Exam 2 Follow-up Questions

Be able to describe the regulation of thyroid hormone levels by the hypothalamus and pituitary gland, and to predict the outcome of various disruptions to the normal mechanisms (e.g. thyroid gland cells unable to respond to TSH).

- Hypothalamus releases TRH - causes anterior pituitary to release TSH - TSH travels through bloodstream to thyroid gland - thyroid gland releases thyroid hormone to target cells When thyroid hormone increases... TRH decreases and TSH increases When thyroid hormone decreases... TRH increases and TSH decreases

***Describe the roles/functions of each of the endocrine system organs we discussed (hypothalamus, pituitary gland, pancreas, and adrenal glands).

- Hypothalamus: control center of endocrine system (neurosecretory cells) direct link between endocrine and nervous systems - Pituitary gland - Pancreas - Adrenal glands

Compare your ability to detect light to the way plants detect light. Include similarities/differences in sensing, communicating, and responding.

- Plants detect light with photoreceptors in leaves: People don't have leaves- they absorb it through their eyes. - plant use light for energy, people use light to see.

Describe the difference between voltage-gated ion channels and chemically-gated ion channels.

- chemically-gated open/close in response to interaction of molecules - voltage-gated open/close in response to changes in relative charge inside vs. outside neuron

Why can humans detect a much wider range of smells than tastes?

- each individual olfactory receptor cell has one of 1000's of possible receptor protein types - integration and interpretation of signals in brain generates unique smell "fingerprint"

When gated sodium ion channels in the membrane of a resting neuron open, in which direction will ions move? What if gated potassium ion channels open? Explain your answers.

- gated sodium ion channels open, allowing sodium ions to move from outside to inside the cell (higher to lower) - gated potassium ion channels open, potassium rushes out of the cell and decreases the membrane potential (higher to lower)

***At some chemical synapses, dopamine acts as an excitatory neurotransmitter. At other chemical synapses, it is inhibitory. Describe dopamine's effects on the receiving neuron in each situation, then propose one explanation for how dopamine can function both as an excitatory and an inhibitory neurotransmitter.

- inhibitory neurotransmitters decrease the likelihood that an action potential will occur (farther from threshold) - excitatory neurotransmitters increase the likelihood that an action potential will occur. (bring men pot closer to threshold)

Explain why hormones released by cells in your adrenal medullae function in your short- term stress response and hormones released by cells in your adrenal cortices are important for your long-term stress response.

- medulla uses nervous system signals which travel very quickly (quick reaction time needed for short-term stress response) - cortex uses endocrine signals which are much slower than nervous system signals but last a longer amount of time (needed to sustain long-term stress response

Describe the differences between a neuron, a neurosecretory cell, and an endocrine cell.

- neuron: nervous system cells thats conduct electrical nerve signals - neurosecretory cell: sends and receives nervous system and endocrine system signals, functioning as the connection between the two systems - endocrine cell: produce and release their own hormones in response to specific signals, hormones act as messenger rather than electrical signal

What does it mean that action potentials are local events?

- occur at a specific place in membrane - inactivation of voltage-gated Na+ channels prevents another action potential from occurring in the same place for a brief period of time

Explain why each of the four criteria we discussed for identifying a new taste is important, and why demonstrating all of them are necessary to establish the existence of a sixth taste.

- receptor protein(s) that interact with chemicals associated with the taste - taste receptor cells (with receptor proteins) that respond to chemicals associated with the taste - signals transmitted to taste processing region of brain perception of taste in the absence of other tastes The flavor must be interpreted by interneurons as one of the basic tastes, integration is needed to perceive more than one flavor at once, these 4 criteria are important to make sure a new taste has a specific chemical that binds to specific receptors and creates a response.

List as many properties/features of hormones as you can remember without looking at your notes. Then review your notes to check yourself.

- send chemical messages that are important for long distance communication within the body - receptor proteins only interact w one type of hormone individual cells have multiple types of hormone receptors - there are different types of hormone receptors for the same hormone on different types of cells - the same hormone can have different effects on the same cell - a small amount of hormone causes a can cause a large response in a target cell - most processes are caused by multiple hormones - the same hormone can be involved in many processes

Look back at the results from the taste analysis. Which taste(s) was/were detected by the greatest number of papillae? The fewest number? Based on what you know about taste receptors, taste buds, and papillae, propose a hypothesis to explain why the sensitivities of an individual papilla to particular tastes could be different.

