Lecture 14 Exercise And Reflexes Flashcards
Aerobic or anaerobic?
Short duration high intensity:
6 sec - ATP stored in muscle used first
10 sec - ATP formed from creatine phosphate and ADP (direct phosphorylation)
30-40secs to end of exercise - glycogen stored in muscle broken down to glucose which is oxidised to generate ATP (anaerobic pathway)
Prolonged duration
Hours - ATP is generated by breakdown of several nutrient energy fuels by anaerobic pathway.
Physiological response to dynamic voluntary exercise
CNS
Regulates physiological response by somatic and automatic systems. Cerebral blood flow and O2 supply well maintained
Metabolism
Increased liver glucose output mostly by glycogenolysis but also gluconeogenesis
Increased adipose tissue lipolysis & free fatty acid (FFA) mobilisation
Skin
Increased sweat rate for heat dissipation (max. ~2-3l per hr)
Major effects on fluid homeostasis, cardiovascular function temp regulation and metabolism
Oxygen transport
Increase in whole body uptake of O2 (max~7l/minute or 80-90ml/kg/min in elite athletes)
Increased heart rate (max~200bpm) & cardiac output (max ~200bpm)
Increased ventilation (max~200l/min)
Arterial PO2 and hemoglobin well maintained
Skeletal muscle
Increased ATP turnover
Increased glycogenolysis, glucose uptake, lipolysis and FFA uptake
Increased O2 utilisation, CO2 and heat production
Increased blood flow, capillary recruitment release of biologically active molecules (“myokines”) with autocrine paracrine and endocrine effects
Training causes beneficial changes: systemic effects
Systemic
Skeletal- hypertrophy, hyperplasia, fibre type switch
Vascular- increased flow, vasoreactivity and angiogenesis
Metabolism - increased insulin sensitivity, oxidative phosphorylation, mito. biogenesis and adipose “browning”
Training causes beneficial changes: cardiac
Growth- hypertrophy,hyperplasia
Cardioprotection reduced ischemic injury
Function - increased stroke volume & cardiac output, improved Ca2+ handling and T tubule organisation
Metabolism - increased oxidative phosphorylation and mito. Biogenesis
Vascular - increased flow, vaso reactivity and angiogenesis
Exercise and cardiac muscle
The “trained” heart - adult hearts show plasticity. Trained hearts weigh more and have larger ventricles
Pathological hypertrophy - change in size due to physiological problem e.g. vol/pressure overload, valve insufficiency, stenosis and hypertension
Dangers of steroids
Stunted growth
Hair changes
Hypogonadism
Roid rage
Increased blood pressure
Increased LDL- cholesterol
Increased risk of heart attack/stroke
Death
Muscle pathology examples
Myasthenia gravis
- autoimmune condition, chronic progressive damage of NMJ
Muscular dystrophy
- group of inherited conditions: degeneration of skeletal muscle fibres
Natural wear and tear
Injury
Age
Muscle pathology: Adult onset autoimmune response
Abnormal thymus
Produces abnormal myoid cells of thymus with ACh receptors
T cells and B cells recognise abnormal myoid cells as defective or foreign and destroy them
These cells have mistaken ACh receptors as the foreign entity. ACh receptors are now recognised as foreign
The body launches a full autoimmune response on its own healthy ACh receptors
Muscles reflexes
Reflex - an involuntary/automatic action your body does in response to a stimulus
Protective e.g. pull hand away from hot flame
Stretch e.g. stretch reflex-patellar tendon “knee jerk” reflex - a monosynaptic myotatic spinal reflex
Reflex arc
Reflex arc consists of:
- a receptor, a sensory neuron that transmits impulse to spinal cord
-integration centre
- a motor neuron that transmits nerve impulse from spinal cord to peripheral region
- an effector, muscle that recieves impulse from the motor neuron
Patellae reflex
1) tap patellae tendon
2)muscle stretches
3)nerve signal to spinal cord
4) impulse crosses synapse
5) impulse travels via efferent nerve to the muscle
6) muscle contracts
7) leg extends
monosynaptic reflex - only one synapse involved - does not involve brain
Polysynaptic reflexes involve 2 or more synapses
