1
Q
Divisons of the nervous system
A
CNS and PNS. Its goes back and forth between the two.
2
Q
Central Nervous System (CNS)
A
- Brain, spinal cord, (and retina)
- Control center where is processes all incoming info and decide what to do about it.
3
Q
Peripheral Nervous System (PNS)
A
- Everything else: cranial nerves,
spinal nerves - Talks to other tissues and systems
4
Q
Afferent
A
Information going in
5
Q
Afferent pathways of CNS and PNS
A
Information about outside world (pain, touch, etc) goes to PNS by sensory (somatic) receptors and nerves to CNS.
Information about inside the body (guts) goes to PNS by sensory (visceral) receptors and nerves to CNS.
6
Q
Efferent
A
Info going out of the CNS
7
Q
Efferent pathways of CNS and PNS
A
From CNS to PNS to the motor (somatic) nerves then to control the skeletal muscles.
From CNS to PNS to the motor (visceral or autonomic) nerves to control the sooth muscle, cardiac muscle, glands.
8
Q
Somatic system
A
Inputs we are consciously/voluntary aware of and activity that we control. Ie. information about outside the world and control of skeletal muscle.
9
Q
Autonomic system
A
We are unconscious/involuntary of it. It happens behind the scenes without us having to think about it.
10
Q
Anterior
A
Front of the body
11
Q
Posterior
A
Back of the body
12
Q
Superior
A
Top of the body
13
Q
Inferior
A
Bottom of the body
14
Q
Dorsal
A
Upper body and back. Top of brain. Or upper side of an aminal. Back of spinal cord.
15
Q
Ventral
A
relating to the front or lower side of the body. Or underside of an animal. Bottom of brain and front of spinal cord.
16
Q
Rostral
A
Front of brain and top of spinal cord. Head of animal
17
Q
Caudal
A
Back of brain and bottom of spinal cord. tail of an aminal.
18
Q
Cerebral cortex
A
Cognition (thinking), sensory perception, language, voluntary movement. High level thinking, very big in humans. Grey Matter
19
Q
Basal nuclei (basal ganglia)
A
Motor refinement, suppression of unwanted movements.
20
Q
What makes up the cerebrum
A
cerebral cortex and basal nuclei
21
Q
Thalamus
A
Relay station for sensory input. All sensory input must make a pit stop here.
22
Q
Hypothalamus
A
Homeostatic regulation (temp, food, etc), link to endocrine stuff
23
Q
What makes up the Diencephalon
A
Thalamus and hypothalamus
24
Q
Cerebellum
A
Balance, coordinated motor control
25
Brain stem
Control of cardio, respiratory, digestive; sleep cycle; balance and
posture. Things we don't think about.
26
Whats a frontal or coronal section
Cuts in half, not down the hemispheres.
27
Cerebrum
- Two hemispheres connected by the corpus callosum
- Each hemisphere divided into four lobes
- Folded structure allows increased area for cortex
Different areas of cerebral cortex have been associated
with perceptions/behaviours. This was discovered by doing scans od brain of awake subjects.
28
Groove
sulcus (plural sulci)
29
Ridge
gyrus (plural gyri)
30
Rats brains
Don't have grooves or ridges
31
fMRI scans of behaving subjects detect what?
local increases in blood oxygenation (indicator of neuronal activity). ie. reading and listening have different and similar parts.
32
Anatomy of a neuron: cell body
- Neuron somas (cell bodies) have all the usual things (nucleus, Golgi, ER)
- Most protein synthesis happens in the soma, and proteins are trafficked to their intended destination (like dendrites or axons)
- However: dendrites and axons can also have ER, Golgi outposts, etc, and some proteins are synthesized locally!
33
Communication between neurons
Chemical Synapes
34
Chemical synapes
Action potenial causes depolarization of presynaptic cell causes release of neurotransmitter. Post-synaptic cells detect the
neurotransmitter using receptor proteins. Which leads to various types of signalling or changes in memembrane potenial.
35
Anatomy of a neuron: Dendrite
Receive synaptic input (though synapses can form on somas and axons too) via neurotransmitter receptors.
- ligand-gated ion channels
- metabotropic receptors
Usually multiple branched dendrites (dendritic tree, or arbor)
- integrate input from multiple synapses.
36
Dendrites have what
Dendrite spines with spiny neurons. These dendrite spines are where excitatory synapes are.
37
Synaptic plasticity
spines are dynamic structures. the ability of synapses to strengthen or weaken over time in response to changes in their activity. Spines can get bigger or longer. Causes activity-dependent change in synaptic efficacy.
