Specialized Eukaryotic Cells

Question 1

What is the membrane (resting) potential on the inside and outside of most neurons?

Answer 1

90 mV outside the cell membrane (more Na)

-90 mV inside the cell membrane (more K inside)

Question 2

What is saltatory conduction?

Answer 2

Depolarization jumping from node of Ranvier to node of Ranvier along a myelinated axon

Question 3

What are the three stages that a neuron passes through after depolarization?

Answer 3

1. Absolute refractory period (can’t fire)
2. Relative refractory period (hard to fire)
3. Return to resting potential

Question 4

What are all types of muscle tissue composed of?

Answer 4

Muscle cells (fibres/myocytes) that contain myofibrils possessing contractile filaments of actin and myosin

Question 5

How are contractile filaments arranged in smooth muscle cels?

Answer 5

Actin predominates

The filaments course obliquely int he cells and attach to the plasma membrane

Question 6

What are skeletal muscles characterized by?

Answer 6

• Peripherally located nuclei

- Striated myofribrils

Question 7

What is involved in catalyzing the chemical reaction between actin and myosin filaments in the cross bridge region of muscle fibres?

Answer 7

The sarcolemma that extends into the fibre as numerous small traverse tubes (T-tubules)

These tubules ring the myofibrils at the A-I junction and are bounded on each side by terminal cisternae of the sarcoplasmic reticulum (the sarcoplasmic reticulum is involved in catalyzing the chemical reaction between actin and myosin)

Question 8

How is actin activated for muscle contraction? Describe the mechanisms for the contraction.

Answer 8

• Calcium is released from sarcoplasmic reticulum
• Ca attached to subunit of troponin, resulting in the movement of tropomyosin and the uncovering of the active site for attachment of actin to myosin head
• ATP in the myosin head hydrolyses, producing energy a phosphate and ADP
• The myosin head bends and pulls the actin filament in to the A band.
• Myosin binds a new ATP to detach bridge

Question 9

How does cardiac muscle differ from skeletal muscle?

Answer 9

• Cardiac muscle fibres branch
• Cardiac muscle fibres contain one central nuclei
• Cardiac muscle fibres contain large numbers of mitochondria
• Individual cardiac muscle fibres attach to each other at intercalated disks with gap junctions (to propagate depolarization)
• T-tubules enter at Z lines and form a diad with only one terminal cisterna of the sarcoplasmic reticulum in cardiac muscle fibres

Question 10

What is loose irregular connective tissue and where is it found?

Answer 10

The ‘packaging material of the body,’ found in between muscles and organs, binds skin to underlying tissue

Almost all connective tissue type cells are found in loose irregular connective tissue

Question 11

What is heparin and what type of cells is it found in?

Answer 11

Heparin is a compound which prevents blood clotting

Found in mast cells (along with histamine)

Question 12

List the five most common types of collagen and where they can be found.

Answer 12

• Type I - most common (dermis, bone, dentine, tendons, organ capsules, fascia and sclera)
• Type II (hyaline and elastic cartilage)
• Type III (collagenous component of reticular fibres)
• Type IV (Basal lamina of basement membrane)
• Type V (component of placental basement membranes)

Question 13

What is ground substance?

Answer 13

The gelatinous substance that fills most of the space between the cells and fibres. It is composed of acid mucopolysaccharides and structural glycoproteins

Question 14

What is dense connective tissue and where is it found?

Answer 14

Found in the dermis, periosteum, perichondrium and capsules of some organs. All fibre types are present, but collagenous fibres predominate

Forms ligaments and tendons

Fibroblasts are practically only type of cells present

Question 15

What are the three types of cartilage?

Answer 15

• Hyaline (costal/rib, articular, nose, larynx, trachea and bronchi)
• Elastic (pinna of ear, auditory tube and cartilage of the larynx)
• Fibrous (Anchorage of tendons and ligaments, between vertebral disks, symphis pubis and in some interarticular disks and ligaments)

Question 16

What is the organic/inorganic matrix of bones composed of?

Answer 16

Organic

• Dense collagenous fibres
• osteomucoid substance containing chondroitin sulphate (provides flexibility and tensile strength)

Inorganic ((provides rigidity))

• calcium phosphate,
• calcium carbonate
• and a little magnesium, fluoride, hydroxide, sulphate and hydroxyapatite

Question 17

What type of bone contains the haversian system? What are components of this system called?

Answer 17

Compact bone:

• Osteons
• Interstitial/circumferential lamellae around central haversian canals
• Osteocytes in lacuna are serviced by canaliculi from haversian canal/other osteocytes
• Volkmann’s canals traverse the bone transversely and interconnect haversian systems
• The periosteum envelopes the bone

Question 18

Long bones are specifically supplied by arteries which pass to the marrow through ___, ___ and ___ arteries

Answer 18

Long bones are specifically supplied by arteries which pass to the marrow through diaphyseal, metaphyseal and epiphyseal arteries