BIOL 213 Test 3

What is an example of an action caused by contraction of skeletal muscle?

raising your hand

How are smooth and skeletal muscle similar?

both are widespread throughout the body

What general statement about muscle tissue is true?

muscles only pull, never push

Which type of muscle exhibits automatically?

cardiac

Which type of muscle causes flexion and extension of the elbow?

skeletal

What is an example of a fast twitch skeletal muscle?

extraocular muscle

What does the endomysium do?

surrounds individual muscle fibers

What is the resting membrane potential?

-70mV

What are actin and myosin?

thin and thick filaments

What does troponin do?

bind calcium ions

What is the function of nebulin?

holds thin filament together

What does titin do?

prevents over-stretching of sarcomeres

True/false, Each muscle fiber is innervated by a branch of a motor neuron

true

What are the properties of myosin heads?

form cross bridges, contain a bend-able hinge region, bind to ATP

Where does a sarcomere extend from?

Z disc to Z disc

What is sarcoplasm?

cytoplasm of a muscle fiber

What are the characteristics of a cell at resting potential?

negative on inside, positive on outisde

What chemical is released at the neuromuscular junction?

acetylcholine

What are channels in the plasma membrane that are constantly open called?

leak ion channels

When a muscle is relaxed, what covers the sites on actin?

tropomyosin

What needs to happen for a muscle to be able to be used for extended periods of time?

rotating through motor units

What is the power stroke?

myosin heads pull on the actin

What molecule is released from the sarcoplasmic reticulum during muscle contraction?

calcium

What caused the depolarization of the cell membrane?

rapid influx of sodium

What is the all or none principle?

a stimulus either causes an action potential or it doesn't

What is required for muscle contraction?

ATP

What does a motor unit contain?

a single motor neuron and all muscle fibers innervated by it

What is the strength of contraction in a multiple motor unit summation dependent on?

the number of motor units that are recruited

What is sustained muscle contraction called?

tetanus

What are the characteristics of slow twitch muscle fibers?

contain more mitochondria and myoglobin (dark muscle)

What are the characteristics of fast twitch muscle fibers?

fewer and smaller mitochondria (white muscle)

What is hypertrophy?

increase in the size of muscle fibers

What is the cause of muscle fatigue?

running out of acetylcholine

What are the steps of muscle contraction?

-action potential on a motor neuron causes voltage gated calcium channels to open at the synaptic knob
-calcium influx into the synaptic knob causes migration of vesicles and release of ACh into the synaptic cleft
-acetylcholine binds to ligand-gated sodium channels on the sarcolemma
-sodium influx into muscle fiber causes depolarization of sarcolemma
-depolarization of T tubules opens voltage gated calcium channels in the membrane of sarcoplasmic reticulum
-calcium enters sarcomere and leads to cross bridge formation
-myosin utilizes ATP to slide actin filaments resulting in tension production

What causes the striped appearance in skeletal muscle?

sarcomeres

Why does external tension lag behind internal tension?

the tendons are highly elastic

What must happen for movement to occur?

tension must overcome resistance

A typical muscle stores enough ATP to sustain contraction for how many seconds?

two seconds

What happens to the inside of a neuron during depolarization?

it becomes less negative

What are the components of the CNS?

brain and spinal cord

What does somatic sensory refer to?

skin receptors

What is the main function of the sensory division of the PNS?

convey action potentials to the CNS

Which type of neuroglia are found in the CNS?

ependymal cells, astrocytes, oligodendrocytes, microglia

What type of glial cells line the central canal and produce cerebrospinal fluid?

ependymal cells

Action potentials propagate through myelinated axons how much faster than non-myelinated axons?

100 times faster

What maintains the resting transmembrane potential?

the sodium-potassium exchange pump

When are potassium channels open?

depolarized

When does an action potential occur?

when the axon hillock reaches threshold level

What prevents an action potential from going backwards?

the refractory period

Where are neurotransmitters released?

presynaptic terminal

What is similar to the resting membrane potential?

a dam holding back water

What happens when two EPSP'S arrive simultaneously at two different dendrites of the same neuron?

spatial summation occurs

What is the junction of a neuron with another cell called?

synapse

What is the gap between the cells forming myelin sheath called?

node of ranvier

What cell type would grow and be most active during a microbial infection of the brain?

microglia

What is made possible by hyperpolarization?

the refractory period

What do action potentials depend on?

voltage-gated ion channels

Where are graded potentials found?

immediately under a synapse, on the soma, on the dentrites

What does an IPSP (inhibitory postsynaptic potential) cause?

hyperpolarization of the target cell

What is the typical strength of an EPSP or IPSP?

1 mV

Can action potentials travel backwards on the axon?

no

Can neurotransmitters be excitatory and inhibitory?

yes

What do neurotransmitters that act via indirect mechanisms often employ?

cAMP as a second messenger

What are some examples of neurotransmitters?

GABA, dopamine, serotonin, acetylcholine

What do graded potentials depend on?

ligand-gated ion channels

Information processing is achieved using what?

IPSPs, EPSPs, neuronal pools

What does divergence require?

collateral axons

What kind of neurons are motor neurons?

multipolar neurons

Where are excitable membranes found?

axons

What are some examples of effectors?

muscles and glands

What are the two command and control system?

nervous and endocrine

What makes saltatory propagation possible?

myelin sheath