Together make center of face

Hard palate (front of mouth)

Sockets for teeth

Nasal Cavity (medial side forms the sides)

Maxillary Sinuses (lightens bones/risk of sinus headaches)

Posterior to maxillary bones

Posterior part of hard palate

Makes up posterior floor and part

of wall of nasal cavity

"cheek bones"

Forms zygomatic arch with temporal bones

Part of eye socket (lateral edge)

Curly then and fragile along

lateral nasal cavity-airway processing

Is the lower Jaw

Has sockets for teeth

Coronoid process for temporalis and

masseter muscles - chewing muscles

Mandibular Chondyle - Temporal - Mandibular Joint

INFANT SKULL

Fontanels

INFANT SKULL

Anterior Fontanel

(parietal/frontal junction)

- visible until two years

INFANT SKULL

Posterior Fontanel

(occipital/parietal junction)

- visible until two months

INFANT SKULL

Sphenoid Fontanel

(sphenoid/frontal/temporal/parietal)

-visible until three months

INFANT SKULL

Mastoid Fontanel

(temporal/occipital/parietal)

- Visible until one year

Helps spring the back (with ligaments and muscle)

Cervical, Thoracic, and Lumbar Curvatures

Pedicel - posteriorily connects body to laminae

Laminae - grows from pedicel to posterior spinous process

Transverse process - projects laterally for muscle attachment

Superior and inferior articulating facet - the joint between the vertebrae.

Cervical Vertebrae

C1 - "atlas" - joint with base of skull on occipital

    condyles

C2 - "axis" - tooth-like dens - first rotational pivot

    of the spinal cord

C3 to C7 - have transverse foramina - arteries for

    brain

C2 to C7 - posterior process is bi-forked 

T1 to T 12 (top to bottom)

Transverse processes exhibit an additional articulating set of facets for ribs

L1 - L5

"moose head shaped"

Tailbone

Four fused vertebrae

Easily broken

12 pairs (flattened and curved) - protect heart,

   lung, and kidneys

Ribs 1-7: articulates with sternum "true ribs"

Ribs 8-12: articulates with cartilage "false ribs"

Head (articulates with body of vertebrae)

Tubercle (T1-T7) (articulates with transverse process)

Costal Cartilages connects to sternum

Sternum

Breastbone

Fused from three bones:

Manumbrium (top)

Body (middle)

Xyphoid Process (pointed tip-bottom)

Sternum acts as key site of blood

cell formation in adults.

stabilizes the shoulder with scapulae

weak - very breakable

Posterior Surface: Spine

Supraspinus fossa / infraspinus fossa for muscle movement

Acromion process (tip of shoulder) articulates with clavicle

Glenoid fossa (cavity) - joint surface for humerus

Coracoid process - muscle attachment site

Head acts as part of shoulder joint

Condyles - contact site for elbow joint

Capitulum (lateral)

Trochlea (medial)

Epicondyles - med/lat = muscle attachment sites

Humerus continued

Fossas and Necks

Olecrannon fossa - accepts olecrannon from ulna

Coronoid fossa - accepts point from ulna

Anatomical neck - between head and shaft

Surgical neck - common break point in kids

Thumb side of forearm (anatomical position)

Allows roation of forearm

Head engages capitulum

Articulates with ulna for rotation

Articulates with wrist

Connects to wrist ligaments

Ulna

Proximal end articulates with humerus

Trochlear notch

(mates with olecranon and coronoid processes)

Head end - articulates with wrist

Styloid process - ligament attachments

Wrist

Metacarpal Bones

Phalanges

Carpal Bones (8)

Palm (5)

2 bones in polex (thumb)

3 bones in fingers 2-5

Articulates with sacrum (Sarcoiliac joint)

Acetabulum - articulates with femur

Pubic Notch (Female > Male)

Lesser pelvis

(bowl from pelvis to sacroiliac joint

to coccyx larger in females)

Greater pelvis

(upper hip "wings" flatter in females)

Ilium

(with crest)

Ischium

Posterior obturator formane & ischial spine

Pubis

Anterior obturator foramen

Head (ball that articulates with acetabulum)

Fovea capitis (ligament attachment and blood supply)

Neck Constriction between shaft and head

Greater & Lesser trochanters (muscle attachment sites)

