BI 332 Quizzes (Weeks 5 - 10)

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According to the image above, what happens inside the liver cells when cAMP levels are high? (select all that apply) - More glucose will be released from storage - Less glucose will be moved into storage - More glycogen will be made - Less glycogen will be made - More glycogen will be broken down

- More glucose will be released from storage - Less glucose will be moved into storage - More glycogen will be made - Less glycogen will be made - More glycogen will be broken down

At minimum, how many neurons extend from the CNS to visceral targets served by the autonomic nervous system (how many in series, not how many to all the targets in the whole body)? - eleventy billion - 1 - 2 - 3

2. Correct! 2 motor neurons extend from the CNS to visceral targets served by the autonomic nervous system. The preganglionic neuron has its cell body in the CNS, its axon extends to the periphery. Out in the periphery it will not synapse with a target cell, but instead with a postganglionic neuron cell body. This synapse will occur in an autonomic ganglion. From the ganglion, the postganglionic axon will extend to the target.

Usually, which of the following hormones will bind to an intracellular receptor? - A water soluble hormone that is attached to a blood transport protein - A water soluble hormone that is not attached to a blood transport protein - A fat soluble hormone that is attached to a blood transport protein - A fat soluble hormone that is not attached to blood transport protein

A fat soluble hormone that is not attached to blood transport protein. Right! Usually, fat soluble hormones diffuse through the cell membrane, bind to an intracellular receptor and require a blood transport protein to get around the body. However, in order for the fat soluble hormone (like thyroxine, estrogen, testosterone) to affect a cell, the blood transport protein must release the hormone. Water soluble hormones do not require transport proteins but must bind to a cell membrane receptor for effect.

These traces represent activity in two adjacent ganglion cells. The on/off represents when a light is shown upon the photoreceptors that relay signals to these ganglion cells. Which trace best represents the transmembrane potential of ganglion cell 1 axon when the photoreceptors are in the dark (light is off)?

AP's. Right! In the dark, the photoreceptor depolarizes and causes neurotransmitter release. The neurotransmitter causes the bipolar cell to hyperpolarize because the neurotransmitter creates IPSPs on the bipolar cell. The bipolar cell does not release NT to the ganglion cell. In the homework, it was indicated that ganglion cells do not fire action potentials unless the bipolar cells released a NT causing them to. However, this was an oversimplification. In fact, ganglion cells fire action potentials, even without stimuli from the bipolar cells. This spontaneous depolarization causes a background action potential generation rate in ganglion cells. Then, when the bipolar cells do fire, they can inhibit the ganglion cells or excite them, changing action potential rate. This will be information sent to the brain that we can then interpret.

These traces represent activity in two adjacent ganglion cells. The on/off represents when a light is shown upon the photoreceptors that relay signals to these ganglion cells. Which trace best represents the transmembrane potential of ganglion cell 2 axon when the photoreceptors are in the dark (light is off)?

These traces represent activity in two adjacent ganglion cells. The on/off represents when a light is shown upon the photoreceptors relaying signals to these ganglion cells. Which trace best represents the transmembrane potential of ganglion cell 1 axon when the photoreceptors are in the dark?

Action potential graph. Right! In the dark, the photoreceptor depolarizes and causes neurotransmitter release. The neurotransmitter causes the bipolar cell to hyperpolarize because the neurotransmitter creates IPSPs on the bipolar cell. The bipolar cell does not release NT to the ganglion cell. In the homework, it was indicated that ganglion cells do not fire action potentials unless the bipolar cells released a NT causing them to. However, this was an oversimplification. In fact, ganglion cells fire action potentials, even without stimuli from the bipolar cells. This spontaneous depolarization causes a background action potential generation rate in ganglion cells. Then, when the bipolar cells do fire, they can inhibit the ganglion cells or excite them, changing action potential rate. This will be information sent to the brain that we can then interpret.

Cranial nerves contain (select all that apply): - Parasympathetic pregangionic neurons - Somatic motor neurons - Sensory neurons - Sympathetic neurons

All but sympathetic neurons. Yes! Cranial nerves definitely contain sensory neurons (think of the trigeminal nerve carrying sensations from the face) and somatic motor neurons (think of the facial nerve controlling the muscles of facial expression). They do not contain sympathetic neurons. They do contain preganglionic parasympathetic neurons. Although the autonomic nervous system does have dual innervation (the same targets are reached by the sympathetic and parasympathetic branches), they are reached through different paths.

What kind of medicine would help Rollie the most to alleviate his symptoms? - A Norepinephrine (NE) agonist - An adrenergic antagonist - A nicotinic Ach receptor antagonist

An adrenergic antagonist. Indeed. There are two types of adrenergic receptors on sympathetic targets - alpha and beta. Alpha are on vessels, beta are also found on vessels, but also on the heart. When an antagonist binds, it prevents the normal function of a receptor and the downstream targets. Here, Rollie has too much vessel constriction. He needs to decrease sympathetic activation by inhibiting the action created by NE binding at alpha receptors. Nicotinic Ach receptors are found on all postganglionic autonomic neurons which always elicit EPSPs when Ach binds. Blocking nicotinic receptors would inhibit all autonomic effects. Although blocking all autonomics would inhibit sympathetics, it would also inhibit parasympathetics. This removal of all ANS would not be in anyone's best interests. Agonists would augment the normal effects. So, a NE agonist would make Rollie's problems worse.

When you lift your foot from a painful stimulus and transfer the weight to your opposite limb, where will you observe the IPSPs related to the hamstrings? - anterior gray horn contralateral to the nociceptor - posterior gray horn ipsilateral to the nociceptor - anterior gray horn ipsilateral to the nociceptor - posterior gray horn contralateral to the nociceptor

Anterior gray horn contralateral to the nociceptor. Right! This question asks about the crossed extensor reflex. In this reflex, a nociceptor sends information to the spinal cord. In the spinal cord, the limb from which the pain was detected must be pulled up. You typically do this by bending the knee. To bend the knee, you must activate the hamstrings. So, the ipsilateral hamstrings cannot be inhibited. To bear the weight of the transfer, the opposite limb must be extended (hence the name, crossed extensor). To do this, the contralateral hamstrings must be relaxed as the contralateral quads are activated (extending the knee). To inhibit the hamstrings, an interneuron generates an IPSP on the motor neuron cell body (anterior gray horn of contralateral limb). Check out the reflex lecture notes on this one.

Where is the synapse in a monosynaptic somatic reflex that causes muscle excitation? - Anterior gray horn of spinal cord - Dorsal root ganglion of spinal cord - Lateral gray horn of spinal cord - Posterior gray horn of spinal cord

Anterior gray horn of spinal cord. Right. The stretch reflex is classified as a monosynaptic reflex. Tapping the patellar tendon tests the stretch reflex, a monosynaptic, ipsilateral reflex. When the tendon is tapped, the tendon pulls the muscle quickly - making the muscle long. The typical response is for the tapped muscle to reflexively contract (this would happen if you tap the muscle in the middle of the belly, too). The stimulus is detected by the muscle spindle organ, which includes the terminal end of the sensory neuron; the signal is carried by the sensory neuron towards the spinal cord. In the spinal cord, the sensory neuron synapses directly onto the motor neuron (no interneuron involved). The synapse between the sensory neuron and the motor neuron is in the anterior gray horn.

Consider a stretch reflex of the hamstrings. Where would the sensory neuron synapse with the motor neuron to the hamstrings? - Lateral gray horn of spinal cord - Posterior gray horn of spinal cord - Dorsal root ganglion of spinal cord - Anterior gray horn of spinal cord

Anterior gray horn of spinal cord. Right. This is the monosynaptic portion of the stretch reflex. This response would occur if the hamstrings were suddenly stretched long. In the motor response, the hamstring would be activated to cause contraction and shorten the hamstring length back to the length it was at before. The monosynaptic part is the synapse between the sensory neuron and the motor neuron. To reach the motor neuron, the sensory neuron axon must reach all the way to the motor neuron cell body in the anterior gray horn. Lateral gray horns are for visceral motor neuron cell bodies. Posterior gray horns are for interneurons that receive synapses from somatosensory neurons, which have their cell bodies in the DRG.

If your patient could not detect pain or temperature on their right side, which of the following is most likely damaged in the spinal cord? - anterolateral white matter on the left - anterior gray horn on the right - posterior gray horn on the left - posterior white matter on the right

Anterolateral white matter on the left. Correct! The anterolateral white matter of the spinal cord contains axons of the spinothalamic pathway. The spinothalamic carries pain, temperature and some crude pressure information. It is made of different neurons in series. The first order neuron synapses in the posterior gray horn with the cell body of the second order neuron (gray horn of same side as sensory neuron). From here the second order axon crosses over to make up the spinothalamic (anterolateral) tracts/pathways. Damage to the left spinothalamic tracts would interfere with signal transmission of pain, temperature, crude pressure from the right side of the body. Because ascending information must have intact neurons all the way from the entry into the spinal cord up until the brain, if damage occurs in any part of the white matter portion of the pathway, there will be sensory loss at the level of damage and below. If damage occurs just at the gray matter and does not affect different spinal cord levels, you will have sensory loss at that spinal cord level only. The posterior column pathway includes white matter of the posterior region of your spinal cord. It carries fine touch, conscious proprioception (muscle, joint position), vibration and pressure information from the same side of the body. The first order neuron axons make up the posterior column. Because the posterior column is made of first order neurons, they have not yet crossed the body. Therefore, damage to the left posterior column interrupts signal transmission (of specific information) from the left side of the body. Anterior gray horns are for motor information.

