edu2exp exercise & performance neural, muscular and endocrine influences and adaptations to...
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EDU2EXP Exercise & Performance
Neural, Muscular and Endocrine influences and adaptations to
exercise
EDU2EXP Exercise & Performance
Reasons to study
• Cheating not tolerated 0• Will help you understand the remainder of
course materials• Won’t have as much catching up to do for
final exam
All students must pass all pieces of assessment in order to pass the
subject
EDU2EXP Exercise & Performance
Muscular Systems
Chapter 1- p 26-45
Chapter 9- 204-218
Pages are wrong in unit outline
EDU2EXP Exercise & Performance
EDU2EXP Exercise & Performance
contractual elements • An I-band (light zone)• An A-band (dark
zone)• An H-zone (in the
middle of the A-band)• An M-line in the
middle of the H-zone• The rest of the A-
band• A second I band
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Action Potential1. A motor neuron releases acetylcholine (ACh) at
the neuromuscular junction2. ACh binds to receptors on the sarcolemma3. If enough ACh binds to receptors, an action
potential is transmitted the full length of the muscle fiber
4. The action potential triggers the release of Ca2+
from the sarcoplasmic reticulum5. Ca2+ binds to troponin on the actin filament, and
the troponin pulls tropomyosin off the active sites, allowing myosin heads to attach to the actin filament
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Muscle contraction- Sliding filament theory
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EDU2EXP Exercise & Performance
Muscle fibre types
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Single Muscle Fiber Physiology
• Peak power is different between muscle fiber types
• All fiber types tend to reach their peak power at ~20% peak force
• Endurance training, strength training, and muscular inactivity may cause a shift in myosin isoforms– Exercise training ↓ type IIx and ↑
type IIa
• Aging may shift the relative distribution of type I and type II fibers – ↓ type II and ↑ type I
EDU2EXP Exercise & Performance
EDU2EXP Exercise & Performance
Receptors
• Chemoreceptors- carry messages about O2 and Co2 concentrations, muscle pH, potassium
• Sensory feedback– Golgi tendon organs- give CNS feedback
about tension developed in the muscle– Muscle spindles give feedback about length of
the muscle
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Muscle spindles- length detector
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Adaptations
• Neural gains
• Muscle fiber hypertrophy- increase in size
• Muscle fiber hyperplasia- increase in number
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Hypertrophy• 2 main types
• Transient- during and immediately after
• Chronic– Sarcoplasmic hypertrophy– Myofibrillar hypertrophy-
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Myofibrillar Hypertrophy
• Increased size/amounts of– Contractile proteins-
Actin & Myosin– Myofibrals per muscle
fibre– Connective tissue-
ligaments etc– Enzymes & stored
nutrients– mitochondria
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Microscopic Views of Muscle Cross Sections Before and After Training
Photos courtesy of Dr. Michael Deschene's laboratory.
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Role of testosterone
• Acute increases after maximal exercise
• Anabolic effect• Induces
hypertrophy• No relationship
between total hypertrophy and testosterone
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Atrophy
• Muscle degeneration from disuse– Not synthesising new proteins– May be used as fuel
• Begins after 6 hours immobilisation
• Strength decreases of 3 to 4% per day
• More apparent with complete inactivity (bed rest)
• Effects are reversible
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Age related changes
• Sarcopenia– Slow phase- 10% loss from 25-50– Rapid phase- Extra 40% loss 50-80 years – Therefore by 80, 50% muscle lost
• Predominant loss of fast fibres slow ones
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Variability in adaptation
• Individual training responsiveness
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Genetics
• Myostatin- gene that inhibits muscle growth
• Therefore when this gene is inactive- extraordinary muscle growth occurs
• Some babies born with 1/ both myostatin genes inactive
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Belgian Blue cattle
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Muscle soreness• Acute• minutes or hours after exercise • from accumulation of the end
products of exercise in the muscles or edema
• Delayed• 12 to 48 hours after a strenuous
bout of exercise• from eccentric muscle activity • Is associated with:–Structural damage– Impaired calcium homeostasis
leading to necrosis–Accumulation of irritants– Increased macrophage activity
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Delayed OnsetMuscle
soreness
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Muscle summary
• Muscle structure and function
• Muscle fibre types and adaptations
• Sliding filament theory
• Sensory – Muscle spindles– Golgi tendon organs
• Physiology of hypertrophy
• DOMS
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Neural
Ch 3 pg 80-97
