10) when voltage - gated ( k^{+} ) channels open on the conductive segment of a neuron,
a) potassium enters, repolarizing the cell to a positive value.
b) potassium exits, repolarizing the cell to a negative value.
c) potassium exits, depolarizing the cell from - 70mv to + 30mv.
d) potassium enters, depolarizing the cell to a positive value.
e) potassium enters, repolarizing the cell to a negative value.
11) inhibitory postsynaptic potentials (ipsps) are associated with which of the following?
a) depolarization of the cell membrane
b) repolarization of the cell membrane
c) no change in the cell membrane potential
d) hyperpolarization of the cell membrane
12) synthesized by the combined action of the skin, kidneys, and liver, ______ causes an increase in blood calcium.
a) growth hormone
b) testosterone
c) calcitonin
d) calcitriol (vitamin d)
13) the ______ division tends to prepare the body for \emergency\ situations.
a) parasympathetic
b) somatic motor
c) sensory afferent
d) sympathetic
14) what is the purpose of motor nerve varicosities as they relate to smooth muscle?
a) they link the thin filaments to the inside of the sarcolemma in smooth muscle.
b) they reabsorb the decomposition products of acetylcholine after acetylcholinesterase breaks it down.
c) they release neurotransmitter onto smooth muscle cells.
d) they enable each cardiac myocyte to directly stimulate its neighbors.
e) they prevent single - unit smooth muscle cells from pulling apart.
15) spicules and trabeculae are found in ______
a) compact bone
b) yellow bone marrow
c) red bone marrow
d) spongy bone
16) intramembranous ossification produces the ______
a) short bones of the wrist
b) long bones of the limbs
c) flat bones of the skull
d) irregular bones of the vertebrae
e) short bones of the ankle
17) in endochondral ossification, the precursor connective tissue is ______, which is replaced by bone.
a) red bone marrow
b) transitional epithelium
c) hyaline cartilage
d) fibrous membranes
18) what is the primary site on a postsynaptic neuron for receiving signals from other neurons?
a) the dendrites
b) the synaptic knobs
c) the axon collaterals
d) the axons
19) local potentials are ______, whereas action potentials are ______.
a) produced by ligand - gated channels; \all or none\
b) produced by voltage - gated channels; produced by ligand - gated channels
c) self - propagating; local
d) nondecremental; decremental
20) in skeletal muscle, the term that describes the alternating light and dark bands is
a) myofibrils
b) myoblasts
c) strabismus
d) striations
e) tetanus
21) which glial cell is found wrapped around nerve fibers in the pns?
a) ependymal cells
b) neurolemmocytes (schwann cells)
c) nodes of ranvier
d) oligodendrocytes
e) satellite cells

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# Brief Explanations:
10) When voltage - gated $K^{+}$ channels open, $K^{+}$ exits the cell. During repolarization, the membrane potential returns to a negative value (resting potential). Depolarization is when the membrane potential becomes more positive (e.g., due to $Na^{+}$ influx).
11) Inhibitory postsynaptic potentials (IPSPs) make the membrane potential more negative (hyperpolarized), which makes it less likely for an action potential to occur. Depolarization makes the membrane more positive, repolarization is the return to resting potential after depolarization, and no - change is not the case for IPSPs.
12) Calcitriol (Vitamin D) is synthesized by the combined action of the skin (in the presence of UV light, 7 - dehydrocholesterol is converted to cholecalciferol), liver (hydroxylation of cholecalciferol), and kidneys (further hydroxylation). It increases blood calcium levels by enhancing calcium absorption in the intestines, reabsorption in the kidneys, and mobilization from bones. Growth hormone is involved in growth and metabolism, testosterone is a sex hormone, and calcitonin decreases blood calcium.
13) The sympathetic division is the "fight - or - flight" system. It prepares the body for emergency situations by increasing heart rate, dilating pupils, etc. The parasympathetic division is the "rest - and - digest" system. The somatic motor is involved in voluntary muscle control, and sensory afferent is for carrying sensory information.
14) Motor nerve varicosities release neurotransmitter onto smooth muscle cells. Linking thin filaments is not their function. Reabsorbing acetylcholine decomposition products is not their role (acetylcholinesterase breaks down acetylcholine, and reuptake mechanisms are different). Cardiac myocytes have intercalated discs for direct stimulation, and preventing single - unit smooth muscle cells from pulling apart is not their function.
15) Spicules and trabeculae are found in spongy bone. Compact bone is more solid, yellow bone marrow is in the medullary cavity (mainly fat), and red bone marrow is where hematopoiesis occurs (but spicules and trabeculae are structural features of spongy bone).
16) Intramembranous ossification produces flat bones of the skull. Short bones of the wrist and ankle are usually formed by other ossification processes. Long bones of the limbs are formed by endochondral ossification, and irregular bones of the vertebrae also have a different ossification pathway.
17) In endochondral ossification, the precursor connective tissue is hyaline cartilage. Red bone marrow is involved in blood cell formation, transitional epithelium is in the urinary tract, and fibrous membranes are not the precursor for endochondral ossification.
18) The primary site on a postsynaptic neuron for receiving signals from other neurons is the dendrites. Synaptic knobs are on the presynaptic neuron, axon collaterals are branches of the axon (not the main receiving site), and axons are for transmitting action potentials away from the cell body.
19) Local potentials are produced by ligand - gated channels (e.g., neurotransmitter binding) and action potentials are "all or none" (once the threshold is reached, a full - fledged action potential occurs; if not, nothing). Voltage - gated channels are mainly involved in action potential propagation (after the initial depolarization from ligand - gated channels in many cases). Local potentials are decremental (lose strength with distance), and action potentials are non - decremental.
20) In skeletal muscle, the term that describes the alternating light and dark bands is striations. Myofibrils are the contractile elements, myoblasts are muscle - forming cells, strabismus is an eye disorder, and tetanus is a muscle condition (sustained contraction).
21) Neurolemmocytes (Schwann cells) are found wrapped around nerve fibers in the PNS. Ependymal cells are in the CNS (line ventricles and central canal), Nodes of Ranvier are gaps in the myelin sheath (not cells), Oligodendrocytes myelinate CNS axons, and Satellite cells are around neuron cell bodies in the PNS (not wrapped around nerve fibers).

# Answer:
10) B. potassium exits, repolarizing the cell to a negative value
11) D. Hyperpolarization of the cell membrane
12) D. calcitriol (Vitamin D)
13) D. sympathetic
14) C. They release neurotransmitter onto smooth muscle cells
15) D. spongy bone
16) C. flat bones of the skull
17) C. hyaline cartilage
18) A. The dendrites
19) A. produced by ligand - gated channels; "all or none"
20) D. striations
21) B. Neurolemmocytes (Schwann cells)

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