Grey Matter Flashcards
1
Q
What are the two components of the nervous system?
A
Central NS:
- brain
- spinal cord (optic nerve)
- integrates information and initiates responses
Peripheral NS:
- motor nerves
- sensory nerves
- connects CNS to limbs and organs
2
Q
What are the two components of the peripheral nervous system?
A
- Efferent NS
- Afferent NS
3
Q
What is the function of the efferent NS?
A
- transmits impulses from CNS to organs, muscles or glands
4
Q
What is the function of the afferent NS?
A
- transmits impulses to CNS from internal organs or from those generated by external stimuli
5
Q
What are the two components of the efferent NS?
A
- somatic
- autonomic
6
Q
What is the function of the somatic NS?
A
- voluntary responses
- stimulate skeletal muscle
7
Q
What is the function of the autonomic NS?
A
- involuntary responses
- cardiac muscles
- smooth muscle and glands
8
Q
What are the components of the autonomic NS?
A
- Parasympathetic NS
- Sympathetic NS
9
Q
What is the function of the parasympathetic NS?
A
- fight and flight
- increased heart rate, pupil constriction, bladder contraction
10
Q
What is the function of the sympathetic NS?
A
- ‘rest or digest’
- decreases heart rate, pupil dilation, bladder relaxation
11
Q
What is the CNS protected by
A
- bone and meninges
12
Q
Is the PNS protected?
A
No
13
Q
What is sciatica
A
- pinched nerve
14
Q
What is the function of neurons?
A
- generate and carry nerve impulses
15
Q
What are the neurons in the CNS?
A
Relay neurons in the brain
16
Q
What are the neurons in the PNS?
A
- motor
- sensory
17
Q
What are neuroglia?
A
- provide structural and support for neurons
18
Q
What do neuroglia in the CNS look like?
A
- astrocytes
- microglia
- oligodendrocytes
19
Q
What do neuroglia in the PNS look like?
A
- Schwann cells
20
Q
What does it means when a neuron is multipolar?
A
- many dendrites branching from cell body, long axon
- motor neurons
21
Q
What does it mean when a neuron is bipolar?
A
Dendron and axon arising from the cell body
22
Q
What does it mean when a neuron is unipolar?
A
- dendron and axon arise from a stem in the cell body
23
Q
What are motor neurons?
A
- transmit nerve impulses to muscles or glands
- cell body located in the CNS
- axon extends out of the CNS
- can be very long
24
Q
What are sensory neurons?
A
- carry nerve impulses from sensory cells to CNS
- cell body and dendron outside CNS
- cell body found in dorsal root ganglia
- axon extends into CNS
25
What are the function of relay neurons §
- connect sensory neurons with motor neurons
- mostly found in CNS
26
What are Schwann cells -
- neuroglia
- progressively wrap themselves around axons producing a spiral layer of membrane
- protect neurons from damage and speed up transmission of nerve impulses
27
What is a nerve?
- in the PNS a nerve is a bundle of nerve fibres
- in the CNS analogous structures are known as nerve tracts
28
How do nerves supply plentiful glucose and oxygen to neurons?
- they contain blood vessels
- surrounded by fluid which act in a similar way to cerebrospinal fluid in the CNS
29
What are the three nerve types?
- afferent
- efferent
- mixed
30
What are the functions of afferent nerves?
- conduct impulses from sensory neurons to the CNS
31
What are the functions of efferent nerves?
- conduct impulses from the CNS along motor neurons to muscles and glands
32
What are the functions of mixed nerves?
- contain both afferent and efferent axons, conduct incoming sensory information and outgoing muscle commands in the same bundle
33
A reflex is an…
Immediate, involuntary response to a stimulus
34
Which type of neurons cell body is not found in grey ,after
Sensory neurons
35
Why is white matter white?
Lots of myelin sheath
36
What is a reflex arc?
- a neural pathway that controls a reflex
37
Why are reflexes almost immediate?
- sensory neurons synapse with relay neurons in the spinal cord rather than passing impulses directly to the brain
- brain receives sensory input while reflex is being carried out, analysis takes place after initiation of the reflex action.
38
What are the two types of reflexes?
Autonomic:
- reflexes that involve inner organs
Somatic:
- reflexes that involve skeletal muscle
39
What is the simplest reflex arc?
