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Compact bone
external layer of used for support
Spongey bone
internal layer made of calcified lattice
Epiphysis
end of a long bone
Epiphyseal plate
site of bone growth
Diaphysis
shaft of long bone
2 main composition of bone
collagen + calcium phosphate hydroxyapatite
What structure does the collagen make (in the structure of bone)
triple-helix structure —> makes the bone stronger than steel
Trabecular bone supplied by
bone ECF
Compact bone supplied by
blood vessels in Haversian canals
Chondrocytes form
cartilage
Osteoblasts create
calcium phosphate crystals to replace cartilage
role of EC matrix Ca2+
forms calcified matrix of bone and teeth
role of ECF Ca2+
- Neurotransmitter release at synapse
- muscle contraction in heart and smooth muscle
- blood clotting (coagulation)
- helps stick cells together (tight junctions)
- regulates neuron excitability
role of ICF Ca2+
- triggers muscle contraction (binding to troponin)
- acts as second messenger
PTH secreted by the
parathyroid glands
PTH function
INCREASES blood Ca2+
target cells of PTH
kidney, bone, intestine
target receptor of PTH
membrane receptor acts via cAMP
absence of PTH causes
hypocalcemic tetany (lack of Ca2+)
Calcitriol other name
Vitamin D3
calcitriol
activated form of vitamin D (from sunlight) helps regulate Ca2+ levels in the body by INCREASING blood Ca2+
transport method of PTH
dissolved in plasma
transport method of Vitamin D3
bound to plasma protein
What triggers calcitriol production
- low plasma Ca2+
- PTH indirectly increases by activating kidney enzymes
- Prolactin (during pregnancy)
Target cells of calcitriol
intestine, bone, kidney
How does PTH act on intestine?
stimulates calcitriol production —> increases Ca2+ absorption (stimulation of transport protein)
How does calcitriol + PTH act on bone?
enhances osteoclast activity —> increase of Ca2+ release from bone
How does calcitriol act on kidney?
increases Ca2+ reabsorption; prevents calcium loss in urine
Which tissue does calcitriol directly impact?
intestine
transport method of calcitonin
dissolved in plasma
target receptor of calcitonin
G protein-coupled membrane receptor
Target cell/tissue of calcitronin
bone and kidney
target receptor of calcitrol
nuclear
calcitronin secreted by the
C cells of thyroid gland (parafollicular cells)
What triggers release of calcitonin
high plasma [Ca2+]
function of calcitonin
LOWERS BLOOD CA2+
- prevents bone resorption
- enhances kidney excretion (through urine)
mass balance for calcium balance
dietary intake should equal Ca2+ loss in the urine and feces
ECF calcium concentration
2.5mM
what regulates calcium uptake by bone
calcitonin
what regulates calcium release by bone
PTH, Calcitriol, Cortisol
Where is the main storage for calcium
bone
what regulates calcium transport into cells
electrochemical gradients
what regulates calcium transport out of cells
active transport
what regulates calcium uptake by kidney
passive filtration
what regulates calcium release by kidney
PTH
calcitonin function for kidney
increases calcium excretion —> loss in urine
What is responsible for bone resorption?
Osteoclasts
Osteoclast function
secrete acid and enzymes that dissolve calcium phosphate in bone —> release of Ca2+ into blood
Osteoporosis
bones to become weak and brittle due to excessive resorption
Monosynaptic reflex has
a single synapse between the afferent and efferent neuron
Polysynaptic reflex has
at least one interneuron between sensory and motor neuron; has both synapses in the CNS
RECALL: Sensory neurons are afferent or efferent neurons?
afferent neurons
RECALL: Motor neurons are afferent or efferent neurons?
efferent neurons
Which reflex is slower?
polysynaptic reflex because of the additional synapse
RECALL: where is the CNS located?
spinal cord
location of interneuron on polysynaptic reflex
CNS/spinal cord
skeletal muscle reflexes are
monosynaptic and polysynaptic
autonomic reflexes are
ALL polysynaptic
somatic reflexes control
skeletal muscles
autonomic reflexs control
smooth msucle, cardiac muscle, and glands
autonomic reflexes have at least two synapses in
the CNS and autonomic ganglion
reciprocal inhibition
when one muscle contracts while its antagonist relaxes
what happens during knee-jerk reflex?
activation of quadriceps (contraction)
inhibition of hamstrings (relaxation)
what type of reflex is the activation of quadriceps in knee-jerk?
monosynaptic
what type of reflex is the inhibition of hamstrings in knee-jerk?
polysynaptic
two types of stretch receptors
golgi tendon organs and muscle spindles
golgi tendon organ links the
muscle and tendon together
golgi tendon organ function
prevents excessive contraction to prevent injury
golgi tendon organs (GTO) detects
changes in muscle tension
what detects the increase in tension for GTO
sensory nerve endings embedded in colalgen fibers (of TENDON)
GTO reflex monosynaptic or polysynaptic?
polysynaptic
What is the main characteristic of muscle spindles?
they are tonically active
tonically active meaning
fires even when muscle is at rest
muscle spindle detects
changes in muscle length and stretch
what does muscle spindle function
regulation of muscle tone
extrafusal fibers
main muscle fibers that generate force
purpose of muscle spindles being tonically active
muscle readiness
more stretch = _________ sensory neuron firing
faster
Crossed Extensor Reflex monosynaptic or polysynaptic?
polysynaptic
Crossed extensor reflex function
maintains balance when one leg is lifted (in response to pain)
Crossed extensor reflex paired with
withdrawal reflex
which leg shows flexion response during crossed extensor reflex
leg with pain stimulus
which leg shows extension response during crossed extensor reflex
leg without pain stimulus (holding leg)
muscle action during flexion response
flexor muscles contract
extensor muscles inhibited
muscle action during extension response
flexor muscles inhibited
extensor muscles contract
sensory receptors send input to
spinal cord, brainstem, cerebellum, and cerebral cortex
vestibular system sends signals to
cerebellum
spinal reflexes sends signal to
spinal cord
which main components control postural reflexes?
cerebellum and brainstem (spinal cord)
role of cerebellum in voluntary movement
Provides feedback and corrects errors in movement
role of motor cortex in voluntary movement
Sends commands to muscles to execute movement
role of basal ganglia in voluntary movement
Helps refine movement and prevent unwanted motions
role of cortical association areas in voluntary movement
Plans and organizes movement
