physiology Flashcards
1
Q
If a mechanically-gate potassium channel opens and potassium moves down its concentration gradient, the cell becomes hyperpolarized
A
True
2
Q
A graded potential is triggered at the axon hillock by opening the chemically-gated channels found there
A
False
3
Q
Action potentials are all or none and should be the same aplitude for a given neuron
A
True
4
Q
Action potentials differ in their size/amplitude, just like graded potentials
A
False
5
Q
K+ Leaves the cell, carrying its positive charge out
A
True
6
Q
Graded potentials happen at the dendrites or cell body. Action potentials are triggered at the axon hillock
A
True
7
Q
A hormone is secreted and its receptor is found in the cytoplasm of the target cell
A
It is lipophilic
8
Q
Thyroid Hormone
A
It is an amine, TSH is actually a protein hormone made by the anterior pituitary. Therefore it is hydrophilic, binds to plasma membrane receptors, and does nto need to be trasnported bound to plasma proteins. TSH is released in response to TRH once TRH binds to endocrine cells of he anterior pituitary.
9
Q
Why are the receptive fields of Merkel’s disks and Meissner’s corpuscles smaller than those of Ruffini’s endings and Pacinian corpuscles
A
Merkel’s disks and Meissner’s corpuscles are located in the upper layers of the skin. Do not respond to mechanical perturbations farther away
10
Q
What happens to restore the resting membrane potential after depolarization
A
Potassium voltage-gated channels open, allowing potassium ions to flow out of the neuron
11
Q
In action potentials, what happens right after calcium ions enter
A
Synpatic vesicles fuse with the plasma membrane and release their contents
12
Q
What is the difference between the anterior and posterior pituitary
A
The posterior releases hormones from the hypothalamus and the anterior creates its own hormones which then get released into the blood
13
Q
A person is experiecing low blood pressure, weight gain, fatigue, and a sensitivty to cold temperatures. What is the likely cause of these symptoms?
A
The hypothalamus is not producing enough thryotropin relasing hormone
14
Q
Endocytosis
A
Transport for very large molecules (proteins)
Molecules get invaginated andmove in like a balloon
15
Q
Exocytosis
A
Transport for very large molecules
Secretory vesicle fuses with plasma membrane allowing to leave membrane
16
Q
Homeostasis
A
Ability of the body to maintain a relatively constant internal environment
Dynamic & self regulatory process
17
Q
Negative Feedback Control System
A
Maintains homeostasis
Local control (cell/tissue) -> Small area of the body
Long distance control (Nervous system)
18
Q
Intracellular fluid
A
Fluid found within cells
Most of body fluids are within cells
19
Q
Extracellular fluid
A
Fluid found outside of the cells
Plasma - Fluid in blood vessels outside of cells
Interstitial fluid- fluid directy surrounding cells, not in blood vessels
20
Q
Plasma membrane
A
Separates inside of the cell from outside
21
Q
Different Ion concentrations inside & outside
A
Na,Cl, Ca -> higher in the extracellular fluid
K -> higher in the intracellular fluid
22
Q
Cell Membrane
A
Composition of interstitial fluid = plasma
Composition of intercellular fluid =/ extracellular fluid
23
Q
Function of the cell membrane
A
Physical separation from the environment
Regulation of exchange with the environment
Communication of the cell with its environment
24
Q
Cell Membrane separates interstitial and intracellular fluid
A
Selectively permeable
Contains transport mechanisms which favor the ion distribution
25
Cell Membrane Structure
Glycerol/phosphate heads
Hydrophilic
26
Cell Membrane Structure
Fatty acid tails
Hydrophobic
27
Cell Membrane Structure
Glycoprotein/Glycolipid
Self recognition (Transplats/blood type)
28
Cell Membrane Structure
Choleterol
Fluidity (How fluid the membrane is, how much movement)
29
Cell Membrane Structure
Trans-membrane protein
Exchange, communicate, adhere, enzymes ( mediations, adhering cells)
30
Cell Membrane Structure
Peripheral protein
Structure, enzyme (binding skeleton structure, for cell shape)
31
Transmembrane Protein
Spans the entirety of the cell membrane
Permit the transport of specific substances
32
Functions of membrane proteins
Ion channels
Enyzymes
Receptros
Membrane carriers
33
Types of membrane transport
Simple diffusion
Diffusion through protein channels
Facilitate transpor
Active transport
Endocytosis/ exoctosis
34
Diffusion
Movement of a molecule
Hight to low concentration
Until it reaches equilibrium
35
Simple diffusion
Substances like O2, CO2 OH
Substances cross the membrane unassisted molecules unassisted
Molecules: hydrophobic lipid substances
36
Simple Diffusion factors
Lipid solubility (organic compounds that are insoluble in water)
Size (Substances too large will not cross)
Membrane composition
37
Rate of diffusion
Surface area (more molecules across if larger membrane surface area)
Thickness (How much area does the substance have to cross)
concentration gradiet (higher gradient higher speed)
38
Ficks law of diffusion
Rate of diffusion = SA Concentration gradient/membrane thickness
Higher SA & higher concentration gradient = higher the rate of diffusion
