Nervous systems Flashcards
(288 cards)
1
Q
Significance of the neural tube?
A
Where the entire CNS develops from.
2
Q
Structure of neural tube?
A
Walls contain neuroblasts, lumen (hollow).
3
Q
What are the three primary brain vesicles?
A
Prosencephalon (forebrain), mesencephalon (midbrain), rhombencephalon (hindbrain).
4
Q
What are the five secondary brain vesicles?
A
Telencephalon, diencephalon, mesencephalon, metencephalon, myelencephalon.
5
Q
When are the three primary vesicles?
A
Three to four week embryo.
6
Q
When are the five secondary vesicles?
A
Five week embryo.
7
Q
Characteristics of lower vertebrate brains?
A
Large areas devoted to olfaction, important optic lobes in fish and amphibians, increase in cerebrum size, 3 layered cerebral cortex.
8
Q
Key features of mammalian brains?
A
Folding of cortex, six layered neocortex, enlargement of cerebellum, reduction of olfactory system.
9
Q
Characteristics of human brain?
A
Development of frontal cortex, enlargement of cortical areas.
10
Q
What are human cortical areas involved in?
A
Manual dexterity, speech, facial expression.
11
Q
What is vertebrate CNS tissue organised into?
A
White and grey matter.
12
Q
White matter?
A
Myelinated axons.
13
Q
Grey matter?
A
Collections of cell bodies.
14
Q
Structure of white matter?
A
Bundles of myelinated axons form tracts connecting nuclei.
15
Q
Structure of grey matter?
A
Formed from nuclei.
16
Q
What is a nucleus (structurally)?
A
A cluster of cell bodies and their dendrites where synapses are made and information is processed.
17
Q
What areas of the cortex can remain in mammals?
A
Some primitive three layered areas.
18
Q
How are individual laminae (layers) characterised?
A
By the types of neurons they contain and by their connections (afferent, efferent, intracortical).
19
Q
Give three examples of evolution of function of vertebrate CNS featuring.
A
Swimming in fish, walking on land by amphibians and reptiles, birdsong.
20
Q
How do lamprey swim using undulatory movements of the body forwards and backwards?
A
Use central pattern generators (CPGs) on both sides of spinal cord.
21
Q
What are CPGs?
A
Network of neurons which produce rhythmic behaviours.
22
Q
Where are CPGs in lamprey?
A
On each side of spinal cord segment.
23
Q
Where on lamprey can the basic rhythmic drive for locomotion be generated?
A
Each half of the spinal cord.
24
Q
What ensures co-ordination in lampreys?
A
Connections between left and right sides.
25
What controls the CPGs?
Locomotor command centres in brainstem.
26
What controls the brainstem locomotor command centres?
Basal ganglia (nuclei) in cerebral hemisphere.
27
What fish has the fastest acceleration from standing start?
Barracuda.
28
What do all bony fish have?
Fast escape/ startle response mediated by Mauthner neurons (M-neurons).
29
M-neurones?
In most fish, on either side of brainstem, large neurones (cell soma 100um diameter).
30
Characteristics of M-neurone?
Detect vibration by sensory input, unilateral muscle contraction, collaterals contact interneurons and motor neurons at all spinal levels.
31
Location of m-neuron axons?
Crosses midline and extends throughout spinal cord.
32
How do amphibians and reptiles walk on land?
Friction of moving in water replaced by pull of gravity, raises body off ground before taking steps.
33
Anatomical concepts?
Antagonistic muscle groups, hip shoulder joints, multi-joint movements, major involvement of spinal cord.
34
Vestibulocerebellum?
Balance.
35
Spinocerebellum?
Body raised off ground.
36
Neocerebellum?
Connected to cerebral cortex for motor coordination.
37
Step cycle in cats?
Flexors and extensors inhibit each other, alternating steps, four steps - flexion, first extension, second extension, third.
38
Three steps of walking (neurophysiology)?
Spinal reflexes (work without brain control), stimulation/ inhibition of antagonistic muscle groups, collaterals contact interneurons-ordination of movement of joints, sensory feedback controls rate of stepping, supra-spinal control.
