Topic 7 Flashcards
What attaches skeletal muscle to bones?
Tendons
What attaches bones to other bones?
Ligaments
What is an antagonistic pair?
Muscles that work together to move a bone
How does an arm bend?
Biceps contracts, triceps relax.
This pulls the bone so arm flexes (bends)
What is a flexor?
A muscle that bends a joint when contracts
How does an arm straighten?
Triceps contract, biceps relax.
This pulls the bone so arm extends (straightens)
What is an extensor?
A muscle that straightens a joint when contracts
What is skeletal muscle made up of?
Large bundles of long cells called muscle fibres
What is the cell membrane of muscle fibre cells called?
Sarcolemma
What are Transverse (T) tubules?
Parts of the Sarcolemma fold inwards across muscle fibre and stick into the sarcoplasm.
They help spread electrical impulses throughout the sarcoplasm so they reach all parts of the muscle fibre.
What is the sarcoplasmic reticulum?
A network of internal membranes that runs through the sarcoplasm.
It stores and releases calcium ions for muscle contraction.
What does multinucleate mean?
Contains many nuclei
What are myofibrils?
Long, cylindrical organelles.
Made up of proteins and are highly specialised for contraction.
What do myofibrils contain?
Thick myosin filaments and thin actin filaments
What are sarcomeres?
Short units in a myofibril
What is an A-band?
Dark bands that show up on an electron microscope as a result of the thick myosin filaments and some overlapping the thin actin filaments
What is an I-band?
Light bands that show up on an electron microscope as a result of the thin actin filaments
What is a Z-band?
The ends of each sarcomere are marked with Z-lines
What is the M-line?
The middle of each sarcomere, in the middle of the myosin filaments
What is the H-zone?
Around the M-line, contains only myosin filaments
How does a muscle contract?
Myosin and actin filaments slide over each other to make sarcomeres contract.
Myofilaments themselves don’t contract .
Myosin and actin molecules stay the same length.
Simultaneous contraction of lots of sarcomeres means myofibrils and muscle fibres contract.
Describe myosin filaments.
- Globular heads that are hinged so can move back and forth
- Each head has a binding site for actin and a binding site for ATP
Describe actin filaments.
- Binding sites for myosin heads called actin-myosin binding sites.
- Two other proteins called tropomyosin and troponin are found between filaments.
- These proteins are attached to each other and they help myofilaments move past each other
Describe the binding sites on myofilaments in a resting muscle.
- Actin-myosin binding site is blocked by tropomyosin, which is held in place by troponin
- Myofilaments can’t slide past each other because myosin heads can’t bind
Describe muscle contraction.
1) An action potential from a motor neurone stimulates a muscle cell and depolarises the sarcolemma.
2) Depolarisation spreads down the T-tubules to the sarcoplasmic reticulum
3) This causes sarcoplasmic reticulum to release stored calcium ions into the sarcoplasm.
4) Calcium ions bind to troponin, causing it to change shape which pulls the attached tropomyosin out of the actin-myosin binding site on the actin filament.
5) Binding site is now exposed so myosin head binds.
6) Bond formed when myosin head binds to actin filament called actin-myosin cross bridge.
7) Calcium ions also activate the enzyme ATPase which breaks down ATP into ADP and Pi to provide energy needed for muscle contraction.
8) Energy released from ATP moves myosin head which pulls the actin filament along in a rowing action.
9) ATP also provides energy to break the actin-myosin cross bridge so myosin head detaches from the actin after its moved.
10) Myosin head reattaches to different binding site further along the actin - new actin-myosin cross bridge is formed and cycle is repeated.
11) Many cross bridges form and break very rapidly pulling the actin filament along which shorten the sarcomere causing muscle contraction.
12) Cycle will continue as long as calcium ions are present and bound to troponin.
What causes muscle contraction to stop?
When excitation stops and the muscle stops being stimulated, calcium ions leave their binding sites on troponin molecules.
Calcium ions are moved by active transport back into the sarcoplasmic reticulum using ATP.
Troponin molecules return to their original shape, pulling the attached tropomyosin molecules with them so binding site is blocked.
Actin filaments slide back to their relaxed position which lengths the sarcomere.
Describe slow twitch muscle fibres.
