Anatomy + Physiology Flashcards
Chemical elements in body w/ %
O - 65
C - 18.6
H - 9.7
N - 3.2
Atoms
Smallest stable unit of matter.
Electron cloud
Orderly series of energy levels. Hold certain amount of electrons
Isotopes
Varieties of elements that differ in number of neutrons
Molecule
Chemical particle comprising two or more atoms in a chemical bond
Compound
Molecule w/ two or more DIFFERENT elements
Molecule
A chemical particle comprising two or more atoms in a chemical bond
Molecular formula vs structural formula
Molecular: Identifies elements and numbers of atoms present
Structural: Identifies location of elements
Ionic, covalent and Hydrogen bonds
Ionic: Charged particles w/ unequal number of protons and electrons
Covalent: Sharing electrons occupying single energy shells comon to both atoms
Hydrogen: Weak attraction between slightly +ve H and -ve O or N
Mixtures
Physically blended, not chemically combined. Eg body fluid.
Water properties
Polar covalent bonds. Solvency, cohesion, adhesion, thermal stability, chemical reactivity
Adhesion
Tendency of different molecules to bond with each other eg water to large membranes to reduce friction around organs
Cohesion
Force of attraction between same molecule. eg film on water surface due to molecules held together with surface tnesion
Chemical Reactivity
Ability to participate in chemical reactions. H20 involved in hydrolysis and dehydration synthesis
Thermal Stability
Helps stabilities internal body temperature. Calorie: Amount of heat that raises temperature of 1g of H2o by 1 degree
Solutions
Particles mixed with an abundant substance called solvent
Colloids
In body and often mixtures of protien w/ h20. - gel to liquid states
Suspension
To large to penetrate selectively permeable membrane eg blood cells in plasma
Acids vs Bases
Acid: Proton donor
Base: Proton acceptor (release oh-)
pH
Measure derived from the molarity of H+. 7 (Neutral), less than 7, acidic, more than 7, basic. (LOGARITHMIC SCALE)
Buffers
Chemicals that resist changes in pH
Energy
Capacity to do work - building molecules or contracting muscles.
Types of energy
Potential energy (Stored in an object). Kinetic energy (in motion eg Heat).
Types of chemical reactions
Decomposition:: large molecule -> small
Synthesis: Small molecule -> large
Exchange: Two molecules exchange atoms/groups
Catabolism + Anabolism
C: Energy releasing (EXERGONIC) Decomposition reaction. breaks covalent bonds.
A: Energy storing (ENDERGONIC) synthesis reactions
Redox
Oxidation of one molecule = reduction of another. Electrons trasnfered as hydrogen atoms
Carbon compounds
Four valence electrons binds to other atoms. Carbon bacbones - forms long chains.
Carbohydrates
Hydrophilic organic molecules (starch, sugar)> (CH2O)n, n= number of carbon atoms. Glucose n = 6. (C6H12O6). 2:1 ratio of hydrogen to oxygen.
Conjugated Carbohydrate
covalently bound to lipid or protein moiety
Lipids
Contain carbon, hydrogen and oxygen. Hydrophobic moleculs w/ high ration of hydrogen to oxygen (1:2 carbon to hydrogen). More calories per gram than carb. Better for energy storage.
Tryglycerides
neutral fats, three fatty acids linked to glycerol. Formed by Dehydration synthesis.
Fatty Acids
4-24 carbon atoms with carboxyl group. Saturated - 4 carbon bonds. Unsaturated - 1 or more double bonds. Polyunsaturated - multiple double bonds. ESSENTIAL FATTY ACIDS MUST BE OBTAINED VIA FOOD
Steroids
17 carbon atoms in four rings. Cholesterol - parent steroid. Roles in nervous system function and structural integrity of cell membranes. 15% of cholesterol comes from diet, 85% from liver. Eg. estrogen, testosterone
Protien
Polymer of Amino acids
Amino Acids
Centeral carbon with three attached amino groups, carboxyl group and Radical group. 20 amino acids used to make protien
Peptide
Molecule comprising two or more amino acids by PEPTIDE bond (Two amino groups of one amino acid w/ carboxyl group (Dehydration synthesis)
(Protien) Primary structure
Sequence of amino acids which is encoded in genes
(Protien) Secondary structure
Coiled/folded shapes w/ hydrogen bonds
Tertiary structure
Further bendign and folding into globular and fibrous shapes to to hydrophobic/philic and van der walls forces
Enzymes
Protiens that fucntion as biological catalysts. Substrates attaches
NAMING ENZYMES
Ase suffix. Amalayse
Enzyme process
↔Approaches active site, bind together, enzyme, substrate = lock and key. Enzyme releases reaction products, unchanged to repeat process.
Cell shapes
Squamous (thin and flat), cuboidal (cube shaped), Columnar (taller than wide), Fusiform (thick in middle, tapered ends)
Plasma cell membrane
Surounds cell and defines boundaries - protein and lipids
Cytoplasm
Organelles, cyutoskeleton, inclusions, cytosol.
Extracellular fluid
Fluid outside cells (includes tissues)
Nucleus
Largest organelles. Usually 1 nucleus. (Anuclear or multinucleate)
Nuclear Envelop
The double membrane around the nucleus. - Nuclear pores and regulate molecular traffic
DNA
Deoxyribonucleic acid (ACTG) Double strand
RNA
Ribonucleic acid (ACGU) Single strand
Mitochondria
Organelles specialized for synthesising atp. Double membrane (inner - cristae)
Rough Endoplasmic reticulum
Parallel flattened sacs covered w/ ribosomes. Produces phospholipids and proteins of plasma membrane.
Smooth Endoplasmic Reticulum
Lacks ribosomes. Cisternae more tubular and branching. Countinuing off Rough endoplasmic reticulum. Makes steroids and lipids.
Ribosomes
Small granules of protien and RNA. Found in nucleoli and on Rough ER. Reads genetic messages from mRNA and assembles amino acids
Golgi Complex
Systems of cisternae that synthesises carbohydrates and completes protein synthesis
Lysosomes
Package of enzymes bound by membranes. Generally round by variable in shape. Intracellular hydrolytic digestion of proteins.
Peroxisomes
Like lysosomes but contains different enzymes and are produced by ER. uses molecular O2 to oxidise organic molecules
Peroxisomes
Like lysosomes but contains different enzymes and are produced by ER. uses molecular O2 to oxidise organic molecules
Proteasomes
Hollow cylindrical organelles that dispose of surplus proteins. Break down tagged targeted proteins to make peptides/ amino acids
Centrioles
Short cylindrical assembly of microtubes. 9 groups with three microtubules in each. Helps cell division
Inclusions
Stored cellular products or Foreign.
Flagella
Tail of sperms. Whip like structure.
Pseudopods
Continually changing extensions of the cell - used for locomotion
Plasma cell membrane
Boarder of the cell. Selectively permeable lipid bilayer Made up of Lipids, proteins and carbohydrates
Membrane Lipids
75% are phospholipids. hydrophilic heads, hydrophobic tails.
20% cholesterol. Holds phospholipids still.
5% glycolipids contributes to glycocalyx.
Membrane proteins (Peripheral and Intergral)
2% of molecules but 50% of the weight. Integral and Peripheral.
Peripheral: Adhere to one face of the membrane.
Integral: Penetrate membrane.
Second Messengers
Receptor Activates G protein that obtains energy from Guanosine triphosphate. Relays signal to adenylate cyclase which converts ATP to cAMP
Glycocalyx
Fuzzy coat external to the plasma membrane. Carbohydrate Moieties (little pieces)
Microvilli
Made of microfilaments to increase surface area. Used for Absorbtion
Cilia
Made of microtubules to function in movement. Hair like. (ear, nose, airway)
Cytoskeleton
Network of protein fibres to determine cell shape and movement within cells
Filtration
Particles given through emmbrane by physical pressure. Eg filtration of water + small solutes through gaps in capillary walls. Driven by hydrostatic pressure
Simple Diffusion
net movement of particles from high concentartion to lower concentration - due to constant spontaneous molecular motion. Molecules collide and bounce of one another. Substances diffuse down their concentration gradient. Does not require a membrane. Substance can diffuse through membrane if membrane is permeable to the substances
Osmosis
Net flow of h20 through selectively permeable membrane. Moves from more concentrated to less concentrated.