39
What is the supra-spinal control?
Ascending sensory pathways run from spinal cord to sensory cortex in cerebral hemisphere, neighbouring motor cortex, descending motor pathways exert control of motor neurons in spinal cord.
40
What enables song in birds?
Complex interconnection of nuclei and tracts in bird brain controlling syrinx.
41
What are photoreceptors?
Cells that absorb light, contain opsins which absorb photons in their external membrane.
42
What are the vertebrate photoreceptors?
Rods and cone cells.
43
Invertebrate photoreceptors?
Retinula cells.
44
How does light polarise in vertebrate and invertebrate?
Hyperpolarises vs depolarises.
45
How to the cells increase the efficiency of light trapping?
Expand into discs or finger like rods.
46
What is the Ciliary line?
The photoreceptive part of the cell derived from a modified cilium.
47
What is the Rhabdomere line?
The photoreceptive membranes derived from the cell body.
48
How many classes of photoreceptors?
Two.
49
How much of the focusing power is on the cornea?
70%
50
How much focus is at the lens?
30%
51
What type of focusing is the cornea and lens?
Fixed and variable respectively.
52
Significance of optic disc?
Blind spot.
53
Where are the photoreceptors located?
Retina.
54
What helps the opsins?
Discs.
55
Why do the discs help the opsins?
Membrane bound so discs greatly increase number in each photoreceptor therefore improving efficiency.
56
Are rods or cones more or less sensitive?
Rods more sensitive, cones less.
57
What do the cones detect?
Colour
58
Vertebrate phototransduction steps?
Similar but some differences between vertebrates and invertebrates, sodium and calcium channels open in dark due to high cGMP, depolarised photoreceptor increases transmitter release, breakdown cGMP to GMP, channels close, hypolarise cell, transmitter release reduced.
59
What does light activate in phototransduction?
Breakdown of cGMP into GMP.
60
What photoreceptors activate at low light levels?
Only rods active, no colour perception.
61
What light can help dark adapt?
Red light.
62
What level of light makes cones sensitive to red green and blue light?
Bright light levels - gives us colour perception.
63
Components of human visual pathway?
Optic nerve, optic tract, synapse, primary visual cortex.
64
What does the cross over in the brain mean?
Right eye to left brain, left eye to right.
65
What animals have small rudimentary forebrains?
Reptiles, amphibians and fish.
66
Where does visual processing take and not take place in small forebrain animals?
Not in forebrain, happens in visual part of midbrain.
67
What is the visual part of the midbrain?
The optic tectum.
68
What are mammals visual areas of midbrain involved in?
Visual reflexes.
69
What is the fovea?
Contains highest conc photoreceptors, sharpest part of image.
70
What do some birds have two of?
Foveae (medial - side and lateral - forward).
71
What does the foveal base act to create?
A telephoto system.
72
How much more is the bird visual actuary in medial fovea to men’s?
2-3x.
73
How to birds have to adapt to suit their visual paths?
Fly along a curved flight path.
74
Invertebrate phototransduction steps?
Light activates phopholipase C to break down PIP2 to IP3 and DAG, open ion channels, photoreceptors depolarise.
75
What are insect and Crustacea eyes like?
Compound eyes, made of photoreceptor units, each own lens, all round vision.
76
What do receptor units in different parts of insect eyes have?
Different properties, ie sensitivity to colour or light polarisation.
77
What are the central rhabdomeres sensitive to in some insects?
UV light - helps guide to patterns visible on plants only with UV light to guide to nectar and pollen sources.
78
How can flies use polarised light?
For navigation and colour vision to find flowers.
79
What is the fly visual system tuned to recognise?
Movement, looming objects, visual field slippage.
80
What animals have simple eyes (ocelli)?
Spiders and insects.
81
Characteristics of simple eyes?
Smaller, many receptor under one lens.
82
Simple eyed insects have how many eyes?
Three simple eyes arranged in triangular pattern, act as horizon detector so insect maintains stable flight path.
83
Why are octopus and squid different to other molluscs?
Have complex brains and intricate behaviour, change skin colour and texture, sophisticated eyes.
