Topic 6 - Responce To Environment (no Homeostasis) Flashcards
(133 cards)
1
Q
Neurone structure
A
- cell body - lots of RER to drive activity and energy
- dendrites that pass signals from other neurone to cells body
- axon which is long bit that signal travels down and where action potential takes place
- Schwann cells that produce myelin sheath and increase speed of action potential as it insulate axon.
- myelin sheath that is a fatty insulating layer that allows quick transmitting of electrical impulses - INCREASE ACITON POTENTIAL (no movement of ions through it)
- nodes of ranvier - gaps in myelin sheath coating axon allowing action potential and diffusion of ions in and out of neurone as electrical signal travels down axon
2
Q
What is the resting potential
A
- potential charge -70mV
- sodium - potassium pump (active transport using ATP) moves 3Na+ out of cell membrane and 2K+ into the cell membrane
- higher sodium concentration outside cell
- higher potassium concentration inside cell in axoplasm (cytoplasm)
- potassium ion channel (voltage gated and depended on amount of K+ entering through the SPP) moves K+ out of the cell to maintain the concentration gradient and charge of the membrane (mainly always open)
- more K+ in by SPP, the more K+ diffuses out of the PIC
- resting potential ends when a stimulus is detected
- charge maintained constantly
3
Q
What is the action potential and how is it triggered?
A
- AP triggered by a stimulus that reaches the potential difference threshold.
- this triggers Na+ voltage gated channels to open and allows Na+ to enter the membrane DOWN ELECTRICAL GRADIENT
- more Na+ into the cell causes DEPOLARISATION (change in charge of membrane to more positive and excited inside due to more Na+)
- causes WAVE OF DEPOLARISATION which is the effect of Na+ gradually changing the charge of the membrane as it diffuses across
- ends as +30 is reached causing SVGC to close
- DEPOLARISATION = LESS NEGATIVE MORE POSITIVE
4
Q
What is the refractory period? And when does it start and finish?
A
- RP is when the charge of the membrane is reversed
- closing of Na+ channels triggers opening of K+ voltage gated channels
- at +30 the charge begins to decrease again at K+ channels are opened and Na + channels are closed
- REPOLARISATION occurs as more K+ EXIT the membrane reducing positive charge
- overshoot/hyper-polarisation occurs and exceeds -70 so K+ diffuse BACK IN to retain positive charge to -70 and repolarise.
5
Q
Nerve impulse definition
A
Self propagating wave of electrical disturbance that travels along the surface of the axon membrane.
Temporary reversal of electrical potential difference across axon membrane
6
Q
Myelination
A
- presence of myelin increases speed of action potential along neurone
- formed from Schwann cells
- action potential can’t occur in myelin sheath as it inhibited diffusion of Na+ and K+
- AP happens at NOR
- assists saltatory conduction
7
Q
Saltatory conduction
A
- action potential jumping from one node of ranvier to another
- allows faster travel of signal across membrane
8
Q
What happens at NOR
A
- saltatory conduction
- sodium voltage gated channels open and allow diffusion of Na+ into the membrane
- once in Na+ diffuses across the membrane causing a WAVE OF DEPOLARISATION as it goes, and repolarisaiotn happening behind it as it travels along.
- depolarisation at NOR triggered by AP
- Na+ move along membrane due to low concentration ahead of is so diffuse across
9
Q
What stops diffusion of k+ and Na+ into membrane
A
Fatty layers of myelin sheath and Schwann cells
10
Q
Why can’t Na+ diffuse back and forth along membrane and to where it’s already passed ?
