Mastering Anatomy Review

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Why was the hypophysectomized rat's metabolic rate lower after hypophysectomy?

The thyroid gland in this rat wasn't being stimulated by TSH, therefore it wasn't making enough thyroxine.

Which of the following hormones has intracellular receptors?

cortisol (steroid-based)

What is the mechanism of action of lipid-soluble hormones?

activation of mRNA, which increases protein synthesis in the cell

After a lipid-soluble hormone is bound to its intracellular receptor, what does the hormone complex do?

acts as a transcription factor and binds to DNA, activating a gene

Which hormone's receptor is always bound to DNA, even when the receptor is empty?

Thyroid hormone (lipid soluble)

What keeps intracellular receptors from binding to DNA before a hormone binds to the receptor?

chaperone proteins (chaperonins)

What type of hormones bind to receptors located on the cell membrane?

water-soluble hormones, such as insulin and epinephrine

Which intracellular substance degrades cAMP, thus inactivating the response to a hormone?

Phosphoidesterase

Growth factor hormones, such as insulin, bind to which type of receptor?

Tyrosine Kinase receptors

Which is the correct order of events for hormones activating G proteins?

activation of G protein, binding of GTP, activation of adenylate cyclase, conversion of ATP to cAMP

Which second messenger causes the release of calcium from the endoplasmic reticulum?

IP3

Which of the following adrenergic receptors increase cAMP levels?

beta receptors

Ions are unequally distributed across the plasma membrane of all cells. This ion distribution creates an electrical potential difference across the membrane. What is the name given to this potential difference?

Resting Membrane Potential

Sodium and potassium ions can diffuse across the plasma membranes of all cells because of the presence of what type of channel?

Leak channels

On average, the resting membrane potential is -70mV. What does the sign and magnitude of this value tell you?

The inside surface of the plasma is much more negatively charged than the outside surface.

The plasma membrane is much more permeable to K than to Na. Why?

There are many more K leak channels than Na leak channels in the plasma membrane

The resting membrane potential depends on two factors that influence the magnitude and direction on the Na and K diffusion across the plasma membrane. Identify these two factors.

The presence of concentration gradient and leak channels.

What prevents the Na and K gradients from dissipating?

Na-K ATPase

Where do most action potentials originate?

Initial segment (axon hillock)

What opens first in response to a threshold stimulus?

Voltage-gated channels

What characterizes depolarization, the first phase of the action potential?

The membrane potential changes from a negative value to a positive value.

What characterizes repolarization, the second phase of the action potential?

Once the membrane depolarizes to a peak value of +30mV, it depolarizes to its negative resting value of -70mV.

What event triggers the generation of an action potential?

The membrane potential must depolarize from the resting voltage of -70mV to a threshold value of -55mV.

What is the first change to occur in response to a threshold stimulus?

Voltage-gated Na channels change shape, and their activation gates open.

What type of conduction takes place in unmyelinated axons?

Continuous conduction.

An action potential is self-regenerating because-

depolarizing currents established by the influx of Na flow down the axon and trigger an action potential at the next segment.

Why does regeneration of the action potential occur in one direction, rather than in two directions?

The inactivation gates of voltage-gated Na channels close in the node, or segment, that has just fired an action potential.

What is the function of the myelin sheath?

The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals.

What changes occur to voltage-gated Na and K channels at the peak of depolarization?

Inactivation gates of voltage-gated Na channels close, while activation gates of voltage-gated K channels open.

In which type of axon will velocity of action potential conduction be fastest?

Myelinated axons with the largest diameter.

In a synapse, neurotransmitters are stored in vesicles located in the-

presynaptic neuron

An action potential releases neurotransmitter from a neuron by opening which of the following channels?

Voltage-gated Ca channels

Binding of a neurotransmitter to its receptors opens --- channels on the --- membrane

chemically gated, postsynaptic

Binding of the neurotransmitter to its receptor causes the membrane to

either depolarize or hyperpolarize

The mechanism by which the neurotransmitter is returned to the presynaptic neuron's axon terminal is specific for each neurotransmitter. Which of the following neurotransmitters is broken down by an enzyme before being returned?

Acetylcholine

Which type of white matter tract connects the two cerebral hemispheres?

Commissures

Which of the following best describes the hypothalamus?

Visceral control center of the body

Which part of the brain stem houses the reflex centers for respiration and cardiovascular functioning?

