Nervous System/Hearing Flashcards
1
Q
Neuron
A
single cell w/dendrite, soma, axon hillock, axon (myelin, nods of Ranvier)
*cannot change size of action potentials it transmits
2
Q
Nerve
A
bundle of many different axons from different neurons
3
Q
Soma
A
central body of the neuron
contains the nucleus
4
Q
Axons
A
carry info away from soma
5
Q
Myelin Sheath
A
allow for saltatory conduction
no ions can enter or exit neural axon that’s myelinated
dramatically speeds the movement of action potentials by forcing AP to jump from node to node
CNS - Oligodendrocytes
PNS - Schwaan Cells
6
Q
Dendrite
A
carry info into the soma
7
Q
Axon Hillock
A
initiates action potential
8
Q
Synaptic Cleft
A
small gap between the presynpatic and the postsynaptic neuron
chemicals released into the space to excite the next neuron
9
Q
Synaptic Knob
A
axons terminate in synaptic knobs
form connections with target cells
10
Q
Axon Velocity Increases with
A
increasing myelin
increasing diameter
11
Q
Na+/K+ ATPase
A
3 Na+ out
2 K+ in
w/hydrolysis of 1 ATP molecule
12
Q
potassium leak channels
A
open all the time
allow some of the K+ from the cell to go out into the extracellular space (down the gradient)
13
Q
Resting Membrane Potential
A
-70 mV
14
Q
Sodium leak channels
A
very few
100 K+ leak channels: 1 Na+ leak channels
15
Q
Are neurons the only cells with a resting membrane potential?
A
No. All cells have a resting membrane potential (rmp)
Neurons and muscle tissue use rmp to generate action potentials
16
Q
Depolarization
A
sodium voltage-gated channels open (in response to membrane potential) to allow Na+ into the cell (down the gradient)
Once membrane potential reaches -50mV (threshold), all Na+ channels are opened fully
Channels are closed before threshold potential
Reaches +35 mV before inactivating Na+ channels
17
Q
Threshold potential
A
-50 mV
18
Q
Can an action potential run out of energy and not reach the other end?
A
Action potentials are continually renewed at each point in the axon as they travel
Assuming enough voltage-gated channels, once an action potential starts, it will propagate without a change in amplitude until it reaches a synapse
19
Q
All or none response
A
if membrane potential doesn’t reach the threshold, the voltage-gated sodium channels won’t open up
20
Q
Repolarization
A
- voltage-gated K+ channels open more slowly than the Na+ ones -> respond to the depolarization of the membrane
- membrane potential returns to negative because K+ ions are leaving the cells
- overshoots the resting potential, -90 mV
- K+ voltage-gated channels close
- K+ leak channels and Na+/K+ ATPase bring the membrane back to resting potential
21
Q
Saltatory Conduction
A
rapid jumping conduction in myelinated axons
22
Q
Glial cells
A
specialized, non-neural cells that typically provide structural and metabolic support to neurons
ex. Schwaan cells
23
Q
Schwaan cells
A
PNS
form myelin - increase speed of conduction of APs along axon
24
Q
Oligodendrocytes
A
CNS
form myelin - increase speed of conduction of APs along axon
25
Astrocytes
CNS
Guide neuronal development
Regulate synaptic communication via regulation of neurotransmitter levels
26
Microglia
CNS
| Remove dead cells and debris
27
Ependymal cells
CNS
| produce and circulate cerebrospinal fluid
28
Nernst Equation
Eion = RT/zF = ln [X]outside/[X]inside
```
z= valence of ion
F= Faraday's constant
Eion = equilibrium potential
```
29
Equilibrium potential
membrane potential at which this driving force (gradient) does not exist
no net movement of ions across membrane
30
chemical gradient across membranes
created by relative concentrations of ions on each side of the membrane
31
Electrical gradient across membranes
determined by valence (charge of ion)
32
Absolute refractory period
neuron will not fire another action potential no matter how strong a membrane depolarization is induced
Na+ volt-gate channels inactivated
on the way back down (at the threshold), Na+ channels are closed
33
Relative refractory period