- sour was detected by the greatest number of papillae - salty was detected bye the fewest number of papillae - sensitivity of individual papilla to particular tastes could be different depending on the types of receptor cells contained in the papilla.

Explain/describe role of sodium-potassium pumps in nervous system signals.

- transport of ions by sodium-potassium pumps restores resting potential - 3 Na out for 2 K in - always functioning (action potentials don't alter its function)

In your own words, describe what happens when an action potential reaches the synaptic terminal of a neuron at a chemical synapse. Now do the same thing for an electrical synapse

Chemical - neurons produce specific type of neurotransmitter and store in vesicles - action potential reaches synaptic terminal of sending neuron - triggers stored neurotransmitters to be released into synaptic cleft and and then interact with specific receptor proteins on the membranes of receiving neuron. Electrical - when the action potential signal reaches the synaptic terminal of sending neuron, the action potential signal is transmitted directly - ions flow directly from the sending neuron to receiving cell through the channels that connect the membranes

How are chemoreceptors similar to photoreceptor cells? How are they different?

Chemoreceptors - sensory receptor cells that detect presence of chemicals - have receptor proteins in membrane - each type can only interact with specific chemicals - can be modified epithelial cells cells or sensory neurons - interaction with chemical alters membrane potential of chemoreceptor Photoreceptors - sensory receptor cells that detect and convert light stimuli into nervous system signals - two types (rods and cones) - certain rods/cones only detect/reflect one light color - rods and cones are modified epithelial cells (not neurons) - interaction with light alters membrane potential of photoreceptor

Find someone you know who hasn't learned about the human sensory system and explain to them the cause of color blindness.

Colorblindness is due to the inability of one or more types of cones to respond to light. The different types of cones sense different types of light, so if these are not able to respond, a person will not be able to see that color. This can happen if the opsin protein specific to that cone is unable to function or if the specific opsin protein cannot be produced. Light sensitive opsin protein go from resting state to a signaling state upon light absorption and determines which wavelengths of light are absorbed best (cause the most membrane potential change).

What's a myelin sheath? Explain the role/importance of myelin sheaths in nervous system signaling.

Myelin sheaths are like insulation around wires. They help prevent "cross wiring" (transmission of a signal to a different neuron if their axons touch each other). One type of myelin sheath is a Schwann cell.

Compare the function of your nervous system control center (brain and spinal cord) and control of hormone signaling by your hypothalamus and pituitary gland.

Nervous System: receive signals from neurons, integrating, respond via electrical signals. Hypothalamus: receive signal, signals to PG to release hormone to other organs and target cells.

Make a table to start keeping track of similarities and differences between your nervous and endocrine systems.

Nervous system - faster response/reaction time - uses electrical impulses to send messages (neurotransmitters) - organs= brain, spinal cord, nerves - uses neurons Endocrine system - slower response/reaction time - uses hormones to send messages - organs called glands - signals travel through bloodstream Both - react to stimuli - help maintain homeostasis - send messages - hypothalamus links between the two systems - particular hormone/neurotransmitter cause different effects

Neuron parts and describe their functions.

Neurons: nervous system cells that conduct nerve signals dendrites: highly branched extensions that receive signals cell body: receives and integrates signals (gets messages via dendrites and from other cells) axon: transmits signals axon hillock: point where cell body and axon meet (signals start here) synaptic terminals: ends of axon branches where signals are transmitted to next cell

Compare the signals involved and the changes that occur during your short-term vs. long-term stress responses.

Short term - hypothalamus sends nerve signal through CNS neuron to spinal cord - spinal cord sends nerve signal through PNS neuron to adrenal medulla - neurotransmitter signals are received by adrenal medulla and epinephrine is released - epinephrine increases heart rate, opens airways, increased blood glucose levels Long term - Hypothalamus releases CRH to the anterior pituitary - anterior pituitary releases ACTH - ACTH travels to adrenal cortex - adrenal cortex releases cortisol - cortisol causes liver cells to release glucose into blood, muscle cells switch to use fats for fuel instead of glucose, immune system cells reduce activity

Although it is frequently used, explain why the statement "An action potential moves down an axon" is NOT the best way to describe how a signal gets from the cell body to the synaptic terminals of a neuron.

Signal transmission along an axon is like a stadium wave (individual action potentials don't move)

Why do objects appear sharper and more distinct in bright light, but fuzzier in dim light? Why does a bright red apple appear more gray in dim light?