Medial/Lateral condyles = joint surface

Medial/Lateral Epicondyles-muscles of thigh and foreleg attach

A "sesamoid" bone

Assists quadriceps muscles

Medial/lateral condyles

Articulates with femur

Intercondylar eminence

ant/post cruciate ligaments

Distal end & medial malleolus

 Ankle Articulation and Ankle ligaments attach

Little toe side

Head articulates with tibia

Lateral malleolus ankle ligaments attach

Tarsus - (7 tarsal bones)

Talus

Articulates with tibia

Calcaneous

Heel bone - carries body weight

5 Metatarsals

Phalanges: 2 bones for halux (big toe)

3 for toes 2-5

1. Hematoma (clot) at break

2. Spongy bone forms around invading blood vessels and fibrocartilage forms

3. Massive bony callus replaces fibrocartilage

4. Osteoclasts remodel and remove excess bone

Three Types of Joints

Fibrous

Cartilagenous

Synovial

1. Syndesmosis - long fibrous sheet

    (amphiarthrotic = limited movement)

    Ex. Interosseus of radius/ulna or tibia/fibula

2. Suture - @ fusion of skull bones

    Synarthrotic = immobile

3. Gomphosis - tooth to socket

    Ex. Periodontal ligament (synarthrotic)

1. Synchondrosis - hyaline cartilage attaches bones

    Ex. Growth plate and ribs to manubrium

2. Symphysis - hyaline with fibrocartilage coat

    (Amphiarthrotic)

    Ex. Intervetebral disk and symphysis pubis

Synovial Joint

Five parts of the Joint

Diarthrotic (highly mobile) with hyaline cartilage

Parts

1. Articular Cartilage

2. Synovial fluid

3. Joint Capsule

4. Meniscus

5. Bursae 

Articular Cartilage

Synovial fluid

Hyaline coat of both surfaces

Lubricant (0.5 ml)

Inner - synovial membrane (forms inner seal for

          fluid)

Outer - tough fibrous capsule and embedded

           ligaments

Meniscus

Bursae

Fibrocartilage pad (ex. Knee)

Pouch-like extensions of synovial membrane

under certain key tendons

Ex. Supra, pre-, and ingrapatellar bursae of knee

1. Ball & Socket (hip/shoulder) - rotate

2. Condyloid (oval/eliptic surface) - bend and rotate

3. Gliding (vertebral facets) - slide along each other

4. Hinge (elbow/knee) - rotates in one plane

5. Pivot (skull/atlas/axis) - rotates around one axis

6. Saddle (convex/concave surfaces - multiplanar

              motion: thumbs with tarsal

Flexion

Extension

Hyperextension

Decrease Joint Angle (elbow curl)

Increase Joint Angle (straighten elbow)

Extend past anatomical position

(sometimes painful)

Dorsiflexion

Plantar flexion

Abduction

lift foot

point foot downward

move away from midline

(lift arm sideways)

Adduction

Rotation

Circumduction

Move toward midline

(let arm fall)

move around an axis

(twist arm)

move in a circular path

Supination

Pronation

Eversion

Palms Up

Palms Down

Sole Outwards 

Inversion

Protraction

Retraction

Sole inwards

(cause of sprained ankles)

Thrust Outward

(jaw)

Pull item back

(jaw)

Depression

Elevation

Make Lower

Make Higher

Sprains - torn ligaments in joints.  Usually also see damagaed cartilage in serious sprains.

Arthritis - painful inflamed joints

Over _____ types of arthritis.

Two main types:

100 types

Osteoarthritis - degenrative disease of articular cartilage that cause weakening and disintegration

Rheumatoid arthritis - autoimmune condition whereby your immune system attacks your joints

Synovial joint example:

The Knee

Complex design but poorly constructed (greater mobility = greater risk of injury)

Hinge joint (but rotates when bent)

Involves medial and lateral condyles of both tibia and femur

Two that prevent side to side flexing:

Tibial Collateral (medial)

Medial tibial condyle to medial femoral condyle

Fibular Collateral (lateral)

lateral fibular condyle to lateral femoral condyle

Two Stop Rotaion and Anterior-Posterior Slip

Anterior cruciate

anterior tibial intercondylar area to

 posterior lateral femoral condyle

Posterior Cruciate

posterior tibial intercondylar area to

medial femoral condyle

Synovial Joint Example:

The Shoulder

Muscles hold shoulder together

(almost no major ligament)

Benefit=increased mobility (greater risk of damage)

Coracohumeral ligament

(at top of shoulder)

Glenohumeral ligament

(in joint capsule wall)

