BIOLOGY MODULE 5 (papers 1 & 3) incomplete - add plant hormone PAGs and kidney stuff after mocks Flashcards
communication and homeostasis, excretion, animal responses, photosynthesis, respiration, plant hormones and responses
how does responding to their environment help an organism survive?
- e.g. avoiding harmful environments
- respond to changes in their internal environment to make sure conditions are optimal for metabolism
- any change in internal or external environment is a stimulus
- important for plants and animals
how do receptors detect a stimuli to produce a response?
- receptors only detect one particular stimulus
- some receptor cells connect to the nervous system, some are proteins on cell surface membrane and some are found in cell membranes of some pancreatic cells
what are effectors?
cells that bring about a response to a stimulus to produce an effect (include muscle cells and glands)
how does communication occur between adjacent and distant cells?
- to produce a response receptors must communicate and this happens via cell signalling
- cell signalling can occur between adjacent or distant cells e.g. NS cells communicate via neurotransmitters being detected
- cell surface receptors allow cells to recognise chemicals involved in cell signalling
what is homeostasis?
- maintenance of a constant internal environment
- involves control systems that keep internal environment roughly constant
- vital for cells to function normally and stop them being damaged
- maintaining core temp stops enzymes being denatured
- maintaining right conc of glucose in blood means theres always enough for respiration
what is your internal environment?
blood and tissue fluid that surrounds your cells
how do homoestatic systems detect a change and respond by negative feedback?
- involve receptors, a communication system and effectors
- receptors detect when a level is too high/low and info is communicated to effectors
- effectors respond to counteract change - brings level back to normal
- negative feedback restores level to normal
- negative feedback keeps things around normal level
why does negative feedback only work within certain limits?
if the change is too big then effectors may not be able to counteract it
how do positive feedback mechanisms amplify a change from the normal level?
- effectors respond to further increase the level away from normal level
- positive feedback is useful to rapidly activate something
- not involved in homeostasis as it doesnt keep internal environment constant
what does the nervous system send information as?
nerve impulses
what is the nervous system and how does it send information as nerve impulses?
- complex network of neurones
- stimulus is detected by receptor cells and a nerve impulse is sent along a sensory neurone
-when nerve impulse reaches end of neurone, neurotransmitters take info to next neurone which send a nerve impulse - CNS processed information and sends it along neurones to an effector
what are sensory neurones?
transmit nerve impulses from receptors to CNS
what are motor neurones?
transmit nerve impulses from CNS to effectors
what are relay neurones?
transmit nerve impulses between sensory and motor neurones and transmit action potentials through the CNS
what is the process of a nerve impulse travelling?
stimulus - receptors - CNS - effectors - response
what do sensory receptors do?
- convert energy of a stimulus into electrical energy
- so sensory receptors act as transducers (something that converts one form of energy into another)
how do receptor cells communicate information via the nervous system?
- when NS receptor is in resting state, there’s a difference in charge between inside and outside the cell generated by ion pumps and channels
- this means there is a voltage (potential difference) across the membrane
- when a stimulus is detected the cell membrane becomes excited and more permeable, allowing more ions to move in and out the cell - altering potential difference
- bigger stimulus excites membrane more, causing larger movement of ions and bigger generator potential
what is resting potential?
voltage/potential difference across a membrane when a cell is when a cell is at rest
what is generator potential?
the change in potential difference due to a stimulus
how is an action potential triggered?
if a generator potential is big enough and reaches a threshold level
what is the structure of a sensory neurone?
- short dendrites
- one long dendron to carry nerve impulses from receptor cells to cell body
- one short axon that carried impulses from cell body to CNS
what is the structure of a motor neurone?
- many short dendrites that carry nerve impulses from CNS to cell body
- one long axon that carries nerve impulses from cell body to effector cells
what is the structure of a relay neurone?
- has many short dendrites that carry nerve impulses from sensory neurones to cell body
- one axon that carried nerve impulses from cell body to motor neurones
what is an example of a sensory receptor converting stimulus energy into nerve impulses?
- pascinian corpuscles contain the end of a sensory neurone (sensory nerve ending)
- sensory nerve ending is wrapped in lamellae
- when pascinian corpuscle is stimulated, lamellae are deformed and press on sensory nerve ending
- this causes deformation of stretch-mediated sodium channels in sensory neurones cell membrane
- sodium channels open and sodium ions diffuse into cell creating generator potential
explain how neurone cell membranes are polarised at rest
- in neurones resting state, outside of membrane is positively charged compared to inside - membrane is polarised
- resting potential = -70mV
- resting potential is created and maintained by sodium-potassium pumps and potassium ion channels in a membrane
- sodium-potassium pumps move sodium ions out the neurone and potassium ions in
- makes outside cell more positively charged than inside
what does a sodium-potassium pump do?
moves sodium ions out of the neurone by membrane isnt permeable to sodium ions so they cant diffuse back in - creates sodium electrochemical gradient (conc gradient of ions) because there’s more positive sodium ions outside
- what is the stimulus stage of an action potential?
