Nervous System Flashcards
1
Q
two components of peripheral nervous system
A
- autonomic nervous system
- somatic nervous system
2
Q
two comonents of central nervous system
A
- spinal cord
- brain
3
Q
three divisions of the brain
A
- forebrain
- midbrain
- hindbrain
4
Q
two subdivisions of hindbrain
A
myelencephalon and metencephalon
5
Q
what does mylencephalon contain
A
medulla oblongata
6
Q
where is medulla oblongata found
A
most posterior part of brain, bordering spinal cord
7
Q
medulla oblongata purpose
A
contains nuclei that control vital functions such as breathing and skeleton muscle tone
8
Q
two brain parts contained in metencephalon
A
cerebellum and pons
9
Q
cerebellum purpose
A
- recieves information from sensory systems, muscles and vestibular system
- co-ordinates this information to produce smooth movements
10
Q
example of damage to cerebellum
A
cerebral palsy
11
Q
what does damage to cerebellum do
A
impairs walking, balance, posture and skilled-motor activity
12
Q
where is pons found
A
bulge on brainstem
13
Q
pons function
A
involved in sleep and arousal
14
Q
main subdivision of midbrain
A
mesencephalon
15
Q
mesencephalon purpose
A
- Controls basic physiological functions (breathing, swallowing, heartbeat)
- Gates sensory and motor information
16
Q
red nucleus function
midbrain
A
co-ordinates sensorimotor information
17
Q
substantia nigra function
midbrain
A
cells make dopamine and project to basal ganglia
18
Q
Periaqueductal Grey Matter function
midbrain
A
involved in pain supression due to high concentration of endorphins
19
Q
two subdivisions of forebrain
A
diencephalon and telencephalon
20
Q
two main components of diencephalon
A
thalamus and hypothalamus
21
Q
how does thalamus work
A
- Separate but interconnected nuclei recieve information from sensory systems and relay it to sensory processing areas in the cortex
- Relay system and can thus influence almost all of brain
- May also play role in learning and memory
22
Q
what is hypothalamus made up of
A
22 nuclei and pituitary gland
23
Q
hypothalamus function
A
- controls autonomic and endocrine systems
- controls key aspects of behaviour including feeding, sex, sleep, temperature regulation and emotional behaviour
24
Q
what are the hemispheres of the telencephalon separated by
A
longitudinal fissure
25
what are the hemispheres of the telencephalon connected by
corpus collosum
26
what is the corpus collosum
a bundle of nerve fibres
27
what is a fissure
deep cleft in surface of brain
28
what is a sulcus
shallow cleft in surface of brain
29
what is a gyrus
ridge in surface of brain
30
why is cortex referred to as grey matter
because there is predominately cells and they give it a grey appearance
31
where is white matter in the telencephalon
runs beneath cortex
32
what is white matter
axons covered by the myelin sheath
33
two functions of spinal cord
- neuronal link between brain and PNS
- integrating centre for spinal reflexes
34
how many spinal nerves are there
31 pairs emerging from spinal cord through spaces formed between vertebrae
35
dorsal root of spinal cord
afferent sensory
36
ventral root of spinal cord
efferent motor
37
what is spinal cord made up of
internal grey matter (neurons) surrounded by white matter (fibres) in periphery
38
what is phrenology
the idea that each part of the brain is specialized in a certain faculty, and the greater in size these areas are, the greater the tendencies towards those faculties are
39
is phrenology a valid scientific theory
nope
40
value of phrenology
- first time a specific function was associated with a specific brain region
- hints to the idea of brain plasticity
41
brocca's aphasia
problems producing language
42
receptive aphasia (wernicke)
problems comprehending language
43
how else can aphasia occur
damage to the bundle of axons connecting Brocca's and Wernicke's areas
44
what is a neuron
most basic unit of nervous system
generates electrical signals and communicates them to other neurons
45
cell body
- contains nucleus and organelles
- sends projections
46
dendrite
- receives signals from environment or other neurons
- some contain spines where synapses occur
47
axons
- begin at axon hillock (axonal cone)
- can travel up to 1 meter
- relays information in the form of chemicals
48
presynaptic neuron
neuron which sends information
49
postsynaptic neuron
neuron which recieves information
50
what are action potentials
a nerve impulse (electrical signal) which is generated and acted upon
51
what is a plasma membrane
lipid bilayer used as a barrier
52
what are plasma membranes made up of
- phospholipids
- glycolipids
- cholesterol
- membrane proteins