84
Why can snakes use infra-red vision?
Body temp much lower so receptor kept cool.
85
How do we know snakes see infrared by detecting heat not light?
Part of somatosensory system, no signals from eyes - the pit organ.
86
What is the main sensory nerve to snake faces?
Trigeminal nerve.
87
Snakes forebrains and midbrain characteristics?
Primitive forebrain, visual processing in midbrain optic tectum.
88
What receptor works to detect infrared?
TRPA1 - activated at 28 degrees, not in rat snakes.
89
What kind of light is detected in ommatidium?
Polarised parallel to microvilli.
90
Why are all directions of light detected?
Outer rhabdomeres have microvilli which direction changes with depth from surface.
91
What are microvilli like in central rhabdomeres?
One direction, sensitive to light polarisation.
92
What is innervation in terms of neuroanatomy?
Nerve supply of…
93
Motor neurones?
Causes movement or secretion.
94
Afferent vs efferent?
Towards or away from.
94
Sensory neurones?
Receives and responds to a stimulus.
95
Ipsilateral vs contralateral?
The same side vs the other side.
96
CNS?
Central nervous system - brain and spinal cord.
97
PNS?
Peripheral nervous system - cranial nerves and spinal nerves.
98
Sensory neurones?
Brings sensory info to CNS from receptors in peripheral tissues and organs.
99
Motor neurons?
Sends motor commands from CNS to target organs.
100
What are the subsections of the peripheral nervous system?
Somatic (skin and skeletal muscle) and autonomic (viscera - smooth and cardiac muscle).
101
What are the subsections of the autonomic nervous system?
Sympathetic (fight or flight) and parasympathetic (rest and digest).
102
What is a segment?
A unit of anatomical structure that can be repeated along the length of an animal.
103
How is the mammalian spinal cord organised?
Segmental organisation.
104
What does the Dorsal horn control?
Sensory neurones.
105
What does the Ventral horn control?
Motor neurones.
106
Where does the ascending sensory pathways take place?
Dorsal column (medial lemniscus) at back of spinal cord.
107
Where is sensory information processed?
By primary sensory neurones with cell bodies in dorsal root ganglia.
108
What kind of communication initially happens in the ascending sensory pathways?
Ipsilateral.
109
What happens to turn the communication contralateral for ascending sensory pathways?
Neurons decussate (cross over) at the medulla oblongata.
110
What does Spinothalamic mean?
Information from spine up to the thalamus.
111
Where do the sensory neurons decussate?
At point of entry (L5).
112
What creates a contralateral pathway?
Neuron synapses with another neuron.
113
What does LMNs stand for?
Lower, motor, neurone.
114
What connects functionally related LMNs?
Interneurones.
115
Are descending pathways (tracts) afferent or efferent to LMNs?
Afferent.
116
Are spinal nerves somatic or autonomic?
Both!
117
Where does the descending motor pathway take place?
Corticospinal (pyramidal) tract.
118
Where does the Corticospinal tract pass through?
Pyramidal structures of the medulla and decussates.
119
What does the descending motor pathway control?
Lower motor neurones that innervate skeletal muscles.
120
What kind of movements does the descending motor pathway control?
Non-stereotyped (purposeful).
121
Consequences of interruption of descending pathways?
Potentially serious, depends on level of injury and where/if tract decussates.
122
What is Somatotopy?
The orderly arrangement of the nervous system in relation to the parts of the body.
123
What is used to represent the anatomical organisation of brains?
Topographic maps.
124
What is the significance of specific brain regions?
They have specialised functions.
125
What does a greater number of neurons mean generally?
More integration can occur.
126
What word is used to describe neural circuits?
Plastic.
127
What is neurogenesis and where in the brain does it happen?
Creation of new neurons, confined to specific areas.
128
What are the different planes of section used in Neuroanatomy?
Coronal, Transverse (horizontal), sagittal.
129
What is the Coronal plane in Neuroanatomy?
Parallel to the face.
130
What is the Transverse plane in Neuroanatomy?
Parallel to the soles of the feet.
131
What is the Sagittal plane in Neuroanatomy?
