Nervous system Flashcards
1
Q
What does the nervous system produce
A
effective responses to a stimulus from the environment
2
Q
Examples of an external stimulus
A
light, temperature, chemical, touch, vibration
3
Q
Examples of an internal stimulus
A
chemical – pH, ions, molecules. Blood pressure, temperature
4
Q
Location of interneurons
A
Located between neurons and form a connection between other neurons
5
Q
where are interneurons found
A
in both vertebrates and invertebrates
6
Q
Interneuron distance
A
local or send their axons for long distances within a nervous system (projection interneurons)
7
Q
Consequence of the presence of interneurons
A
Increase the number of synapses – and therefore the complexity of neuronal circuits
AKA relay neurons, association neurons or connector neurons
8
Q
How can a neuron vary
A
- Cell body (soma) - size and shape
- Dendrites – number, branching, length
- Axon – length, diameter, branching, myelinated or unmyelinated
- Synaptic terminals – number and structure
- Synaptic transmission – chemical or electric
9
Q
What does the structure of the neuron relate to
A
directly relates to its function
10
Q
What is hydra
A
a freshwater invertebrate
11
Q
describe the nervous system of a hydra
A
a simple nerve net with no CNS
12
Q
What movements does the hydras nervous system allow
A
movement of body and tentacles in water
13
Q
direction of action potentials in hydra
A
conducted in all directions - bidirectional
14
Q
sea anemone and corals (invertebrates) movements
A
- Slow but coordinated movements of polyps
- Tentacles (catching prey)
- Body movements (defence)
15
Q
Sensitivity of sea anemone and corals
A
Tentacles/oral disc 4000 x more sensitive than the ‘column’
16
Q
Complexity of jellyfish nervous system
A
more complex nerve nets
17
Q
Movements of jellyfish
A
Spontaneous rhythmic activity (slow state and startle). Contractions of the margin of the ‘bell’ produce a propulsive force forward
18
Q
Star fish’s nervous system
A
a modified nerve net
19
Q
What coordinates limb movements in a star fish
A
coordinated by neural ring
20
Q
What controls individual limb movements in a star fish
A
radial nerves
21
Q
What does the cooperation of radial nerves and neural ring in star fish allow
A
complex movements like movement and feeding
22
Q
what is bilateral symmetry
A
mirror image on both sides
23
Q
What did the evolution of bilaterality lead to
A
cephalization - CNS so animal moves forward and has sense organs at the front
24
Q
What are the consequences of cephalisation
A
- Increase in number of nerve cells
- Concentration of nerve cells into ganglia; ganglia into brains, nerves into nerve cords
- Development of functional speciality: AFFERENT neurons – towards the CNS, EFFERENT NEURONS – away from the CNS
- Localization of specific functions in different parts of the nervous system
- Development of interneurones and more complex synaptic contacts
- Development of head bearing sense organs
- Development of ventral nerve cord
25
What is a segment
a unit of anatomical structure that can be repeated along the length of an animal
26
What are the consequences of segmentation
1. Development of segmental ganglia with sufficiently complex neural circuitry to control locomotion in individual segments
2. Coordination of movement (and/or limb movement) between adjacent segments. e.g., in annelid worms or earth worms
27
What are connectives
ganglia joined by connecting nerves
28
What do arthropods
connectives, autonomic nervous system (ANS) which innervates the viscera of the body and segmental ganglia
29
What does the segmental ganglia do
Co-ordination of movement in walking/running and flying
30
How does the segmental ganglia coordinate movements
1. Receiving sensory information from a defined part of a body segment whose activity it regulates directly
2. Activating dorsal/ventral or left/right limb muscles appropriately in response to stimuli
3. Using central pattern generators (CPGs) - repeated rhythmic motor output independent of sensory stimulation
4. Interconnections between segmental ganglia (connectives) cam propagate activity along the length of the ventral nerve cord – and along the length of the animal – coordinated by the ‘brains’
31
mollusks (invertebrate) nervous system brain ganglia organisation
Buccal – feeding
Cerebral – coordination
Pleural – respiration
