Neurophysiology Flashcards
(110 cards)
1
Q
what is neurophysiology?
A
the functions of the nervous system
2
Q
what are the functions of the nervous system?
A
- control movement and some functions (motor neurons)
- detect external stimuli (sensory neurons)
- integration of neural activity and connections (association neurons)
3
Q
what cells make up the nervous system?
A
neurons and supporting cells
4
Q
what are neurons
A
basic functional and structural unit of the nervous system
5
Q
what do supporting cells do?
A
aid the functions of neurons, about 5x more abundant
6
Q
association neurons
A
responsible for behaviour, thoughts and emotions in the CNS
7
Q
what are the 3 main regions in neurons
A
- axon
- cell body
- dendrites
8
Q
what do neurons do?
A
- conduct electrochemical impulses (action potentials)
- release chemical regulators (neurotransmitters)
9
Q
what does the cell body of neurons do
A
- the “nutritional center” of the neuron, where macronutrients are produced
- in the CNS frequently clustered to nuclei
- in the PNS occur in clusters called ganglia
10
Q
what do dendrites do in neurons?
A
- thin branched processes that receive information from sensory receptors (or from other cells) and send it to the cell body
11
Q
what do axons do in neurons?
A
- delivers electrical signals from the cell body to another neuron or an effector organ (muscle or gland)
- conduct impulses called action potentials
12
Q
what are afferent neurons
A
- aka sensory neurons
- conduct impulses FROM sensory receptors into the CNS
13
Q
what are efferent neurons
A
- aka motor neurons
- conduct impulses OUT OF the CNS to effector organs (like muscles or glands)
14
Q
what are inter neurons
A
- aka association neurons
- located entirely within the CNS, serve the integrative and associative functions of the nervous system
15
Q
what are the 2 types of motor neurons?
A
somatic and autonomic neurons
16
Q
somatic motor neurons
A
responsible for reflex and voluntary control of skeletal muscle
- have cell bodies in the CNS and send axons to skeletal muscles
17
Q
autonomic motor neurons
A
involuntary control of smooth muscle cardiac muscle and glands outside the CNS
- involves 2 neurons in the efferent pathway: 1. cell body in the CNS (which synapses with the second neuron), 2. post ganglionic neuron (whose axon extends to the effector organ and its synapse targets the tissue)
18
Q
2 divisions of autonomic neurons
A
sympathetic and parasympathetic
19
Q
sympathetic neurons
A
controls the body’s “fight or flight” response
20
Q
parasympathetic neurons
A
controls the bodies “rest and digest” functions
21
Q
simple neural circuit
A
- stimulus reaches receptor connected to sensory neuron
- sensory neuron send info integration center of the association neuron
- after integration info is sent through the motor neuron
- motor neuron reaches the effector and generates a response
22
Q
4 structural classifications of neurons
A
- pseudopolar: single, short process that branches like a T to form a pair of longer processes
- bipolar: 2 processes, one at either end, retinal and cochlear neurons
- multipolar: have several dendrites and one axon extending from the cell body - motor neurons
- anaxonic: have no obvious axon, some CNS neurons
23
Q
what is a nerve
A
- a bundle of axons located outside the CNS, most are comprised of both sensory and motor fibres
- some cranial nerves only contain sensory fibres - the ones that serve sight, hearing, taste and smell
24
Q
supporting cells in the PNS
A
- Schwan cells: form myelin sheaths around peripheral axons
- Ganglionic (satellite) cells: support neuron cell bodies within the ganglia
25
supporting cells in the CNS
1. Oligodendrocytes: form myelin sheaths around CNS axons
2. microglia: migrate through the CNS and phagocytose foreign and degenerated material
3. astrocytes: help to regulate the external environment of neurons in the CNS
4. ependymal cells: line the ventricles (cavities) of the brain and the central canal of the spinal chord
26
What is the difference between supporting cells in the CNS and PNS
In CNS: one oligodendrocyte forms myelin sheaths around several axons
In PNS: successive wrapping of schwan cell membrane around one axon, most of the schwan cell cytoplasm is left outside the myelin
27
What are astrocytes
- the most abundant glial cell in the CNS (up to 90% of nervous tissue in the brain)