1) Contract slowly
2) Good for endurance activities
3) Many mitochondria
4) Little sarcoplasmic reticulum
5) Low glycogen content
6) Numerous capillaries
7) Doesn’t fatigue quickly
8) Red (lots of myoglobin)
9) Aerobic respiration
Describe fast twitch muscle fibres.
1) White (little myoglobin)
2) Few mitochondria
3) Extensive sarcoplasmic reticulum
4) High glycogen content
5) Few capillaries
6) Fatigue quickly
7) Contract quickly
8) Anaerobic respiration
What are the reactions involved in aerobic respiration called?
Glycolysis
The link reaction
the Krebs cycle
Oxidative phosphorylation
What is a metabolic pathway?
A linked series of chemical reactions occurring within a cell
What is the energy produced in aerobic respiration used for?
Phosphorylate ADP to ATP
Where does glycolysis take place?
Cytoplasm
Where does the Link reaction, Krebs cycle and oxidative phosphorylation take place?
Mitochondria
What catalyses the aerobic respiration reactions?
Specific intracellular enzymes
Coenzymes
What is the enzyme with the slowest activity called?
Rate limiting - determines the overall rate of repsiration
What are the coenzymes used in respiration called?
NAD and FAD - transfer hydrogen form one molecule to another so they reduce or oxidise a molecule.
Coenzyme A - transfers acetate between molecules.
Describe Glycolysis (5)
1) Glucose (6C) is phosphorylated by adding 2 phosphates from 2 molecules of ATP, increasing reactivity of glucose
2) This creates 2 molecules of triose phosphate (3C)and 2 molecules of ADP
3) Triose phosphate is oxidised, forming 2 molecules of pyruvate (3C)
4) NAD removes hydrogen ions, forming 2 reduced NAD
5) 4 ATP are produced, but 2 were used up in stage 1, so net gain = 2 ATP
Why is glycolysis a substrate-level phosphorylation?
Energy for the formation of ATP comes from the substrates as glucose is at a higher energy level than pyruvates so energy is available to create ATP.
Where do the 2 molecules of reduced NAD and 2 pyruvate molecules produced in glycolysis go?
2 reduced NAD - used for oxidative phosphorylation
2 pyruvate molecules - matrix of mitochondria for link reaction
Describe the Link Reaction (5)
1) Pyruvate is decarboxylated - one carbon atom is removed from pyruvate in the form of CO2
2) NAD is reduced - collects 2 hydrogen from pyruvate changing it into acetate
3) Acetate is combined with coenzyme A to form acetyl coenzyme A
4) No ATP is produced
5) This repeats twice for every 1 glucose molecule
Describe the Krebs Cycle (9)
1) Acetyl CoA (2C) from link reaction combines with oxaloacetate (4C) to form citrate (6C)
2) CoA goes back to link reaction
3) Citrate (6C) is converted to 5C molecule - decarboxylation occurs, hydrogen is removed
4) Hydrogen converts NAD to reduced NAD
5) 5C molecule is converted to 4C molecule
6) Decarboxylation and dehydrogenation occur, producing 1 molecule of reduced FAD and 2 reduced NAD
7) ATP is produced by direct transfer of phosphate group from intermediate compound to ADP. When phosphate is directly transferred form one molecule to another, its called substrate-level phosphorylation
8) Citrate has been converted into oxaloacetate
9) This repeats twice for 1 glucose molecule
What are the products of the Krebs cycle and where are they reused?
1 CoA - next link reaction
Oxaloacetate - regenerated for next Krebs cycle
2 CO2 - waste product
1 ATP - energy
3 Reduced NAD - oxidative phosphorylation
1 Reduced FAD - oxidative phosphorylation
Describe Oxidative Phosphorylation (10)
1) Process where energy carried by electrons, from reduced coenzymes (reduced NAD and reduced FAD) is used to make ATP
2) Involves 2 processes - the electron transport chain and chemiosmosis
3) Hydrogen atoms are released from reduced NAD and reduced FAD as they’re oxidised to NAD and FAD
4) H atoms split into protons and electrons
5) Electrons move down electron transport chain losing energy at each carrier
6) Energy is used by electron carriers to pump protons from mitochondrial matrix into intermembrane space
7) Concentration of protons is higher in the intermembrane space than in mitochondrial matrix - forms an electrochemical gradient
8) Protons move down electrochemical gradient back into mitochondrial matrix via enzyme ATP synthase
9) This movement drives synthesis of ATP from ADP and inorganic phosphate - called chemiosmosis
10) In mitochondrial matrix, at end of transport chain, the protons, electrons and O2 combine to form water. Oxygen is the final electron acceptor
How many ATP molecule are made form 1 glucose molecule?