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Neuromotor System Organization
Neuromotor System Organization
• Central nervous system (CNS)– Includes the brain
and spinal cord
• Peripheral nervous system (PNS) – Is comprised of
cranial and spinal nerves
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Neurotransmitters of the BrainNeurotransmitters of the Brain
• Neurotransmitters- chemical messengers
• Synapse= gap between nerves
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Neuron Classifications
Neuron Classifications• Motor (efferent) neurons
– Supply extrafusal and intrafusal skeletal muscle fibers
• Sensory (afferent) neurons – Transmit sensory information from peripheral sensory
receptors to the brain
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Afferent
Efferent
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Reflexes• Sensory input• Transmission of
impulses to spinal cord via sensory root (afferent)
• Causes muscle fibres to contract
• (efferent)
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Autonomic Nervous System (ANS)
Autonomic Nervous System (ANS)
• Innervates smooth muscle (involuntary muscle) in the intestines, sweat and salivary glands, myocardium, and some endocrine glands
• Has two distinct divisions– Sympathetic – Parasympathetic
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Sympathetic Nervous SystemSympathetic Nervous System• Sympathetic neurons
– Exit the spinal cord and enter a series of ganglia (sympathetic chain) near the cord
– Release norepinephrine
• Activated during flight-or-fight situations– Accelerates breathing and
heart rate – Dilates pupils– Helps redistribute blood flow
from the skin to deeper tissues in anticipation of a perceived challenge
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Neural Summary
• Generalised structure and function
• Reflex arcs
• ANS- Para and sympathetic
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Endocrine
Chapter 2 page 59-76
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Hormones
• Steroidal
• Non steroidal
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Steroidal– Formed from cholesterol– Lipid soluble– Therefore can easily
cross cell membrane wallsTo cell receptors inside cell
cytoplasm/nucleus
– Examples• Adrenal cortex (cortisol and aldosterone)• Ovaries (estrogen and progesterone)• Testes (testosterone)• Placenta (estrogen and progesterone)
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Nonsteroidal– Protein or peptide and
amino acid-derived– Not lipid solublecan’t cross cell
membranes– Triggers a series of
intracellular events through outside recepters
• Activates cellular enzymes
• Changes membrane permeability
• Promotes protein synthesis
• Changes cellular metabolism
• Stimulates cellular secretions
Examples-Thyroid gland - Adrenal medulla (epinephrine and norepinephrine)
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Hormones of the PancreasHormones of the Pancreas
• Insulin– Regulates glucose metabolism – Released in response to hyperglycemia– Facilitates glycogenesis (glucose glycogen)
• Glucagon– Stimulates glycogenolysis – to release glycogen blood glucose to prevent
hypoglycemia
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EDU2EXP Exercise & Performance
INSULIN-
Controller of blood glucose levels
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Thyroid hormones• Major endocrine gland• Regulates metabolism• Secretes non steroidal hormones
– Increased protein synthesis– Increased mitochondria
• Failure to secrete thyroid hormones = hypothyroidism. Too much thyroid hormone = hyperthyroidism
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Hormones of the Adrenal Medulla
Hormones of the Adrenal Medulla
• Catecholamines• Epinephrine (Adrenaline) (80%)• Norepinephrine (20%)
– Released during fight or flight response– Increase heart rate, contractility, and blood pressure
– Rate of secretion is strongly influenced by exercise intensity
• Epinephrine increases after 50% vo2 max• Norepinephrine increases after 60-70% vo2 max
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EDU2EXP Exercise & Performance
Cortisol
• “stress hormone”
• Important for fat and glucose metabolism regulation– Increases mobilisation of FFA’s utilise for
energy– Spare blood glucose and save for brain
• Decreased immune function
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Regulation of Glucose Metabolism During Exercise
Glucose concentration during exercise is a balance between glucose uptake by the exercising muscles and its release by the liver– ↑ Glucagon: promotes liver glycogen
breakdown and glucose formation from amino acids
– ↑ Epinephrine: promotes glycogenolysis– ↑ Norephinephrine: promotes glycogenolysis– ↑ Cortisol: promotes protein catabolism
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Changes in Plasma Concentrations of Epinephrine, Norepinephrine, Glucagon,
Cortisol and Glucose During 3 h of Cycling at 65% of VO2max
.
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Mechanism by which ADH Conserves Body Water
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Endocrine Summary
• Steroidal/Non steroidal hormones• Thyroid hormones• Pancreatic hormones:
– Insulin & Glucagon
• Adrenal Hormones– Epinepherine– Norepinepherine– CortisolAnd their roles during exercise