Physiology- Nerve and Muscle Flashcards
Structure of a nerve
Whole nerve to Fascicle to Cells to Axons
What is depolarisation?
When the cell becomes more positive
What is repolarisation?
When the cell returns to RMP
What is the RMP?
-70mV
What are important neural communications?
Neuron to Neuron & Neuron to Muscle
Main subtypes of muscle
Cardiac, Smooth and Skeletal. Only skeletal is under voluntary control.
What is a neuro-skeletal motor unit and wherein the spinal cord are they found?
Comprised of motor neuron and muscle fibres. Motor neurons are found in the anterior part of the spinal cord.
Why do we need skeletal muscle?
For movement, posture and thermoregulation
Structure of a muscle fibre
Whole muscle (bundle of fascicles) to Single fascicle (Bundle of fibres) to Cells (myofibres) to Myofibrils to Myofilaments
Structure of skeletal muscle?
Sarcolemma surrounds the myofibre
The sarcomere is made of filaments
T-tubules are extensions of the sarcolemma that dive deep into the muscle
What is and what is the structure of the sarcomere?
The sarcomere is the contractile unit of the muscle.
Actin is the thin filament, myosin is the thick filament.
T tubules and the sarcoplasmic reticulum are located close to the sarcomere
Steps of an action potential
RMP, Depolarisation, Repolarisation and Hyperpolarisation
What is the refractory period?
Is when a neuron is unable to generate an AP, the Na+ VIGC is either already opened or closing
What is an electrical gradient?
Opposites attract, ions will move down a concentration gradient.
From an area of more positives to less
What is a chemical gradient?
Na+ and K+ ions are important in our cells. Ions will move down an area of high concentration to low concentration.
What is voltage?
Voltage is the difference in charge across the membrane
What is a voltage-gated ion channel? (VGIC)
These are the channels that ions require to cross the membrane, they open at certain voltages.
What charge does a Na+ VGIC open at?
Opens at -60mV
What charge does the K+ VGIC open at?
Opens at +30mV
What is the role of the axon hillock?
Summates the local (graded) potentials to generate action potentials. If the voltage reaches the -60mV threshold, an AP will occur.
What is myelin?
Myelin is made from specialised cells called Schwann cells and it increases the speed of an AP
What is the input zone of the neuron called?
The dendrite
What is the output zone called?
Synaptic terminal
Describe what happens to the cell during depolarisation
Na+ VIGC open to allow Na+ to enter the cell, raising membrane potential to reach +30mV
Describe what happens to the cell during repolarisation
K+ VIGC open to allow K+ to leave the cell to return the MP to -70mV. Na+ VIGC is closed
What is an excitatory potential
When Na+ enters the neuron to bring the MP closer to the threshold
What is an inhibitor potential
Na+ leaving the cell moves MP away from the threshold
What are the two types of isotonic contractions?
Eccentric (Muscle lengthening) & Concentric (Shortening
Describe an isometric contraction
When the muscle remains muscle the same length while developing tension
What energy is used in the first 6 secs of exercise
Stored ATP
What energy is used in the 10-30 secs of exercise
Creatine phosphate- CP shuttle. Provides fast but little ATP
What energy is used in the 30-60 secs of exercise
Anaerobic system- Doesn’t require oxygen, Glycogen is broken down to glucose. Produces 2 ATP and lactic acid
What energy is used in 60 secs + of exercise
Aerobic system- Requires oxygen, glucose and fatty acids combine with oxygen to form 32 ATP in the mitochondria
Describe white muscle fibres
Type-IIB, fast-twitch fibre, small resistance to fatigue, high force generation, low # of mitochondria
Describe red muscle fibres
Type A, Slow twitch, high resistance to fatigue, low force generation, a high number of mitochondria
Describe cross-bridge cycle
Ca2+ binds to actin uncovering binding site.
Myosin head binds to actin forming cross bridge
Causes sarcomere to shorten