Signals from many rod cells transmitted to single bipolar cell - amplifies dim light signals, but makes images fuzzier Few cone cell signals transmitted to single bipolar cell - images are sharper in bright light

Explain why signals travel more rapidly along myelinated versus un-myelinated axons.

Signals travel more rapidly along myelinated axons because in a myelinated axon the action potential can hop down the axon (node to node) instead of having to travel down the entire axon, the way an action potential has to in an un-myelinated axon.

What are the two kinds of ions important for nerve signals? Indicate their charges.

Sodium ions (Na) + Potassium ions (K) +

How is the sodium-potassium pump different from gated ion channels? Describe what the sodium-potassium pump does (i.e. how many of each type of ion does it move and in what direction).

Sodium-potassium pumps: use energy to move Na+ and K+ in specific directions - three Na+ ions out for every two K+ moved in (ALWAYS functioning)

Describe signal integration in your own words and explain why it is important. If a neuron receives multiple excitatory stimuli simultaneously, can you be sure that it will generate an action potential? Why or why not?

The action potential generated depends on the amount of both excitatory and inhibitory stimuli (SUM TOTAL) acting simultaneously so we could not be sure that it would generate and action potential if it received multiple excitatory stimuli.

Explain why the hypothalamus can act as the communication link between your nervous and endocrine systems.

The hypothalamus contains neurosecretory cells that allow it to send and receive signals from the nervous system and endocrine system.

Describe the relationship between your hypothalamus, anterior pituitary, and posterior pituitary (i.e. how and in what directions is information communicated between them).

The hypothalamus sends signals to the anterior and posterior pituitary glands. These glands cannot communicate back. Posterior: hormones released in response to nervous system signals, neurosecretory cells connect, extension of hypothalamus Anterior: produce and release its one hormones when controlled by hypothalamus

Humans can detect MANY different bitter-tasting chemicals, but cannot distinguish between them. Use what you know about chemoreceptors, receptor proteins, and perception to propose a reasonable hypothesis to explain why.

The same component of the chemical binds to the same receptor, although the chemicals may be different, they still have the same part that interacts with or all bitter cells go through the same interneuron (evolutionary- don't care to distinguish between these different flavor bc we dont want to take bitter)

Propose a hypothesis to explain the difference in the overall sensitivity (average frequency of detection for all tastes) of papilla #1 (first graph) and papilla #15 (last graph) observed in the taste analysis.

There are fewer receptor cells in papilla 15 than papilla 1

***Which type of ion channel, voltage-gated or chemically gated, is important during an action potential? why?

Voltage gated sodium ion channels

Describe the similarities and differences between signal transmission at chemical and electrical synapses.

Electrical synapses - faster - sending and receiving neuron are directly connected - direct passing of ions through sodium ion channels - more likely to generate an action potential - cannot be modified Chemical synapses - slower - gap between sending neuron and receiving neuron (synaptic cleft) - chemicals transmitted via neurotransmitters - can be modified

Based on what we've discussed describe/explain how the different parts of your nervous system might work together to allow you to catch a pen that rolls off your desk. Include the specific function categories of neurons in your description.

Eyes see and send signal to brain Brain interprets message from eyes Brain sends signal to muscles to catch pen

In what direction(s) does information flow through the different parts of the nervous system - the CNS and the two divisions of the PNS?

Flows from sensory neurons on the PNS to interneurons in the CNS, and then back to motor neurons in the PNS to cause a reaction

Make a list of observations that would allow you to determine whether a chemical should be classified as a hormone or a neurotransmitter. What observations would NOT be helpful (i.e. what would you expect to see for BOTH a neurotransmitter and a hormone)?

Hormones - travel via the bloodstream - reach ALL cells Neurotransmitters - released into synaptic clefts - act as communication links between specific cells Both - must interact with a receptor protein to cause a response in a cell - allow communication to cells that are not neurons - small amount is enough for a response - specific type can have different effects (e.g. in different target cells, at different synapses) - mechanisms exist to stop signal (remove from bloodstream or synaptic cleft)

Describe the role of hormones in maintaining homeostasis.

Hormones allow the body to respond to stimuli by causing a response in target cells. Hormones allow the body's internal conditions to remain within a healthy "normal" range (ex. temp, water, glucose).