38
How can you measure the rate of respiration?
A respirometer measures the volume of oxygen being taken up in a given time - more oxygen taken up = faster rate of reaction.
1) Set up respirometer
2) Each tube contains potassium hydroxide solution (soda lime) which absorbs carbon dioxide
3) Control tube is set up in exactly the same way as the set tube but without small invertebrates (e.g. woodlice) to make sure results are only due to organisms respiring (it contains bead the same mass as organisms)
4) The syringe is used to set the fluid in the manometer to a known level
5) Apparatus is left for set period of time
6) There will be a decrease in the volume of air in the test tube due to oxygen consumption, CO2 is absorbed by soda lime
7) Decrease in volume of air will reduce pressure in the tube and cause the coloured liquid in the manometer to move towards the test tube
8) Distance moved by the liquid in a given time is measured -this value can be used to calculate volume of oxygen taken in per min
9) Any variables that could affect results are controlled (e.g. temperature, volume of soda lime)
What type of respiration is Lactate Fermentation?
Anaerobic respiration
Describe Lactate Fermentation (3)
1) Glucose is converted to pyruvate via glycolysis
2) Reduced NAD from glycolysis transfers hydrogen to pyruvate to form lactate and NAD
3) NAD can then be reused in glycolysis
How is lactic acid broken down?
Cells convert lactic acid into pyruvate - which enter Krebs cycle.
Liver cells convert lactic acid back to glucose - respired or stored.
What is the effect of lactate build-up?
- Many of the amino acids that make up an enzyme have +ve or -ve charged groups
- As hydrogen ions from lactic acid accumulate in the cytoplasm, the neutralise the -ve groups in the active site of enzyme.
- Substrate may no longer bind to enzymes active site
What does myogenic mean?
A contraction initiated by the myocyte cell itself instead of an outside occurrence or stimulus such as nerve innervation.
Describe how the Cardiac Muscle controls the regular beating of the heart.
1) Process starts in sino-atrial node (SAN) in the wall of the right atrium
2) SAN is like a pacemaker - sets the rhythm of the heartbeat by sending out regular waves of electrical activity to the atrial walls
3) Causes right and left atria to contract at the same time
4) A band of non-conducting collagen tissue prevents waves of electrical activity form being passed directly from atria to ventricles
5) Instead, waves of electrical activity are transferred from SAN to atrioventricular node (AVN)
6) AVN is responsible for passing waves of electrical activity on to the bundle of His. There is a slight delay before the AVN reacts, to make sure ventricles contract after the atria gave emptied
7) Bundle of His is a group of muscle fibres responsible for conducting waves of electrical activity to the finer muscle fibres in the right and left ventricles walls, called Purkyne fibres
8) Purkyne fibres carry waves of electrical activity into muscular walls of left and right ventricles causing them to contract simultaneously form bottom up.
What is an electrocardiogram?
A machine that records the electrical activity of the heart by recording changes in electrical charge using electrodes placed on the chest
How does the electrical charge in the heart change?
Depolarises (loses charge) when contracts
Repolarises (regains charge) when relaxes
Describe an electrocardiogram.
P wave - contraction (depolarisation) of the atria (ARTIAL SYSTOLE)
PR interval - the time taken for impulses to be conducted from SAN across to atria and ventricles through AVN
QRS complex - main peak, contraction (depolarisation) of the ventricles (VENTRICULAR SYSTOLE)
T wave - relaxation (repolarisation) of the ventricles
Height of waves indicates how much electrical charge is passing through the heart (DIASTOLE)
What is an ECG used for?
Diagnosing heart problems
How do doctors diagnose problems with the heart’s rhythm?
Compare patient’s ECGs with a normal trace
What is tachycardia?