- stimulus excites neurone cell membrane causing sodium ion channels to open
- membrane becomes more permeable to sodium so sodium ions diffuse into neurone down sodium electrochemical gradient
- make inside of neurone less negative
- what is the depolarisation stage of an action potential?
- if potential difference reaches threshold, voltage-gated sodium channels open
- more sodium ions diffuse into neurone
- this is positive feedback
- what is the repolarisation stage of an action potential?
- at potential difference of +30mV the sodium channels close and voltage-gated potassium ion channels open
- membrane is more permeable to potassium so potassium ions diffuse out the neurone down a conc gradient
- starst to get membrane back to resting potential
- this is negative feedback
- what is the hyperpolarisation stage of an action potential?
- potassium ion channels are slow to close so too many potassium ions may diffuse out the neurone
- potential difference becomes more negative than resitng potential (less than -70mV)
- what is the resting potential stage of an action potential?
- ion channels reset
- sodium-potassium pump returns membrane to resting potential and maintains until membrane’s excited by another stimulus
what is the refractory period?
after an action potential the cell membrane cant be excited again straight away because ions are recovering and cant be made to open
how does an action potential move alone the neurone?
- wave of depolarisation
- when action potentials happen, some sodium ions that enter diffuse sideways
- causes sodium ion channels in next region to open and sodium ions diffuse in
- causes a wave of depolarisation
- the wave moves away from parts of membrane in refractory period as they cant fire an action potential
what is the effect of a bigger stimulus on impulses?
- once threshold is reached, an action potential will always fire with the same change in voltage
- bigger stimulus wont cause bigger action potential but will cause more frequent action potentials
what is the all or nothing nature of action potentials?
action potentials will only fire is threshold is reached and will always fire with the same change in voltage
what is the myelin sheath?
- electrical insulator
- made of schwann cells
- between schwann cells there are patches of bare membrane called the nodes of ranvier (where sodium ions get through the membrane)
what happens in a myelinated neurone?
- depolarisation only happens at nodes of ranvier (sodium ion channels are concentrated at nodes)
- neurones cytoplasm conducts enough electrical charge to depolarise next node - impulse ‘jumps’ to next node (SALTATORY COONDUCTION)
what happens in a non myselinated neurone?
- impulse travels as a wave along the whole length of the axon membrane
- slower than saltatory conduction
what is the difference between depolarisation and repolarisation?
depolarisation - difference in charge across cell membrane becomes smaller
repolarisation - difference in charge across cell membrane becomes bigger
what? is a synapse
a junction between a neurone and the next cell (neuone/effector)
what is the synaptic cleft?
tiny gap between cells at a synapse
what is the presynaptic neurone and what happens to it?
- one before the synapse
- has a swelling called synaptic knob
- this contains synaptic vesicles filled with neurotransmitters
what happens when an action potential reaches the end of a neurone?
- causes neurotransmitters to be released into synaptic cleft
- they diffuse across postsynaptic membrane or cause a hormone to be secreted from a gland cell
what happens when a neurotransmitter binds to a receptor?
- might trigger an action potential in a neurone
- cause a muscle contraction in a muscle cell
- or cause a hormone to be released from a gland cell
neurotransmitters are removed from the cleft so the response doesn’t keep happening
what are the synapses called that use acetylcholine?
- cholinergic synapses
- bind to receptors called cholinergic receptors
- broken down by acetylcholinesterase (AChE))
how does a neurotransmitter transmit nerve impulses between neurones?
- action potential triggers calcium influx
- calcium influx causes neurotransmitter release
- neurotransmitter triggers action potential and postsynaptic neurone
what happens when 1. an action potential triggers calcium influx?
- action potential arrives at synaptic knob of presynaptic neurone
- action potential stimulates voltage-gated calcium ion channels in presynaptic neurone to open
- calcium ions diffuse into synaptic knob
what happens when 2. calcium influx causes neurotransmitter release?
- influx of calcium ions into synaptic knob causes synaptic vesicles to move to presynaptic membrane - they fuse with presynaptic membrane
- vesicles release the neurotransmitters into synaptic cleft by exocytosis
what happens when 3. the neurotransmitter triggers an action potential in the postsynaptic membrane?