Carrier Mediated Transport
Transport protiens in membrane caryr solutes in/out of cell or organelle (specific) Uniport, symport, antiport.
Facilitated Diffusion
Mcgraw diagram 3,18
Primary Active Transport
Carrier moves solute through membrane up its concentration - uses ATP. Eg Sodium potassium pump
Secondary Active Transport
Carrier moves solute through the membrane but uses atp indirectly. Sodium-glucose transporter
Cellular respiration
Conversion of nutrients into a form usable by cells. - achieved by the production of ATP
High energy bonds = ATP
Connect a phosphate group of one compound to another. Formation of ATP or addition of free phosphate molecule to another molecule
Formation of high energy bonds - ATP
Start with nitrogenous base.
ADD Ribose molecule + phosphate group
Adonenie (mono, di, tri etc) phosphate
ATP
Most important energy transfer molecule. stores energy fron exergonic reactions. Holds energy in covalent bonds and quickly releases that energy from work
Formation of ATP
ENergy storer. ANabolsim - uses energy. Requires an enzy,e (ATP synthesase)
Hydrolysis of ATP
Catabolism - releases energy. Requires enzyme (Adenosine triphosphate). Enzyme breaks 3rd high energy phosphate bond. Separates ATP into ADP and P + energy
Oxidation
Loss of hydrogen or gain of oxygen. Looses electrons
LEOA
GERC
remember that? thats y12 work
dumbarse
Oxidation/reduction reactions and coenzymes.
Catalysted by enzyme
H removed- dehydrogenases
o is added -oxidases.
Both require coenzymes.
NAD+
Nicotinamide adenine dinucleotide (vitamin b)
NAD+ + 2H+ -> ADH + H+
FAD
Falvin adenine dinucleotide
FAD + 2H+ -> FADH2
Mitochondria energy protuction
Double membrane. Outer surounds organelle. The inner is folded (cristae). enzymes in the matrix (Fluid inside) catalyze reaction to produce energy
ATP synthesis
Substrate level phosphorylation.
Oxidative phosphyloration
Substrate level phosphorylation
Atp is formed from ADP by adding a phosphate group. Occurs in glycolysis and krebs cycle
Glycolysis
Splitting glycose into 2 pyruvates. If ATP demand outpaces o2, supply pyruvate ferments to lactate. if enough o2 is present, aerobic respiration occurs
2 x 3-carbon molecules of pyruvic acid.. Converted to lactic acid if 02 not avaliable. Enter aerobic pathway if avaliable.
NADH + H+ -> NAD+ + H2. NBeg gain of 2 ATP
Oxidative Phosphorylation
Generates ATP, CONSUMES atp and coenzymes are required. Occurs in mitochondria. (electron transport proteins) Hydrogen Atom splits into h+ and electrons. Electrons transfer across membrane + loose energy. Released energy via h+ pump between mitochondrial membranes. Energy captured from H+ flowing through atp synthase.
Electron transport system
Cytochromes pass H + e- to oxygen to make h20. Generates ATP. Primary source of H20 (metabolic).
Carbohydrate Metabolism
Dietary carbs burned as fuel within a few hours of consumption. High energy bonds from carbs (glucose). 1 glucose molecule makes 26 molecules of ATP
Glucose Metabolism
Starts in the cytosol/plasm with glycolysis (sugar breaking). Takes palce w/ w.o. o2. Each glucose molecule = 2 pyruvic acid molecules. acid enters mitochondria and co2 is removed. Remained goes to Krebs cycle.
Major phases of glycolysis
Sugar activation:Gkucose is phosporlyated and uses 2 atp. energy stored
“ cleave: split into 3 carbon fragments
oxidation + ATP: Removal of h and phosphate group attached.
Krebs Cycle
Some of the original energy from glucose is ATP and NADH. lost as heat. Most of the energy remains in pyruvate (chemical bonds).
Presence of o2 breaks down pyruvic acid. Enzymic pathway - to produce more ATP. Removes H from organic molecule and transfers to Coenzymes. Accept electrons from one molecule and givces to another
Coenzyme A
Involved in the metabolism of carbon sugars. Joins 2 C molecules in Pyruvate. Activated form of acetic acid. Moves to Krebs cycle. 2 C molecules join with 4 already in cycle. 6 c = citric acid
Substrate Level Phosphorylation
ATP is made from ADP by adding a phosphate group. 4 carbons are resynthesised making another NAD in the cycle to make NADH and FAD. uses 1 pyruvate.
Electron transport system
The remaining energy from glucose is released via e- transport train. The nadh and fadh work w/ enzymes (oxidation. Max number of ATP is 32-34. GLycolysis takes place in cytoplasm. Krebs takes place in mitochrondia
Anaerobic Fermentation
Absence of o2 can generate atp by glycolysis. needs supply of NAD+ (donates e- to pyruvate) - makes lactate. which travels to liver. o2 avaliable lactate changes back to pyruvate.
Lipid metabolism
Tryglicerides stored in adipocytes (turnover 2/3 weeks). released into bloodstreem and transported or oxidised into other fat cells
Lipogenesis
Synthesis of fat from other types of molecules. Amino acids and sugars used to make fatty acids and glycerol.
Lipolysis
Fatty acids enter mitochondria. Broken down into carbon fragments that can be unces in Beta oxidation.
Tissues
Group of similar cells and cell products that perform specific roles in organs
Organs
Structure with discrete boundaries. Comprising two or more tissue types
Histology
Study of tissues and how they are arranged in organs
Tissue Examination
Cross section - longitudinal, cross and oblique
Primary tissue classes
Epithelial, connective, nervous, muscle
Cell junctions
Connects between two cells. Anchored to each other or to their matrix. Communicate with one another
Tight junctions
Linkages between cells aby transmembrane cell-adhesion proteins
Desome
‘Patch’ that hodls cells together - like a peg Resist mechanical stress
Hemidesmosomes
Anchor basal region of cells to basement membrane. Cannot peel away from underlying tissue
Gap junctions
Transmembrane proteins, ions, nutrients and other small solutes pass between cells
Epithelial Tissue
Forms sheets of closely adhering cells. One or more cells thick. Covers body surfaces and line body cavities. Constitutes most glands. Avascular ( no blood vessels)
Basement membrane
Layer between epithelium and underlying connective tissue. Anchors to epithelium to the connective tissue below it
Basal surface
Surface of epithelial cell facing basement membrane
Apical surface
The surface of epithelial cell away from the basement membrane
Epithelial tissue functions (memorise atleast 3)
Protect deeper tissue from injury
excrete wastes
Absorbs chemicals including nutrients
sense stimuli
Simple epithelia
One layer of cells (name according to cell shape) all cells touch basement membrane.
tratified epithelia
More than one cell layer. Names according to shape of apical cells. Soem cells rest ontop of others and do not touch basement membrane
Pseudostratified columnar epithelia
Appears stratified as some cells taller than others. Every cell reaches basement membrane but not all cells reach free surface
Goblet cells
Mucus secreting cells in simple columnar and pseudostratified epithelia.
Simple squamous epithelium
Single layer of thin cells. permits rapid diffusion or transport of substances. (Alveoli, glomeruli, endothelium.)
Simple cuboidal epithelium
Single layer of square/round cells. absorption and secretion. Mucus production and movement. (liver, thyroid, salivary glands, kidney tubules)
Simple columnar epithelium
A single row of tall narrow cells with oval nuclei in bottom half of cell. (digestive tract, uterus, kidney)
Pseudostratified epithelium
Looks multilayered, but al lcells touch basement membrane. Nuclei at several layers.
Straifited epithelia
2-20 layers of cells (1mm). cells rest directly on others. only deepest layer touches basement membrane.