Transverse humeral ligament

(forms passageway for biceps tendon)

Muscular System

Purpose

OUtermost Layer

Dense Connective tissue

Collects connectives from muscle fibers to form tendon on to periosteum of a bone

Or contacts aponeurosis (fiber layer between muscles)

Covers muscle fibers and muscles

Three Layers of Connective Tissue

From smallest to greatest

Endomysium

Perimysium

Epimysium

surrounds muscle (collection of fascicles and connected tissue)

- connects to fascia

Multi-nucleated

(cells fuse during development)

Membrane of cell = "sacrolemma"

Cytoplasm contains mitochondria and nuclei

Each muscle fiber contains:

Myofibril = bundels of contractile elements

Myofibril constructed in short repeated structures (sacromeres) built of two proteins -

myosin and actin

1. Begins and ends with a zig-zagged "Z line"

2. I Bands and A Bands

3. H zone and M line

I Bands

&

A Bands

I bands: thin actin filaments enter sacromere from

             each z line. Long and thread-like. Actin

             forms fromework for myosin to pull on

A bands: thick myosin fibers

 -Connect to Z with protein ("titin or connectin")

 -Myosin subunits have small protein regions that

  pull on actin.

I bands and A bands of sacromere

must overlap for contraction.

H Zone

&

M Zone

H Zone: Central region of A band between ends of I bands = unused myosin

M Zone: Connection proteins between myosin fibers

Tropomyosin and Troponin

Regulate availability of actin binding sites for myosin in a Ca²⁺ dependent manner

In resting fibers, free cytoplasmic Ca²⁺ is very low

Troponin (globular) and tropomyosin (thread-like) block actin binding sites for myosin

 Sacroplastic reticulum

Transverse tubules (T-tubules)

Sacroplastric Reticulum:

 (related to ER) - membranous passageways that store calcium

Transverse tubules (T-tubules):

membrane passageways that extend in from sarcolemma (cell membrane) to the interior

Enlarged sarcoplastic reticulum (cisternae) touches T tubules.

During Muscle Contraction..

A band fibers pulls itself over

 I band fibers during contraction

So during contraction:

I bands get smaller (less unbound actin)

H zones get smaller (less bound myosin)

 Begins with electrical nerve impulse from central nervous system (spinal motor neurons)

Impulse reaches the axon terminal of the neuron across the synaptic cleft from the motor end plate (neuromuscular junction)

Motor end plate has massive sarcoplastic reticulum with mitochondira and nuclei

One muscle fiber gets input from one neuron

One neuron innervates multiple fibers (=motor unit)

Each neural impulse:

1. Causes exocytosis of thousands of vesicles that contain a small aqueous chemical cue, acetylcholine

2. Acetylcholine drifts across the synaptic clept and binds to receptors at the motor end plate

3. Receptors trigger an electrical impule in the muscle fiber triggering contraction

4. An extracellular enzyme (acetylcholinesterase) destroys the leftover acetylcholine thus stopping contraction.

5. Muscle impulse enters the T-tubules and cuases release of Ca²⁺ from sarcoplastic reticulum

  -Ca²⁺ pumps keeps cytoplasmic Ca²⁺

    concentration normally low.

Step 4 of Muscle Contraction

Contraction of Sarcomere (+heat prod.)

A. Ca²⁺ causes the troponin-tropomyosin configuration change exposing actin.

B. Myosin head (pre-cocked) binds to actin via cross-bridges

C. Myosin head then changes its shape and pulls

D. ATPase site on myosin head uses energy from ATP to cause myosin cross-bridges to break when ATP binds to it

E. Then the ATP is hydrolyzed (ADP + Pi -> heat) and myosin recocks the heat

F. Myosin head then rebinds another actin subunit and repeats the process as long as Ca²⁺ levels are high and ATP is available.

G. Rigor mortis happens after death because no more ATP is made to break actin/myosin cross-bridges

Starts with end of nerve impulse and acetylcholine destruction by acetylcholinesterase

Ca²⁺ levels fall (Ca²⁺ pumped into sarc reticulum)

ATP binds to myosin (but not used for energet yet- no Ca²⁺!)  Cross-bridges break and tropomyosin reblocks actin and ATP is cut and myosin gets recocked.

Actin and myosin fibers slide past each other and waits for next muscle impulse.

Muscle has only limited free ATP from Mitochondria

ADP + PO4 (pi) ? ATP using PO4 from creatine phosphate storage pool as a short-term fix.