- neurotransmitter diffuses across synaptic cleft and binds to specific receptors on postsynaptic membrane
- causes influx of sodium ion channels in postsynaptic neurone to open - causes depolarisation and action potential happens if threshold is reached
- neurotransmitter is removed from synaptic cleft so response doesn’t keep happening
what is an excitatory synapse?
at excitatory synapse, neurotransmitters depolarise in postsynaptic membrane - fires action potential if threshold is reached
what is an inhibitory synapse?
at inhibitory synapse, when neurotransmitters bind to receptors on postsynaptic membrane, they hyperpolarise the membrane and prevent an action potential being fired
what is synaptic divergence?
when one neurotransmitter is connected to many neurones, info can be dispersed to different parts of the body
what is synaptic convergence?
when many neurones connect t one neurone, info can be amplified (made stronger)
what is summation?
effects of neurotransmitters can be combined to cause an action potential
- 2 types: spatial and temporal
what is spatial summation?
- when neurones converge, the small amount of neurotransmitter released from each neurone can be enough to reach threshold for action potential
- if one neurones release inhibitory neurotransmitters then total effect of all neurotransmitters may be no action potential
- stimuli may arrive from different sources, spatial summation allows signals from multiple stimuli to be coordinated into a single response
what is temporal summation?
- when 2 or more nerve impulses arrive in a quick succession from the same presynaptic neurone
- makes action potential more likely as neurotransmitter is released into synaptic cleft
how do synapses make sure impulses are transmitter one way?
receptors for neurotransmitters are only on postsynaptic membranes so synapses make sure impulses only go one way
what is the hormonal system?
- made of endocrine glands and hormones
- endocrine glands are groups of cells specialised to secrete hormones
- hormones are chemical messengers - hormones diffuse directly into blood, then taken around the body by circulatory system
- they diffuse out of blood all over the body but each hormone only binds to a specific receptor (target cells)
- hormones trigger a response in the target cells (effectors)
how are hormones secreted? (hormonal system)
- secreted by endocrine glands
- glands can be stimulated by change in concentration of specific substance
- can also be stimulated by electrical impulses
what is the process of the hormonal system?
stimulus - receptors - hormone - effectors - response
- why is a hormone a first messenger? 2. why is a signalling molecule a second messenger?
- it carries the chemical message the first part of the way from the endocrine gland to the receptor on target cell
- it carried the chemical message the second part of the way from receptor to other parts of the cell
how do hormones bind to receptors and trigger second messengers?
- when a hormone binds to its receptor it activates an enzyme in cell membrane
- enzyme catalyses production of signalling molecule (second messenger)
- second messengers activate a cascade (chain of reactions) inside the cell
what is an example of a hormone binding to a receptor and triggering second messengers? (learn)
- adrenaline (first messenger) binds to specific receptors in cell membrane e.g. liver cell
- this activated adenylyl cyclase (enzyme) which catalyses production of cAMP (second messenger) from ATP
- cAMP activates cascade reactions to make more glucose available to the cell by catalysing breakdown of gycogen into glucose
what are adrenal glands?
- endocrine glands above the kidneys
- each gland has cortex (outer) and medulla (inner)
- cortex and medulla have different functions to produce different responses
how are the cortex and medulla involved in the response to stress?
- cortex secretes steroid hormones and these hormones both have a role in long and short term response to stress
- medulla secretes catechoamine hormones which act to make more energy available in the short term
what are the effects of the cortex in response to stress?
- stimulating breakdown of proteins and fats into glucose - increases amount of energy available so brain and muscles can respond to situation
- increasing blood volume and pressure by increasing uptake of sodium ions and water by kidneys
- suppressing immune system
what are the effects of the medulla in response to stress?
- increasing heart and breathing rate
- causes cells to breakdown glycogen into glucose
- constricting some blood vessels so blood is diverted to brain and muscles
what is the role of the pancreas in the endocrine system?
- areas of pancreas involved are the Islets of Langerhans
- found in blood capillaries
- they secrete hormones directly into blood
- made of alpha cells (secrete glucagon) and beta cells (insulin)
- glucagon and insulin help control blood glucose conc
how is temperature controlled in ectotherms?
- ectotherms cant control body temperature internally - control their temp by changing their behaviour
- internal temp depends on external temp (surroundings)
- activity level depends on external temp (higher temp = more active)
- have variable metabolic rate & generate little heat themselves
how is temperature controlled in endotherms?
- control body temp internally by homeostasis - can also control it through behaviour
- internal temp is less affected by external temp
- activity level doesnt depend on external temp - can be active anytime
-have constantly high metabolic rate and generate lots of heat from metabolic reactions
how does sweating reduce body temperature?
sweat evaporates from skin and takes heat with it
how do hairs lying flat reduce body temperature?