38
Activity-dependent change in synaptic efficacy
Can go in either direction
- Increased efficacy: long-term potentiation (LTP) (high activity)
- Decreased efficacy: long-term depression (LTD) (low activity)
Timescale: seconds to minutes
Associated with learning and memory
39
How can activity-dependent change in synaptic efficacy
Pre-synaptic side
1) Changes in number of release sites or release probability
Post-synaptic side
2) Movement of receptors into or out of synapse (change in number of receptors), change in receptor properties
Change in synapse number
3) Synapse formation or elimination. Which can be observed by changes in the number of dendritic spines.
40
Structral plasticity of dendritic secretory comparments during LTP-induced synaptogenesis
Have a recording electrode and two stimulating electrodes in the hippocampus. Stimulating electrodes to elict LTP by delivering bursts of rapid stimulation. After few mintues see small increase in activity which is very characteristic of LTP. Then took tissue from hippocampus and did serial elctron microscopy reconstrutions to see shape of dendrites and dendritic spines. The LTP sample had many more pines with synapes than the control sample.
41
Anatomy of a neuron: axon
Specialized for propagation of action potentials
- voltage-gated ion channels
Myelin sheath insulates axons, allowing increased conduction velocity.
Microtubules mediate long-distance trafficking.
42
Microtubule
Runs down the axon and is used for axonal transport.
43
Parts of axon
Axon hilihock, myelin, and nodes of raniver.
44
Examples of axonal transport motors (motor proteins that walk)
Kinesins and dyneins
45
Molecular motors in axonal transport
- protein complexes that walk on microtubules using energy from ATP hydrolysis.
- carry cargos such as vesicles, proteins, organelles.
Similar microtubule-based transport occurs in dendrites.
46
Kinesins
Walk anterograde (forward to terminal) to the the plus end.
47
Dynein
Walk retrograde (backwards to cell body) to the minus end.
48
Microtublues
Made of tubulin subunits.- Made of α and β subunits
- Polymerize and depolymerize from (+) end
- Polymerization depends on GTP coming in and GDP going out.
- Motors can be
(+) end directed (kinesin)
(-) end directed (dyneins)
They walk to either plus or minus end.
49
What way are axon microtublues oriented
The same way with the + end near the axon terminal.
50
Kinesin Stepping (symmetric walking)
Pi goes out and there is a substep of 4nm. Then foot bound to ADP lifts up and twist around to front. Then ATP binds to the other (back) foot. After ATP hydroloysis it becomes the ADP bound state and can left up and swing around. Look at pic.
51
the stepping of kinesin is dependent on what?
ATP hydrolysis
52
Neuronal axons contain what?
A different type of cytoskeletion structure made of actin and spectrine in a cool cage arrangment.
53
Whats the role of the cage structure
Perhaps structural stability, regulation of axon
diameter, organization of signaling proteins, ...??
54
Functional types of neurons
Sensory neurons, interneurons, motor neurons.
55
Sensory neurons
Inputs from sensory endings or receptor cells; outputs to other neurons. They have a pseudounipolar structure where cell body is in the middle. They sometimes have afferent endings or synapses with receptor cells.
56
interneurons
Connect two other neurons in the CNS. They are not myelinated.
57
Motor neurons
Inputs from other neurons; outputs to muscle. it's connected to a muscle cell.
58
fluorescence microscopy
Sample from tissue expressing fluorescent protein and/or labeled with fluorescence probes. Then imaged then channeled with different lasers or filter sets. Labeled pirkinji cells in cerebellum, DAPI which is labelling nuclei. Then merge these images together.
59
Purkinje cells
- Located in cerebellar cortex, involved in movement.
- Each purkinje cell receives input at 150,000 – 200,000
synapses (a lot!). Because they have huge dendritic harbour and they interget lots of info.
60
Retinal bipolar cells
- Receive inputs from photoreceptors (rods and cones).
- Each bipolar cell gets synaptic inputs from ~1-35 photoreceptors.
61
Pyramidal cells
- Most abundant excitatory neurons in cerebral cortex, hippocampus.
- Two sets of dendrites, a long axon (not shown). There is an upper and lower tree.
Called this because cell body shaped this way.
62
Motor neurons (axon terminals)
Areas where YFP (green) and AChR (red) overlap indicate neuromuscular junctions. Green was the axons is. Red is post synaptic acetychlonline receptors.
63
Where are neurons
grey and white matter
64
Grey matter
lots of cell bodies (neurons and glia) and dendrites (but also axons). Its the outside edges.
65
White matter
lots of axons – myelin is refractive to light (why its white). It's the insides.
66
Dense connectomic reconstrucion in layer 4 of the somatosensory cortex
Took piece of tissue from somatosensory cortex of mouse (grey matter) then did transmission electron microscopy of section then used it to reconstruct the volume. A few neurons have 90 cell bodies + dendrites have 34221 axons.
67
How many synapses?