Pedal – movement
32
How do octopi exhibit foresight, planning, use of tools
Gets food, clears the front of its den and arranges rocks in order to cover the entrance before going to sleep
33
How do octopi exhibit persistence and thinking
Opens childproof caps on pill bottles
34
How do octopi play
Blowing jets of water from the funnel to send a pill bottle to the other end of the tank where the water flow sends it back - repeatedly
35
How do octopi show memory and affection
Recognise their human ‘caretakers’ by moving towards them and squirting water at them
36
How do octopi show thinking
Solving difficult problems using objects of differing colours and shapes
37
What did the CNS develop from
the neural tube
38
What do walls of the neural tube contain
neuroblasts
39
Structure of the neural tube
hollow tube, has a lumen
40
What are the 3 primary brain vesicles
1. prosencephalon (forebrain),
2. mesencephalon (midbrain)
3. rhombencephalon (hindbrain)
41
What secondary brain vesicles does the forebrain form
telencephalon and diencephalon,
42
What secondary brain vesicles does the midbrain form
mesencephalon
43
What secondary brain vesicles does the hindbrain form
metencephalon and myelencephalon
44
"lower" vertebrate brain features
1. Large area devoted to olfaction (smell)
2. Importance of the optic lobes in fish and amphibians
3. Increasing size of cerebrum. Cerebral cortex = 3 layers
45
What are the key features of the mammalian brain
1. Folding of the cortex (gyri and sulci – cerebral cortex only found in higher vertebrates)
2. Development of 6 layered neocortex
3. Enlargement of the cerebellum
4. Reduction of the olfactory system (especially in primates)
46
How has the human brain developed
the frontal cortex has developed and there is enlargement of cortical areas involved with unique human features: manual dexterity, speech, facial expressions
47
How is vertebrate CNS tissue organised
into white and grey matter
48
What is white matter
myelinated axons
49
What is grey matter
collections of cell bodies
50
What does the corticospinal tract consist of
neuronal pathway - descending and ascending tracts
51
What matter are tracts
white matter
52
What matter are nuclei
grey matter
53
What is a nucleus
a cluster of cell bodies and their dendrites where synapses are made and information is processed
54
What do bundles of myelinated axons form
tracts connecting nuclei
55
How are the layers of the cortex characterized
by the types of neurons they contain and by their connections (afferent, efferent and intracortical)
56
How do lampreys swim
by undulatory movements of the body forwards and backwards using central pattern generators (CPGs) on both sides of the spinal cord
57
What are CPGs
network of neurons which produce rhythmic behaviors
58
Where are CPGs in lampreys
on each side of each spinal cord segment in lamprey
59
How is the basic rhythmic drive for locomotion in lampreys generates
each half of spinal cord generates movement and connactions between left and right ensure coordination
60
What controls CPGs in lampreys
locomoter's command centers in the brainstem which is controlled by the basal ganglia (nuclei) in the cerebral hemisphere
61
What do Mauthner (M) neurons mediate
All bony fish have a “fast escape” or “startle response”
62
Which fish has the fastest acceleration from a ‘standing start’
the barracuda
63
Where are M - neurons located
on either side of the brainstem. Large neurons (cell soma 100 um diameter)
64
What do M-neurons detect
vibration and sensory input
65
Axon of M-neurons
on either side of the brainstem. Large neurons (cell soma 100 um diameter)
66
How do M-neurons cause unilateral muscle contraction in fish
Collaterals contact interneurones and motor neurones at all spinal levels
67
First animals to walk on land
First by amphibians such as salamanders … then by reptiles
68
In order for animals to walk on land what is the friction of water replaced by
pull if gravity on land
69
Anatomical concepts of walking on land
1. Antagonistic muscle groups: flexors (bending) and extensors (straightening)
2. Hip and shoulder joints
3. Multi-joint movements
4. Major involvement of the spinal cord
70
How has the cerebellum evolved during the transition onto land
1. Vestibulocerebellum – balance
2. Spinocerebellum – body raised off the ground