Straified squamous (most widespread. skin)
Stratified cuboidal (two or more cell layers. secrete hormones/sperm/sweat)
Stratified columnar (rare)
transitional epithelium (multilayered epithelium - surface cells flat)
Keratinized stratified squamous epithelium
Multiple cell layers, cells become flat and scaley towards the surface. Resists abrasion, retarts water loss, resists penetration
Non keratinized stratified squamous epithelium
Same as keratinized epithelium without surface layer of dead cells. resists abrasion and penetration of pathogens. (tongue, oral mucosa, esophagus)
Connective tissue
Diverse, abundant type of tissue with few cells relative to matrix. Most cells not in direct contact with one another. Supports and connects organs. Have blood vessels
onnective tissue functions
Connecting organs (tendons and ligaments)
support (bone and cartilage)
physical protection ( cranium, rubs, sternum)
immune protection (white blood cells)
movement (bones provide lever system)
storage (fat, calcium, phosphorus)
heat production (metabolism of brown fat in infants)
Transport (blood)
fIBROBLASTS
Produce fibers and ground substance of matrix
Macrophages
Phagocytize foreign material and activate immune system when detecting foreign matter.
Fibrous connective tissue
Plasma cells - synthesize antibodies (protien)
Mast cells - often found alongside blood vessels. secrete herapin and histamine.
Adipocytes - store triglycerides
Collagenous fibres
Collagen in most abundant protein. 25% touch flexible and stretch resistant. (tendons and ligaments)
Reticular fibers
Thin colalgen fibers coated w/ glycoprotein. Famework for spleen and lymphnodes.
Elastic fibers
Thinner than collagenous fibers. Branch and rejoin each other. Protien called elastin
Glycosaminoglycans (GAGs)
Long polysaccharides comrpising amino sugars and uronic acids. Regulare water and electrolyte balance of tissues
Proteoglycans
Large molecules shaped like bottle brushes. formed colloids that hold tissues together
Adhesive glycoproteins
Protein carbohydrate complexes. Bind components of tissues together
Loose connective tissue
Abundant gel like substance between cells.
Areolar
Loosley organized fibers. Mostly collagenous, elastic and reticular fibers. Found in all tissues .supply infection fighting leuckocytes.
Reticular
Mesh of reticular fibers/fibroblasts. Forms supportive framework for lymphatic organs
Dense regular connective tissue
Densely packed parallel collagen fibers. Elastic tissue forms wavy sheets in some locations. - Tendons and liagments.
Dense irregular
Densely packed, randomly arranged collagen fibers and few visible cells. Withstands unpredictable stresses - deep layer of skin, capsules around organs.
Adipose Tissue
Empty looking cells within margins and nucleus against cell membrane. Energy storage, insulation, and cushioning. Fat and organ packing.
Cartilage
Firm connective tissue with flexible matrix. Hyaline, fibrocartilage, elastic
Chondroblasts, chondrocytes and perichondrium
Chondroblasts: Cartilage cells - produce matrix that surrounds them.
Chondrocytes: Mature cartilage cells
Perichondrium: sheath of dense irregular connective tissue that surrounds elastic and most hyaline cartilage
Hyaline cartilage
Clear glassy. fine colalgen fibers. Movement - holds airway open, growth of long bones. eg trachea, larynx, fetal skeleton
Elastic cartilage
The abundance of elastic fibers. Covered with perichondrium. Provides flexible but elastic support.
Fibrocartilage
Contains large coarse bundles of collagen fibers. Resist compression and absorbs shock. Resists compression and absorbs shock.
Osteogenic
Stem cells arise from embryonic mesenchyme. Multiply continuously to give rise to other bone cell types.
Osteoblasts
Bone forming cells. form single layer under endosteum and periosteum and non mitonic. Hardens by mineral deposition.
Oseocytes
Former osteoblasts, trapped in matrix.
Osteoclasts
Bone dissolving cells found on bone surface. large cells formed by fusion of several stem cells. multiple nuclei/cells.
Bone matrix
1/3 organic 2/3 inorganic. Organinc matter synthesised by osteoblasts (collagen, carbohydrate, protein complexes)
Inorganic matter
85% hydroxyapatite. 10% Calcium carbonate. other minerals (F, Na, K, Mg)
Composite material
Combination of ceramic and polymer. Hydroxapatite and other minerals are the ceramic and collagen.
Periosteum
Tough fibrous connective tissue covering the whole bone. Onion like layers around central canals. Run longitudinally though shafts of long bones. blood vessels and nerves.
Spongey bone
Lattice of bone covered with endosteum.
SLivers of bone - spicules
Thin plates of bone - trabeculae (red bone marrow)
Red Marrow
Myeloid tissue. Contains hemopoietic tissue. Produced blood cells - in almost every bone in child. in adult skull, vertebrae, ribs, sternum, heads of humerus/femur.
Yellow marrow
Found in adults. fatty marrow doesnt produce blood. Can transform into red in case of chronic anemia.
Bone development
Ossification or osteogenesis
Intramembranous ossification
Produces flat bones of skull and calvical in fetus. thickens long bones throughout life.
Endochondral ossification
All other bones made like intramembranous
bone remodeling
Absorption and deposition - occurs 10% per year
Wolffs law of bone
Architecture of bone determined by stresses placed on it.
Bone physilogy
Mature bone a metabolically active organ.
Upper lim four regions
Brachium (between shoulder and elbow). Antebrachium (forearm). Hand, Pectoral girdle (scapula + claviacal)
The scapula
Flat bone on postero-lateral aspect of thorax - overlays ribs 2-7. SHoulder blade
Spine of Scapula
Transverse ridge on the posterior surface - supraspinous fossa (Above spine groove). infraspinatus fossa (surface below the spine
Suprascapular notch
Superior border - provides passage for nerve and vessels
Subscapular Fossa
Concave anterior surface of scapular (surface facing the ribs)
Acromion process
Extension of the spine - forms apex of the shoulder. Aritculates clavical - point of attachment of scapular and upper limb to rest of skeleton
Coracoid process on scapula
Projection on ventral surface - attachment site of muscles
Glenoid cavity
Shallow socket (humerus joins). Articulates with head of humerus to form glenohumeral joints
The clavicle
S shaped long bone (intramembranous ossification). FIrst to appear in embryo. Extens horizontally across root of neck towards shoulder (COLLARBONE)
Sternum
Bony plate anterior to the heart (palpable - subcutaneous in aprts).
Sternum Three regions
Manubrium, Body (gladiolus), xiphoid process
Humerus - proximal end
- Hemispherical head - articulates with glenoid cavity of scapula.
- anatomical neck.
- greater and lesser tubercles
- intertubical sulcus - biceps tendon
- Surgical neck
- Deltoid tuberosity
Humerus - Distal end
- Capitulum - articulates with head of radius
- Trochlea - articulates with ulna
- Lateral and medial epicondyles
- Olecranon fossa - olecranon process of ulna
- coronoid fossa
- radial fossa
The Humerus
Fractures not uncommon (any site during the length)
- Epiphyseal separation in adolescents
- Osteoporosis
- Metastases
- May result in nerve damage.
- Auxillary nerve
- Musculocutaneous nerve
- radial nerve
- ulnar nerve
Radius - proximal end
- Head: Disc-shape allows for rotation during pronation and supination. Articulates with capitulum on humerus
- Neck
- Radial tuberosity for biceps muscle.
Radius - distal end
- Styloid process - palpated near thumb
- Ulnar notch accommodates head of ulna
Ulna - proximal end
- Trochlear notch - articulates with trochlea of humerus
- Olecranon - bony prominence at back of elbow
- Coronoid process
- Radial notch - holds head of radius
Ulna - distal end
- Styloid process
- Interosseous membrane
Radius and Ulna fractures
Usuall result in fractures to both bones.- Distal radial fractures most common in >50
- Fracture of distal 2cm - colles fracture
- Forced dorsiflexion (Extension) of wrists
- Dorsal displacement - comminuted (broken into pieces)
- Ulna styloid may also be avulsed (broken off bone)
Carpus (wrist)
Eight short bones form the wrist - allows movement of flexion, extension, abduction and adduction. Two rows of carpal bones
Carpus proximal row
Scaphoid, lunate, triquetrum and pisiform
Carpus distal row
Trapezium, trapezoid, capitate and hamate
Metacarples (bones of the palm
- metacarpal 1 - proximal to base of thumb
- metacarpal V - proximal to base of little finger
- Proximal base, body and distal head
Phalanges (bones of the fingerrs)
- Thumb or pollux has two phalanges - Proximal, distal phalanx
- Fingers have 3 phalanges - proximal, middle, distal phalanx
Muscle Attachments
- origin↔stationary point
- insertion↔movable area
- Attachments↔Bone, fascia or tendon of other muscle, skin
- any muscle crosses a joint will act on that joint
Action
Effect produced by a muscle to produce or prevent movement
Four categories of muscle action
- Prime movement↔Muscle that produces most of force during particular joint action
- Synergist↔muscle that aids prime mover
- Antagonist↔opposes prime mover. prevents excessive movement. sometimes relaxes to give prime mover control over action. (ANtagonistic pairs)
- Fixator↔muscle that prevents movement of bone
Four categories of muscle action
- Prime movement↔Muscle that produces most of force during particular joint action
- Synergist↔muscle that aids prime mover
- Antagonist↔opposes prime mover. prevents excessive movement. sometimes relaxes to give prime mover control over action. (ANtagonistic pairs)
- Fixator↔muscle that prevents movement of bone
Muscles acting on the head
Attach to vertebral column, thoracic cage and pectoral girdle.