  During resting, mitochondria makes excess ATP

  The cell transfers a PO4 from ATP to creatine for

     later (via enzyme "creatine phosphokinase")

one minute of walking or 6 sec of sprinting.

Then depend on mitochondrial respiration

and/or glycolysis for ATP Production.

Metabolism

Early steps of Kreb cycle are anaerobic.

Glucose => 2 pyruvate => 2 ATP

Then oxygen (aerobic) converts 2 pyruvate

 to 34 ATP more at mitochondria.

Hemoglobin in blood (oxygen from lungs)

Myoglobin in muscle - temporary oxygen

When metabolism uses up available oxygen the cell uses anaerobic metabolism to try to maintain ATP via lactic acid production

Pyruvate gets converted to - lactic acid so glycolysis can continue

Prolonged oxygen debt causes significant increase in lactic acid levels (lowered pH) = "the burn" or later muscle pain.

Muscle Fatigue

Can occur psychologically

Ion imbalances (dehydration)

Reduced blood flow (muscle starvation)

Lactic acid build up (depends on physical conditioning of individual)

Often cramp - prolonged involuntary contraction

Muscle fiber contracts only after the stimulating impulse reaches a minimum voltage = "threshold stimulus"

Muscle fiber either contracts or does not - ALL or NOTHING

Normal neuromuscular junction impulse is sufficient to trigger a contraction of the fiber.

Measuring muscle responses

Myograms are used to study muscle contraction

Once stimulus exceeds threshold - fibers in the motor unit will contract and relax

the contraction and relaxtion

a delay between the stimulus and contraction = latent period

caused by diffusion of transmitters at cleft and diffusion of Ca²⁺ inside muscle

(treppe)

a muscle fiber can increase its contraction strength with successive stimuli

the effect may be due to incomplete calcium pumping out of cytoplasm

Example: Tossing pillows and then tossing books

As the load is increase on a muscle, additional motor units can be brought

Power muscles (ex. quadriceps) have motor units with thousands of fibers

Finesse muscles (ex. superior rectus muscles) have comparatively few fibers per unit = more control

 (1 neuron per 10 mucle fibers)

Small motor units are active first

Larger power units become active a little later

Continuous muscle contraction consists of many motor units becoming active (some relaxing and contracting) but maintaining a summed force.

Muscle tone - resting contractions of a few fibers (posture)

Isotonic

Myofibrils shorten producing tension

Isometric

Produce tension without shortening

Slow Twitch: Myoglobin Rich = type I (red fiber)

Makes ATP fast enough to supply needs via oxidative metabolism for long term use (posture muscles)

Fast Twitch: Gylcolytic = type IIa (white fiber)

Consumes oxygen fast and switches to glycolysis making it easily fatigued (most muscles)

Intermediate: Type IIb, shares red and white fiber properties (fast twich with oxidative metabolism leading to ATP production)

Smooth Muscle and Types of Smooth Muscle

fibers are thin and "randomly" oriented into the cell

Multiunit Smooth Muscle

Contracts after nervous system impulse

Visceral Smooth Muscle

Autorhythmic

Acetylcholine stimulates motor end plate

Ca²⁺ then released from sacroplastic reticulum

Ca²⁺ binds to the enzyme "calmodulin"

Calmodulin activates the actin/myosin system

Striated fiber with 1 nucleus, actin and myosin

Ends of fibers posses a special structure

   - Intercalcated disks: complex membrane

      junctions that function like gap junctions

   - Whole networ: syncytium (one tissue acting as

       a whole)

System contracts like skeletal muscle fiber except extracellular Ca²⁺ plays a key role in triggering contraction

Skeletal Muscles

Origin

Insertion

Origin: the "immovable" connection - anchor

Insertion: movable connection

   - Muscles may have 1 origin and 1 insertion or

     more of both

Agonist

Antagonist

Agonist: promise mover (one the predominately

             causes the motion)

 - Synergists: nearby muscles assisting with motion

Antagonist: opposes motion

Made of Two Muscles: Occipital and Frontalis

O: Occipital Bone.

I: Skin and muscles of forehead

A: Elevates eyebrows

Eyes: Obicularis Oculi

O: Maxillary and Frontal bones

I: Skin around eye

A: closes eyelids

O: Zygomatic Bone

I: Orbicularis oris muscle

A: Elevates corners and draws

mouth laterally = smile!

