ANAPHY (MIDTERM)
SKELETAL SYSTEM
1.) Functions of Bones
a. Support- Bones provide a framework that
supports the body and cradles its soft organs.
b. Protection- The fused bones of the skull
protection the brain.
c. Movement- Skeletal muscles, which attach to
bones by tendons, use bones as levers, to move
the body and its parts.
d. Mineral and growth factors storage- Bones is
reservoir for minerals, mostly importantly
calcium and phosphate.
e. Blood cell Formation- Most blood cell
formation, or hematopoiesis occurs in the
marrow cavities of certain bones.
4.) Bone Structure
4.1 Bone Tissue
1. Osteocytes (cells) are found in the matric of
calcium phosphate, calcium carbonate and
collagen.
2. Compact Bone- contains haversian system.
3. Spongy bone- without haversian systems but
red bone marrow is present.
4. Articular cartilage- which is smooth and
found on joint surface.
5. Periosteum- made of fibrous connective
tissue membrane which anchors tendons and
ligaments and contain blood vessels that enter
the bone.
4.2 Gross structure of a typical long bone
2.) Bone Development and Growth
 Ossification is the process of bones
formation.
 Ossification begins during the sixth or seven
week of embryonic life.
 2 types of ossification:
1.) Intramembranous- bones forms directly
on or within loose fibrous connective tissue
membrane.
2.) Endochondral- bone form within the
hyaline cartilage.
3.) Factors that affect bone growth and
maintenance
a. Heredity- genes contribute to genetic
potential for height.
b. Nutrition- part of the bone matrix includes
calcium, phosphorus and protein.
c. Hormones- concerned with cell division,
protein synthesis, calcium metabolism and
energy production.
d. Exercise or stress- weight bearing bones
must bear weight or they will lose calcium and
become brittle.
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Disaphysis (shaft) of a long bone
Medullary cavity- within the diaphysis.
Endosteum- a thin layer of connective
tissue that lines the medullary cavity.
Epiphysis- either end of the diaphysis
consisting of spongy bone surrounded by
compact bone.
Epiphyseal plate- separates the diaphysis
and epiphysis.


Epiphyseal line- replaces the plate when
the bone growth is completed.
Periosteum- a dense regular connective
tissue covers the bone and is the site of
tendon-muscle attachment and diameter
bone growth(widening)
6.1 Skull
4.3 Bone Surface Markings


These are structural features visible on the
surfaces of bones.
Two major types:
1.) Depression and Openings – form a joints or
allow the passage of soft tissues such as blood
vessels, nerves, ligaments, and tendons.
2.) Process – are projections or outgrowths that
form joints or attachment points for connective
tissue such ligaments and tenonds.
5. Classification of Bones
a. Long – arms, legs; shaft is the diaphysis
(compact bone) with marrow cavity containing
yellow bone marrow (fat); ends are epiphyses
(spongy bone)
b. Short – wrists, ankles (spongy bone covered
with compact bone).
c. Flat – ribs, pelvic bone, cranial bones (spongy
bone covered with compact bone).
d. Irregular – vertebrae, facial bones (spongy
bone covered with compact bone).
6.) Divisions of the Skeletal System
-The adult human skeleton contains of 206
named bones. These bones are grouped into
two principal divisions; axial skeleton (80 bones)
and appendicular skeleton (126 bones).
6.1 Axial Skeleton
 The axial skeleton forms the longitudinal
axis of the body.
 Its principal subdivision are the skull,
vertebral column, and bony thorax. It
provides support and protection.
a. Cranium
 The cranium forms the vault and base of
the skull, which protect the brain, eyes and
ears.
 The eight bones of the cranium include the
paired parietal and temporal bones and the
single frontal, occipital, ethmoid and
sphenoid bones.
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Frontal bone – forms the forehead.
Parietal bone – extend to the side of skull
Occipital bones – curves to form the base
of the skull.
Temporal – located on the sides.
Sphenoid – complete sides and contributes
to orbits.