What does it mean that hormone receptors are specific for a particular type of hormone? Write a sentence that explains why it is important that a particular type of hormone receptor is specific for a particular type of hormone.

Hormones can only bond to particular receptors because it allows for reactions to be specific and efficient.

If two drugs are added simultaneously to a neuron, one that opens voltage-gated Na+ channels and one that opens voltage-gated K+ channels, do you think that the neuron will generate an action potential? Explain your answer.

If they open at the same time, it is unlikely that enough positive charge will build to cause the continuation of an action potential down the neuron. Explanation: Enough build up of positively charged sodium ions must occur before potassium channels open. (only if it happens to cross the threshold)

You leave a brightly lit hallway and enter a dark room. Explain why you can't see very well right away, but over time you are able to see more clearly.

In a bright room all your rods absorb light (they are maxed out) and the rod retinal pigments are in straight form. It takes time for the retinal pigments in rod cell opsin proteins to be removed and replaced with form that can absorb light

Heart muscle cells and skeletal muscle cells (the ones attached to your bones) both respond to thyroid hormones. Based only on that information, what do you know about heart muscle and skeletal muscle cells?

although they have different cell types, heart muscles and skeletal muscles both have a receptor protein for thyroid hormone and thyroid hormone regulates a process related to both organs.

A neuron is stimulated so that its membrane potential is just above the threshold. Later, the same neuron is stimulated so that its membrane potential is significantly above the threshold. Compare what will happen after the first and second stimulation events in terms of action potential generation.

both will generate an action potential because action potentials are "all or nothing" if the membrane potential is above the threshold, a membrane potential will be generated

Your liver and muscle cells respond differently to the hormone insulin. Propose at least one hypothesis to explain how insulin could cause different responses in your muscle vs. your liver cells.

different receptor types are present on different types of cells. Muscle and liver cells could have different types of receptors that cause insulin to respond differently in each cell.

Explain why blue cones, red cones, and green cones detect different wavelengths of light. What determines that blue cone signals are interpreted as blue, red cone signals as red, and green cone signals as green?

different types of opsin protein for each color

Explain why action potentials are described as "all-or-nothing" events. Come up with an analogy other than flushing a toilet to describe this property of action potentials.

do not vary in size (once it reaches the threshold it will always send action potential) only thing that can change is the frequency)

***Draw and label your own diagram to describe how hormone signals are regulated by negative feedback (make a "one-hormone" sketch and a "multi-signal" sketch).

hormones are released that counteract change caused by a stimulus. Hormone levels are controlled by negative feedback loops. They hypothalamus is the control center of the endocrine system that acts as the link between the nervous and endocrine system and regulates many hormones.

What determines which chemicals a chemoreceptor can detect?

if it has the receptor protein for that chemical.

If the alpha cells of your pancreas could no longer produce glucagon, how would that affect the ability of your body to regulate blood glucose levels? What if target cells lost the ability to respond to glucagon signals? Now answer the same questions for beta cells and insulin.

if the pancreas could no longer produce glucagon, there would be no way for glucose to be released back into the blood if there wasn't enough. The same would occur if target cells were unable to respond to glucagon because although it is being produced the cells cannot respond and glucose could not be released into the blood.

Describe how insulin and glucagon regulate blood glucose levels and explain why glucagon and insulin are an example of antagonistic hormones.

insulin allows glucose to be taken out of the bloodstream when there is too much and glucagon puts glucose back into the blood stream when there isn't enough. These hormones cause an opposite reaction on the same process, therefore they are antagonistic.

Describe how/why regulation of insulin by blood glucose levels is an example of negative feedback. Do the same thing for glucagon.

it is an example of negative feedback because because the hormones act to counteract the stimulus and move it in the opposite direction.

Why is it important that mechanisms exist to remove hormone signals from your blood stream?

it is important that we can remove hormones from the blood bc hormones are released to counteract a stimulus. When that stimulus no longer needs to be counteracted, we need to get rid of the hormone so that the body remains within a normal range. Endocrine cells monitor levels of hormones in the blood and release another hormone to bring the hormone level back to normal.

If a neuron is treated with a drug that inhibited sodium-potassium pumps, will the neuron continue to be able to generate nerve signals? Explain your answer.

no bc there would be no membrane potential

Choose a papilla from the experiment carried out by Bealer and Smith that could only detect one taste. Propose a reasonable hypothesis to explain why the papilla could only detect one taste.

papilla 12 could only detect sweet. It could only detect sweet because it only had receptor cells for the sweet chemical.