neuron can be induced to transmit an action potential
requires greater depolarization (b/c its hyperpolarized)
from the point where Na+ channels closed to the point where resting membrane potential is established
34
Electrical synapses
```
occur when cytoplasm of 2 cells are joined by gap junctions
not common in nervous system
prominent in smooth and cardiac muscle
excitatory only - depolarizes
bidirectional
```
35
Chemical synapses
found at the end of axons where they meet their target cell
action potential converted into a chemical signal
synaptic cleft present
excitatory (depolarizes) or inhibitory (hyperpolarizes)
unidirectional
36
Steps in chemical synapses
1. action potential reaches end of an axon (synaptic knob)
2. depolarization of presynaptic membrane opens Ca++ voltage-gated channels
3. Ca++ influx causes exocytosis of neurotransmitters stored in secretory vesicles
4. Neurotransmitter molecules diffuse across the narrow synaptic cleft
5. Neurotransmitters bind to receptor proteins (ligand-gated ion channels) in postsynaptic membrane
6. Opening the ion channels alters membrane polarization
7. if threshold is reached, Na+ voltage-gated channels are opened => action potential is initiated
8. Neurotransmitter in the synaptic cleft is degraded/removed to terminate the signal
37
Neurotransmitter Breakdown
reuptake
enzyme (ex. acetylcholinesterase)
glial cells (astrocytes)
38
Each presynaptic neuron can only___
| postsynaptic neuron can respond to ____
release one type of neurotransmitter
| respond to many different neurotransmitters
39
If an inhibitor of acetylcholinesterase is added, what happens to the postsynaptic membrane?
it will be depolarized longer w/each potential
40
Temporal summation
summing up synapses over time
| *increased frequency of action potentials will add up to increase the number of action potentials transmitted
41
Spatial summation
summation over space
| multiple inputs
42
Excitatory postsynaptic potentials (EPSPs)
excitatory neurotransmitters cause postsynaptic depolarization
43
Inhibitory postsynaptic potential (IPSPs)
inhibitory neurotransmitters cause postsynaptic hyperpolarization
44
Peripheral Nervous System (PNS)
receiving info = sensory function
acting on the info = motor function
all nerves and sensory structures outside of the brain and spinal cord
45
Central Nervous System (CNS)
processing info = integrative function
| brain and spinal cord
46
Motor neurons (PNS)
carry info from nervous system to the organs
| efferent neurons = exit CNS
47
Sensory neurons (PNS)
carry info towards the CNS
| afferent neurons = approach CNS
48
Integration (CNS)
interneurons (association neurons)
49
Reflexes
direct motor response -> sensory input (w/o conscious thought)
50
Somatic (PNS)
```
subdivision of PNS
voluntary control of skeletal muscle
stimulation only
ACH only
one neuron from spinal cord to effector organ
```
51
Autonomic (PNS)
subdivision of PNS
involuntary control of glands and smooth muscle
stimulatory or inhibitory
2 neurons from spinal cord to effector organ
ACH, NE
52
Sympathetic system
Subdivision of autonomic, PNS
"flight or fight" "4 Fs = Flight, Fight, Fright, Freak (sex)"
ACH at ganglion, NE at organ
increase blood flow to skeletal muscle
increase body activity :
-increase HR, blood pressure, breathing rate, sweating
-pupils and bronchioles dilate
53
Parasympathetic system
```
subdivision of autonomic, PNS
"rest and digest"
ACH at ganglion and organ
increase blood flow to the GI tract
increase GI motility
decrease body activity:
-decrease HR, blood pressure, breathing rate, sweating
-pupils and bronchioles constrict
```
54
Catecholamines (epinephrine, norepinephrine)
housed in the adrenal medulla
| releases EPI and NOREPI
55
Cerebrospinal Fluid (CSF)
clear liquid
CNS floats in it
shock absorption
exchange of nutrients/waste
56
spinal cord
protected by CSF and vertebral column
pathway for info to and from the brain
site for information integration and processing
basic reflexes (simple spinal reflexes)
