Lecture 6

Question 1

5 differences between the adaptations to aerobic and high intensity exercise?

Answer 1

Increased oxidative capacity vs. Decreased oxidative capacity

Some IIx (fast glycolytic fibres) can be converted to fast oxidative fibers vs.
Some IIa (fast oxidative fibres) can be converted to fast glycolytic fibers

Increase in size and number of mitochondria vs. Decrease in size and number of
mitochondria

Decrease in fibre diameter vs. Increase in fibre diameter

Increase in number of capillaries surrounding muscle fibres vs.Reduced resistance to fatigue

Question 2

What is the recruitment order of muscle fiber types? Are all muscles the same type in a motor unit?

Answer 2

Recruitment order:

1. Type I
2. Type IIa
3. Type IIx

– In a single motor unit, all muscle fibres are of the same type

Question 3

What are the 4 factors in the generation of force?

Answer 3

• Number of motor units activated
• Frequency of stimulation
• Muscle fibre and sarcomere length
• Speed of Contraction

Question 4

What is asynchronous motor unit summation?

Answer 4

• During a sustained tetanic contraction, motor units are activated on a rotating basis

Question 5

What is tetanic contraction?

Answer 5

Tetanic contraction is a sustained muscle contraction evoked when the motor nerve that innervates a skeletal muscle emits action potentials at a very high rate

Question 6

What is the ideal length for muscle/sarcomere length to generate force in micro meters?

Answer 6

2-2.5 micrometers

Question 7

How can you tell if a muscle has dystrophy by looking at it?

Answer 7

-More white tissue as compared to normal
•Affected muscles infiltrated by fat and connective tissue
-Numerous genetic loci
-Proteins localized in the nucleus, cytosol, cytoskeleton, sarcolemma, and
extracellular matrix.

Question 8

What is neurophysiology?

Answer 8

• The “message” for a muscle contraction is carried from the brain to the target body region in what seems to be an instant
• The message is transmitted by neurons (nerve cells)
• A group of nerves bundled together constitute a nerve
• A nerve impulse—an electrical charge—is the signal that passes from one neuron to the next and finally to an end organ, such as a group of muscle fibers, or back to the CNS

Question 9

What are the 3 inputs and outputs that comes from the peripheral nervous system?

Answer 9

Inputs(afferent):

Somatic senses-Skin, muscles, joints
Special senses-Vision, hearing, smell, taste etc.
Visceral senses-Internal envir. (fullness, Blood Pressure, etc.)

Outputs(efferent):

(somatic) Skeletal muscle
(autonomic) Sympathetic-Cardiac muscle, Smooth muscle, Glands
(autonomic) Parasympathetic-Gastrointestinal tract

Question 10

What are the 3 main components of the nervous system?

Answer 10

• Central Nervous System
• Sensory Receptors and Afferent Neurons
• Motor Function and Efferent Neurons

Question 11

What is the purpose of neurons? What are 3 universal properties of neurons?

Answer 11

Transmit action potentials by propagation

• Universal Properties:
– Excitability (irritability)
• Respond to environmental changes called stimuli

– Conductivity
• Neurons respond to stimuli by producing electrical signals that are quickly conducted to other cells at distant locations

– Secretion
• When electrical signal reaches end of nerve fibre, a chemical neurotransmitter is secreted that crosses the gap and stimulates the next cell

Question 12

What are the 3 classes of neurons?

Answer 12

Sensory (afferent)neurons conduct signals from receptors
to the CNS.

Inter neurons(association neurons) are confined to the CNS.

3 Motor (efferent) neurons conduct signals from the CNS to effectors such as
muscles and glands

Question 13

What is the definition of action potential? What is the 3 step process of an action potential?

Answer 13

• the all-or-nothing electrical impulse used to communicate information between neurons and from neurons to muscle fibres.
• An action potential is a brief reversal of charge that moves along a nerve axon
• This is a change from the resting membrane potential
• The ions primarily responsible for membrane polarity in neurons are potassium (K+) and sodium (Na+)

Question 14

What is the value for normal resting membrane potential in mV? What are the 3 important for determining resting membrane potential?

Answer 14

• Resting Membrane Potential = -70 to -90
mV (can say the cell/neuron is polarized)

• Concentration gradients of Na+ and K+
• Permeability of membrane for Na+ and K+
• Contribution of the Na+- K+ pump

Question 15

What are 4 examples of things that stimulate neurons? What does the stimulation of a neuron cause?