A
- voltage gates now closed and can’t opened again as resting in refractory period
11
Q
All or nothing principle
A
- AP must happen at threshold (-55)
- stronger stimulus means more AP
12
Q
How does axon diameter affect speed of conduction
A
Larger diameter = less resistance and easier flow of ions so quicker conduction
13
Q
How does temp affect speed of conduction
A
- higher temp = more kinetic energy = move faster = AP triggered faster = conduction increased
- to high denatured voltage gated Chanel proteins
- 37 degrees C maintained
14
Q
Sensory reception pathway key terms
A
Stimulus - change in environment
Receptor - cells that detect change
Coordinator - connects information between receptor and appropriate effector
Response - change due to stimulus
15
Q
Taxis
A
- directional
- change causes organisms to more towards or away from
- positive is towards
- negative is away
16
Q
Kinesis
A
- non-directional
- stimulus stimulated general movement
17
Q
Coleoptile
A
Young plant
18
Q
Positive phototropism
A
- IAA concentrates in shaded side of shoot tip
- elongates cells towards light
19
Q
Positive gravitropism
A
- in roots
- auxin on side of gravity (underside)
- cells elongate in direction of gravity where auxin is concentrated
- roots grow downwards
- auxin evenly distributes
20
Q
Negative phototropism
A
- uneven light distribution
- bends away from light
- roots
- IAA on shaded side of root so it grows downwards
21
Q
Negative geotropism
A
- auxin on lower side
- shoot grows up away from gravity
22
Q
Acid growth hypothesis
A
- active transport of hydrogen ions
- from cytoplasm to spaces in wall
- wall stretches under turgor pressure
23
Q
Nervous organisation
A
- CNS = Brian and spinal cord
- peripheral nervous system = pairs of nerves originating form CNS
- voluntary NS = conscious response
- autonomic NS= imposes to glands - voluntary or involuntary
24
Q
Features of IAA auxin
A
- not broken down by light
- moves to shaded side
- produced in tip
- diffuses
- elongates cells
25
What apparatus is used to investigate animal responce
Choice chamber
- 4 different compartments
- investigates light intensity, or humidity
- using wood lice or mill worms
- mesh to prevent them escaping
26
Features of receptors
- cells
- detect one specific stimulus
- can be proteins of cell plasma membrane
27
Charges during resting potential
- different charge inside than outside cell
28
What is al voltage also known as
Potential difference
29
What happens when a stimulus detected
- cell membrane excites
- becomes more permeable
- more ions move in and out
- potential difference altered (generator potential)
- if GP gets to threshold it will trigger and action potential
30
How does the size of the stimulus link to the size of action potentials
- all APs are the same size however, the stronger the stimulus the higher the frequency of action potentials
31
Difference between sensory reception and sensory perception
Reception is role of receptors
Perception is brain processing information.
32
What is the structure of a pacinian corpuscle
- many layers of connective tissue (lamellae) around sensory nerve ending (some gel fluid)
- sensory nerones surround the nerve
- stimulus applied to outside of tissue layers
- in the nerve ending Na+ channels can open to allow Na+ to diffuse in (only at end of nerve ending) ?
- inside membrane is negatively charged compared to outside
- connected to a blood capillary for good blood supply
33
What is pacinian corpuscle
- mechanoreceptor (detect mechanical stimuli)
- found in skin
- when stimulated the lamellae deform and press on sensory nerve ending causing neurones cell membrane to stretch deforming stretch-mediated sodium ion channels
- when channels open and sodium ions diffuse into cell, generator potential is reached
- if GP reaches threshold it generates AP
34
Pupil
Cornea
Iris
Lens
Retina
Optic nerve
Blind spot
Pupil - hole in centre of iris
Cornea - transparent part of sclera that focuses light
Iris - control pupil size and include circular and radial muscles
Lens - long narrow transparent cells, biconcave, 4mm thick, focuses light of retina
Retina - photoreceptors, rods, cones
Optic nerve - axons of ganglion cells
Blind spot - no photoreceptors above optic nerve
35
Aqueous humor
Sclera
Choroid
Fovear
Suspension ligaments
Ciliary muscles
Vitreous humor
Conjunctiva
Aqueous humor - fluid behind cornea
Sclera - tough white connective tissue protects and maintains shape of eye resisting pressure from vitreous humor
Vitreous humor - fluid behind lens
Choroid - rich supply of blood vessels, pigmented epithelium, absorbs light so it doesn’t reflect back
Fovea - cone cells at back of retina
Sus ligs - hold lens to ciliary body
Ciliary muscles - control lens shape
Conjunctiva - protective layer of cells
36
What controls amount of light entering eye
Iris
37
Where do light rays focus
Retina with photoreceptor cells
38
What is rhiodopsin
A pigmant
39
What happens when light enters the eye
- hits photoreceptors
- absorbed by light sensitive optical pigments (on photoreceptor)
- light bleaches pigment and causes a chemical change
- this alters membrane permeability to Na+
- GP created until threshold
- nerve impulse sent along bipolar neurone
-
40
What does bipolar neurone do
- connects photoreceptor to optic nerve which take impulse to the brain
41
Two types of photoreceptors
ROD
CONE
42
Rod cells
- mainly found in peripheral parts of retina
- different optical pigments to cone cells
- only give info in B&W (monochromatic vision)
- very snetive to light
- works well in dim light
43
Why do rod cells work well in dim light
There are many rods joined to one neurone so many weak generator potentials combine to reach the threshold and trigger AP
44
Cone cells
- found packed together in fovea
- give info in colour (trichromatic vision)
- red-sensitive, green-sensitive, blue-sensitive
- less sensitive to bright light
- iodopsin
- highly folded
- lots of mitochondria
- attached to bipolar, then ganglion, then optic nerve = higher resolution and visual acuity
45
Why do cone cells work better in bright light
- one cone joins to one neurone so it takes more light to reach threshold and trigger AP
46
Visual acuity of rod cells
- low
- because many rods join to same neurone meaning light from two points close together can’t be told apart
47
Cones visual acuity
- high
- close together
- one cone t one neurone
- when light from two points hits two cones, 2 APs go to brain
- this allows you to distinguish between two separate points
48
Acuity
Ability to distinguish between two points
49
How many rod cells connected to single ganglion cell
Approx. 100 synaptically connected to single G cell
50
Number of cone cells connected to ganglion cell
Single bipolar cell connected to ganglion cell
51
What is rhodopsin?