O: Outer surfaces of maxilla and mandible

I: Orbicularis oris muscle

A: Compresses cheek

Platysma

O: Fascia of upper chest

I: Lower border of mandible

A: Depresses mandible, tenses neck skin

O: Lower border of zygomatic arch

I: lateral surface of mandible

A: elevates jaw (mastication)

O: teporal bone

I: coronoid process of mandible

A: elevates jaw (mastication)

O: Sphenoid, palatine, maxillary bones

I: Medial surface of mandible

A: Lateral motion of mandible

O: Sphenoid

I: Anterior surface of mandibular chondyle

A: Lateral Motion of mandible and protracts jaw

O: Sternum and Clavicle

I: Mastoid process

A: One side rotates head,

both sides pull head forward and down

O: spinous processes of cervicle

and thoracic vertebrae

I: Occipital Bone

A: One side rotates head, both sides pulls head back and extend neck

O: Cervical vertebrae processes

I: Occipital Bone

A: One side rotates; both sides extends neck

Causes negative pressure in chest when it contracts =inhale

O and I: left and right inferior ribs and vertebrae

External Intercostals

Internal intercostals

lift and expand ribs (inhale)

compress ribs (active exhale)

O: Pubic bone (and symphysis)

I: Xiphoid and costal cartilages

A: Flexes vertebral column

O: Outer surface of ribs

I: outer lip of iliac crest, linea alba

A: compresses abdomen and rotates lumbar region

O: Iliac crest

I: Costal cartilages, linea alba

A: Compresses abdomen and rotates lumbar region

O: Costal Cartilages

I: Linea Alba and Pubis

A: Flexes vertebral colum and

increase abdominal pressure

Levator Ani

O: Pubis and Ischial Spine

I: Coccyx

A: Prevents pelvic organs from descending under pressure

O: Ischial Spine

I: Sacrum and Coccyx

A: aids levator ani

Bladder Sphincter

O: Pubis and ischium margins

I: Meet with contralateral fibers (i.e. from other side)

A: Prevents urination

External anal sphincter

Location: Rectum and anal canal

A: Prevents Defecation

O and I: Perineal body and coccygeal ligament

O: Ischial Tuberosity

I: Pubic Arch

A: aids in penis or clitoris erection

O: "central tendon" of urogenital diaphragm

I:

Males: Urogenital diaphragm and penlile fascia

Females: pubic arch and clitoral root

A:

Males: expels last urine and semen

Females: compresses vaginal orifice (keegle exercise)

O: Outer surface of upper ribs

I: Ventral surface of scapula

A: Pulls shoulder forward and down

O: Occipital bone and spinous process of cervicle and thoracic vertebrae

I: clavicle and scapula

A: Elevates, depresses, adducts, and rotates scapula

O: Cervical Vertebral transverse process

I: Doral-medial margin of scapula

A: elevates scapula

O: Thoracic vertebral spinous processes

I: Medial border of scapula

A: elevates and adducts shoulder

O: clavicle, sternum, costal cartilages

I: Intertubercular groove of humerus

A: flexes, adducts, rotates humerus medially, flexes shoulder (throwing)

O: Spines of sacral, lumbar and lower thoracic vertebrae, iliac crest, and lower ribs

I: Intertubersular groover of humerus

A: Extends shoulder, adducts and rotates humerus medially and down "swimming muscle"

O: Acromium process, scapular spine, clavicle

(3 heads => different motions)

I: Deltoid tuberosity of humerus

A: Abducts, extends, flexes humerus

(skips humerus)

O: coracoid process of scapula

I: radial tuberosity

Action: flex forearm at elbow

O: Anterior shaft of humerus

I: Coronoid process of ulna

A: Flex forearm at elbow

O: Distal lateral end of humerus

Insert: lateral surface of radius proximal to stylus

A: flex forearm at elbow

Triceps brachii

O: Tubercle above glenoid cavity and lateral and medial surfaces of humerus

I: Olecrannon process of ulna

A: Extends forearm at elbow

O: Medial epicondyle and coronoid process of ulna

I: Lateral surface of radius

A: Pronates forearm and hand

O: Distal end of ulna

I: Distal end of radius

A: pronates forearm and hand

O: Lateral epicondyle of humerus and ulnar crest

I: Lateral surface of radius

A: rotates forearm laterally

Anterior Compartment of Forearm

Wrist flexors go through carpal tunnel between flexor reticulum and carpals

Superficial layer (most originate at humerus medial epicondyle)

O: Medial epicondyle of humerus

I: Base of 2nd and 3rd metacarpals

A: Flexes/abducts wrist

O: Medial epicondyle of humerus and olecranon

I: carpals (pisiform...???