Higher membrane thickness = slower the rate of diffusion
39
Channel mediated diffusion
Ions & water travel because they are hydrophilic
40
Ion channels
Tunnels in the membrane
Allowing charged molecules to move across membrane
41
Ion Channels
Factors
Higher Concentration Gradient
Results in a Higher speed
Sodium high one side & Low on the other
(2) # Channels Available ⇒ Faster Transport
Size
Sodium, Potassium, and Calcium are all cation channels
May not fit in the same channel due to size
Charge
Transmembrane protein have amino acids with charges
Different charge = attraction & same charge = repel
42
Water mediated diffusion
Water moves through channels called aquaporins
Rate of diffusion
concentration gradient & # of channels available
If a cell does not have aquaproins it is impermeable to water
43
Facilitate diffusion/facilitate transport
Requires a transmembrane protein to change confirmation
Move and flip confirmation, transporting molecule to the other side
Contains large hydrophilic substances (Glucose & amino acids)
44
Carrier Proteins
Selective will saturate, can be inhibited
Will saturate
Controlled by lengths of change confirmation
Similar shape & size substances (drugs) can bind, can stop transport or hijack the carrier
45
Active Transport
Substances move against the concentration gradient (Requires energy, ATP)
Moving from where a substance is low to where a substances is high
Uses membrane carriers, it is specifc, saturates, and can be inhibited.
46
Sodium Potassium ATPase Pump
Active Transport
Sodium out, where it is high
Potassium in , where it is low
Maintains concentration gradient across the membrane
ATPase enzyme breaks down ATP to allow conformational change
47
Local Communication
Cells talk to themselves or nearby cells
48
Autocrine Communication
Cells talk to themselves
Cells release messenger to bind a receptor on plasma membrane
Triggers a cellular response
49
Paracrine communication
Chemical signal sent to nearby cells
Nearby cells will respond after picking up the message
Cells can communicate locally both chemically and physically
50
Gap Junctions
Tunnels called gap junctions
Creates a passage for small molecules
Quick wya for cells to communicate
Direct transfer of molecules through tunnels/bridges
2 membrane proteins interlock -> form connections called connexons
51
Osmosis
Movement of water down its concentration gradient
High solute concentration = low water concentration
Water crosses through channels called aquaporins
Channel mediated diffusion
52
Factors affecting osmosis
Permeability of membrane (Whether channels are present or not)
Concentration gradient of the solutes (higher concentration gradient = higher speed)
Osmotic pressure of the solution
53
Solues
What is dissolved in solution
54
Solvent
Water, what does the dissolving
55
Osmoles (Osm)
number of solute particles in a soluion
56
Osmolarity (Osm/L
number of osmoles in 1L of solution
57
High osmolarity
Lower the water concentration
58
Tonicity
Ability of a solution to cause osmosis across membranes
59
Isotonic
ECF has the same osmolarity as body fluids
60
Hypertonic
ECF has higher osmolarity than body fluids
Water leaves the cell
Causes shrivel
61
Hypotonic
ECF has lower osmolarity than body fluids
Water enter cell
Causing lyse/growth
62
Chemical & Electrical Gradient
Ions are influences by the charges around them (electrical driving froce)
Positivie ions attracted to a cell with negative charge (electrical gradient)
Ions move down their electrochemical gradient
Until reaching electrochemical equilibrium
63
Plasma membrane is permeable to potassium
Potassium is constantly leaking out of the cell
Causes the inside of the cell to have a negative charge
64
Chloride doesnt move in
Inside of a cell is negaive
Chloride is negative
It is repelled due to both having negative charge
65
Membrane Potential
Electrical poential of a cell membrane
Due to distribution of ions across membranes
66
Factors R-Membrane Potential
Permeability of membrane to various ions
Concenraion gradients of the ions
67
Sodium Potassium Pump
3 Sodiums ions out (Na+) and 2 Potassium ions in (-K+) cell
Maintians charge across the membrane
Preventing the leakage of poassium
Will maintain potassium inside the cell
68
Excitable cells
Rapidly change their membrane potential creates electrical signals
This electrical signal is an action potential
Action potential relies on ion channels called voltage-gated channels
69
The Neuron
Communication via propagation of an action potential
Release of neurotransmitters to carry the signal to the next neuron
The nervous system signals via electrical events within the neurons
70
Types of Ion channels
Mechanically Gated
Chemically Gated (Ligand-gated channels)
Voltage Gated
71
Mechanically Gated ion channel
Open gate due to deformation/stretch across the membrane
Changes shape of the membrane containing channel
Gate opens -> allowing flow of ions
72
Chemically Gated (Ligand-gated channels) ion channels
Respond to a chemical binding to he channel
Chemical binds-> gae opens-> ion flow
73
Voltage Gated ion channels
Respond to voltage change inside he cell
Volage change -> Gate open -> ion flow
74
Dendrites/Soma (Cell body)
input zone
