Lab Two

Question 1

What are mechanoreceptors?

Answer 1

Specialized sensory receptors that respond to touch, pressure, sound, and movement; they can detect both internal and external stimuli.

Question 2

What external stimuli may mechanoreceptors respond to?

Answer 2

Vibrations or touches that are created by wind, sound, water, or those that are transmitted through the substrate.

Question 3

What do internal mechanoreceptors function for?

Answer 3

To provide information about muscle position, contraction, movement as well as leg positioning in space. Referred to as proprioreceptors; provide information about joint angle, muscle length, and muscle tension.

Question 4

What mechanoreceptors are found on the exoskeleton/cuticle of cockroach legs?

Answer 4

1. Setae (short hairs)
2. Hair plates (clusters of hair that bend when adjoining surfaces of the cuticle contact each other in movement)
3. Campaniform sensilla (dome-like structures, distort with movement of the spine or leg)
4. Chordotonal organs (under the cuticle, change in length when the joint is flexed/extended)

Question 5

How are individual action potentials measured?

Answer 5

Through the use of extracellular needle electrodes placed along the sensory nerve.

Question 6

What are Stretch Receptors?

Answer 6

(ex. Chordotonal organs) Detect the position of the leg as the cockroach moves. As the leg is moved from a neutral position, the sensory neuron increases the rate at which it generates APs.

Question 7

What is the firing rate?

Answer 7

Action potential per second, used to monitor leg position. Large firing rate = large leg movement, small firing rate = small leg movement.

Question 8

What is Sensory Receptor Adaptation?

Answer 8

If a stimulus is prolonged over a period of time, the sensory receptor firing rate will decline.

Question 9

What displays very rapid sensory receptor adaptation?

Answer 9

Pacinian corpuscles.

Question 10

What is the pickup source of electrical noise?

Answer 10

Caused by electrical radiation that produces currents in the electrodes and wires leading to the amplifiers.

Question 11

What is a Faraday Cage?

Answer 11

A grounded, screened enclosure around the preparation and electrodes that separates that source of the radiation from the electrodes.

Question 12

What are the ground loops source of electrical noise?

Answer 12

Caused by the ground cable itself serving as an antenna for the noise radiating in the room; avoided by using alligator clips.

Question 13

What are the hind legs of the cockroach called?

Answer 13

The Metathoracic legs; function in moving the cockroach forward.

Question 14

What is the Coxa?

Answer 14

The upper portion of the leg, attaches the leg to the thorax.

Question 15

What is the Trochanter?

Answer 15

Acts like a knee, lets the cockroach bend its leg.

Question 16

What is the femur?

Answer 16

Thigh.

Question 17

What is the tibia?

Answer 17

Shin.

Question 18

What is the Tarsus?

Answer 18

Segmented, acts as the ankle and foot.

Question 19

True or False: Action Potentials from a given neuron will all have the same amplitude.

Answer 19

True, but if recorded extracellularly they may vary in amplitude because they are recording the change in current passing through the electrodes on the outside of the nerve.

Question 20

What does the recorded action potential depend on?

Answer 20

The diameter of the neuron and the distance of the electrodes from the neuron. Larger diameter = larger amplitude.

Question 21

What is Phasic Adaptation?

Answer 21

When the firing rate ceases or is greatly reduced when movement of the receptor stops, even though a new position is maintained.

Question 22

What is Tonic Adaptation?

Answer 22

When action potentials continue for as long as the stimulus is maintained and slowly decline over time .

Question 23

What is Phasictonic Adaptation?

Answer 23

Initial response to a stimulus is a burst of action potentials, then a large drop, and then settles into a gradual decrease.