A: Flexes/adducts wrist

O: Distal end of humerus

I: Base of 2nd metacarpel

A: Abducts/extends wrist

O: Lateral epicondyle of humerus

I: Base of 2nd and 3rd Metacarpals

A: Abducts/extends wrist

O: Lateral epicondyle of humerus

I: Base of 5th metacarpal

A: extends/adducts wrist

O: Medial epicondyle of humerus, coronoid of ulna, radius

I: Tendons of Finger

A: Digits at Metacarpal, phalangeal and interphalangeal joint (also flexes wrist)

(Deep to FDS)

O: Anterior surface of ulna

I: Bases of distal phalanges of fingers 2-5

A: Flexes fingers

O: Lateral epicondyle of humerus

I: Posterior surface of phalanges 2-5

A: Extends fingers

O: Sacrum, coccyx, and posterior surface of ilium

I: Posterior surface of femur and thigh fascia

A: Extends hip (stance and motion)

O: Lateral Surface of ilium

I: Greater trochanter of femur

A: Abducts, medially rotates

O: Lower edge of symphysis pubis

I: Medial surface of tibia (skips femur)

A: Adducts thigh/flexes knee

adductor femoris in cats 

O: Ischial tuberosity

I: Posterior surface of femur

A: Adducts/flexes/laterally rotates thigh

O: Anterior Superior Iliac Spine

I: Medial Surface of Tibia

A: Flexes Hip and Thigh, rotates thigh laterally

The quadriceps femoris

4 muscles all insert on patellar tendon to drive patellar ligament to tibia

O: Iliac Spine and acetabular margin

I: Patellar tendon

A: Extends leg

O: Greater trochanter and posterior surface of femur

I: Patellar Tendon

A: Extends leg

O: Medial surface of femur

I: Patellar Tendon

A: Extends Leg

Vastus Intermedius

Under rectus femoris

O: Anterior and Lateral surfaces of femur

I: Patellar Tendon

A: Extends Leg

Most Lateral

O: Ischial Tuberosity

I: Head of Fibular and Tibial Lateral condyle

A: Flexes and laterally rotates leg and extends thigh

O: Ischial Tuberosity

I: Medial Surface of Tibia

A: Flexes and laterally rotates leg and extends thigh

O: Lateral condyle and lateral tibial surface

I: Tarsal Bone and First Metatarsal

A: Dorsiflex ankle, inverts foot

O: Femoral medial and lateral condyles

I: Posterior edge of calcaneus

A: Plantar flex foot, flexes knee

Last push when running or jumping

O: Head and shaft of fibula, posterior surface of tibia

I: Posterior edge of calcaneus

A: Plantar flexes foot at ankle

Neurons - informations processing and transmission of electrical signals

    Nerve impulse: basic unit of information

                               = action potential 

Glia (neuroglia) - support, protects, and nurses the neurons

Cell body or perikaryon

Houses Cellular Machinery

Nucleus, nucleolus, mitochondria, golgi bodies, Nissl body (ER), etc.

Long slender cellular process from soma

Carries elctrical impulse away from cell ("transmitter")

Carries biochemicals from soma to synapse

Multiple collaterals branch off of axon

One too many slender processes from soma

Receives information from sensory structure or other neuron ("receiver")

Synapse

Synaptic Cleft

Specialized structure at end of axon

Chemically transmits nerve impulse to target tissue with neurotransmitters (smal mol wt. chemicals)

Gap between synaptic terminal and target tissue (approx. 20 nm in width)

Trigger Zone

Triggers nerve impulse if depolarized (must reach "threshold": minimum voltage needed to create a neural impulse [action potential])

Schwann Cells (peripheral) and

Oligodendrocytes (central)

Glial cell that insulates axon (increases impulse velocity???)

"Conduction velocity" - speed at which impulse moves along axon

Wrap axon in insulation - looks like string of sausages ( 1 schwann cell/"sausage" )

Myelinated vs. Un-myelinated

Node of Ranvier

Fast vs. Slow

Gaps between schwann cells are critical to increasing impulse conduction velocity

Peripheral Nervous System

Division of PNS

Cranial Nerces (exit brain directly)

Spinal nerves from spinal cord to body

Somatic NS: runs voluntary motion

 Autonomic NS: Runs viscera