In the midline, at right angles to coronal plane.
132
What is the association cortex?
Cerebral cortex outside the primary areas - involved in communication, memory, planning future behaviour, and thought.
133
What are Gyrus/ Gyri?
Folds on surface.
134
What are Sulcus/ Sulci?
Dips between gyri.
135
Two examples of inter-hemispheric commissures?
Corpus callosum, anterior commissure.
136
What does motor control, control?
Planning, execution, co-ordination.
137
What is the extrapyramidal system?
Used for stereotyped (repetitive) movements.
138
What is an example of a part of the brain that is part of the extrapyramidal system?
Cerebellum.
139
What is the function of the cerebellum?
Functions in initiating, timing and terminating movements - coordinates motor output.
140
Areas of grey matter deep within hemisphere?
Basal ganglia (nuclei), thalamus, hypothalamus.
141
What is the basal ganglia?
A collection of nuclei which produce regulated movements.
142
Extrapyramidal motor control - major inputs received from?
Cerebral cortex, thalamus, brainstem.
143
Extrapyramidal motor control - major outputs to?
Thalamic nuclei, cortex, brain stem.
144
What does the basal ganglia have implications for?
Parkinson’s disease (PD) and Huntington’s disease (HD).
145
Summarise the function and significance of the thalamus.
Relays sensory pathways to cerebral cortex (ascending tracts), activates cerebral cortex (sleep and consciousness), emotional effects generate autonomic activity, coordination of visual and motor activity.
146
Summarise function and significance of the hypothalamus.
Responds to physiological environmental and emotional change that affect autonomic system, part of limbic system, maintenance of homeostasis, neuroendocrine control.
147
Specifically, what does the hypothalamus do within the limbic system?
Involvement in thirst, hunger, appetite, reproductive, associated behaviour.
148
What is the significance of the brainstem?
Connects brain to spinal cord.
149
Sections of brainstem?
Midbrain, pons, medulla oblongata.
150
What is the brainstem involved in?
Functional composition of cranial nerves III - XII, conveys sensory info to cortex, motor control from cortex to motor neurons, cerebellar connections, regulation of autonomic, visual and auditory reflexes, alertness, consciousness, life and death.
151
What controls breathing?
Controlled by the medulla oblongata.
152
What is Spina Bifida?
A congenital defect of spine in which part of spinal cord and meninges are exposed through gap in backbone.
153
What is Hydrocephalus?
Accumulation of cerebrospinal fluid in brain.
154
What are the three sections of the ear?
External ear, middle ear, inner ear.
155
Name elements of the internal ear.
Pinna, external ear canal, ear drum, nerves, ear ossicles, oval window.
156
What is the scientific name for the ear drum?
Tympanic membrane.
157
How is sound initially detected?
Because it sets up vibrations in the eardrum and amplified by movement of the ear ossicles in the middle ear.
158
What are the components of the Cochlea?
Scala vestibuli, scala tymrani, basilar membrane, scala media.
159
Do lower or higher frequencies run further in the travelling wave?
Lower frequencies.
160
What is the Organ of Corti?
Hearing organ.
161
What are the components of the Organ of Corti?
Hair cells, tectorial membrane, nerve cells (spiral ganglion), basilar membrane.
162
Explain the concept of the Tonotopy.
Tonotropy relationship as how far wave travels depends on frequency.
163
What is the significance of Tonotopy?
Maintained all the way to the auditory part of the brain, the one way the nervous system can make sense of auditory input.
164
Areas of the auditory pathways?
Auditory cortex, thalamus, mid, medulla, auditory nerve
165
What plays the same role as the eardrum in vertebrates for insects?
The tympanum (thin cuticle) - vibrates more than normal cuticle.
166
Where is an insects ear located?
In its leg.
167
Components of an insect’s leg cross-section?
Blood vessel, crista acoustica, auditory neurone, acoustic membrane, trachea, tympanum, muscle.
168
Are bat or cricket mating calls higher frequencies?
Bat calls.
169
What is the cerebral cortex involved in?
Planning of voluntary movement.
170
What is the cerebellum involved in?
Co-ordinates motor output and force of muscle contraction.