Signals are combing to tell the neuron what is going on
Receiving signals in order for communication to take place
Electrical event called graded poential
75
Axon Hillock
Trigger zone
Decide whether signal gets passed onto the next cell
Threshold - if threshold is reached AP occurs
76
Axon
Conducting zone
Action potential travels here
77
Axon Terminal
Output zone
Signal gets passed onto the next neuron by releasing chemicals
78
Graded potential
Electrical response which varies in its magnitude/size
Dependant on the number of ion channels which open
Mechanical and Chemical channels are responsible for grade potentials
79
Average RMP for neurons
-70mv
80
Depolarization
Cell becomes more positive
Move towards threshold
Sodium coming into the cell
81
Repolarization
Cell returns to the RMP
Threshold -> mVolage change initaiting an action poential (-55mv)
82
Hyperpolarization
Membrane potential is more negative than RMP
Moves away from threshold
Potassium moving out
83
Graded potenial decay
Graded potentials don't travel all the way down the axon like action potentials
Signal loses strength, due to leakage of charge across the membrane, loss of depolarization
Strength of the initial simulus
84
Action Potentials
All or none - threshold reached or not reached
Require depolorization to reach threshold (-55mv)
Only travel in one direction down an axon
Trigger release of neurotransmitters pass signal
85
Sodium causes action potentials
During RMP
Permeability to potassium ions is greater than sodium
Potassium leakage
During action potential
Sodium channels open (voltage gated ion channels)
Increase membrane permeability to sodium
86
Sodium Voltage gated channel
Two gates -> activation & inactivation gate
Inactivation gate is closed
Another action potential cannot fire in the same neuron
Absolute refractory period
Allows for undirectional travel/flow
87
Potassium Voltage Gated Channel
Only one gate -> activation gate
Slower to open/close than sodium voltage gated channel
Potassium leaving is what causes repolarization and hyperpolarization
88
Propagation of action poential
Action potential traveling down a neuron
Depolarize the axon until it reaches the axon terminal
89
Steps for Propagation
(1) Depolarizing Graded Potential
Movement of sodium
Caused by Mechanical/Chemical sodium gated channels
(2) Sodium rushes into axon hillock
Causes at least a +15mv change (from -70mv to -55mv)
Reaches threshold causing action potential
(3) Sodium travel to regions with resting membrane potential
Causing the next area of the axon to begin depolarization
Moving of sodium causes depolarization of the next sodium voltage gated channels
90
Action potentials uniderectional
Previous parts of the axon are in repolarization
INactivation gate is closed
Channel can ever open again until it is in RMP
This is called the absolute refractory period
Action potetials happen sequentially
Previous channel will always be in absolute refractory
91
Speed of action potential propagation
1. Resistance of the axon membrane to ion leakage (myelination)
Inceased ion leakage -> Slower action potential
2. Diameter of axon
Large dimater -> Faster conduction
92
Saltatory conduction
Myelin sheath acts like an insulation around axons
Spaces between each cell are the Nodes of Ranvier
Nodes of ranvier contain Sodium & Potassium volage channels
Depolarization only happens at Nodes of Ranvier
Rather than he whole axon
Propagation is faster with myelin
Action potentials are said to leap from node to node
93
Multiple Sclerosis (MS)
Central nervous system disorder
Damage to he myelin sheath
Disrupts he conduction of action potentials along axons
Autoimmune atack which attacks myelin causing damage
94
Chemical synapse
Location of chemical synapse
Axon terminal
Dendrites
Cell body
95
Presynaptic & Postsynaptic Neurons
Synpase
Axon terminal of the presynaptic cell
Plasma membrane of the postsynaptic cell
96
Presynaptic & Postsynaptic Neurons
Axon terminals
Axon terminals depolarization triggers
Calcium to enter the axon terminal through calcium voltage gated
This causes the release of neurotransmitters from synaptic vesicles
97
Presynaptic & Possynaptic Neurons
Neurotransmitters
Neurotransmitters cross the synaptic cleft
Transmit information to the postsynaptic cell by opening chemically-gated channels
Neurotransmitters are returned to axon terminals for recycling
Enzymes in synapse inactive neuroransmitters
Neurotransmiters diffuse out of the synaptic cleft
98
Events at postsynaptic neuron
Neurotransmitter bind receptors on the dendrites/soma of the postsynaptic neuron
Causes a graded potential, referred to as the post-synaptic potential
If there is depolarization of the postsynaptic neuron
Excitatory postsynaptic potential (More Sodium in)
If there is a hyperpolarization of the postsynaptic neuron
Inhibitory postsynaptic potential (More Potassium out, Or Chloride in)
Graded potentials are small
Single postsynaptic potential will not be enough to cause threshold
99
Principle of summation
EPSPS and IPSPS can happen simultaneously in a neuron
Decay happens as they travel towards the axon hillock
Graded potentials sum together at the axon hillock
Maybe threshold is reached maybe not
100
Central Nervous Sysem