- pigment broken down by light
52
What is retinal convergence
number of rod cells connected to a single bipolar cell
- it ensures threshold value is exceeded to create a generator potential in bipolar cell connected
53
Why is colour blindness higher in males
Sex-linked and on X chromosome
54
Autonomic nervous system
Control involuntary/subconscious activities of internal muscles and glands
55
Myogenic
Heart muscle
56
What is SAN
SINOATRIAL NODE
- pacemaker
- generate electrical impulses that contract cardiac muscles
- sets rhythm by sending waves of electrical activity to atrial walls
- located in wall of right atrium
- causes right and left atria to contract at the same time
- transfers waves of electricity to AVS
57
What prevents waves of electrical activity being passed directly from atria to ventricles
Band of non-conducting collagen tissue
58
AVN
ATRIOVENTRICULAR NODE
- passes waves of electrical activity to bundle of HIS
59
60
Why is there a delay before AVN reacts to electrical activity
- to make sure atria is empty before ventricles contract
61
What is bundle of His
- muscles fibres
- conduct waves of electrical activity
- between ventricle and apex (bottom) of heart
- splits into finer fibres in right and left ventricle walls called PURKYNE TISSUE
62
Role of purkyne tissue
- carries waves of electrical activity into muscular walls of right and left ventricles, causing them to contract simultaneously, from bottom up
63
ECG
Electrocardiogram
Electrocardiography
64
Simple process of heart beat
- pacemakers generates wave of signals to contract
- signals are delayed at AV node
- signals pass to heart apex
- signal spread throughout ventricles
65
Synaptic nervous system
- stimulates effectors and speeds up any responce
- occurs during strenuous exercise or heightened emotions
- allows us to cope with stressful conditions by preparing FIGHT OR FLIGHT
66
Parasympathetic nervous system
- inhibitors effect and slow responses
- occurs during normal resting conditions
- allows us to conserve energy and replenish our body reserves
67
What controls rate of SAN
Unconsciously controlled by medulla oblongata in brain
68
Chemical receptors (chemoreceptors)
In aorta
In carotid arteries
In medulla
Monitor O2 level in blood
Monitor CO2 and pH (O2 indicators)
69
Pressure receptors
- baroreceptors
- in aorta and carotid arteries (major arteries in neck)
- stimulated by high and low blood pressure
70
How does electrical impulses get to medulla oblongata
Sensory neurones
71
Role of medulla
Processes information and sends impulses to SAN along sympathetic and parasympathetic neurone (part of autonomic nervous system)
72
What are the two parts to the medial oblongata
- cardio-accelerometer centre - linked to sinotrial node that increases heart rate via SNS
- cardio-inhibitory centre - linked to sinoatrial node decreasing heart rate via RNS
73
How does the heart respond to HIGH BLOOD PRESSURE?
- receptor, neurone and transmitter, effector, and response
RECEPTOR: baroreceptor detect high blood pressure
NEURONE/TRANSMITTER: impulse to medulla along parasympathetic secreting acetylcholine(neurotransmitter), binding to receptors on SAN
EFFECTOR: cardiac muscles
RESPONSE: heart rate flows to reduce BP to normal
74
How does the heart respond to LOW BP?
- receptor, neurone and transmitter, effector, and response
RECEPTOR: baroreceptors detect low BP
NEURONE/TRANSMITTER: impulse to medulla along parasympathetic, secrete noradrenaline which binds to receptors on SAN
EFFECTOR: cardiac muscles
RESPONSE: heart rate speeds and increases BP to normal
75
How does the heart respond to high blood O2, low CO2 or HIGH pH?
