6 - skeletal tissues - its - boston college · 6 - skeletal tissues skeletal tissue types ......
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6 - Skeletal tissues
SKELETAL TISSUE TYPES notochord cartilage bone dentine enamel
ENDOSKELETON vs DERMAL SKELETON
SKELETAL TISSUE
USE & FUNCTION
BONE SCALING
Excitatory vs Inhibitory Influences: Neural Integration
EPSP: excitatory postsynaptic potential
IPSP: inhibitory postsynaptic potential
But also Ach,serotonin and others
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1.EPSP: excitatory postsynaptic potential
2. IPSP: inhibitory postsynaptic potential (GABA and glycine are the main neurotransmitters)
Key point: An action potential in a presynaptic neuron results in a graded potential in the postsynaptic neuron.
4
NOTE: 1. The role of voltage-gated calcium channels
2. Vesicles with neurotransmitter
3.Neurotransmitter binding to postsynaptic receptors (often ligand-gated ion channels)
4.Re-uptake and enzymatic breakdown of neurotransmitter
5. At an excitatory synapse non-selective ion channels open and ions, mostly Na+ move down the gradient
6. At an inhibitory synapse Cl- channels open
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•Real neurons receive as many as 200,000 synapses each •Ion flows from all inputs summate or average at the initial segment •An action potential in the postsynaptic neuron occurs if the membrane potential at the initial segment reaches threshold
Neural integration
Q: What are the strengths and weaknesses of the organic and inorganic components of skeletal tissues?
Q: What are skeletal tissue made of?
Hydroxyapatite: Ca10(PO4)6(OH)2Collagen
Dermal or membranous Endochondral direct development cartilage precursor shallow location deep location protection function support function
Bone undergoes deposition and resorption by the activity of osteoblasts and osteoclasts throughout life.
Q: why might a single animal have more than one skeletal tissue at different times of life? In different parts of the body?
QQ: why might some single skeletal structures be formed of more than one tissue?
SKELETAL TISSUE USE AND FUNCTION
Stress vs strain
Strain is measured as change in length relative to the original length (dimensionless)
Stress is measured in units of force / area (Gpa)
Q: Which skeletal tissues will strain (deform) most? Least? Q: Which skeletal tissue will break most easily? Least?
Stress-strain curves differ depending on the material, whether inorganic or organic
Q: Which curve represents cartilage? bone? dentine? enamel?
E = Young’s modulus elasticity
ba
c
d
Q: How does bone used for different purposes vary in composition?
Q: what is the relationship between the inorganic content and the modulus of elasticity?
b
a
c
ba c
Q: How might you explain the differences in mineral content among the various arm bones of a bat? http://youtu.be/rMSIauO-MJc?list=PL011EB0DA5D2CC028
Swartz and Middleton 2007
Glossophaga soricina
5 X
Q: Why aren’t large animals just “bigger models” of small animals?
Support is dependent on bone x-sec, NOT bone volume.
Q: Will the x-sec of legs increase less fast than, equally as fast as, or faster than mass (≈ volume)?