Brian and spinal cord
Inegrative control centre
101
Peripheral Nervous System
Peripheral nerves (cranial and spinal)
Communication beween CNS and body
102
Sensory (Afferent) Division
Composed of sensory neurons
Conducts signals from receptors to CNS
103
Motor (Efferent) Division
Composed of motor neurons
Conducts signals from CNS to effectors
104
Autonomic Nervous System
Controls Involuntary responses
105
Somatic Nervous System
Controls voluntary movement
106
Sympathetic Division
Mobilises body systems
Flight or fight responses
107
Parasympathetic Division
Conserves energy
Rest and digest responses
108
Sensory Receptors
Photoreceptors
Mechanoreceptors
Chemoreceptors
Chemoreceptors
Nociceptors
Thermoreceptors
Osmoreceptors
109
Photoreceptors
Wavelengths in the visible receptrum
110
Mechanoreceptors
Mechanical energy (Stretch/deform/bending)
111
Chemoreceptors
Chemical sensitive
112
Nociceptors
Pain receptors, tissue damage
Free nerve endings that detect painful stimuli
113
Thermoreceptors
Heat & Cold
114
Osmoreceptors
Soluble concentration of osmotic activity
115
Classes of sensory receptors
Complex neural receptors
Special senses receptors
116
Complex neural receptors
Receptor is part of the neuron
Specialized nerve ending
Myelinated axon
Cell body
Responsible for olfaction somatic senses
117
Special senses receptors
Specialized receptor
Synapse
Myelinated axon
Cell body
118
Complex neural receptors
1. stimulus
2. alteration of receptor membrane (sodium channels open)
3. Local current flow within receptor (Receptor potential - graded potential)
4. Graded potentials change frequency of action potentials
5. Action potential propagation to the CNS
119
Special senses Receptors
Application of stimulus
Alteration of receptor membrane (sodium channels change)
Local current flow within receptor (Receptor potential- graded potential)
Release of neurotransmitter
Change in post-synaptic membrane potential
Change in frequency of action potentials
Action potentials propagate to CNS
120
Action potentials vs receptor potentials
Action potential -> all or none, once initiated will flow down axon
Receptor potentials -> graded, differ in amplitude & dissipate
121
Receptive field
Stimulus is stronger
The receptor potential is longer
Frequency of action potentials is higher
stronger release in neurotransmitter
A strong stimulus will excite more receptors
122
Sense of Smell
Complex neural receptors
Primary sensory neurons in the olfactory epithelium
Synapse with secondary neurons in the olfactory bulb
123
How do we perceive different smells?
We have 350 odor receptors
Combination of signals coming from neurons
Creates the perception of different smells
124
Taste
Combination of 5 sensations; sweet, sour, salty, bitter, and umami
2000-5000 taste buds
Each of these taste buds contain 50-150 taste cells
Taste cell is non-neural epithelial cell
Taste cells are special senses receptors
125
Sensory Physiology Structures
126
Cortical Anatomy/function of each lobe
127
Somatic senses
Touch
Proprioception -> Awareness of body movement and location in space
Temperature
Nociceptors (pain)
128
Similarities B/W somatic senses
All receptors are neurons
Receptors are located at skin and viscera
Secondary neurons are in the spinal cord
Medulla synapse onto tertiary neurons in he thalamus
Information is sent to the somatosensory cortex
129
Somatic sensory receptors are mechanoreceptors
Sensitive to physical distortion of skin
130
Types of mechanoreceptors
Pacinian corpuscles
Meissner's corpuscles
Merkel's disks
Ruffini's endings
131
Pacinian corpuscles
Deep
Sense of vibration of skin
132
Meissner's corpuscles
Superficial
Responds to fluter & stroking movements
133
Merkel's disks
Superficial
Responds to steady pressure & texture
134
Ruffini's endings
Deep
Responds to skins stretching
135
How do mechanoreceptors differ
Adaption rate (Becoming used to the presence of a receptor)
Pacinian and Meissner's corpuscies are rapidly adapting
Merkel's disks and Rufinis endings are slowly adapting
Receptive field size
Size- merkel (touch) and meisner (touch)
Ruffini's (stretch) and Pacinian (vibration)
136
Tactical Acuity
Two point discrimination
Smallest seperation beween two points on the skin that is perceived as two points rather than one
Regions with high tactile acuity have small receptive fields
137
Sensory Pathways for somatic senses
The somatosensory cortex is located in the parietal lobe
Sitmuli from the left side is going to the right side of the brain
138
Spinal cord
Segments of the spinal cord receive sensory input from specific regions
Dermatome -> Area of the spinal cord that receives sensory information from an area of the skin
Dorsal root -- sensory
Ventral root -- motor
139
Primary Somatosensory Cortex
Primary motor cortex is located on the precentral gyrus
Proximity allows for sensory information to quickly trigger motor actions
140
Somatosensory Cortex somatotopy
Each body part is represented in a specific area of the somatosensory cortex
Amount of space on the somatosensory cortex devoted to each part is proportional to the snesitivity of that part
The larger the sensitivity the more space in the somatosensory cortex
141
Temperature
Sensed by free nerve endings in the epidermis
