BIO 212 Exam 4

Amino acids

- Glutamate most widespread excitatory neurotransmitter - GABA (gamma aminobutyric acid) most common inhibitory neurotransmitter

neuropeptides

- Often called neuromodulators - can alter response of postsynaptic neuron to other neurotransmitters - Opiate peptides - endorphins

Biogenic amines

- Widespread physiological effects and psychoactive - Includes norepinepherine (adrenalin), histamine, serotonin, dopamine - Abnormally high or low levels associated with a variety of mental illnesses (schizophrenia, depression) and neurodegenerative disease (PD)

What are the four classes of neurotransmitters?

Acetylcholine, Biogenic amines, amino acids and neuropeptides

Voltage-gated ion channels

Are channels that open and close in response to changes in voltage across the membrane.

Ligand-gated ion channels

Are channels that open and close when ligands(such as neurotransmitters) bind to them

Action Potentials

Are nerve impulses that carry an electrical signal along an axon. In contrast to a graded potential, an action potential is always a large depolarization

Which of the following is NOT important in chemical synapses? A. NeurotransmiJers B. Gap junctions C. Secretory vesicles D. Specific neurotransmitter receptors E. Voltage-gated Ca2+ channels

B

What are the two types of synapses and what do they do?

1. Electrical - electric charge freely flows through gap junctions from cell to cell 2. Chemical - neurotransmitter acts as signal from presynaptic to postsynaptic cell

Excitation-contraction coupling

1.Action potential initiated by neural impulse 2.Impulse leads skeletal muscle cells to produce their own action potentials 3.Opens voltage-dependent Ca2+ channels in the SR 4.Causes Ca2+ release into the cytosol 5.Triggers muscle contraction

What are the 3 factors that are primarily responsible for the resting membrane potential and what do they do?

1.Sodium-potassium pump-continually moves sodium ions out of the cell and potassium ions into the cell by use of ATP to transport 3 Na+ out of the cell for every two K+ it moves into the cell. 2.Ungated ion-specific channels-allow passive movement of Na+ and K+, there are normally way more ungated K+ channels as there are Na+ channels. 3.Presence of negatively charged molecules(such as proteins) that are abundant within the cell that contribute some negative electric charge to the inside of the cell.

What do the two heads of the mysosin do?

2 heads form cross-bridges with actin (each head contains binding sites for actin and ATP). Molecules are oriented in opposite directions to bring thin filaments toward center of sarcomere

what is the structure of actin?

2 intertwined helical chains

Graded potential

A depolarization or hyperpolarization that varies depending on the strength of the stimulus. For example, a large change in membrane potential will occur when a strong stimulus opens many channels

Why did Dr. Westwood experience paralysis after eating the pufferfish meal? A. TTX causes motor neurons to fire continuously, overloading the brain with signals, resulting in paralysis. B. TTX causes motor neurons to stop firing, preventing communication with the muscles, resulting in paralysis. C. TTX causes sensory neurons to stop firing preventing communication with the brain, resulting in paralysis. D. TTX causes sensory neurons to fire continuously, overloading the brain with signals, resulting in paralysis. E. None of the above explain why Dr. Westwood experienced numbness after his pufferfish meal.

B

Excitatory postsynaptic potential (EPSP)

Brings membrane closer to threshold potential (depolarization)

Dr. Westwood experienced numbness after eating the pufferfish meal because TTX causes: A. Motor neurons to fire continuously, overloading the brain with signals, resulting in numbness. B. Motor neurons to stop firing, preventing communication with the brain, resulting in numbness. C. Sensory neurons to stop firing preventing communication with the brain, resulting in numbness. D. Sensory neurons to fire continuously, overloading the brain with signals, resulting in numbness. E. None of the above explain why Dr. Westwood experienced numbness after his pufferfish meal.

C(numness, lack of feeling, lack of sensing)

glia

Cells that surround the neurons, perform various functions

The toxin found in the bird feathers: A. Is used by the birds to deter predators. B. Is found in birds that have eaten poison arrow frogs. C. Is the same toxin found in pufferfish flesh. D. Affects voltage sensitive ion channels. E. Affects voltage sensitive potassium channels.

D

The response of a postsynaptic cell is determined by: A. The type of neurotransmitter released at the synapse. B. The type of receptors the postsynaptic cell has. C. The number of Na+ channels in the postsynaptic membrane. D. The number of K+ channels in the postsynaptic membrane. E. All of the above.

