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You decide to run an experiment in the lab in which you stimulate a neuron two times. If you wait 10 ms between the two stimulations, you can record normal action potentials each time. A. If you only wait 2 ms between stimuli, you are unable to record a second action potential using the same stimulus that caused the first action potential. To remedy this, you apply a larger stimulus to the neuron and are once again able to record action potentials. Name and explain this phenomenon. B. If you switch to a 1 ms interval between stimuli, even increasing the amplitude of the second stimulus does not elicit an action potential. Why is this the case?

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Deanna HettingerLv2

12 Mar 2019

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You are studying the synapse between the violet and red neurons in the rainbow fish. Each time the violet neuron fires a single action potential, the red neuron exhibits a postsynaptic potential with an amplitude of 2mV. You apply ACh to your preparation, then stimulate the violet neuron. Now the red neuron responds to a single action potential in the violet neuron with a burst of action potentials. This effect lasts for several minutes after the ACh is removed.

a. What are TWO possible actions ACh could exert on the red neuron to elicit its effect?

b. What could ACh be doing to the violet (presynaptic) neuron?

c. If you knew the neurotransmitter that was used between violet and red neurons, how could you determine whether the ACh acts on violet (presynaptically) or red (postsynaptic) cell?

Answer question part a-d

Question part A

Diffusion Lab

Purpose: To investigate the diffusion of a substance across a semipermeable membrane.

Materials:

iodine (must be colored, clear won't work)

cornstarch/water solution

plastic sandwich bags (cheap is good)

beakers or clear plastic cups

Set-Up and Procedure
1. Fill beaker about halfway and put about ten drops of iodine.
2. Put about a teaspoon of starch and about 3 ounces of water in baggie and tie.
3. Make sure that it is water tight
4. Put the baggie in the beaker or glass and wait.
5. In about 15 minutes the solution in the baggie will turn blue/black. (purple)
This is a result of the iodine diffusing through the bag.
You should know that iodine is an indicator for starch. It turns blue/black in color.
Test it by dropping some iodine on a piece of white paper.

Questions and Conclusions :

Define permeability

To which substance is the plastic bag is permeable ?

Why did the iodine enter the bag ?

Why didn't the starch enter the beaker?

How is the plastic bag like the cell membrane?

Question part b

Reflex Lab

Procedures for Reflex Lab

In this lab we will test muscle stretch reflexes and cutaneous reflexes.

A partner is needed to be the subject for this lab.

Purpose: To test and observe normal muscle stretch and cutaneous reflexes.

Equipment: Reflex hammer,

Background: In the most narrow sense, a reflex is an involuntary, unpremeditated response by the body to an external stimulus. Reflexes allow reaction to a stimulus more quickly than would be possible if conscious thought were involved. A reflex can be described as a stimulus-response cycle. Most reflexes involve the brainstem or the spinal cord and do not require interaction from higher brain centers. The muscle stretch reflexes are the simplest reflexes. They involve the sensory neuron synapsing directly upon the motor neuron. They are sometimes called monosynaptic reflexes. They are also called spinal reflexes because the reflexive action does not require input from the brain. The other reflexes we will be testing in this lab are the cutaneous reflexes. They are also called superficial reflexes because the receptors are in the superficial areas of the body. They are more complex and require the message to go up the spinal cord to the brain and then back down to elicit the response. These can be used to test for CNS injury.

There are five components to a reflex; these components together are called the reflex arc. The components are as follows:

sensory receptor â receives the stimulus and generates an impulse (is usually a nerve ending)

afferent pathway â a neuron that carries the impulse from the receptor to a central integrating center

integrating center âthis is where the afferent component connects to the efferent component- this is in the CNS. One or more synapses must occur here. Interneurons are not involved in stretch reflexes but are always found in all other types of reflexes.

efferent pathway - a neuron that carries the impulse from the integrating center to an effector.

effector -receives the impulse and responds. The effector may by skeletal muscle, smooth muscle, or glands.

For more information please read chapter 12 : "Muscle" ( Pages 380-390) in Human Physiology book ( 12th edition by Stuart Ira Fox)

Part I. Stretch reflexes.