Explain what selective permeability means. What does it mean that membrane proteins are specific? Explain the importance of selective permeability and specificity of membrane proteins in the context of nervous system signaling.

selectively permeable membrane: proteins in membranes (membrane proteins) tightly control movement of molecules in and out of neuron (Note - Selective permeability is a property of ALL cell membranes!)

In your own words, describe the role of the sensory system in maintaining homeostasis.

senses gather stimuli and send it to the nervous system nervous system responds to stimuli.

You walk into your apartment and notice that it smells like the toast you burned in the morning. Propose an explanation for why, after a few minutes, you do not notice a burnt toast smell.

sensory receptor cells stop responding to the smell because the brain filters the signal out in order to allow us to focus on what is changing rather than what is already there.

Describe/explain the difference between synergistic and antagonistic hormones.

synergistic- hormones that cause changes in target cells that have the same effect on a particular condition antagonistic- both hormones regulate the same condition but do opposite things (causes the opposite effect on a particular condition.

Compare your senses of taste and smell. Include similarities and differences between the chemoreceptors involved, and how signals are transmitted to your brain.

taste - modified epithelial cells - signals from taste receptor cells transmitted to brain via sensory neurons - integrated - 5 tastes Smell - neurons - neurons detect airborne chemicals - integrated - more than 1000 different smells (chemicals)

You put a piece of lemon in your mouth. In general terms, explain why your reaction is "sour!" rather than "sweet!"

the chemical from the lemon binds to receptor proteins on cells that can interact with sour tastes. This interaction then changes the membrane potential of the cell and causes a increase in neurotransmitter release. This sends signals to the brain to perceive sour rather than sweet.

***In your own words, define resting potential. Sketch a resting neuron. Indicate where the concentrations of sodium ions and potassium ions are highest and the relative charges inside and outside the cell. Explain why the conditions inside and outside a neuron are like this when a neuron is at rest.

the membrane potential of a neuron when it is NOT sending signals due to the sodium-potassium pump, voltage channels closed

Explain why all rods detect the same wavelengths of light. Explain why rod signals are all interpreted as shades of gray.

there is only one type of rod that contains one type of opsin protein. Opsin proteins determine the wavelengths of light that retinal (pigment molecule in rods and cones that absorbs light) can absorb. Since rods only contain one type of protein, they only detect the one wavelength of light (grey).

In the taste experiment, participants rinsed their mouths with distilled water and the researchers waited one minute between each solution application. Every 10 trials, they also gave the participants a five minute break. Why were these breaks between trials important? Hint - Think about what might happen if a taste receptor was repeatedly stimulated over a long period of time.

to ensure that the taste receptors do not experience sensory adaptation.

Many spicy foods cause people to experience a burning sensation. Propose a hypothesis to explain this observation.

when the chemical in spicy food binds to the receptors in our mouth, the signal is sent to the brain indicating a spicy food. This signal is to warn us and prevent us from consuming spicy foods that may be dangerous. We feel it as a burning sensation because this is something we do not want to feel. Although spicy foods aren't actually hot, they create this sensation to warn our body.

The same amount of pressure is applied to two different sensory receptor neurons that detect touch in your skin. One generates action potentials and one does not. Propose a hypothesis to explain this observation. Hint - Think about what determines whether or not a sensory receptor neuron generates action potentials.

whether the membrane potential change reaches the threshold or not determines whether an individual touch receptor neuron sends action potential signals to your brain when something touches your skin.

Review the experiment we discussed that assessed the ability of individual papillae to detect chemicals associated with different tastes. Why was it important to determine whether droplets of solution applied to individual papilla spread on a person's tongue?

(look at HW 6)

In one sentence, summarize the role of the nervous system in maintaining homeostasis.

Processes, integrates, and transmits information regarding vast majority of internal/external conditions

Explain the role of glial cells in the nervous system.

- Cells that act as neuron "support system" - Multiple types- exact functions not understood - Known functions include supplying nutrients & maintain homeostasis of surrounding environment & insulation

Describe the steps from when light enters your eyes to when signals from a photoreceptor reach interneurons in your brain.

1) absorption of light causes retinal pigment to be replaced (goes from bent form to straight form when exposed to light) 2) shape change alters membrane potential and decreases the amount of neurotransmitters released (more neurotransmitter at synapse in dark than light) 3) reduction in amount of inhibitory transmitter can allow action potential signals to be transmitted to the brain.