- Action
- Flexion (bending head forawrd)
- extension (Holding head erect)
- Lateral flexion (moving head to one side)
- Rotation (turning head left and right)
Sternocleidomastoid
Scalene Muscles
Trapezius
Splenius Capitis
Semispinalis capitis
Deep muscle of the back (vertebral column)
- Erector spinae↔Illocostatlis, longissimus, spinalis. EXTENTION AND LATERAL FLEXION OF VERTEBRAL COLUMN
- Semispinalis thoracis↔Extension and contraction rotation of the vertebral column
- Quadratus lumborum↔Ipsilateral flexion of lumbar vertebral column
- Multifidus↔stabilizes adjacent vertebrae, and helps maintain posture
Pectoralis major
- Origins - sternum, upper rubs and clavical to humerus
- insertion: anterior aspects of humerus
- actions: flexion, adduction, medial roation of arm.
- Used in climbing - bring trunk upwards. Sternoscostal fibers extend arm from flexed postion
Pectoralis monor
- Origins - ribs 3-5
- insertion - coracoid process of scapula
- actions - depresses the shoulder
- accessory muscle for respiration
Serratus anterior
- Origins - upper 8 ribs (lateral aspect)
- insertion - medial border of scapula
- actions - protraction and rotation of scapula
- winged scapula - arm raised, medial border and inferior angle move outwards from chest wall
Trapezius
- Origins - nuchal lines, ligamentum nuchae, cervical and upper 6 thoracic spines
- Insertions - lateral end of the clavicle, the acromion process and spine of scapula
- Actions - neck extension (if muscles fixed), elecate/rotate scapula, keep shoulders braced, suspend upper limb, nerve damage = drooping of shoulders
Latissimus dorsi
- Origins - t6-12 spines, lower 3-4 ribs, iliac crest, thoracolumbar fascia (to lumbar and sacral spines), inferior angle of scapula.
- Insertion - humerus (Anterior) - intertubuclar sulcus
- actions - adducts and extends and medially rotates arm, raises body - climbing
Elevator scapulae
- origins - transverse processes of cervical vertebral spines (c1-4)
- insertion - upper medial border scapula (above spine)
- actions - elevation of scapular, tilts glenoid inferiorly
Rhomboid Minor
- origins - spinous processes of C7, T1-2.
- insertion - medial border scapula (opposite spine)
- Actions - elevation and retraction of scapula
Rhomboid Major
- Orgins - spinous processes T2-5
- insertion - medial border of scapular (below spine)
- action - retraction and elevation of scapula
Deltoid
- origins - anterior fibres = anterior border and upper sirface of clavicle. Middle fiber = lateral aspect of the acromion process. Prosterior fibers = lower lip and posterior border of spine of scapula
- Insertion - humerus = deltoid tuberosity
- actions - all fibers abduction. Anterior = flexion of arm, middle = abduction of arm, posterior = extension of flexed arm.
- Prevents dislocation of humerus when carrying heavy weights. insertion pulls/elevates humerus and humeral head/clavicle
Rotator Cuff
Group of 4 muscles Forms cuff around shoulder joint
- Supraspinatus
- Infraspinatus
- teres minor
- subscapularis
Supraspinatus
- origins - supraspinous fossa
- insertion - upper facet on greater tubercle of humerus
- actions - abduction of humerus
Infraspinatus
- Origins - infraspinous fossa
- insertion - middle facet on greater tubercle of humerus
- actions - lateral rotation of humerus
Teres Minor
- origins - lateral border of the scapula
- insertion - lower facet on greater tubercle of humerus
- Actions - lateral rotation of humerus
Subscapularis
- Origins - costal surface of scapula
- insertion - lesser tubercle of humerus
- actions - medial rotation of humerus
Subscapularis
- Origins - costal surface of scapula
- insertion - lesser tubercle of humerus
- actions - medial rotation of humerus
Teres Major
- Origins - costal surface of scapula
- insertion - lesser tubercle of humerus
- actions - medial rotation of humerus
The Axilla (armpit)
Pyramidal shaped region between chest and arm
- Brachial plexus
- xillary artery and vein
- lymph nodes
- Structure↔apex, base, four walls (medial, lateral, anterior, posterior)
Blood Vessles
- Axillary artery/vein (Continuation of subclavian artery and vein)
- artery has 3 named parts in relation to pectoralis minor.
- Lymph nodes - drainage of chest to breast
Brachial plexus
↔Network of nerves that supply the muscles and skin of the upper limb. Supplies all muscles expect thoes attaching axial skeleton to scapula (trapezius and sternomastoid - accessory nerve). Nerves of the plexus are formed by ventral rami of C5,6,7,8 and T1
Spinal cord / spinal nerves
- Grey↔nerve cell bodies - central H shape
- White↔axons - columns of white matter
- Nerves constitute peripheral nervosus system
Grey matter
Dorsal horns contain cell bodies of sensory neurons. Ventral horns contain cell bodies of motor neurons
Formation of mixed spinal nerves
- Formation of mixed spinal nerves↔each neuron gives rise to single axon. Axons from grey matter neurons emerge segmentally from spinal cord
- Dorsal (sensory) ventral (Motor) nerve roots. Dorsal and vental roots join to form mixed spinal nerves
- Mixed spinal nerves emerge from intervertebral foramina. Each contains sensory and motor fibers. Dorsal primary rami supply erector spinae back muscles and skin. Ventral primary rami supply somatic muscle of trunk and limbs and skin
Brachial plexus
- Brachial plexus
- R (roots) - Ventral rami of C5,6,7,8 + t1
- T (trunks) - upper/middle/lower
- D (divisions) anterior and posterior from each trunk
- c (cords0 - lateral, medial and posterior
- B (Branches - named nerves (musculocutaneous, median, ulnar, axilary, radial
Biceps brachii
- Origins - long head (superglenoid tubercle of scapula), short head (coracoid process of scapula)
- Insertion - radial tuberosity
- Actions - flexion of arm and forearm and medial roation of foream
- Nerve supply - musculocutaneous nerve
Brachialis
- Origin - shaft of humerus
- insertion - coronoid process of ulna
- Actions - flexion of forearm
Oracobrachialis
- Origin - coracoid process of scapula
- insertion - shaft of the humerus
- Action - flexion and adduction of arm
- Nerve supply - musculocutaneous nerve
Flexor compartments of the arm
Superficial and deep
Palamris Longus
- Origin: medial epicondyle of humerus
- Insertion: palmar aponeurosis (tendon degenerated)
- Action: flexion of forearm (v. weak) and wrist. Tendinous insertions to MPJ - weak
- Nerve supply: median nerve
- Flexion of the proximal phalanges. May assist in thumb flexion. Missing +/- 13% (depens of sex/population difference). Present in orangs (climbing), variable in chimps/gorillas. Tendon used in graft surgical repair
Pronator Teres
- Origin: medial epicondyle of humerus, coronoid process of ulna.
- Insertion: radial shaft - lateral aspect.