- layer of hair provides insulation by trapping air
- when its hot pili muscles relax so less air is trapped and skin is less insulated - heat is lost more easily
how does vasodilation reduce body temperature?
- when its hot arterioles near surface dilate
- more blood flows through capillaries so more heat is lost from skin by radiation
how does the hypothalamus control body temperature in mammals?
- hypothalamus receives info about temp from thermoreceptors - thermoreceptors in hypothalamus detect internal temp (blood temp) & thermoreceptors in skin (peripheral temp receptors) detect external temp
- themoreceptors send impulses along sensory neurones to hypothalamus, which sends impulses along motor neurones to effectors
how does eating and exercise change concentration of glucose in blood?
- conc of glucose in blood is normally 90mg per 100cm3 of blood
- blood glucose rises after eating food containing carbohydrate and falls after exercise (more glucose is used to release energy in respiration)
which cells secrete insulin and glucagon to control blood glucose concentration?
- beta cells secrete insulin into blood
- alpha cells secrete glucagon into blood
how does insulin affect blood glucose?
lowers blood glucose when its too high
- insulin binds to specific receptors on cell membrane of liver and muscle cells
- increases permeability of cells to glucose so cells take up more glucose
- activates enzymes that covert glucose to glycogen (glycogenesis)
- cells can store glycogen in cytoplasm as energy source
- insulin increases rate of respiration of glucose
how does glucagon affect blood glucose?
raises blood glucose when its too high
- binds to specific receptors in cell membranes of liver cells
- activates enzymes that break down glycogen into glucose (glycogenolysis)
- glucagon promotes formation of glucose from glycerol and amino acids (gluconeogenesis - forming glucose from non-carbs)
- glucagon decreases rate of respiration of glucose
what happens to beta cells when theyre depolarised?
secrete insulin
how do beta cells secrete insulin when they detect high blood glucose concentration?
- when blood glucose conc is high, more glucose enters beta cells by facilitated diffusion
- more glucose in beta cells causes rate of respiration to increase making more ATP
- means K+ cant get through so build up inside cell
- makes inside of beta cell less negative so plasma membrane of beta cell is depolarised
- depolarisation triggers calcium ion channel cells in membrane to open so calcium ions enter beta cell
- causes vesicles to fuse with beta plasma membrane & release insulin
what is type 1 diabetes?
- no insulin is produced
- usually develops in children/young adults
1. is an autoimmune disease which attacks and destroys the beta cells in islets of Langerhans
2. after eating, blood glucose conc rises and stays high
3. kidneys can’t reabsorb all glucose so some is excreted in urine
how do you treat type 1 diabetes?
- regular insulin injections
- insulin pump (machine that continually delivers into body)
- islet cell transplantation (donor) so pancreas can produce some insulin
- healthy balanced diet to manage amount of glucose they taken in
- regular exercise reduces amount of insulin needed to be injected
what is type 2 diabetes?
- linked to obesity
- beta cells don’t produce enough insulin or body cells don’t respond properly to insulin
1. cells don’t respond properly as insulin receptors dont work properly - blood glucose higher than normal
how do you treat type 2 diabetes?
- healthy balanced diet
- exercise
- metformin - medication that acts on liver cells to reduce glucose levels sulfonylureas - stimulate pancreas to produce more insulin
- insulin therapy
why is insulin be produce by genetically modified bacteria?
- cheaper than extracting it from animal pancreas
- more insulin can be produced
- make human insulin and is more effective than using pig or cattle insulin
- som prefer it for ethical/religious reasons
how are stem cells use to cure pigs?
- unspecialised cells
- can be grown into beta cells and implanted in pancreas of type 1 diabetic to make insulin
what is excretion?
removal of waste products of metabolism from the body
- e.g. CO2 and nitrogenous waste
- most waste products are toxic
what are the functions of the liver?
- breaks down excess amino acids
- removes other harmful substances from blood
- stores glycogen
how are excess amino acids broken down by the liver?
- amino groups are removed from excess amino acids, forming ammonia and organic acids (deamination)
- organic acids can be respired to give ATP, or can be converted to carbs stored as glycogen
- ammonia is too toxic for mammals so is combined with CO2 in ornithine cycle to create urea
- urea’s is released from liver into blood, kidneys filter blood and remove urea as urine
what other harmful substances does the liver remove from blood?
- alcohol (ethanol) - toxic substance that can damage cells, broken down by the liver into ethanal, then broken down into less harmful substance - acetic acid
- paracetamol - broken down by the liver, excess paracetamol can lead to liver and kidney failure
- insulin - can cause problems with blood glucose levels
how does the liver store glycogen?