Medulla Oblongata

Spinal nerves are all classified as

mixed nerves

Nerves that only carry impulses away from the central nervous system (CNS) are called

motor nerves

The majority of the cranial nerves attach to the

brain stem

Select the statement that is the most correct

Ganglia associated with afferent nerve fibers contain cell bodies of sensory neurons.

Transduction refers to conversion of

stimulus information to nerve impulses

Which of the following is not an aspect of sensory perception?

quality estimation

Which receptors adapt most slowly?

nociceptors

---- are receptors that can respond to changes in pressure

Mechanoreceptors

Feeling a gentle caress on your arm would likely involve all of the following except

Pacinian corpuscles

The synapse of the olfactory nerves with the mitral cells is called a

glomerulus

Most taste buds are located

on the tongue

Which of the following is not a requirement for something to be tasted?

The tastant must contact the basal cells of the taste buds.

Which of the following is true about gustatory receptors?

Complete adaptation occurs in about one to five minutes.

Which of the following types of neurons are replaced throughout adult life?

Olfactory receptor cells

The cells of the retina in which action potentials are generated are the

ganglion cells

During accommodation,

the ciliary muscle contracts, causing the lens to bulge

In the visual transduction pathway of the retina,

neurotransmitter from the photoreceptor causes IPSPs in the bipolar cell.

Which of the following is NOT a possible cause of conduction deafness?

death/damage to hair cells of the organ of Corti.

Some people get motion sickness because of mismatched sensory information sent to the ----- center of the ----

vestibular, medulla oblongata

The two types of receptors that bind acetylcholine are --- and --- receptors

Nicotinic, muscarinic

Which division of the nervous system has short preganglionic neurons?

sympathetic

Once a preganglionic axon reaches a trunk ganglion, one of three things can happen to the axon. Which of the following is not one of these things?

The axon can emerge from the sympathetic trunk to synapse in another axon.

The parasympathetic division uses only --- as a neurotransmitter in the ganglionic neurons

acetylcholine

Sweat glands are innervated by the --- fibers alone

sympathetic

When the vagus nerve was stimulated, what happened to the heart rate?

heart rate decreased

What do you think would happen to heart rate if the vagus nerve was severed?

heart rate would increase

Atropine is an antagonist on which of the following receptors?

muscarinic-AChR

Epinephrine potentiates which division of the autonomic nervous system?

sympathetic nervous system

Which of the following would increase heart rate?

administering epinephrine, administering atropine

The notable hardness of bone is attributed to

the presence of inorganic hydroxyapatites

The osteon is

the structural unit of compact bone

What is an osteoid?

the organic part of the matrix of bone

Osteoblasts

from new bone

Bones are constantly undergoing resorption for various reasons. Which of the following cells accomplishes this process?

osteoclast

Wolff's las is concerned with

the thickness and shape of a bone being dependent on stresses placed upon it

The correct order (from start to finish) of fracture repair is

Hematoma formation, fibrocartilaginous callus formation, bony callus formation, bone remodeling

A long bone forms by a process known as ---- ossification

endochondral

Ossification of the ends of long bones

is produced by secondary ossification centers.

In some cases the epiphyseal plate of the long bones of children closes too early. What might be the cause?

elevated levels of sex hormones.

Which hormone increases osteoclast activity to release more calcium ions into the bloodstream?

parathyroid hormone

Why should people who live in the north take supplemental calcium with vitamin D?

People who live in the north have decreased amount of sunlight exposure. Vitamin D is manufactured by skin cells when exposed to sunlight, and is needed for absorption of dietary calcium.

Mrs. Sanchez makes an appointment to see her doctor for pain in her abdominal area. Tests and X rays reveal kidney stones as well as bones with a moth-eaten appearance. Further questioning reveals a medical history of abnormal reflexes and weakness. What is the problem and what treatment would be recommended?

Hyperparathyroidism resulting from a parathyroid gland tumor, the treatment is removal of the tumor

Which of the following is true about calcium homeostasis?

Parathyroid hormone is the single more important regulator of calcium levels in the blood

John is a 26-year-old man who begins to notice a progressive enlargement of feet, hands, cranium, nose, and lower jaw bone. His doctor recommends irradiation of the pituitary gland. What is the most likely diagnosis, and what caused this condition?