- Action: Flexion of elbow and forearm pronation
- Nerve supply: median nerve
Flexor capri Radialis
- Origin: Medial epicondyle of humerus
- Insertion: Bases of 2nd/3rd metacarples
- Action: flexion of forearm and wrist & radial deviation (Abduction) of wrist.
- Nerve supply: Median nerve
Flexor Carpi Ulnaris
- Origin: Medial epicondyle of humerus, pper posterior border of ulna.
- Insertion: pisiform, hook of hamate and base of 5th metacarpal
- Action: flexion of forearm and wrist, ulnar (medial) deviation/adduction of wrist.
- Nerve supply: Ulnar nerve
Flexor Digitorum Superficialis
- Origin: Medial epicondyle radius.
- Insertion: split to insert on middle phalanges of 4 fingers.
- Action: flexion of elbow, wrist, proximal I-P joints.
- Nerve supply: median nerve
- Strongest when wrist extended. Extensors act as antagonists to reduce excess movement at wrist. Acts as synergists in finger flexion
Forearm rotation
Proximal and distal radio ulnar joints. Rotation of Radius OVER ulna. Pronation and supination. Full supination - autonomical position. Adaption to brachiation
Flexor digitorum profundus
- Origin: upper anterior and medial ulna and interosseous membrane.
- Insertion: distal phalanges of 4 fingers.
- Actions: flexion of elbow, wrists, distal I-P joints
- Nereve supply: Median and ulnar nerve
- BULKIEST, essential for gripping, strongest when wrist extended
Palmaris Profundus
- Origin: anterior radius and interosseous membrane.
- Insertion: distal phalax of thumb
- Actions: flexion of thumb & wrist when thumb fixed.
- Nerve supply: median nerve
Pronator Quadratus
- Origin: Distal anterior ulna.
- Insertion: distal anterior radius
- Action: pronation of forearm
- Nerve supply: Median nerve
Nerve supply to forearm
Flexor compartment - median and ulnar nerves
Median nerve
Enters tforearm through 2 heads of pronator teres.
Ulnar Nerve
Grooves in the medial epicondyle and passes into flexor carpi ulnaris
Radial nerve
Pierces Supinator
Brachial artery
divides into radial and ulnar arteries (cubital fossa).
Radial Artery
Lateral side of forearm, covered by skin, superficial and deep fasciae. At wrists, runs dorsally to enter anatomical snuff box. Passes through 1st dorsal interosseous muscle to enter palm.
Ulnar artery
Larger - usually lies deep to superficial compartment muscle. Gives rise to common interosseous (I-O) artery just below radial tuberosity. Divides into anterior and posterior (I-O) arteries on either side of membrane. Crosses over flexor retinaculum - accompanied by ulnar nerve. Distally becomes more superficial - pulse palpated deep to flexor carpi ulnaris
Fascia of wrist and hand
Tough bands of fibrous tissue across wrist - thickening of deep forearm fascia
Flexor and extensor retinaculae across wrist
- Attach to bones of the proximal and distal rows of carpal bones
- Lined by synovial sheath
- bind long tendons at wrist, prevent bow stringing.
- Attachment for intrinsic muscles of hand
Palmar aponeurosis
hin triangular sheet. tough connective tissue - apex attached to flexor retinaculum. Central, covers tendons in palm. Forms insertion of palmaris longus
Fibrous flexor sheaths
Tendons at wrist in ‘tunnels’ surrounded by synovial membrane. Synovium ensures that tendons ‘glide’ freely in fibrous sheaths
Carpal tunnel
Flexor surface at wrist. Flexor retinaculum attached to carpal bones - creates osseo-fibrous tunnel. Non elastic, non distensible. Contains long tendons of fingers and median nerves
Extensor compartment of the forearm
Superficial and deep
Branchioradialis
- Origin: lateral supracondylar line of humerus
- Insertion: distal radius above styloid process
- action: flexion of forearm
- Nerve supply: radial nerve
Anconeus
- Origin: lateral epicondyle of humerus
- Insertion: posterior ulna, olecronon process
- Actions: extension of forearm
- Nerve supply: radial nerve
Extensor carpi radialis longus
- Origin: supracondylar line of humerus
- Insertion: base of 2nd metacarpal
- Actions: extensions and abduction of wrist
- Nerve supply: radial nerve
Extensor carpi radialis brevis
- Origin: lateral epicondyle of humerus
- Insertion: base of 3rd metacarpal
- Action: extension of wrist
- Nerve supply: radial nerve
Extensor carpi Ulnaris
- Origin: Lateral epicondyle of humerus, posterior border ulna
- Insertion: base of 5th metacarpal
- Actions: extension/adduction of wrist
- Nerve supply: radial nerve
Extensor digitorum communis
- Origin; lateral epicondyle of humerus
- Insertion: middle and d istal phalanges of medial 4 fingers
- actions: extension of digits and wrists
- Nerve supply: radial nerve
Supinator
- Origin: lateral epicondyle of humerus, supinator crest of ulna
- Insertion: lateral aspect of radius (mid region)
- actions: spination of forearm:
- Nerve supply: radial nerve.
- Usually acts alone (unopposed supination)> Fast/forecful supination - works w/ bicepts
Supinator
- Origin: lateral epicondyle of humerus, supinator crest of ulna
- Insertion: lateral aspect of radius (mid region)
- actions: spination of forearm:
- Nerve supply: radial nerve.
- Usually acts alone (unopposed supination)> Fast/forecful supination - works w/ bicepts
Extensor indicis
- Origin: Ulna and I-O membrane
- Insertion: phalanges 2&3 of index finger
- Actions: extension of indext finger and wrist
- Nerve supply: radial nerve
Extensor Pollicis Longus
- Origin: lateral, middal 1/3 posterior ulna and I-O membrane.
- Insertion: base of distal phalanx of thumb
- Actions: extension distal phalanx of thumb
- Nerve supply: radial nerve
Extensor Pollicis Longus
- Origin: lateral, middal 1/3 posterior ulna and I-O membrane.
- Insertion: base of distal phalanx of thumb
- Actions: extension distal phalanx of thumb
- Nerve supply: radial nerve
Extensor pollicis brevis
- Origin: posterior radius of I-O membrane
- insertion: proximal phalanx of thumb
- Actions: extension of thumb and abduction of wrist
- Nerve supply: radial nerve
Abductor pollicis Longus
- Origin: posterior ulna and I-O membrane
- Insertion: base of 1st metacarpal lateral
- Action: Abduction of thumb and wrist
- Nerve supply: radial nerve
The human hand
Prehensile to grasp hands and feet. Increased indipentend mobility of digits. Can be rotated to face palm and other digits.
Muscles of the hand - palmar surface
- Thenar muscles - act on the thumb
- Hypothenar muscles - act on the 5th digit (little finger)
- Lumbrical muscles - dual actions
- Palmar interossei - acts on digits
Structure of thumb and joints
- First digit - metacarpal and proximal and distal phalanges
- Thumb metacarpal shorter at right angles to plane of other metacarpals
- articulates with carpals in saddle joint - only one in the body
- Lax, strong capsule and articular surfaces - rotation and wide range of movement
- Distal pad of thumb can be placed against pads of other fingers - opposability - vital for grip\
Abductor pollicis brevis
- Origin: flexor retinaculum, scaphoid and trapezium
- Insertion: radial base of proximal phalanx
- Actions: abducts thumb at CMJ, extends IPJ
- Nerve supply: Median nerve
Flexor pollicis brevis
- Origin: flexor retinaculum and trapezium
- Insertion: Proximal phalanx
- actions: flexes MCPJ
- Nerve supply: Median nerve
Opponens pollicis
- Origin: flexor retinaculum and trapezium
- Insertion: radial aspect of 1st metacarpal
- Action: opposition of the thumb
- Nerve supply: median nerve
Abductor digiti Minimi
- Origin: pisiform and flexor retinaculum
- Insertion: 5th digit, base of proximal phalanx
- Action: Abduction of MCPJ
- Nerve supply: Ulnar nerve
Flexor digiti minimi brevis
- Origin: Hook of hamate and flexor retinaculum
- Insertion: 5th digit, base of proximal phalanx
- Action: Flexes MCPJ and assists with opposition
- Nerve supply: Ulnar Nerve
Abductor Pollicis
- Origin: oblique head - palmar surfaces of trapezoid, trapezium and capitate, bases of metacarpals of index + middle figners. Transverse head - palmar surface of shaft of middle metacarpal
- Insertion: proximal phalanx of thumb
- Action: adducts the thumb
- Nerve supply: Ulnar nerve
Palmaris brevis
- Origin: flexor retinaculum, superficial palmar fascia
- Insertion: skin of palm
- Actions: tightens and creases skin, deepens concavity of palm
- Nerve supply: Ulnar nerve
Lumbrical muscles
- Origin: Tendons of flexor digitorum profundus, just distal to carpal tunnel
- Insertion: Dorsal extensor expansions
- Actions : Flexion of MCPJ and extension of IPJ
- Medial 2 nerve supply - ulnar nerve
Lumbrical muscles
- Origin: Tendons of flexor digitorum profundus, just distal to carpal tunnel
- Insertion: Dorsal extensor expansions
- Actions : Flexion of MCPJ and extension of IPJ
- Medial 2 nerve supply - ulnar nerve
Palmar interosseous muscles
- Origin: Palmar surface metacarpals
- Insertion: Proximal phalanges
- Action: Adduct other digits towards 3rd digit
- Single head of origin.