- receptor, neurone and transmitter, effector, and response
RECEPTOR: chemoreceptors detect change in blood
NEURONE/TRANSMITTER: impulses along medulla sending impulses along parasympathetic, secreting acetylcholine, which binds to receptors on SAN
EFFECTOR: cardiac muscles
RESPONSE: heart rate decreases to return O2, CO2 and pH levels back to normal
76
How does the heart respond to low blood O2, high CO2 or low pH?
- receptor, neurone and transmitter, effector, and response
RECEPTOR: chemoreceptors detect change in blood
NEURONE/TRANSMITTER: impulses along medulla sending impulses along sympathetic, secreting noradrenaline which binds to receptors on SAN
EFFECTOR: cardiac muscles
RESPONSE: heart rate increases to return O2, CO2 and pH levels back to normal
77
What is a synapse
Junction between two neurones or between and neurone and an effector cell
Gap = synaptic cleft
78
What is the presynaptic neurone
Before the synapse and has swelling called synaptic knob
79
What is the synaptic knob
- swelling on presynaptic cleft
- contains synaptic vesicles filled with chemical neurotransmitters
80
What happens when action potential reaches end of neurone
- neurotransmitters released into synaptic cleft
- diffuse across postsynaptic membrane (one after the synapse)
- bind to specific receptors
81
What happens when neurotransmitters bind to specific receptors
- trigger AP
- muscle contraction
- hormone secretion
82
Resting potential voltage ???
-70mV
83
Threshold value
- 55mV
84
Action potential peak value
30-35mV
85
Purpose of refractory period
- delay between AP which…
1. Limits frequency of impulse transmition meaning too many impulses dont fire at once
2. Produced discrete impulses so they not overlap, but instead are individual and come separately
86
Structure of a synapse
- presynaptic neurone is the one that the signal is traveling from
- the synaptic cleft if the gap
- the postsynaptic cells is the receiver
87
Describe the process of synaptic transmission
- action potential triggers voltages gated
88
What is a discrete impulse
- during resting/refractory period
- action potentials don’t overlap and are separate (discrete)
- limit to frequency
89
Electrochemical gradient
Combined effect of concentration gradient of ions and electrical potential differnce across a membrane
- drives movement of ions
90
Non-myelinated
When axon isn’t insulated and lacking myelin sheath
91
Describe the process of synaptic transmission
- action potential travels down to presynpaitc knob
- triggers voltage gated CALCIUM ion channels to open allowing Ca+ to diffuse into synaptic knob (pumped it after by AT)
- Ca+ causes synaptic vesicles containing neurotransmitter to fuse with presynaptic membrane
- neurotransmitter = ACETYLCHOLINE (ACh)
- ACh released from vestiges to membrane by exosytosis
- ACh diffuses across synaptic clef and binds to specific CHOLINERGIC receptors on the postsynaptic membrane.
- sodium ion channels in PSN open causing depolarisation causing AP if threshold reached
- ACh removed from cleft so response doesn’t keep happening
- ACh broken down by enzyme ACETYLCHOLINESTERASE (ACHE)
- products re absorbed by presynaptic neurone and used to make more ACh
92
Types of neurotransmitters
ACh
Noradrenaline
93
Synapse that uses ACh
CHOLINERGIC synapse
94
95
Excitatory neurotransmitters
- depolarise postsynaptic neurone
- fires action potential if threshold reached
96
Excitatory neurotransmitter example
Acetylcholine at CHOLINERGIC synapse in CNS
- binds to CHOLINERGIC receptors to cause AP in postsynaptic membrane
- and at neuromuscular junctions
97
Inhibitory neurotransmitter
- hyperpolarise postsynaptic neurone
- MEMBRANE NOW MORE NEGATIVE
- prevent AP
98
Example of inhibiting neurotransmitter
- acetylcholine inhibitory at CHOLINERGIC synapse in HEART
- when it binds to receptors in heart, potassium ion channels open on postsynaptic neurone HYPER-POLARISING it
99
What happens when there is a weak stimulus at a synapse
- small amount of neurotransmitter
- not enough to excite postsynaptic membrane
- wont reach threshold
- no AP stimulated
100
What is summation
- neurotransmitter from many neurone (or one VERY stimulated one in short period of time) added together
101
Two types of summation
Spatial
Temporal
102
Spatial summation
Small amount of neurotransmitter released from each neurones can be enough altogether to reach threshold in post synaptic neurone and trigger an action potential
- if some neurones release inhibitory neurotransmitter then no action potential is reached
103
Temporal summation
- depends on frequency
- high frequency of weak impulses triggers action potential
