17

Types of Dense CT-

Back 17

Dense Regular

Dense Irregular

Elastic Tissue

Front 18

Dense Regular CT-

Back 18

Description: many/thick parallel fibers of collagen; Regular = Parallel; large concentration of parallel collagen fibers;

Function: strength to hold structures together; Very Thick, broad fibers; strong in direction of fibers;

Location: i.e. makes up Ligaments and Tendons
>Ligament- connects bone-to-bone
>Tendon- connects muscle-to-bone
*very little side-to-side strength

Front 19

Dense Irregular CT-

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Description: many/thick unparallel fibers of collagen; Irregular=unparallel; fibers going any way, not as strong as regular

Function: same as above

Location: i.e. dermis & dura; in skin, underneath areolar tissue providing strength to dermis

Front 20

Elastic Tissue-

Back 20

Description: many/thick parallel fibers of elastin; one one elastic tissue

Function: rubber band like action on structure

Location: i.e. aorta & elastic ligaments; back of the neck (helps raise vertebrae, not a lot in body

Front 21

Types of Special CT-

Back 21

Cartilage (chondroblast)- produce collagen (while making, get trapped inside and become chondrocytes) and elastin, makes matrix solid;

Rigid CT:
hyaline cartilage
elastic cartilage
fibrocartilage
bone tissue

Liquid CT:
blood tissue

Front 22

Hyaline Cartilage-

Back 22

Description: plastic but rigid matrix; very smooth, white surface (end of bones), not a lot of protein fibers

Function: rigid tissue, at the end of bones (reduce friction)

Location: i.e. joint surfaces, btw bones, end of nose

Front 23

Elastic Cartilage-

Back 23

Description: plastic but rigid matrix with elastic fibers; not as smooth

Function: rigid but elastic

Location: i.e. external ear (connects middle ear to throat)

Front 24

Fibrocartilage-

Back 24

Description: plastic but rigid matrix with collagen fibers; a lot of cartilage

Function: rigid & very strong, resilent

Location: i.e. Vertebral discs, in tramatic joint (discs, knee...)

Front 25

Bone Tissue-

Back 25

Description: Ca/protein matrix; 50% bone weight Ca salts, 50% organic proteins; Ca salts bond to protein matrix, making strong and rigid; also laminated to help in rigidity adn strength; Primary cell: osteoblast

Function: very rigid & strong, no absorption, very vascular

Location: i.e. tibial, etc.; entire skeletal system

Front 26

Blood Tissue-

Back 26

Description: liquid matrix & blood cells; blood cells from connective tissues; 3 types: RBC, WBC, platelets, plasma (liquid); 92% of plasma- water

Function: transport within body

Location: i.e. blood

Front 27

Muscle Tissues-

Back 27

Tissues that are able to contract and are excitable
--Cause motion to the body and its parts
--From mesoderm cells
--Has tensile strength and collagen and is elastic, allowing joints to extend and change without tearing

>Skeletal muscle is VOLUNTARY
>Cardiac and smooth muscle is INVOLUNTARY

Front 28

Types of Muscle Tissue-

Back 28

Skeletal Muscle

Cardiac Muscle

Smooth Muscle

Front 29

Skeletal Muscle-

Back 29

Description: most abundant muscle tissue in body, involved with skeleton; multi-nuclei (due to length, allows for making of proteins throughout cell) with Straitions (lines in cell, due to mysin and actin); to move joint, muscle contracts; extrememly long muscles; contains mostly actin and mysin; VOLUNTARY- fast to contractand strong in contraction, can fatigue fast

Function: motions of skeleton, Fusiform (sp)- arranged in actin and mysin bundles help with contraction,

Location: i.e. attached to bones, cell bunched together to make muscles in body

Front 30

Cardiac Muscle-

Back 30

Description: single nuclei (center) with straitions; small, short cells, like rectangles end-to-end; INVOLUNTARY; not as fast or as strong in contraction; doesn't fatigue easily

Function: pumping blood

Location: i.e. wall of heart

Front 31

Smooth Muscle-

Back 31

Description: single nuclei without striations; does have mysin and actin in low concentration; INVOLUNTARY; weak in contraction, has fusiform (sp); great endurance, slow contraction, slow muscle

