Physiology 🫁

Question 1

what are excitable tissues?

Answer 1

• Tissues which respond to adequate stimulation by an electrical response, Nerve and muscle tissues are the most excitable tissues in the body.

Nerve: Respond by action potential (Depolarization &repolarization).

Muscle: Respond by muscle contraction (contraction followed by relaxation i.e., SMT)

Question 2

What are the types of stimuli according to Strength?

Answer 2

1. Subminimal (subthreshold) stimuli
2. Minimal (threshold) stimulus
3. Superminimal (super-threshold) stimuli
4. Maximal stimulus
5. Super-maximal stimuli:

Question 3

Subminimal (subthreshold) stimuli

Answer 3

stimuli of low intensity which produce no response (even if applied for a very long time).

Question 4

Minimal (threshold) stimulus

Answer 4

is the weakest stimulus which produces a response.

Question 5

Superminimal (super-threshold) stimuli

Answer 5

Increasing the intensity of the stimulus gradually above the threshold value leads to gradual increase in the response till it becomes maximum

Question 6

Maximal stimulus

Answer 6

• the stimulus that produces a maximal response. When the stimulus reaches a certain value, the response becomes maximum and fixed i.e. there is no further increase in the response with greater intensities.

Question 7

Super-maximal stimuli

Answer 7

stimuli of greater intensities than the maximal stimulus. These stimuli produce the same response as the maximal stimulus.

Question 8

statement of all or none rule

Answer 8

The response either occurs maximally or it does not occur at all, provided that all other conditions remain constant.

*So, All subminimal stimuli do not produce response

*And, Minimal (threshold) stimulus produces a maximal response

*Further increase in the intensity of the stimuli (superminimal, maximal, supermaximal) do not produce any further increase in the response

Question 9

Is there any contradiction between gradation of skeletal muscle contraction and all or none role ?

Answer 9

NO, as All or non law is applied in the single nerve fiber or single muscle fiber while gradation is applied in the nerve trunk or the whole muscle.

Question 10

what is the definition of simple muscle twitch (SMT)?

Answer 10

A single contraction followed by relaxation due to simulation of skeletal muscle by single maximal stimulus .

Question 11

what are the phases of simple muscle twitch?

Answer 11

1. The latent phase
2. Contraction phase
3. Relaxation phase

Question 12

latent phase of simple muscle twitch

Answer 12

The interval from stimulus application until the muscle begins
to shorten.

Question 13

contraction phase of simple muscle twitch

Answer 13

The muscle fibers shorten

Question 14

relaxation phase of simple muscle twitch

Answer 14

The muscle return to its original length

Question 15

what are the factors affecting simple muscle twitch?

Answer 15

• Temperature
• fatigue
• Stimulus frequency

Question 16

how does warming affect simple muscle twitch?

Answer 16

• (by using a warm ringer’s solution) “30-40”
• Effect:
  1-Increase amplitude of SMT
  2-Decrease duration of all phases of SMT
• Causes:
  1.Temperature reduces muscle viscosity.
  2.Temperature activates muscle enzymes.

_________
- NB: Severe ≥ 42: Heat rigor

Question 17

how does cooling effect simple muscle twitch?

Answer 17

• (by using a cool ringer’s solution) “>20”
• Effect:
  1-decrease amplitude of SMT
  2-increase duration of all phases of SMT
• Causes:
  1. Temperature increases muscle viscosity.
  2. Temperature reduces muscle enzymes activity

Question 18

what are other types of Rigor?

Answer 18

• Ca rigor (arrest of heart in systole)
• Rigor mortis (stiffening of muscles after death due to Depletion of ATP)

Question 19

what is the definition of fatigue?

Answer 19

• It is a state of decreased muscular activity due to rapid repeated stimuli, the muscle may not show any response to stimuli.

Question 20

what are the manifestations of muscle fatigue?

Answer 20

1-Decrese amplitude of SMT
2-Increase duration of all phases of SMT
3- Contracture

Question 21

what is contracture?

Answer 21

a state of sustained weak muscle contraction followed by incomplete relaxation due to depletion of ATP which occurs when the muscle become extremely fatigued.

Question 22

effects of increased stimulus frequency

Answer 22

• Effects of stimulation with Very Low frequency
• Effects of stimulation with Low frequency
• Effects of stimulation with intermediate frequency
• Effects of stimulation with high frequency

Question 23

effects of stimulation of muscle with very low frequency

Answer 23

• Leads to separate twitches as this allows enough time for the muscle to complete relaxation.

Question 24

effects of stimulation of muscle with low frequency

Answer 24

Leads to separate twitches as this allows enough time for the muscle to complete relaxation, but staircase appears

Question 25

effects of stimulation of muscle with intermediate frequency

Answer 25

Leads to Clonus (incomplete tetanus) As the stimuli falls during the relaxation time.