Thermoreceptors in the brain (cruicial for homeostasis)
There are both warm and cold receptors
They present slow adaption between 20-40 degrees C but they don't adapt outside this range
142
Pain
Sensory and emotional experience
Actual or poential tissue damage
Nociceptors are free nerve endings that detect painful stimuli
143
Pain Fibers
Ab (beta)
Respond to mechanical stimuli (touch)
Large & myelinated
Ad (Delta)
Respond to intense mechanical or mechano thermal stimuli, fast pain
Small & myelinated
C
Respond to heat, cold, slow pain
Small & unmyleninated
Thermoreceptors and Noiceceptors
Nociceptors have a higher threshold than thermoreceptors
144
Vision
Involves about half of our cerebral cortex
Light is an electromagnetic energy emitted in the form of waves
145
Wavelengths
Extremely short wavelengths -> Gamma rays
Long wavelengths -> Radio waves
Visible light -> 400-700nm
146
Pupil
Hole in the center
147
Iris
The colour of you reye, regulates size of pupil
148
Cornea
Clear sheet in front of pupil and iris
149
Sclera
The white of your eye (majority of eyeball)
150
Conjunctiva
Inside of eyelid
151
Extraocular eye muscles
Moves eye
152
Optic nerves
Carries signal to brain
153
Fundas
Rear region of eye
Central retinal artery & vein
154
Optik disk
Where optic nerve exits the retina (blindspot)
155
Macula
Center of visual field
156
Fovea
Center of macula (highest spatial resolution
157
Retinal processing
(1) Light first makes way through
Axons of optic nerve, ganglion cells, amacrine cells, bipolar cells, horizontal cells, gets reflected than activates photoreceptors
(2) Photoreceptors project to bipolar cells (depolarized)
Release neurotransmitter
Initiate action potentials on the ganglion cell
(3) Photoreceptors and bipolar cells are graded potential
Whereas the ganglion cell where action potential occurs
The amacrine and Horizontal cells which help integrate visual signals through lateral interactions
158
Photoreceptors
Convert light energy into receptor potentials
159
Rods
Highly sensitive to light
Responsible for vision at low light levels
160
Cones
Less sensitive to light
Three types of cones
Respond to RBG wavelengths
161
Light Transudction in the dark
Photoreceptors are leaky
Sodium & calcium to pass through channels in the plasms membrane
Depolarization of photoreceptors
Triggers neurotransmitter that inhibits activation of the bipolar cell
162
Light Transduction in the light
Closing of sodium and calcium channels
Hyperpolarization of rod and cone cell
Less neurotransmitter release
Lesser inhibition allowing the bipolar cell to depolarize
163
Light Transudction recovery phase
Sodium and clacium channels do not open immediately
Reduced release of neurotransmitter
This is why there is a lingering sensation of bright stimulus
164
Specialization of the fovea
Fovea is responsible for detailed vision, has the highest acuity
Photoreceptors in the fovea are exclusively cones
Cells overlying the fovea are pushed aside
Allowing light to strike the photoreceptors directly
Small receptive field, having much more sensation
165
Receptive fields of the retina
Peripheral portions of the retina have many photoreceptors
Converge on a ganglion cell (large receptive fields) (Amplifying effect) (large reception of light)
In fovea few photoreceptors converge on a ganglion cell, allowing for a smaller receptive field
166
Types of eye movements
Saccades
Smooth pursuit
Vestibulo-ocular reflex
Vergence
167
Saccades
Rapid
Jerky eye movements that quickly move the line of sight
To scan a face or read
168
Smooth pursuit
Smooth eye movements
Keep the image of a moving object of interest on the fovea
A flying bird
169
Vestibulo-ocular reflex
Stabilizes the eye during head movement
Uses sensory input from the semicircular canals
170
Vergence
Used when the object of interest is approaching or moving away
171
Retina Projects to visual cortex
Infomration from the left visual field is sent to the right visual cortex
Fibers from the nasal part of either eye cross over at the optic chiasm
fibers from the temporal portion of the right eye and the nasal portion of the left project to the lateral geniculate nucles on the right side
Synapse in the LGN visual signals continue to the primary visual cortex
172
Sound
Pressure wves generated by vibrating air molecules
Alternately compressed and released
173
Outer ear
Auricle (Pinna)
Auditory canal
Tympanic membrane
174
Auricle (pinna)
Moveable in some animals
Directs the sounds into the ear
175
Auditory canal
External auditory meatus
176
Middle Ear
Ossicles
Eustachain ube
177
Ossicles
Three small bones
Transfer the sound from an external environment to the inner ear
178
Tympanic membrane
Ear drum
Separates the external ear from them middle ear
179
Innear ear
Oval window
Cochlea
Vestibular apparatus
180
Ear canal
Funnels and conducts the sound to the middle ear
181
Eustachian tube
Connects the middle ear with the pharynx and helps equilibrituate the middle ear pressure
182
Oval and round window of ear
Separates the inner ear (filled with air) and the cochlea ( filled with fluid)
183
Cochlea
Structures that convert physical motion of the ears structures into a neuronal response
184
Vestibular apparatus