- body needs glucose for energy
- liver converts excess glucose in blood to glycogen and stores it as granules in its cells until glucose is needed for energy
what is the hepatic artery in the liver?
supplies liver with oxygenated blood from heart, so liver has good supply of oxgyen for respiration
what is the hepatic vein in the liver?
takes deoxygenated blood away from liver
what is the hepatic portal vein in the liver?
brings blood from duodenum and ileum (parts of small intestine) so its rich in products of digestion - harmful ingested substances are filtered out and broken down right away
what is the bile duct in the liver?
takes bile to gall bladder to be stored
what is the structure of the liver?
- liver is made of liver lobules
- each lobule has a central vein in the middle that connects to hepatic vein
- many branches of hepatic artery, hepatic portal vein and bile duct are connected to each lobule
what are liver lobules?
cylinder structures made of hepatocytes arranged in rows radiating out from the centre
what is the structure/function of the liver lobule?
- hepatic artery and portal vein connected by sinusoids
- blood runs through sinusoids, past hepatocytes that remove harmful substances and O2 from blood
- harmful substances are broken down by hepatocytes into less harmful substances that re-enter blood
- blood runs to central vein, central veins from all lobules form hepatic vein
- Kupffer cells attached to walls of sinusoids
- hepatocytes produce bile to secrete into bile canaliculi that drain into bile ducts
what do Kupffer cells do?
remove bacteria and break down old red blood cells
INSERT KIDNEY CARDS HERE !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
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(page 151-154)
what is water reabsorption controlled by?
hormones
how is water potential controlled by hormones?
- WP is monitored by osmoreceptors in hypothalamus
- when osmoreceptors are simulated by low WP in blood, hypothalamus sends nerve impulses to posterior pituitary gland and releases ADH into blood
- ADH makes walls of distal convoluted tubule and collecting duct more permeable to water
makes more water reabsorbed from tubules into medulla and into blood (osmosis)
what happens to blood ADH when you’re dehydrated?
- ADH levels rise
1. water content of blood drops so WP drops
2. detected by osmoreceptors in hypothalamus
3. posterior pituitary gland is stimulated to release more ADH into blood
4. more ADH means that DCT and collecting duct are more permeable so water is reabsorbed into blood by osmosis
5. small amount of highly concentrated urine produced and less water is lost
what happens to blood ADH when you’re hydrated?
- ADH levels fall
1. water content of blood rises so WP rises
2. detected by osmoreceptors in hypothalamus
3. posterior pituitary gland releases less ADH into blood
4. less ADH means DCT and collecting duct are less permeable so less water is reabsorbed into blood by osmosis
5. large amount of dilute urine produced and more water is lost
INSERT KIDNEY CARDS HERE !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
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(page 156-157)
what is the CNS?
made of brain and spinal cord
what is the peripheral nervous system (PNS)?
- made of neurones that connect CNS to rest of the body
- made up of somatic and autonomic nervous system
- autonomic system is made up of sympathetic and parasympathetic system
what do the somatic and autonomic nervous systems do?
somatic - controls conscious activities
autonomic - controls unconscious activities
what do the sympathetic and parasympathetic nervous systems do?
sympathetic - gets body ready for action, fight or flight system, releases noradrenaline
parasympathetic - calms body down, rest and digest system, releases acetylcholine
what are the 5 parts found in the brain as part of the CNS?
hypothalamus
pituitary gland
cerbrum
cerebellum
medulla oblongata
what is the hypothalamus?
- found beneath middle part of brain
- automatically maintains body temperature
- produces hormones that control pituitary gland
what is the pituitary gland?
- found beneath hypothalamus
- controlled by hypothalamus
- releases hormones and stimulates other glands to release their hormones
what is the cerebrum?
- largest part of the brain (top)
- divided into cerebral hemispheres
- has a thin outer later (cerebral cortex) that’s highly folded
- involved in vision, hearing, learning and thinking
what is the medulla oblongata?
- base of brain at top of spinal cord
- automatically controls breathing and heart rate
what is tHe cerebellum?
- found underneath cerebrum, also has folded cortex
- important for muscle coordination, posture and coordination of balance
what are reflexes?
- rapid, automatic response to stimuli
- pathway of communication doesn’t involve conscious part of the brain
- avoid damage to the body
what is the blinking refelx?
- body detects something that could damage your eye you automatically blink
- sensory nerve endings in cornea are stimulated by touch
- nerve impulse sent along sensory to relay neurone in CNS
- impulse passed from relay to motor neurones
- motor neurones sent impulses to effectors to muscles that move eyelids
what is the knee-jerk reflex?