- monosynaptic
- involves only one sensory neurons and a motor neuron
40
Most reflex arcs are…
Polysnaptic
- one or more interneurons synapse with sensory and motor neurons ( this allows processing of the reflex in the brain with short delay)
41
Describe the patellar reflex
1. when the patellar tendon is tapped an AP is initiated in a muscle spindle in the quadriceps
2. the muscle spindle is a stretch receptor and detects the change in muscle length and sends impulse to the CNS
3. the impulse is propagated in a sensory neuron which releases glutamate at a snap yes with a motor neurons in the CNS
4. The result is extension of the quadriceps whcih causes the contraction of the lower legs
42
How is the hamstring relaxed in the patellar reflex
- the sensory input from the quadriceps also activates interneurons that release the inhibitory neurotransmitter glycine at synapses with the motor neurons of the hamstring muscle, blocking their contraction
- facilitates extension of the lower legs
43
What are the advantedges of reflex arc pathways?
- they produce rapid responses, important for survival and protection
44
Describe the nerve pathway involving picking up a hot dinner plate
- thermoreceptors in skin generate AP which are then propagated along sensory neurons
- these synapses with interneurons and neurons in the CNS
- motor neurons stimulate skeletal muscles to move body to safety
- Brain processes response
45
What portion of the autonomic NS does pupil dilation involve?
Sympathetic
46
What portion of the autonomic NS does pupil constriction involve
Parasympathetic
47
Describe muscle changes in dim light
- radial muscles contract
- circular muscle relax
48
Describe muscle changes in bright light
- circular muscles contract
- radial muscles relax
49
What is a consensual reflex?
- a response observed on both sides of the body when one side has been stimulated
50
Why does a consensual reflex happen within pupil dilation and constriction?
- sensory impulses in the optic nerve stimulate motor impulses in both the left and right oculomotor nerves
51
What is a nerve impulse?
- an action potential propagated in one direction along an axon as a wave of depolarisation
52
What is an AP?
Sudden reversal of membrane potential from -70 to 140 back to -70 in response to a stimuli’s
53
What is resting potential?
- the concentration potential of a neuron at rest
- inside is more negative
- -70mV
54
In resting potential the Na+/K+ creates a concentration gradient by…
Pumping 3 Na+ out and pumping 2 K+ in
55
In resting potential which channels are closed and which are open?
- K+ channels are open so they can diffuse out of the cell along the concentration gradient
- Na+ channels are closed so Na+ cannot diffuse into cell
56
How is equilibrium established in resting potential
- electrical charge builds up outside of cell
- some K+ are attracted back into the cell due to the positive gradient
- K+ concentration gradient and electrical gradient counteract each other
57
What are the five stages of an AP?
1. Resting potential
2. Depolarisation
3. Repolarisation
4. Hyper polarisation
5. Return to resting potential
58
Describe depolarisation
- Stimulus causes change in shape of voltage gated Na+ channels, opening them
- Na+ diffuses into axon along electrochemical gradient, leading to depolarisation of the membrane
59
Describe repolarisation
- voltage gated Na+ channels close
- voltage gated K+ channels open, K+ ions diffuse out of axon due to electrochemical gradient
60
Describe hyperpolarisation
- with voltage gated K+ channels open, membrane is more permeable to K+ ions, leading to hyperpolarisaiton
61
Describe the return to resting potential
- voltage gated K+ close
- non-voltage gated K+ channels still open so K+ diffuses back into axon
- Na+/K+ pump helps restore na+ and K+ cones
62
What is the refractory period?
The time after an AP when the membrane cannot react to a new stimulis
63
Why is there a refractory period?
- creates an upper limit to frequency of nerve impulses
- ensures nerve impulses only propagate in one direction
64
A stimulus must cause depolarisation to a threshold of…
-55 to -50 to generate an action potential
- A stimulus either triggers a full AP or not at all
65
Why may a weak stimulus not cause an AP?
- a small number of voltage-gated Na+ channels open causing a insufficient depolarisation
66
At a threshold…
More voltage gated Na+ channels open and an AP is generate
67
Describe the nature of a nerve impulse
Non-decremental
- the size of the action potential is always the same
- stronger stimuli do not trigger higher APs but do increase the frequency of APs
68
How does stronger stimuli causes an increase in the strength of electrical activity overalll?
- increases the number of neurons conducting impulse in a nerve
69
Explain why the electrical activity of nerves is increased by stronger stimuli
- frequency of APs increases in individual neurons, not the size of depolarisation
70
How is an AP propogated along an axon?
- At the site of the AP, the membrane has the opposite electrical charge to the adjacent resting membrane
- +ve ions are attracted to the -ve area creating a local electric current
- this depolarises the resting membrane generating an AP as voltage gated channels open
71
What ensures that nerve impulses only propagate in one direction
- Na+ channels that had previously been open cannot open again due to the refractory period
72
What are the factors that affect the speed of nerve impulse conduction
- diameter of axon
- myelination
- temperature
- concentration of Na+ ions in tissue fluid
73
How does the diameter of an axon affect the speed of nerve impulse conduction?
- the greater the diameter of axon the faster the speed of propagation of the nerve impulses (less resistance)
74
Why does an increase in temperature increase the speed of nerve impulse conduction?