- Axis of movement - line through middle finger
- PAD
- Nerve supply: Ulnar nerve
Dorsal interosseous muscles
- Only muscles on dorsum of hand
- Origin: 2 heads - from adjacent sides of metacarpals
- Insertion: Proximal phalanges and extensor expansion
- Action: Abduct fingers - relative to axis of movement
- DAB
- Nerve supply: Ulnar nerve
Nerve supply to the hand
- Median nerve: Thenar eminence and Lateral 2 lumbrical muscles
- Ulnar nerve: all other muscles of the hand
Nerve supply to the hand
- Median nerve: Thenar eminence and Lateral 2 lumbrical muscles
- Ulnar nerve: all other muscles of the hand
The lower Limb
- Divided into regions like upper limb
- Thigh↔Between hip and knee joint
- Leg↔Extends from knee joint to ankle joint
- Foot: TARSUS
- Connect to trunk via pelvic girdle - pubis, ilium and ischium
The pelvic girdle (3 bones)
- Two hip (coxal) bones - ossa coxae or innominate bones
- Sacrum
- Pelvis - pelvic girdle plus structures of pelvic cavity.
- Sacroiliac joint - posteriorly joins hip bones to vertebral column (sacrum)
- Auricular surface of ileum to auricilar surface of sacrum
- Pubic symphysis - fibrocartilaginous joint - joins pubic bones anteriorly
The Pubis (Body, superior and inferior rami)
- Pubic crest, tubercle. Pectineal line.
- Meets ilium at iliopubic eminence
- Right and left sides meet at pubic symphysis
- Contributes to boundary of obturator foramen
The ilium
Iliac blades - broad iliac fossa. (false pelvis) - inner and outer gluteal surfaces. - Anterior border - two projections, separated by a notch - ASIS and AIIS
- Posterior border - two projections separated by a notch - PSIS and PIIS
- Below PIIS is greater sciatic notch
- Body - participates in formation of acetabulum and lesser pelvis
- Auricular surface for sacrum
The gluteal surface
- Posterior gluteal line: shortest, rusts from iliac crest to upper part of greater sciatic notch
- Anterior gluteal line: longest, begins at crest, ends at upper part of greater sciatic notch
- Inferior gluteal line: Least distinct, ends near middle of greater sciatic notch
The ischium
- Body: contributes to acetabulum and internal surface of wall of lesser pelvis
- Ischial spine
- Above spine - greater sciatic notch, converted to foramen by sacrospinous ligament
- Below spine - lesser sciatic notch, converted to foramen by sacrotuberous and sacrospinous ligaments
- Ischial tuberosity: muscle attachment.
- Ramus contributes to obturator foramen
The Acetabulum
- Deep socket formed by pubis, ilium and ischium.
- Incomplete - horse shoe shaped lunate surface
- Deficient - bridged by transverse ligament
- Socket deepend further by acetabular labrum
- cetabulum faces laterally, inclined anteriorly and inferiorly
The femur features
- Long bone
- Articulates with acetabulum at hip joint
- Head - 2/3 of sphere, faces upwards and medially
- Neck - directed superomedially and inclining anteriorly
- Greater and lesser trochanters
- Intertrochanteric line and crest
- Shaft, linea aspera
- Medial and lateral condyles
- Patellar surface
- Articulates distally with tibia
Angle of inclination
- Angles between femoral neck and shaft.
- Enables limb to swing clear of pelvis. Brings thigh away from body.
- Average of 125 deg. (males>females)
- Changes from
- 150 in newborn
- 145 in young child - 3yrs
- 126-128 in adult
- 120 in old age
Patella
Sesamoid bone
- Develops within quadriceps femoris tendons
- Increase lever function of muscles
Tibula - Larger bone features
- Medial and lateral condules
- Intercondylar area
- Tibial tuberosity
- facet for the head of the fibula
- anterior border
- interosseous border
- soleal line
- medial malleolus
- fibular notch
- concave articular surface for talus
- Joinedb y interosseous membrane
Fibula - smaller bone features
- Head and apex (styloid process) and facet for articulation with tibial condyle
- Interosseous border
- Lateral malleous
- Facet for articulation with talus
- Malleolar fossa
Bones of the foot
Metatarsals
Larger long bones in the feet
Phalanges
Smaller long bones in the feet - make up the toes
Gluteal region in the thigh
Gluteus maximus, medius and minimus
Gluteus maximus
- Origin: posterior gluteal line, sacrotuberous ligament.
- Insertion: ITT and gluteal tuberosity
- Action: Extension of flexed hip and brings limb into line of trunk
- Nerve supply: Gluteal nerves
- Acting as distal attachment, prevents forward movement of trunk from producing flexion at supporting hip during walking
Gluteus medius
- Origin: between posterior and anterior gluteal line
- Insertion: greater trochanter
- Action: Abduction of MR of Hip
- Nerve supply: Gluteal nerves
Gluteus minimus
- Origin: between anterior and inferior gluteal lines
- Insertion: greater trochanter
- Action: Abduction of MR of Hip
- Nerve supply: Gluteal nerves
Lateral rotators of the hip
six small muscles in gluteal region of thigh
- Piriformis↔from ventral sacrum
- Superior gemellus↔from ischial spine
- Inferior gemellus↔From ischial tuberosity
- Obturator internus↔inner surface obturator membrane/foramen
- Obturator externus↔outer surface obturator foramen
- Quaatratus femoris↔from ischial tuberosity
- ALL INSERT ONTO GREATER TROCHANTER (INTERROCHANTERIC CREST)
Nerve supply to lower limb
- Ventral rami of L1-S3 (dorsal and ventral divisions) Emerge through muscles of posterior abdominal and pelvic wall
- Lumbar nerves related to psoas major muscle and sacral nerves to piriformis muscle.
- L4 +L5 form lumbosacral trunk
Femoral nerve
- ## Branches↔Femoral nerve: posterior divisions L2,3,4
Supplies
- Iliacus
- pentineus
- muscles of anterior compartment of thigh
- Emerges through psoas major muscle and passes between psoas and iliacus muscles to enter thigh
Obturator nerve
- Branches↔Obturator nerve: anterior divisions of L2,3,4
Supplies
- Pectineus
- Oburator externus
- Muscles of mediated compartment of thigh
- Emerges medial to psoas major
Sciatic nerve
- Branches↔Sciatic nerve L4,5. S1,2,3
- Enters thigh through greater sciatic foramen below piriformis
- Supplies↔Muscles of the posterior compartment of the thigh
- All muscles of the leg and foot via
- TIBIAL (L4,5 S1,2,3) and common fibular (L4,5 S1,2,3) Nerves
- All muscles of the leg and foot via
Organization of nervous system
Central nervous system (brain and spinal cord)
Peripheral nervous sysem - cranial and spinal nerves/ganglia
PNS
Sensory and motor devisions.