53
phospholipids
| membrane composition
- hydrophilic phosphate head
- hydrophobic fatty acid tail
54
glycolipids
| plasma membrane composition
lipids modified by sugars in the extracellular side
55
cholesterol purpose
| membrane composition
essential for maintenance of membrane fluidity
56
simple diffusion
- does not apply to ions: only small, uncharged molecules such as gases
- passive transport
57
electrochemical gradient
- determining force for ion transport
- neural membrane is negatively charged in the cytoplasmic side and positively charged on the extracellular side
- the electrochemical gradient is the combination of concentration and charge differences across the membrane
58
facilitated diffusion
- moves down a gradient
- main driving force for ions
- passive transport
59
carrier proteins
bind solutes tightly and undergo conformational changes
60
ion channels
selective pores which let specific ions in
61
active transport
energy is required to move a substance across a membrane against its concentration gradient
62
why must the electrochemical gradient be restored
because the neuron will lost its ability to get electrically excited
63
how is the electrochemical gradient restored
- exchangers: transport two different ions, one with the concentration gradient, one against. the energy generated by the first is used to carry the second
- ATPase pumps: break down ATP to obtain necessary energy to transport ion against gradient
64
charge (Q)
arises from a net imbalance in the number of positively and negatively charged particles in a given place
65
Current (I)
a flow of electrically charged particles, in the fluids of the body these charged particles include Na+, K+ and Cl-
66
Voltage (V)
a measure of the potential difference between two points, one of which is at a positive potential relative to the other. An electrical voltage represents an electrical potential energy gradient, down which charged particles would like to move, if permitted.
67
what happens when a cell is not stimulated
its under resting conditions and the net charge of its interior is maintained
68
electrical gradient
- influenced by overall electrical charge
- positive ions would flow towards areas of negative charge
69
chemical gradient
- influenced by individual concentration of a particular ion
- all ions move from areas of high to low concentrations
70
what does the direction an ion moves in depend on?
- overall net effect of electrical and chemical gradients
- permeability of membrane to ion
71
what maintains the electrochemical gradient and why
* Na+K+ pump
* because there is more sodium inside cell and potassium outside cell, meaning when channels are open sodium leaves and potassium comes in
* they must make it back to original side at some point
72
why is ionic imbalance important
- intracellular pH control
- osmotic control
- transport
- excitability
73
steps of Na+K+ pump
1. binding cytoplamsic Na+ stimulates autophosphorylation (ATP)
2. phosphorlyation causes conformational changes
3. Na+ is liberated outside and K+ binding sites are exposed inside
4. Binding K+ triggers release of phosphate
5. Release of phosphate restores original conformation
6. K+ is released and Na+ binding sites are exposed again in the cytoplasm
74
equilibrium potential
the electrical potential difference that exatly counterbalances diffusion due to concentration difference
75
equilibrium potential for K+
-90mV
76
equilibrium potential for Na+
+60mV
77
equlibrium potential for Cl-
-70mV
78
what are ion channels
- involve integral proteins that span membrane repetitively
- central pore so ions can diffuse with polar amino acids forming a selective filter
- composition of the pore differs in each channel
79
three types of ion channels
- voltage-gated
- ligand-gated
- mechanically-gated
80
what are ligand gated ion channels
opening relies on binding of a ligand which is normally extracellular fluid
81
voltage-gated Na+ channel steps
1. Voltage-gated Na+ and K+ channels are closed in resting state
2. A stimulus opens the activation gate of some Na+ channels depolarizing membrane potential. If threshold is reached, more Na+ channels open, triggering an action potential.
3. Above this threshold, potential activation gates of all Na+ channels are open. K+ channels are mostly closed but slowly begin to open.
4. The Na+ channel inactivation gates close and K+ channels are fully open. Efflux of K+ from the cell drops membrane potential back to and below resting potential.
5. Both gates of Na+ channel are closed but K+ channels are still open. Continued efflux of K+ keeps potential below resting level.
