LGSE 3012

What is nervous tissue?

Nervous tissue is specialized to react to stimuli and to conduct impulses to various organs in the body which bring about a response to the stimulus.

Nerve tissue are all made up of specialised nerve cells called neurons

Neurons are easily stimulated and transmit impulses very rapidly.

A nerve is made up of many nerve cell fibres (neurons) bound together by connective tissue.

Types of neurons

sensory (or afferent) neurons

motor (or efferent) neurons

Inter neurons

Structure of a Motor Neuron

Classification of Neurons

Unipolar Neurons.

• Sensory neurons single process or fibretwo main branches (axon and dendrite)

Multipolar Neurons.

• Motor neuronsnumerous cell processes (an axon and many dendrites)multipolar neurons

Bipolar neurons

• Bipolar neurons dendrite at one end and an axon at the other

Functions of Nerve Tissue

• Nervous tissue allows an organism to sense stimuli in both the internal and external environment.

• The stimuli are analysed and integrated to provide appropriate, co-ordinated responses in various organs.

• The afferent or sensory neurons conduct nerve impulses from the sense organs and receptors to the central nervous system

• Autonomic motor or efferent neurons transmit impulses to the involuntary muscles and glands.

What is the characteristics of muscle tissue?

Contractility

• Only one action: to shorten

• Shortening generates pulling force

Excitability

• Nerve fibers cause electrical impulse to travel

Extensibility

• Stretch with contraction of an opposing muscle

Elasticity

• Recoils passively after being stretched

Types of Muscle TissueSkeletal

• Attach to and move skeleton• 40% of body weight• Fibers = multinucleate cells (embryonic cells fuse)• Cells with obvious striations• Contractions are voluntary

Cardiac: only in the wall of the heart

• Cells are striated• Contractions are involuntary

(not voluntary)

Smooth: walls of hollow organs• Lack striations• Contractions are involuntary (not voluntary)

Skeletal muscle

Epimysium: surrounds whole muscle

Perimysium is around fascicle

Endomysium is around each muscle fiber

Skeletal Muscle

• Each muscle: one nerve, one artery, one vein– Branch repeatedly

• Attachments– One bone to another– Cross at least one movable joint– Origin: the less movable attachment– Insertion: is pulled toward the origin– Usually one bone moves while the

other remains fixed– In muscles of the limb, origin lies

proximal to the insertion (by convention)

– Note: origin and insertion may switch depending on body position and movement produced

Skeletal muscle

• Fibers (each is one cell) have striations

• Myofibrils are organelles of the cell: these are made up of filaments

• Sarcomere– Basic unit of

contraction– Myofibrils are long

rows of repeating sarcomeres

– Boundaries: Z discs (or lines)

This big cylinder is a fiber: 1 cell

-an organelle

BONE● What is bone?● ~ hard, whitish tissue that makes up the skeletal system

of vertebrates.● Fetuses have cartilages in the shape of future bones

which convert into bones at a later stage ;● a) from the center (earlier stage)● b) from growth plates at the end of bones (later stage)● Babies are born with 300 bones● The bones fuse as they age● An average adult has 206 bones (after fusing)

Bone Growth● Cartilages in the shape of future bones are formed.

● Osteoblasts penetrate cartilage to form bone.

How ?● Osteoblasts deposit osteoids which contain sites for Calcium

Phosphate crystal production.

● The production and deposition of these mineral crystals give bone it's hard and strong structure.

● Blood vessels develop

● Osteoclasts reshape the bone – forms a central cavity

● Central cavity contains the bone marrow.

● New cartilage is formed at the growth plate which is placed at the end of the bone.

● The cartilages are turned into bone by osteoblasts

● Process continues until the growth plate 'closes', leaving no more room for growth.

How do bones elongate?

● Damage to growth plate due to trauma.

● Illnesses that damage growth plate

● Growth Hormone deficiency

● Growth Hormone (Acromegaly is a result when access GH is produced. Bones continue to grow)

● Estrogen

● Testosteron.

Hormones involved in bone growth?

What can halt growth of bones?

Thank You