3. Neocerebellum – connected to the cerebral cortex for motor coordination
71
What causes alternating steps
flexors and extensors inhibiting each other reciprocally
72
4 phases of walking
1. Flexion (F)
2. First extension (E1)
3. Second extension (E2)
4. Third extension (E3)
73
Spinal reflexes in walking
spinal circuits work without control of the brain
74
muscle groups in walking
Inhibition/stimulation of antagonistic muscle groups: flexors v extensors
75
coordination in walking
Co-ordination of movement of more than one joint
76
Sensory feedback in walking
Sensory feedback controls rate of stepping (cutting dorsal spinal roots interrupts pathway)
77
supra-spinal control in walking
Supra-spinal control (above spinal cord). Ascending sensory pathways run from spinal cord to sensory cortex in cerebral hemisphere. Neighboring motor cortex (and other motor areas stimulated). Descending motor pathways exert control of motor neurones in the spinal cord
78
Why do birds singing
Birdsong is composed of syllables which are characteristic of particular species. Bird song is a learnt behavior
79
Neuroanatomy of birdsong
There is a complex interconnection of nuclei and tracts in the bird brain which control the syrinx to produce the song
80
What does the central nervous system include
brain and spinal cord
81
What does peripheral nervous system include
cranial and spinal nerves
82
what do sensory neurons do
brings sensory information to the CNS from peripheral tissues and organs
83
What do motor neurons do
sends motor commands from the CNS to target organs (muscles, glands)
84
What does the peripheral nervous system split into
1. Somatic nervous system - controls skin and skeletal muscle
2. Autonomic nervous system - control viscera e.g., smooth and cardiac muscle
85
what does the autonomic nervous system split into
1. sympathetic - fight or flight
2. parasympathetic - rest and digest
86
what is the dorsal column ascending pathway split into
gracile fasciculus and cuneate fasciculus
87
What is the spinocerebellular tract responsible for
sending sensory information that helps coordinate the muscles in the trunk and the limbs
88
What does the spinocerebellular tracts split into
the posterior and anterior spinocerebellular tract
89
What does the anterolateral system split into
the lateral spinothalamic tract and the anterior spinothalamic tract
90
What are the 3 ascending (afferent) pathways
dorsal column medial lemnisucs sysyem, spinocerebellar tract and anterolateral (spinothalamic) system
91
What are the 2 descending (efferent) pathways
pyramidal tracts (corticospinal) and extrapyramidal tracts
92
What does the pyramidal (corticospinal) tract split into
lateral and anterior corticospinal tract
93
What does the extrapyramidal tracts split into
rubrospinal tract, reticulospinal tracts, olivospinal tract and vestibulospinal tract
94
location of the dorsal column
at the back of the spinal cord
95
What processes the sensory information in the dorsal column
Sensory information (vibration, discriminative fine touch and proprioception) processed by primary sensory neurons with cell bodies in the dorsal root ganglia
96
Type of communication in the dorsal column
initially ipsilateral (same side of the body) the neurons then cross over at the medulla oblongata so it is now contralateral (to the other side)
97
Where does the spinothalamic tract carry information
from the spine, up the thalamus
98
Spinothalamic tract - where is sensory information processed
Sensory information (pain, temperature, touch and pressure) processed by primary sensory neurons with cell bodies in the dorsal root ganglia
99
Where do neurons decussate (cross over) in the spinothalamic tract
at the point of entry (L5)
100
Communication within the spinothalamic tract
forms synapses with another neuron to create a contralateral pathway
101
What do interneurons connect
functionally related lower motor neurons
102
Are descending pathways efferent or afferent to lower motor neurons
afferent
103
What is the general somatic efferent
motor to skeletal muscle from large ventral horn
104
What is the general visceral efferent
motor to visceral frim ventral horn
105
General visceral afferent
sensation from the visceral
106
General sensory afferent
discriminative touch, proprioception, pain and temperature from skin, joints, muscles
107
Location of the corticospinal tract