82
absolute refractory period
- a period of complete resistance to stimulation
- inactivation of Na+ channels means that after an action potential there is a brief period where no other action potential can be generated
83
relative refractory period
- a period of partial resistance to stimulation
- lasts as long as K+ channels are open
- strong stimulus can trigger a new action potential
84
contiguous conduction
conduction of action potentials in unmyelinated fibres
85
conduction speed of contiguous conduction
rate of 10m/s so relatively slow
86
c-fibres
- afferent fibres that carry sensory information from skin and muscles to brain
- unmyelinated
87
what does damage to c-fibres cause
neuropathic pain
88
what does axon potential speed depend on
- internal resistance of axon
- resistance of axonal membrane
89
ow to have fast axon potential propagation
- wide axon
- insulated axon (increases membrane resistance)
90
salatory conduction
when myelin surrounds and insulates consecutive segments of axons in the PNS (schwann cells) and CNS (oligodendrocytes)
91
myelin
membrane component of glial cells
92
what is multiple sclerosis
- autoimmune disease
- myelin sheathe degenerates and forms hardened scars (sclerosis)
- affected axons also slowly degenerate
- results in slowing and eventual block of AP conduction
93
perception
conscious interpretation of the external world derived from sensory input
94
stimulus
a change detectable by the body
95
stimulus to action potential pathway
Stimulus → Receptor → Receptor potential → Action potential (in afferent fibre)
96
sensory transduction
srimulus to receptor potential - changing the energy of the stimulus to electrical energy which takes place at the cellular receptor
97
sensory system composition
sensory receptors, their axonal pathways and targer areas in the brain involved in perception
98
extroceptors
receptors outside of the body
99
introceptors
receptors inside the body
100
name five sensory receptors
- photoreceptors
- mechanoreceptors
- thermoreceptors
- chemoreceptors
- nociceptors
101
sense associated with photoreceptors
vision
102
example of a stimulus that triggers photoreceptors
light
103
senses associated with mechanoreceptors
- touch
- balance
- hearing
- proprioceptors
104
example of a stimulus that triggers mechanoreceptors
mechanical energy (stretching muscle, hair cell movement)
105
sense associated with thermoreceptors
temperature
106
examples of aa stimulus that triggers thermoreceptors
heat and cold
107
senses associated with chemoreceptors
- taste
- smell
108
stimulus that triggers chemoreceptors
specific chemicals
109
sense associated with nociceptors
pain
110
examples of a stimulus that triggers nociceptors
- excessive pressure
- excessive temperature
- certain chemicals
111
two factors that impact nerve fibre velocity
- axon diameter
- myelin sheath
112
how does axon diameter impact nerve fibre velocity
larger diameter has lower resistance for the current to flow down the length of the axon
113
graded potential
what a stimulus induces in a receptor cell or a free nerve ending
114
how are graded potentials different to action potentials
GP: proportional to stimulus strength
AP: all or nothing
115
what shows stimulus intensity
- the action potential frequency
- the number of receptors activated
116
where do receptor potentials occur
in seperate receptor cells
117
how do receptor potentials work
- stimulus opens ion channels in receptor causing graded membrane potential
- receptor cell releases chemical messenger
- chemical messenger opens ion channels in afferent neuron action potential generating region
- if the threshold is reached, an action potential is generated
118
where do generated potentials occur
in specialised nerve endings
119
how do generated potentials work
- stimulus opens ion channel in receptor causing local current flow
- local current flow opne ion channels in afferent neuron action potential generating region
- if the threshold is reached, an action potential is generated
120
receptive field
Somewhere in the body where the presence of a stimulus will alter the firing of a sensory neuron
121
examples of receptive fields
- cochlea hair
- a piece of skin
- retina
122
four things necessary for receptors to work
- receptor must have specificity for the stimulus energy
- the receptors receptive field must be stimulated
- stimulated energy mist be converted into a graded potential
- a generated potenial in the associated sensory neuron must reach the threshold
123
transducation
the process of converting energy forms into electrical signals via a receptor/generator potential which triggers an action potential if it i s large enough to reach the threshold
124
adaptation
When a long-lasting stimulus changes the receptors sensitivity to it
125
how does adaptation mostly occur
by rapidly-adapting receptors
126
how do rapidly adapting receptors work
- pressure, touch, hearing smell
- adapt very quickyl - repsond less if stimulus remains constant (frequently exhibits an off response when stimulus is removed)
- allows us to shut out background noise
127
how does adaptation occasionally occur
by slowly adapting receptors
128
how do slowly-adapting receptors work
- pain, proprioception, chemicals in blood or CSF
- adapt slowly, continue to respond even when stimulus remains constant
- continuous input is useful for some modalities because the body needs to make continuous responses to that kind of information, or because the stimulus needs to be constantly evaluated