Somatic and visceral subdivisions
Sensory (Pns)
Afferent division carries signals from receptors to CNS.
somatic - carries signals from reeceptors in skin, muscle bones and joints
Visceral - carries signals from viscera (heart, lungs, stomach bladder)
Motor (PNS)
Efferent divisons carries signals from CNS to effectors - muscles that carry out body responce
Somatic - carries signals to skeletal muscles
Visceral - carries signals to glands, cardiac and smoothe muscle
Visceral motor division
Sympathetic division - prepares body for flight and fight (accelerates heart and respiration rate).
Parasympathetic division - tends to have calming affect (slow heart rate and breathing)
Universal properties of neurons
- Excitability↔ability to respond to environmental changes (Stimuli)
- Conductivity↔ability to respond to stimuli by producing electrical signals that are conducted to other cells at distant locations
- Secretion↔When electrical signals reach end of nerve fibre, cell secretes a chemical neurotransmitter that influences the next cell
Functional classes of neurons
- Sensory (afferent) neurons↔Detect stimuli and transmit information about them to CNS
- Interneurons↔Entirely within CNS and connect motor and sensory pathways (+- 90% of all neurons). Receive signals from numerous neurons and perform integrative functions (make decisions on responce)
- Motor (efferent) neurons↔Send signals out to muscles and glands - the effectors
Structure of a neuron
- Stoma/cell body - control centre of neuron
- Single, centrally located nucleus with large nucleolus
- Cytoplasm - contains mitochondria, lysosomes, golgi complex, inclusions, rough ER and cytoskeleton
- Inclusions↔glycogen, lipid droplets and melanin
- Cytoskeleton↔Dense mesh of microtubules and neurofibrils (bunch of actin filaments)
- NO CENTROLES OR MITOSIS
- Dendrites↔branches arising from neurostoma - primary site for receiving signals from other neurons
- More dendrites - more infomation.
- Provides percise pathways for reception and processing of infomation
Structure of a neuron p2
- Axon - nerve fibre
- Originates from neurostoma - axon hillock
- Cylindrical, relatively unbranched most of its length
- Colalterals - bunches of axon
- Branch extensivelly on distal end
- Specialized for rapid conduction of signals to distal points
- Axoplasm↔cytoplasm of axon
- axolemma↔plasma membrane of axon
- One axon per neuron - some have none
- Myelin sheath may enclose axon
- Distal end of axon has terminal arborization. Extensive complex of fine branches.
- Axon ternimal↔swelling that forms junction (synapse) with next cell
- Contains synaptic vesicles- neurotransmitter
Structural classification of neurons
- Multipolar neuron↔one axon and multiple dendrites - most common
- Bipolar neuron↔One axon and one dendrite - olfactory cells, retina, inner ear
- Unipolar neuron↔single process leading away from neurosoma - sensory cells from skin and organs to spinal cord
- Anaxonic neuron↔Many dendrites but no axon - retina, brain, adrenal gland
Azonal transport
many proteins of neurosoma must be transported to axon and axon terminal.
- Repair axolemma↔serve as gated ion channels, enzymes or neurotransmitters
- Two way passage of proteins, organelles and other material along the axon.
- Anterograde transport↔movement down axon AWAY from neurosoma
- Retrograde transport↔movement up axon toward the neurosoma
Fast Axonal transport
Rate of 20-400 mm/day
- Fast anterograde transport↔Organelles, enzymes, synaptic vesicles and small molecules
- Fast retrograde transport↔Recycled materials and pathogens - rabies, herpes, simplex, tenanus, polio viruses
Slow azonal transport
rate of 0.5-10mm/day
- Always anterograde - moves enzymes, cytoskeletal components and new axoplasm down axon during repair and regeneration of damanged axons
- Damaged nerve fiberes regenerate at speed governed by slow axonal transport
Support Cells - Neuroglia
- aprox 1 trillion neurons in nervous system
- neurogilia outnumbers neurons by 10:1
- protect neurons and help them function
- bind neurons together and form framework for nervous tissue
- in fetus, guide migrating neurons to destination
- mature neuron not in synaptic contact covered by glial cells
- Prevent neurons from touching each other
- gives precision to conduction pathways
Oligodendrocytes
form myelin sheaths in CNS that speed signal conduction. Arm like processes wrap around nerve fibers
Ependymal cells
Cuboidal epithelium with cilia on apical surface. Line internal cavities of the brain and secrete and circulate cerebrospinal fluid
Microglia
wander through CNS looking for debris and damage. Develop from white blood cells (monocytes) and concentrate in areas of damage
Astrocytes
↔most abundant - cover brain surface and most nonsynaptic regions of neurons in grey matter - can form scar tissue where needed. Secrete nerve growth factors. Have extensions - perivascular feet that connect blood capillaries and stimulate them to form blood-brain barrier
Astrocytes
Monitor neuron activity and regulate blood and chemical composition of fluid flow to match metabolic need. Convert glucose to lactate and supply this to the neurons
Schwann cells
Envelope nerve fibers in pns. wind repeadly around a nerve fiber. Produce myelin sheath similar to that produced by oligodendrocytes in CNS.
Neurilemma
↔thick, outermost coil of myelin sheath. Contains nucleus of cell and most of its cytoplasm. External to neurilemma is basal lamina and thin layer of fibrous connective tissue - endoneurium
Satellite cells
Surround Neurosomas in ganglia of PNS. Provide electrical insulation and neurosoma. Regualte the chemical environment of neurons
Myelin
- Myelin sheath↔insulation around a nerve fiber. Formed by Schwann cells in PNS and oligondendrocytes in CNS. consists of the plasma membrane of glial cells. 20% protein and 80% lipid
- Myelination↔Production of myelin sheath begins wk 14 of fetal development. Proceeds rapidly during infancy. Completed in late adolescence. Dietary fat is important to CNS development
Myelination in CNS
- Oligodendrocytes - myelinate several fibres in immediate vicinity
- Anchored to multiple nerve fibres. Cannot migrate around fibres. Must push new layers of myelin under older ones.
- Myelination thus spirals inwards towards nerve fibre.
- Nerve fibres in CNS have no neurilemma or endoneurium
Internodes
myelin-covered segments from one gap to the next
Initial segments
short section of fibre between axon hillock and first glial cell
Trigger Zone
the axon hillock and initial segment - play important role in initiating nerve signal
BRain tumours
Masses of rapidly dividing cells
Mature neurons with little to no capacity for mitosis - seldom form tumours.
Brain tumors arise from..?
- meninges
- metastasis from non-neuronal tumours in other organs
- Glial cells that are mitotically active throughout life
Gliomas grow rapidly - high malignant
- blood-brain barrier decreases effectiveness of cemotherapy
- treatment consists of radiation or surgery
Unmyelinated nerve fibres
Many CNS and PNS fibres unmyelinated
In PNS↔Schwann cells hold 1-12 small nerve fibres in surface grooves. Membrane folds once around each fibre
Conduction speed of nerve fibres
Speed at which signals travel along surface of nerve fibre depending on two factors
Diameter of fibre
Larger fibres have more SA and conduct signals more rapidly
Presence or absence of Myelin - Myelin further speeds signal conduction
Conduction speeds
- Small, unmyelinated fibres: 0.5 - 2.0 m/s
- small, myelinated fibres: 3-15.0 m/s
- large, myelinated fibres: up to 120 m/s
- slow signals sent to GIT where speed is less of an issue
- fast signals sent to skeletal muscles where speed improves balance & coordinated body movement
Electrophysiology of Neurons
How do neurons generate an electrical signal? How do they transmit meaningful signals/message to the next cell
Nerve growth factors
Protein secreted by a gland, muscle or glial cells and picked up by axon terminals of neurons. Prevents apoptosis (programmed cell death) in growing neurons. Enables growing neurons to make contact with their targets
Electrical potentials and currents
Basis of neural communication and muscle contraction
- Electrical potential - difference in concentration of charged particles between one point and another.
- Living cells are polarized and have a resting membrane potential
- Cells have more negative particles on inside of membrane than outside.