171
What is the brainstem involved in?
Conveys sensory info to the cortex and motor info to lower motor neurons.
172
What is the thalamus involved in?
Relays sensory info to the cortex.
173
What is the basal ganglia involved in?
Enhances desired movement and inhibits unwanted movement and regulation.
174
What are the ascending (sensory) neuronal pathways?
From periphery up towards brain.
175
What are the descending (motor) neuronal pathways?
From brain down to periphery.
176
What is the corticospinal pathway used for?
Voluntary movement of masculature.
177
What is the dorsal column pathway used for?
Vibration, proprioception, fine touch.
178
What are the extrapyramidal pathways?
Carry motor fibres to spinal cord.
179
What is the spinothalamic pathway?
Pain, temperature, touch, pressure.
180
What are key components of the somatic reflex arc?
Sense organ, afferent neuron, synapse, efferent neuron, neuromuscular junction, muscle.
181
What is the release of acetylcholine on to skeletal muscle?
Excitatory.
182
Where does inhibitor of skeletal muscle occur and what is the name for it?
Prior to level of spinal cord, reciprocal inhibition.
183
What is another name for knee jerk reflex?
Stretch reflex/ mono-synaptic reflex.
184
What is the sequence of events in a knee jerk reflex?
Stimulate patellar tendon, activates stretch receptors or muscle spindles within extensor muscle, activates sensory nerve, extensor muscle contracts, flexor muscle relaxes.
185
Where deos reciprocal inhibition occur?
In spinal cord, no involvement of brain.
186
What are muscle spindles?
Stretch receptors.
187
What is involved in the flexor/ crossed extensor reflex?
Both sides of body, removing foot from stimulus (flexor contracts), other side of body stabilises (extensor contracts).
188
What are responses not dependent on?
Conscious perception.
189
What are components of a reflex arc?
Receptor, afferent pathway, integrating center, efferent pathway, effector organs.
190
What do bats use for navigation and catching prey?
Echolocating calls.
191
What are the typical frequencies for bat calls?
25-100kHz.
192
What do moths use auditory systems for?
To detect predators and take evasive action.
193
What do male mosquitos do differently do females?
Use hearing to find and detect females by the humming of their wingbeats.
194
What part of the mosquitos detect the airborne vibrations?
Entire antenna.
195
Is an antenna an actual hearing organ?
No not generally, only used for this purpose tho and very tightly tuned.
196
What detects the vibrations at the base of the antenna?
Johnston’s organ - active processes in sensory neurons amplify the signal.
197
What is olfaction?
Smell.
198
What is gestation?
Taste.
199
What is the taste environment like in environment?
Aggressive, cells replaced in a few weeks, high turnover.
200
What are the different areas of the tongue?
Foliate papillae, circumvallate papillae, fungiform papillae, taste buds, taste sensory neurones, synapses, microvilli, basal cells, taste cells, taste pore.
201
What are the five types of taste sensation?
Sweet, salt, bitter, sour (acid), umami (glutamate).
202
Describe taste cells for salt and acid.
Have channels for Na+ and H+ ions, they depolarise cell, opening Ca2+ channels, causing transmitter release.
203
Describe taste cells for bitter, sweet and umami.
Have a G-protein coupled receptors that bind to molecules causing ion channels to open, thus triggering transmitter release.
204
What does binding of odour molecules in the olfactory transduction do?
Causes a G protein subunit to stimulate adenylyl cyclase.
205
Where does olfactory transduction happen?
On the olfactory neurone ciliary membrane.
206
What does stimulation of adenylyl cyclase cause?
Increases levels of cAMP which opens channels in cell membrane causing it to depolarise which causes an action potential to be generated.
207
How many odour receptor genes do mammals have and what do they do?
1000, allow discrimination of around 10,000 odours.
208
What is sensory transduction?
Simple system in which ion channels opened by binding an odour molecule.
209
What covers entire invertebrate body for taste and olfactory?
Chemosensory hairs.
210
What are pheromones?
Molecules released by one sex to attract the other.
211
What are exteroceptors?
Sensory endings that monitor interactions with the external environment.