Ethmoid – part of the orbital wall and
contributes to nasal septum.
The immovable joints between these bones
are called sutures.
6.1.1.1 Sutures
 Are joints in the cranium
 The names reflects on bones they unite.
 These are the following sutures; sagittal,
lambdoid and squamous.
6.1.1.2 Fontanels
 Are soft spots in the cranium of the
newborn
 There are also six large membranous are
called fontanels (“soft spots”), that permit
the skull to undergo changes in shape
(molding) during childbirth.
 These also permit rapid growth of the brain
during infancy.
 Ossification of these fontanels is normally
complete by 20 to 24 months.
 The major fontanels are the anterior,
posterior, anterolateral and posterolateral.
6.1.2 Facial bones
 The facial skeleton provides openings for
the respiratory and digestive passages and
attachment points for facial muscles.
 The facial bones make up the face (maxillae,
palatine, mandible, zygomatic, lacrimal,
vomer, nasal, and inferior nasal concha)
a. mandible – the lower jaw.
b. maxillae – the upper jaw and anterior
portion of the hard palate.
c. palatine bones – posterior portion of the
hard palate and floor of the nasal cavity.
d. zygomatic bones – checkbones.
e. lacrimal bones – lies between ethmoid and
maxilla bones.
f. nasal bones – form bridge of nose.
g. vomer – helps from nasal septum.
6.1.2.1 Paranasal sinuses
 Air cavities in the maxillae, frontal,
sphenoid and ethmoid bones.
 They lighten the skull and provide
resonance for voice.
6.2 Ear Ossicles (malleus, incus, stapes)
-Three auditory bones in each middle ear cavity
transmit vibrations for the hearing process.
6.3 Hyoid bone
-supports in the neck by ligaments.
-serves as an attachment point for tongue and
neck muscles.
6.4 Vertebral column
- include 24 movable vertebrae; 7 cervical, 12
thoracic and 5 lumbar and the sacrum and
coccyx.
-The vertebrae support trunk and head,
encloses and protects the spinal cord in the
vertebral canal.
-Discs of fibrous cartilage absorb shock
between the bodies of adjacent vertebrae, also
permit slight movement.
-The primary curvatures of the vertebral column
are the thoracic and sacral; the secondary
curvatures are the cervical and lumbar.
- Curvatures increases spine flexibility.
- consists of one clavicle and one scapula. The
pectoral girdles girdles attach the upper limbs
to the axial skeleton.
6.5 Rib Cage or Thoracic Cage

