Topic 6 Flashcards
1
Q
What is a stimulus?
A
Detectable change in internal / external environment of organism which leads uk s response
2
Q
What is a receptor?
A
Sense cells that can detect stimuli
Specific to one type of stimulus
(Pacinian corpuscle,sensory receptors )
(Rods/Cones , light receptors )
(Chemoreceptor in carotid artery)
3
Q
What is a coordinator?
A
Formulates suitable response to a stimulus
Connects effectors and receptors
4
Q
What is an effector?
A
How a response is produced
(Muscles - contract)
(Glands- secret hormones)
5
Q
What is the response pathway?
A
Stimulus-Receptor-coordinators(Nervous system: sensory neurones-brain/spinal cord- relay neurone-motor neurone)- effector-response
6
Q
What are the different communication pathways?
A
Nervous system
Endocrine System (hormones/ glands)
7
Q
What is a taxis?
A
Directional response is determined by direction of stimuli
Respond to environmental changes by moving body away (negative taxis) or towards (positive taxis) favourable stimulus
Chemotaxis: movement towards chemical
Phototaxis: movement towards light
8
Q
What is a kinesis?
A
Non-directional response to a stimuli
Changes its speed or rate of change of direction
If organisms crosses sharp dividing line between favourable and unfavourable conditions, its turning rate increases which raises chances it returns to favourable environment
9
Q
What is tropism?
A
Growth of part of a plant in response to directional stimuli
Plant part grow towards stimuli(positive response)
Plant part grow away stimuli (negative response)
10
Q
What is the tropism of a plant shoot and root?
A
Shoot: positive phototropism and negative gravitropism. So leaves in favourable position to capture light for photosynthesis
Root: negative phototropism and positive gravitropism. Increase roots chances to grow into soil to absorb nutrients
11
Q
What are plant growth factors and its features ?
A
What Plants use to responsed to external stimuli
• They exert their influence by affecting growth .
• made by cells located throughout plant than in particular organ
• some affect tissue that releases them than acting on distant organ
Produced in small quantities
12
Q
What are plant growth factors stimulated by?
A
Light: shoots need to photosynthesis (phototropic response)
Gravity: roots sensitive to gravity , grow in direction of pull (gravitropic response)
Water: plant root grow towards water to absorb it for photosynthesis/ metabolic processes/ support (hydrotropic response)
13
Q
What is IAA?
A
Indoleacetic acid
Belong to auxin group
Control plant cell elongation
14
Q
How does the phototropism response occur in a flowering plant?
A
[positive phototropism]
Cells in tip shoot produce IAA. Is diffused down the chute. When there is light IAA diffuses to dark side. Increasing IAA concentration on dark side. So more elongation on dark side. So shoot tip bends towards light
[negative phototropism]
In roots. high concentration of IAA onto dark/ lower side inhibits growth. So upper/ light side root cells elongate, bending away from light
15
Q
How does the gravitropism response occur in flowering plants?
A
[ positivity Gravitropic]
IAA produced in tip of root, diffuses into shoots & roots. In root, Gravity causes IAA to move from upper side to lower side. Increasing IAA concentration. Inhibiting lower root cells elongation. Upper root cells elongate more than lower root cells. So root bends downwards
[negatively Gravitropic]
Shoots, greater concentration of IAA on lower side, increase lower side elongation greater than upper side elongation. So shoot bends upwards away from gravity
16
Q
How does IAA concentration affect the bending of the shoot and the roots?
A
In shoots, greater IAA concentration increases cell elongation
In root, greater IAA concentration inhibits cell elongation
17
Q
What are the effects of IAA on a plant cell?
A
When taking optimal concentration (shoots take more than roots)
-increases their plasticity (ability to stretch) of their cell walls. For younger cells as older cells are too rigid to elongate
Procces:
• enzyme linked cell wall loosening
-binds to receptors, so protons (hydrogen ions) actively pumped into cell
-so lowers pH of cell (more hydrogen in cell than cell wall)
-expansin enzymes increase placidity of cell wall, allowing water to move into cell to elongate
• acid growth hypothesis: hydrogen ions actively transported from cytoplasm into cell wall spaces so cell becomes more plastic , and elongates.
18
Q
What are features of sensory receptors?
A
-Specific to single type of stimuli
-acts as a transducer. Transduces form of energy into another form of energy
(In nervous system: receptors transduce energy from stimuli into electrical energy as an nervous impulse to create a generator potential )
(Pacinian corpuscle: transduces mechanical energy of stimulus into generator potential
19
Q
What is the structure of a Pacinian corpuscle?
A
Has single sensory neurone at centre. Surrounded by layers of tissue with viscous gel in between
Is in ligaments, tendons, fingers, and soles of feet
In plasma membrane of sensory cell, they contain stretch mediated sodium channels that are permeable to sodium changes when deformed via stretching
20
Q
What is the function of the Pacinian corpuscle? And how does it achieve this?
A
They Respond to mechanical stimuli such as pressure
-resting potential: when sensory neurone is at resting, stretch mediated sodium channels on neurone are too narrow to allow sodium ions to pass them
-pressure is applied, Pacinian corpuscle is deformed, neurone membrane is stretched. Which widens the sodium channels, so sodium diffuses into neurone
-sodium ions change membrane potential, becomes depolarised, and produces generator potential
(If reach threshold value)
-this then creates an action potential. Passing along neurone to central nervous system
-balanced is readdressed by sodium potassium pump
-threshold value stops brain overloading
21
Q
What are light receptors?
A
They transduce light energy into the electrical energy of an nervous impulse
22
Q
What are the features of a rod cell?