Responsible for our balance
185
Sound transudction
(1) Sound waves strike the tympanic membrane and become vibrations
Sound wave energy is transferred to three bones of the middle ear
Ossicles (bones) vibrate
(2) Ossicles attached to the membrane of the oval window
Vibrations of the oval window create fluid waves within the cochlea
(3) Cochlea --- Where sounds become action potentials
Fluid waves initiated at the oval window
Waves push on the flexible membrane of the cochlear duct
(4) Pressure from the wave releases at the round window
Mechanoreceptors within the cochlear duct transduce movement into action potentials on the auditory nerve
186
Strucures within the cochlea
The cochlea duct contains the organ of Corti
Organ of corti sits on the basilar membrane is covered by the tectorial membrane
These membranes are flexible tissues
Move in response to movment of perilymph inside the vestibular duct
Displacement of the basilar and tectorial membranes
Receptor potentials to occur in hair cells located in the organ of corti
Receptor potentials are created when the hair cells begin to bend
187
Hair cells
Basilar membrane vibrates the hair cells move back and forth
(1) Bending the biggest hair cell opens mechanically linked ion channels
Depolarizing the hair cell
Release of neurotransmitter increasing the action potential frequency on the afferent nerve
(2) Bending in the opposite direction hyperpolarizes the hair cell
Decreasing the release of a neurotransmitter
Fewer action potentials
188
How is frequency of sound mapped
Tonotopy
Fluid waves travel along the basilar membrane
189
Basilar membrane
Different part of the basilar membrane are different frequencies
narrow, thick base tuned for high frequencies
Middle portion responds to medium frequencies
Apex, resonds to the low frequencies
190
Coding of sound intensity
Increased rate of firing on a single nerve fiber
Multiple sets of neurons with different thresholds
Recruitment of additional neurons as loudness increases
191
Auditory pathway in the CNS
Ears -> Medulla (where nerves cross body midline) -> Midbrain (projections to cerebellum) -> Thalamus -> Auditory cortex
Different groups of neurons in the primary auditory cortex encode different frequencies of sound
192
Sound localization
Sound takes longer to reach one ear than the other -> Known as interaural timing differences
Timing differences can be very small, they are sensed by coincidence detectors in the brainstem
The sound is going to be louder due to an acoustic shadow produced by the head -> Interaural intensity differences
193
Types of hearing loss
Conductive
Sensorineural
Central
194
Conductive hearing loss
Sound is unable to be transmitted through th eouter or middle ear. A mechanical defect
Loud sounds rupture ossicle
Ear war
Infection fills middle ear with fluid
195
Sensorineural hearing loss
Damage to structure of inner ear that affects hair ells, or to auditory erve (nerve deafness). A transductile or peripheral defect
Loud sounds damage organ of corti
Oxtotoxic drugs damage hair cells
Presbycusis (old age hearing) degenerates cochlea
196
Central hearing loss
Damage to auditory pathways upstream from cochlea. A defect in the central nervous system
Tumours, stroke in the central auditory pathways
197
Motor unit
A single motor neuron innervates a large number of muscle fibers
Made of motor neuron + all muscle cells (fibers) that it innervates
198
Muscle Force
Force is increased by recruitment of more motor neurons and increased activity of motor neurons
Motor nuerons have phasic and tonic responses
199
Phasic
Bursting of action potentials when eye moves
200
Tonic
Sustained of action potentials sustains contraction
201
Muscle spindles
Alpha (a) motor neuron
Innervates extrafusal muscle fibers
Extrafusal fibers create the force
Extrafusal fibers are normal contractile fibers
Gamma (y) motor neurons
Innervate the intrafusal muscle fibers
Tonically active 1a afferent sensory neurons wrapped around intrafusal fibers (sense stretch of the intrafusal fibers) and send information the CNS
202
Contraction of intrafusal/extrafusal fibers
Gamma motor neurons fire, and contract the intrafusal fibers
Alpha motor neurons fire and contract the extrafusal fibers
203
Golgi Tendon Organ
Sensory receptors that send information the CNS about muscle tension mechanoreceptor
Sensory receptors are attached to 1b afferent sensory neurons
Links muscle and the tendon
Consists of sensory nerve endings interwoven among collagen fibers
Muscle passively stretched (someone pulls on your forearm)
Activity in muscle spindle increases
Activity in golgi tendon organ goes up
Muscle actively contracts
When extrafusal muscle fibers contract by activation of motor neurons,
Spindles unload and decrease their charge rate
Golgi tendon organ firing increases
204
Group 1a
Primary afferents
Supply all three types of intrafusal fibers
205
Group 1b
Afferent fibers
Branch extensively and wrap around the many collagen fibers that compose the golgi tendon organ
206
Alpha-gamma activation
When the muscle actively contracts
Alpha motor neurons fire
Extrafusal fibers contract, and the intrafusal fibers slack
Activity on the muscle spindles will decrease