- processes terminate in "end feet" at capillaries and others on neurons, therefore can influence interactions between neurons and the blood
- have other extensions adjacent to synapses between the axon terminal of one neuron and the cell body of another
28
7 functions of astrocytes
1. take up K+ form extracellular fluid
2. take up neurotransmitters released from the axon terminals of neurons
3. the "end-feet" surrounding blood capillaries take up glucose from the blood
4. formation of synapses in the CNS
5. regulate neurogenesis in the adult brain
6. induce the formation of the BBB
7. release transmitter chemicals that can stimulate or inhibit neurons
29
why do astrocytes take up K+
- K+ diffuses out of neurons during the production of nerve impulses and ends up in the extracellular fluid
- the take-up of K+ helps maintain proper ionic environment for neurons
30
astrocytes taking up neurotransmitters (glutamine example)
- astrocytes can take up th eneurotransmitter glutamate and transform it to glutamine which can be released back into neurons
- the neurons can then reform glutamate to fire again
31
why do the "end-feet" of astrocytes surrounding the blood capillaries take up glucose from the blood
- astrocytes metabolize glucose to lactate and then release it as an energy source by neurons, which metabolize it aerobically into CO2 and H2O for the production of ATP
- PET scans and fMRIs visualize brain locations by their metabolic activities and are based on the functions of astrocytes as well as neurons
32
what is the purpose of blood brain barrier
to impose strict control over what can move from blood plasma to the brain
33
why can some substances not pass the blood-brain barrier
- they are too highly charged
- too large
- not lipid soluble
34
what can move through the blood brain barrier
- non-polar CO2 and O2
- organic molecules like alcohol and barbituaries
35
how do endothelial cells of brain capillaries contribute to the BBB
- endothelial cells are joined by tight junctions and there are no pores between adjacent cells so the brain cannot obtain molecules from blood plasma by a nonspecific filtering process
-
36
what components of the BBB do astrocytes influence
- the tight junctions between endothelial cells
- the production of carrier proteins and ion channels
- the enzymes that destroy potential toxic molecules
37
how do CNS depressants directly affect brain cells
- affect areas that inhibit behaviours, alter speech, slow reaction time and foggy memory
- reactions depend some part on dose, size, weight, gender, genetics, etc.
38
fetal alcohol syndrome
- when mother drinks alcohol while pregnant may result in baby having small eye openings, smooth philtrum and thin upper lip
39
how do astrocytes affect the BBB
- secrete neurotrophins and in turn the endothelial cells appear to secrete regulators that promote the growth and differentiation of astrocytes
40
Nicotine and the BBB
- in < 10 seconds nicotine molecules cross the BBB and fit like keys into locks activated by acetylcholine neurotransmitters and increase the level of several other neurotransmitters (e.g dopamine)
41
tobacco and the BBB
- decreases MAO activity which is the enzyme needed to break down neurotransmitters
42
what problem arises with prescribed drugs and the BBB
- drugs we need to treat neurodegenerative disorders can't pass through the BBB but some infections can pass through
43
Rabies and the BBB
- rabies is a deadly viral infection which can penetrate the BBB
- there is no treatment after symptoms appear, but before they do rapid treatment with anti-rabies antibodies help attenuate the infection
- immune cells and antibodies cannot enter the brain therefore antibodies replicate out of control
44
what does dualinnervative mean
when an organ receives info from both sympathetic and parasympathetic systems
45
what organs do not have dualinnervation and how is regulation achieved in them?
- the adrenal medual, arrector pili muscles in skin, sweat glands in the skin and most blood vessels
- regulation is achieved by increases or decreases in tone (firing rate) of sympathetic fibres
46
2 neurons in autonomic motor control
Preganglionic: set of nerve fibres that connect the CNS to the ganglia
Postganglionic: set of nerve fibres that connect the ganglion to the effector organ
47
how are autonomic nerves classified?