A
-light receptor
-can’t distinguish wavelengths of light, meaning images are seen in black and white
-sensitive to low intensity light
-more numerous than cone cells
-distributed at periphery of the retina
-One type
-Generator potential is created from Pigment(rhodopsin) being broken down in rod cell by low light intensity.
-rod cells are connected to a single bipolar cell (retinal convergence) which allows for summation to occur. This Increases the chance the threshold value is reached to create a generator potential
-Low visual acuity: many rod cells are connected to the same bipolar cell. So many rods cells generate a single impulse. So brain can’t distinguish seperate light sources. So resolution is lower
23
Q
What are the features of a cone cell?
A
-provides full colour vision
-cone shaped
-3 types that respond to different ranges of wavelength
-sensitive to high light intensity
-connected to their own bipolar cell. So brain receives individual impulses from each cone. This also prevents summation occurring meaning they only exceed threshold potential at higher light intensities
-has light sensitive pigment (iodopsin). There are 3 different types of iodopsim in each cone cell, that require different range of wavelengths of light to break pigment down.
-good visual acuity: each cone cell connected to bipolar cell. So brain can receive seperate impulses . So can Distinguish the seperate sources of light. Increasing resolution
-less numerous and distributed at periphery . More concentrated at fovea as that’s where lens concentrates most light = fovea Receives higher light intensity
24
Q
What is the autonomic nervous system?
A
Controls involuntary internal glands and muscles activities
Has two divisions: [sympathetic nervous system] [parasympathetic nervous system] which are antagonistic
[antagonistic: if one contracts, then other relaxes]
25
What is the sympathetic nervous system?
-Stimulates effectors
-speeds up activity
-control effectors during strenuous exercise or strong emotions to help us cope in stressful situations
(Prepares us for flight or fight response)
26
What is the parasympathetic / vagus nervous system?
-Inhibits effectors
-slows activity
-controls activities under normal resting conditions to conserve energy and replenish body reserves
27
What does myogenic mean?
Contract initiated within muscle than by nervous impulse from outside (neurogenic)
(Exp: heart muscles)
28
What is the sequence of events that controls the basic heart rate?
-Electrical excitation expands from SAN in right atria accross both atria. So they contract
-layer of non-conductive tissue prevents wave crossing ventricles
-electrical excitation enters into AVN between atria. Sending excitation between ventricles along purkyne tissue compromised of the bundle of His. Which branches into smaller fibres of purkyne tissue at the base of the ventricles
-wave of excitation released from apex of purkyne tissues, so ventricles contract quickly from bottom of heart upwards
(AVN: atrioventricular node)
(SAN: sinoatrial node)
29
How can the basic heart rate be modified?
Through chemoreceptors and pressure receptors (baroreceptors)
Which then change frequency of impulses to the medulla oblongata. That then can either:
• increase the heart rate through the sinoatrial nodes linked to the sympathetic nervous system.
• decrease the heart rate through sinoatrial nodes linked to the parasympathetic (vagus) nervous system
30
What are chemoreceptors?
Found in wall of carotid arteries and aorta (arteries towards brain)
Sensitive to change in pH of blood caused by changes in carbon dioxide concentration.
31
How do chemoreceptors modify the basic heart rate?
-increase in muscular activity. increases respiration. Causing higher blood carbon dioxide levels. Which lowers pH. As carbon dioxide is an acidic gas
-This is then detected by chemoreceptors, which increase frequency of nervous impulses to medulla oblongata
-centre increases frequency of nervous impulse through sympathetic nervous system to SAN-increases electrical waves-increases heart rate
-increases blood flow to remove carbon dioxide gas from blood faster. Returning carbon dioxide levels back to normal.
-So pH of blood rises to normal in carotid arteries. So chemoreceptors reduce frequency of nerve impulses to medulla oblongata. So reduces frequency of impulses to SAN, so the heart rate returns to normal
32
What are pressure receptors?
Sensitive to changes in pressure
(Baroreceptors)
In walls of carotid arteries and aorta
33
How do pressure receptors modify the basic heart rate?
• blood pressure higher than normal: they transmit nerves impulses to centre in medulla to decrease heart rate. By sending impulses to parasympathetic nervous system to SAN to decrease rate heart beats
Blood pressure lower than normal: they transmit nervous impulses to medulla centre, that increase heart rate. By sending impulses to sympathetic nervous system to SAN. That increases rate heart beats
34
What is the nervous system compromised of?
-central nervous system (brain/ spinal cord)
-peripheral nervous system: has nerves, such as the sensory neurone and motor neurone that originate from spinal cord/brain
[The motor neurones can then send impulses to muscles, voluntary, through the voluntary nervous system . Or send impulses to glands/ smooth and cardiac muscle , involuntary through the autonomic nervous system]
35
What is the spinal cord?
-column of nervous tissue that run along back and inside vertebral column
-consists of pairs of sensory nerves entering cord from receptors and motor nerves leaving cord to effectors
-has white matter which is axons? and grey matter which are nervous cells
36
What is a reflex arc?
The pathway of neurones involved in an (involuntary response to sensory stimulus )/(reflex)
Consist of 3 neurones: sensory neurone, coordinator (relay/ intermediate neurone) and motor neurone
37
What are the main stages of a reflex arc?
-stimulus
-receptor
-sensory neurone
-coordinator
-motor neurone
-effector
-response
38
What is a spinal reflex arc?
When one of the three neurones in an reflex arc is in the spinal cord
39
Why is a reflex arc important?
-involuntary: don’t require decisions to be made by brain to make complex responses. So brain isn’t overloaded with impulses. So it only has some impulses being sent to the brain to inform and sometimes override actions
-protection: protects body from harms, effective responses present since birth
-fast: as pathways short, and only involves 1 or 2 synapses. Aswell as there not being any decisions needing to be made
40
How is coordination achieved using the nervous system?
