Muscle and Nerve Experiments

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Questions and Answers

Calculate the MCV using the provided values.

88 µm³ (correct)

95 µm³

79 µm³

72 µm³

What does a low MCH value indicate?

Normal hemoglobin levels

High cell volume

Dehydration

Iron deficiency anemia (correct)

Which blood group lacks A and B antigens on red blood cells?

O (correct)

What principle is used for determining blood groups?

Agglutination reaction of RBCs with antibodies Signup and view all the answers

In what scenario would agglutinins be present in plasma?

When the corresponding antigen is absent Signup and view all the answers

What characterizes the latent period in a simple muscle twitch (SMT)?

It involves propagation of action potential through the nerve fiber. Signup and view all the answers

How does warming affect the simple muscle twitch (SMT)?

Decreases the duration of biochemical reactions responsible for contraction. Signup and view all the answers

What is a primary effect of muscle fatigue on the simple muscle twitch (SMT)?

Decreased amplitude of SMT. Signup and view all the answers

How does cooling the nerve and muscle affect SMT?

It increases viscosity and resistance to contraction. Signup and view all the answers

What occurs during the contraction phase of a simple muscle twitch?

Physical and chemical changes involve actin and myosin. Signup and view all the answers

What phenomenon is observed during the initial contractions of repeated stimulation?

Staircase phenomenon. Signup and view all the answers

What triggers the 'genesis of tetanus' in muscle experimentation?

High-frequency stimulation with no rest. Signup and view all the answers

What happens when the frequency of stimulation is increased to 10 / second?

Tetanus is produced, resulting in continuous contraction. Signup and view all the answers

What phenomenon occurs when skeletal muscle is subjected to repeated maximal stimuli after a period of rest?

Staircase phenomenon Signup and view all the answers

What is the effect of warming on tetanus?

It enhances the contractions to obtain clonus. Signup and view all the answers

How do mechanical contractions differ from electrical responses in muscle function?

Electrical responses never fuse into a sustained contraction. Signup and view all the answers

What role does Ca+2 play in muscle contraction during the staircase phenomenon?

It elevates within the cytoplasm, enhancing contraction strength. Signup and view all the answers

What is the nature of Compound Action Potential (CAP)?

It comprises the summed action potentials of various neurons in a nerve trunk. Signup and view all the answers

What is an effect of cooling on muscle function during clonus?

It converts clonus into tetanus. Signup and view all the answers

What characterizes the peaks observed in a Compound Action Potential (CAP)?

They represent differences in conduction speeds of various nerve fibers. Signup and view all the answers

Which of the following is true regarding tetanic contractions?

They are the primary method by which muscles perform useful work. Signup and view all the answers

What defines a motor unit?

A motor neuron and all the muscle fibers it innervates. Signup and view all the answers

How does increased nerve diameter affect conduction velocity?

It decreases internal resistance, leading to increased conduction velocity. Signup and view all the answers

What is the primary function of hemoglobin in red blood corpuscles?

To transport oxygen in the bloodstream. Signup and view all the answers

Which of these statements regarding red blood corpuscles (RBCs) is true?

RBCs are non-nucleated biconcave discs. Signup and view all the answers

What measurement reflects the average volume of a single red blood corpuscle?

Mean corpuscular volume. Signup and view all the answers

What effect does myelination have on conduction velocity?

It speeds up conduction by allowing action potentials to jump between nodes. Signup and view all the answers

What is the typical RBC count for an adult female?

4.8 million/mm3 Signup and view all the answers

How is nerve conduction velocity (m/s) calculated?

Distance / latency. Signup and view all the answers

Which factor describes the blood component that makes up 55% of its composition?

Plasma. Signup and view all the answers

What is the typical range of hemoglobin concentration in adult males?

15-16 g/dl Signup and view all the answers

What is the formula used to calculate Mean Corpuscular Volume (MCV)?

MCV = PCV X 10 / RBCs count (millions) Signup and view all the answers

Which type of anemia is characterized by a normal size and hemoglobin content in red blood cells?

Normocytic Normochromic Anemia Signup and view all the answers

What is a common symptom of anemia?

Headaches Signup and view all the answers

In microcytic hypochromic anemia, the red blood cells are:

Smaller than normal and contain less hemoglobin Signup and view all the answers

What is the normal range for Mean Corpuscular Hemoglobin Concentration (MCHC)?

32-38 gm/dl Signup and view all the answers

Which of the following is a cause of macrocytic hyperchromic anemia?

Vitamin B12 deficiency Signup and view all the answers

Which condition results from acute blood loss?