- based on the primary neurotransmitters released across the synapses
cholinergic neurons: release acetylcholine (ACh)
adrenergic neurons: release norepinephrine (NE or E)
48
Acetylcholine and autonomic outflow
- ACh ic the neurotransmitter for all preganglionic fibres (both sympathetic and parasympathetic)
- transition is cholinergic
- ACh is the transmitter released by most parasympathetic post ganglionic fibres at their synapses with effector cells
49
Norepinephrine and autonomic outflow
- NE is the neurotransmitter released by most sympathetic nerve fibres at the postganglionic axon
- transmission is adrenergic
50
synesthesia
2 or more senses are connected
- Mozart: heard music as colours
- Alexander Yee and Shiger Kondo: reached 10 trillion decimal places of pi, each of the first 4 million digits was assigned a different colour and turned that into a song
- Daniel Tammet: ability to see numbers as colours, textures and sounds, and used this to memorize 22514 digits of pi
51
what can ANS dysfunction effect
heartrate, blood pressure, digestive tract peristalsis, sweating
52
ANS dysfunction through lyme disease
- when a tick carrying the parasite bites you, substances in its saliva disrupt the local immune response, spirochetes multiply in the skin
-immune response causes lessons, but neutrophils fail to appear
- bacteria spread via the bloodstream to joints, heart, nervous system and distant skin sites
53
what is the fluid mosaic model of the cell membrane
a constantly changing arrangement of the membrane that includes added cholesterol, carbs and protein to the lipid bilayer
54
passive transport
a process that does not consume energy - simple diffusion
55
4 types of simple diffusion
1. small uncharged molecules (lipid soluble) can diffuse through the lipid bilayer (e.g. steroid hormones)
2. small charged molecules (ions) can diffuse through water-filled pores)
3. leaky Ion channels: ions flow in or out as needed
4. voltage-gated ion channels: can only be opened or closed by gates
56
active transport
move substances in and out of cells against gradients
- consume energy
57
why are ion channels important for the nervous system
they help produce electrical impulses that transmit information rapidly
58
active transport of Na+ and K+
- establishes an electrochemical gradient that mediates how nerves fire
- ATPase moves Na+ out of the cell and K+ into the cell
59
what is resting membrane potential?
a potential difference (voltage) across the membrane that all cells have
- the inside of the cell is usually negative compared to the outside (in neurons its -70mV)
60
why are voltage-gated ion channels important for electrical activity in axons?
- when the channel opens it can change the membrane potential of the cell which is needed to conduct electrical signals in neurons
- channels are initially closed
- when they open ions move across the membrane (Na+ starts outside and K+ starts inside at the start of action potentials)
61
what are action potentials?
signals that go along the nerves from one place to another (the way neurons talk to each other)
- momentary discharges of resting membrane potentials caused by a rapid influx of Na+ due to opening of sodium ion channels
62
how do action potentials move along the nerve?
- AP starts at the axon helic and once initiated they move along the axon membrane towards the synapse
- voltage-gated ion channels reamplify signals since they have to go a long way and may weaken
- as the ions Na+ and K+ move across the membrane they change the charge across the axon
63
Ion gating in axons
a. channel is closed at resting memb. potential (nothing can get across)
b. gated channel opens as response to depolarization
c. gated channel closes (like a ball and chain), takes a while to close all the way so another mechanism keeps it closed until it can return to its original state
64
what is depolarization
cell undergoes a shift in electrical charge distribution resulting in a less negative charge inside the cell than outside
65
how does a cell repolarize after an action potential
- K+ will diffuse out of the cell making the inside less positive (until back to negative) restoring the original state of the resting membrane potential
66
Na+ and K+ pumps during action potentials
- pumps are constantly working
- pump out Na+ that entered the cell during the action potential
- pumps in the K+ that had left
- opening of the gates (pumps) is stimulated by depolarization
67
"all or none" response of an action potential
- the stimulus for the AP has to be strong enough to reach the threshold or it wont go at all
- if depolarization reaches the threshold , the maximum potential change is reached
- memb. potential starts at -70mV and reached +30mV
68
what does it mean to have a stronger action potential
stronger signals = fire more often (but not actually "stronger')
69
non-myelinated action potentials
- the AP moves smoothly along the axon
- all parts of the membrane are depolarized
- every patch of membrane contains Na+ and K+ channels therefore needs more energy to restore the membrane after transmition
70
myelinated action potentials
- the AP "jumps" between non-insulated nodes of Ranvier by saltatory conduction
- the myelin sheath provides insulation for the axon, prevents Na+ and K+ from moving through the membrane because there are no channels there
- The AP doesn't physically have to go over as many Na+ channels = moves faster
- needs less energy to restore the membrane after
71
purpose of the refractory period for action potentials
ensures the AP goes down the axon in one direction
72
what can increase the speed of action potential conduction
- increase diameter of the axon (reduces resistance)
- myelination (saltatory conduction)
73
what is the synapse
the functional connection between a neuron and a second cell (tiny space)
74
what happens when the action potential reached the end of an axon
- the AP reaches the synapse between the axon of the presynaptic neuron and meets the dentrites of another cell which stimulates it
75
what happens at the ends of presynaptic neurons
- the endings release neurotransmitters that stimulate APs in the postsynaptic cells
- the presynaptic neuron ends in a terminal bouton and is separated from the post synaptic by a tiny cleft
76
how do neurotransmitters get into the synaptic cleft?