It Uses nerve cells to pass electrical impulses along there length.
They Stimulate target cells by secreting chemicals at the synapse (called neurotransmitters) onto them directly
=Causing rapid communication between specific parts of the organism
(Mostly short lived and restricted to localised body region)
41
How is coordination achieved using the hormonal system?
Produces hormones that are transported in the blood plasma to their target cells.
The target cells have specific receptors on their cell surface membrane. The receptors are stimulated when there is a change in concentrations of hormones
(Causes slower less specific communication form between parts of an organism) but long-lasting and widespread. Also Effects might be irreversible
42
how are neurones structured?
• cell body: contains usual cell organelles (has ER to make neurotransmitters & proteins)
• dendrons: extensions of cell body that subdivide into smaller branched fibres called (dendrites) which carry nerve impulses towards the cell body
• axon: single long fibre that carries impulses away from cell body
• Schwann cells: surround the axon to protect it and provide electrical insulation. They perform phagocytosis to remove cell debris. Plays a role in cell regeneration. They wrap around the axon many times so layers of this membrane build up around it
•myelin sheath: membranes of shawarma cells. Forming a covering to the axon. They are rich in lipid myelin that protects the axon and insulates the electrical impulse
• nodes of Ranvier: constrict between adjacent Schwann cells. Where there isn’t any myelin sheath. These speed up transmission
43
What are sensory neurones?
Transmit nerve impulses from receptor to intermediate/ motor neurone.
Has long dendron that carries impulses to the cell body and an axon that carries impulses away from cell body
44
What are motor neurones?
Transmit nerve impulses from from intermediate / relay neurone to an effector
They have long axon and many short dendrites
45
What are intermediate/ relay neurones?
Transmit impulses between neurones (motor neurones and sensory neurones )
46
What is a nerve impulses?
Self propagating wave of electrical activity that travels along axon membrane
47
What are the different ways movement of ions is controlled across the axon membrane, to help maintain the resting potential?
-phospholipid bilayer: prevents diffusion of polar ions of sodium and potassium across hydrophilic barrier
-channel proteins: span membrane, contain channels. Some are open all the time to allow ions to freely cross by facilitated diffusion. Or some are gated , meaning they can be opened/ closed to allow sodium/ potassium ions to cross by facilitated diffusion when open. (Gates are voltage gates, so respond to voltage changes)
-sodium/ potassium pump: carrier proteins actively transport sodium ions out of axon and potassium ions in using ATP from respiration
48
What are the stages to establishing an resting potential in the axon?
-1) sodium ions are actively transported out of axon by sodium potassium pump
-2)potassium ions are actively transported into the axon by the sodium potassium pump
-3) active transport of sodium ions is greater than that of potassium ions as 3 sodium ions move out for every 2 potassium ions moving in
-4) creating more positive ions outside the axon membrane than inside (making outside positively charged relative to the inside which is negatively charged, despite both ions being positively charged) (NA also greater charge than K) (axon membrane is polarised)
-5)value of PD accros membrane is -65v and called Resting potential as no impulse is transmitted
-6) creates an electrochemical gradient as there is more sodium ions in tissue surrounding axon than inside axoplasm, and more potassium ions in axoplasm than surrounding tissue
-7) so sodium ions try to diffuse back into axoplasm and the potassium ions try to diffuse out axoplasm through protein channel, if there open as they’ll move down a concentration gradient
-8) gated channels for sodium are shut so sodium ions can’t move as easily and a few gated channel are open to let potassium through.
49
What are the stages of transmission of an nerve impulse along an neuron?
Resting potential (polarised)
Action potential (depolarised)
Refractory period (hyperpolarisation)
50
What are the stages for producing an action potential
-1) Membrane starts in Resting state, polarised, inside is negative compared to outside . Some voltage potassium channels are open but sodium channels are closed
-2) sodium ion channels open, some diffuse into axon membrane through channels along electrochemical gradient. Caused by the energy of the stimulus and receptors acting as transducer to create generator potential above threshold value
-3)as sodium ions enter the cell, it become positively charge inside respect to outside. Which triggers a reversal in PD accros axon membrane
-4)potential difference accros plasma membrane reaches 40mV . As it has created an action potential. The voltage gates sodium channels close and the voltage gate potassium channel open
-5) potassium ions diffuse out of cell as some potassium voltage gated channels are open. So more potassium diffuses out. Causing repolarisation of the axon
-6) potential difference overshoots slightly to make cell hyperolised from the outward movement of potassium ions. As Potassium gates close slowly , it cause overshooting negative charge. So original potential difference is restored by sodium/potassium pump as cell returns to resting potential
51
How is an action potential passage created along an unmyelinated sheath?
1) resting potential, establishes an polarised molecule
2) stimulus causes reversal of charge on axon membrane, making axon potential and membrane depolarised as sodium ions enter diffuse out of axon
3) localised electron currents established by influx of sodium ions cause opening of sodium voltage gated channels further along axon. = depolarisation. Behind this region, sodium voltage gated channels close and potassium ones opens. So potassium ions begin to leave axon
4) action potential propagated along axon to next region. Axon at the original membrane has been repolarised from outward movement of potassium ions
5) repolarisation of orignal axon allows sodium allows sodium ions to be transported out, and return to its resting potential . While axon propagates further onward
52
How is passage of an action potential like between myelinated axon?
-myelin sheath acts as electrical insulator, preventing action potential forming
-action potential occurs at breaks in myelinated sheath called nodes of ranvier
-action potential jumps from node to node in procces : saltatory conduction
-occurs faster than in unmyelinated axon as depolarisation isn’t required to occur across entire myelinated axon , only at nodes of ranvier
53
What factors affect the speed an action potential travels at?