- Neurons have aprox 70mV resting membrane potential
Nerve electrical potentials and currents
- Electrical current↔flow of charged particles from one point to another
- Movements of ions (na+/k+) though channels in plasma membrane
- gated channels are opened or closed by various stimuli
- Enables cells to turn electrical currents on and off
Resting membrane potential
exists because of unequal electrolyte distribution between extracellular fluid and intracellular fluid
- RMP results from combined effect of three factors
- Ions diffuse down concentration gradient through the membrane
- plasma membrane is selectibely permeable and allows some ions to pass easier than others
- electrical attraction of cations/anions to eachother
POtassium (K+) has geratest influence on RMP
- Plasma membrane more permeable to K+ than any other ion
- leaks out until electrical charge of cytoplasmic anions attracts it back in adn equilibrium reached - no more net movement of K+
- K is aprox 40x as concentrated in ICF than ECF
- Cytoplasmic anions cannot escape due to size or chage - phosphates, sulfates, small organic acids, proteins, ATP and RNA
Membrane not very permeable to Na+ but RMP is slightly influenced by it
- Na+ is aprox 12x as concentrated in ECF as in ICF
- Some Na+ leaks into cell, diffusing down concentration and electrical gradients
- Na leakage makes RMP slightly less negative tahn if RMP was determined solely by K+
Na+/K+ pump moves 3na out for ever 2K it brings in
- Works continuously to compensate for Na+ and K+ leakage
- Requires significant use of ATP - 1ATP per exchange (70% of energy requirement of nervous system)
- Necessitates glucose and O2 supply to nerve tissue (energy needed to create resting potential)
- Exchange of 3+ve charges for only 2 -ve charges contributes +- -3mV to resting membrane potential of -70mV
Local POtentials
Changes in MP of neuron occurring at and nearby part of cell that is stimulated. Neurons respond to chemicals, light, heat or mechanical disturbance.
A chemical stimulant bind to a receptor of a neuron
- opens Na+ gate and allows Na+ to enter the cell
- Entry of positive ion makes cell less negative - DEPOLARISATION - Change in membrane potential towards 0 mV
- Na+ entry results in current that travels towards cell’s trigger zone
- Short range change in voltage is local potential
Properties of local potentials (unlike action potentials)
- Graded↔Vary in magnitude with stimulus strength - stronger stimuli open more Na+ gates
- Decremental↔weaken as spread from point of stimulation - voltage shift caused by Na+ inflow diminishes with distance
- Reversible↔if stimulation ceases, cell quickly returns back to normal RP - either excitatory or inhibitory
- Some neurotransmitters make MP more negative - HYPERPOLARISE it
- becomes less likely to produce a action potential
Action POtentials
Chase in membrane polarity produced by voltage-gated ion channels. Only occurs where have high density of voltage-regulated gates
- Neursoma (50-75 gates per um2) cannot generate AP.
- Trigger zone (350-500) gates per um2) Ap can be generated
- If excitatory local potential reached trigger zone and is still strong enough, it can open these gates and generate AP
Rapid up and down shift in membrane voltage involving a sequence of steps
- Arrival of current (local potential) at axon hillock depolarises membrane
- Local potential must reach threshold - critical voltage +- 55mV required to open voltage-regulated gates
- Neuron fires - voltage-gated Na+ channels open, Na+ enters and depolarizes cell - this opens more channels resulting in rapid positive feedback cycle as voltage rises
- As membrane potential rises above OmV, Na+ channels are inactivated and close. Voltage peaks about +35mV. Membrane now +ve on inside and -ve on outside
- Slow K+ channels open and outflow k+ repolarises cell due to +ve ICF
- k+ channels remain open for the time so that membrane is briefly hyperpolarised (more negative than RMP)
- RMP is restored as Na+ leaks in and extracellular K+ is removed by astrocytes
Characteristics of AP (Unlike local potential)
- Follows a all or none law
- if threshold is reached, neuron fires at maximum voltage
- if threshold is not reached, it does not fire
- non decremental↔does not weaken with distance
- irreversible↔once started, goes to completion and cannot be stopped
Signal conduction in nerve fibres
- Signal conduction in nerve fibres↔AP at trigger zone causes Na+ to enter axon and diffuse into adjacent regions, this depolarisation excites voltage-gated ion channels.
- Opening of channels results in new AP Allows Na+ diffusion to excite the membrane immediately distal
- Chain reaction continues until nerve signal reaches end of axon - Called CONTINUOUS CONDUCTION
- Myelinated fibres conduct signals with saltatory conduction - signals jump from node to node
- Nodes of Ranvier contain many voltage-gated ion channels, while myelin-covered internodes contain few.
- When Na+ enters cell its electrical fielf repels +ve ions inside cell. As +ve ions move away, +ve charge repels +ve neighbours, transferring energy down axon rapidly (conducting signal)
- Myelin speeds conduction by minimizing leakage of Na+ out of cell and separating inner +ve ions from attraction of -ve ions outside cell
- Signal strength does start to fade with the internode
- When signal reaches next node of Ranvier, it is strong enough to open voltage-gated ion channels and new AP occurs
Synapses
Nerve signals travels to end of axon. Triggers release of a neurotransmitter. Stimulates new wave of electrical activity in cell across synapse
- Synapse between two neurons↔First neuron in signal path is presynaptic neuron. Releases neurotransmitter
- Second neuron is postynaptic neuron
- Responds to neurotransmitter
Presynaptic neuron may synapse with…
- Dendrite
- neurosoma
- axon of postsynaptic neuron
To form:: - Axodendritic
- Axosomatic
- Axoaxonic synapses
Neurotransmitters
ELectrical synapses do exist
- Occur between some neurons, neuroglia, cardiac and single-unit smooth muscle.
- Gap junctions join adjacent cells↔Ions diffuse through gap junctions from one cell to next.
Advantage of quick transmission
No delay for release and biding of neurotransmitter
Dusadvantages of neurotransmitters
Cannot integrate informed and make decisions.
Structure of Chemical synapse
- Axon terminal of presynaptic neuron contains synaptic vesicals containing neurotransmitter
- Many vesicles dock on release sites on plasma membrane to release neurotransmitter
- Reserve pool of vesicles is located further away from membrane
- Post synaptic neuron membrane contains proteins that function as receptors and ligand-regulated ion gates
Surface anatomy of the brain
- Longitudinal fissure↔Deep groove that separates lobes of cerebral hemispheres
- Gyri↔thick folds of neural tissue
- Sulci↔shallow grooves
- Folding increases surface area
Embryonic development of the brain
↔Nervous system develops from ectoderm - outermost tissue layer of the embryo. Early in wk 3 dorsal midline of embryo thickens to form neural plate. As thickening progresses, neural plate sinks and edges thicken. Forms a neural groove with raised neural fold on each side
Neural fold fuse, creating a hollow neural tube by day 26. Lumen of neural tube becoems fluid-filled that will form ventricles of brain and central cananl of spinal cord
Neural crest
longitudinal column on each side of neural tube - ectoderm. Gives rise to two inner meninges, most of PNS and structure of skeletal, integumentary and endocrine system. By wk 4 the neural tube exhibits 3 primary vesicles and anterior end
- Forebrain↔prosencephalon
- Midbrain↔mesencephalon
- Hindbrain↔rhombencephalon
Week 5 of foetal development of brain
- Forebrain devides into
- Telencephalon - becomes cerebral hemispheres
- diencephalon - has optic vesicles that become retina of eye
- Midbrain remains undevided
- Hindbrain divides into
- Metencephalon
- Myelencephalon
The meninges
- The meninges↔Three connective tissue membranes surrounding brain and spinal cord. Lie between nervous tissue and bones of the skull and spianl column.
- Dura mater, arachnoid mater and pia mater.
- Protect brain and provide structural framework for blood vessles
The meninges
- The meninges↔Three connective tissue membranes surrounding brain and spinal cord. Lie between nervous tissue and bones of the skull and spianl column.
- Dura mater, arachnoid mater and pia mater.
- Protect brain and provide structural framework for blood vessles
Dura mater
↔Tough outer layer - inflexible, non distensible. Outer endosteal layer.
Inner meningeal layer
- Inner meningeal layer↔continues into vertebral canal and forms spinal dural sheath. Layers separate by dural sinuses, collect circulating venous blood
- Protection for brain. Dura mater is pressed closely against cranial bones - no epidural space.
- Not attached to bone except at foramen magnum, crista galli, sutures