First do muscle stretch reflexes which are also called deep tendon reflexes.

It is important the subject relax the muscle being tested. Tell the subject to let the muscle go limp.

Rate each response according to the following scale:

+4 very brisk, hyperactive, large movement at joint.

+3 brisker than average, medium movement at joint

+2 average, small movement at joint

+1 somewhat diminished, very small or no movement at joint

0 no response

A. Patellar (also called the knee jerk reflex) â activation of femoral nerve. The receptor is located in the quadriceps muscle, the effector is the quadriceps muscle. The nerve ending is responding to the stretch of the muscle caused by striking the tendon.

1. A subject is allowed to sit comfortably on a table with knees dangling over the edge.

2. Using a reflex hammer (or substitute as described above) strike the patellar tendon just below the kneecap.

3. Observe the action caused by the reflex.

4. Record your results using the graded scale above.

B. Biceps Reflex â activation of the musculocutaneous nerve

1. Rest subjectâs left forearm along your left forearm.

2. Subjectâs hand should rest in or near the bend of your elbow.

3. Press your left thumb on the subjectâs biceps tendon, apply a little pressure.

4. Strike your thumb with the reflex hammer, this will transfer the pressure to the biceps tendon.

5. Watch carefully for twitching of the biceps muscle. Usually, the forearm will not move.

6. Record your results using the graded scale above.

C. Triceps reflex â activation of the radial nerve.

This is a difficult reflex to observe, but give it a try.

1. The subject should have the arm relaxed and elbow bent.

2. Support the entire weight of the arm with your left hand.

3. Strike the triceps tendons, just above the elbow.

4. Watch carefully for twitching of the biceps muscle.

5. Record your results using the graded scale above.

Both B and C show up best on someone who doesnât have a lot of subcutaneous fat and who has good muscle definition.

D. Achilles reflex (also called ankle-jerk reflex) â activation of the poplitealnerve. The principle is similar to the knee-jerk reflex. Here the stretch receptors are located in the gastrocnemius muscle.

1. Have the subject take her/his shoes and socks off, exposing the Achilles tendon on the back of the ankle.

2. Strike the Achilles with the reflex hammer (or substitute) and observe the extension of the foot downward.

3. Record the results using the graded scale above.

Part II. Cutaneous reflexes

A. Plantar reflex

This reflex differs from the four muscle stretch reflexes. In this reflex, receptors are stimulated in the sole of the foot (cutaneous receptors). The reflex pathway travels up the leg to the integrating center. While in the integrating center, the reflex travels up the spinal cord through the pyramidal tracts, which are nerve pathways between the spinal cord and brain.

1. The subject needs to lie on his or her back, with shoes and socks off.

2. Using the end of the handle of the reflex hammer, trace a path along the lateral side from heel to the little toe to the big toe.

3. Observe for the flexion (toe curling) which is recorded as a normal plantar reflex.

4. If the toes curl, this is called a Negative Babinski response and is normal. If the toes flare, then an abnormal response is recorded and is called a Positive Babinski response and indicates CNS damage.

5. Record the results.

B. Ciliospinal reflex â This reflexive pathway is from the skin to the thoracic spinal cord, through the sympathetic trunk, then to the dilator pupillae muscle of the eye. This is another test of the CNS.

1. Pinch the back of the subjectâs neck,

2. Watch pupils for a response.

3. A normal response is dilation of the pupil.

4. Record your results.

question part c

Homeostasis Lab - Heart Beat Regulation

This lab is designed to help explore the process of homeostasis as it applies to regulating heart rate. It also should help how a sampling process works.

Make two copies of the data sheet (or make your own) and paste them into your report.

1. Take a pulse for six seconds, record this number in the table below.

2. Every 15 seconds for the next three minutes, take a pulse again for six seconds, record each of these values.

3. Multiply each of these values by 10 to get the beats per minute.

4. Now average these numbers (this is the setpoint for the pulse at resting). Note the range of values (that is how far they can deviate from the set point).