-myelin sheath: act as an electrical insulator, prevent action potential forming there. allowing for saltatory conduction to occur. Increasing speed of conductance
-diameter of axon: greater diameter, faster the speed of conduction. As there is less leakage of ions from large axon. So maintains membrane potential
-temperature: higher temperature, faster the impulse as enzymes perform more rapidly at higher temperatures up to a point. Which controls respiration so active transport is possible ( for sodium potassium pump to function)
54
What is the all or nothing response ?
When the size of the stimulus is large enough to trigger a response that meets the threshold value. To initiate the action potential
55
How can an organism perceive stimulus size based on the principle?
-by number of impulses passing at a given time. Larger stimuli, more impulses generated in given time
-having different neurones with different threshold values. Brain then interprets number and type of neurone passing impulses caused by stimuli. So can then determine its size
56
What is the refractory period?
Period after action potential when inward movement of sodium is prevented because the sodium voltage gated channels are still closed.
(In this time it’s impossible for further action potential to be generated)
57
What are the purposes of a refractory period?
-ensures action potential is propagated in one direction: can only move from active region to resting region. Because action potential can’t be propagated in region that’s refractory. So can only move in forward direction
-produces discrete impulses: due to refractory period. New action potential can’t be formed behind first one. stops new impulses being formed behind the first one. Ensures action potentials are separate from eachother
-it limits the number of action potentials: as action potential separated from eachother, limits action potentials that can pass along axon in given time. Limiting strength stimulus can be detected
58
What is the structure of a synapse?
Transmits information from one neurone to another using neurotransmitters
Has presynaptic neurone which releases neurotransmitters. Its axon is called the synaptic knob. Contains many mitochondria and endoplasmic reticulum. THE ER manufactures the neurotransmitters. Neurotransmitters are stored in synaptic vesicles
When neurotransmitters are released from vesicle, they diffuse across synaptic cleft to the post synaptic neurone. That has specific receptor proteins on its membrane to receive it
59
What are the functions of a synapse?
-allow single impulse along neurone to initiate new impulses in a number of different neurones. So single stimulus can create number of simultaneous responses
-allows impulses to be combined at the synapse to allow nerve impulses from receptors reacting to different stimuli to contribute to a single response
60
What are the features of synapses?
-Unidirectional: only pass information (neurotransmitter: acetylcholine) in one direction . Occurs in CNS and muscular joints
-spatial summation: presynaptic neurones release neurotransmitters together to exceed threshold value of post synaptic neurone to trigger new action potential
-temporal summation: single pre-synaptic neurone releases many neurotransmitters over short period, so the concentration of neurotransmitters exceeds the threshold value of post synaptic neurone
-inhibition: prevent impulses from passing to next neurone by not forming an action potential in post-synaptic neurone (not recycle neurotransmitters?)
61
What is the process of an inhibitory synapse inhibiting an impulse?
-pre synaptic neurone releases neurotransmitters that binds to chloride ion protien channels= they open = chloride( negative charge ions) moving in post synaptic neurone by facilitate diffusion
-binding of neurotransmitters causes opening of nearby potassium protein channels= potassium (positive charged ions) moves out
-postsynaptic membrane become more negative and outside is more positive= (hyperpolarisation, so less likely an action potential is created (as high influx of sodium ions would be highly improbable)
62
What is consisted in a cholinergic synapse?
Where neurotransmitters is acetylcholine
Which is hydrolysed by acetylcholinesterase to form acetyl and choline
Common in vertebrae’s (in central nervous system and neuromuscular junctions)
63
What is the process for transmission across a synapse?
-action potential arrives at presynaptic neurone= calcium ion protein voltage gated channels opening. Ions enter synaptic knob by facilitated diffusion.
Ions Cause vesicle to move to pre-synaptic membrane by activating ATP and fuse with it. Releasing acetylcholine into synaptic cleft via exocytosis. Diffusing accros synaptic cleft quickly as diffusion pathway is short
-acetylcholine binds to complimentary receptor site on sodium ion protein channels in post synaptic membrane= channels open= diffuse accross postsynaptic membrane along concentration gradient into post synaptic neurone= action potential being generated In post synaptic neurone
-enzyme acetylcholinesterase binds with acetylcholine into synaptic cleft. Hydrolysing it into choline and acetyl. Which diffuse across synaptic cleft back into pre synaptic neurone (recycling) . Preventing action potential forming in post synaptic neurone, allowing discrete transfer of information across synapse
-ATP is related by mitochondria, then is used to recombine choline and acetyl into acetylcholine. Which is stored into synaptic vesicles= sodium ion channels closing from lack of acetylcholine
64
What is the overall structure of of a skeletal muscle
-made of millions of tiny muscle fibres called myofibrils
-myofibrils are arranged parallel to each other to give maximum force to pull bone
-muscles are composed of myofibrils that are bundled into single fibre, then muscle fibres which are group to form whole muscles that are attached to tendons
65
What is the microscopic structure of skeletal muscle (myofibrils) ?