212
What are components of exteroceptors?
Merkel disk, epidermis, dermis, meissner corpuscle, pacinian corpuscle, Ruffini ending, hair follicle ending, naked ending.
213
What sensation does the naked ending sense?
Pain, temperature.
214
What sensation do hair follicle endings sense?
Hair movement.
215
What sensation do Merkel’s endings sense?
Sustained pressure, detailed mapping of texture and shape.
216
What type of sensations do Meissner’s ending sense?
Touch, brief response, effective for transient contact.
217
What sensation does the pacinian corpuscle sense?
Vibration.
218
What sensation do Ruffini endings sense?
Shear stress.
219
What does a receptive field mean?
Each sensory neuron responds to stimulus within specific region of skin.
220
What does a higher receptors density mean?
Smaller receptive field, greater acuity.
221
What do you do to calculate receptive field size?
Adjust distance between tips, determine min distance at which 2 points felt.
222
What are the ascending tracts?
Spinothalamic, spinocervical, spino reticular, dorsal column.
223
What are the primary sensory and motor areas?
Primary motor cortex, central sulcus, primary sensory cortex, primary visual cortex, primary auditory cortex.
224
What does the primary motor cortex do?
Muscle control.
225
What does the primary sensory cortex control?
Sensation from skin and muscle.
226
What does sensory homunculus explain control?
The left side of the brain receives info and controls right side of body.
227
What are proprioceptors?
Receptors monitoring muscles and joints.
228
Give examples of proprioceptors?
Muscle spindles, Golgi tendon organs, joint receptors.
229
How do muscle spindles work?
When muscle is stretched, sensory axon in spindle responds, signal reaches spinal cord, alpha motor neurons contract muscle, spindle is slack so cannot respond further, gamma motor neurons fire, spindle contracts.
230
What do Golgi tendon organs do?
These monitor stretch in tendons.
231
How has our awareness of relative positions of parts of body come about?
From activity of muscle spindles plus Golgi tendon organs.
232
What do joint receptors do?
These endings in capsule and supporting ligaments of joints give sensations of pain and discomfort when joint is moved beyond its range of normal movement.
233
What are exteroceptors in invertebrates?
Touch/ wind sensitive hairs.
234
How is external sensation/ exteroception mediated in animals with exoskeletons?
Mechanosensory hairs, detect touch and air currents and are important in maintaining flight movements.
235
Where do axon terminals of invertebrate mechanoreceptors end?
In the brain or segmental ganglia.
236
What is similar for invertebrates to vertebrate nervous system?
Somatotopy helps keep order in sensory systems of invertebrates also, making the organisation of synaptic connections more efficient.
237
What are external proprioceptors in insects and crustaceans?
Insect hair plates and campaniform sensilla.
238
What fulfils the same role as vertebrate joint receptors for invertebrates?
Femur rotates upwards, surface contacts hair plates on coxa indicating that it can travel no further.
239
What are campaniform sensillae?
Depressions with a floor of very thin cuticle which monitor distortion of the insect exoskeleton - monitor strains in the shafts of halteres.
240
What do oscillating halteres do?
Act like gyroscopes as tend to resist changes in direction of movement, when insect turns during flight creates strains in shaft of each haltere that are detected by arrays of campaniform sensillae that lie at base.
241
What is the Chordotonal organ?
Lies inside exoskeleton and is stretch receptor which has its own tendon, when joint flexed sensory neurons detect position and speed of movement.
242
What is the muscle receptor organ?
Muscle don’t provide power for movement, small accessory muscles supplied by same nerve cells that control power muscles.
243
What movements does the MRO monitor?
Powerful tail flips used for escape.
244
What are electric field detection?
On sharks and rays, sensory structures detect electric field associated with muscle activity in prey species, also detect temp.
245
How do electric field detections work?
Sensory nerve endings at base of pit filled with conductive gel, prey detected when not visible.
246
What are the two basic types of electric fish?
Those that use high voltages to stun prey and weakly electric fish that use constant fields to trains of pulses for navigation and communication.
247
What are electric fields generated by?
Modified muscle cells.