With your big toe, you step on a sharp tack. Given what you know about the resulting motor response, where on the trunk is the exchange between the sensory information and motor information? - At about the level of the C5 vertebra - At about the level of the T10 vertebra - At about the level of the L5 vertebra - At about the level of the 3rd sacral vertebra

At about the level of T10 vertebra. Right! The spinal cord ends in the conus medullaris which occurs about the level of L1/L2 vertebrae. The enlargements associated with the limbs occur in the cervical and lumbar regions of the cord. The lumbar enlargement is just proximal to the conus medullaris - this is where neurons for the limbs emerge or enter the cord. For this particular reflex, the neurons are found in the sciatic nerve, which is made of neurons from spinal segments L4-S3. This will be located at approximately the T10 vertebra.

Using the graph of rods & cones from the Eye activity, at what light intensity must a light be for color to be detected? - at least log 5 uuL of light - at least 7 minutes of duration in the dark - at least log 2 uuL of light - at least 30 minutes of duration in the dark

At least log 5 uuL of light. Right! Cones detect color. However, color light can only activate cones at a high enough light intensity. So, since the cones detect light at log 5 uuL or greater, only light at that intensity can activate cones and be perceived as colorful. Below that light intensity, only the rods are activated and can respond, though they do not indicate color.

After a trauma, you tap your patient's left patellar tendon. Her muscles respond, but she does not feel the tap. Where could the damage be? - Axons in the left lateral white matter in the lumbar region of the cord - Cell bodies in the left posterior gray horn in the lumbar region of the cord - Axons in the left posterior column white matter in the lumbar region of the cord - Cell bodies in the left anterior gray horn in the lumbar region of the cord

Axons in the left posterior column white matter in the lumbar region of the cord. Right! Tapping the patellar tendon tests the stretch reflex, a monosynaptic, ipsilateral reflex. When the tendon is tapped, the tendon pulls the muscle quickly - making the muscle long. The typical response is for the tapped muscle to reflexively contract (this would happen if you tap the muscle in the middle of the belly, too). The stimulus is detected by the muscle spindle organ, which includes the terminal end of the sensory neuron; the signal is carried by the sensory neuron towards the spinal cord. In the spinal cord, the sensory neuron synapses directly onto the motor neuron (no interneuron involved). The synapse between the sensory neuron and the motor neuron is in the anterior gray horn. It is believed the same proprioceptor that has an axon branch to the anterior gray horn for the reflex also has an axon branch that enters into the posterior white matter for the posterior column-medial lemniscus pathway to carry the proprioceptive information to the brain for conscious perception. Since the expected response occurred of the muscle response, there is no issue along the reflex arc portion through the spinal cord. However, since this person did not consciously feel the stimulus, there is damage to the ascending components carrying information to the brain. The posterior column is the conscious sensory pathway to the brain for proprioception and it carries this information in the ipsilateral posterior white matter. There is not a synapse involved along this pathway until the medulla oblongata, so the posterior gray horn of the cord is not involved. The lateral white matter includes axons for descending conscious motor control (not involved in reflexes, all mediated through lower centers) and the spinothalamic pathway (2nd order neurons not involved in the stretch reflex or the posterior column pathway).

Where on the retina do you think you will find the most ganglion cell axons/ mm2? Where on the retina will you find the most ganglion cell cell bodies/ mm2? axons - optic disc cell bodies - fovea axons - 80 degrees lateral to the fovea cell bodies - 80 degrees lateral to the fovea axons - 20 degrees lateral to the fovea cell bodies - 20 degrees lateral to the fovea axons - fovea cell bodies - optic disc

Axons: optic disc Cell Bodies: Fovea Right! Cones have a low ratio between photoreceptor and ganglion cell. Rods have a high ratio (many rods/ganglion cell). Cones are most dense at the fovea - this is where you should have the lowest possible ratio of cone/ganglion cells. All ganglion cell axons exit the eye at the optic disc. They converge to become the optic nerve, drawn up like a pony tail on a person's head. Although rods are more dense away from the fovea, many rods converge to send signals to very few ganglion cells. These ratios explain why color vision is high acuity per area on the retina.

Why does clonidine cause a depression of blood pressure in normal subjects? - Because it directly inhibits binding of Ach on postganglionic nicotinic receptors - Because it directly blocks NE from binding at effectors - Because it inhibits the release of Ach between the preganglionic and postganglionic sympathetic neurons - Because it directly activates the parasympathetic branch

Because if inhibits the release of Ach between the preganglionic and postganglionic sympathetic neurons. Right! Clonidine directly inhibits presynaptic release of catecholamines by the preganglionic neurons to the postganglionic neurons of the sympathetic NS. By doing this, it reduces postganglionic sympathetic NE release (less depolarization of the postganglionic neuron) which in turn lowers stimulation of effectors such as blood vessels or heart. This leads to lower BP.

Where are the ear ossicles? - Between the auricle and the tympanic membrane - Between the vestibule and cochlea - Between the tympanic membrane and the oval window

Between the tympanic membrane and the oval window. Right. Just making sure. The ear ossicles are the stapes, malleus incus (stirrup, hammer anvil). The extend from the tympanic membrane to the oval window in the middle ear. The external ear is between the auricle tympanic membrane (ear drum). The inner ear includes the vestibule, cochlea semicircular canals.

What will happen to body temperature if TRH cannot be made? - There will be no change in body temperature - Body temperature will increase - Body temperature will decrease

Body temperature will decrease. Right! Body temperature is related to body metabolic rate. The higher the metabolic rate, the higher the body temperature. We are endothermic (warm blooded) animals because of our resting high metabolic rates - through our high constant production and usage of ATP, we maintain an elevated, mostly constant body temperature. Our elevated metabolic rate is due to the constant stimulation of body cells by thyroid hormone (see here for those intersted: http://www.ncbi.nlm.nih.gov/pubmed/18279015Links to an external site.). TH release from the thyroid gland is due to stimulation by the anterior pituitary gland hormone TSH (thyroid stimulating hormone). TSH is released from the anterior pituitary under the action of the hypothalamic hormone TRH (thyrotropin releasing hormone). TRH is released from the hypothalamus into the blood of the hypophyseal portal system. It travels a very short distance to the anterior pituitary where it gets out of the blood and stimulates certain cells of the anterior pituitary to release TSH. When TSH is released, it gets into the blood of the hypophyseal portal system and travels to the rest of the body. TSH binds to receptors on the surface of thyroid gland cells and causes TH production and release. Once in the blood, TH binds to receptors within every single body cell and increases cellular metabolic rate. SO, without TRH, there can be no TSH release and then no TH release and then no high, sustained metabolic rate and no high body temperature.

What will happen to body temperature if TSH cannot be made? - Body temperature will increase - There will be no change in body temperature - Body temperature will decrease

Body temperature will decrease. Right! Body temperature is related to body metabolic rate. The higher the metabolic rate, the higher the body temperature. We are endothermic (warm blooded) animals because of our resting high metabolic rates - through our high constant production and usage of ATP, we maintain an elevated, mostly constant body temperature. Our elevated metabolic rate is due to the constant stimulation of body cells by thyroid hormone (see here for those intersted: http://www.ncbi.nlm.nih.gov/pubmed/18279015). TH release from the thyroid gland is due to stimulation by the anterior pituitary gland hormone TSH (thyroid stimulating hormone). TSH is released from the anterior pituitary under the action of the hypothalamic hormone TRH (thyrotropin releasing hormone). TRH is released from the hypothalamus into the blood of the hypophyseal portal system. It travels a very short distance to the anterior pituitary where it gets out of the blood and stimulates certain cells of the anterior pituitary to release TSH. When TSH is released, it gets into the blood of the hypophyseal portal system and travels to the rest of the body. TSH binds to receptors on the surface of thyroid gland cells and causes TH production and release. Once in the blood, TH binds to receptors within every single body cell and increases cellular metabolic rate. SO, without TRH, there can be no TSH release and then no TH release and then no high, sustained metabolic rate and no high body temperature.

After a trauma, you tap your patient's left patellar tendon. Her muscles do not respond, though she felt the tap. Where could the damage be? - Axons in the left posterior column white matter in the lumbar region of the cord - Cell bodies in the left anterior gray horn in the lumbar region of the cord - Axons in the left lateral white matter in the lumbar region of the cord - Cell bodies in the left posterior gray horn in the lumbar region of the cord

Cell bodies in the left anterior gray horn in the lumbar region of the cord. Right! Tapping the patellar tendon tests the stretch reflex, a monosynaptic, ipsilateral reflex. When the tendon is tapped, the tendon pulls the muscle quickly - making the muscle long. The typical response is for the tapped muscle to reflexively contract (this would happen if you tap the muscle in the middle of the belly, too). The stimulus is detected by the muscle spindle organ, which includes the terminal end of the sensory neuron; the signal is carried by the sensory neuron towards the spinal cord. In the spinal cord, the sensory neuron synapses directly onto the motor neuron (no interneuron involved). The synapse between the sensory neuron and the motor neuron is in the anterior gray horn. If there is not the expected response when this tendon is tapped, the source of issue could be anywhere along the reflex arc. Since this person felt the stimulus, but the motor response did not occur, the damage will likely be in the motor component. The anterior gray horn has the cell bodies of the motor neurons. The posterior column is the conscious sensory pathway to the brain for proprioception. The lateral white matter includes axons for descending conscious motor control (not involved in reflexes) and the spinothalamic pathway (2nd order neurons not involved in a monosynaptic pathway).

