Biosci 3 postlab.pdf

Postlab of Frog Experiments

Exercise 11 Pithing the Frog

PITHING Ø  make the animal free from pain Ø  destroy the Nervous System Ø  pithing/dissec>ng needle Ø  foramen magnum -‐ cup-‐like depression -‐ located between the skull and the atlas (first cervical vertebra) Ø  single pithing – brain is destroyed Ø  double pithing – brain and spinal cord are destroyed

Signs of Successful Pithing •  Frog will remain limp •  Legs are extended forward or outstretched and frog will quiver

v  Single pithing will only destroy the brain. Frog will s>ll be able to:

Ø  breath Ø  muscles will s>ll contract Ø  heart will s>ll beat

Proper way of restraining the frog during pithing:

•  Legs should be outstretched and held >ghtly between ring and small finger •  Head bent forward , pressure exerted on top of the head by index finger •  Head is bent over the second finger

Exercise 12 Muscle-‐Nerve Prepara>on

Parts of Muscle-‐Nerve Prepara>on •  Scia>c nerve – whi>sh thread-‐like structure lying in between the thigh muscle close to the femur •  Femur •  Thigh muscles •  Gastrocnemius – large muscle at the postero-‐ inferior

part of the lower leg opposite the peroneus •  Tendon of Achilles v  remove peroneus, shinbone (;biofibula) and foot (pes) v Muscle-‐ nerve prepara;on is placed in amphibian Ringer’s

solu;on

Exercise 13 Applica>on of Different Forms of

S>muli

S>mulus -‐  any change in the environment -‐  Tissues maybe s>mulated by: a. mechanical s>mulus (>e and pinch the scia>c nerve) b. thermal s>mulus ( hot and cold water) c. chemical s>mulus (NaCl ) d. electrical s>mulus – (s>mulator) -‐ preferred 1. intensity and dura>on can be controlled 2. it maybe applied and removed easily 3. changes that the electrical s>mulus produces is reversible and do not damage the >ssues

S;mulus Applied Response

1. Mechanical a. Tying single b. Pinching single

2. Thermal a. Hot water single

b. Cold water

single

3. Chemical (NaCl) series

4. Electrical a. Direct single

ANSWER TO QUESTIONS 1.  Which among the different forms of s>muli

applied gives a be\er result? Ans: Among the different forms of s>muli applied,

electrical s>mulus gave the be\er result 1. intensity and dura>on can be controlled 2. it maybe applied and removed easily 3. change that the electrical s>mulus produces is reversible and do not damage the >ssues

2. Why is the chemical s>mulus not frequently applied in the laboratory?

Ans: Chemical s>mulus is not frequently use in the laboratory because it damages the >ssue.

Threshold s;mulus -‐ s>mulus whose strength is just enough to elicit a response Subminimal s;mulus -‐ weaker than threshold s>mulus -‐ does not cause any response Maximal S;mulus -‐ type of s>mulus that causes the greatest response Supramaximal s;mulus -‐ strength is greater than maximal s>mulus but response is similar to that of maximal s>mulus

Exercise 14 The Spinal Frog

•  Spinal frog-‐ single pithing •  Normal frog (only the semicircular canal is destroyed)

Condi;on Spinal Frog Normal Frog

1.  Posi>on of : a. head b. eyes c. limbs

Drooping Half closed Extended

Erect Wide open Contracted

2. Pinching the toes No response

3. Pinching the skin No response

4. Pinching the hind toes No response

5. Response on the other toes

No response

6. Posi>on of the body Tilted to one side (not balanced

Normal posi>on

7. Evidence of sight No response Frog moved

8. Evidence of hearing

No response frog moved

9. Touching the cornea

No response Eyes closed

10. Destruc>on of semicircular canal

Not balanced Normal posi>on

Exercise 15 Complex Coordinated and Uncoordinated Reflexes

Condi;on Observa;on Type of Reflex

Before injec>on of strychnine a. concentrated HNO3 b. immersion in hot water

Frog flexed the leg withdraws the leg

v  all are complex

coordinated reflexes (orderly sequence of muscular contrac>ons

Ager injec>on of strychnine (dorsal lymph sac) a. concentrated HNO3 b. immersion in hot water

S>ffening of the leg (convulsive movements/spasmodic contrac>ons)

v Uncoordinated reflexes

Answer to Ques>ons 1.  What type of reflexes was produced upon the first

applica>on of acid? Ans: The type of reflex produced upon the first

applica>on of acid is complex coordinated. Ager injec>on of strychnine and applica>on of acid? Ans: The strychnine solu>on causes convulsive

movements or spasmodic contrac>on because strychnine binds with glycine which is a neurotransmi\er for relaxa>on and contrac>on equilibrium therefore the muscle remains contracted.