Lots. Estimated that the human brain has:
~100 billion (1011) neurons
>100 trillion (1014) synapses
For comparison:
~1011 – 1012 stars in our galaxy
68
Nucleus (plural nuclei)
Group of neuron cell bodies with similar connections and functions, in the CNS. Not in atom of cell.
69
Ganglion (plural ganglia)
Groups of neuron cell bodies with similar connections and functions, in the PNS
70
Cortex (plural cortices)
Neurons organized in layers, like the cerebral cortex, in the CNS
71
Nerves
Bundles of axons.
72
Cranial nerves
- 12 pairs of cranial nerves
- Most arise from brain stem
- Contain sensory and/or motor fibers to organs/tissues in head and neck.
- Important for sight, hearing, taste, smell, touch, chewing, swallowing, etc.
Some are afferent (optic)
Some are efferent (trochlear)
Some are both (glossopharynqeal)
73
Spinal nerves
- 31 pairs of spinal nerves
- “On/Off ramps” to spinal cord
- Contain sensory + motor fibers connecting to organs and tissues throughout the body (two-way traffic).
Comes into and out of the spine between each vertebra.
74
Types of spinal nerves
Cervical nerves (8)
Thoracic nerves (12)
Lumbar nerves (5)
Sacral nerves (5)
75
Spinal cord
White matter is outside and grey matter is inside. Has dorsal roots, dorsal root ganglia, and ventral roots. Dorsal and ventral roots connect to make a spinal nerve.
76
Dorsal roots
sensory afferent axons. Where sensory input comes in.
77
Dorsal root ganglia
group of cell bodies of sensory afferent neurons.
78
Ventral roots
Motor efferent axon. Comes out.
79
Example of a neural circuit: myotatic spinal reflex
- Afferent input and efferent output talk to each other without involving the brain.
- Reciprocal innervation: simultaneous stimulation of nerve to one muscle and inhibition of nerve to the opposing muscle.
Muscle sensory receptor goes to afferent axon.Two heads. One connects directly connects to motor (efferent) axon which activates it then contracts the muscle. The other head is inhibition as it connects to interneuron then the motor axon to relax the flexor muscle.
80
Vertical pathways
Dorsal column medial lemniscus pathway and Spinothalamic pathway. Pathways cross over (“decussate”) in different places. Both go through the thalamus.
81
Dorsal column medial lemniscus pathway
For Proprioception, touch, then to spinal cord, then crosses over at the medulla. Then thalamus to cerebral cortex.
82
Spinothalamic pathway
For pain and temperature. Then to spinal cord where it across over, then thalamus and cerebral cortex.
83
Glial Cells
- Non-neuronal cells in the nervous system
- Physical and metabolic support
- ~90% of cells in the CNS are glia!
- Source of most brain tumors because they are still able to divide unlike neurons,
84
Types of glial cells
Oligodendrocytes, Schwann cells, microgila, ependymal cells, and astrocytes.
85
Oligodendrocytes
produce myelin sheath in CNS. Made of plasma membrane of digodendrocytes that rolls around the axons.
86
Schwann cells
produce myelin sheath in PNS.
87
Microgila
immune role – detect inflammation, phagocytose debris (like
macrophages).
88
ependymal cells
form the epithelium lining ventricles, secrete cerebrospinal fluid.
89
astrocytes
- Physically support neurons by creating kind of a matrix in the nervous system.
- Regulate ions (conc.) in interstitial fluid important for mainting ion potential and ability of cells make action potentials.
- Isolate synapses, take up neurotransmitters.
- Participate in synapse formation and pruning during development.
- Command capillary cells to form tight junctions (blood-brain barrier)
- Emerging roles in disease and injury.
90
Ventricles
Interconnected spaces filled with cerebrospinal fluid. They do plumbing. There is 4 of them.
91
Cerebrospinal fluid (CSF)
Fills the ventricles and subarachnoid space all around brain and spinal cord. Density of brain and CSF are similar, so brain is suspended (CSF acts as shock-absorber). Produced by ependymal cells in the ventricles. Composition is highly regulated, to protect CNS interstitial fluid. It's in the subarachnoid apace.
92
Blood-brain barrier (blood-CNS barrier)
It does both the brain and spinal cord. CNS depends on blood supply for oxygen and glucose (brain damage after ~5 min oxygen deprivation). Blood-brain barrier protects interstitial fluid in brain and spinal cord from stuff in the blood. Lipid-soluble substances can get through: O2, CO2, alcohol, steroid hormones. Water can get through via aquaporin channels. Everything else depends on selective membrane transport.
93
Blood-brain barrier is mediated by what?
1. Tight junctions (physical) between endothelial cells in capillary walls (help from astrocytes).
2. Tight regulation of membrane transport across endothelial cells.
