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Structure of the Nervous System

76 important questions on Structure of the Nervous System

What is a horizontal plane section?

1 top half, 1 bottom half

Where does the dorsal root of the spinal cord send it's information?

Dorsal: Rug --> Towards the CNS
Dor(sal) je rug te breken = verlamming ezelsbruggetje

What is the function of the Somatic Peripheral Nervous System (sPNS)?

Voluntary control (muscle, skin, joints)
Contain motor neuron (AXONS ONLY)

Where do the cell bodies/dendrites/axons of motor neurons lie?

Cell bodies: CNS
Dendrites: CNS (not important)
Axons: PNS

Where do Somatic Sensory Neurons lie? & What is their function?

Function: Send information of body to CNS
SO position:
Dorsal Root Ganglia

What is the function of the Autonomic/Visceral PNS?

Control the internal organs, vessels & glands

What is the function of Meninges & Which 3 are there?

- Meninges: Membranes to protect the CNS

3 Membranes:
- Dura Mater: Outer Layer
- Arachnoid Membrane
- Pia

What is inbetween of the Pia & The Arachnoid Membrane?

Cerebrospinal Fluid (protection: Floating brain)

How many ventricles are there and what are ventricles?

4 ventricles: Fluid-filled cavernes (CSF)

What does a CT scan reveal of the brain?

- White/Grey matter
- Vesicles

What is neurulation? What happens if this goes wrong?

Neural plate forms neural tube

Goes wrong: Spina Bifida (open back)
Anencephaly (open head)

Interna Capsula: Function?

From thalamus to cortex
Also from cortex to spine (Corticospinal tract)

What does the Midbrain differentiate into? What are the functions?

Tectum & Tegmentum
Functions: Conduit for info passing from/to forebrain

What does the tectum differentiate into? What are the functions of the new area's?

Superior Colliculus (Optic tectum): Saccadic eye movement
Inferior Colliculus: Auditory information relay station (to thalamus)

What are the functions of the hindbrain?

Sensory information processing
Movement control
Autonomic NS regulation

Conduit spinal cord from/to forebrain

Where does the cerebellum get input from? Whats the function of the cerebellum?

Massive input from spinal cord & pons

Fine motor control

What is the function of the pons?

Switchboard/bridge
- Connecting cerebral cortex with cerebellum

What input do the Dorsal Horn Cells in the spinal cord get?

From Dorsal Root Fibers (sensory input)

What is the Function of Ventral Horn Cells in the spinal cord?

Project Axons in ventral roots to muscles

What cells are in the intermedial zone of the spinal cord & what is their function?

Interneurons
Function: Shape motor outputs in response to sensory input & brain command

What do we mean by the spinal cord being a conduit?

It's conducting (1 way stream) sends to brain or receives from brain and sends down

What are similarities of the brain from rats/humans? What are differences?

Similar: Telencephalon hemispheres are paired?
Difference: Gyri & Sulci in human much deeper

How many cell layers are there in the cortex? Where are the cell bodies?

6 layers.
Cell bodies are NOT in layer 1 (top) --> At least 1 layer does project to layer 1 though

What is the difference and similar between anscestors brains and our brains?

Difference: We have more association cortex
Similar: Primary sensory areass & secondary sensory areas with heavy interconnections with those primary sensory area's

How come we can perceive endless flavors?

1. Basic tastes get activated
2. Flavor comes from smell &&&&& taste
3. Other sensations/senses (texture/temperature)

When will a stimulus evoke a perception of taste, if we look at taste cells?

Only if threshold is met (critical amount)

What are the Apical End, Microvilli and Taste Pore of a taste receptor cell?

Apical End: Membrane region neaar the tongue surface: Chemically sensitive part of the taste receptor cell

Microvilli: Extension of apical end --> Projects into taste pore

Taste Pore; Opening in the tongue surface (exposure to mouth content)

What type of neurons are taste cells? How do their axons connect

Noob, zijn geen neurons.

Form synapses with gustatory afferent axons near bottom of taste bud

What is the process of the firing of a Taste cell?

Chemical(tastant) activates the taste receptor --> Membrane potential depolarizes.

Depolarization large enough --> Action potential --> Voltage gated calcium channels open --> Release of neuro transmitters

What neurotransmitter do sour & salty use?

Serotonine
(and some others but thats not important)

When talking about taste, what tastes use ATP as a neurotransmitter?

Bitter, sweet umami

(use some other transmitter but not important)

What is taste transduction?