Heartbeat is too fast
Heart isn’t pumping blood efficiently
What is bradycardia?
Heartbeat too slow
What is an ectopic heart?
Heart has an ‘extra’ heartbeat
Doesn’t cause a problem in a healthy person
What is fibrillation?
Irregular heartbeat
Atria or ventricles lose their rhythm and stop contracting properly
Result in chest pain and fainting to lack of pulse and death
What area of the brain controls breathing rate?
The Medulla Oblongata
Describe the Medulla Oblongata
Contains areas called ventilation centres
Two ventilation centres - the inspiratory centre and the expiratory centre
Describe how the Medulla Oblongata controls breathing rate (9)
1) Inspiratory centre in the Medulla Oblongata sends nerve impulses every 2-3 seconds to the external intercostal and diaphragm muscles to make them contract
2) Increases the volume of lungs, lowers pressure
3) Inspiratory centre also send nerve impulses to expiratory centre, inhibits its action
4) Air enters lungs due to pressure difference between lungs and air outside
5) As lungs inflate, stretch receptors in bronchioles are stimulated
6) Stretch receptors send nerve impulses back to medulla oblongata, inhibits action of inspiratory centre
7) Expiratory centre is no longer inhibited, so sends nerve impulses to the diaphragm and intercostal muscles to relax
8) Causes lungs to deflate because of elastic recoil and by gravity lowering ribs, expelling air
9) Stretch receptors become inactive and cycle starts again
How does exercise affect breathing rate and the blood?
- Level of Carbon Dioxide in blood increases, decreases pH
- Chemoreceptors in the Medulla Oblongata, aortic bodies (cluster of cells in aorta) and carotid (cluster of cells in carotid arteries) are sensitive to changes in blood pH
- If Chemoreceptors detect a decrease in blood pH, they send nerve impulses to Medulla Oblongata which sends more frequent nerve impulses to intercostal muscles and diaphragm. This increases rate and depth of breathing.
- This causes gaseous exchange to speed up
- Carbon Dioxide level drops and extra oxygen is supplied for muscles, pH returns to normal and breathing rate increases
What is ventilation rate?
The volume of air breathed in or out in a period of time
What muscles are only used during deep inhalation?
Internal intercostal muscles
What is minute ventilation and how do you work it out?
The volume of air taken into the lungs in 1 minute.
minute ventilation = tidal volume x number of breaths
How is heart rate controlled?
Unconsciously by cardiovascular control centre in the Medulla Oblongata.
- Electrical impulses from chemical and pressure receptors in the blood are sent along sensory neurones to Medulla Oblongata
- Cardiovascular control centre processes information and sends impulses to SAN along sympathetic and parasympathetic neurones
- These release different chemicals (neurotransmitters) onto SAN which speeds up or slows down heart rate
- SAN generates electrical impulses that cause the atria to contract, which sets rhythm of heartbeat
Why does heat rate need to be controlled?
Animals need to alter heart rate to respond to external stimuli
What receptors detect stimuli in the blood?
Chemical receptors - chemoreceptors in aortic and carotid bodies and in Medulla Oblongata , monitor oxygen and carbon dioxide levels and pH
Pressure receptors - baroreceptors in aortic and carotid bodies, stimulated by high and low blood pressure
What is cardiac output and how do you work it out?
The total volume of blood pumped by a ventricle every minute
cardiac output = heart rate x stroke volume
What is stroke volume?
Volume of blood pumped by one ventricle each time it contracts
Describe how the body responds to high blood pressure
1) Barorcceptors detect high blood pressure
2) Impulses sent to cardiovascular control centre
3) Sends impulses along parasympathetic neurones
4) Secrete acetycholine which binds to SAN receptors
5) SAN fires impulses less frequently to slow heart rate and reduce blood pressure back to normal
Describe how the body responds to low blood pressure
1) Baroreceptors detect low blood pressure
2) Impulses sent to cardiovascular control centre along sympathetic neurones
3) Secrete noradrenaline which binds to SAN receptors
4) SAN fires impulses more frequently to increase heart rate and blood pressure back to normal
Describe how the body responds to high blood oxygen, low carbon dioxide or high pH
1) Chemoreceptors detect chemical changes in the blood
2) Impulses sent to cardiovascular control centre along parasympathetic neurones
3) Secrete acetylcholine which binds to SAN receptors
4) SAN fires impulses less frequently to decrease heart rate and return oxygen, carbon dioxide and pH levels back to normal
Describe how the body responds to low blood oxygen, high carbon dioxide or low pH
1) Chemoreceptors detect chemical changes in the blood
2) Impulses sent to cardiovascular control centre along sympathetic neurones
3) Secrete noradrenaline which binds to SAN receptors
4) SAN fires impulses more frequently to increase heart rate and return oxygen, carbon dioxide and pH levels back to normal
What is tidal volume?