-Actin: Thinner and consists if two strands twisted around another
-Myosin: thicker, has rod shaped tails with bulbous heads heads projected to the side. Joined tail to tail to give M line
-they contain:
• a Z line: membrane down the middle of actin (distance between Z line is sarcomere)=shorter = contract. Longer relax
• H zone: area where there is myosin only. Move up with actin, narrow in contraction
• M line: myosin only, no overlap with actin
• A (anisotropic. Reflect light) band: is the same width of myosin present, colour can appear darker as actin overlaps myosin
• I (isotropic, absorb light ) band: actin only, narrower during contraction, appear lighter
tropomysoin: forms fibrous strand around actin filament
Troponin: bounds to tropomyosin only actin filament, binds to calcium ions which change shape of troponin. Allow for binding site on actin to be expressed , so myosin heads can attach to them
66
What are slow twitch muscle fibres?
contracts slowly
-less powerful contractions over time
-adapted for endurance work
-common in muscle like calms muscles (contracting constantly to maintains upright body position)
-adapt for aerobic respiration: avoid build up of lactic acid =might= function less as it’s acidic = les enzyme function
-large store of myoglobin, (bright red, molecule stores oxygen , associated with oxygen at low oxygen concentrations
-rich supply of blood vessels
-numerous mitochondria
67
What are fast twitching muscle fibres?
Contract rapidly
-produce powerful contraction for short time period
-for intense exercises
-common in muscles that need short burst of energy (biceps)
-adapted more for anaerobic respiration
-thicker and more myosin muscles
-high concentration of glycogen to supply glucose for America respiration
-high concentration of enzyme involved in anaerobic respiration to provide ATP rapidly
-phosphocreatine store: can generate ATP from ADP anaerobic respiration by donating phosphate to provide energy for muscle contraction
(Fast oxidative fibres , fast glycorgtic fibres
68
What are the feature of a neuromuscular junction?
-point where motor neurone meets skeletal muscle fibre
-many junctions along muscle fibre give rapid powerful and coordinated muscle contraction , which allow simultaneous contraction of fibres
and fast movement for survival
-all muscle fibres supplied by single motor neurone , act together as a single functional unit (motor unit)
=gives control over forces muscle exerts (small force needed, few units stimulated )
69
What is the procces of a neuromuscular junction to stimulate muscle contraction?
-(action potential cause calcium ion channels to open, calcium ions diffuse in, cause ATP releases energy) impulse arrive at junction, cause vesicles to fuse with pre-synaptic membrane and relate acetylcholine into gap
-acetylcholine bonds to receptors on muscle fibre membrane (sarcolemma) = depolarisation as sodium ions diffuse in as channels are open
-Cause’s depolarisation wave that travels down T-tubules
-depolarisation= calcium ion protien channels opening on sarcoplasmic reticulum . So calcium released and diffuses from stores of sarcoplasmic reticulum into muscle cytoplasm
-calcium binds to protein in muscles= contraction (and release energy from ATP)
-acetylcholinesterase in gap breaks down acetylcholine (acetyl, choline) so contraction only occurs when impulse arrives continuously = less bonded to receptors sores= sodium channels close= absorbed into synaptic knob, recombined to form acetylcholine using energy from mitochondria
70
What are the similarities between an neuromuscular junction and cholinergic synapse?
-have neurotransmitters transported by diffusion
-have receptors that bind with neurotransmitter= sodium influx
-use sodium potassium pump to depolarise axon
-use enzymes to break down neurotransmitter
71
What are the differences between a neuromuscular junction and a cholinergic synapse?
NM only excretory whilst CS is inhibitory/ excitatory
Nm link neurones to muscles whilst CS likes neurones to neurones/ other effector organs
Nm only contains motors neurones whilst CS has motor, sensory and intermediate neurones involved
Action potential :
-ends in NM
-new one can be produced in CS
On NM acetylcholine binds to receptors on membrane muscle fibre whilst on CS it binds to post synaptic neurone
72
Why do skeletal muscles occur and act in antagonistic pairs?
(Muscles can only pull not push)
-skeletal muscle contraction will move a part of the skeleton in only one direction. To move the skeletal part in the other direction. Requires a second (antagonistic) muscles. that stretches it partners muscle (that has relaxed). which in Doing so returns the partner muscle to its original state ready for contraction
73
What evidence is there for the sliding filament mechanism when muscle contracts ?
-I-band becomes narrower
-Z lines move closer together
-H zone becomes narrower
-A band remains the same
74
What is the process of the sliding filament mechanism of muscle contraction?
-calcium ions bind to troponin which causes ten tropomyosin molecules that were blocking the binding site on actin filament to pull away and expose myosin sites
-ADP molecules attached to the myosin heads means there in a state to bind to actin filament and form a (myosin actin) cross bridge
-when attached, myosin heads change their shape, pulling actin filament along , then releasing ADP molecule
-ATP molecule attaches to each myosin heads means, it become detached from actin filament
-calcium ions then activate enzyme ATPasd that hydrolyses ATP to ADP that provides energy so myosin heads change their returns to its original position
-then myosin heads with attached ADP molecule reattached itself along actin filament and the *cycle* is repeated as long as calcium ion conc. in myofibrils is high
-as myosin molecules are joined tail to tail, movement of one set of myosin heads is in opposite direction to other set. So actin filaments there attached to move in opposite directions= this pulls actin filaments towards eachother . Shorting distance between Z lines = shorter sarcomere . = shortening of muscle= brings movement to body
75
What is the procces of muscle relaxation?
-stop stimulation = calcium ions actively transported back into sarcoplasmic reticulum using energy from hydrolysis of ATP
-reabsorption of calcium ion= tropomyosin to block actin filament
-myosin head can not bind to actin filament = contraction ceases and muscle relaxes
(This state allows antagonistic muscles to pull actin filament out from between myosin
76
How is energy supplied for muscle contraction?
-aerobic respiration (Kreb cycle, oxidative phosphorylation) (in mitochondria)
-Andearobic respiration (glycolysis only) (in cytoplasm) need lot glucose molecules
Phosphocreatine: a reserve supply for phosphate . That (phosphate) can combine with ADP and so-reform ATP, and can replenish store using phosphate from ATP when muscle is relaxed
(Respiration stages often need greater amount of ATP for contraction than can be delivered (areaobicly as 02 passed in blood is at a slower rate and anerabocsly as not enough glucose)
77
What is homeostasis?