5. The next step is to take a 30 second reading. Multiply this number by 2 to get beats per minute.

6. How does this compare to the setpoint?

7. Repeat steps 1 through 6 after running in place for 30 seconds. Record the same data.

8. After getting 8 readings, stop and plot these numbers on a piece of graph paper. The X-axis should be minutes and the Y-axis should be heart rate.(Don't forget to connect the points ). You can do this in Excel and then import it into Word. Or you can e-mail this to me.

Submit your lab report in the correct format.. Respond to the questions above. Explain WHY the results were what they were. Compare the resting and post-exercise and postulate explanations for the differences. You should have two data tables and one graph with your heart rate data from both tables on it in your report.

Time in seconds	Heart rate (bpm)
0 (initial recording)
15
30
45
60
75
90
105

question part d

What was one thing you found interesting, confusing or surprising about any of the lab activities? Why?

Exercise #5: The Nervous system and Perception

Task #1: Color vision

Introduction

In the human retina, there are two kinds of light-sensitive cells: rods and cones. These cells are located on the outside of the retina, away from the vitreous humor and against the choroid layer, and are covered by a later of bipolar and ganglion cells as well as neurons. Light enters the posterior chamber through the lens and must pass through several cell layers before it is absorbed by the rods and cones.

Cones are involved in color vision at daylight intensities. Generator potentials in a cone excite one neuron, giving high-level resolution vision. Cones will not cause neural firing at low light intensities and are, therefore, nonfunctional at night.

Rods provoke black-and-white vision at low light intensities. A bipolar cell associates with several rods, so that generator potentials sum in their effect. This assures neuronal firing at low light intensities and provides a highly sensitive vision but with less resolution.

Receptor convergence. A ganglion cell, which receives input from a number of rods, spread out over the retina, cannot pinpoint the source of a light stimulus as well as a ganglion cell, which is stimulated by a single photoreceptor. In the case of a ganglion cell receiving the added input of several rods, light hitting any one of the rods can cause a neural spike in the ganglion cell, but the brain has no way to know which rod was excited. It is therefore harder to pinpoint the location of light stimuli on the retina when the stimulus is detected by rods (as compared to cones). The result is that our ability to see detail, or our resolving power, is considerably lower under dim light conditions than under bright light conditions.

Dark adaptation. If you go from a lighted area to a very dark room, you will not be able to see. After about ten minutes, however, you begin to be able to see again. This occurs because the rhodopsin pigment, which gets broken down when it absorbs light, is continually re-synthesized in the rods. When there is very little light, very little rhodopsin gets broken down and the amount of rhodopsin gradually builds up, making the rod much more sensitive to dim light.

When light strikes a receptor cell, it triggers a photo-chemical reaction that leads to neuronal firing. If a rod or cone receives high-intensity light, the visual pigments will be temporarily bleached and will not absorb any more light. Within a matter of a few seconds, enzyme systems in the cells will restore the visual pigment to its light-absorbing form. This can be easily demonstrated. If, after viewing a bright light, the eye is quickly shut or turned to a dark wall, the bright image will persist as a positive afterimage because the high generator potential causes the continued firing of neurons. If the eye is cast on a lighter background after a few seconds, a negative afterimage, or a dark image of the object will appear. This is because the still bleached cells are not receptive to the light coming from the light background.

According to the Young-Helmholtz theory of color vision, there are three types of cone cells, which respond respectively to red, green, and blue light.

All other colors are perceived as the brain interprets impulses coming from a mix of these receptors. If an object of one color is viewed for a long period of time at high light intensity, the cones for that color will become bleached. The afterimage of the object will be seen in the complementary color.

The Exercise 6 PowerPoint will demonstrate afterimages to you. Use the slide show option to project the square of red light on your entire screen in a dark room. After staring intensely at the square for 30 seconds or so, without shifting your gaze, click enter to change the slide to a soft white. Continue staring at the screen as the change is made. What do you see? What was the color of the afterimage?

Repeat this experiment using a blue square. Before doing the experiment, hypothesize what color the afterimage will be according to the Young-Helmholtz theory.

Hypothesis to be tested: (2 pts)

What did you see when the experiment was conducted? (2 pts)

Was you hypotheses accepted or rejected? (1 pt)

Explain the colors seen in these afterimages using the Young-Helmholtz theory. (5 pts)