muscle excitation

Question 1

skeletal muscle

Answer 1

-long cylindrical cells
- many nuclei per cell
- striated: has tiny bands that run across the muscle cell
- voluntary
-rapid contractions

Question 2

cardiac muscle

Answer 2

-branching cells
- one or two nuclei per cell
- striated
- involuntary
-medium speed contractions

Question 3

smooth muscle

Answer 3

• fusiform cells
  -one nucleus per cell
  -nonstriated
  -involuntary
  -slow, wave-like contractions
• found in hollow organs

Question 4

electrical disequilibrium

Answer 4

• the body is in a state of electrical disequilibrium because active transport of oils across the cell membrane creates an electrical gradient
• although the body is electrically neutral, cells have excess negative ions on the inside and their matching positive ions are found on the outside.

Question 5

electrochemical gradient

Answer 5

• the inout of energy to transport ions across a membrane has created an electrical gradient
• the active transport of positive ions out of the cell has created a chemical gradient. The combination of an electrical gradient is called an electrochemical gradient
• the cell remains in osmotic equilibrium, physiological measurements are carried out on a relative scale

Question 6

cell membrane

Answer 6

• the -ve ions will try and move down the electrical gradient and follow the +ve ion out of the cell, but the membrane inhibits its flow as its a good insulator
• prevents the movements of separate charges

Question 7

resting membrane potential

Answer 7

• electrical gradient across the cell membrane
• resting: membrane potential has reached a steady state and is not changing
• potential: electrical gradient created by active transport of ions is a source of stored or potential trial energy

Question 8

potassium ions and resting membrane potential

Answer 8

• potassium ion leak out of cell down its concentration gradient.
• excess -ve charge build up in side the cell as Pr negative cannot cross the membrane. An electrical gradient is formed
• -ve charges attract K+ ions back into the cell down the electrical gradient.
• net movement of k+ stops. the membrane potential at which the electrical gradient opposes the chemical gradient is known as the equilibrium potential

Question 9

neuromuscular junctions

Answer 9

The nerve impulse reaches the neuromuscular junction (myoneural junction).
- acetylcholine is released from the motor neuron
- acetylcholine binds with receptors in the muscles membrane to allow sodium ions to enter the muscle.

Question 10

excitation of muscles steps

Answer 10

• nerve impulse reaches neuromuscular junction
• acetylcholine is reached from motor neuron
• acetylcholine binds with receptors in the muscles membrane to allow sodium to enter
• sodium influx will generate an action potential in the sarcolemma
• action potential down T tubule
• sarcoplasmic reticulum releases calcium
• calcium binds with troponin to move the troponin, tropomyosin complex
• binding sites in the actin filament are exposed

Question 11

motor unit

Answer 11

A motor unit is all the muscle cells controlled by one nerve cell.

Question 12

muscle tonus and tetany

Answer 12

muscle tonus
- tightness of a muscle, some fibres always contracted

tetany
- sustained contraction of a muscle, result of a rapid succession of nerve impulses

Question 13

refractory period

Answer 13

• brief period of time in which muscle cells will not respond to a stimulus