Function: within walls of organs

Location: i.e. stomach, etc. (lines all internal organs, tubes and sacs); lines organs with motion (i.e. arteries)

Front 32

Nerve Tissue-

Back 32

From ECTODERM
Active nerve cell- neuron
--able to create an electrical signal and transmit it over long distances in the body
--electrical signal created by movement of Na/K ions across cell surface channels
--Nerve tissue provides sensory and motor function for the body

Front 33

Skin (general)-

Back 33

Integementary System
Outer covering of body
--largest organ
--primary function- protects body from outer environment
--helps in temperature regulation and provides an important sensory network
--divides into 3 levels with 4 different tissues

Front 34

Levels of Skin-

Back 34

Epidermis

Dermis

Hypodermis

Front 35

Epidermis (general)-

Back 35

Surface layer
Layer of Keratizated Stratified Squamous
> most protective, thickest layer, solely for barrier purposes
--contains many layers or Strata

Function: environmental protective layer of skin

Front 36

Dermis-

Back 36

Middle layer of skin
Provides strength, blood (epidermis), nerve sensation and innovation to skin (touch, temperature) and brain; has hair, follicles and glands
>Sweat glands allows temp control, by evaporation
Has 2 CT sub layers:
--Papillary region- UPPER (1/3)- just under epithelial tissue; very vascular; Areolar CT
--Reticular layer- LOWER (2/3)- thick, collagen fibers; vascular; Dense Irregular CT

Function:
*center skin layer, contains blood vessels to supply oxygen/nutrients for epidermis
*contains nerve endings to provide a sensory network
*houses all accessory structures of skin:

1. hair follicles, 2. sebacceous glands, 3. sweat glands

Front 37

Hypodermis-

Back 37

(Subcutaneous layer)- Deepest layer

--made of Adipose CT
--very vascular

Function: stores lipids and provides thermal insulation and mechanical cushioning

Front 38

Layers of the Epidermis-

Back 38

Stratum Basale

Stratum Spinous

Stratum Granulosum

Stratum Lucidum

Stratum Corneum

*many layers of epithelial cells, arranged in strata
*about 40% is dead
*Epidermal Ridges hold epidermis tightly to dermis

Front 39

Stratum Basale-

Back 39

Lowest most layer, just above dermis, directly on basement membrane, near blood supply
--takes about 28 days to travel from this layer to the surface of skin
--where tissue undergoes mitosis (daughter cell near basement membrane stays in place, the other is pushed into next layer), responsible for growth of epidermis
--cells are more cube-like
--has mylanocytes (skin color cells)
--rarely have nerve endings
--

Front 40

Stratum Spinous-

Back 40

Second lowest layer
--8-10 cells layers thick
--where cells will live out their lives
--cells produce keratin during this time, sometime called kerocytes; make more keratin as they get closer to surface
--as cells near top of this layer, cells begin to die due to low levels of oxygen

Front 41

Stratum Granulosum-

Back 41

Third layer from top
--3-5 cell layers thick
--ALL cells are DEAD
--cells be become granular, granules all over cell (from decomposition of cell
--near top of this layer, DNA starts to come apart

Front 42

Stratum Lucidum-

Back 42

Second from top layer
--ONLY found on the palms and soles of feet
--Thin layer, 3-5 cells thick
--very dense, pure keratin
--under Stratum Corneum

Front 43

Stratum Corneum-

Back 43

Top Layer
--thick Layer, 25-30 cells layers thick
--cells have decomposed, only thing left is keratin, which takes shape of cell
--layer is made completely of keratin

Front 44

Skin Color-

Back 44

Protects against UV radiation, more melanin (darker skin), more UV protection

Combination of 3 factors
>Melanin- brown dye that stains the epidermal cell membranes
*produced by the melanocyte, amount of melanin released is determined by genetics, hormones and environmental factors (sunlight); sunburn: inflammation

>Carotene- yellow/orange pigment, precursor of Vit A, some ethic groups store Vit A

>Blood in Dermis- hemoglobin will cause red or blue color; deals with venous and arterial blood, major contributor of color to skin