The bones of the thoracic cage include the
12 pairs, the sternum, and the thoracic
vertebrae.
 The thoracic cage protects the organs of the
thoracic cavity and upper abdominal organs
from mechanical injury and is expanded to
contribute to inhalation.
6.5.1 Sternum
- consist of manubrium, body and xiphoid
process
6.5.2 All ribs articulate with thoracic vertebrae.
 Vertebro-Sternal Rib/True Ribs (first seven
pairs) articulate directly with
sternum(breast bone) by means of costal
cartilage.
 Vertebro-Chondral Rib/False Rib (next
three pairs) articulate with 7th costal cart.
 Floatin Ribs (last two pairs) do not
articulate with the sternum.
7. Appendicular Skeleton
 The appendicular skeleton consists of the
bones of the pectoral and pelvic girdles and
the limbs. (extremities)
 It allows mobility for manipulation and
locomotion.
7.1 Pectoral Girdle
7.1.1 Clavicles (collarbone)
-The clavicles hold the scapulae laterally away
from the thorax. The sternoclavicular joints are
the only attachment points of the pectoral
girdle to the axial skeleton.
7.1.2 Scapulae
- The scapulae articulate with the clavicles and
with the humerus bones of the arms.
7.2 Upper Extremities (upper limbs)
-Each upper limb consists of 30 bones and is
specialized for mobility.
7.2.1 Arm/Forearm/Hand
 Composed solely of the humerus (upper
arm) articulates with the scapula and the
ulna (elbow).
 The forearm is composed of the radius and
ulna articulate with one another and with
carpals;
 The hand consists of the carpals(wrists),
metacarpals(hand)
 Phalanges (fingers)
!! A strong pelvis floor helps you to maintain a
good bladder and bowel control. It is also
important in good sexual functions.
7.4 Lower extremities (lower limb)
-Bone of the lower extremities provide
frameworks of the thigh, leg and foot.
7.4.1 Femur
a. the single bone of the thigh.
b. the largest, longest, strongest bone of the
body.
7.3 Pelvic Girdle
 it is a heavy structure specialized for
weight bearing, is composed of two hip
bones that secure the lower limbs to
the axial skeleton.
 Each hip bone consists of three bones:
ilium, ischium and pubis.
 The acetabulum occurs at the point of
fusion.
7.4.2 Patella
a. a triangular sesamoid bone enclosed in the
(quadriceps) tendon that secures the anterior
thigh muscles to the tibia.
b. protects the knee joint anteriorly and
improves the leverage of the thigh muscles
acting across the knee.
Pelvic Structure and childbearing. The
male pelvis is deep and narrow with
larger, heavier bones than those of the
female. The female pelvis, which forms
the birth canal, is shallow and wide
7.4.5 Ankle and Foot
a. The ankle and foot consist of the tarsal,
metatarsal and five phalanges.
7.4.3 Tibia
a. The tibia is located on the medial side of
the leg.
b. It has medial and lateral condyles, tibial
tuberosity, anterior crest, medial malleolus.
c. It articulates with the talus of the ankle.
8. Joints or Articulations
 Joints are sites where bones meet.
 Their functions are to hold bones together
and to allow various degrees of skeletal.
!! not all skeletal has the same movement
* Cavity – space in the bone.
7.4.4 Fibula
a. It is located on the lateral side of the tibia.
b. It has a head and lateral malleolus that
articulates with the ankle but does not bear
body weight.
8.1 Classification based on
a. Amount of movement
 Synarthrosis – immovable.
 Amphiarthrosis – slightly movable.
 Diarthrosis – freely movable.
b. Joints are classified structurally as fibrous,
cartilaginous, or synovial.
Fibrous Joints – occur where bones are
connected by fibrous tissue; no joint cavity is
present. Nearly all fibrous joints are
synarthrotic.
In cartilaginous Joints – the bones are united
by cartilage; no joint cavity is present.
All synovial Joints (strengthen the bones) –
have a joint cavity enclosed by a fibrous capsule
lined with synovial membrane and reinforced
by ligaments; articulating bone ends covered
with articular cartilage; and synovial fluid in the
joint cavity.
8.2 Structure of Synovial Joints – all diarthroses
have similar structure.
 Articulatar Cartilage – smooth on joint
surface.
 Joint Capsule – strong fibrous connective
tissues steath (membrane) that encloses the
joint.
 Synovial Membrane – lines the joint
capsule; secretes synovial fluid that
prevents friction.
 Bursae – sacs (storage) of synovial fluid that
permit tendons to slide easily across joints.
8.3 Movements Allowed by Synovial Joints
 The insertion (movable attachment) moves
toward the origin (immovable attachment).
 Three common types of movements can
occur when muscles contract across joints;
a. gliding movements