- helps maintain posture and balance
- stretch receptors in quad muscles detect leg is stretched
- nerve impulse passes along sensory neurone which communicates directly with motor neurone in spinal cord (no relay neurone involved)
- motor neurone carried nerve impulse to effector in quad muscles causing it to contract so lower leg moves forward quickly
which systems coordinate fight or flight response?
nervous and hormonal systems
how do nervous and hormonal systems coordinate fight or flight?
- when the body is threatened it responds by preparing itself for action (fight or flight)
- nerve impulses from sensory neurones arrive at hypothalamus activating both hormonal and sympathetic nervous system
- pituitary gland is stimulated to release ACTH, causes cortex of adrenal gland to release steroidal hormones
- sympathetic NS is activated, triggering release of adrenaline from medulla of adrenal gland
what effects do the sympathetic system and adrenaline have?
- increase heart rate - blood pumped around the body faster
- increased breathing rate - muscles around bronchioles relax
- glycogen converted to glucose so more glucose available for muscles to respire
- hair stands on end - erector pili muscles in skin contract so makes animal look bigger
how does the nervous system help control heart rate?
- SAN generates electrical impulses causing cardiac muscles to contract
- rate of SAN firing is unconsciously controlled by medulla (in brain)
- animals need to alter their heart rate to respond to internal stimuli e.g. prevent fainting due to low blood pressure
- stimulus detected by pressure and chemical receptors
- electrical impulses are sent to medulla along sensory neurones, medulla sends impulses to SAN along motor neurones
what are pressure receptors?
- baroreceptors in aorta and vena cava
- stimulated by high and low blood pressure
what are chemical receptors ?
- chemoreceptors in aorta, carotid artery and medulla
- monitor blood, CO2 and pH (indicators of O2 levels)
what happens at high blood pressure?
- baroreceptors detect high blood pressure
- impulses sent to medulla, sends impulses along vagus nerve which secretes acetylcholine and binds to receptors on SAN
- effector: cardiac muscles
- heart slows down to reduce blood pressure back to normal
what happens at low blood pressure?
- baroreceptors detect low blood pressure
- impulses sent to medulla, sends impulses along accelerator nerve which secretes noradrenaline and binds to receptors on SAN
- effector: cardiac muscles
- heart speeds up to reduce blood pressure back to normal
what happens at high blood O2, low CO2 or high pH levels?
- chemoreceptors detect changed in blood
- impulses sent to medulla, sends impulses along vagus nerve which secretes acetylcholine and binds to receptors on SAN
- effector: cardiac muscles
- heart slows to return O2, CO2, and pH back to normal
what happens at low blood O2, high CO2 or low pH levels?
- chemoreceptors detect changed in blood
- impulses sent to medulla, sends impulses along accelerator nerve which secretes noradrenaline and binds to receptors on SAN
- effector: cardiac muscles
- heart increases to return O2, CO2, and pH back to normal
how does hormonal system help control heart rate?
- controls HR by releasing adrenaline
- adrenaline binds to specific receptors in the heart
- causes cardiac muscle to contract more frequently and with more force
- heart rate increases and pumps more blood
how can you investigate effect of exercise on heart rate?
- measure heart rate at rest and record in a table
- do gentle exercise and immediately record heart rate
- return to resting position and measure heart rate every minute until back to resting heart rate
how do you analyse the effect of exercise on heart rate using students t-test? (p161 - easier to understand)
- need 2 sets of data
- t-test is used to find out if there’s a significant difference in the means of the 2 data sets (compared on critical value)
1. identify null hypothesis - data in 2 sets will be the same
2. calculate mean and standard deviation for each set
3. use formula to calculate t
4. calculate degrees of freedom ((n1 + n2) - 2)
5. look up values for t in critical value table , if value of t-test is bigger than critical value of 0.05 or less, results are significant so reject null hypothesis
how does the CNS coordinate muscular movement?
- CNS receives sensory info and decides on a response
- if response needs movement, CNS sends signals along neurons to tell skeletal muscles to contract
- skeletal muscle (striated muscle) is the type of muscle you move
what is the structure of a skeletal muscle?
- made of muscle fibres
- cell membrane of muscle fibre is sarcolemma
- bits of sarcolemma fold inwards and stick to sarcoplasm - folds are called transverse tubules and help spread electrical impulses throughout sarcoplasm so reach all parts of muscle fibre
- sarcoplasmic reticulum runs through sarcoplasm & stores and releases calcium needed for muscle contractions
- muscle fibres have lots of mitochondria for ATP needed for contraction
- multinucleate - have many myofibrils made up of proteins & are highly specialised for contraction
what are myofibrils made from?