passes through the pyramidal structures of the medulla and decussates (crosses over)
108
What does the corticospinal tract control
lower motor neurons (LMNs) that innervate skeletal muscles. Non-stereotyped movements (purposeful movements)
109
What is somatotopy
the orderly arrangement of the nervous system in relation to the parts of the body
110
What do the consequences of the interruption of the descending pathway depend on
level of injury and where and if the tract decussates
111
What does a greater number of neurons mean
more intergration can occur
112
what is neurogenesis
creation of new neurons - is confined to specific areas
113
where is the association cortex located
cerebral cortex outside the primary areas
114
what is the association cortex involved in
communication, memory, planning future behaviour, and thought I.e., complex processes
115
Inter-hemispheric commissures (junctions)
corpus callosum, anterior commissure
116
Function of motor neurons
planning, execution and co-ordination
117
Function of the extrapyramidal system
for stereotyped (repetitive) movements e.g., rocking or headbanging
118
What system is the cerebellum part of
the extrapyramidal system
119
Cerebellum functions
initiating, timing and terminating movements. Cerebellum co-ordinates motor output
120
Examples of grey matter areas within the hemisphere
basal ganglia, thalamus and hypothalamus
121
What is the basal ganglia
A collection of nuceli which produce regulated movements
122
What system controls the basal ganglia
extrapyramidal motor control
123
Major inputs of the basal ganglia
cerebral cortex, thalamus, brainstem
124
Where do the major outputs of the basal ganglia go to
thalamic nuclei, cortex (via thalamus), brain stem
125
Where does the thalamus relay sensory information to
the cerebral cortex (ascending tracts)
126
Function of the thalamus
Activating the cerebral cortex – sleep and consciousness. Emotional effects generating autonomic activity. Co-ordination of visual and motor activity
127
What does the hypothalamus respond to
physiological, environmental and emotional changes that affect the autonomic nervous system
128
What system is the hypothalamus under
limbic system
129
Hypothalamus functions
involvement in thirst, hunger, appetite. Reproduction and associated behavior. Maintenace of homeostasis (e.g., body temperature and water/electrolyte balance). Neuroendocrine control - pituitary gland
130
What does the brainstem connect
brain to spinal cord
131
What is the brainstem involved in
1. The functional composition of cranial nerves III – XII
2. Conveying sensory information go the cortex
3. Conveying motor control from the cortex to motor neurons
4. Cerebellar connections
5. Regulation of the autonomic nervous system
6. Visual and auditory reflexes
7. Alertness and consciousness
8. Life and death (breathing = controlled by medulla oblongata
132
What does the basal ganglia do
enhances desires movement and inhibits unwanted movement- regulation i.e., kick foot and do not wave arms
133
What does the thalamus control
relays sensory info to the cortex i.e., wind direction
133
What does the thalamus control
relays sensory info to the cortex i.e., wind direction
134
What does the cerebral cortex do
planning of voluntary movement o.e., kick the ball between posts
135
What does the cerebellum do
co-ordinates motor output and force of muscle contraction i.e., bring leg forward and hit ball contraction of abdomen to brace
136
What does the brainstem do
conveys sensory info to the cortex and motor info to lower motor neurons
137
What info does the ascending dorsal column pathway send
vibration, proprioception, fine touch
138
What info does the ascending spinothalamic pathway send
pain, temperature, touch and pressurew
139
What info does the descending corticospinal pathway send
voluntary movement of musculature
140
What info does the descending extrapyramidal pathway send
carry motor fibres to spinal cord
141
Key components if a somatic reflex arc
1. sense organ - generator potential
2. Action potential
3. Afferent neuron
4. Synapse - EPSPSs (and IPSPs)
5. Efferent neuron - action potential
6. neuromuscular junction - endoplate potentials
7. muscle
142
Release of neurotransmitter to skeletal muscle is ...
excitatory - acetylcholine
143
Inhibition of skeletal muscle ...