b. angular movements (which include flexion,
extension, abduction, adduction, and
circumduction).
c. rotation
 The six major categories of synovial joints
are
a. plane joints (nonaxial movement).
b. hinge joints (uniaxial)
c. pivot joints (unaxial)
d. rotation (permitted)
e. condlyd joints (biaxial with angular
movements in two planes)
f. saddle joints (biaxial, like condyloid joint, but
with freer movement)
g. ball-and-socket joins (multiaxial and
rotational movement)
9. Common Bone and Joint Disorders
 Sprains – involve stretching or tearing of
joint ligaments.
 Dislocations – involve displacement of the
articular surfaces of bones.
 Bursitis and Tendonitis – are inflammations
of a bursa and tendon steath, respectively.
 Arthritis – is joint inflammation or
degeneration accompanied by stiffness,
pain, and swelling.
 Acute forms generally result from
bacterial infection.
 Chronic forms include osteoarthritis,
rheumatoid arthritis and gouty arthritis.
 Osteoarthritis – is a degenerative condition
most common in the aged.
 Rheumatoid Arthritis – the most crippling
arthritis, is an autoimmune disease (it
attacks its own cells) involving severe
inflammation of the joints.
 Gouty Arthritis (gout) – is a joint
inflammation caused by the deposit of
urate salts in soft joint tissue.
 Fracture – is cracking or breaking of a bone.
 Slipped disc – is herniation of the nucleus
pulposus of an intervertebral disc.
 Kyphosis – is an exaggeration of the lumbar
curve of the vertebral column.
 Scoliosis – is a lateral bending of the
vertebral column.
 Osteomyelitis – is an infection of the bone,
usually caused by Staphylococcus aureus.
 Rickets and Osteomalacia – are disorders in
which bones fail to calcify.
MUSCULAR SYSTEM
1. An overview of Muscle Tissue
 Skeletal Muscle – attached to and moves
the bony skeleton voluntarily.
 Cardiac muscle – forms the walls of the
heart.
 Smooth muscles – in the walls of hollow
organs.
2. Muscle Functions
– Muscles moves internal and external body
parts, maintain posture, stabilize joints,
generate heat, and protect some visceral organs
 Motion. (maintain body posture)
contraction of skeletal muscles produces
body movements as walking, writing,
breathing and speaking.
 Posture and body, support – The muscular
system lends form and support to the body
and helps to maintain posture in opposition
to gravity.
 Heat Production - All cells release heat as
an end product of metabolism.
3. Organ System Involved in Movement
1. Muscular – moves the bones.
2. Skeletal – bones are moved, at their
joints, by muscles.
3. Nervous – Transmits impulses to
muscles to cause contraction.
4. Respiratory – exchanges O2 and CO2
between the air and blood.
5. Circulatory – transports O2 to muscles
and removes CO2.
4. Functional Characteristics of Muscles Tissue
-Special functional characteristics of muscles
include excitability, contractility, extensibility,
elasticity and tonicity.
1. Excitibility – ability to receive and
respond to stimulus.
2. Contractility – ability to shorten
(forcibly)
3. Extensibility – ability to be stretched
when relaxed.
4. Elasticity – ability to resume to its
resting length.
5. Tonicity – The ability to be partially
contracted (posture)
5. Skeletal Muscle Tissue
- Connective Tissue component connective
tissue coverings of skeletal muscle.
a. Perimysium – coarser fibrous membrane
covering bundles of muscle fibers.
b. Endomysium – Thin connective tissue
covering muscles to a bone.
 Tendon – cord of dense fibrous tissue
attaching a muscle to a bone.
 Aponeurpses – fibrous or membranous
sheet connecting a muscle & the part it
moves.
6. Microscopic Anatomy of a Muscle fiber
 The major cells of skeletal muscle tissue are
termed muscle fibers.
 Each muscle fiber has 100 or more nuclei
because it arises from fusion of many
myoblasts.
 The sarcolemma is a muscle fiber’s plasma
membrane; it surrounds the sarcoplasms.
 T tubules are invaginations of the
sarcolemma.
 Each muscle fiber contains hundreds of
myofibrils, the contractile elements of
skeletal muscle.
 Sarcoplasmic Reticulum surrounds each
myofibrils.
 Within a myofibril are thin and thick
filaments, arranged in compartments called
sarcomere.
 The overlapping of thick and thin filaments
produces striations.
 Myofibrils are built from three types of
proteins:
a. Contractile proteins (myosin for the thick
filament, and actin for the thin filaments)
b. Regulatory proteins (troponin, tropomyosin)
which parts of the thin filament.
c. Structural proteins (titin, myomesin and
dystropin)
7. Contraction and Relaxation of Skeletal Mus.
a. Polarization (resting potential)