If only alpha motor neurons were activated only extrafusal fibers contract
207
Alpha-gamma coactivation
Both extra and intrafusal fibers contract together
Tension maintained and muscle spindles can still signal changes in length
208
Stretch reflex
Load added to muscle = causes muscle to stretch
Muscle and muscle spindle stretch
Muscle spindle afferents to fire more frequently
Alpha motor neuron projects to the muscle
Increases activity towards muscle
Causing contraction and maintain arm position
209
Patellar tendon reflex/knee jerk reflex
Tapping the patellar tendon streches the quadriceps femoris
Muscle spindle in quadriceps femoris stretch
Activating 1a afferent to fire action potentials
1a afferent synapse on alpha motor neuron to quadriceps femoris
Muscle contracts and swings leg forward
Collateral 1a afferent excited an inhibitory interneuron in the spinal cord
Inhibitor interneuron inhibits alpha neuron to antagonistic muscle, relaxing it so the leg can swing and extend out
210
Organization of spinal cord
The medial parts of the spinal cord gray matter are involved in primary control of posture
The lateral pars are involved in the fine control of distal extremities
211
Primary motor cortex
Motor map shows the same disporoportions as somatotopic map in the primary somatosensory cortex of the postcentral gyrus
Musculature used in task requiring fine motor control, occupy a larger space in the primary motor cortex then musculature requiring less precise motor control
212
Corticospinal tract
Primary pathway that leaves the motor cortex to innervate motor neurons in the spinal cord
Left side of body is controlled by right motor cortex and right side conrolled by let motor cortex (mostly)
Axons cross over either the brainstem or spinal cord allowing for this to happen
213
Population coding in the motor cortex
Cortical motor neurons are directionally tuned
Individual motor neurons cannot precisely specify the direction of an arm because they are tune broadly
Movement direction can be decoded by a population of neurons
214
Brain Machine Interfaces
Resoration of motor functions for patients with spinal cord damage or patients with brainstern damage
Invasive BMI's record neural activity with implanted microelectrodes and use population decoding algorithms to control prosthetic devices, computers, or patients muscles
215
Motor cortex
Projects to motor neurons in the spinal cord which project to the muscle. This results in movement
Receives input from cortical association areas, the basal ganglia, and the cerebellum
216
Cerebellum
Sits underneath the cortex, on top the brain stem
Sees differences between an intended action and actual action
Gets input from the cerebral coftex, brainstem and spinal cord and sends projects back to them forming a bast loop
Modification of synapses in this loop is crucial for motor adaptation and learning
217
Cerebral deficits/lessons
Typical cerebellar diseases include dysmetria and decomposition of movements
218
Cerebellar disease symptoms
Wide gait, instability of trunk, irregular staggering steps
Results in lateral veering or falling if severe
Can also be seen with a severe loss of proprioception
219
Projections to the cerebellum
Cerebral cortex:Synapse in the pontine nuclei of the pons first, which project up into the cerebellum
Direct sensory input: Vestibular, muscle spindles, other mechanoreceptors
Other brain stem inputs:inferior olive and the locus coeruleus - send modulatory inputs for learning and memory
220
Output of the cerebellum
Cerebellar cortex projects to the deep cerebellar nuclei and onto the motor cortex (via the thalamus)
Cortical areas that project to the cerebellum, and the cerebellum projects back to them
221
Cerebellar circuit
There are two types of input circuits
Mossy fibers: synapse on granule cells, axons of granule cells form parallel fibers which synapse on purkinje cells
Climbing fibers: synapse directly on purkinje cells
mossy and climbing fibers excite purkinje cells
222
Purkinje cells
Provide output of the cerebellum through inhibitory synapses
One pukinje cell can receive input from over a million granule cells (convergence) but only one climbing fiber
223
Basal Ganglia
Regulating and planning movements
Receives input from the cortex and projects back to the cortex through the thalamus
Circuit influences brain stem outputs and ultimately neurons of the spinal cord ( Crucial role in planning movements)
224
Organization of the basal ganglia
4 interconnected nuclei found in the white matter fo the cerebrum
striatum
Golbus pallidus
Substantia nigra
Subthalamic nucleus
225
Inputs to the basal ganglia
Caudate nucleus and the putamen are the input nuclei of the basal ganglia
Almost all cortical areas project to the acaudate or putamen, except primary visual and auditory cortex (temporal and occipital lobe)
Caudate and the putamen receive dopaminergic input from the substantia nigra pars compacta in the midbrain (Increase or increase efficacy of other neurons)
226
Outputs of basal ganglia
Caudate and the putamen send output through the globus pallidus and the substantia nigra pars reticulata
The globus pallidus can be further subdivided into an external segment and internal segment for motor control