248
What do birds use magnetic fields for?
Direction during migration.
249
What is the ANS?
Autonomic nervous system.
250
What is the ANS involved in?
Sleeping, eating, thermoregulation, CV control, crying, elimination of waste products, breathing and respiration, light reflex, stress response.
251
What does autonomic =?
Autonomous.
252
What are functions of the ANS?
Functions without you being aware of it or exerting voluntary control, responds principally to physiological demands, responds to environmental and emotional demands.
253
What does the ANS do overall?
It innervates and therefore controls the organs of the body.
254
What does viscus mean?
Organ.
255
What does viscera mean?
Organs.
256
What is another name for the ANS?
Visceral nervous system.
257
What is the basis of autonomic control?
ANS reflex arc.
258
What are the subdivisions of the ANS?
Sympathetic nervous system and parasympathetic nervous system.
259
What does the sympathetic nervous system control?
Fight or flight.
260
What does the parasympathetic nervous system control?
Rest and digest.
261
Explain what is meant by the term antagonsitically when referring to SNS and PNS?
Usually have opposing effects on organ therefore systems often function antagonsitically.
262
What may effects of ANS on effectors be?
Either excitatory or inhibitory.
263
What does the efferent ANS consist of?
Two neurones - pre ganglionic and post ganglionic.
264
Where are the pre and post ganglionic neurones situated?
Pre is before the ganglion between CNS and that, post is after ganglion between that and target organ.
265
Explain the difference between the two neurons in PNS and SNS?
Longer pre ganglion neurone in PNS, loner post neurone in SNS.
266
What do all preganglionic neurones do?
Release ACh at the ganglionic synapse.
267
What do some post ganglionic neurones release?
A peptide.
268
What are the transmitters of pre neuron and receptors of post in SNS and PNS?
Acetylcholine and Nicotinic AChR.
269
What is the transmitter of post neurones and receptors on target in SNS?
Noradrenaline transmitter and alpha or beta adrenergic receptors.
270
What is the transmitter of post neurones and receptors on target in PNS?
Acetylcholine transmitter and muscarinic AChR.
271
What are all preganglionic autonomic neurons under the direct control of?
Pathways descending from higher regions of the brain in particular the hypothalamus.
272
Why are post ganglionic axons not attached to the cells of the target organ?
They may need to move in relation to them.
273
What are the two locations (outflows) of pre neuron cell bodies?
Cranial - four cranial nerve nuclei, sacral spinal cord - S2, 3, 4.
274
What do the cranial preganglionic neuron cell bodies do?
Control secretory glands in head, two intra-ocular muscles of eye.
275
What do preganglionic neuron cell bodies in sacral spinal cord do?
Emptying nerves, control large bowel/anus, bladder, erectile tissue of genitalia.
276
Where is the vagus nerve located?
Leaves the head and enters the thoracic and abdominal cavities.
277
What is the distribution of cranio-sacral parasympathetic outflow like?
Relatively restricted.
278
Where is the lateral horn of the spinal cord?
Segments T1 - L2, preganglionic axons synapse.
279
What are the two options of sympathetic outflow from CNS?
Para vertebral ganglia or pre vertebral ganglia.
280
What is sympathetic outflow from CNS like?
Relatively unrestricted throughout body.
281
How many possible routes for sympathetic preganglionic axons?
Three.
282
What two ways can post ganglionic axons reach their target organs?
Either by joining peripheral nerves or by running along arteries that supply target organs.
283
What are two examples of ANS?
Light reflex and thermoregulation control.
284
Give and overview of light reflex.
Pupil constricts, afferent neuron is projection of optic nerve to oculomotor nucleus, short post ganglionic fibres travel to circulatory muscles of iris to contract and narrow pupil.
285
What is the constricting of the pupil in light reflex known as?
Direct pupillary response.
286
How does the sympathetic reflex of thermoregulation work?
Increased activity in thermoreceptors, reflex increased sympathetic discharge to sweat glands, decreases discharge to cutaneous blood vessels (vasodilation).
287
What is the enteric nervous system?
The innervation of GI tract - intrinsically controlled - in intestinal wall.