-maintenance of internal environment in a constant state despite external changes
(Internal environment is made up of tissue fluid which bathe all cells and is formed from the blood)
(So if the blood is wrong temp/ph/conc. all cells could be affected
78
Why is homeostasis important?
-enzymes in biochemical reactions are sensitive to pH and temperature changes= reduce rate of reaction (changes structure and bonds) / stop them working (denature?)
-maintain constant blood glucose concentration (water potential) needed to ensure constant water potential to stop cells to shrink and burst from osmosis. & ensures reliable source of glucose for respiration
-organism become more independent to changes in external environment
79
What are the requirements for a control mechanism?
-optimum point: (body temp 37° and blood pH 7.4, point system operates best at)
-receptor: detects any deviations from optimum point
-coordinator: coordinates information from receptors and sends appropriate instructions (area of brain )( hypothalamus for temp control)
-effector: creates changes needed to return the system to optimum point (muscle / gland)
-feedback mechanism: receptors respond to stimulus created by changes to system brought about by effector
80
What are the coordinations of control mechanisms?
*Negative feedback* : procces that brings reversal of any change in conditions. Ensures a steady state can be maintained as the internal environment is returned to its original conditions after change, and [prevents and overshoot] (eg control of blood glucose level)
*Positive feedback* : procces that increase changes detected by receptors (= greater deviations from normal)
81
What are the uses and harms of positive feedback?
Harms: (body temp get too cold)
-so body temp below core temp= enzymes less active= exergonic reactions that release heat are slower= less heat released= cools further= reactions slower = less heat produced = body temp spiral downwards
Usefal: (nerve transmission)
-nerve impulse causes stimulus. Stimuli leads to small influx of sodium-l=increase permeability of neurone membrane= more sodium ions enter =increase and more rapidly ions enter= action potential
82
How do endothermic use negative and positive? feedback to control temp?
-thermoregulation keeps body temp at safe limits (not above 48°C)
-centre in hypothalamus of brain that monitors blood temp and receive info from our skin
-use heat from internal metabolic reactions & use behaviour to regulate body temp
-have wide range of physiological (negative & positive) mechanisms to regulate body temp
To gain heat:
-have body with small SA:V ratio= are large
-vasoconstriction (smooth muscle acts as effectors) diameter of arteries made smaller. So pass beneath the insulating fat layer
-shivering: body muscle undergo involuntary rhythm contractions
-raising hair. Thick layer of still air to be trapped next to skin
-decrease sweating
-metabolic reactions and behavioural mechanisms
To lose heat:
-vasodilation : diameter of arteries near skin surface becomes larger z more warm blood pass closer to skin surface. Heat from blood is radiated away from body
-increase sweating: evaporate water from skin surface requires energy in form of heat . So loses heat as water has high latent heat of vaporisation
-lowering of body hair: hair erector muscle in skin relax. Elasticity causes skin to flatten against body. Insulating Mayer less thick, more heat lost to environment when internal temp is higher than external temp
83
How do endotherms use negative feedback to control temp?
Temp of blood increases above normal 37°
-this is detected by thermoreceptors in hypothalamus of brain
-send more impulses to the heat loss center in hypothalamus
-send impulses to skin (effector organ )
-inititates cooling mechanism (sweating)
-reduction in blood temp
-detected by thermoreceptor = less impulses sent
-body temp returns to normal
84
How do endotherms use positive feedback to control temp?
• when body continuously rises/ falls away from normal
• behavioural responses also requires in extreme conditions
• hypothermia -too cold= die-lack of enzyme activity-MR too slow to keep alive
• hyperthermia -too hot = die = enzyme protien carries denature
(Eg, diseases , typhoid fever can cause breakdown of control mechanisms)
85
How do ectotherms control body temp to stop positive feedback?
gain heat from the environment, so temperature fluctuates with that of environment
-expose themselves to sun (maximum surface area of their body exposed)
-take shelter (reduce heat loss when external temp is low)
-Gain warmth from the ground
86
Why is it advantageous to have separate negative feedback mechanisms to control deviations away from normal?
Gives more homeostatic control, as there are more positive actions in both directions. So allows for homeostasis to be achieved more rapidly and efficiently
(Eg glucagon decreasing lowers blood sugar , but to make it more quicker and reduce its time, insulin also used to lower blood sugar con
87
What are the common characteristics of hormones?
-produced in glands (endocrine glands), that secretes hormones directly into the blood
-carried in blood plasma to the target cells. The cells have specific receptors on their cell surface membrane which are complimentary to a specific hormone (high affinity for hormones)
-they are effective in very low concentrations , but are widespread, and have long lasting affects
88
How is the second messenger model mechanism used to regulate BGC
1- adrenaline binds to transmembrane protein receptor in the cell surface membrane of a liver cell
2-adrenaline bondage causes the protein on the inside of the membrane to change shape
3-the shape change= activation of adenyl cyclase, which converts ATP to cyclic AMP (cAMP)
4-camp acts as a second messenger that binds to protien kinase enzymes, changing its shape and activating it
5-active protein kinase enzyme catalyses conversion of glycogen to glucose , that moves our liver cell by facilitated diffusion into the blood through protein channels
89
What is the pancreas role in regulating blood glucose?
Has Pancreatic cells produce and secrete pancreatic juice into the duct that transports enzymes for digestion into the small intestine
Has islets of langerhan that Produces and secrete hormones. Which contain larger alpha cells that produce glucagon and smaller beta cells that produce insulin
90
What is the role of the liver in regulating blood sugar?