Output is sent on the superior colliculus (eye movement projection), subthalamic nucleus, the thalamus, and eventually back to the cerebral cortex
227
Activity in basal ganglia
Motor neuron cortex excites the putmen neuron
The putamen inhibits to the globus pallidus internal segment neuron (silencing its tonic discharge rate)
The globus pallidus internal segment enuron projects to the thalamus neuron and allows it to fire AP since its tonic inhibition is inhibited
Thalamus neuron projects to the motor cortex neuron
228
Indirect and direct pathways
Dopamine 1 receptors increase activity of putamen, but Dopamine 2 receptors inhibit the putamen
The direct pathway facilitates movements
The indirect pathway inhibits movements
Excitatory or inhibitory effect on motor cortex depends on the balance between the direct and indirect pathway
229
Parkinson's disease
Cells in the substantia nigra pars compacta die
Patients los dopaminergic neurons of the substantia nigra pars compacta
Deficits appear when the patient loses 80% of dopaminergic neurons
230
Parkinson's disease
Typical Symptoms
Tremor at rest
Slowness of movement
Rigidity of neck
Minimal face expression
231
Parkinson's disease
Motor Symptoms
Rigid gait
stooped forward
hypokinesia
Slow shuffling steps
Slow movement initiation
232
Process of Parkinsons
Cells of substantia nigra pars compacta die, less dopamine release
Less inhibition to putamen cells, meaning it is more actively inhibiting the Globus pallidus external segment
Because there is an increased inhibition from the Putamen to the globus pallidus external, we see a reduced inhibition of the globus pallidus internal segment
Globus pallidus external segment less efficiently inhibits the subthalamic nucleus, meaning there is an increased excitatory effect from the globus pallidus internal segment
This overall excitation of the globus pallidus internal segment from all directions, causes an increased inhibition of the Thalamus leading to a significantly decreased excitation to the motor cortex
233
Treatments of parkinsons
Basal Ganglia Structures that can be removed to help Parkinsons are; Either the globus pallidus internal segment or the subthalamic nucleus
234
Four functions of membrane proteins
Ion channels
Enzymes
Receptors
Membrane carriers
Structural Function
235
Chemical Gradients
Molecules tend to move from areas where they are in high concentration to areas where they are in low concentration. There they move down their concentration gradient
236
Electrical Gradients
Recall that many of the solutes in our body carry a change. Positively charged ions move towards negatively charged areas or down their concentration gradient
237
Two factors that affect the cell's membrane potential
The concentration gradients of different ions across the membrane
The permeability of the membrane to those ions
238
Graded potential properties
Occur in the soma or dendrites of a neuron
Can be depolarizing or hyperpolarizing
Can be the result of opening mechanically gated or chemically gated ion channels by a stimulus
Graded because the size of amplitude of the electrical event will be directly proportional to the stimulus strength (large stimulus = large graded potential)
239
Neurotransmitter is removed
Neurotransmitters are returned to axon terminals for recycling
Enzymes in he synapse inactivate neurotransmitters
Diffuse out of the synaptic cleft
240
Pituitary Gland
Pea size gland that has a crucial function essential for life
The site where several hormones are released which control reproduction, body fluid volume, metabolism, growth, adapting to stress, and a variety of other functions
241
Posterior Pituitary
Releases two peptide hormones, oxytocin and antidiuretic hormone. Produced by neurons inthe hypothalamus
242
Antidiuretic Hormone
Vasopressin, a hormone hat acts on the kidneys to conserve water and regulate our blood volume.
243
Anterior Pituitary
Release numerous hormones from endocrine cells found there in response to stimulation from hormones released by the hypothalamus
244
Thyroid Gland
Largest endocrine glands, butterfly shaped gland tha is located in the lower neck region, just below the larynx.
245
Hyperthryoidism
Producing too much thyroid hormone
246
Hypothyroidism
Deficiency in thyroid hormone
247
Adrenal gland
Two major regions to the adrenal gland, the outer adrenal cortex and the inner adrenal medulla.
248
Adrenal cortex
all hormones made by the adrenal cortex are steroid hormones
249
steroid hormones
Androgen, estrogens, progestins, mineralocorticoids, and glucocorticoids
250
Cortisol
Carabolic hormone, geneerally causing the breakdown of macromolecules, such as proteins, into their basic building blocks
251
Aldoserone
Mineralocorticoid because it affects the transportation of ions by the kidneys. The main stimulus for release is though a complex pathway of different proeins called he renin-angiotensin-aldosterone system
252
Adrenal Medulla
Releases a chemical mediator called epinephrine, as well as norepinephrine and dopamine.
253
Pancreas
Two major hormones, insulin and glucagon
254
Dermatome
Area of the skin that is mainly supplied by afferent nerve fibres from a single dorsal root of the spinal nerve
