Human Physiology Exam 4

actin

Thin contractile protein involved in cross-bridge formation, comes in filamentous or globular forms.

synaptic vesicles

Store neurotransmitters, and following Ca++ drivien signal, dump neurotransmitters into the synapse.

synaptic terminal

The structure at the end of the axon that contains neurotransmitters and vesicles.

sarcomere

The functional unit of the muscle fiber that includes the A-band, I-band, H-zone and the M-line.

Sodium (Na+)

The ion responsible for depolarizing the muscle membrane by traveling through the nACH receptor, down its electrochemical gradient.

ryanodine receptor

Located on the sarcoplasmic reticulum and once-opened, allows Ca++ flow from the sarcoplasmic reticulum into the sarcomplasm.

myosin

Thick filamentous contractile protein involved in cross-bridge formation, has a club-like appearance with a "head."

Acetycholine (ACh)

A neurotransmitter derived from choline; responsible for sending the excitatory signal in the neuromuscular junction (NMJ).

t-tubule

These invaginations allow depolarization of the muscle membrane to quickly penetrate from the sarcolemma to the myofibril.

motor end plate

Large and complex terminal formation by which an axon of a motor neuron establishes synaptic contact with a skeletal muscle fiber, transmitting neural impulses to a muscle.

sarcolemma

The plasma membrane of a muscle fiber.

acetylcholinesterase (AChE)

The enzyme responsible for stopping the ACh signal. functions by metabolizing ACh into choline, which is recycled, and acetate.

nicotinic acetylcholine receptor

Responsible for opening a ligand-gated Na+ channel in the muscle membrane when the proper ligand binds to it.

dihydropyridine receptor

A L-type calcium channel in the muscle membrane, activated upon depolarization, couples depolarization signal to release of calcium.

depolarization

An electrical change which brings the relative charge of the inside of the cell more positive; necessary for transmission of electrical impulses within a cell, or from one cell to another.

sarcoplasmic reticulum

Modified endopolasmic reticulum, stores and release calcium.

What is the role of AChE in the NMJ?

Serves as an enzyme that breaks down the neurotransmitter ACh, thus stopping the signal from nerve cells to muscle fibers.

What is the mechanism of action of sarin or a sarin-like chemical?

Inactivates AChE in the synaptic cleft and causes ACh to remain in the synapse for a longer period of time.

Na+ levels inside the cell would drastically increase due to the channels remaining open for longer periods of time.

How would exposure to a sarin-like poison affect the amount of Na+ going into the muscle cell?

How would exposure to sarin or sarin-like chemical affect Ca++ levels inside the sarcoplasmic reticulum?

Ca++ levels inside the sarcoplasmic reticulum decrease.

How do altered Ca++ levels affect the position of the actin and myosin filaments?

The increased Ca++ levels cause prolonged muscle contraction.

How would antibodies for ACh receptors affect the action at the neuromuscular junction (NMJ)?

Antibodies to the receptors would block the action of ACh on the muscle cell.

How would antibodies against ACh receptors affect the influx of Na+ into the cell?

Na+ levels inside the cell would decrease.

How would antibodies against the ACh receptors affect the levels of Ca++ inside the sarcoplasmic reticulum? And, what does this do to muscle contraction?

Ca++ remains inside the sarcoplasmic reticulum, muscle contraction cannot occur.

Cardiac muscles differ from skeletal muscles in that they __________. 

contain intercalated discs

The function of transverse tubules is to

rapidly move action potentials to the interior of the muscle fiber.

A state of maximal muscle contraction is called _____________. 

tetanus

Smooth muscle uses the troponin-tropomyosin system for contraction, just like skeletal muscles. 

False

Smooth muscle differs from skeletal and cardiac muscles in that they __________________?

lack myofibrils

The cell membrane of a muscle fiber is called ______________. 

sarcolemma 

This type of muscle fiber is slow to fatigue, used for standing and walking, and primarily uses aerobic respiration to produce ATP. 

slow-twitch fibers 

The neurotransmitter _________________ is released at the neuromuscular junction.

acetylcholine

Before myosin can associate with actin, the protein ___________ must be moved.

tropomyosin

Lipophilic signal molecules requires receptors in the cell membrane. 

False

This hormone is released from the beta cells of the pancreas and controls blood glucose.

insulin

Insulin, glucagon, parathyroid hormone, oxycocin, vasopresin, growth hormone, adrenocorticotropic hormone are all ____________ hormones. 

peptide

Typically, when steroid hormones bind to their receptors,

gene transcription may increase or decrease

For cells, long distance communication can be achieved by ______________. 

signaling through the release of hormones

Place the following statements in the correct sequence, beginning with tonic release:

1. thyroid releasing hormone is released from the hypothalamus

2. anterior pituitary is signaled

3. cortisol is released

4. ACTH is released

5. hormone travels through the hypothalamic-hypophyseal portal system

1, 5, 2, 4, 3

A catecholamine or peptide hormone binds to receptors on the surface of a cell.

Second messengers are activated when

When adenylyl cyclase is activated what is formed

cAMP

_______________ hormones use second messenger systems. 

lipophobic

This anterior pituitary hormone will stimulate the adrenal cortex to secrete cortisol.

adrenocorticotropic hormone