 When the muscle fiber is relaxed, the
sarcolemma has a (+) charge outside and a
(-) charge inside.
 Na ions are more abundant outside the cell
and K ions are more abundant inside the
cell.
 The Na and K pumps maintain these relative
conceptions on either side of the
sarcolemma.
b. Depolarization
 This process is started by a nerve impulse.
 Acetylcholine released by the axon terminal
makes the sarcolemma very permeable to
Na_ions, which enter the cell and cause a
reversal of charge to (-) outside and (+)
inside.
 The depolarization spread along the entire
sarcolemma and initiates the contraction
process.
8. Sliding Filament Mechanism
 Depolarization stimulates a sequence of
events that enables myosin filaments to pull
thee actin filaments to the center of the
sarcomere, which shortens.
 All of the sarcomeres in a muscle fiber
contract in response to a nerve impulses;
the entire cell contracts.
 Tetanus is a sustained contractions bought
about by continuous nerve impulses; all our
movements involve tetanus.
9. Types of Muscle Contractions
1. Simple Muscle twitch: It is the response of
a muscle to single brief threshold stimulus.
2. Summation: It occurs when two stimuli
when each is capable of causing a muscle
to contract, follow each in rapid
succession.
3. Staircase (treppe) effect: It occurs when
series of stimuli are applied.
4. Tetanus: It is caused by continuous stimuli.
There is a little bit relaxation.
10. Muscle Arrangement
 Antagonistic muscle have opposite
functions. A muscle pulls when it
contracts, but exerts no force when it
relaxes and it cannot push.
 Synergistic muscles have the same
function and alternate as the prime
mover depending on the position of the
bone to be moved.
 The frontal lobes of the cerebrum
generates the impulses necessary for
contraction of skeletal muscles. The
cerebellum regulates coordination.
11. Muscle tone
 This is the state of slight contraction
present in muscles.
 The alternate fibers contract to prevent
muscle fatigue.
 This is regulated by the cerebellum.
 Good tone helps maintain posture,
produces 25% of body heat (at rest), and
improved coordination
 Isotonic exercise involves contraction
with movement; improves tone and
strength and Improves cardiovascular and
respiratory efficiency (aerobic)
 Concentric contraction- muscle exerts
force while shortening
 Eccentric contraction- Muscle exerts
force while lengthening.
 Isometric contraction occur when muscle
tension produces neither shortening nor
lengthening; improves tone and strength
but its not aerobic.
12. Energy Sources for Muscle Contraction
 Muscle fibers have three sources for ATP
production
a. creatine phosphate
b. anaerobic cellular respiration
c. aerobic cellular respiration
 Creatine Phosphate is a secondary energy
source;is broken down to creatine +
phosphate + energy. The energy is used
to synthesize more ATP.
 Glycogen is the most abundant energy
source and is first broken down to
glucose. Glucose is broken down in cell
respiration:
Glucose + O2  CO2 + H2O + ATP + heat
13. Effect of Exercise on Muscles
 Regular aerobic exercise results in
increased efficiency, endurance, strength,
and resistance to fatigue of skeletal mus.
 Resistance exercises causes skeletal
muscle hypertrophy and large gains in
skeletal muscle strength,
 Immobilization of muscles leads to muscle
weakness and severe atrophy.
14. Criteria for Naming Skeletal Muscle
Criteria
Example
Direction of
Superior rectus (of
contractile fibers
Rectus = straight
Oblique = diagonal
Transverse = across
eyeball), rectus
abdominate.
Location in body
Over bones
Between bones
Frontalis, occipitals,
sunscapularis,
Intercostals
Relative size
Maximus = large
Minimus = small
Major = greater
Minor = lesser
Longus = long
Brevis = short
Gluteus maximus
Gluteus minimus
Zygomaticus major
Zygomaticus minor
Palmaris longus
Peroneus brevis
Shape
Deltoid = triangular
Orbicularis = circular
Teres = long and round
Number of points of
attachment
Biceps = 2 heads
Triceps = 3 heads
Quadriceps = 4 heads
Biceps brachii
Triceps femoris
Quadriceps femoris
Type of action
Flexion
Extension
Elevation
Depression
Abduction
Adduction
Supination
Pronation
Tension
Location of the muscle’s
origin and insertion
Flexor carpi radialis
Extensor carpi radialis
longus
Levator ani, levator
scapulae
Depressor labii inferiorus
Abductor pollicus longus
Adductor pollicus brevis
Supinator
Pronator teres
Tensor fasciae latae
Sternocleidomastoid
muscle
15. Skeletal Muscle Groups
a. Muscles of the head
Frontalis
Mintalis
Obricularis oculi
Buccinator
Zygomaticus
Platysma
Risorius
Sternocleidomastoid