Question 26

effects of stimulation of muscle with high frequency

Answer 26

Leads to tetanus. As the stimuli falls during the contraction time.

Question 27

what is the definition of staircase (treppe) phenomenon?

Answer 27

- When a muscle is stimulated with the maximal stimulus at a slow rate so that each stimulus occurs after the previous muscle twitch is complete, there is an increase in the height of each twitch until a constant height is reached after several twitches

Question 28

what is the cause of staircase (treppe) phenomenon?

Answer 28

- The cause of this phenomenon is that the 2nd stimulus finds the muscle in a better physiological condition (more warm and more Ca ++ ions are present inside the muscle fibers).

Question 29

where does staircase phenomenon occur?

Answer 29

Staircase phenomenon can occur with separate twitches, clonus and tetanus

Question 30

what is the definition of clonus (incomplete tetanus)?

Answer 30

- Repeated contractions of the muscle with incomplete relaxation. (If the frequency is increased, stimuli will fall during the relaxation phases of the previous twitches)

Question 31

what is the definition of tetanus?

Answer 31

- A continuous contraction without relaxation which results from fusion of successive contractions produced by the rapid successive stimulation due to persistent release of Ca++ ions which lead to continuous contractions. (With the frequency further increased, stimuli will fall during the contraction phases of the preceding twitch)

Question 32

what is the value of the tension developed during a complete tetanus?

Answer 32

The tension developed during a complete tetanus is about 4 times that developed by a simple muscle twitch.

Question 33

what is the frequency of Stimulation needed to produce tetanus?

Answer 33

The frequency of stimulation needed to produce tetanus is around 20-60 HZ for most skeletal muscles.

Question 34

Which is the commonest type of contraction in the human body stair case, clonus or tetanus ?

Answer 34

tetanus

Question 35

With low frequency stimuli, how can you produce tetanus ?

Answer 35

Increaseing the duration of SMT, may be by cooling

Question 36

what is the most commonly used stimuli in laboratory experiments? And why?

Answer 36

**Electrical stimuli as:** - their onset, duration and strength are easily controlled - similar to physiological process of excitation, - cause no or minimal tissue damage so, can be repeated.

Question 37

what are the apparatuses used to record muscle contraction?

Answer 37

- kymograph - Biopac

Question 38

what does each apparatus for recording of skeletal muscle response include?

Answer 38

- Organ bath for tissue - Rotating drum and pen for recording - Electrical stimulator

Question 39

what are the two types of electric currents that can be used in Physiological experiments?

Answer 39

**Galvanic current** - long duration - low amplitude **Faradic current** - short duration - high amplitude

Question 40

what controls the degree of muscle contraction?

Answer 40

1. Activating a desired number of motor units within the muscle. 2. Controlling the frequency of motor neuron impulses in each motor unit. - When an increased muscle contraction is necessary, the brain increases the number of simultaneously active motor unit within the muscle. This is known as "motor unit recruitment".

Question 41

what are the causes of delayed muscle fatigue inside the body?

Answer 41

**Cardiovascular system:** supplies the muscles with 02 and nutrients and removes the metabolites from the muscle. **CNS:** regulates the muscle contraction so that not all the muscle fibers are contracted at the same time, but instead, there is alternation between contracted and relaxed muscle fibers. **Hormones:** e.g. adrenaline, noradrenalin, cortisol, thyroxin and insulin. They delay onset fatigue by increasing the metabolic rate, glycogen stores, blood pressure and excitability of the nervous system

Question 42

what are the disadvantages of perfusion of tissues with pure water?

Answer 42

- Perfusion of tissues with pure water destroys the cells. - It draws from the cells important crystalloids - It also leads to rupture of the cell membrane duo to accumulation of water inside the cells.

Question 43

what are the solutions used instead of water?

Answer 43

- The following solutions (physiological saline, Tyrod's solution, Ranger's solution) are used instead of water for perfusion or for preventing the tissues from drying. - They are isotonic with the cells and they contain the essential crystalloids constituents in the same concentration as the plasma and tissue fluids.

Question 44

physiological saline

Answer 44

- 0.6% sodium chloride solution for frog's tissues. - 0.9% Sodium Chloride for mammalian tissue

Question 45

ringer's solution

Answer 45

- Ringer's solution typically contains NaCI, KCI, CaCl2 and NaHCO3 - Sometimes with other minerals such as MCI2, dissolved in distilled water. - The precise proportions of these vary from species to species

Question 46

Tyrode's solution

Answer 46

- It resembles lactated Ringer's solution, but contains magnesium, a sugar (usually glucose) as an energy source and uses bicarbonate and phosphate as a buffer instead of lactate. - It must be gassed with oxygen and carbon dioxide when used for cell culture applications and physiology