- thick and thin myofilaments that move past each other
- thick myofilaments: made of myosin
- thin myofilaments: made of actin
what are the dark bands on a myofibril?
- contain thick myosin filaments
- some overlapping actin filaments
- these are called A-bands
what are the light bands on a myofibril?
- contain thin actin filaments
- these are canned I-bands
what is the structure of a myofibril?
- made up of many short units (sarcomeres)
- ends of each sarcomere is marked with a Z-line
- middle of sarcomere is an M-line (is middle of moysin filament)
- around M-line is H-zone which only has myosin filaments
how is muscle contraction explained?
sliding filament model
what is the sliding filament model?
- myosin and actin filaments slide over one another to make sarcomeres contract - myofilaments themselves don’t contract
- simultaneous contraction of many sarcomeres means myofibrils and muscle fibres contract (sarcomere gets shorter)
- sarcomeres return to original shape as they relax
what is the importance of myosin heads?
- myosin filaments have globular heads that are hinged so move back and forth
- each head has a binding site for each actin and binding site for ATP
- actin filments have binding sites for myosin heads (actin-myosin binding site)
- tropomyosin and troponin are found between actin filaments, proteins are attached and help myofilaments move past each other
what happens to the binding sites in resting muscles?
- the actin-myosin binding site are blocked by tropomyosin held in place by troponin
- means myofilaments can’t slide past each other because myosin heads can’t bind to actin-myosin binding site on actin filament
how are muscle contractions triggered by an action potential?
- action potential triggers an influx of calcium
- ATP provides energy needed to move myosin head
- ATP proved energy needed to break the cross bridge
how does an action potential trigger an influx of calcium ions?
- when action potential from motor neurone stimulates a cell, it depolarises sarcolemma, depolarisation spreads down T-Tubules in sarcoplasmic reticulum
- this causes sarcoplasmic reticulum to release stored calcium ions into sarcoplasm
- calcium ions bind to troponin causing it to change shape, this pulls attached tropomyosin out of actin-myosin binding site
- this exposes binding site which allows myosin head to bind
- bond formed when myosin head binds to actin filament = actin-myosin cross bridge
how does ATP provide the energy needed to move the myosin head?
- calcium ions activate ATPase (breaks down ATP into ADP + Pi)
- energy released from ATP moves myosin head, which pulls actin filament along (like a rowing action)
how does ATP provide the energy needed to break the cross bridge?
- myosin head detaches from actinfilament after its moved
- myosin head reattaches to a different binding site further along the actin filament, new actin-myosin cross bridge forms and cycle repeats
- many cross bridges form and break very rapidly and shorten the sacromere + muscle contraction
- cycle continues as long as calcium ions are present and bound to troponin
what happens when excitation stops?
- when muscle stops being stimulated, calcium ions leave their binding sites on troponin molecules and are moved by active transport back into sarcoplasmic reticulum
- troponin molecules return to original shape, pulling attracted tropomyosin molecules with them, means that tropomyosin molecules block actin-myosin binding site
- muscles arent contracted because no myosin heads are attached to actin
- actin filaments slide back to relaxed position which lengthens sarcomere
how is ATP continually generated during aerobic respiration?
- most ATP is generated via oxidative phosphorylation in mitochondria
- aerobic respiration only works when there is oxygen so its good for long periods of low-intensity exercise
how is ATP continually generated during anaerobic respiration?
- ATP made rapidly by glycolysis
- end product is pyruvate which is converted to lactate by lactate fermentation
- lactate can quickly build up in muscles and cause muscle fatigue
- anaerobic respiration is good for short periods of hard exercise
how is ATP continually generated during ATP-creatine phosphate (CP) system?
- ATP made by phosphorylating ADPA (adding phosphate from CP)
- CP stored inside cells and ATP-CP system generates ATP quickly
- CP runs out after few seconds so is used in short bursts of vigorous exercise
- ATP-CP system is anaerobic and is alactic (doesnt form lactate)
explain neuromuscular junctions
- neuromuscular junction = synapse between motor neurone and muscle cell
- use acetylcholine which bind to non cholinergic receptors
- work in same way as synapses between neurones (release neurotransmitter triggering depolarisation in postsynaptic cell)
- depolarisation of muscle cell always causes contraction
- AChE stored in clefts on postsynaptic membrane is released to break down acetylcholine after use
what are the 3 types of muscle?
skeletal muscle
smooth muscle
cardiac muscle
what is skeletal muscle?
- skeletal muscle contraction is controlled consciously
- made of many muscle fibres with many nuclei
- can see regular cross-striations (stripes)
- some muscle fibres contract quickly for speed and strength but fatigue quickly
- some muscle fibres contract slowly for endurance and posture and fatigue slowly
what is smooth muscle?