Orbicularis
Scalenes
Muscles Acting on
shoulder and upper limbs
Deltoid
Brachioradialis
Triceps bracii
Extensor pollicis brevis
Biceps brachii
Aconeus
Brachialis
Muscles of chewing and
swallowing
Muscles acting on the hip
and lower limbs
Pectoralis minor
Pectoralis major
Buccinator
Adductors
Hamstrings
Gracilis
grastrocenmius
Quadriceps femoris
soleus
Gluteus maximus
plantaris
Muscle of the chest
Muscles of the back
Pectoralis minor
Pectoralis major
Serratus anterior
Erector spinae
Trapezius
Latissimus dorsi
Muscle of respiration
Muscles of the
Abdomen
Diaphragm
Rectus abdominis
Transverse abdominis
Internal oblique
External oblique
16. Sites for Intramuscular Injections
- The common sites are the gluteus medius
(buttocks), value laterals (the lateral thigh), and
deltoid (shoulder).
17. Abnormalities and disorders in skeletal
muscle function
1. Hypertrophy – a phenomenon is which
forceful muscular activity causes
muscles size to increases.
2. Atrophy – a phenomenon in which
disuse of muscle causes the muscle size
to decrease.
3. Rigor mortis – state of contracture of all
muscle of the body after death.
4. Muscle cramps – spasmodic,
involuntary contraction occurring
during strenuous muscular activity.
5. Muscle Fatigue – physiological inability
of the muscle to contract.
6. Tremor – a rhythmic, involuntary,
purposeless contraction that produces a
quivering or shaking movement.
7. Myasthenia gravis – an autoimmune
disorder that causes chronic,
progressive damage of neuromuscular
junction.
8. Muscular dystrophy – a group of
inherited muscle destroying diseases
that cause progressive degeneration of
skeletal muscle fiber.
9. Tetanus – caused by Clostridium tetani,
which produces a toxin that causes
painful muscle spasms. The jaw muscles
are affected first.
10. Torticollis (wryneck) – persistent
contraction of sternocleidomastoid
muscle, drawing a head to one side and
distorting the face.
NERVOUS SYSTEM
1. Overview of the nervous system
1.1 Structure of the Nervous System
 The structures that make up the
nervous system brain, 12 pairs of
cranial nerves, spinal cord, 31 pairs of
spinal nerves, ganglia, enteric plexus
and sensory receptors.
1.2 Functions of the Nervous System
1. Detect changes and feel sensation
(sensory function).
2. Initiate responses to changes (motor
function).
3. Organization and store information
(intergrative function).
1.3 Organizations of the Nervous System
 The nervous system is divided
anatomically into the central nervous
system (brain and spinal cord) and the
peripheral nervous system (cranial and
spinal nerves).
 The major functional divisions of the
nervous system are the sensory
(afferent) division, which conveys
impulses to the CNS, and the motor
(efferent) division, which convey
impulses from the CNS.
 The efferent division includes the
somatic (voluntary) system, which
serves, skeletal muscles, and the
autonomic (involuntary) systems, which
innervates smooth and cardiac muscle
and glands.
2. Nerve Tissue
- The nervous tissue consists of neurons (nerve
cells) and neuroglia.
2.1 Neuron
 It is the basic structural and functional
unit of the nervous system.
 It is composed of the following parts:
cell body, dendrites, and axon.
A. Neuron cell body contains the
nucleus; cell bodies are in the CNS
B. Axon carries impulses away from
the cell body.
C. Dendrites carry impulses toward
the cell body.
2.1.1 Types of Neurons – nerve fibers
A. Sensory – carry impulses from
receptors to the CNS, may be somatic
(from skin, skeletal muscle, joints) or
visceral (from internal organs).
B. Motor – carry impulses from the CNS to
effectors; may be somatic (to skeletal
muscle) or visceral (to smooth muscle,
cardiac muscle, or glands) Visceral
motor neurons make up the autonomic
nervous system.
C. Interneurons – entirely within the CNS.
2.2 Neuroglia
 Oligodendrocytes in CNS from the
myelins.
 Microglia phagocytize pathogens and
damaged cells.
 Astrocytes contribute to the bloodbrain barrier.
 Ependymal cells line the ventricles of
the brain and central canal of the spinal
cord; form CSF and assist in its
circulation.
3. Generation and transmission of impulses
3.1 Neurons have two major physiological
properties:
1. The ability to respond to stimuli and
convert them into nerve impulse
2. The ability to transmit the impulse to
the other neurons, muscles, or glands.
3.2 The nerve impulse propagation
State or Event
Polarization
(The neurons is not
carrying an electrical
impulse)
Depolarization
(generated by stimulus)
Propagation of the
impulse from point
of stimulus
Repolarization
(immediately follows
depolarization)
Description