Normocytic Normochromic Anemia Signup and view all the answers

What indicates anemia in terms of oxygen carrying capacity?

Decreased hemoglobin content Signup and view all the answers

Which of the following factors does NOT contribute to bone marrow depression?

High iron intake Signup and view all the answers

A person exhibiting cold hands and feet may be experiencing symptoms of:

Anemia Signup and view all the answers

Study Notes

Nerve and Muscle Experiments

Experiments use the sciatic-gastrocnemius preparation.

Neuromuscular Transmission

Arrival of action potential to presynaptic motor terminal triggers acetylcholine (ACh) release via exocytosis.
ACh binds to nicotinic receptors on the motor end plate.
Increased permeability to sodium (Na+) ions leads to the end-plate potential (EPP).
Generation of an action potential (AP) in the adjacent areas of the muscle fiber.

Simple Muscle Twitch (SMT)

Definition: A single contraction followed by relaxation due to a single stimulus.
Stimulus: Single maximal stimulus applied indirectly (to the nerve).
Principle: Stimulating the sciatic nerve with a single maximal stimulus causes a contraction followed by relaxation of the gastrocnemius muscle.

Phases of SMT

Latent period (0.01 seconds): Events occur before contraction, including action potential propagation, synaptic delay and muscle fiber internal changes.
- Propagation of action potential through the nerve fiber.
- Synaptic delay at the neuromuscular junction.
- Generation of action potential on sarcolemma.
- Physical and chemical muscle changes (like actin and myosin sliding).
Contraction phase (0.04 seconds): The muscle actively contracts
Relaxation phase (0.05 seconds): The muscle passively relaxes after contraction.
Total time of SMT = 0.1 seconds

Effect of Temperature on SMT

Warming increases contraction speed and reduces the resistance to contraction. Warm muscles contract faster and relax quicker.
Cooling slows the speed of contraction and increases resistance to contraction. Cold muscles contract more slowly and take longer to relax.
- Increased viscosity during cooling means decreased resistance to contraction
- Contraction/relaxation is faster with warmth

Effect of Fatigue on SMT

Steps for the experiment
- Record a Simple Muscle Twitch (SMT)
- Apply 10 stimuli without recording; then record the next contraction
- Repeat steps to gradually fatigue the muscle
- Remove the electrodes from the nerve and stimulate the muscle directly
Fatigue leads to a reduction of SMT amplitude (becoming weaker) and an increase in duration.

Effect of Several Successive Stimuli "Genesis of Tetanus"

Steps to the experiment.
- Set up the equipment like for a simple muscle twitch.
- Stimulate muscle at a low frequency (e.g., 2/second) to get separate contractions.
- Gradually increase the stimulation frequency (e.g., 5/second) to induce a staircasing contraction pattern called clonus.
- Further increasing the stimulation frequency (e.g., 10/second) causes continuous contraction which is known as tetanus.

Observations on Tetanus

Mechanical contractions can fuse to produce tetanus in the muscle, but the electrical response (action potentials) never fuses. Muscles typically contract by tetanic contractions which allow for sustainable work
Tetanus is the more common method for muscle contraction in the body versus the SMT.

Staircase Phenomenon

If skeletal muscle is stimulated rapidly and repeatedly as in a series of maximal stimuli(clonus, tetanus), during rest intervals to avoid fatigue each successive contraction usually increases in amplitude. This is due to increasing calcium (Ca2+) concentrations in the cytoplasm of the muscle fibers.

Effect of Temperature on Clonus and Tetanus

Warming increases frequency of stimulation to achieve tetanus.
Cooling increases frequency of stimulation to achieve clonus.

Compound Action Potential (CAP) and Nerve Conduction Velocity (NCV)

Used to evaluate the conduction of electrical impulses through peripheral nerves.
CAP represents the summed action potentials of many neurons in a nerve trunk.
A CAP shows multiple peaks due to different types of nerve fibers having different conduction speeds.
Nerve conduction velocity (NCV) is calculated by dividing the distance between stimulating and recording electrodes by the latency (time).
NCV increases with larger nerve fiber diameter.
NCV increases with myelination via saltatory conduction (jumping impulses from node to node along the axon).

Blood Composition

Blood is made of plasma (55%) and cellular components (45%).
- Plasma: liquid portion of blood, containing water, proteins, electrolytes, nutrients, and waste products.
- Cellular components: Made up of red blood cells (erythrocytes, RBCs), white blood cells (leukocytes) and platelets.

Red Blood Corpuscles (RBCs)

Non-nucleated biconcave discs.
In adult males the number of RBCs is 5.4 million/mm3 , in females it is 4.8 million/mm3.