Describe how a signal is transmitted along the length of an axon. Explain why signals always travel from axon hillock to the synaptic terminals.

One way street, When an action potential reaches the axon terminal, neurotransmitters stored in vesicles in the terminal buttons of axons are released into the synaptic cleft. In the cleft, the neurotransmitters bind with corresponding receptors of post-synaptic neurons and lead to a configurational change in the neuron, allowing positively charged particles to enter the neuron. This begins another action potential in the dendrite of the neuron. After neurotransmission, the neurons are released into the synapse where they are either reabsorbed or deactivated by enzymes. If, in case, the neurotransmitter is blocked or replaced, the physiological state is affected, leading to a change in mood, cognition and behavior.

Explain why your perception of the world around you is determined by the types/locations sensory receptors and the communication links they form with interneurons in your CNS. Use an example to illustrate your description.

Our perception of the world around us is based on what our sensory receptor cells can detect (how sensory receptor cells connect and communicate with interneurons). Ex. how much we perceive a stimulus is based on other conditions (a clock ticking)

Compare the structures and properties of rods and cones.

Rods - Very sensitive to light - takes a small amount of light to alter membrane potential - signals not interpreted as different colors (why objects appear grey in dim light) - modified epithelial cells, NOT neurons - ONE type of opsin protein Cones - less sensitive to light - three kinds that detect different wavelengths (colors- blue green and red a combination of signals is generated from all three type of cones through integration by neurons, allows us to see a wide variety of colors) - modified epithelial cells, NOT neurons - each type of cone has a DIFFERENT kind of opsin protein

Why are the signals that reach your brain from photoreceptors said to be "partially integrated"? Explain the benefits of partial integration of photoreceptor signals.

They are partially integrated because you receive parts of the signals from each of the different cone types—some from red, blue, and green. The benefits include sharper images and improved ability to detect low levels of light.

Find someone who is not in the class and explain to them why virtually all type 1 diabetics are treated with insulin injections, while insulin injections are much less effective at treating type 2 diabetes and therefore not frequently prescribed.

When someone has type 1 diabetes they cannot produce enough insulin so they must be treated with more. People with type two diabetes have cells that are unable to respond to insulin, so even if they were given an injection, their condition would not be affected because they already produce enough insulin on their own.

***Give one example of a hormone we discussed whose release is controlled by hypothalamus signals. Give one example of a hormone we discussed whose release is NOT controlled by hypothalamus signals.

cortisol is controlled by hypothalamus signals

Describe TWO ways in which a drug could decrease signaling at a chemical synapse. Describe TWO ways a drug could increase signaling at a chemical synapse.

decrease - decrease amount of neurotransmitter being released - make reuptake of neurotransmitters faster - increase degradation of neurotransmitters - mimic neurotransmitters and block receptors increase - increase amount of neurotransmitter being released - make reuptake of neurotransmitters slower - decrease degradation of neurotransmitters

Propose a reasonable hypothesis to explain why liver, muscle, and adipose (fat) cells respond to insulin, but only liver cells respond to glucagon.

liver, muscle, and fat cells respond to insulin because they are all responsible for absorbing glucose out of the blood while only liver cells respond to glucagon because it is responsible for releasing glucose back into the blood.

Explain why regulating blood glucose (sugar) levels is essential for maintaining homeostasis.

reduce the risk of diabetes and heart disease, we just need enough glucose to fuel the cells, but not enough to overload the bloodstream.

***A drug prevents cells in your hypothalamus from responding to cortisol. How would the levels of releasing hormone, ACTH, and cortisol during long-term stress be different in the presence of the drug vs. without the drug? What if cells in your anterior pituitary could no longer respond to cortisol? What if cells in your anterior pituitary could no longer respond to CRH (the releasing hormone that promotes ACTH release)?

releasing hormone increases ACTH increases cortisol increases

You've probably heard someone say that eating carrots, which contain a significant amount of vitamin A, improves your ability to see at night. Explain why a vitamin A deficiency affects your ability to see in the dark AND in brighter light and increasing your vitamin A consumption will improve your ability to see under all light conditions.

retinal is a pigment molecule in rods AND cones that absorbs light. Retinal is made from vitamin A, which is highly abundant in carrots. The more retinal pigment, the greater the chance to absorb light, both at night, and in the day.