129
proportional receptors
provide continous information about the stimulus
130
differential receptors
signals change in stimulus insensity
131
two types of adaption mechanisms
mechancal and chemical
132
how does mechanical adaption work
- physical mechanical mechanism that induces the decrease in the response of a receptor neuron
- specialised receptor endings in Pacinian cells of skin
133
how does mechanical adaption work
- physical mechanical mechanism that induces the decrease in the response of a receptor neuron
- specialised receptor endings in Pacinian cells of skin
134
how does chemical adapation work
- membrane enzymes or intracellular signaling mechanisms induce response termination
- common in olfactory responses
135
three divisions of somatosensory system
- cutaneous sensations (skin)
- visceeral (internal organs and deep tissues)
- proprioception (awareness of position of limbs and body in space
136
name five sensory receptors present in skin
* meissner's corpuscle
* merkel receptors
* ruffini ending
* pacianian corpuscle
* bare/free nerve endings
137
what does meissner's corpuscle respond to
flutter and stroking movements
138
what do merkel receptors sense
steady pressure and texture
139
what does ruffini ending respond to
responds to skin stretch
140
what does pacinian corpuscle sense
vibration
141
what do free nerve endings respond to
pain and heat
142
receptive field
region of space in which the presence of a stimulus will alter the firing of a neuron
143
what haopens when many primary sensory neurons converge on a single secondary neuron
- poor touch discrimination
- creates a large receptive field
- two stimuli are perceived as a single point because both fall within the same receptive field
144
what happens when few primary sensory neurons converge on a single secondary neuron
- good touch discrimination
- receptive fields are much smaller
- two stimuli activate seperate pathways and are thus perceived as distinct
145
why do fingers have a better sense of touch
- higher density of mechnoreceptors
- enriched in receptors with snall receptive fields
- more brain tissue dedicated to integrate info coming from fingertips
146
where are 3rd order afferent neurons present
thalamus
147
where do 3rd order afferent neurons project to
somatosensory cortex
148
where are 2nd order afferent neurons
spinal cord
149
what do 2nd order afferent neurons synapse with
3rd order afferents in the thalamus
150
what are 1st order neurons also known as
primary sensory neurons
151
where are 1st order afferent neuron cell bodies
peripheral sensory ganglion
152
what do 1st order afferent neuron peripheral axons do
form or innervates receptors
153
1st order afferent neuron central axon purpose
they synapse with 2nd order afferent neurons
154
what do lesions in the somatosensory cortex cause
impairment of somatic sensations
155
somototopic representation
representation of the body mapped on cortical surface
156
how does phantom limb syndrome work
ascending pathways stimulate the somatosensory cortex from adjacent representations but descendent pathways interpret this incorrectly
157
agnosia
inability to recognise an object even though simple sensory skills are normal
158
what does posterior parietal lesions cause
spatial neglect
159
spatial neglect symptoms
- ignore contralateral extrapersonal space
- deny body parts
- incompete copy of drawing
160
how do nociceptors work
- free nerve endings found in every tissue execpt the brain
- activated by intesne thermal, mechanical or chemical stimuli
- tissue irritation or injury releases chemicals suach as prostaglandins, bradykinin, H+, K+ etc. that stimulate nociceptors
- connected to C fibres
161
Wavelength (λ)
distance between two peaks of an electromagnetic wave
162
reflection
bouncing of light off a surface
163
refraction
bending of light rays when they from one media to the other
164
aborption
transfer of light energy to a particle
165
pathway from retina to brain
Photoreceptors → horizontal cells → bipolar cells → amacrine cells → ganglion cells
166
what are horizontal and amacrine cells
local interneurons which modulate transmission onto bipolar and ganglion cells
167
name the seven layers of the retina
- pigmented epithelium
- photoreceptor outer segment
- outer nuclear layer
- outer plexiform
- inner nuclear layer
- inner plexiform
- ganglion cell layer
168
what are photoreceptors
receptors (rods and cones) tha transform electromagnetic radiation into electrical signals
169
how many photopigments do rods have
one
170
do rods see in black & white or colour
black and white
171
what is the photopigment contained by rods called
rhodopsin
172
what is rhodopsin composed of
retinal and opsin
173
rod sensitivity to light
highly sensitive
174
what kind of vision do rods provide
night vision
175
where are rods located
all over retina except for fovea
176
how mny rods in total
100 million
177
do cones pick up on black & white or colour
colour
178
how do cones see colour
- each cone is sensitive to one type of light
- brain assigns colours based on readout of 3 cone types
- if all types of cones are equally active, they see white light
179
how many photopigments do cones contain
3 different opsins (diff. absorption for green, red, or blue light)
180
cone sensitivity to light
low sensitivity
181
type of vision provided by cones
daylight sight
182
where are cones located
mainly in macula (especially the centre which is called the fovea)
183
how many cones are there
6 million
184
phototransduction