When light activates a photoreceptor, do ligand gated sodium/calcium channels change from being open to being closed, or vice versa? - Change from being closed (in dark) to open (in light) - Change from being open (in dark) to closed (in light)

Change from being open (in dark) to closed (in light). Right! Activated rhodopsin dissociates into retinal and opsin. This process activates a G protein that leads to conversion of cGMP to GMP. When there is less cGMP, cGMP dissociates from the ligand gated Na+/Ca++ channel, causing it to close. This means that in the dark, that channel was open and the photoreceptor was depolarized. But in the light, with less cGMP, the channel closes and the photoreceptor repolarizes, returning to resting level. Often this is called hyperpolarization in the light.

Where do preganglionic neurons synapse with postganglionic neurons in the parasympathetic nervous system? - Closer to the CNS than the effector organ - Closer to the effector organ than the CNS

Closer to the effector organ than the CNS. Correct! The sympathetic and parasympathetic branches have their own ganglia. For sympathetic ganglia, only sympathetic preganglionic neurons synapse with sympathetic postganglionic neurons. There are a few locations of sympathetic ganglia: the chain ganglia located just to either side of the vertebral column and the collateral ganglia scattered throughout the abdomen. The adrenal medulla is a special modified sympathetic ganglion made of altered post ganglionic neurons. In parasympathetic ganglia, only parasympathetic preganglionic neurons synapse with parasympathetic postganglionic neurons. Parasympathetic ganglia are located in or near the effector organs (long preganglionic axons).

Using the data graph from today, what is the relationship between PD incidence & caffeine? - Consuming less caffeine causes PD - Consuming more caffeine is correlated with PD - Consuming more caffeine causes PD - Consuming less caffeine is correlated with PD

Consuming less caffeine is correlated with PD. Right! People who consume less caffeine have higher rates of PD than those who consume more caffeine - lower counts of PD for high caffeine intake, higher counts of PD for lower caffeine intake. However, you do not know from the data shown how this data were collected. If this were data from a controlled, randomized trial in which you took into account every possible factor (within reason) and only varied the amount of caffeine, then you could suggest a strong causative relationship. However, without that information, you only have an association between the shown factors - associations are also called correlations. Correlation does not equal causation.

Ashlyn Blocker's life will never be like yours: she was born without nociceptors. Now, aged 18 years, she likes to cook ramen noodles in the kitchen. Sometimes, when the spoon falls into the boiling water, she immediately reaches in to retrieve it. However, Ashlyn must remember not to reach into the boiling water to catch her dropped object. The many scars on her hands and arms indicate how difficult it has been for her to learn this lesson. Regarding Ashlyn, what reflexes are most likely affected by her condition? (select all that apply) - crossed-extensor - tendon - stretch - withdrawal

Crossed extensor & Withdrawal Yes. In the passage, Ashlyn is described as not having nociceptors. The reflexes that involve nociceptors are the withdrawal and crossed extensor. The tendon & stretch reflexes would not be affected because they use proprioceptors, which are not affected by Ashlyn's condition.

If the skin over the knee were suddenly offended by a painful stimulus, you would remove your limb from the pain. What reflex would cause this and where on the trunk would the exchange between sensory information and motor information occur? - Crossed extensor reflex, at about the level of the T9 vertebra - Withdrawal reflex, integration at about the level of the 1st sacral vertebra - Withdrawal reflex, integration at about the level of the T4 vertebra - Crossed extensor reflex, integration at about the level of the L5 vertebra

Crossed extensor reflex, at about the level of the T9 vertebra. Right! The spinal cord ends in the conus medullaris which occurs about the level of L1/L2 vertebrae. The enlargements associated with the limbs occur in the cervical and lumbar regions of the cord. The lumbar enlargement is just proximal to the conus medullaris - this is where neurons for the limbs emerge or enter the cord. For this particular reflex, this withdrawal and crossed extensor reflex, the neurons are found in the femoral nerve, which is made of neurons from spinal segments L2-L4. This will be located at approximately the T9 vertebra.

Heads up! Bipolar cells do not have voltage gated Na+ & K+ channels. NOW answer this: When a bipolar cell moves from light to dark, what does the transmembrane potential at its axon look like (in light for first 1/6th of graph shown, then in dark for rest)?

Decrease to flat line. Right! In the dark, the photoreceptor depolarizes and causes neurotransmitter release. The neurotransmitter causes the bipolar cell to hyperpolarize because the neurotransmitter creates IPSPs on the bipolar cell. The bipolar cell does not have voltage gated Na+ or K+ channels, so it cannot have action potentials.

What is the photoreceptor doing in the dark? - hyperpolarizing and not releasing neurotransmitter to the bipolar cell - depolarizing and releasing neurotransmitter to the bipolar cell - resting and not releasing neurotransmitter to the bipolar cell

Depolarizing and releasing neurotransmitter to the bipolar cell. Correct! In the dark, the photoreceptor has open Na/Ca calcium channels. These channels are open because cGMP is bound to them and Na & Ca can diffuse into the photoreceptor, depolarizing it. Because the photoreceptor is depolarizing, it is releasing NT to the next cell (the bipolar cell). In the light, light energy activates Rhodopsin stored in the photoreceptor to change shape (11-cis retinal changes to all-trans retinal which then dissociates from opsin). The freed opsin triggers a chain reaction that causes cGMP to become GMP. [This is done because the free opsin activates a G-protein called transducin that turns on the enzyme phospohdiesterase (PDE). PDE then converts cGMP to GMP.] When there is less cGMP around, the channel closes and Na/Ca cannot diffuse into the photoreceptor. The photoreceptor then returns to resting levels (which sadly, we call hyperpolarization). The shape change of Rhodopsin is called bleaching.

When is your metabolic rate lowest? - During REM sleep - During RAS sleep - While reading a book after a good meal - During NREM (deep) sleep

During NREM (deep) sleep. Correct! During NREM sleep (slow wave), your metabolic rate drops by some 30%, brain activity declines, your heart rate drops, blood pressure drops and respiratory rate decreases. During REM sleep these same processes increase back to awake levels. The RAS is not active during sleep. While resting and digesting is a lower metabolic rate than during exercise, it is still higher than NREM sleep.

What best describes the effector organs of the parasympathetic nervous system? - Effector organs are only the GI tract only - Effector organs are only glands - Effector organs are only the heart - Effector organs include the heart, glands & GI tract

Effector organs include the heart, glands and GI tract. Right! Our homework image shows heart, glands and GI tract all on the right side as effector organs of the autonomic nervous system. The heart, glands & GI tract respond to either parasympathetic or sympathetic neurotransmitters. This is why these organs are said to be dually innervated - by both the sympathetic & parasympathetic branches. In the picture from the homework, sometimes people interpret this image as follows: the sympathetics affect the GI tract; the adrenal gland affects the glands; the parasympathetic affects the heart. In truth, all of these effectors have receptors for either sympathetic or parasympathetic neurotransmitters (most glands anyway). There will be a few exceptions for when the sympathetic division affects certain targets that the parasympathetic does not. These targets (effector organs) served only by sympathetics include sweat glands & most blood vessels.

How does subconscious information reach lower motor neurons (what are the downward pathways that carry this information)? - Corticospinal pathways - Extrapyramidal pathways - Pyramidal pathways - Direct somatic motor pathways

Extrapyramidal Pathways. Correct! Somatic motor control features at minimum an upper motor neuron and a lower motor neuron. The upper motor neuron cell body is in the upper CNS, the axon extends down to the lower motor neuron. The lower motor neuron cell body is in the anterior gray horn (if a spinal nerve). The basal ganglia and cerebellum unconsciously control skeletal muscles in two ways: (1) by communicating with the cerebral cortex and (2) by communicating with brainstem nuclei. From the brainstem nuclei, axons project down through the spinal cord white matter to synapse on the lower motor neuron - it is these axons that make up the extrapyramidal system (also called indirect pathways). The direct pathway is also called the pyramidal system or corticospinal pathway; the upper motor neuron is in the cerebral cortex and the axons project down through the brainstem and spinal cord to the lower motor neuron. When the axons of this system pass through the cerebrum, they are called the internal capsule. When they pass through the midbrain, they are called the cerebral peduncles. When they pass through the medulla oblongata, they are called the pyramids. When they pass through the spinal cord, they are called the anterior or lateral corticospinal pathways.

True or False? The sensory neurons carrying pressure and pH information from the stomach are part of the autonomic nervous system. - True - False

False. Correct. The autonomic nervous system is a division of the PNS, motor branch. Although sensory neurons come from the gut and visceral organs, they are not technically autonomic neurons. They are structurally and functionally no different than the somatic sensory neurons.