involved in primitive processes (walking, urination, sex organ function)
57
medulla oblongata
part of hind brain
connected to the brain stem
relays info between other areas of the brain
controls AUTONOMIC FUNCTIONS (breathing, heart rate)
contains respiratory rhythmicity centers
58
pons
```
part of the hind brain
balance and equilibrium
antigravity posture
controls some autonomic functions
receive info from vestibular apparatus in the inner ear -> monitors acceleration and position due to gravity
```
59
Cerebellum
part of the hind brain
balance and coordination
integrating center where complex movements are coordinated
receive info from vestibular apparatus in the inner ear -> monitors acceleration and position due to gravity
60
Midbrain
relays visual and auditory info
contains much of the reticular activating system (RAS) -> responsible for arousal/wakefulness
startle reflexes
61
Thalamus
part of the diencephalon
| contains relay and processing centers for sensory info
62
Hypothalamus
part of the diencephalon
maintain homeostasis
contains centers for controlling emotions and autonomic functions
pituitary gland => primary link between nervous and endocrine systems
63
Telencephalon
left hemisphere = controls right side of body; responsible for speech
right hemisphere = controls left side of the body; responsible for visual-spatial reasoning, music
64
Corpus collosum
thick bundle of axons that connect the cerebral hemispheres
| if cut => split brain = 2 independent cortices
65
Cerebrum
largest region of human brain
cerebral cortex = 4 mm of gray matter (unmyelineated axons) on the outside; . houses the conscious mind
responsible for thought processes and intellectual functions
process somatic sensory and motor info
contain 4 lobes: frontal, parietal, temporal, occipital
66
Frontal lobe
all voluntary movement
reasoning skills
problem solving
67
Parietal lobe
```
general sensations (touch, temp)
gustation (taste)
```
68
Temporal lobe
```
process auditory and olfactory sensations
-contains olfactory bulbs
short-term memory
language comprehension
emotion
```
69
Occipital lobe
visual sensation
70
Basal nuclei (basal ganglia)
composed of gray matter
voluntary motor control
procedural learning related to habits
works with cerebellum to control coordination of movements
-basal ganglia = inhibitory (prevents excess movement)
-cerebellum = excitatory
71
Limbic system
contains structures such as amygdala (fear), hippocampus (memory)
emotion, memory
72
All neurons entering/exiting the CNS are carried by __ pairs of cranial nerves and __ pairs of spinal nerves
12 pairs of cranial nerves
| 31 pairs of spinal nerves
73
Cranial nerves
convey sensory and motor info to and from brain stem
74
Spinal nerves
convey sensory and motor info to and from spinal cord
75
Vagus nerve
very important cranial nerve
important in parasympathetic: decreases HR, increases GI activity
bundle of axons end in ganglia on the surface of the target organ
76
All somatic motor neurons ___
innervate skeletal muscle
| use Ach
77
All somatic sensory neurons ___
have long dendrites extending from sensory receptor toward the soma (just outside the CNS in dorsal root ganglion)
78
dorsal root ganglion
bunch of somatic and autonomic sensory neuron cell bodies located just dorsal to the spinal cord
79
All autonomic preganglion neurons release ____
Acetylcholine (Ach)
80
All parasympathetic postganglion neurons release ____
Ach
81
Nearly all sympathetic postganglion neurons realease ___
Norepinephrine (NE)
82
Sympathetic pre/postganglion
| lenght, location
```
preganglion = long; located in thoracolumbar = thoracic and lumbar spinal cord
postganglion = short
```
83
Parasympathetic pre/postganglion
| lenght, location
```
preganglion = short ; located in craniosacral = brainstem and sacral (towards tail bone) spinal cord
postganglion = long
```
84
Adrenal medulla
part of the sympathetic nervous system
| releases epinephrine = stimulation of heart
85
Sensation
act of receiving info
