Specialized Eukaryotic Cells Flashcards
What is the membrane (resting) potential on the inside and outside of most neurons?
90 mV outside the cell membrane (more Na)
-90 mV inside the cell membrane (more K inside)
What is saltatory conduction?
Depolarization jumping from node of Ranvier to node of Ranvier along a myelinated axon
What are the three stages that a neuron passes through after depolarization?
- Absolute refractory period (can’t fire)
- Relative refractory period (hard to fire)
- Return to resting potential
What are all types of muscle tissue composed of?
Muscle cells (fibres/myocytes) that contain myofibrils possessing contractile filaments of actin and myosin
How are contractile filaments arranged in smooth muscle cels?
Actin predominates
The filaments course obliquely int he cells and attach to the plasma membrane
What are skeletal muscles characterized by?
- Peripherally located nuclei
- Striated myofribrils
What is involved in catalyzing the chemical reaction between actin and myosin filaments in the cross bridge region of muscle fibres?
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)
How is actin activated for muscle contraction? Describe the mechanisms for the contraction.
- 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
How does cardiac muscle differ from skeletal muscle?
- 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
What is loose irregular connective tissue and where is it found?
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
What is heparin and what type of cells is it found in?
Heparin is a compound which prevents blood clotting
Found in mast cells (along with histamine)
List the five most common types of collagen and where they can be found.
- 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)
What is ground substance?
The gelatinous substance that fills most of the space between the cells and fibres. It is composed of acid mucopolysaccharides and structural glycoproteins
What is dense connective tissue and where is it found?
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
What are the three types of cartilage?
- 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)