True or False? In the autonomic nervous system, when the parasympathetic division is active, all parasympathetic effects are observed and the sympathetic division is completely inactive. - False - True

False. Correct. The sympathetic and parasympathetic divisions are antagonistic - they have opposite effects. But, their activation is not so simple as either being totally on or totally off. It is true that during digestion, the parasympathetic dominates to regulate gut function. Much of the parasympathetic activation at this time is through local, short reflexes in the wall of the gut and longer reflexes to activate the vagus nerves and those components involved in digestion. Additionally, hypothalamic signals will influence the cranial nerves that decrease heart rate and constrict the pupils, but not all parasympathetic effects will be called into action. For example, during the sex act, parasympathetic activation changes blood flow to the genitalia to allow erection. Luckily, this same parasympathetic action does not occur with every meal we eat! Even more importantly, sympathetic activation of the blood vessels is constant. This background level of sympathetic action maintains a constant degree of constriction (tone) in blood vessels that maintains blood pressure. When you need to change blood pressure, you alter the amount of sympathetic activation to increase constriction (raise BP) or dilate (decrease BP). When you are suddenly surprised, massive sympathetic activation occurs, and parasympathetic is dampened, but not totally eliminated. Whatever your answer on this one, I awarded full credit. This concept was not explicitly discussed in lecture, but is interesting to consider and worth noting.

True or False? Postganglionic parasympathetic neurons extend from the chain ganglia to the adrenal medulla. - False - True

False. Correct! The adrenal medulla is the inside of the adrenal gland. It is composed of modified postganglionic sympathetic neurons. When stimulated, the adrenal medulla releases epinephrine and norepinephrine into the blood. Because the adrenal medulla is a modified sympathetic ganglion, it is innervated by sympathetic preganglionic neurons (preganglionic neurons reach it). The preganglionic neurons have their cell bodies in the spinal cord and reach all the way to the adrenal medulla without first synapsing. Although there are a few parasympathetic fibers that go to the adrenal gland, parasympathetic axons do not synapse in the chain ganglia.

True or False. When an agonist binds to a G-protein coupled receptor, second messengers are always made. - False - True

False. Right! There are different kinds of G proteins and some activate enzymes, some inhibit them. It depends on the type of G protein. Check out this

Usually, _________ hormones travel in the blood _________ and bind to intracellular receptors. - Fat soluble; bound to carriers (mostly) - Fat soluble; freely - Water soluble; freely - Water soluble; bound to carriers (mostly)

Fat soluble, bound to carriers (mostly). Well done! Usually, fat soluble hormones (adrenal cortex hormones, sex hormones and thyroxine) must travel in the blood bound to blood transport proteins (blood carriers). The blood is mostly water and being attached to blood transport proteins allows the hormones to dissolve in the blood. The blood transport proteins are not easily removed from the blood by the kidney or liver and fat soluble hormones are slowly released from the carriers so that they may affect their target cells. Therefore, one advantage of blood transport proteins is that they provide a reserve of hormones in the blood. Once these hormones reach their targets, they dissolve through the cell membrane (made mostly of fats) and find their receptors inside the target cell. Water soluble hormones are the opposite - they travel freely in the blood, but must bind to target cell receptors on the surface of the cell membrane.

_________ hormones travel in the blood _________ and bind to intracellular receptors. - Water soluble; freely - Fat soluble; bound to carriers (mostly) - Fat soluble; freely - Water soluble; bound to carriers (mostly)

Fat soluble; bound to carriers (mostly) Well done! Fat soluble hormones (adrenal cortex hormones, sex hormones and thyroxine) must travel in the blood bound to blood transport proteins (blood carriers). The blood is mostly water and being attached to blood transport proteins allows the hormones to dissolve in the blood. The blood transport proteins are not easily removed from the blood by the kidney or liver and fat soluble hormones are slowly released from the carriers so that they may affect their target cells. Therefore, one advantage of blood transport proteins is that they provide a reserve of hormones in the blood. Once these hormones reach their targets, they dissolve through the cell membrane (made mostly of fats) and find their receptors inside the target cell. Water soluble hormones are the opposite - they travel freely in the blood, but must bind to target cell receptors on the surface of the cell membrane.

Innate reflexes are faster than learned responses because innate reflexes involve ____ - EPSPs but not IPSPs like in learned responses - more motor neurons than learned responses - fewer interneurons than learned responses - more heavily myelinated axons than learned responses

Fewer inter neurons than learned responses. Right! Innate reflexes are the neural pathways you have from birth - they are genetically determined. They involve the fewest neurons as possible which create rapid responses to specific stimuli. Innate and learned reflexes utilize IPSPs and EPSPs. Learned responses are called "learned reflexes" because they can occur quickly and in response to a specific stimulus. These seem to happen without your thinking about them. But really, these responses are things we have learned to do after activating our cerebral cortex. They involve far more neurons than those of innate reflexes, more synapses and therefore more time. It is hard to compare myelination between learned and innate reflexes. They both likely use the same degree of myelination in some cases. More or fewer motor neurons does not make sense in this context.

Where do preganglionic neurons synapse with postganglionic neurons in the parasympathetic nervous system? - Sympathetic chain ganglia - Adrenal medulla - Ganglia located in or near effector organs - Collateral ganglia

Ganglia located in or near effector organs. Correct! The sympathetic and parasympathetic branches have their own ganglia. For sympathetic ganglia, only sympathetic preganglionic neurons synapse with sympathetic postganglionic neurons. There are a few locations of sympathetic ganglia: the chain ganglia located just to either side of the vertebral column and the collateral ganglia scattered throughout the abdomen. The adrenal medulla is a special modified sympathetic ganglion made of altered post ganglionic neurons. In parasympathetic ganglia, only parasympathetic preganglionic neurons synapse with parasympathetic postganglionic neurons. Parasympathetic ganglia are located in or near the effector organs (long preganglionic axons).

Using the eye homework: What cells carry visual information to the brain? - Photoreceptors - Ganglion cells - Bipolar cells - Horizontal cells

Ganglion cells. Correct! The axons of the ganglion cells make up the optic nerves. While the photoreceptors, bipolar cells and horizontal cells are components of the retina (neural layer in particular), it is the axons of ganglion cells that actually carry the signal to the brain.

What cells make up the optic nerve? - Photoreceptors - Ganglion cells - Bipolar cells - Horizontal cells

Mr. and Dr. Q have been married for 17 years. Since his head injury 4 months ago, Dr. Q has noticed that Mr. Q has been having a hard time remembering the people with whom he works. He remembers well the new neighbors that moved in next door 3 months ago, but he cannot remember the name of his current supervisor at work (Ms. P has been his supervisor for 3 years). Again and again Dr. Q reminds him that Ms. P is his supervisor at work, but Mr. Q draws a blank. Which of the following best explains what is happening to Mr. Q? - He has decreased function of his hippocampus - He has decreased synaptic connections between neurons in his insula - He has decreased function of his RAS - He has decreased ability to make short term memories

He has decreased function of his hippocampus. Right! The hippocampus is essential to consolidation of short term memories into long term memories as well as accessing long term memories. Short term memories last less than 1 minute, long term memories can last forever. In this case, Mr. Q. should be accessing long term memories of his supervisor at work. He has worked with this person for 3 years and often sees them. The condition in which one cannot access old memories is called retrograde amnesia. RA can occur without anterograde amnesia (as in this case) or it can co-occur, depending on severity. His RAS is working if he is alert. His short term memory ability is normal if he can have conversations that are meaningful. His insula is functioning correctly if he can consciously perceive food and body position (the insula is the cerebral lobe responsible for this in part) - if he is having trouble with recognizing faces in general (meaning, does not even see a person), the inferior temporal lobes are in trouble. Of course it is also possible Mr. Q is an engineer and bad with names :).

Mr. and Mrs. A have been married for 40 years. Recently, Mrs. A has noticed that Mr. A has been having a hard time remembering the new people he has been meeting. He remembers well the neighbors that have lived next door for the last 20 years, but he keeps asking about the new couple that moved in next door 3 months ago. Again and again his wife reminds him that he has met them several times, but he insists that he has not. What do you think is happening to Mr. A? - He has decreased ability to make short term memories - He has decreased function of his hippocampus - He has decreased synaptic connections between neurons in his occipital lobe - He has decreased function of his RAS

He has decreased function of his hippocampus. Right! The hippocampus is essential to consolidation of short term memories into long term memories. Short term memories last less than 1 minute, long term memories can last forever or only as long as a course in A&P :0. in this case, Mr. A. should be making long term memories of his new neighbors. He has met them several times and often sees them outside. The condition in which one cannot make new memories is called anterograde amnesia. His RAS is working if he is alert. His short term memory ability is normal if he can have conversations that are meaningful. His occipital lobe is functioning correctly if he can see and recall the function or name of simple objects - remember the inferior temporal lobes are for facial recognition.

Why is Rollie pale? - he has less blood flowing to his face - he has less total blood volume - he has a higher heart rate

He has less blood flowing to his face. Right! When vessels constrict, less blood flows from the constricted end into a tissue. This means that if the vessels of the face constrict, the face gets less blood and the skin appears pale. This is consistent with Rollie's symptoms because of his very high sympathetic activation.

Which of the following are important to emotion? - medulla oblongata & pons - spinocerebellar pathway & pyramidal pathway - hippocampus & amygdala

Hippocampus & amygdala. Correct! The hippocampus and amygdala are regions of the limbic system (other regions of the brain contribute as well). They are important to emotion as well as learning and memory. The medulla oblongata & pons are part of the brainstem and therefore important to vegetative functions. The spinocerebellar & pyramidal pathways are ascending (spinocerebellar) and descending (pyramidal) pathways important for unconscious position information transfer to the cerebellum (spinocerebellar) and motor control (pyramids).