The volume of air in each breath, usually about 0.4dm3
What is breathing rate?
How many breaths are taken, usually in a minute
What is oxygen consumption?
The volume of oxygen used by the body, often expressed as a rate
What is respiratory minute ventilation and how do you work it out?
The volume of gas breathed in or out in a minute
respiratory minute ventilation = tidal volume x breathing rate
How do you measure ventilation?
1) A spirometer has an oxygen-filled chamber with a moveable lid
2) A person breathes through a tube connected to the oxygen chamber
3) As the person breaths in the lid of the chamber moves down. When they breathe out it moves up
4) These movements are recorded by a pen attached to the lid of the chamber - this writes on a rotating drum, creating a spirometer trace
5) The total volume of gas in the chamber decreases over time.
- This is because the air that’s breathed out is a mixture of oxygen and carbon dioxide but the carbon dioxide is absorbed by the soda lime.
- This means that there’s only oxygen in the chamber which the person inhales from - as this gets used up by respiration, total volume decreases.
How can investigate the effects of exercise using a spirometer?
1) A person breathes into a spirometer for one minute at rest and recordings are taken
2) The person then exercises for 2 minutes. While the person is exercising the spirometer chamber is refilled with oxygen
3) Immediately after the person stops exercising, they breathe into the spirometer again and recordings are taken for another minute
4) The recordings taken before and after are then compared
How do analyse a spirometer trace?
Breathing rate - count the number of peaks in the trace in a minute
Tidal volume - find the average difference in the volume of gas between each peak and trough
Oxygen consumption - find the change in volume of gas in the spirometer
How do you test whether exercise has a significant effect on tidal volume at rest?
Use t-test
What can affect your internal environment?
Your external environment and what you’re doing
What is homeostasis?
Maintenance of a stable internal environment involving control systems that keep your internal environment within narrow limits - your internal environment is kept in a state of dynamic equilibrium.
Why is homeostasis important?
Keeping your internal environment constant is vital for cells to function normally and to stop them being damaged.
E.g. if body temp is too high enzymes become denatured as the molecules vibrate too much which breaks hydrogen bonds that hold 3D shape. Shape of active site changes and so no longer works as a catalyst
How is a constant energy supply for cells managed?
Blood glucose concentrations carefully controlled.
Concentration of glucose in blood is normally around 90 mg per 100cm3
Monitored by pancreas
Blood glucose concentration falls after exercise as more glucose is used in respiration to release energy
What is the role of the pancreas?
Monitor concentration of glucose in blood
What is the role of the kidneys?
Regulate water content of blood and urine
Describe how homeostatic systems works
1) Homeostatic system involve receptors, a communication system and effectors
2) Receptors detect when a level is too high or too low and the info communicated via the nervous system or the hormonal system to effectors
3) Effectors respond to counteract the change - bringing back the level back to normal (negative feedback mechanism)
4) Negative feedback keeps things around the normal level - e.g. body temp 37 + or - 5
5) Negative feedback only works within certain limits - if change is too big then effectors may not be able to counteract it
What is negative feedback?
A mechanism that restores the level to normal
What is positive feedback?
Changes are amplified away form normal level
What mechanisms are used to reduce body temperature?
Sweating - more sweat is secreted form sweat glands. Water in sweat evaporates from surface of skin and takes heat from body. Skin is cooled
Hairs lie flat - mammals have a layer of hair that provides insulation by trapping air. When its hot, erector pili muscles relax so hairs lie flat. Less air is trapped so skin is less insulated and heat can be lost more easily
Vasodilation - when its hot arterioles near the surface of the skin dilate so more blood flows through the capillaries in the surface layers of the dermis. This means more heat is lost form the skin by radiation and temp is lowered.
