Week 9 (exam 3) Flashcards
What are the 2 structures of the bone?
1) spongy or cancellous bone
2) compact bone
What is spongy or cancellous bone made with?
Made with trabeculae (sg trabeculum)
What is trabeculae?
Little struts that criss cross each other
If you take a strut and look under a microscope you will see lamella, lacunae, canaliculi in red bone marrow
What is compact bone?
Thick and solid
Has a central canal or Haversian canal
Has many osteons or haversian systems
Waste goes in cell to central canal and nutrients from canal go outward through the cell
Why do bones bleed?
Because of the central canal or Haversian canal
How are bones formed?
1) dermal membrane or membrane bone or intramembranous bone
2) endochondrial (cartilage replacement bone)
What is dermal bones or membrane bone or intramembranous bone?
CT membrane in fetus that is laid down
Osteoblasts in membrane starts to make bony matrix
Center of ossification or ossification system
What is the dermis?
Lower layer of skin where bone initially develops
What is the center of ossification or ossification center?
Where process of bone formation begins and where it spreads out
What does ossification mean?
Bone formation
What is endochondrial?
Begins as hyaline cartilage
Includes bones in limbs
Becomes bone over time
What is an epiphyseal plate?
The cartilage that is left in bone when you’re a teenager
What happens when epiphyseal plates go through closure?
The bone cannot grow anymore
Person is in their late teens
What are epiphyseal lines?
Where the epiphyseal plates were
Happens in late teens
What is the articular cartilage?
Only cartilage left in bone
Thin little layer at the joint
Late teens
How is the medullary cavity or marrow cavity formed?
When the process of creating bone through endochondrial is done or almost done osteoclasts kick in and remove matrix inside bone
What is a medullary cavity or marrow cavity and what is found in it?
Hollow space in bone where yellow marrow or white marrow is found (basically fat)
What is remodeling in bone?
The constant dance between osteoclasts (breaking down matrix) and osteoblasts (building up matrix)
Where can you take and store Ca if needed?
Skeleton
What are the 2 major regulators of Ca?
1) parathyroid gland (4 of them in the back of thyroid glands)
2) thyroid gland
What is secreted from the parathyroid gland and what does it do?
Parathyroid gland hormone
PTH increases osteoclasts activity
- breaks skeleton down and blood Ca levels rise
What is secreted from the thyroid gland and what does it do?
Calcitonin hormone
Inhibits activity of osteoclasts
-blood Ca levels drop
What kind of cells produce calcitonin?
Parafollicular cells or C cells
What happens to the osteoblasts when a person gets older?
Bone becomes brittle lack of collagen
Osteopenia
Osteoporosis
What is osteopenia?
Insufficient ossification (decrease in bone density and not strong enough)
What is osteoporosis?
Osteopenia to the extreme
Extreme danger of fracture and breaks
Pores appearance
What are Bisphosphonates?
Class of drugs to reduce osteoporosis
Slows down osteoclasts and balances out osteoclasts with how slow osteoblasts are going
What are excited or irritability cells?
Cells that can alter a charge when stimulated
Ex: neurons
How is alter in charge across cell membrane accomplished?
Ion channels
Ionic players
- Na+
- K+
Nerve or neurons that are at rest have what charge?
Slightly negative
What is a potential difference?
Difference of charge across cell membrane
Negative on the inside
Positive on the outside
What is the resting potential?
Difference in charge across the membrane when cell is resting
What is the resting potential number inside a cell membrane?
-70mV
What is an oscilloscope?
Used to measure electrical events
What is depolarization?
Heading toward positive territory from resting
What is hyperpolarization?
Heading toward more negative territory from resting
What is repolarization?
Depolarize and let it return to resting
What is graded potential?
Slight stimulate has gradual change in charge
What are the ions that voltage gated ion channels open for?
1) Na+ (they flood in)
2) K+ (they flood out)
What is the action potential?
Threshold and on
Basis of all nerve pulses
All or none
If you don’t depolarize and hit the threshold there is no action potential
If you depolarize and hit the threshold you get action potential
No action potentials are stronger than the others
After an action potential occurs what happens and explain
Refractory period- new action can not be stimulated
2 parts
1) absolute refractory period
2) relative refractory period
What is the absolute refractory period?
Occurs in the beginning
Impossible to have another action potential
Na+ and K+ ions are glued shut until end of absolute refractory period
What is the relative refractory period?
Can hit another action potential if hit with stronger than normal stimulation
Not glued shit anymore
How are nerve signals transmitted? Step by step (from pictures from lecture)
1) neuron is at rest and has negative charges inside and positive charges outside
2) Na+ comes in at front of neuron
3) Na+ follows local current
4) Na+ moves to middle and K+ leaves from front of neuron
5) K+ leaves neuron as Na+ move to end and refractory period occurs from where Na+ started
What is the local current?
Movement of Na+ atoms moving down axon
What does the refractory period ensure?
Ensures action potential moves in one direction and doesn’t go backwards
What does propagation mean?
Action potential stimulates action potential stimulates action potential and continues to move like a WAVE down the axon
Is the strength of the action potential all in one lost or reduced?
No
What does myelin do?
Speeds up movement of action potential down an axon
What is an neurolemmocyte?
Schwanns cell
Special kind of glial cell
Wrapped around axon
What is the nodes of ranvier?
Parts of axon not covered by schwanns cells
What is saltatory propagation mean?
Nerve transmission has to skip down axis because of Schwanns cell
What are the 3 types of diameter the axon can have?
1) Type A fiber (Type A neuron/ axon)
2) Type B fiber
3) Type C fiber
What is type A fibers?
Largest diameter (thick) and fastest
300 miles per hour
What are type B fibers?
Intermediate diameter and moderate speed
40 miles per hour
What is type C fibers?
Thinnest diameter and slowest of the three
2 miles per hour
What is the connection between cells?
Synapse
Why do neurons connect to other cells?
To submit transmissions
What is the second cell CNS connects to?
Nerve cell
Neuron to neuron
What is the 2nd cell PNS connects to?
Effector cells (muscle, organ, gland) or neurons
What does the axon communicate with on other cells?
Dendrites
What is a presynaptic neuron?
1st cell of sequence
What is a postsynaptic neuron?
2nd cell in sequence
What do the axon terminal branches do?
They have neurotransmitters at the end and release and stimulate postsynaptic neurons
What is at the end of each axon terminal branches?
Axon bulb or synaptic knob or terminal bouton
What is a synaptic cleft?
Space between dendrite and axon bulb
What does a synaptic vesicle contain?
Contains neurotransmitters
What is the ion channels in dendrites that begin to open?
Chemically regulates ion channel