1. action potentials reach axon terminals
2. voltage-gated Ca2+ channels open
3. Ca2+ binds to sensor proteins in the cytoplasm
4. Ca2+ protein complex stimulates fusion and exocytosis of the neurotransmitter into the synaptic cleft
77
how does an action potential get to the post synaptic neuron from the synapse
1. chemically gated channels are opened at the dendrites and cell bodies
2. there is an inward diffusion of Na+ which causes excitatory postsynaptic potential
3. signal is localized, incremental conduction of EPSP
4. at the axon hilic, voltage-gated Na+ and then K+ channels open
5. at the axon the action potential gets conducted
78
What is ESPS
Excitatory postsynaptic potential - depolarization in the postsynaptic neuron
79
what is myotonia?
a neuromuscular disorder where skeletal muscles have delayed relaxation after voluntary contraction or chemical stimulation
- can be caused by mutation in muscle Cl- channel
- if channel gates do not open properly repolarization is delayed, several APs fire instead of just one (until everything catches up)
80
myotonia in goats
- when startled / excited it causes a temporary stiffening of muscles
- when muscles relax after a few seconds the goat jumps back up
- poor climbers, easy to tame
-high meat-to-bone ratio (3:1 instead of 2:1)
81
what does Grey matter consist of?
- neuron cell bodies and dendrites
- found in the cortex (surface layer) of the brain
- also found deeper in the brain in agressions known as nuclei
82
what does white matter consist of?
- axon tracks
- myelin sheaths produce the white colour
- underlie the cortex and surround the nuclei
83
Meninges of the brain
Scalp, skull, Dura matter, arachnoid matter, Pia mater
- from inner layer to outer layer spells "PADS"
84
how does the pia mater connect to the brain and spinal chord
- the innermost membrane, clings to the surface and follows every fold
85
2 fluid cusions that protect the brain against head trauma
superior sagittal sinus (SSS): the outer cavity, sits under dura matter
subarachnoid space (SAS): the inner cavity, space in between the arachnoid and the pia matter
86
what is CSF tap
- taking a sample of CSF to examine signs of disease
- e.g. bacteria, viruses, inflammatory cells are abnormal products of degeneration as in multiple sclerosis
87
How many pairs of nerves are there in the CNS
43 pairs
- 31 are spinal nerves
- 12 are cranial nerves
88
what is a mixed nerve
- composed of sensory and motor fibres packed together
- every nerve in the CNS is a mixed nerve
- the sensory and motor fibres separate near the attachment of the nerve to the spinal chord
89
the spinal cord and the PNS
- the spinal cord extends from the brain stem to the pelvic region and ends before the end of the vertebral column
- nerves enter or leave the spinal cord in between the vertebrae
- interneurons communicate with one another along the length of the spinal cord
- an afferent sensory stimulus can be translated up to down the spinal cord by interneurons
90
how do reflexes show a link between the PNS and the spinal cord
- the "simple" withdrawl reflex response to a painful stimulus involves the contraction of several muscles, the relaxation of other muscles and responses that are initiated in the brain
91
Upper (UMN) vs lower motor neuron (LMN) damage in myotatic (stretch) reflexes - e.g. knee-jerk reflex
with LMN damage reflex is diminished
- not able to send back messages properly
with UMN damage reflex is exaggerated (or normal)
- loss of inhibitory inputs
- things regulating from higher up no longer send messages down
92
how does formation of the brain start?