- involuntary muscle contractions controlled unconsciously
- no striped appearance - smooth
- found in walls of hollow internal organs, and blood vessel smooth muscle contracts to reduce blood flow
- each muscle fibre has one nucleus
- contracts slowly and dont fatigue
what is cardiac muscle?
- contracts on its own (myogenic) but rate of contraction is controlled involuntarily but autonomic NS
- found in walls of your heart
- made of muscle fibred connected by intercalated discs which have low electrical resistance so nerve impulses easily pass between cells
- branched muscle fibres allow nerve impulses to spread quickly
- each fibre has one nucleus
- can see some cross-striations but pattern not as long as skeletal
- contract rhythmically and dont fatigue
how can electrical signals be used to monitor muscle fatigue?
- muscles contract in response to nervous impulses (electrical signals)
- electrical signals can be detected by electrodes placed on skin, electrodes are connected to a computer to allow electrical signals to be monitored (electromyography) and the reading it generates is called an electromyogram
how do plants increase their chance of survival by responding to changes in their environment?
- sense direction of light and grow towards it to maximise light absorption for photosynthesis
- sense gravity so roots grow in right direction
- climbing plants have sense of touch so can climb to reach sunlight
what are 2 examples of plant chemical defences?
alkaloids - chemicals with bitter taste, noxious smell or poisonous characteristics
tannins - taste bitter, bind to proteins in gut making the plant hard to digest
some plants are pheromones. what are 2 examples of pheromones (signalling chemicals that produce response in other organisms)
- some plants release alarm pheromones into air in response to herbivore grazing, causes nearby plants to detect chemicals and make chemical defences e.g. tannins
- when corn plants are being eaten, they produce pheromones that attract parasitic wasps and they lay their eggs in caterpillars and they die
why do some plants fold up in response to being touched?
- helps protect plant against herbivory - knocks off insets, may scare animals trying to eat it
how do some plants respond to extreme colds?
- by producing antifreeze
- carrots produce antifreeze proteins at low temperatures - proteins bind to ice crystals at lower temp than water freezes at so stops more ice crystals growing
what is a tropism?
- the response of a plant to a directional stimulus
- plants respond to stimuli by generating their own growth
- pOsitive tropism is growing tOwards stimulus
- negAtive tropism is growing Away from stimulus
what is a phototropism?
- plants grow in response to light
- shoots are positively phototropic and grow towards light
- roots are negatively phototropic so grow away from light
what is geotropism?
- plants grow in response to gravity
- shoots are negatively geotropic and grow against gravity
- roots are positively geotropic so grow towards gravity
what are the 3 other tropisms (aside from geo and photo)
hydrotropisms - plant growth in response to water - roots are positively hydrotropic
themotropisms - plant growth in response to temperature
thigmotropism - plant growth in response to contact with an object
what are growth hormones?
- plants respond to stimuli using growth hormones
- growth hormones are chemicals that speed up/slow down growth
- produced in growing regions of the plant and move to where theyre needed
what are giberellins?
- growth hormone
- stimulated seed germination, stem elongation, side shoot formation and flowering
what are auxins?
- growth hormone
- stimulate growth of shoots by cell elongation (cell walls become loose and stretchy so cells get longer)
- high conc of auxins inhibits root growth
what is indoleacetic acid (IAA)?
- type of auxin
- moved around plant to control tropisms, moves by diffusion and active transport over short distances, and via phloem over long distances
- this results in different parts of plants having different amounts of IAA
how does IAA act in a phototropism?
moves more to shaded parts of roots and shoots to theres uneven growth
how does IAA act in a geotropism?
moves to underside of shoots and roots so there’s uneven growth
how are auxins involved in apical dominance?
- auxins stimulate growth of apical bud and inhibit growth of side shoots from lateral bud (this is apical dominance - the apical bud is dominant over lateral buds)
- apical dominance prevents side shoots from growing h=which saves energy and saves shoots from same plant competing with shoot tip for sunlight
what is the apical bud?
shoot tip at top of flowering bud
what does apical dominance allow?
- allows plant in an area where there are loads of other plants to grow tall very fast, past smaller plants to reach sunlight
- if you remove the apical bud then the plant wont produce auxins, so side shoots start growing by cell division and elongation
what happens if you replace the tip with a source of auxin?
- side shoot development is inhibited - demonstrates apical dominance is controlled by auxin
- auxins become less concentrated as they move away from apical bud to rest of the plant - if plant grows very tall, bottom of plant will have low auxin conc so side shoots start to grow near the bottom