- higher rate of diffusion of ions due to higher kJ
75
Why does a reduction of Na+ conc in tissue fluid slow down conduction speed?
- increases time for formation of APs
76
What is saltatory conduction?
- when an impulse jumps from node of ranvirt to node as APs cannot form where myelin is present
77
What is a synapse?
- a tiny gap across which a nerve impulse passes from one neuron to another
78
What is the first stage of synaptic transmission
1. A nerve impulse is propagated along the axon of the presynaptic neuron towards the synaptic bulb
2. Ca2+ channels in presynaptic membrane open, membrane becomes more permeable. Ca2+ from the tissue fluid diffuses into presynaptic bulb.
3. Vesicles containing neurotransmitters move to and fuse with presynaptic membrane. Neurotransmitter is released into synaptic cleft by exocytosis.
79
What is stage 2 of synaptic transmission?
1. Neurotransmitters diffuses across synaptic cleft (synaptic delay)
2. Neurotransmitter binds to receptor and stimulates opening of Na+ channels in post synaptic membrane.
3. Entry of Na+ depolarises the postsynaptic bulb (=excitatory postsynaptic potential EPSP.) If EPSP is large enough to reach threshold an AP is stimulated and a nerve impulse is propagated along dendrite
80
What is stage 3 of synaptic transmission?
1. Neurotransmitter is broken down, products cannot bind to the receptors
2. Products travel back to presynaptic membrane and taken up by endocytosis
3. Neurotransmitter is re-synthesised and stored in vesicles ready for next impulse
81
What does it mean when a synapse has unidirectionality
- synapses ensure impulse only transmitted in one direction
82
How does a synapses protect from overstimulation?
- recycling of neurotransmitter
83
How do synapses filter?
- low-level stimuli only cause a small amount of neurotransmitter to be released so no impulse is generated
84
How do synapses form neural networks?
- convergence and divergence
85
What are the two types of synapses?
- excitatory synapses
- inhibitory synapses
86
How do excitatory synapses work?
- stimulate Na+ channels to open causing depolarisation (EPSP) and therefore transmission of a nerve impulse
87
How do inhibitory synapses work?
- stimulate K+ or Cl- channels to open causing hyper polarisation (an inhibitory postsynaptic potential) and therefore blocking transmission of a nerve impulse
88
What is summation
- occurs when several impulses arrive at a synapse
- this can cause an EPSP above threshold that generates an AP in postsynaptic membrane
89
What are the two types of summation
- spatial (impulses from several different neurons)
- temporal (several impulses from the same neuron)
90
What is acetylcholine?
- the most common neurotransmitter
- cholinegeric nervers
- synthesised in the synaptic bulb using ATP
- degraded on post-synaptic membrane by acetylcholinesterase
91
What is a neuromuscular junction?
- specialised synapse between motor neuron and skeletal muscle
- nerve impulse here stimulates muscle contraction
- sarcolemma and motor end plate = postsynaptic membrane
92
93
What is the type of transmission within the nervous system and the endocrine system?
NS:
- electrical (nerve impulses) + chemical (synapses)
Endocrine:
- chemical
94
What is the method of transport within the NS vs the ES
NS:
- neurons synapse with specific cells
ES:
- blood carries hormones to target cells
95
What is the speed of response within the nervous system and endocrine system?
NS:
- fast acting
ES:
- slow acting
96
Is the nervous or endocrine system long term response?
Endocrine generates longer term responses
97
What is the site of responses within the NS and the ES?
Nervous system:
- often very localised
Endocrine system
- often widespread
98
Describe the three types of hormones?
- protein
- steroidal
- amine
99
How are protein hormones released from cells?
- exocytosis
100
What is a target organ?
- an organ with receptors for a particular protein
101
What are secondary messengers?
- molecules (e.g cyclic AMP) which actives or inhibits enzyme pathways
102
When do hormones use secondary messengers? -
When they bind to a cell surface receptor
103
What is a hormone-receptor complex?
- when hormones enter cells and bind to a receptor in the cytoplasm
- hormone-receptor complex moves to nucleus where it binds to DNA affecting transcription
104
How do plants coordinate responses?
- using plant growth substances
105
What are plant growth substances?
- chemicals produced in plant at low concentrations and transported to the part of the plants where they produce a response
- often involved in tropism
106
What is tropism?
- growth responses of a plant to a directional stimulis
107
What is the response of shoots and roots to phototropism?
Shoots:
- grow towards light source (positive)
Roots:
- mostly none or away from light (negative)
108
What are shoots and roots responses to geotropism?
Shoots
- grow away from gravity (negative)
Roots:
- grow towards direction of gravity (positive)
109
What is the response of shoots to hydrotropism?
none
110
What is the response of roots to hydrotropism?