86
Perception
act of organizing, assimilating, and interpreting sensory info into useful, meaningful info
87
Sensory Repectors
detect 1 type of stimulus from either internal/external stimulus
receives only 1 kind of info
88
Mechanoreceptors
respond to mechanical disturbances (pressure, stretch, vibrations)
89
Nocioreceptors
respond to pain
stimulated by tissue injury
DO NOT ADAPT under any circumstances
90
Thermoreceptors
respond to temp
91
Chemoreceptors
respond to chemical stimuli
92
Photoreceptors (Electromagnetic receptors)
respond to electromagnetic waves
93
4 properties of sensory stimuli communicated to the CNS
1. Modality = type of stimulus
2. location = communicated by receptive field of receptor sending the signal
3. intensity = frequency of action potentials
4. duration = may or may not be coded explicitly
- tonic/phasic receptors
94
Tonic receptors
fire action potentials as long as the stimulus continues
95
Phasic receptors
only fire action potentials when stimulus begins
| do not explicitly communicate the duration of the stimulus
96
Adaptation
decrease in firing frequency when intensity of a stimulus remains constant
97
Proprioception (kinesthetic sense)
awareness of self
| essential for coordinated motion
98
Taste buds
bunch of specialized epithelial cells
| have taste pore w/taste hairs = detect food chemicals
99
Bones in the middle ear (malleus, incus, stapes) are arranged in a way to _____ sound vibrations
amplify
100
Vibrations of the oval window creates ____ ______
pressures waves
101
Organ of Corti
primary site at which auditory stimuli are detected
has hair cells that brush the tectorial membrane
in the cochlear duct
102
From Sound to Hearing
sound waves-> auricle -> external auditory canal -> tympanic membrane (ear drum) -> malleus -> incus -> stapes -> oval window -> perilymph -> endolymph -> basilar membrane -> auditory hair cells -> tectorial membrane -> neurotransmitters stimulate bipolar auditory neurons -> brain -> perception
103
Pitch
frequency
distinguished by which regions of basilar membrane vibrate
low frequency (long wavelength) = stimulate hair cells at apex of cochlear duct (furthest away from the oval window)
high frequency (short wavelength) = stimulate hair cells at base of cochlea (closest to the oval window)
104
Large vibrations cause
more frequent action potentials in auditory neurons
105
If auditory nerve is severed ___
no hearing of any kind is possible
106
Bone conductance can ____ and result in ____ if the middle ear is nonfunctional
still stimulate the cochlea
| result in hearing
107
Cones
extreme visual acuity
concentrated in the fovea (focal point)
require abundant light
color vision depends on red, blue, green
108
What physical difference allows cones to absorb red/blue/green light?
each type of cone make a particular pigment protein (opsin) which is specialized to change conformation when light of the appropriate frequency strikes it
109
Emmetropia (normal vision)
incoming light rays are converged to the retina
110
Myopia (nearsightedness)
too much refraction at lens (ciliary muscles too strong) or abnormally long eyeball results in a focal length that is too short
Use diverging lens (concave) to correct
111
Hyperopia (farsightedness)
too little refraction at the lens (ciliary muscles weak) or abnormally short eyeball => focal length is too long
use converging lens (convex) to correct
112
Absolute Threshold
minimum stimulus required to activate a sensory receptor 50% of the time
113
Differential Threshold
| Just Noticeable Difference
minimum noticeable difference between any 2 sensory stimuli 50% of the time
114
Weber's law
two stimuli must differ by a constant proportion for the difference to be perceptible
115
Why can't older people hear higher frequencies?
Loud sounds can mechanically harm the hair cells causing them to die
Once hair cells die, they NEVER regrow
Hair cell that detect high frequency are the smallest and most easily damaged
Loss of hair cell = loss of hearing