Which of the following is essential to consolidation of fact (declarative) memories? - spinocerebellar pathway - medulla oblongata - hippocampus

Hippocampus. Correct! Consolidation refers to the conversion of short term memories to long term memories. The hippocampus is essential to the this function. During long term memory formation, hippocampal neurons facilitate neural pathways leading to rapid transmission of signals along specific neural traces. A memory is a stimulus that triggers signal transmission along this specific neural path. When the hippocampus is removed, individuals cannot form new long term memories (a condition called anterograde amnesia). This condition was dramatically illustrated in the film 50 First Dates starring the actors Drew Barrymore Adam Sandler.

Which of the following are the most important components of an acute stress reaction? - Hypothalamus, anterior pituitary and adrenal cortex - Posterior pituitary & hypothalamus - Pancreas & parathyroid glands - Hypothalamus & adrenal medullae

Hypothalamus and adrenal medullae. Perfect! The acute stress response is how the body reacts to a sudden stress. Stress includes any emotional or physical stimulus that evokes the stress response. The body responds to acute stresses using the sympathetic nervous system - including its components the hypothalamus and adrenal medullae. Longer term stresses - ones that last beyond a few minutes - evoke the responses of the adrenal cortex and the hypothalamus and anterior pituitary that regulate it. The hypothalamus and posterior pituitary make and release, respectively, other hormones (ADH & oxytocin), that are not components of acute stress responses. ADH may be released during chronic stresses to augment the effects of aldosterone.

ADH is produced in the _______________ and released to the blood from the _____________. - hypothalamus; posterior pituitary - posterior pituitary; posterior pituitary - anterior pituitary; posterior pituitary - posterior pituitary; anterior pituitary

Hypothalamus, posterior pituitary. Sehr gut! Anitdiuretic hormone (ADH) is essential to your normal blood osmolarity (salt/water balance). It is made by neurons in the hypothalamus. These neurons have their cell bodies in the hypothalamus but their axons extend down to the posterior pituitary. Because all of the cellular machinery responsible for ADH production is located in the cell bodies, ADH is made in the hypothalamus. However, because the terminal end that releases the ADH to the blood is located in the posterior pituitary, the hormone is actually released from the post. pituitary.

Which part of the endocrine system is most appropriately called the "master gland"? - posterior pituitary - thyroid - hypothalamus - anterior pituitary

Hypothalamus. While the anterior and posterior pituitary release hormones necessary for homeostasis, they only do under the direction of the hypothalamus. The thyroid gland releases a hormone that has widespread effects on virtually every cell in the body, but again, its activity is regulated by a hormone from the ant. pit, who is regulated by the hypothalamus. The best answer here is the hypothalamus.

If you created a drug to prevent PD, where would you want to prevent neuronal death? - In the cerebellum - In the basal ganglia - In the midbrain (substantia nigra) - In the post central gyrus

In the midbrain (substantia niagra). Right! PD (Parkinson's disease) is due to degeneration of the substantia nigra in the midbrain. When these neurons die, they no longer regulate the basal ganglia. Death of the basal ganglia occur in Huntington's disease Cerebellar damage/death causes the condition ataxia Loss of cells in the post central gyrus will result in sensory loss

In the case study about a person who dove into shallow water...Where are the axons that carry motor information to the left trunk muscles? - In the right lateral white matter of the spinal cord - In the left lateral white matter of the spinal cord - In the right anterior white matter of the spinal cord - In the left anterior white matter of the spinal cord

In the right anterior white matter of the spinal cord.

In the case study about a person who dove into shallow water...Where are the axons that carry temperature information from the left upper/lower extremities? - In the right posterior white matter of the spinal cord - In the left posterior white matter of the spinal cord - In the right anterolateral white matter of the spinal cord - In the left anterolateral white matter of the spinal cord

In the right anterolateral white matter of the spinal cord.

In the case study about a person who dove into shallow water...Where are the axons that carry motor information to the right upper/lower extremities? - In the right lateral white matter of the spinal cord - In the left lateral white matter of the spinal cord - In the right anterior white matter of the spinal cord - In the left anterior white matter of the spinal cord

In the right lateral white matter of the spinal cord.

In the case study about a person who dove into shallow water...Where are the axons that carry touch, pressure, and vibration information from the right upper/lower extremities? - In the right posterior white matter of the spinal cord - In the left posterior white matter of the spinal cord - In the right anterolateral white matter of the spinal cord - In the left anterolateral white matter of the spinal cord

In the right posterior white matter of the spinal cord.

In babies, where is the site of integration for the stepping reflex? - in the brainstem - in the spinal cord - in the cerebrum - in the cerebellum

In the spinal cord. Correct! This is a spinal nerve reflex, not a cranial nerve reflex. For spinal nerve reflexes, the sensory neuron and motor neuron interact in the spinal cord. For cranial nerves, the neurons interact in the brainstem. The cerebrum and cerebellum are never integration centers for reflexes. The whole point of reflexes is that you can do them without higher brain contributions.

Heads up! Photoreceptors cells do not have voltage gated Na+ & K+ channels. NOW answer this: When a photoreceptor moves from light to dark, what does the transmembrane potential at a region between the cell body and terminal end look like? (in light for first 1/6th of graph shown, then in dark for rest)

Increase to flat line. Right! In the dark, the photoreceptor depolarizes and causes neurotransmitter release. This happens even though no action potentials happen. The neurotransmitter release is due to a graded potential being big enough to open the voltage gated calcium channels. The photoreceptor does not have voltage gated Na+ or K+ channels, so it cannot have action potentials.

How does caffeine interact with CNS neurons? - It binds to adenosine receptors and inactivates them - It is an agonist of ATP - It binds to dopamine receptors and activates them - It binds to GABA receptors and inactivates them

It binds to adenosine receptors and inactivates them. Right! Caffeine is a competitive antagonist for adenosine receptors. When it binds, it prevents adenosine from binding and inactivates the effects of adenosine. In doing so, glutamate and dopamine effects persist in the CNS, causing you to be more awake (because if adenosine bound, dopamine and glutamate levels would fall due to adenosine inhibiting the neurons that release them), although it does not bind to the receptors for glutamate or dopamine. It is interesting to consider that in the brain, perhaps neurons are continually active. By having adenosine (or another neurotransmitter or hormone) bind, this baseline activity can be changed.

Which of the following is unusual about thyroid hormone? - It binds to an intracellular receptor, does not require a blood transport protein but cannot enter the cell without a membrane transport protein - It binds to a membrane receptor, does not require a blood transport protein but can enter the cell passively - It binds to an intracellular receptor, requires a blood transport protein but cannot enter the cell without a membrane transport protein - It binds to a membrane receptor, requires a blood transport protein but can enter the cell passively

It binds to an intracellular receptor, requires a blood transport protein but cannot enter the cell without a membrane transport protein. Right! Thyroid hormone utilizes an intracellular receptor, requires a blood transport protein (thyroid binding globulin, made by liver) but cannot enter the cell alone. It must use a membrane transporter. For more information about this check out here: http://www.ncbi.nlm.nih.gov/pubmed/17574004Links to an external site. - this feature appears particularly important when thinking about entry into the brain or across the placenta for the developing baby. What is strange is that normally hormones that bind to intracellular receptors are fat soluble and do not require assistance into the cell, though they require blood transport proteins for even distribution in the blood. Thyroid hormone is strange in that it binds intracellularly and uses the transport, but not the solubility in the membrane.

What happens to Rhodopsin in the light? - It causes the photoreceptor to depolarize - It changes shape and breaks apart - It is released to the bipolar cell, causing an IPSP

It changes shape and breaks apart. Correct! In the dark, Rhodopsin is whole and made of 11-cis retinal attached to opsin. Rhodopsin is in the outer segment of the photoreceptor. In the light, light energy activates Rhodopsin to change shape (11-cis retinal changes to all-trans retinal which then dissociates from opsin). The freed opsin triggers a chain reaction that causes cGMP to become GMP. [This is done because the free opsin activates a G-protein called transducin that turns on the enzyme phospohdiesterase (PDE). PDE then converts cGMP to GMP.] The shape change of Rhodopsin is called bleaching.

What do you notice about the sensory pathway shown? - It does not show neurons that synapse in the thalamus before information reaches the primary olfactory cortex - It does show neurons that synapse in the thalamus before information reaches the primary olfactory cortex

It does not show neurons that synapse in the thalamus before information reaches the primary olfactory cortex. Right! Unlike other sensory pathways, olfactory information does not synapse in the thalamus before signals are sent to the olfactory cortex. This is likely because the olfactory pathway is a very ancient pathway and it develops in a manner differently than most other sensory receptors.