- positive
111
What is the name o a plants response to touch?
Thigmotropism
112
What a shoots responses to touch?
Grow towards and bend around a support (positive)
113
What are roots responses to touch?
- grow away from the object (negative)
114
What did Darwin’s experiment on coleoptiles show?
- the tip of the shoot detects light
- coleoptile does not show bending when tip is removed or covered
115
What did Boyson + Jensen experiment on coleoptiles show?
- the chemical that stimulates growth is water soluble
116
What did Wents experiment on coleoptiles show?
- chemical (from agar) diffuses from tip to growth zone
- stimulating growth
117
What is auxin?
- IAA
- hormone responsible for phototropism
118
What is meristem tissues?
- areas of plant growth
- undifferentiated with a high rate of mitosis
119
What is the effect of a low concentration of IAA on plants?
- root growth is stimulated
- shoot growth is not affected
120
What is the effect of a high concentration of IAA on plants?
- Shoot growth is stimulated
- root growth inhibited
121
Is IAA concentration constant throughout the plant?
- when plant is growing, roots have a low concentration of IAA and shoots have a high concentration
122
What are the three stages of growth in shoots and roots?
1. Cell division in meristem
2. Elongation
3. Maturation
123
Describe auxin action
- auxin is produced in the shoot tip
- it diffuses down the shoot tip
- auxin is destroyed by light - auxin accumulates on the shaded side causing cell elongation
- plant bends towards light
124
Describe cell elongation:
- auxins are synthesised in meristem cells
- auxins diffuse from the tip
- auxins bind to receptor sisters, activating hydrogen ion pumps in cell membranes
- low pH of cell walls keeps them flexible allowing cells to expand as they absorb water
- auxins are destroyed by enzyme, causing cell walls to become rigid. No more elongation
125
What are the other functions of cell elongation?
- inhibit growth of side branches
- stimulate lateral root growth
- fruit development
- leaf fall
126
What are the uses of synthetic auxins?
- herbicide (rapid growth and death)
- fruiting
- root formation
127
What is the site of production for plant growth substances?
- meristem tissues
128
What is the mode of transport for plant growth substances?
- cell to cell by diffusion or via vascular tissue
129
How do plant growth substances affect functions within a plant?
- affect gene transcription or enzyme activity
130
How do plant growth substances affect functions within a plant?
131
What are receptor cells? -
- cells that are sensitive to a particular stimulus
132
What are sense organs?
- organs that contain groups of specialised cells
133
What are the receptors within an eye?
- photoreceptors
134
What are the receptors within an ear?
Mechanoreceptors
135
What are the receptors within a nose and a tongue?
- chemoreceptor
136
What are the receptors within skin
- mechanoreceptor
- thermoreceptor
137
What are primary receptors?
- neurons with dendrites sensitive to a particular stimulus
138
What are secondary receptors?
- one (or more) receptor cells which are sensitive to a particular stimulus and which synapse with a normal sensory neuron
139
How do receptor cells function?
- a stimulus causes a hyperpolarisation or depolarisation of the receptor cell membrane resulting in a generator potential
140
What is a generator potential
- change in potential difference across a receptor cell membrane
141
Does generator potential size change with stimulus size?
Yes
142
How is generator potential linked to action potential?
- when a generator potential reaches the threshold of the sensory neurone an action potential occurs
143
What is the cornea?
- Clear covering of the eye
- refracts and focuses light
144
What is the lens?
- transparent structure behind pupil
- refracts and focuses light
145
What is the pupil?
- hole in the centre of the iris
- controls the amount of light entering the eye
146
What is the iris?
- pigmented tissue, sphincter
- controls the amount of light entering the eye
147
What is the sclera?
- white outer layer of eye
- protective layer
148
What is the conjunctiva?
- covering over the cornea
- protects cornea
149
What are suspensory ligaments?
- connect ciliary muscle and lens
- involved in controlling accommodation (focusing)
150
What are ciliary muscles?
- ring of muscle connected to lens via suspensory ligaments
- controls focusing by altering thickness of lens
151
What is the retina?
- inner layer of eye containing rods and cones
- responds to light stimulus
152
What is the optic nerve?
- sensory nerve (part of CNS)
- carries nerve impulses from retina to brain
153
What is the blind spot within the eye?
- no light sensitive cells where optic nerve leaves the eye
154
What is the fovea?
- most light sensitive part of the retina
- helps with central vision
155
What is the chorad?
- black layer behind retina
- prevents internal reflection of light
156
What is the vitreous humour?
- clear gel that fills eye and keeps retina in place
157
Describe how the retina processes light?