- higher frequency more Na+ released to trigger AP
- low frequency not enough to generate generator potential
104
Sarcoplasm
Cytoplasm of sarcomere
105
Sarcolemma
Cell membrane of sarcomere
106
Proteins/myofilaments in sarcomere
Actin - thin (light)
Myosin - thick (dark)
107
What attaches muscles to bones
Tendons
108
What attaches bones to bones
Ligaments
109
Muscles that work together to move a bone
Antagonistic pairs
110
What are muscles made up of
- large bundles of long cells (muscle fibres)
- muscle fibre made up of myofibrils
111
Components of muscle fibres
- transverse tubules - spread electrical impulses
- sarcolemma
- sarcoplasmic reticulum - internal membranes running through sarcoplasm. Stores calcium ions more contraction
- mitochondria to provide atp
- multinucleate (contain many nucleus)
112
Structure of myofibril
Z lines - ends of sarcomere and join to next sarcomere
H zone - only myosin in middle and reduces during contraction
M line - centre of sarcomere
A band - actin overlapping with myosin (remains the same during contraction)
I band - only actin (reduces in size during contraction)
113
Sliding filament theory
- muscle contraction
- myosin and actin filaments slide over each other
114
What happens at sarcoplamic reticulum to trigger muscle contraction
- action potential travels down it from neurone
- message triggers release of calcium ions .
Signal from neurone ….
To tubules ….
To SR …
Causing release of ions…
Triggers AP
115
What is tropomyosin
- thin filament converting myosin binding site
116
What is troponin
- connected to tropomyosin
- needs calcium ions to bind to it
- calcium ions change its shape
- then changes shape of tropomyosin to expose myosin binding sites
117
Importance of calcium ions in muscle contraction
Must be present for it to take place
- diffuse from sarcoplasmic reticulum and into muscle cell across sarcolemma
- attach to tropomyosin and cause them to change shape
-
118
What happens when the sarcomeres are contracted
- Myosin and actin overlap
- sarcomere gets shorter
119
Muscles contraction summary
- wave of depolarisation across sarcolemma opens Ca+ ions
- ca+ ions diffuse across sarcoplasmic reticulum and also didffuse into muscle cells across sarcolemma
- ca+ attach to troponin and cause shape of tropomyosin to change and twist away from myosin binding sites on actin
- myosin head attach to binding sites to form cross bridges
- cross bridge forming causes myosin to BEND, release ADP+Pi and pull actin
- another ATP attaches to myosin head, changing shape and separating from actin
- ATP HYDROLASE hydrolyses ATP and ADP and inorganic phosphate, straightening myosin = recovery stroke
- head now able to repeat process by attaching to another binding sites and sliding actin along more
120
What triggers calcium ions to be released
- action potential
- from motor neurone
- depolarises sarcolemma and T-tubules to sarcoplasmic reticulum
- calcium channels open
121
What happens when depolarisation of muscles stops
Muscle relaxes
122
Muscle relaxation
- depolarisation stops
- ca+ actively transported to SPR
- tropomyosin back to normal position
- binding sites blocked again
- muscle relaxes and pulled back to position by another antagonistic muscle
123
What is phosphocreatine (PPC)
- molecule stored by muscles
- used for rapid ATP production
- phosphate ion from PPC is transferred to ADP
ADP + PPC -> ATP + creating
124
Function of phosphocreatine
Allows muscles to continue contracting for a short period of time until mitochondria are able to supply ATP
Once used up, muscle contrcsation rate will equal rate of ATP production form an(aerobic) respiration
125
Skeletal muscles made up of slow and fast twitch fibres
126
Slow twitch fibres
- slow contraction for long period of time (endurance)
- not easily fatigued
- slow energy release through anaerobic respiration
- red colour as rich in myoglobin (stores oxygen due to high affinity)
- lots of mitochondria
- lots of capillaries
127
Fast twitch fibres
- fast contraction for long periods of time
- anaerobic (quick release of energy)
- few blood vessels
- low myoglobin (whiter colour)
- low mitochondrial density
- fewer capillaries
- high glycogen - quick release of glucose to generate atp
- quickly tired
128
129
How does the iris reduce in size
Circular and radial muscles in the pupil
- circular contract
- radial relax
130
How do cone cells allow far images to be focused on fovea
Each cone connected to one bipolar/neurone
Each cone sends separate signal
131
132
Crossbridges name
Actinomyosin bridges
133
Recovery stroke
- myosin straightening due to atp - adp+pi