E

What kind of potentials are particularly important for the function of sensory neurons?

Graded potentials, because sensory neurons must distinguish between strong and weak stimuli coming into the organism from the environment

How does ion flow work considering only an electrical gradient?

If looking at a positive ion such as K+, it will flow in which ever direction there is a more negative charge(because positive charge is attracted to negative charge and vice versa).

What are synapses?

Junction where axon terminal meets another neuron, muscle cell, or gland

What 3 ions are most critical for establishing the resting potential?

Na+, K+, and Cl-, and to a lesser extent, intracellular anions such as negatively charged proteins

Is Na+ concentration greater inside or outside of the neuron cell?

Outside/extracellular

What is the structure of myosin?

Protein with two heads and a tail, the tails align to form the thick filament

Acetylcholine

Released at neuromuscular junctions, excitatory in skeletal muscles (also in brain)

are neuron cells polarized?

yes, because there is a separation of charge across their membranes(the resting potential inside of a neuron cell is more negative than the outside)

Inhibitory postsynaptic potential (IPSP)

Takes membrane farther from threshold potential (hyperpolarization)

Is the inside of a neuron more positively or negatively charged in the cell's resting state?

The interior of the cell has a more negative charge than the exterior

What does the Nernst equation allow neuroscientists to predict?

When an ion is or isn't in equilibrium

Can an electrical gradient be balanced by a chemical gradient and vice versa?

Yes, if for example, an electrical gradient favors ion movement inside the cell, but the chemical gradient favors ion movement outside of the cell, then these opposing forces could cause an equilibrium in which there is no net diffusion.

What are thin filaments composed of?

actin and regulatory proteins

hydrostatic skeleton

combination of muscles and fluid, like in earthworms

If cytosolic Ca2+ levels are high and there is adequate ATP, muscles will ...

contract

Ca2+ release triggers...

contraction

myofibrils

cylindrical bundles of actin and myosin filaments

Where is smooth muscle used?

digestive organs and in blood vessels

What are muscles that straighten a limb?

extensors

exoskeleton

external, chitin, segmented for movement. In arthropods

what is an example of a ball and socket joint?

femur and ilium (leg movement)

What are muscles that bend a limb?

flexors

Is K+ concentration greater inside or outside of the neuron cell?

inside/intracellular

are anions such as negatively charged proteins found in higher concentration, inside or outside of the neuron cell?

inside/intracellular

What returns Ca2+ to the sarcoplasmic reticulum(SR)

ion pumps

How does ion flow work considering only a chemical gradient?

ions will flow from high concentration to a lower concentration

The toxin, tetrodotoxin, in the pufferfish did what?

it blocked voltage-gated sodium ion channels, which eventually caused numbness, trouble breathing, nausea and signs of paralysis

endoskeleton

minerals give firmness. present in vertebrates

what is another word for muscle cell?

muscle fiber

What are thick filaments composed of?

myosin

Depolarization

occurs when the cell membrane becomes less polarized(letting Na+ in)

Hyperpolarization

occurs when the cell membrane becomes more polarized (negatively charged)

is Cl- concentration greater inside or outside of the neuron cell?

outside, extracellular

Tropomyosin

rod-shaped molecule that forms chains. In the absence of Ca2+, they partially cover the myosin-binding site on each actin molecule, thereby preventing cross-bridges from making contact with actin. Together troponin and tropomyosin cooperate to block access to myosin-binding sites on actin molecules in the relaxed muscle fiber.

What is the repeating unit in myofibrils?

sacromeres

Troponin

small, globular shaped protein that is bound to both tropomyosin and actin, holding tropomyosin in its blocking position. Together troponin and tropomyosin cooperate to block access to myosin-binding sites on actin molecules in the relaxed muscle fiber.

Where is Ca2+ stored and released from?

the sarcoplasmic reticulum (SR)(a membrane network that surrounds myofibrils)

What do tendons do?

they link skeletal muscle to bones

what is an example of a pivot joint?

vertebra

When has the cross-bridge formed?

when the myosin head binds to actin

what is an example of a hinge joint?

where the humerous attaches to your ulna and radius (elbow)

do muscle cells contain multiple nuclei?

yes

is skeletal muscle striated?

yes