Methylphenidate is sold as the medication Ritalin. It has been shown to improve memory and learning in individuals who consume this medication because it increases excitatory signal transmission in certain neural pathways. Which of the following would explain how it acts (its mechanism of action)? - It acts as an antagonist to EPSP causing neurotransmitters - It acts as an inverse agonist for EPSP causing neurotransmitters - It acts an agonist for IPSP causing neurotransmitters - It prevents re-uptake of EPSP causing neurotransmitter

It prevents re-uptake of EPSP causing neurotransmitter. Right! The prompt suggests that we want to increase the number of EPSPs (or intensity of them) in certain neural pathways. There are two ways to do this: 1) prevent removal of the EPSP causing NT or 2) add an agonist that acts like the EPSP causing NT. Re-uptake is the process by which a presynaptic neuron reabsorbs the NT it released. If we inhibit this re-uptake, we can increase the amount of NT in the cleft and sustain signal transmission in the pathway. Agonists bind to a receptor and cause the same effect as when a NT usually binds to that receptor on that cell. Inverse agonists bind to receptor and cause the opposite effect as when a NT usually binds to that receptor on that cell. So, if the normal response of a certain cell to Ach is opening of Na+ channels --> depolarization, then when the inverse agonist binds to the Ach receptor, the cell hyperpolarizes (perhaps by opening a Cl- channel or K+ channel). Antagonists bind to a receptor for a certain NT and block the receptor - the antagonist itself does not change the activity of the cell, but instead prevents an NT from changing the activity of the cell. Agonists, antagonists and inverse agonists are receptor specific.

Regarding caffeine and PD, is increasing caffeine intake a good treatment therapy? - Maybe, but only for the short term treatment of symptoms if some brainstem cells are present - No, it would not have an impact on symptoms in the early stages - Maybe, but only for the long term treatment of symptoms once all brainstem cells are gone

Maybe, but only for the short term treatment of symptoms if some brainstem cells are present. Right! Maybe. Caffeine binds to adenosine receptors in the substantia nigra preventing the inhibitor effect of adenosine on dopamine releasing cells. Increasing caffeine should therefore not further decrease dopamine presence in the short term - as long as the cells that release it are still viable. The problem with PD is the constant degeneration of the substantia nigra cells. Without these to bind caffeine, caffeine would not be an effective medication. Additionally, caffeine would probably not be a long term treatment option since some people might develop tolerance. However, it may temporarily serve as a protective mechanism to some extent.

What other symptoms would you NOT expect in Rollie? - Dilated pupil in eyes - Constipation in GI tract - More storage of glucose in liver - Bronchodilaton in lungs

More storage of glucose in liver. Correct! With elevated sympathetics, you usually get depressed parasympathetics. 3 of these options would be consistent with high sympathetics (elevated blood sugar due to the liver releasing more glucose from storage, bronchodilation to increase airflow, dilated pupils to see the field of view). However, depressed gut function would lead to less defecation = constipation.

Consider two neurons in series (neuron #1 synapses on #2). When activated, neuron #1 releases NT onto neuron #2 that results in IPSPs on neuron #2. What happens if some ligand promotes depolarization on neuron #1 to threshold? - Neuron #2 hyperpolarizes - Neuron #2 depolarizes - Nothing

Neuron #2 hyperpolarizes.

OK. So for now. Imagine the above scenario again. What happens if an antagonist for the ligand above appears? - Neuron #2 hyperpolarizes - Neuron #2 depolarizes - Nothing - neuron #2 neither hyperpolarizes nor depolarizes

Nothing - neuron #2 neither hyperpolarizes nor depolarizes. Awesome. Let's talk about caffeine in class. So, if the ligand causes neuron #2 to hyperpolarize, then when the antagonist is present, it blocks the ligand on #1. This means that #1 won't release NT to #2 and #2 won't hyperpolarize. At least not if there are no other neurons present....

Which sensory apparatus uses the actual cranial nerve as the receptor cells? - Hearing - Olfactory - Equilibrium - Optic - Gustatory

Olfactory. Right! The olfactory receptors cells are actually CN I. In the eye, the photoreceptors are the sensory receptors - they indirectly communicate with the ganglion cells which then make up the optic nerve (CN II). Hair cells are the sensory receptors for equilibrium and hearing - they then communicate with the vestibulocochlear nerve (CN VIII). The gustatory receptor cells relay signals to the facial (VII), vagus (X) glossopharyngeal (IX) nerves.

What is the name of the pathways that carry visual information from the thalamus to the occipital lobes? - Optic radiation - Superior colliculi - Optic chiasm - Optic nerves (CN II)

Optic radiation. Right! The optic radiations are the paired pathways of axons from the left and right thalamus to the ipsilateral occipital lobe. Each retina has a visual field, some of which is shared with the other eye. When visual information is received by the retina, the information on the nasal half of each retina is carried by the optic nerves through the optic chiasm to the contralateral thalamus. The information on the lateral half of each retina does not pass through the optic chiasm and instead is sent to the ipsilateral thalamus. This partial crossover of information is called a hemidecussation because half of the information crosses over to the other side while the other half does not (hemi=half, decussation=crossing). The end result is that each thalamus receives visual data from the opposite visual field, some of it from the ipsilateral eye and some of it from the contralateral eye. This information is then sent to the primary visual cortex (in the occipital lobe) for processing via the optic radiations. If the optic radiations are not working, it is the same as if the occipital lobe is not functioning. The superior colliculi are reflex centers in the midbrain that coordinate visual data with eye movements so that you can read words on a page or turn towards something at the periphery of your visual field.

What is the name of the pathways that carry visual information from the thalamus to the occipital lobes? - Superior colliculi - Optic chiasm - Optic nerves (CN II) - Optic radiation

What division of the autonomic nervous system uses Norepinephrine or Epinephrine at the effector organs? - Both Sympathetic & Parasympathetic - Sympathetic - Parasympathetic

Parasympathetic.

Which of the following explains why someone would have a high tolerance to caffeine? (People with high tolerance require more caffeine for a response than someone else for the same response.) - People with high tolerance have fewer competitive antagonists for caffeine receptors than people with low tolerance - People with high tolerance bind caffeine at their receptors for more time than people with low tolerance - People with high tolerance have more receptors for caffeine than people with low tolerance - People with high tolerance remove caffeine from their body slower than people with low tolerance

People with high tolerance have more receptors for caffeine than people with low tolerance. Right! Tolerance is related to the readiness of the body to respond to the compound. Since molecular interactions are really just random events, the more likely you make it for molecules to engage with their receptors, the more likely you are to have a response. But, you also need to consider if the compound is an agonist or an antagonist. If you can remove caffeine from the body very quickly due to liver processing of the compound, you will likely have a high tolerance - you can consume the compound but the chances it will hit a receptor rapidly diminish as you process it. If you have a lot of receptors for the compound, the chance some of the compound will come in contact with the receptor becomes higher. But, this would mean for an agonist, you have a low tolerance - a little bit of the drug will hit the receptor and have an effect on the target cell to change cellular function. For an antagonist, this is the opposite in terms of receptor number. Caffeine itself is an antagonist to adenosine. It competes for the same binding site as adenosine and when caffeine binds, adenosine cannot do its job (make you sleepy for example). If you have more receptors for adenosine, then some will bind caffeine (blocking adenosine), but others will bind adenosine and cause an effect on the cell. So, for antagonist compounds, you have a higher tolerance if you have more receptors because they need to outcompete the adenosine. And the more receptors you have, the more caffeine you will need to beat them. If you bind the compound for a very long time, you will have more of a reaction with the same amount of compound as someone who binds it more strongly - low tolerance.

Using the eye homework: What happens first when dim light enters the eye? - Photopigments in the rods bleach - Photopigments in the cones bleach - Rhodopsin regenerates

Photopigments in the rods bleach. Correct! Bright light is detected by cones, dim light is detected by rods. Although rods will respond to bright light initially, they gradually shut off. Photopigments (visual pigments) are proteins that change shape when they absorb photons of light. This shape change is called bleaching. Once a photopigment has been bleached, it must be regenerated before another light molecule can activate it. The most well studied photopigment is rhodopsin - it is found in the outer segments of rods. It is composed of a bent retinal molecule attached to a protein opsin molecule. In the dark, the bent retinal is attached to opsin and we call the resulting compound rhodopsin. When light enters the eye, the retinal absorbs the energy of the light and becomes straight instead of bent. The straight retinal cannot stay attached to opsin and so the rhodopsin degenerates into a free retinal and free opsin (bleaching). Now that the opsin is free, it starts a chain reaction in the photoreceptor that changes ion permeability of the rod. This series of reactions ultimately signals the bipolar cell. The bipolar cell then signals the ganglion cell. The ganglion cell then sends action potentials to the brain. Rhodopsin regeneration must occur before another photon of light can be detected by the pigment. This process involves enzymes and ATP in the pigmented layer of the retina.

For successful regeneration of the visual pigment, the photoreceptors must be in direct contact with the ________. - Ciliary body - Choroid - Pigmented layer of the retina - Ganglion cells

Pigmented layer of the retina. Right! The pigmented layer of the retina is a single cell thickness epithelium between the photoreceptors and the choroid. Its cells contain the enzymes that make possible visual pigment regeneration. Without the direct contact between the photoreceptors and the pigmented epithelium, visual pigment cannot be regenerated and the photoreceptors cannot respond to new light. The rest of these structures have specific functions addressed in the feedback of the other questions.

What type of receptor is shown here? - Osmoreceptor - Baroreceptor - Proprioceptor - Nociceptor

Propioreceptor. Right! Proprioceptors are a type of mechanoreceptor that is located in a muscle, joint, tendon or ligament. They send signals to the CNS when the shape of the muscle, tendon, joint or ligament changes. The tendon & stretch reflexes use proprioceptors. The image here shows the stretch reflex, in which the special proprioceptor (a muscle spindle) is located in the muscle itself. When the muscle spindle is stretched, it initiates the stretch reflex, causing the same muscle that contains the muscle spindle to contract. Nociceptors are pain receptors. The withdrawal and crossed extensor involve nociceptors. Baroreceptors are a special type of mechanoreceptor that monitors pressure in hollow organs - you will find them in blood vessels, digestive organs (stomach, intestines) & respiratory organs (like lungs). Osmoreceptors are also mechanoreceptors that detect changes in solution salt/water balance (osmolarity). They are particularly important in detecting the concentration of the blood by special regions in the brain containing osmoreceptors.