Neuron membrane
has a (+) charge
outside and a (-)
charge inside.

Na+ ions are more
abundant outside the
cell.

K+ ions and negative
ions are more
abundant inside the
cell.
Sodium and Potassium
pumps maintain these ion
concentration.

Neuron membrane
becomes very
permeable to Na+
ions, which rush into
the cell.

The neuron
membrane then has
a (-) charge outside
and a (+) charge
inside.

Depolarization of
part of the
membrane makes
adjacent membrane
very permeable to
Na+ ions, and
subsequent
depolarization, which
similarly affects the
next part of the
membrane, and so
on.

The depolarization
continues along the
membrane of the
neuron to the end of
the axon.

Neuron membrane
becomes very
permeable to K+
ions, which rush out
of the cell. This
restore the (+)
charge outside and
(-) charge inside by
the membrane.

The Na+ ions are
returned outside and
the K+ ions are
returned inside by
the sodium and
potassium pumps.

The neuron is now
able to respond to
another stimulus and
generate another
impulse.
4. Anatomy and function of the spinal cord
4.1 Location and protection of the spinal cord
a. Location: within vertebral canal;
extends from the foramen magnum to the disc
between the 1st and 2nd lumbar vertebrae.
b. Protection: The spinal cord is
protected by the vertebral column, meninges,
cerebrospinal fluid and denticulate ligaments.
4.2 External and Internal anatomy
a. External: white matter is the
myelinated axons and dendrites of interneurons
b. Cross-section: internal H-shaped gray
matter contains cell bodies of motor neurons
and interneurons;
4.3 Functions: transmits impulses to and from
the brain (ascending tracts carry sensory
impulses to the brain; descending tracts carry
motor impulses away from the brain), and
integrates the spinal cord reflexes.