1. Light enters eye and is focused on the retina which contains photoreceptors (rods and cones)
2. Photoreceptors trigger chemical change which generate electrical signals
3. Signal is transmitted to bipolar cells (1:3 bipolar cell to photoreceptor in order to reach threshold)
4. Signal is passed on to ganglion cells which is passed on to optic nerve
158
What care rods used for?
- dim light vision
159
What are cones used for?
- colour vision
160
What is the chemical within rod cells?
Rhodopsin
161
What is the chemical within cone cells?
Iodopsin
162
What is rhodopsin made of?
Opsin + retinal
163
Describe the pathway of how photoreceptors respond to stimuli
1. Light
2. Photoreceptive pigment activated
3. Bipolar cell activated
4. Ganglion cell activated
5. Nerve impulse to brain via optic nerve
164
Photoisomerisation of retinal triggers…
- Shape change
- Cis retinal + opsin is dark adapted
- with light it is changed to trans retinal
- trans retinal cannot bind to opsin
- leading to bleaching (breakdown of rhodopsin)
- opsin is now light adapted
165
How are rod cells activated in the dark?
- cisretinal is bound to opsin
- transducin inactive
- Na+ channel open
- Na+ is pumped out but diffuses back in -> inside of the cell vis negative (polarisation)
166
How are rod cells activated in light
- transretinal is not bound to opsin
- transducin is open
- Na+ channel closed
- Na+ is pumped out but cannot diffuse backi n
- inside cell is much more negative (Hyperpolarisation -> AP)
167
Does being in the dark stimulate inhibition or excitation of a nerve impulse?
- inhibition
- polarisation causes more neurotransmitter to be released (glutamate)
- bipolar + ganglion cells not depolarised
- no nerve impulse
168
Does being in the light stimulate inhibition or excitation of a nerve impulse?
- hyperpolarisation causes less neurotransmitter to be released
- bipolar + ganglion cells depolarised
- nerve impulse generated
169
How many types of cones are there?
- 3
- each with a different form of iodopsin that respond to a particular wavelength of light
170
What is trichromatic vision? -
- colours are seen due to combinations of impulses from the three cone types
171
What is monochromacy
- total colour blindness
- only rods or only one type of functional cone
172
What is dichromacy?
- two types of functional cone
173
What is anomalous trichomacy?
- three types of functional cone but one type may be mutated and less sensitive
174
Describe rods in daylight
- Almost all rhodopsin is broken down
- in the dark rhodopsin is re synthesised and rods are sensitive again
175
Describe cones in daylight vision
- iodopsin is less easily broken down by light and can be resynthesised in light
176
Describe rods during night vision
- convergence
- spatial summation
- threshold reached in bipolar cells and AP stimulated
- impulse via optic nerve to brain
177
Describe night vision in cones?
- no convergence
- no spatial summation
- threshold not reached in bipolar cells
- AP not stimulated
- light impulse via optic nerve to brain
178
What photoreceptor does daylight vision use?
- cones
179
What photoreceptor does nighttime vision mainly use
Rods
180
Why are rods ore sensitive to low light than cones?
- convergence and spatial summation allows a impulse down a signal neuron to the brain
181
Why do rods have lower acuity than cones?
- convergence
182
What is photoperiodism
- the response of an organism to a length of daylight
183
What are examples of photperiodic processes in plants?
- flowering
- leaf growth
- seed germination
- chlorophyll synthesis
- tuber + bulb formation
184
What are forms of photoperiodic processes in animals?
- colour changes in fur or feathers
- migration behaviour
- hibernation
- mating behaviour
185
What are phytochromes?
- proteinaceous pigments that allow plants to detect light
Pf (cis isomer) and Pfr (trans isomer)
186
What light does Pf absorb?
Red light
187
What light does Pfr absorb?
- far red light
188
What happens to Pfr at night in darkness?
- slowly converted to Pr
189
What happens in sunlight
both conversions happen but Pr to Pfr dominates so Pfr accumulates
190
Describe flowering in long day plants
- Requires short nights
- less Pfr converted into Pr during short nights
- Pfr needed to stimulate flowering
191
Describe flowering in short day plants
- require long nights
- all Pfr converted into Pr during the night
- Pfr inhibits flowering q
192
What does it mean if a plant is day neutral
- flowering is not stimulated by photoperiodism
- flowering occurs at a certain developmental stage or age, or in response to an environmental stimulus
193
How is germination controlled by light?
- red light stimulates germination (high Pfr levels)
- far red light inhibits germination (low Pfr levels)
- reversible, final light exposure determines outcome
194
Exposure to red light causes…
Conversion of Pf to Pfr
195
Exposure to far red light causes
Pfr converted to Pr
196
What is greening
Changes that plants undergo after the shoot has broken through soil into light
- production/unrolling of leaves
- chlorophyll production
- inhibition of elongation of internodes
197
What is the phytochrome action within greening?