Which of the following keeps you awake in class? - RAS - hippocampus - hypothalamus - nociceptors

RAS. Correct! While sitting in class may be painful (activation of nociceptors), it is the reticular activating system (RAS) that wakes up the cerebral cortex and maintains arousal. When the RAS is not active, you are unconscious. The RAS is a network of nuclei associated with the reticular formation of the brain stem. The reticular formation is a collection of nuclei and fiber tracts that receives information from sensory receptors (not smell) and sends them to the headquarters of the RAS located in the midbrain. From there, neural activity excites the cerebral cortex. The RAS is active during your waking periods and is inactive during sleep. When you wake up in the middle of the night, the RAS has been activated for some reason.

In the case study about a person who dove into shallow water...Where is the damage to the this person (you must select only 1 place) - right cerebral hemisphere - left cerebral hemisphere - right spinal cord - left spinal cord

Right spinal cord

Which of the following does NOT cause the release of a hormone from an endocrine organ? - Neural reflex arc - Another hormone - Somatic motor neuron stimulation - Levels of circulating ions

Somatic motor neuron stimulation. Correcto! Hormones are released due to the actions of arriving hormones, circulating levels of blood ions/chemical (sodium, potassium, calcium or glucose) or due to neural stimuli. However, that neural stimuli does not come from a somatic motor neurons because somatic motor neurons innervate skeletal muscle. Only visceral motor neurons directly stimulate glands (composed of epithelial tissue) or if the endocrine organ is a neural structure (like the hypothalamus), then an interneuron can stimulate the hormone's production and release.

Which of the following does NOT cause the release of a hormone from an endocrine organ? - Another hormone - Somatic motor neuron stimulation - Levels of circulating ions - Neural reflex arc

Which of the following is/are an innate reflex that involves a proprioceptor? (select all that apply) - Stretch reflex - Withdraw reflex - Any visceral reflex - Tendon reflex

Stretch & Tendon Reflexes. Correct! Some reflexes are important to posture and regulating muscle activation. These reflexes use proprioceptors as the sensory neuron (muscle spindles for the stretch reflex and gogli tendon organs for the tendon reflex). Visceral reflexes regulate non-skeletal muscle activity, like heart rate, digestive activity, etc. and involve chemoreceptors or stretch receptors typically. Nociceptors are pain receptors - like when you touch a hot stove, the nociceptor is activated. In the spinal cord, this sensory neuron sends information to an interneuron which then communicates with the somatic motor neurons that withdraw your hand from the painful stimulus.

In which reflex does the activated muscle also contain the proprioceptors responsible for initiating the reflex? - tendon - stretch - withdrawal - crossed-extensor

Stretch reflex. Right! The stretch reflex is initiated by a proprioceptor embedded in the muscle belly. When the muscle spindle is lengthened, the sensory neuron of the muscle spindle sends an action potential towards the spinal cord. In the spinal cord, the sensory neuron synapses with the motor neuron to the same muscle, causing the muscle to be activated. For the tendon reflex, the receptor is in the tendon and the organ that contains the receptor is ultimately inhibited. For the crossed-extensor and withdrawal reflexes, a nociceptor is utilized, not a proprioceptor.

What controls the diameter of the pupil? - Somatic motor innervation - Sympathetic and parasympathetic innervation from the oculomotor nerve - Sympathetic innervation from special sympathetic nerves to the eye and parasympathetic innervation from the oculomotor nerve - Sympathetic and parasympathetic innervation from special sympathetic nerves to the eye

Sympathetic innervation from special sympathetic nerves to the eye and parasympathetic innervation from the oculomotor nerve. Correct! The iris is a structure that contains smooth muscles in circular and radial (longitudinal) arrangements. The muscle fibers are oriented so that when the circular constrictor muscles are active, they decrease the pupil diameter. The constrictor muscles are controlled by parasympathetic axons that arrive at the eye via the oculomotor nerve. When the radial fibers are active, they increase pupil diameter. The radial muscles are controlled by sympathetic axons that arrive from the chain ganglion in special sympathetic nerves to eye. While the eye is served by both autonomic branches, the autonomic axons reach the target through different pathways. Somatic axons do not control smooth muscle.

Suppose I hand you a section of the spinal cord (I carry them in my pockets). I tell you it is from the T4 segment. What neuron cell bodies would be located in the lateral gray horns? - Parasympathetic postganglionic cell bodies - Sympathetic postganglionic cell bodies - Sympathetic preganglionic cell bodies - Parasympathetic preganglionic cell bodies

Sympathetic preganglionic cell bodies. Correct! The cell bodies of all autonomic preganglionic neurons are located in the CNS. (Postganglionic cell bodies are in the autonomic ganglia out somewhere in the body.) The sympathetic preganglionic neurons only emerge from T1-L2/3 levels of the spinal cord; this is why the sympathetic branch is called the thoracolumbar division. Parasympathetic preganglionic cell bodies will be found only in the brain stem or in S2-S4 of the spinal cord.

Which division of the autonomic nervous system has relatively short preganglionic neurons and relatively long postganglionic neurons? - Parasympathetic - Both - they are equally short for the pre or long for the post - Sympathetic

Sympathetic.

Which of the following is an ipsilateral polysynaptic spinal somatic reflex that inhibits muscle activity to regulate muscle tension protectively? - Crossed extensor reflex - Tendon reflex - Stretch reflex - Any visceral reflex

Tendon reflex. Correct! Spinal reflexes feature the spinal cord as the integration (processing) center of the reflex arc. Cranial reflexes use the brainstem as the processing center. Somatic refers to skeletal muscle and not visceral (gut, heart) muscle. Reflexes can be learned (like riding a bike) or innate (crossed extensor, stretch etc). Ipsilateral means that the neural connections are all occurring on the same side of the body, contralateral means they involve neurons on both sides of the body. Polysynaptic reflexes involve more than just the sensory and motor neurons (they also involve interneurons) and feature more than one synapse in the reflex arc. The tendon reflex involves an interneuron in the spinal cord, neurons all on the same side of the body and skeletal muscles.

Which of the following is an ipsilateral polysynaptic spinal somatic reflex that regulates muscle tension protectively? - Any visceral reflex - Tendon reflex - Stretch reflex - Crossed extensor reflex

Which is true of both the olfactory and gustatory receptors? - Only gustatory receptors contribute to taste perception. - They both require the chemical that stimulates them to be dissolved in water/mucous. - They are never replaced. - They are both proprioceptors.

They both require the chemical that stimulates them to be dissolved in water/mucous. Correct! The olfactory and gustatory receptors are chemoreceptors. They bind chemicals that lead to depolarizations and ultimately, action potentials that are sent to the brain for perception. They both require that their stimuli are dissolved in mucous (or fluid) to be detected. They also are both capable of regeneration - within about 1-2 weeks you have replaced all your taste buds and within 1-2 months you have replaced all your olfactory receptors. Both olfactory and gustatory receptors contribute to the sensations of taste. It is estimated that about 70-80% of taste is smell because both receptors relay information to the same regions in the brain.

Using the eye homework: When light activates a photoreceptor, what happens to ligand gated sodium/calcium channels? - They change from open to closed - The change from closed to open

They change from open to closed. Right! Activated rhodopsin dissociates into retinal and opsin. This process activates a G protein that leads to conversion of cGMP to GMP. When there is less cGMP, cGMP dissociates from the ligand gated Na+/Ca++ channel, causing it to close. This means that in the dark, that channel was open and the photoreceptor was depolarized. But in the light, with less cGMP, the channel closes and the photoreceptor repolarizes, returning to resting level. Often this is called hyperpolarization in the light.

When cells receive chemical messengers (ligands) on their surface, a whole host of events take place inside the cell. The ultimate goal is a response by the cell. By using G Protein Coupled Receptors (GPCRs), second messengers such as cyclic AMP (cAMP) can be made. Above, see the effect of cAMP in liver cells. According to the image, when the ligand binds, what happens to second messenger levels? - They increase - They decrease - They do not change

They increase. Right. According to the image shown, when the ligand binds, cAMP levels increase. This is because when the ligand binds, the G protein is activated which then moves along the membrane, causing the membrane bound enzyme adenylyl cyclase to make cAMP from ATP. cAMP is the second messenger because it goes on to the do the signaling inside the cell; the ligand was the first messenger. Adenylyl cyclase is the effector enzyme. Sometimes, inside cells, when ligands bind, they cause a different G protein to be activated which then inhibits adenyly cyclase. In this case, cAMP levels decline.

The smooth muscles of the deepest pelvic organs (ie urinary bladder) are controlled by autonomic neurons. How do parasympathetic axons reach these targets? - Through neurons that emerge from the lumbar segments of the spinal cord - Through neurons that emerge from the thoracic segments of the spinal cord - Through neurons that emerge from the sacral segments of the spinal cord - Through neurons that emerge from the brainstem

Through neurons that emerge from the sacral segments of the spinal cord. Correct! The parasympathetic division of the autonomic nervous system has preganglionic cells that are located in the brainstem and the sacral segments of the spinal cord. For this reason, it is called the craniosacral division. The sympathetic branch has preganglionic cells that leave the spinal cord between T1-L2/3 segments of the spinal cord - thus it is called the thoracolumbar division. The deepest pelvic organs receive parasympathetic information that originates from the sacral regions. The same organs receive sympathetic information from lumbar or thoracic regions.