occurs prior at the level of the spinal cord - reciprocal inhibition
144
What does the knee jerk check for
checks that lower motor neurons are functional
145
Knee jerk reflex sequence of events
1. Stimulate patella tendon
2. Activates stretch receptors or muscle spindles within the extensor muscle
3. Activates sensory nerve, synapse to motor neuron (monosynpatic reflex)
4. Extensor muscle (quadriceps) contracts
5. Flexor muscle (hamstring) relaxes
146
Reciprocal inhibition - knee jerk reflex
occurs in the spial cord - there is no involvment of the brain
147
Motor neuron inhibition - knee jerk reflex
sensory neurons travelling from muscle spindle stimulate internueorns that inhibit motor neurons that supply opposing muscle causing quadricep muscle to be unopposed
148
What happens during the crossed extensor reflex
Removing foot from stimulus (flexor contracts and extensor relaxes). Other side of the body stabilises (flexor relaxes and extensor contracts)
149
What does the autonomic system involve
sleeping, eating, thermoregulation, CV control, crying, stress response, light reflex, breathing and respiration, elimination of waste products
150
When does the autonomic nervous system function
without you being aware of it or exerting voluntary control over it - involuntary
151
What does the autonomic system respond to
physiological demands, environmental and emotional demands, controls organs of the body
152
Autonomic nervous system reflex arc
1. Afferent neuron with receptive ending
2. interneurone
3. autonomic preganglionic neuron
4. Autonomic postganglionic neuron
5. Effector
153
What are the 2 subdivisions of the autonomic nervous system
1. Sympathetic nervous system - fight or flight
2. Parasympathetic nervous system - rest and digest
154
How does the sympathetic nervous system and parasympathetic nervous sytem function
antagonistically because they usually have opposing effects on an oragsn
155
When does the parasympathetic nervous system use acetylcholine
for transmission of preganglionic and postganglionic neuron
156
When does the sympathetic nervous system use acetylcholine
transmission of preganglionic neuron
157
When is nicotonic AchR USED
For receptors on postganglionic neuron
158
When is noradrenaline used
sympathetic nervous system - transmitter of postganglionic neuron
159
When is alpha/beta adrenergic receptors used
sympathetic nervous system - receptors on target tissue
160
When is muscarinic AChR used
parasympathetic nervous system - receptors on target tissue
161
What controls all preganglionic autonomic neurons
pathways descending from higher regions of the brain, in particular they hypothalamus
162
Why are postganglionic axons not attached to the target organ
because they need to move in relation to them
163
Parasympathetic outflow of the CNS (I.e., the location of the preganglionic neuron cell bodies)
Cranial: 4 cranial nerve nuclei – controlling secretory glands in the head; two intra-ocular muscles of the eye
Sacral spinal cord S2, 3 and 4 - ‘the emptying nerves’ controlling the large bowel/anus, the bladder and erectile tissue of the ganglia
164
Direction of vagus nerve
leaves the head and enters the thoracic anf abdominal cavities
165
Distribution of the sympathetic outflow of the CNS
relatively unrestricted throughout the body
166
Distribution of parasympathetic outflow
relatively restricted
167
Sympathetic outflow from the CNS
Lateral horn of the spinal cord in: Segments T1 – L2(3). Preganglionic axons synapse. Either: in paravertebral ganglia (sympathetic chain) Or: in prevertebral ganglia (e.g., coeliac plexus)
168
How do postganglionic axons reach their target organs
either by joining peripheral nerves or by running along arteries that supply the target organs
169
How many possible routes are there for sympathetic preganglionic axons
3
170
What is the direct pupillary response
when light is shone directly into one eye and its pupil constricts
171
What is the afferent neuron in the light reflex
projection of the optic nerve to the oculomotor nucleus
172
What causes the pupils to narrow
Short postganglionic fibres travel to the circular muscles of the iris
173
Sympathetic reflexes contributing to thermoregulation
Increase in body temperature -> increased activity in central thermoreceptors (via hypothalamus):
1. Reflex increases sympathetic discharge to sweat glands -> sweating
2. Reflex decreases sympathetic discharge to cutaneous blood vessels -> vasodilation in skin
-> decrease in body temperature
174
What is the enteric nervous system
the innervation of the GI tract is intrinsically controlled in the intetsinal wall