The diagnosis is acromegaly. The condition results from excess secretion of growth hormone from the pituitary gland post puberty and after the epiphyseal plates of the long bones has fused.

In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?

acetylcholine (ACh)

When an action potential arrives at the axon terminal of a motor neuron, which ion channels open?

Voltage-gated calcium channels

What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?

exocytosis

The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur?

Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate.

How is acetylcholine (ACh) removed from the synaptic cleft?

Acetylcholinesterase (AChE, an enzyme)

The action potential on the muscle cell leads to contraction due to the release of calcium ions. Where are calcium ion stored in the muscle cell?

Terminal cisternae of the sarcoplasmic reticulum

Excitation-contraction coupling is a series of events that occur after the events of the neuromuscular junction have transpired. The term excitation refers to which step in the process?

Excitation, in this case, refers to the propagation of action potentials along the sarcolemma.

Excitation of the sarcolemma is coupled or linked to the contraction of a skeletal muscle fiber. What specific event initiates the contraction?

Calcium release from the sarcoplasmic reticulum initiates the contraction

One component of the triad is a t-tubule. How does activity in the T tubule impact the other two components?

The T tubule is linked to tow adjacent terminal cistern of the sarcoplasmic reticulum by a series of proteins

What is the name given to the regularly spaced infoldings of the sarcolemma?

transverse or T tubules

A triad is one portion of a T tubule plus two adjacent terminal cisternae of the sarcoplasmic reticulum. What is the significance of this arrangement?

Action potentials propagating down the t tubule trigger the release of calcium ions by the terminal cisternae

What is the relationship between the number of motor neurons recruited and the number of skeletal muscle fibers innervated?

Typically, hundreds of skeletal muscle fibers are innervated by a single motor neuron.

What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell?

Arrival of an action potential

The binding of calcium to which molecule causes the myosin binding sites to be exposed?

Troponin

A myosin head binds to which molecule to form a cross bridge?

Actin

What causes the myosin head to disconnect from actin?

binding of ATP

What energizes the power stroke?

hydrolysis of ATP

Opening and then closing of the Na channels

Depolarization phase in the generation of an action potential

All voltage-gated Na and K channels are closed

The resting state of a neuron

Opening of potassium gates and the rushing out of K

The repolarization phase in an action potential

The sodium channels remain opened

The absolute refractory period

Increased potassium efflux as a result of sluggish closure of the potassium gates

The phase in action potential known as the "after hyper polarization"

Reflexes

Rapid automatic responses to a stimulus in which the particular stimulus always produces the same motor response

Numerous nerve impulses arriving at a synapse at closely timed intervals exert a cumulative effect

Temporal summation

Simultaneous stimulation of many terminals, distributed widely over the surface of a postsynaptic neuron

Spatial summation

An insufficient stimulus

Subthreshold stimulus

Any stimulus above this intensity will result in an action potential in a neuron

Threshold stimulus

Somatic nervous system

Conducts impulses from CNS to skeletal muscles

Autonomic nervous system

Conducts impulses from CNS to internal organ muscles

Central nervous system

Consists of brain and spinal cord

Peripheral nervous system

Consists of nerves carrying impulses to and from brain and spinal cord

Presynaptic calcium influx

Triggers neurotransmitter release

Synaptic cleft

Separates presynaptic terminal from postsynaptic membrane

Receptor/Channel

Triggers voltage change in postsynaptic neuron

Neurotransmitter

Binds to a postsynaptic receptor/channel

Acetylcholine

Excites skeletal muscle

Norepinephrine

Main neurotransmitter of sympathetic nervous system

Dopamine

"Feel Good" transmitter, deficient in parkinson's disease

Serotonin

"Mood" transmitter, target of Prozac to relieve depression

GABA

generally inhibitory, found throughout CNS

Endorphins

Peptides with inhibitory, opiate-like actions

Somatic afferent fibers

skin, skeletal muscles, and joints to CNS

Visceral afferent fibers

organs in the ventral body cavity to CNS

Somatic motor fibers

CNS to skeletal muscles

Visceral motor fibers

CNS to smooth muscles, cardiac muscles, and glands

Which of the following statements concerning inhibitory synapses (IPSPs) is correct?

Postsynaptic membrane becomes more permeable to potassium and chloride

The sodium-potassium ion pump will

pump three sodium ions out of the cell for every two ions of potassium it brings into the cell

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