conversion of light energy into membrane potentials
185
what happens to photoreceptors in the dark
theyare depolarised
186
how are photoreceptors depolarised
- guanylyl cyclase produces cGMP in the dark
- cGMP binds and activates Na+ channels
- Na+ influx depolarises the membrane
- membrane depolarisation induces liberation of glutamate
187
what happens to photoreceptors in the light
they are hyperpolarised
188
how are photoreceptors hyperpolarised
- light activates rhodopsin and a G protein called transducin
- transducin binding GTP activates PDE (phosphodiesterase)
- active PDE breaks down cGMP
- low levels of cGMP promote channel closing
- Na+ influx decreases and the membrane hyperpolarises
- membrane hyperpolarization reduces glutamate release
189
what does glutamate do to bipolar cells
either depolarises or hyperpolarises them
190
what is the bipolar cell receptive field
area of retina where a stimulus will evoke a response in that bipolar cell
191
receptive field centre
direct connection from photoreceptors
192
receotive field surround
connection from photoreceptors through horizontal cells
193
receptive field centre and surround relationship
whatever response is triggered in the centre, the opposite will be triggered in the surround
194
ganglion cells receptive field
area of the retina where a stimulus will evoke a response in that ganglion cell
195
what do ganglion cells do
generate action potentials and are the only output of information to the rest of the brain
196
what happens when light is shone on centre of the receptive field of a ganglion cell
ganglion produces action potentials
197
what happens when light is shone on the surround of a ganglion cell receptive field
ganglion decreases action potential
198
how is action potential firing rate affected in a ganglion cell
* no change if centre and surround are in same level of illumination
* greatest difference when there is large contrast between centre and surround
199
two systems contained within the ear
- vestibular
- auditory
200
vestibular system
* inform brain of the position of the head and body and how they are moving
* balance
201
auditory system
- detect sounds
- locate them in space
- identify sound nuances
- hearing
202
pitch
depends on frequency
203
intensity
depends on amplitude
204
timbre (quality)
depends on overtones
205
auditory system steps
1. sound waves move tympanic membrane
2. tympanic membrane moves ossicles
3. ossicles move oval window membrane
4. movement in oval window moves fluid in cochlea
5. fluid in cochlea induces response in sensory neurons
206
how do sound waves reach the brain
Auditory receptors (cochlea) → brainstem → thalamus (medial geniculate nucleus) → primary auditory cortex
207
explan attenuation reflex
- malleus and stapes linked to skull by muscles
- after a loud sound the brain will diminish hearing sensitivity by tensing the muscles
- this leads to impairment of the amplification sysetem
208
attenuation reflex functions
- delayed protection
- adatation to loud sounds
- not hearing our own speech
209
what happens at the apex of the cochlea
scala vestibuli and scala tympani communicate
210
where does perilymph flow
from vestibuli to tympani when the stapes taps the oval window
211
where does endolymph flow
inside the scala media
212
concentration of endolymph inside the scala media
high in K+ and low in Na+
213
how are waves generated in the basilar membrane
perilymph is displaced, which then displaces endolymph which in turn generates the waves
214
where are high frequencies detected by the cochlea
near the narrow and stiff oval window
215
where are low frequencies detected in the cochlea
near the wide and flexible apex
216
what happens when the sterocilia are bent in direction A
- ion channel opens
- K+ influx occurs
- cell is depolarised
217
what happens when the steriocilia are straight
- ion channel is semiclosed
- K+ influx is at resting potential
218
what happens when cilia are bent in direction B (opposite to A)
- ion channel is closed
- cell is hyperpolarised
219
what does sound do outer hair cell
depolarises them
220
what does the depolarisation of outer hair cells cause
- induces cell to shorten or lengthen (electromotility)
- the change of length amplifies teh movemnt of the basilar membrane
221
mechanism of hearing
1. sound waves induce oscillation in the tympanic membrane
2. pressure waves are transmitted through the ossicles to the oval window
3. pressure on the oval window induces movement of the basilar membrane
4. displacement of basilar membrane depolarises hair cells
5. depolarisation of outer hair cells change their morphology, amplifying the signal
6. depolarisation of inner hair cells induce neurotransmtter release
7. neurotransmitter evokes action potential in the cochlear nerve
222
mechanism of hearing
1. sound waves induce oscillation in the tympanic membrane
2. pressure waves are transmitted through the ossicles to the oval window
3. pressure on the oval window induces movement of the basilar membrane
4. displacement of basilar membrane depolarises hair cells
5. depolarisation of outer hair cells change their morphology, amplifying the signal
6. depolarisation of inner hair cells induce neurotransmtter release
7. neurotransmitter evokes action potential in the cochlear nerve
223
when is a cochlear implant useful
when the cause of deafness is sensorineural ie. damage or death of hair cells but a mostly functioning auditory nerve
224
how does a cochlear imlpant differetitate frequencies
uses natural tonotopy