- the "basic plan" is established by week 3
- by week 4 3 distinct swellings are evident at the anterior end: the prosencephalon (forebrain), mesencephalon (midbrain) and rhombencephalon (hindbrain)
- by week 5 the forebrain divides into the telencephalon and diencephalon, the hind brain divides into the metencephalon and the myelencephalon
93
what is the cerebrum
the largest pert of the brain which performs the "higher functions", divided into 2 hemispheres and has 5 regions
94
5 regions of the cerebrum and what they do
1. frontal lobe: motor control
2. occipital lobe: vision and coordination of eye movements
3. parietal lobe: perception of somaesthetic sensation (sensation arising from cutaneous, muscle, tendon, and joint receptors)
4. temporal lobe: interpretation and association of auditory and visual information
5. the insula: implicated in encoding integration of sensory information with visceral responses, receives auditory and somatosensory (mainly pain) information
95
what is the corpus callosum
connects the 2 hemispheres of the brain and ensures both sides can communicate with each other
- has been surgically cut in some people with epilepsy to alleviate symptoms
- each hemisphere is good at certain tasks and poor at others
96
Kim peak and christopher langan
Kim: had no corpus callosum
- known for remembering every page that he reads
Christopher: smartest person in the world but did not do anything extraordinary
97
damage to the left vs right half of cerebrum
Damage to left: difficulty with spacial concepts (like maps)
Damage to right: severe speech problems, though may leave the ability to sing unaffected
- applicable for ~ 97% of people (all right-handers ~ 90% of people, and ~ 70% of left-handers)
98
what is the cerebral cortex
- the outer layer of the cerebrum - a sheet of grey matter tissue, especially important in emotion and memory
- people with damage to the orbitofrontal area of the prefrontal cortex experience severe impulse behaviour
99
phineas gage
metal rod went through his left eye and brain, he survives but the damage to his cerebral cortex severely changed his personality
100
what is the thalamus
relay center through which all sensory information (except smell) passes on the way to the cerebrum
- promotes alertness
- causes arousal from sleep in response to any sufficiently strong sensory stimulus
- 4/5ths of the diencephalon
101
what is the epithalamus
the dorsal segment which contains the pineal gland which secretes melatonin
- melatonin helps regulate circadian rhythms
102
what is the hypothalamus
the bodies smart control coordinating center
- sits above the optic chiasm
- it is the most inferior portion of the diencephalon
- sight of the master circadian clock - SCN
- regulates daily bodily processes like hunger, thirst, regulation of body temp, etc.
- hormone secretion from the pituitary gland
- contributes to regulation of sleep and wake
103
function of the midbrain and hindbrain
contains many relay centers for sensory and motor pathways and are important in control of skeletal movements
104
2 systems of dopaminergic releasing nerves of the midbrain
1. nigrostriatal dopamine system
- involved in motor control
- Parkinsons disease is caused by degeneration of dopaminergic neurons in the substantial nigra
2. Mesolimbic dopamine system
- involved in emotional reward
- alcohol, amphetamines, cocain, marijuana and morphine promote activity
- may play a role in addiction (e.g. nicotine and other drugs
105
Schizophrenia
- may be caused by overactivity of the mesolimbic dopamine system
- early adulthood onset in 40% of men and 25% of women
- may experience hallucinations, disorganized thinking and speech, loss of motivation, impaired judgement, paranoia, etc.
106
what is the cerebellum
- the second largest structure of the brain, >50 billion neurons, contains grey and white matter
- monitors and refines motor activity initiated elsewhere
- receives input from proprioceptors (joint tendon, muscle receptors) and together with signals from the motor areas of the cerebral cortex helps with coordination of movement
107
what is the medulla
- all ascending and descending fibre tracts providing communication between the spinal chord and brain must pass the medulla
- required for regulation of breathing, CV responses (vital centers)
108
Asperger syndrome and PDD
Aspergers: hyperfocus, mild movement disorder, lack of social cues
Pervasive developmental disorder: some range of the same things
109
Autism and the brain
- affects speech and motor skills
- we concentrate on a single specific thing because we cant attend to all the info being received through our senses at the same time
Courchesne theory of overstimulation: autism children seem antisocial because they shun external stimuli, since their cerebellum cannot take it
110
what parts of the brain form from the prosencephalon, mesencephalon and rhombencephalon
Procephalon: cerebral hemisphere, thalamus, hypothalamus
mesencephalon: midbrain
rhombencephalon: pons, cerebellum, medulla oblongata