-consists of cells called hepatocytes, that utilizes the hormones to regulate BSL
Include processes :
-glycogenolysis
-gluconeogenisis
(Specifically in the liver)
-glycogengenisis
91
What are the 3 procces required to regulate BSL?
-Glycogensesis: conversion of glucose into glycogen (occurs when BGL high , so liver/muscle cells removes glucose from blood and convert it into glycogen)
-Glycogenolysis: breakdown of glycogen to glucose: low BGL than normal, liver converts glycogen into glucose, that diffuses into blood to restore normal BGL
-Gluconeogenesis: production of glucose from other sources than carbohydrates(glycerol and amino acids) . Occurs when supply of glycogen is exhausted .
92
Why is it important to regulate blood glucose levels?
-cells need constant supply of glucose to use for respiration, (specify brain cells, that only respire glucose
-to maintain an isotonic solution: as if BGL concentration rises to high (hypertonic solution) , it lowers water potential of the blood, so water will move out of cells= shrink (red blood cells ability to transport oxygen is affected). If BSL is too high in cells,( hypotonic solution) water moves into red blood cells = bursts (haemolysis for RBC). So maintains cell shape and no rupture by osmosis
93
What are the factors that influence/ rise blood glucose concentrations?
-diet: glucose is absorbed from hydrolyses of carbohydrates (
-glycogenlysis in liver and muscle cells
-gluconeogensis
94
How does insulin secretion lower BSL and its affects?
body cells have glycoprotein receptors on cell surface membranes that bind to specific insulin molecules:
• tertiary protein structure of glucose transport carrier protein changing , so they open, allowing more glucose into cells by facilitated diffusion
• rise In carrier protein responsible for glucose transport in the cell-surface membrane. From the vesicles that contain these proteins fusing with cell surface membranes from a stimulus of a rise in insulin
•activates enzymes that convert glucose to glycogen and fat
Affects:
-increase absorption rate of glucose into cells (muscle cells particularly )
-increase respiratory rate of cells to use glucose and uptake form blood
-increasing conversion rate of glucose into glycogen
-increase glucose conversion to fat
(Lower blood glucose level= b cells reduce insulin secretion [= negative feedback])
95
how does glucagon increase BSL and its affect?
-attach to specific protein receptors on cell surface membranes of liver cells
-activate enzymes that convert glycogen into glucose (glycogenolysis
-gluconeogenesis
Increase conc. of glucose in blood, returning it to its optimum conc.
(Once raised there will be reduced secretion of glucagon= negative feedback)
96
What is the role of adrenaline in regulating blood glucose levels?
Produced by adrenal glands above kidney
Raise blood glucose levels:
-attach to routes receptors on cell surface membrane
-activate enzymes that cause breakdown of glycogen to glucose in the liver
97
How do hormones interact to regulate blood glucose levels?
Insulin and glucagon act antagonisticly
They are self regulating through negative feedback in response to glucose concentrations in blood. that causes different levels of hormones to be excreted.= glucose concentration fluctuates around optimum point (not constant)
98
What are the types of sugar diabetes ?
• type 1 insulin dependant: body unable to produce insulin. (Usually Begins in childhood). Possibly from autoimmune immune response = Beta cells being attacked. Develops quickly and symptoms are obvious
• type 2 insulin independent: usually due to glycoprotein receptors on body cells lost / unresponsive. Or inadequate supply of insulin from pancrease. Usually develops over age of 40. Caused by obesity and poor diet. Develops slowly. Symptoms are unnoticed. Overweight poeple develops this diabetes.
99
Hows is diabetes controlled?
Type 1 diabetes insulin dependant: injections of insulin (not via mouth due to it being a protein that would be digested in alimentary canal). Injected 2-4 times a day. Insulin must match to glucose intake. Is monitored by biosensors. Exercise and diet management more carefully
Type 2 diabetes insulin independent: controlled by regulating intake of carbohydrate in diet and matching it to exercise taken. & by insulin injections or drugs to lower glucose absorbed from intestine = maintain balance
100
What is Osmoregulation?
-homeostatic control of the water potential of the blood to balance the concentration of salt and water in the blood and prevent movement of water into/ out of cells by osmosis
101
What is the role of the kidney?
-has excretory role to remove urea (produce urine in nephron to remove nitrogenes waste) and homeostatic role (osmoregulation)
102
How is water and salt lost in the human body to help maintain optimum concentration of water and salt?
Water: lost mostly by urine , expired air, evaporation from skin, faeces and sweat
(important to note that some water is also gained by metabolism e.g respiration aside from diet)
Salt: mostly by urine, faeces and sweat
103
What is the structure of the mammalian kidney?
[are 2 kidneys]
-fibrous capsule: outer membrane that protects kidney
-cortex: lighter colored outer region made up of renal/ bowman capsules, convoluted tubules and blood vessels
-medulla: darker colored inner region made of loops of Henle, collecting ducts and blood vessels
-renal pelvis: funnel shaped cavity that collects urine into ureter
-ureter: tube that carries urine into the bladder
-renal artery: supplies kidney with blood from heart via aorta
-renal vein: returns blood to heart via vena cava
(Contains millions of nephrons)
104
What is the structure of the nephron composed of?