99% of the cases of hypercalcemia (too high blood calcium) are due to tumors of the parathyroid glands. Is the problem too much PTH or too little PTH? - Too little PTH - Too much PTH - Not related to PTH

Too much PTH. Right! PTH is produced by the parathyroid glands - it activates osteoclasts to break down bone and increase blood calcium levels. When there is too much PTH the bones become brittle and the blood calcium spikes.

True or False? In the autonomic nervous system, for both the sympathetic and parasympathetic divisoins, the preganglionic neuron releases Ach to the postganglionic neuron - True - False

True.

True or False? Some olfactory and gustatory stimuli (odorants/tastants) trigger action potentials in low concentrations, while other odorants/tastants trigger action potentials only in high concentrations. - False - True

True. You inherently know this - think of a very bad odor, like rotting food or cigarette smoke. You can detect these odors although very little of them many be present. It is similar for the chemical they put in natural gas that is piped into your home. These odorants trigger the olfactory receptors to generate action potentials when just a few molecules are present (although with natural gas, 1 in 1000 people cannot detect that odor). Sometimes we can adapt to these noxious fumes - like smokers who gradually destroy their olfactory receptors with the toxins in cigarette smoke (not true adaptation, but the same effect), or decreased production of the receptors on the receptor cells for that odorant/tastant or our brain activates GABA secreting neurons in the olfactory pathway to inhibit signal transmission - but for others, we cannot adapt. Other odorants/tastants require more of the molecules to be present to initiate an effect in the receptor cells. Because these modalities are mediated by a chemically gated channel, you can think of the odorant/tastant like we think of neurotransmitters on a postsynaptic cell. Bigger graded potentials are generated when there are more receptors for the neurotransmitter or the neurotransmitter is present for longer. Odorants/tastants that bind for long periods or find more receptors can have a big effect despite have few molecules present. The other factors that affect an odorant's ability to trigger awareness is the odorant's ability to dissolve in your nasal mucosa and find the olfactory receptor cells. If you have a very dry nose or an overly mucous filled nose (stuff nose), odorants cannot reach the receptors.

True or False? All the hormones from the anterior pituitary are regulated by some hormone from the hypothalamus. (Though not the same hypothalamic hormone for all ant pit hormones.) - True - False

True. Right! All the hormones from the anterior pituitary are regulated by hormones from the hypothalamus - the hypothalamic hormones reach the anterior pituitary via the hypophyseal portal system, a special blood network between the hypothalamus and the anterior pituitary. Although negative feedback can inhibit the release of anterior pituitary hormones, this factor is in addition to the regulatory hormones from the hypothalamus.

Newborn babies are born with many innate reflexes, some more complicated than others. In the rooting reflex, a stroke (touch) on the cheek provokes the baby to turn its head towards the side on which it was touched. In the stepping reflex, a touch on the dorsal (top) surface of the foot induces the knee to bend and thigh to flex, creating stepping like movements. Perhaps the most important reflex of all is the sucking reflex that allows the baby to swallow food that reaches the posterior pharynx (throat).In babies, what nerve carries the sensory information involved in the rooting reflex? - VI (6) - V (5) - IX (9) - VII (7)

V (5) Right! The trigeminal nerve (CN V, CN 5) senses touch on the face. CN IX is the glossopharyngeal - this is sensory at the back of the throat CN VI is the abducens - a motor nerve to the muscles that move the eye CN VII is the facial - it has sensory fibers for taste, but is mostly motor to the muscles of the face

Which of the following is an innate reflex that involves a nociceptor? - Withdraw reflex - Any visceral reflex - Tendon reflex - Stretch reflex

Withdraw reflex. Correct! Some reflexes are important to posture and regulating muscle activation. These reflexes use proprioceptors as the sensory neuron (muscle spindles for the stretch reflex and gogli tendon organs for the tendon reflex). Visceral reflexes regulate non-skeletal muscle activity, like heart rate, digestive activity, etc. and involve chemoreceptors or stretch receptors typically. Nociceptors are pain receptors - like when you touch a hot stove, the nociceptor is activated. In the spinal cord, this sensory neuron sends information to an interneuron which then communicates with the somatic motor neurons that withdraw your hand from the painful stimulus.

In babies, what nerve carries the motor information involved in the rooting reflex? A spinal nerve of the cervical plexus - VIII (8) - XI (11) - IX (9) - Some spinal nerve in the cervical plexus

XI (11). Right! The spinal accessory nerve (CN XI, CN 11) innervates the sternocleidomastoid and trapezius muscles involved in head turning. They are the motor arm of this reflex arc. CN IX is the glossopharyngeal - this is sensory at the back of the throat and motor for swallowing. CN VIII is the vestibulocochlear - sensory from the ears for auditory and balance sensory information. Spinal nerves of the cervical plexus do not innervate head turning muscles. The one from this plexus that you know is the phrenic nerve - a motor nerve to the diaphragm for breathing.

Yes or No? Suppose a sensory stimulus triggers an ipsilateral reflex. Does this information also eventually reach the brain? - Yes - No

Yes. Right! Although sensory information will trigger a motor response without the brain being involved, the brain still becomes aware of the information. This occurs because the sensory neuron branches. One branch may lead to the reflex motor neuron, but another will carry information up to the brain. The pathway that carries this information up to the brain involves more synapses than the reflex component. This is why the sensory information seemingly reaches your consciousness well after the motor response has already occurred.

Shown above are the maculae of the vestibule in the ear (receptors that detect head position). Note the action potentials generated in the vestibular branch of the vestibulocochlear nerve. Does this nerve generate action potentials when it is unstimulated by receptor cells of the maculae? - Yes - No

Yes. Well, it turns out they do! There is a background firing rate of the vestibular nerve at all times. When the maculae tilt one way, the action potential frequency increases. When they tilt the other, the action potential frequency decreases. This is useful in the nervous system because the signal is not just on or off. It allows more precise information to be sent to the brain. When you have a receptor in one ear and the other, the brain receives lots of information that it is able to sort out to determine direction.

How would damage to the cell bodies in the left, dorsal gray horn of the spinal cord affect you? - You would not have conscious position awareness from the right side of your body below the damage. - You would not have conscious temperature awareness from the right side of your body at this level of damage. - You would not have conscious position awareness from the left side of your body below the damage. - You would not have conscious temperature awareness from the left side of your body at this level of damage.

You would not have conscious temperature awareness from the left side of your body at this level of damage. Correct! The lateral white matter of the spinal cord contains axons of the spinothalamic pathway. The spinothalamic carries pain, temperature and some pressure information. It is made of different neurons in series. The first order neuron synapses in the posterior gray horn with the cell body of the second order neuron (gray horn of same side as sensory neuron). From here the second order axon crosses over to make up the spinothalamic (anterolateral) tracts/pathways. Damage to the left spinothalamic tracts would interfere with signal transmission of pain, temperature, crude pressure from the right side of the body. Because ascending information must have intact neurons all the way from the entry into the spinal cord up until the brain, if damage occurs in any part of the white matter portion of the pathway, there will be sensory loss at the level of damage and below. If damage occurs just at the gray matter and does not affect different spinal cord levels, you will have sensory loss at that spinal cord level only. The posterior column pathway includes white matter of the posterior region of your spinal cord. It carries fine touch, conscious proprioception (muscle, joint position), vibration and pressure information from the same side of the body. The first order neuron axons make up the posterior column. Because the posterior column is made of first order neurons, they have not yet crossed the body. Therefore, damage to the left posterior column interrupts signal transmission (of specific information) from the left side of the body.

How would damage to the right, lateral white matter of the spinal cord affect you? - You would not have conscious position awareness from the right side of your body below the damage. - You would not have conscious temperature awareness from the right side of your body below the damage. - You would not have conscious temperature awareness from the left side of your body below the damage. - You would not have conscious position awareness from the left side of your body below the damage.

You would not have conscious temperature awareness from the left side of your body below the damage. Correct! The lateral white matter of the spinal cord contains axons of the spinothalamic pathway. The spinothalamic carries pain, temperature and some pressure information. It is made of different neurons in series. The first order neuron synapses in the posterior gray horn with the cell body of the second order neuron (gray horn of same side as sensory neuron). From here the second order axon crosses over to make up the spinothalamic (anterolateral) tracts/pathways. Damage to the left spinothalamic tracts would interfere with signal transmission of pain, temperature, crude pressure from the right side of the body. Damage to the right white matter would inhibit pain, temperature and crude pressure from the left side of the body. Because ascending information must have intact neurons all the way from the entry into the spinal cord up until the brain, if damage occurs in any part of the pathway, there will be sensory loss at the level of damage and below. The posterior column pathway includes white matter of the posterior region of your spinal cord. It carries fine touch, conscious proprioception (muscle, joint position), vibration and pressure information from the same side of the body. The first order neuron axons make up the posterior column. Because the posterior column is made of first order neurons, they have not yet crossed the body. Therefore, damage to the left posterior column interrupts signal transmission (of specific information) from the left side of the body.

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