Answer 15

• Stimulation of a neuron causes local disturbances to this resting membrane potential
– Chemicals (ligands), light, voltage, heat, etc

• Causes the opening or closing of gated channels (Na+, K+)changes membrane potential (depolarizes)
– This depolarization of the plasma membrane will either cause a local potential or action potential

Question 16

What are local potentials? how are they different from action potentials?

Answer 16

• Voltage-gated channels on the dendrites and soma open
• Na+ diffuses for short distance on the inside of the plasma membrane producing a current that travels toward the cell’s trigger zone; this short-range change in voltage is called a local potential

• Different from action potentials because: graded, decremental, reversible, excitatory or inhibitory

Question 17

How does the typical local potential process occur?

Answer 17

Typically (but with exceptions), the response begins at the dendrite, spreads through the soma, travels down the axon, and ends at the synaptic knobs (synapse) then may cause the release of neurotransmitters etc.

Question 18

How are action potentials different than local potentials?

Answer 18

• More dramatic change produced by voltage-gated channels on the trigger zone and axon
– If excitatory local potential spreads all the way to the trigger zone and is still strong enough when it arrives, it can open these gates and generate an action potential

Question 19

What are myelinated fibers? What is saltatory conduction?

Answer 19

• Voltage-gated channels needed for APs
• Fast Na+ diffusion occurs between nodes

• Saltatory conduction —nerve signal seems to jump
from node to node

Question 20

What is the physiological process going on with multiple sclerosis?

Answer 20

• Immune system attacks the myelin sheath

* Nerve Impulses traveling along nerves are interrupted or distorted

Question 21

What are the 2 ways that synapses act as junctions?

Answer 21

• Junction between either:

1. Axon and Dendrite
2. Axon and Effector
   – Muscle
   – Heart
   – Other Organ

Question 22

What happens at the chemical synapse? What is the difference at the membrane called?

Answer 22

• Neurotransmitters are released when AP reaches the terminal end of the axon
• Neurotransmitters flood synapse and bind to post-synaptic cell
• Post-synaptic cell function is altered

the difference at the membrane is called the postsynaptic potential

Question 23

What are the 5 steps of neurotransmitter release?

Answer 23

1. An action potential depolarizes the axon terminal
2. The depolarization opens voltage-gated Ca2+ channels and Ca2+ enters the cell
3. Calcium entry triggers exocytosis of synaptic vesicle contents
4. Neurotransmitter diffuses across the synaptic cleft and binds with receptors on the postsynaptic cell.
5. Neurotransmitter binding initiates a response in the postsynaptic cell.

Question 24

What are the 9 steps of action potential?

Answer 24

1. resting membrane potential
2. Depolarizing stimulus
3. Membrane depolarizes to threshold. Voltage gated Na+ channels open and Na+ enters cell. Voltage gated K+ channels begin to open slowly.
4. Rapid Na+ entry depolarizes cell
5. Na+ channels clse and slower K+ channels open.
6. K+ moves from cell to extracellular fluid
7. K+ channels open and additional K+ leaves cell, hyperpolarizing it
8. Voltage gated K+ channels close, less K+ leaks out of the cell
9. Cell returns to resting ion permeability and resting membrane potential.

Question 25

What are the 3 common neurotransmitters for human movement? What are NE and Epi important for?

Answer 25

• ACh – Acetylcholine: action potentials in muscle cells
• NE – Norepinephrine:
• Epi – Epinephrine:

Important for control of Heart rate and vascular resistance

Question 26

What are the basic steps of receptor mediated signalling?

Answer 26

Signalling Molecule - Receptor Protein - Intracellular Signal - Molecules - Target Protein(s) -Response

Question 27

What are the post-synaptic actions of neurotransmitters?

Answer 27

1. Alter ion channels

• Excitatory Neuron: Na+ channels open, cell depolarizes, AP
• Inhibitory Neuron: Cl channels open, cell hyperpolarizes, AP much less likely

Question 28

What are the 3 steps of spatial summation?

Answer 28

• Spatial summation is the net sum of both excitatory and inhibitory synapses
• When enough of a change is generated an action potential will be triggered

1. Three excitatory neurons fire. Their graded potentials separately are all below threshold.
2. Graded potentials arrive at trigger zone together and sum to create a suprathreshold signal
3. An action potential is generated.

Question 29

What is temporal summation?

Answer 29

• An action potential can also be triggered by frequent, close together firing of synapses
• When firings are far apart membrane potential recovers between
• When firings are close together they can SUM to elicit an action potential

Question 30

What is neural integration?

Answer 30

• It requires more than 1 synapse “firing” to cause enough of a local potential to generate an AP– Spatial and temporal summation