Front 45

Hair-

Back 45

Accessory Structure
--found on the surface of the body except palms, soles and parts of digits
--made of pure very compressed keratin, which grows from the hair follicle
--used for thermal insolation, scalp hair can retain 10% body heat
--hair shafts have a predetermined lenght, after a certain length, hair starts to denature and breaks/splits

Front 46

Skin Glands-

Back 46

Accessory Structure
Sabaceous Glands- associated with hair follicles and makes oily chemical (sebum) that helps waterproof hair, attached to upper part of every hair follicle; designed to keep you dry

Sweat Gland- produces perspiration, used for cooling
--2 major types:

1). Eccrine S.G.- more wide spread over skin; produces watery solution that is released from pores, which is used to help cool skin

2). Apocrine S.G.- mostly in axilla, grion and areolae of breasts; liquid released contains more lipids and proteins and is released thru hair follicles, and start after puberty

Front 47

Hair Color-

Back 47

Black hair- melanin only, dark hair

Blond hair- melanin + iron (Fe)

Red hair- melanin + sulfur (S)

Grey hair- accumulation of air bubbles and no pigment

Front 48

Nail-

Back 48

Accessory Structure
--used as tools (claws)
--extremely compressed keratin on the distal ends of the digits (hands and feet);
--nail is actually nail plate and lies over the nail bed;
--nail grows from proximal to distal from nail matrix, under skin proximal to nail plate
--no melanocytes
--toe nails , developed in in evolution, have not gotten rid, but no real use to humans

Front 49

Skin Disorders-
Burns-

Back 49

Skin Burns: common, classified by the depth of the thermal damage (thickness)

*1st degree- only epidermal damage (redness of skin); mildest; PARTIAL thickness; area is bright red

*2nd degree- PARTIAL thickness; extensive damage to epidermis and portion of dermis damaged; later there is blister formation, bringing fluids to site, providing protection

*3rd degree-FULL Thickness, epidermis and most of dermis are gone, including accessory structures and possibility of hypodermis can be gone too; can be less painful, no nerve endings; key is reduce infection, then fix skin

*1st & 2nd degree- partial thickness*
*3rd degree- full thickness*

Front 50

Skin Disorders-
Cancers-

Back 50

All are due (today) to chronic injury of skin (sunlight)
--common in people with light skin and outside jobs (sun exposure)

Basal Cell Cancer- most common, least fatal; small black ulcer; slow growing, non-invasive, only destroys local tissue; grows upward; common on face (year-round sun)

Squamous Cell- little less common; more invasive; can be a low-flat scaly lesion, low shallow ulcer; grows up

Malignant melanomas- from melanoctyes; least common, most fatal; common in pigmented lesion- moles, frackel, beauty marks; can change shape, size, color;
-oval > texas shaped
-dark > many colors
grows up into epidermis and down in dermis giving blood and lymph channels

Front 51

Bone Tissue-

Back 51

A specialized form of CT, strong and rigid
--50% Ca salts and 50% protein
*Calcium salt- hydroxyapatie
--206 bones in human body

*Ca salt- strong as sheet rock, protein strong as stainless steel

Front 52

Types of Bone-

Back 52

Long Bones- longer than it is wide (i.e. fumur, tibia, bones in palm)
Short Bone- cube-like bone (i.e. carpal bones)
Flat Bone- flat with 2 parallel plates of compact bone (i.e. sternum, breast bones, skull bones)
Irregular Bones- does not fit into other types
Seamoid Bones- oval and seed-shape bones; 6 in the body, used like a pulley, involved w/ligaments and tendons; biggest seamoid- knee cap
--Seamoids- patella, knee bones, seamoid bones

Front 53

Parts of the Long Bone-

Back 53

Articular Cartilage- hyaline cartilage that covers the ends of the epiphysis

Epiphysis- rounded end or head of the bone; articulates w/ bone before it

Metaphysis- taped part or neck that goes between head & shaft

Diaphysis- long, narrow shaft of the bone, lenght of bone
**Inside shaft- medullary cavity and is coated with Endosteum (CT) (contains nerves, blood vessels and Osteoblasts); bone marrow- in shaft, yellow (fat tissue) or red (RBC)

