Midterm Review 3/3 Flashcards
Describe the endothelial cells.
- Linked together by continuous tight junctions that prevent free diffusion into brain
- Unlike other capillaries in body with fenestration (large slit pores between adjacent endothelial cells)
- Also have thick basement membrane under endothelial cells
What substances easily pass through the blood brain barrier
uncharged molecules, lipid-soluble molecules, lipid-soluble gases (CO2, O2, and anesthetics), drugs (caffeine, nicotineT, heroin)
True/False: the blood-brain barrier is very permeable to water
True
What causes the blood-brain barrier to be compromised?
meningitis and bacteria cause inflammation
What are the parts of the neuron?
Cell body, dendrites, axon, and presynaptic terminal
What does the cell body of the neuron contain?
nucleus, ER, etc
What are the dendrites of a neuron?
receptors that bind to neurotransmitters
What is the function of the axon?
The message-sending portion of the neuron, carries action potential to the next neuron
How does AP travel in myelinated axons?
through the nodes of Ranvier
What is the function of glial cells?
supportive to help the neurons (assistants) bathes them in healing solutions
True/False: Glial cells can not proliferate throughout life.
False: they proliferate throughout life (unlike neurons)
What is the function of oligodendrocytes?
- Form myelin sheath in CNS axons
- Schwann cells form myelin sheath in peripheral nerves
What are the Nodes of Ranvier and what do they do?
rich in positive sodium ions and they jump from one node to the next (makes it a lot faster to have that action propagate down the axon.
What happens if we have a problem with the nodes of ranvier or the myelin sheath?
The person would be weak and not be able to walk well
What is the presynaptic terminal and what happens?
where axons terminate and where neurotransmitters are released which diffuse across synaptic cleft,
bind to receptors on postsynaptic membrane, electrical signal is converted to chemical signal (neurotransmitter release), triggers AP
What are the excitatory neutrotransmitters?
- Glutamate (major excitatory neurotransmitter)
- Acetylcholine
- Epinephrine
- Histamine (generally excitatory effects)
- Dopamine (both Excitatory and Inhibitory)
What are some of the inhibitory neurotransmitters?
- GABA (Gamma-aminobutyric acid) (most common
one in nervous system) - Serotonin
What is action potential?
transient, regenerative,
electrical impulse in which the membrane
potential rapidly rises to a more positive peak
True/False: Normal resting voltage of AP is negative
True
What happens at the junction between two neurons?
AP causes neuron to release chemical neurotransmitter (which either excites or hinders next neuron from firing its own AP)
What do the efferent nerves do?
Allows brain to communicate with periphery (e=away from brain)
What do the afferent nerves do?
Allows periphery (e.g. organs, muscles) to
communicate with brain
(a= to brain)
Action potential has ____ depolarization and ____ repolarization.
Rapid depolarization and slow repolarization
What happens when an electrical stimulus of nerve or muscle cell causes membrane potential to become more + than threshold voltage?
triggers AP
Depolarizing stimulus
requires certain
____ and ____.
requires certain
intensity (magnitude)
and duration
When a cell fires an AP, how soon can it fire another one?
Cell needs time to recover
What is the absolute refractory period?
Second response is not
possible regardless of
strength/duration of
stimulus due to Na+ channel inactivation
How long does the absolute refractory period last?
Lasts from initiation of AP to when repolarization is
almost complete
What is the relative refractory period?
Second response can be
elicited but requires a greater stimulus (in strength or duration)
Why is action potential so important?
Because it lets the body talk to the brain and the brain talk to the body
What happens during saltatory conduction?
current flows from node to node, very efficient system
What is a motor unit?
Motor neuron with
cell body in spinal cord have long axons that branch with target muscle
How is synaptic nerve transmission terminated?
Large amount of acetylcholinesterase in muscle basement membrane
What are the three types of muscle?
Skeletal, cardiac (heart), smooth (intestines, bladder)
What is the basic function of muscles?
to generate force or movement in response to physiological stimulus
Muscles turn a chemical or electrical command
into a ____ response.
mechanical
What triggers muscle contraction?
rise in free cytosolic calcium concentration
True/False: All muscle types have the same contraction trigger.
True
What is sarcolemma and why is it important?
plasma membrane and it allows communication with muscle cels
True/False: A single muscle cell responds to a single neuron, but, a single neuronal axon may bifurcate to
innervate several muscle cells (motor unit)
True
What is the big muscle bundle broken down into?
myosin and actin
What two myofilaments are responsible for contraction?
myosin and actin
What happens during a muscle contraction?
- Myosin heads bind to actin, forming cross bridges, then detach from actin
- Energy is derived from ATP hydrolysis
- Therefore needs to be regulated or myocyte
would be depleted of ATP - In all 3 muscle types, ↑ Ca++ initiates and allows
cross-bridges to continue
Where is glycogen stored and what is it used for?
in muscle cells and can be used for energy
Usually, the muscle uses ____ metabolism.
aerobic
True/False: You body can function using anaerobic metabolism if you are lifting heavy weight.
True
What chemical makes you feel sore after a workout?
lactate
What do T-tubules do?*
Penetrate muscle at junctions of A and I bands (a highway that allows the calcium to go from the sarcoplasmic reticulum to the T-tubule and then go deeper into the muscle to provide calcium for muscle contraction)
What is the sarcoplasmic reticulum?
Storage site of intracellular calcium
How does excitation-contraction coupling work in skeletal muscles?
- Action potential begins at motor end plate
- Travels along cell membrane and down T-tubules
- Depolarization of T-tubule activates voltage-gated
L-type Ca++ channels - Ca++ released from sarcoplasmic reticulum
- Activates troponin C which starts cross-bridge cycling
How is ach inactivated?
by acetylcholinesterase (stops muscle activity)
What fibers make up skeletal muscle?
slow and fast twitch fibers
Describe slow-twitch fibers.
- Smaller, thinner fibers, surrounded by capillaries to provide oxygen
- Red due to ↑myoglobin to bind oxygen
- Rely on oxidative metabolism for energy (low glycogen level)
- Provide endurance for minutes to hours (quadriceps in marathoners)
Describe fast-twitch fibers.
- Abundant glycogen for rapid energy release by glycolytic pathway
- Less mitochondria, less myoglobin, less extensive blood supply for oxygen
- Give great amount of power for a few seconds to a minute or so
- Gastrocnemius (calf muscle used in jumping), fatigue quickly
Are slow twitch muscle fibers aerobic or anaerobic?
aerobic
Are fast twitch muscle fibers aerobic or anaerobic?
anaerobic
True/false: the amount of fast/slow twitch muscle fibers can change with training or age.
True
Compare and Contrast slow and fast twitch muscle fibers.
Slow: oxidative (red muscle), small diameter, high myoglobin content, high capillary density, many mitochondria, low glycolytic enzyme content
Fast: Glycolytic (white muscle), large diameter, low myoglobin content, low capillary density, few mitochondria, high glycolytic enzyme content
How can fast, slow and intermediate twitch be identified?
biopsy
True/False: In any muscle there will be a mixture of slow and fast fibers.
True
Motor units containing ___ fibers will be recruited first to power normal contractions.
slow
___ fibers help out when particularly forceful contraction is required.
Fast
All 3 muscle types terminate contraction through ____ re-uptake into sarcoplasmic reticulum
calcium
How is calcium removed from the cytoplasm?
by either extruding
calcium across cell membrane or sequester within intracellular compartments
- Use Na-Ca exchanger or Calcium pump at plasma membrane
- Calcium re-uptake by SERCA-type calcium pump
- Voltage gates