Renal (bowman’s capsule): cup shaped and surrounds the glomerulus. Inner layer consists of podocyte cells
Proximal consulates tubule: series of loops surrounded by blood capillaries. Walls made of epithelial cells with microvilli
Loop of Henle: long, hairpin loop which extends from cortex into the medulla of kidney (descending) -> [hair line bend of loop of Henle] and back again (ascending) . Is surrounded by blood capillaries
Distal convoluted tubule: series of loops surrounded by blood capillaries (fewer than proximal). Walls made of epithelial cells
Collecting ducts: tube where lots of distal convulsions tubes from number of nephrons empty. Lines by epithelial cells and increasingly widens as it empties into the kidneys pelvis
-basement membrane (is selective, only allow molecule pass through with less than 69000 relative molecular mass)
105
What are the types of blood vessels associated with the nephron?
Afferent arteriole: tiny vessel that arises from renal artery and supplies nephron with blood. Takes blood to & Enters renal capsule and forms glomerulus. (Wider than efferent)
Glomerulus: branched knots of capillaries which fluid is forced out blood. Recombine to form efferent arteriole
Efferent arteriole: tiny vessel that leaves renal capsule. Has smaller diameter than afferent arteriole. That causes an increase in blood pressure within the glomerulus. Carries blood away from renal capsule
Blood capillaries: they surround proximity/ distal convulsed tubule and the loop of Henle (vesa recta vessel) . Which reabsorb mineral salts, glucose and water. They merge together into venules and further into renal veins
106
How is glumerular filtrate formed by ultrafiltration?
The afferent arteriole causes high hydrostatic pressure to be built up in glomerulus. (As its wide)
This is resisted by the capillary endothelial cells, connective tissue and endothelial cells of blood capillary , basement membrane, epithelial cells on renal capsule, hydrostatic pressure of the fluid in the renal capsule space, lower water potential of blood in the glomerulus (draws some water back into blood as albumen plasma protein create a solute potential)
Contains some modifications that allow certain filtrate through:
-podocytes, have space between them. So filtrate can pass beneath them and through gaps between branches. So filtrate passes between cells than through them
-endothelium of glomerular capillary has pores fluid can pass through
Causing water, glucose and mineral ions( not blood cells, platelets and plasma proteins )to be squeezed out capillary to form the glomerular filtrate.
107
How is glucose and water reabsorbed by the proximal convoluted tubule?
-sodium ions are actively transported out of cells lining the PCT into blood capillaries . Which lowers sodium ion concentration of these cells.
-sodium ions diffuse down a concentration gradient from the lumen of PVT into epithelial lining cells through protien carriers (that carry another molecule (glucose, chloride ions) by facilitated diffusion via co-transport. These then diffuse into the blood. Causing all glucose and other valuable reabsorbed
(85% of water reabsorption of water occurs in proximal convoluted tube) (reabsorbs 50% urea ) (100% glucose/ AAs reabsorbed) (50% water reabsorbed
108
How is the proximal convoluted tubules adapted for selective reabsorption?
Cuboidal Epithelial cells containing:
- micro villi/ villi to increase surface area for absorption.
-base foldings: to give large surface area to transfer transported substances into capillaries
-high density of mitochondria to provide ATP for active transport
-pinocytic vesicles: perform pinocytisis (absorb smaller molecules & protiens (hormones) that filter out?) (is bulk transport of molecules)
-nucleas
-sodium potassium pump
-basement membrane
-endothelial cells
109
How does the loop of Henle perform counter current flow to maintain the water potential gradient [of sodium ions in the medulla]?
(1) sodium ions actively transported out ascending limb into interstitial/ tissue fluid that establishes a low water potential in the fluid
(2) permeable to water, descending limb then transports water out of filtrate by osmosis down water potential gradient, into interstitial fluid (as fluid WP is low). then is transported into the blood capillaries. Which continues till it reaches lowest point on tip of hairpin
(3) at base of ascending limb, sodium ions diffuse out filtrate , then are actively transported as filitrate moves up limb= filtrate increasing in water potential
-[ which creates an water potential gradient between ascending limb and collecting duct, which increases in water potentials as it travels from the cortex down the medulla. So water is continuously transported out filtrate by osmosis from collecting duct into blood vessels as it travels down duct. From the WP in interstial space being lower as ION concentration increase further down medulla ]=[create water literal grandient to transport water out tubule]
110
How is the loop of Henle adapted for counter current flow to maintain water potential gradient?
-ascending limb of Henle: is thin and thick section (thin section diffuses ions accross whilst thick diffuses and actively transports)( permeable to ions but impermeable water) is wider and has thicker walls
-descending limb of Henle: (permeable to water but imperceptible to ions) has thin and narrow walls
111
How are materials reabsorbed in the Distil convoluted tubule and collecting duct to fine tune pH and salt levels of blood?
(Osmoregulation)
Actively transport salt and water into the blood and selecting certain ions to be reabsorbed (by having certain permeability?)
This permeability can be induced by hormonal factors
112
How do hormones provide homeostatic control towards Osmoregulation?
-(1)Osmoreceptors in hypothalamus detect low water potential in blood as it flows over the receptors= lose water, shrink
-(2) hypothalamus then stimulates thirst centres and increases impulses down axons to pituitary gland. The posterior pottery gland releases more ADH (inhibited by alchohol and secreted it into the blood to travel to target cells in nephron
-(3) ADH (primary messenger) binds V2 receptors (glycoproteins) in the collecting duct, and DCT walls. Activating phosphorylase enzyme in the cell which stimulates vesicles with aquaporin channel proteins to fuse with cell surface membrane
-(4) membrane becomes more permeable to water (and urea=more urea secretions), so more water is reabsorbed into the blood= small volumes of concentrated urine which would look dark yellow
113
What reasons might cause water potential in the blood to lower?
-too little water is consumed
-heavy sweating
-lots of ions transported into blood
114
What reasons might cause water potential in the blood to increase?
-large volumes of water being absorbed
-sale used in metabolism/ excreted not being replaced in diet