Endosteum- lives inside marrow canal, only has blood vessels, base cells, some nerve endings, no fibrous layer
*Long bones haave yellow bone marrow
*In adults, in sternum, ribs, and pelvic bones red bone marrow

PERIOSTEUM- double CT layer, covers the outside of the bone (360 ), except where articular cartilage is; very important for health of bone
**Inner layer- OSTEOGENIC or Cellular layer- has nerve endings, blood vessles and osteoblasts (bone cells)
**Outer layer- Dense Irregular CT- blood vessels go to surface of bone, supplies blood to outer half of compact bone; goes thru cellular layer and holds periosteum to bone

Front 54

Periosteum-

Back 54

Double CT layer, covers the outside of the bone (360 ), except where articular cartilage is; very important for health of bone

*Inner layer- OSTEOGENIC or Cellular layer- has nerve endings, blood vessles and osteoblasts (bone cells)

*Outer layer- Dense Irregular CT- blood vessels go to surface of bone, supplies blood to outer half of compact bone;
--includes cortal bone- outer rim of bone, where all the strength of bone is located
--provides bone cells that will consistently repair bones over time
--provides sensativity to bone, due to lack of nerv endings

Front 55

Bone Cells-

Back 55

OSTEOGENIC- stem cells; found in periosteum and endosteum; help in repair or replacement of bone stems cells; turn into osteoblast when there is need for repair

OSTEOBLAST- cells that produce bone tissue by making protein matrix; produces osteoid matrix (foundation of bone); makes/"lays down" new bone and gets trapped making new bone

OSTEOCYTES- once trapped during bone formation, they become the inside of bone tissue (inside lacunae); connect neighboring osteocytes by canalicili, allowing the transport of nutrients; when killed, they release cytoplasm which signals bone reabsorption

OSTEOCLASTS- made from WBC Monocytes, reabsorb dead bone tissue; leaving behind a chemical trail that signals new osteoblasts to make new bone tissue

Front 56

2 types of Bone-

Back 56

Compact Bone

Spongy Bone

Front 57

Compact Bone-

Back 57

Dense and Cortical Bone
--outer rim of bone tissue
--relatively thin, extremely strong
--based on thin sheets of dense bone tissue that are laminated together

Front 58

Spongy Bone-

Back 58

A network of interlocking trabeculae, making a spongy-like appearance
--found in the ends of the bone and provide internal support without adding too much weight

Front 59

Fetal Bone Formation-

Back 59

Intramembranous Ossification-
--in the flat bones of skull
--mesenchyme cell from a membrane in the shape of the bone and later will change into osteoblasts and form bone tissue
--2 soft spots are the last to to change into bone, allowing skull to grow more after birth; skull is mostly complete to allow child to survive birthing process

Endochondral Ossification-
*Occurs in long bones, 6-9 weeks from conception; inside-cartilage
*bone starts out as all cartilage (hyaline) and change mesenchyme cells to chondroblast
*Cartilage is broken down from center out
*as the cartilage tissue dies, it dies and is calcified and reabsorbed by osteoclast signaling for osteoblasts to lay down bone tissue, slowly changing the cartilage to bone
*a thin rim of cartilage will remain to become the epiphyseal plate (growth plate)

Front 60

Epiphyseal Plate

Back 60

Growth plate
--allows the long bone to grow in length during childhood
--there is a proximal and distal growth plate on each long bone
--each plate will stop growing at a predetermined age; closeure starts with the upper limbs first then the lower limbs

Front 61

Nervous Tissue-

Back 61

Able to create an electrical signal, transmit that signal and analyze these electrical signals
--2 levels:
*controls and monitors the body internal organs
*able to intereact with its environment and learn
--Can analyze incoming signals (sensory) and make decisions based on the sensory information and can translate these decisions into action (motor)
--can remember both sensory and motor events for future use (memory)

2 major categories:
--Central Nervous System- Brain and Spinal Cord
--Peripheral Nervous System- peripheral nerves

Front 62

Organization of Nervous System-

Back 62

CNS--> motor output (somatic(muscle) and autonomic)--> PNS--> sensory input

--going in CNS (afferent)- taking sensory info,
--going out CNS (efferent)- makes a decision and send signal out of CNS; efferent-motor nerves:
--conscious decisions-Somatic nerves- goes to skeletal muscle
--unconscious decisions- Autonomic (automatic)- goes to cardiac muscle, gall bladder, visceral muscle, stomach (muscle innervation of internal organs