- red light stimulates greening (high Pfr)
- far red light inhibits greening (low Pfr)
198
What is etiolation?
- plants grow rapidly in darkness
- they quickly use up the seeds food store to reach light
- tall thin plants
199
How does phytochrome signalling work?
Activation of a signal transduction pathway leading to transcription of genes involved in flowering germination and greening
200
What is signal transduction
- the process by which a stimulus results in a cellular response
201
What is the brain the main coordinating response for?
- recovering information from receptors
- interpreting information
- transmitting information to effectors
202
What is the cerebrum?
- site of higher functions (cerebral cortex)
- consists of two cerebral hemispheres
203
What is the corpus callosum?
- connects the two cerebral hemispheres
- broad band of white matter (myelinated axons)
204
What is the function of the thalamus?
- routes incoming sensory information to correct part of brain via myelinated axons
205
What is the function of the hypothalamus?
- thermoregulatory centre
- controls sleep, hunger thirst
- acts as endocrine gland
- connects to pituitary gland
206
What is the function of the basal ganglia?
- neurons at the base of the forebrain responsible for selecting and initiating stored programmes for movement
207
Describe the structure of the cerebral cortex
- contains cell bodies, synapses, dendrites
- highly folded
- composed of four lobes
208
1. Frontal lobe
2. Parietal lobe
3. Occipital lobe
4. Temporal lobe
209
What is the frontal lobe
- conscious area of brain, forming associations
- decision making, reasoning
- emotional response
- includes motor cortex -> movement
210
What is the function of the parietal lobe?
- orientation, movement
- sensory cortex -> sensation
- calculation
- recognition and memory
211
What is the function of the occipital lobe?
= visual cortex
- vision, colour, shape recognition, perspective
212
What is the function of the temporal lobe?
- procession auditory information
- hippocampus = memory
213
The midbrain, along with the thalamus, relays information for vision to the ………… lobe and hearing to the ………….. lobe
1. Occipital
2. Temporal
214
What is in the hindbrain?
- cerebellum
- medulla oblongata
- pons
215
What is the function of the cerebellum?
- coordination of smooth precise movements
- controls balance and posture
216
What is the function of the medulla oblongata?
- controls heart rate, blood pressure, breathing rate…
- cranial reflexes
217
What is the function of the pons?
- involved in sensory and motor analysis
- involved in consciousness and sleep
218
What are the meninges?
=Membranes around brain
- provide protective cushion
219
What are the ventricles (in the brain)
- produce centrospinal fluid
- acts as a protective cushion
220
What is a CT scan?
- computerised axial tomograph
- uses X rays which are passed through body area
- x rays are reduced in strength by density of tissue
221
What are the pros of CT scans?
- used to detect brain diseases
- quick
222
What are the cons of CT scans?
- produces frozen moment pictures only
- looks at structure rather than function
- harmful
223
What is an MRI?
Magnetic resonance imaging
- uses magnetic fields and radio waves to image soft tissues
224
What is are the pros of MRI?
- fine detail of soft tissues seen
- no radiation risk
- detects tumours,strokes, injuries
225
What is are the cons of mri?
- produces frozen moment pictures only
- takes 30 mins
- have to lie very still
- exspensive
226
What are fMRI scans?
Functional magnetic resonance imaging
- MRI procedure that measures brain activity while people carry out different tasks
- monitors flow of oxygenate blood in the brain
227
What are the pros of fMRI?
- can be used to analyse brain activity
- high resolution images
- no risk of radiation
228
What are the cons of fMRI?
- monitors blood flow but not neuron function
- noisy
- lie very still
229
What’s is a PET scan?
- radioactively labelled O2 injected
- moves to metabolically active areas of the brain
230
What are the pros of PET scans?
- can be used to analyse brain disease
- patient movement does not matter
231
What are the cons of PET scans?
- resolution not as clear as fMRI scan
- harmful
- expensive
232
What is binocular disparity
- each eye views a slightly different image due to having slightly different positions in the head
233
What is binocular disparity used for?
- by the visual cortex to calculate depth
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What allows us to have depth perception?
- stereoscopic vision
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What is necessary for stereoscopic vision?
- binocular vision
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Why might a child who had an eye patch during visual development not develop stereoscopic vision?
- monocular deprivation in eye with patch
- fewer impulses from deprived eye to ocular columns in visual cortex
- if patch worn during critical period columns for this eye narrow due to loss of synapses
- child may have reduced or no vision in deprived eye
- sensory input from both eyes required for stereoscopic vision
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How do we perceive depth for far away objects?
Using visual cues and past experiences
- Both eyes views very similar images so visual cortex cannot calculate death
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What are some examples of visual cues that help us perceive depth?