Hemoglobin (Hb)

Red pigmented substance in RBCs that carries oxygen.
Adult male Hb: 15-16 g/dL, females 13-14 g/dL. Newborns have 19 g/dL.

Hematocrit (PCV)

Percentage of RBCs in blood
Male: 46 +/- 6%, Female: 42 +/-6%.

Blood Indices

Mean corpuscular volume (MCV): Average volume of a single RBC. Normal range: 80-95 μm³
Mean corpuscular hemoglobin (MCH): Average amount of hemoglobin in a single RBC. Normal range: 25-32 pg.
Mean corpuscular hemoglobin concentration (MCHC): Concentration of hemoglobin per unit volume of RBCs. Normal range: 32-38 g/dL.

Anemia

Decrease in oxygen-carrying capacity of blood (due to RBC or hemoglobin deficiency).
Symptoms: dizziness, headache, growth problems(children), shortness of breath, pale or yellow skin, cold extremities, tiredness, tachycardia (fast heart rate).

Classification and Causes of Anemia

Normocytic normochromic anemia: Normal sized and coloured RBC, but decreased number.
Microcytic hypochromic anemia: Smaller than normal and paler RBCs, due to iron deficiency.
Macrocytic hyperchromic anemia: Larger than normal RBCs with more hemoglobin, usually due to vitamin B12 or folic acid deficiency.

Causes of Anemia

Acute blood loss (hemorrhagic anemia).
Bone marrow depression (aplastic anemia), such as that caused from exposure to radiation or certain medications.
Excessive breakdown of RBCs (hemolytic anemia), such as from infections, chemicals, incompatible blood transfusions or snake venom.

Blood Grouping

Importance: Prior to blood transfusion, blood grouping and cross matching is essential.
Principle: Red blood cells (RBCs) have antigens (agglutinogens) attached to their membrane and the plasma contains antibodies (agglutinins) to recognize these antigens.
The antibodies and antigen reaction determines the blood type (O, A, B or AB).
Anti-A
Anti-B
Anti-D

Rh Factor

An antigen on RBCs, presence of Rh antigens on cells designates a person as Rh-positive.
Absence of Rh antigens on cells means a person is Rh-negative.
Rh incompatibility can result from a Rh-negative mother carrying an Rh-positive fetus. This condition is called erythroblastosis foetalis where the mother's antibodies attack the fetal RBCs.

Blood Transfusion

Indications: Restore whole blood lost in hemorrhage, replace a specific component (e.g., RBCs, platelets), or treat erythroblastosis foetalis.
Precautions: Blood must be compatible between donor and recipient using cross matching. Recipient must be Rh-negative or receiving Rh- negative blood. Must be free from bloodborne diseases and contamination and good quality with sufficient hemoglobin (Hb).

Complications of Blood Transfusion

Agglutination: Blocks capillaries producing backache, joint, and angina pain if coronary arteries occluded.
Hemolysis: Rupture of RBCs causing hemoglobin increase resulting in blood viscosity increase which is then associated with heart failure, jaundice, renal failure and hypoxia. Other toxic substances such as histamine may also be released causing vasodilation, hypotension, and shock.
Physical (overload): Excessive transfusion.
Infective: Infectious hepatitis, AIDS, malaria, others.
Mechanical: Air embolism.

Hemostasis

Definition: Stoppage of bleeding from injured blood vessels. This involves the assessment of vascular spasm and platelet function in the first and second stages of hemostasis.
Materials for the bleeding time experiment: Lancets, a stopwatch, cotton swabs, alcohol and filter paper.
Normal bleeding time = 1 to 3 minutes. Prolonged bleeding time may indicate a coagulation disorder.
Purpura: Purple colored spots appear on the skin or mucous membranes.

Coagulation Time

Definition: Time needed for a blood clot to form, involving stages after vascular spasm and platelet function to the intrinsic coagulation pathways to form a fibrin clot.
Materials: Used in this experiment are lancets, a stop watch, cotton swaps, alcohol wipes, and a non-heparinized capillary tube.
Normal coagulation time = 3–9 minutes. Prolonged clotting time may indicate a deficiency of clotting factors like vitamin K or clotting factors VIII, IX, or XI.

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Description

This quiz focuses on the principles of neuromuscular transmission and muscle contraction, specifically through experiments with the sciatic-gastrocnemius preparation. It covers the process of action potentials, neurotransmitter release, and the phases of a simple muscle twitch. Test your understanding of these fundamental physiological concepts.