Neuromuscular system physiology

Question 1

what are exteroreceptors? (3), and where they are found (3)

Answer 1

• sensory receptors
• detect stimuli external to body
• e.g. touch, pressure, temperature
• found on skin, nose, tounge

Question 2

what are enteroreceptors? (2), and where they are found (2)

Answer 2

• sensory receptors
• that detect internal stimuli within the body
• found in glands and smooth muscle

Question 3

what are proprioceptors (2), and where they are found (3)?

Answer 3

• sensory receptors
• detect position, movement and orientation of body
• found in skeletal muscle, tendons, & joints

Question 4

what does the NMJ essentially do?

Answer 4

connection between axonal efferent and muscle fibre

Question 5

what is the neurotransmitter released across NMJ’s?

Answer 5

acetylcholine

Question 6

what does acetylcholine bind to on the muscle cell surface membrane?

Answer 6

nicotinic Ach receptors

Question 7

what electrical gradient indirectly causes contraction of muscle (2)

Answer 7

• depolarisation
• causes Ca2+ influx

Question 8

how does depolarisation occur in skeletal muscle? (4)

Answer 8

• acetylcholine receptors bind to Ach
• allows Na+ to enter muscle cell
• triggers further voltage-activated Na+ channels to open
• Massive iflux in NA+ causes depolarisation of skeletal muscle

Question 9

what causes Ach infused vesicles to fuse with plasma membrane? (2)

Answer 9

• action potential-driven depolarization
• Ca2+ influx to presynapse

Question 10

how are body movements classified?

Answer 10

• the type of neuronal control

Question 11

which is higher order and why: postural reflex movements or autonomic reflexes?

Answer 11

Postural reflex movements:
* involves midbrain as well as spinal cord

Question 12

what nerve transmits information about head movement to the vestibular nuclei?

Answer 12

the 8th cranial nerve

Question 13

at what age do babies establish basic postural reflexes?

Answer 13

6-7 months

Question 14

what particular function of the Basal ganglia is impaired in Parkinsons’s disease?

Answer 14

• scaling of motor output

Question 15

is there any direct projections from the Basal ganglia to the Spinal cod?

Answer 15

no

Question 16

is there direct sensory input from the periphery to the basal ganglia?

Answer 16

no

Question 17

what 3 main disorders can occur due to disfunction of the basal ganglia?

Answer 17

1. parkinson’s isease
2. huntington’s disease
3. dystonia

Question 18

what is a cortical pathway?

Answer 18

• refers to a neural pathway within the cerebral cortex

Question 19

what is the cerebral cortex?

Answer 19

• outer layer of the brain
• responsible for higher cognitive functions such as perception, decision-making and voluntary movement

Question 20

what are the ipsilateral white columns? (2)

Answer 20

• part of the spinal cords white matter
• responsible for transmitting sensory information from same side of body to brain

Question 21

what does the somatosensory cortex do?

Answer 21

allows you to sense movement of the body

Question 22

what are the 3 anatomical levels in the nervous sytem that control voluntary movement?

Answer 22

• cerebrum - cortex, basal ganglia
• cerebellum - motor patterns, refinement, execution
• ** brain stem & midbrain** - relay systms of higher brain regions

Question 23

what is the mass of skeletal muscle relative to the whole body in men and women?

Answer 23

men- 40%
women - 30%

Question 24

how is acetylcholine removal from the synaptic cleft?

Answer 24

acetylcholinesterase

Question 25

how does DHPR cause Ca2+ release?

Answer 25

• not entirely known
• thought to be through protein-protein interaction
• this idea comes from the speed of the process as its so quick

Question 26

what is calsequestrin? (2)

Answer 26

• a protein that binds to calcium
• allows lots of calcium to be stored in the SR

Question 27

what is Rigor mortis, and how does it occur?

Answer 27

• post-death phenomon characterized by stiffening of muscles
• occurs due to depletion of ATP

Question 28

the percentage of ATP used in different aspects of muscle contraction?

Answer 28

• myosin ATPase - 60%
• Ca2+ ATPase - 30%
• Na-K ATPase - 10%

Question 29

what does the turnover rate of ATP mean?

Answer 29

• the rate at which ATP are synthesized and hydrolysed within a biological system
• Resting turnover rate - 1 minute
• increase 10-100 fold during exercise

Question 30

how do skinned muscle fibre cells stay intact?

Answer 30

• unlike most cells, skeletal muscle cells have a very strong organised structure
• allows for structure to stay intact even when the plasma membrane is removed

Question 31

why would it be fatal if ATP levels depleted in intesnse exercise?

Answer 31

• calcium stores would become depleted
• calcium levels could increase so much that sustained contraction of the muscle cell occurs
• equivalent to a cell undergoing necrosis

Question 32

what is anoxia?

Answer 32

when something is in a state of no oxygen

Question 33

What is the reason why phosphate effects muscle contraction, force and sensitivity to Ca2+ (2)

Answer 33

• power stroke generation in cross bridge cycle
• higher concentration of phosphate slows down the kinetics of the phosphate release from ADP during this stage

Question 34

what types of remodelling occur in response to intense exercise?

Answer 34

• innervation
• blood flow
• extracellular matrix

Question 35

what is succinate? (4)

Answer 35

• a dicarboxylic acid
• involved in the kreb cycle
• undergoes oxygenation in Kreb cycle to fumarate
• leads to production of ATP through oxidative phosphorlyation