- parallel lines. Converging
- relative sizes of objects
- overlap of objects
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How does the brain develop?
- neurons divide
- neurons migrate to their final position
- axons lengthen and myelinated
- synapses form
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How does the visual cortex develop?
- axons from retinal neurons grow to the thalamus
- axons from neurons in thalamus grow to visual cortex in the occipital lobe
- visual cortex consists of columns of cells
- adjacent columns receive impulses from same retinal area of left and right eyes
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What were the experiments of Hubel and Wiesel
Experiment 1:
- monkeys
- group 1: raised in dark for 3-6 months
- group 2: raised w/ light but not patterns for 6 months
Both groups had difficulties with object discrimination and pattern recognition
Conclusion: visual development requires stimulation with light and patterns.
Experiment 2:
- newborn monkeys deprived of light in one eye for 3-6 months (=monocular deprivation)
- newborn monkeys deprived of light stimulus in one eye for one week after birth
- repeat with adult monkey
- both groups were blind in one eye
- the young monkeys retinal cells responded to light but cells did not respond
Conclusion; critical windows for visual development
Experiment 3:
Cats
- Deprivation of light stimulus in one eye at various times after birth for various lengths
- deprivation at age <3 weeks: no effect
- deprivation at age >3 months: no effect
- deprivation at 4 weeks: major effect
Conclusion:
- critical period at 4 weeks
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What is a critical period
- time period where the nervous system must have specific stimuli to develop properly
- evidence of the role of nurture in visual development
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What is evidence for critical windows in humans case studies?
- people born with cataracts or eye damages at early ages have permanently impaired vision
- people with cataracts later in life do not have impaired vision
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What happens during visual development
- columns made before birth
- overlap between territories of different axons
- refinement of territories through stimulation produces distinct patterns of columns seen in adults
- monocular deprivation during critical period leads to columns from light-deprived eye being narrower
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What is learning?
- any (relatively permanent) change in behaviour or knowledge that comes from remembered experiences and information
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Where is memory located in the brain
- temporal lobe (hippocampus) - short term
- parietal lobe
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How is short term memory formed?
- increasing the strength of synapses by increasing the amount of neurotransmitter released
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How is long term memory formed?
- repeated stimulus triggers gene expression in active neurons
- gene expression leads to increase in number of synapses (-> long term memory)
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What is aplysia
- sea slug
- very large neurons
- behaviour can be analysed
- behaviour is modified by learning
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What is habituation?
- a decreased response to a repeated stimulus
- involves learning and memory
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Describe a aplysia which is not habituated
- gill in cavity on upper side of body
- water expelled through siphon
- if siphon touched: reflex withdraws gill and siphon for protection
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Describe an aplysia which is habituated
- aplysia learned not to withdraw gill after repeated stimulation
- essential as aplysia lives in sea withi continue wave action
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Frequent repeated stimulus…
Decreases amount of neurotransmitter released at synapses
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Describe synapses of habituated alypsia
- Frequent stimuli
- less Ca2+ enters
- less neurotransmitter released
- no depolarisation of post synaptic membrane
- no action potential
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What are Hubel and wiesels overall findings?
- synapses are strengthened or weakened depending on stimulation during the critical period
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What makes a good animal model?
- readily available
- easy to find
- short life span
- easy to study
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What are the ethics of animal research?
1. Rights and duties
2. Informed consent
3. Utilitarian approach
4. Animal welfare
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What is Parkinson’s?
- caused by the death of dopamine generating cells in the substantial nigra -> low dopamine less
- neurons die due to abnormal aggregation of protein in the cytoplasm
- affects neurons in basal ganglia involved in movement
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What are early symptoms of Parkinson’s?
- muscle stiffness
- muscle tremor
- slow movement
- poor balance
- problems walking
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What are the later symptoms of Parkinson
- cognitive speech, behavioural and mood problems
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What is dopamine?
- monoamine nrutoransmitter
- produced in substantial nigra
- involved in various functions, reward, pleasure, euphoria
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Describe the pathway of normally controlled muscle activity
1. Impulses pass from motor cortex to spinal cord and muscles
2. Impulses pass from motor cortex to basal ganglia to dampen signals from (A) to brain stem
- this is controlled by dopamine made in substantia nigra
3. Acetylcholine inhibits damping effect
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Describe how the pathway of muscle activity in Parkinson’s
1. Impulses pass from motor cortex to spinal cords and muscles
2. Cells in substantia nigra don’t produce dopamine
3. Basal ganglia not activated to dampen impulses from A
4. Increased muscle tension and tremor
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How do you slow down loss of dopamine to treat Parkinson’s?
- use monamine oxidise inhibitors (MAOI)
- block breakdown of dopamine by MAO-B
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How can you increase dopamine levels in the treatment for Parkinson’s?