What mechanisms increase body temperature?
Shivering - muscles contract in spasms which makes body shiver and more heat is produced from increased respiration
Much less sweat - less sweat is secreted from sweat glands when its cold reducing the amount of heat loss
Hairs stand up - erector pili muscles contract which makes hairs stand up which traps more air and so prevents heat loss
Vasoconstriction - arterioles near surface of skin constrict so less blood flows through capillaries in surface layers of dermis which reduces heat loss
Hormones - body releases adrenaline and thyroxine which increases metabolism and so more heat is produced
What controls body temperature?
The hypothalamus in the brain
How does the body control body temperature?
Maintained at a constant level by hypothalamus (thermoregulation)
- Receives info about temp from thermoreceptors
- Thermoreceptors send impulses along sensory neurones to hypothalamus which sends impulses along motor neurones to effectors
- Effectors respond to restore the body temp back to normal
What is the control of body temp called?
Thermoregulation
What are transcription factors?
Proteins that control the transcription of genes
- Bind to DNA sites near the start of the genes and increase or decrease the rate of transcription.
- Factors that increase the rate are called activators
- Factors that decrease the rate are repressors
Hormones affect activity of transcription factors
How do hormones regulate body temperature inside a cell?
At normal body temp
- thyroid hormone receptor (transcription factor) binds to DNA at start of gene
- this decreases the transcription of a gene coding for a protein that increases metabolic rate
At cold temperature
- thyroxine is released which binds to thyroid hormone receptor, causing it to act as an activator
- the transcription rate increases, producing more protein
- protein increases metabolic rate causing an increase in body temperature
How do hormones regulate body temperature from the cell membrane?
Some hormones can’t cross the cell membrane but they can still affect transcription factors
- bind to receptors in the cell membrane which activate messenger molecules in the cytoplasm
- these messenger molecules activate enzymes called protein kinases, which triggers a cascade inside the cell
- during cascade, transcription factors can be activated
What is keyhole surgery?
A way of doing surgery without making a large incision in the skin
- Much smaller incision
- Insert tiny video camera
- Specialised medical instruments though incision into body
What are the advantages of keyhole surgery?
- Operations don’t involve opening up the patient so much so patients lose less blood and have less scarring of the skin
- Patients usually in less pain after operation and recover more quickly because less damage is done
- Makes it easier for patient to return to normal activities and their hospital stay is shorter
What injury can be fixed by keyhole surgery?
Damaged cruciate ligaments
- Ligaments found in the middle of your knee, connecting thigh bone to lower leg bone
- Damaged cruciate ligament can be removed and replaced with a graft
- Graft is likely to be from a tendon in patient’s leg
What can replace damaged body parts?
Prostheses can be used to replace whole limbs or parts of limbs
- some include elecrtic devices that operate the prostheses by picking up info sent by nervous system
What injury can be fixed by prostheses?
Damaged knee joints can be prosthetic joints
- Metal device is inserted into the knee to replace damaged cartilage and bone
- Knee joint and the ends of the leg bones are replaced to provide a smooth knee joint, cushioning in the new joint helps reduce impact on knee
Name 3 types of performance-enhancing drugs
Anabolic steroids - increase strength, speed and stamina by increasing muscle size and allowing athletes to train harder. Also increase aggression
Stimulants - speed up reactions, reduce fatigue and increase aggression
Narcotic analgesics - reduce pain, so injuries won’t affect performance
Where does Glycolysis take place? Is oxygen needed?
Cytoplasm
No
Where does Link Reaction take place? Is oxygen needed?
Matrix of Mitochondria
Yes
Where does Kreb’s Cycle take place? Is oxygen needed?
Matrix of Mitochondria
Yes
Where does ETC. take place? Is oxygen needed?
Crista of Inner Membrane of Mitochondria
Yes
What is substrate level phosphorylation?
The synthesis of ATP through the direct transfer of a phosphate group from a substrate to a molecule of ADP.
Reaction is catalysed by kinase
What is oxidative phosphorylation?
The process where the energy carried by electrons, from reduced coenzymes, is used to make ATP.
Involves two processes:
- Electron transport chain
- Chemiosmosis
