edu2exp exercise & performance neural, muscular and endocrine influences and adaptations to...

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

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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

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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