- dopamine cannot cross the blood Brian barrier
- use dopamine precursor levodopa (L-DOPA) which can cross barrier
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How can you use dopamine agonists to treat Parkinson’s?
- mimics dopamine
- bind and activate dopamine receptors
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How could you inhibit acetylcholine to treat Parkinson’s?
- use anticholin gene medications
- basal ganglia function is now less inhibited
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How do you use brain surgery to treat Parkinson’s? -
Deep brain stimulation using electrodes
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How do you use stem cell therapy to treat Parkinson’s
- replacement of dopamine producing cells in substantia nigra
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What is clinical depression?
- mental disorder
- characterised by episodes of low mood accompanied by low self esteem and loss of interest in enjoyable activities
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What are the causes of clinical depression?
Multifactorial
- genetic component (5-HTT gene = serotonin transporter)
- environmental factors (traumatic events)
- linked to low serotonin activity in the brain
- involvement of other neurotransmitters such as dopamine and noradrenaline
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What is serotonin?
5-hydroxytryptamine (5-HTT)
- monamine neurotransmitter
- produced in the brain stem
- affects neurons in the cortex, cerebellum and spinal cord
- regulation of mood, appetite and sleep
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What is the 5-HTT gene?
- codes for serotonin transporter protein in the presynaptic neuron membrane
- influences susceptibility to depression after stressful event
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Describe the ‘short’ 5-HTT allele phenotype
- less mRNA
- less 5-HTT protein
- less serotonin taken up
- higher risk of depression
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Describe the long 5-HTT allele phenotype
1. More mRNA
2. More 5-HTT protein
3. More serotonin taken up (better management of serotonin - quickly repackaged into vesicles)
4. Lower risk of depression
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Why may there be a higher risk of depression in short allele phenotype?
- SS have had elevated levels of serotonin since fetus
- brain adapts to elevated serotonin by reducing the number of synaptic receptors
- higher risk of depression if cant respond to serotonin
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How is depression treated?
- counselling
- medications (to restore serotonin levels)
- selective serotonin re-uptake inhibitors (SSRI) - blocks serotonin reuptake
- tricyclin antidepressants
- monoamine oxidase inhibitors
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How can drugs can interfere with synapses?
1. NT synthesis and storage
2. Ion channels
3. NT release
4. NT receptor binding
5. NT re-uptake
6. NT breakdown
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What are the effects of MDMA on synapses?
- blocks uptake of serotonin
- allows more serotonin release
- high serotonin level in synapses
- increased frequency of binding to post synaptic receptors
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Short-term effects of MDMA
- affects thinking, mood, memory
- emotional warmth + empathy
- euphoria, pleasure and enhanced senses
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Long term effects of mdma
- depression (serotonin depletion, decreased numbers of serotonin transporter proteins and receptors)
- reduction of number of serotonergic axon terminals
- reduction in grey matter volume (affections attention, learning, memory, processing and sleep)
- p psychological problems
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What is genome sequencing?
- identify the dna base sequence of an individual, this allows us to determine the AA sequence of the polypeptides coded for by that dna
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What are the uses of genome sequencing?
- comparing genomes between species to determine evolutionary relationship
- genetic matching
- personalised medicine
- synthetic biology
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How has genome sequencing been used in personalised medicine?
- certain alleles change susceptibility to a response to a drug, treatments can be selected and implement earlier
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What social moral and ethical issues does genome sequencing raise?
- data protection
- genetic discrimination
- equal access
- editing of humans
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How can drugs be produced using GMOs?
- use recombinant dna technology to produce transgenic organisms that produce a required protein
- genetic code is universal
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How are enzymes used to isolate a desired gene?
- restriction endonucleases cut DNA at specific sequences
- different REs cut at different points but one re will always cut at same sequence
- particular res allow you to cut out a certain gene of interest
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Summarise the process of inserting a dna fragment into a vector
- plasmid is used as the vector and is cut using same restriction enzymes as DNA so ends are complementary
- DNA ligase joins the fragment and plasmid together
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Summarise the process of inserting a vector into a host cell
Cell transformation
- host cells from plants animals or microorganisms such as bacteria are mixed with the vectors in an ice-cold solutions, then heat shocked to encourage cells to take up vectors.
- cells can be grown
- dna fragment will be cloned
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How do you identify transformed cells
- insert marker genes into vectors
- disrupt the resistance gene with the fragment from the desired gene. Cells that do not survive have taken up the vector. Use replica plating to culture the strain
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Suggest risks of using GMOs
- may reduce biodiversity so communities may become more vulnerable to disease
- horizontal gene transmission into wild populations
- adverse effects on other species
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Suggests the benefits associated using genetically modified organisms
- increased yield, drought, pest resistance
- can produce large quantities of protein for harvesting