*everything the brain decides to do- MOTOR response

*nerves travel only in one direction

Front 63

Neuron-

Back 63

Primary Nerve Cell
--has different cell processes that extends from cell and is used to connect electrical pathways
--multipolar neuron mostly in brain; more complex
--DENDRITES (input)- smaller but usually multiple processes, used for input with other neurons
--AXON (output)- single very long cell process, used for output to next neuron; end of axon- presynaptic area- where neurotransmitter is released
--Cell Body (soma)- contains nucleeus and most of cell organelles
--Synapse- interface or connection btw adjacent neurons; allows the signal to jump btw the neurons
--signal- neurotransmitter
--follow neuron- postsynaptic area
--space btw 2 neuron- synatpic space or synaptic cleft

Front 64

Types of Neurons-

Back 64

Bipolar-

Unipolar-

Front 65

Neuroglia-

Back 65

Cells found in the nervous system that aid or support neurons
--care for, feed, help neurons; no electrical stimulation
--lined up in line with neurons

Front 66

Types of Glia Cells-

Back 66

Astrocytes (CNS)- most abundant; uses processes to make blood-brain barrier (btw small blood vessels and actually brain tissue, preventing movement of toxins and poison from getting to brain); hold circuitry (neuron cell processes) together; produces scar tissue; hand feeds neuron (passes nutrients from blood to avon);

Oligodendrocyte (CNS)- produces myelin, which increases the speed of transmission; 300 mph-white matter (myelinate); 50 mph-grey matter (non-myelinate)

Microglia (CNS)- does phagocytosis of bacteria and dead neurons

Ependymal cell (CNS)- look like simple cubodial cells, found in spaces in brain (ventricals), makes CSF- protects brain

Schwann Cells (PNS)- produces myelin, increase transmission speeds

Satellite cell (PNS)- surrounds and supports cell body of PNS cells; tries to imitate astrocytes

Front 67

Nerve Physiology- Resting State-

Back 67

Resting State:
1). neuron separates Na and K ions on opposite sides of membrane using Na/K pump
2). pumps 3 Na ions out for every 2 K ions into cell,
3). this causes outside of cell to become more positive than the inside ("Resting Potential")

* uses no energy, just preparation
*inside cell is partially negative due to Cl ions that are moved in cell with Na ions

Front 68

Nerve Physiology- Depolarization-

Back 68

Depolarization:
1). 2 Na gates in first channel open (by neurotransmitter), allowing Na ions to rush into cell,
2). this causes a change in membrane polarity around channel, making it really positive inside and more negative outside; the wave continues does the neuron
3). Once this section of neuron has been depolarized, and the wave has moved on, the first section will start to reset

*everything happens just outside or just inside the membrane
*entire membrane does not depolarize at one, starts at dendrite and moves towards axon in a wave, open Na gates along the way

Front 69

Nerve Physiology- Repolarization-

Back 69

Repolarization:
1). one Na gate closes, trapping Na inside, and a K gate opens ("Absolute Refractory Period"), allowing K to leave cell
2). K gate closes and Na/K pump starts pumping 3 Na out and 2K in
3). When Na and K concentration have normalized, the outside is positive and inside is more negative, second Na gate will close
("Relative Refractory Period")
4). Once all Na and K have been separated, the cell is back in "Resting Potential"

*occurs after depolarization wave has moved a small distance down the axon
* second Na gate must close before gates can be reopened in another depolarization

Front 70

Types of Propagation-

Back 70

Continuous- occurs to unmyelinated nerves an Action potential travels along nerve from start to finish

Saltatory- ocurs in myelinated nerves and the action potential skips and jumps from node to node
--node occurs at regular intervals along nerve's length, where myelin sheaths thins;
--allows action potential to travel faster

Front 71

Refractory Periods-

Back 71

1st- Absolute- can't fire neuron because only one Na gate is closed and need both to be closed
2nd- Relative- when 2nd gate is closed, could fire, concentrations haven't gotten back to normal, but could fire neuron if needed