3. Under what group of reflexes will you classify the withdrawal reflex?

Ans: Withdrawal reflexes are classified under complex coordinated reflex.

Exercise 35 The Effect of Temperature on

Heart Rate

Condi;on Results heartbeats/minute

1. Intact heart 60-‐100 beats/min

2. heart in Ringer’s solu>on (room temperature)

Slightly lower than intact heart

3. heart in warm Ringer’s solu>on

v  the higher the temp. the higher the cardiac rate

4. Heart in cold Ringer’s solu>on

v  the lower the temp. the lower the cardiac rate

Sympathe;c Parasympathe;c

Force increases decreases

Rate increases decreases

Rhythm increases decreases

Answer to Ques>ons 1.  How do increased calcium and potassium levels affect the

heart rate? Ans: Increase calcium levels – increase heart rate Increase potassium levels – lower heart rate 2. Differen>ate sympathe>c/parasympathe>c s>mula>on Ans: Sympathe>c s>mula>on – increases cardiac

ac>vi>es Parasympathe>c s>mula>on – decreases cardiac ac>vi>es

Exercise 10 Isotonic and Isometric Contrac>ons

Isotonic Contrac;on

Isometric Contrac;on

Muscle length Shortens Muscle retains original length

Muscle tension Less tension More tension

Iner>a Greater Lesser

Force Lesser force Greater Force

Isotonic Contrac;on -‐ Muscle length changes but the force produced does not

Isometric Contrac;on -‐  Is the condi>on in which muscle length does not change regardless of the amount of force generated by the muscle

Answer to Ques>ons: 1.  Isotonic contrac>ons ex. Walking, wri>ng, running Isometric contrac>ons ex. Simply standing, pushing against a wall 2. Isotonic contrac>on -‐ muscle shortens, mechanical work Isometric contrac>on -‐ muscle >ghtening but no shortening of muscle

Exercise 8 Simple Muscle Contrac>on

•  Single pithing •  Muscle prepara>on (same as muscle nerve prepara>on)

•  Parts of muscle prepara>on? •  Parts removed? •  What muscle is used? v  to produce simple muscle contrac>on, electrical s>mulus is applied to the muscle.

v Muscle is allowed to relax before applica>on of second s>mulus

Myogram -‐ record of muscle contrac>on Muscle twitch/Simple Muscle Contrac>on -‐ brief contrac>on of a muscle fiber in a motor unit in response to a single ac>on poten>al in a motor neuron

Three Phases of Simple Muscle Contrac>on A-‐B lag or latent phase -‐ period ager s>mula>on -‐ contrac>on is not apparent B-‐C contrac>on phase -‐ period when muscle fibers contract (muscle fibers shorten) C-‐D relaxa>on phase -‐ period when the myogram falls -‐ muscle returns to its res>ng state

Exercise 9 Summa>on

1. Summa;on -‐ adding together of individual muscle twitches to make a strong coordinated movements -‐ brought about by sending at least 2 successive s>muli -‐ second s>mulus comes before the end of contrac>on or at the beginning of relaxa>on period.

A -‐ first baseline B -‐ first peak/second baseline C -‐ second peak AB first contrac>on BC second contrac>on CD relaxa>on

2. Second contrac>on is higher than the first contrac>on because of the ff. reasons: a. greater tension is produced on the muscle upon sending more than one s>mulus. b. second contrac>on is higher than the first because it starts at a higher baseline c. greater amount of Ca on the second contrac>on

a -‐ first baseline b -‐ first peak/second baseline c -‐ second peak

The End

Biosci 3 postlab.pdf

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