Stimulus causes electrical response in sensory taste receptor

How does salt/sour change potention/channels of a taste cell?

Can pass directly through ion channels

SOUR: also can bind to & block the ion channels depending on the type of cell

How do bitter, sweet & umami influence cell channels?

Bind to G-protein-coupled receptors, which activates 2nd messenger which opens ion channel

Salt flavor --> Neurotransmitters into synaps: What happens?

Na+ selective channels --> Salt can go directly into cell --> Na+ goes up & causes depolarization--> Action potential --> Neurotransmitters into synaps

Sour flavour --> Neurotransmitters into synaps: What happens?

We don;t know but probably: H+ can bind to block K+ channels

Bitter flavour --> Neurotransmitters into synaps: What happens?

G-Protein-Coupled: Bind to these receptors (T1R & T2R)

Dimers: 2 proteins are affixed to each other
T2R receptors are poison receptors

Sweet, Bitter & Umami are all G-protein-coupled: What receptors do they bind on?

Bitter: T1R & T2R
Sweet: T1R2 & T1R3
Umami: T1R3 & T1R3

How does the flavour signal from the taste bud go to the cortex?

Taste buds --> Primary Gustatory Axons --> Brain Stem --> Thalamus --> Cerebral cortex

Where do taste axons bundle together?

In the cranial nerves:
- Slender Gustatory Nucleus (medulla)

What does taste information diverge into?

- Cerebral cortex: Conscious perception
- Neocortex (via thalamus): sensory information
- VentroPosteroMedial nucleus(VPM): Sends axons to the primary gustatory cortex

What happens in lesions of the thalamus or the gustatory cortex?

Ageusia: Loss of taste

What is the Labelled Line Hypothesis of taste and why is it incorrect?

Hypothesis: Specific taste receptors for basic tastes --> connect to seperate axon sets --> Specfic taste neurons in the cortex

Incorrect:
- Receptor cells are not specific for basic tastes (overlap)
- Primary axon sets are even less specific
- Single cell responses are ambiguous

The labelled line hypothesis is probably wrong, what is correct about neural taste coding?

Taste is broadly tuned: 1 cell can respond to more types of tastes

Population Coding Schemes:
- There are some specific receptors but population coding (broadly tunes neurons) are used for the stimulus properties

What is a Olfactory Ephethelium?

Small, sheet of cells in nasal cavity used for smelling

What 3 types of cells are in the Olfactory Epithelium?

Smell receptor cells: neurons
Supporting cells: Glia
Basal cells: source of new receptor cells

What are olfactory cells coated with and what is it's function?

Mucus (thin layer):
- Proteins in mucus concentrate the odorants
- Contains Antibodies to protect the brain

Where to in the mucus do odorants bind?

Cillia

What does an olfactory receptor neuron look like?

1 dendrite at surface of epithelium.
1 unmyelinated axon
Coated in mucus

What does the Olfactory Nerve (Cranial Nerve 1) consist of? Where does it end in?

Bundle of olfactory axons (some are separated)
Ends in: Olfacotory Bulb

Smell --> Action potential: What happens?

Odorant binds to odorant receptor proteins --> Stimulate G-protein --> activation of adenylyl cyclase --> form cAMP --> binding of cAMP to cyclic nucleotide-gated caton channel -->open cation channel --> Na+ & Ca2 influx --> Activated CL-channels cause current to flow

How can 100 types of receptor cells code for infinite type of smells?

Population coding schemes.
Each receptor protein binds differnt odors.
Receptor cells are senstitive to certain odors
BUT:
Each odorant activates many differne receptors

What are glomerulli & What is their function?

In mice: Spherical structures in olfactory bulb
Provide precize mapping between 25.000 primary smell axons to 100 second order axons
- Modulated by a lot of systems

What is the main coritcal area for smell?

Olfactory cortex
(Doesn't pass through thalamus)???

How can the brain distinct 2 odorants when 1 olfactory cell can't?

1. Population coding: Smell is large activation
2. Sensory map: odor organized into spatial maps
3. Temporal Coding: Time essential to coding

What area's are involved in the visual system pathway (brain?)

Lateral Genculate Nucleus (LGN) of the thalamus
Primary Visual Cortex
Striate cortex

What is the function of striate cortex in visual processing?

Feed visual info into occipital, temporral & parietal cortex

What is a Retinofugal projection?

Fugal = away
projection away from the retina

How does the optic nerve travel?

Exit retine at optic disc --> Fatty tissue --> into skull

What happens in the optic chiasm?

Decussation: crossing of bundles of the 2 optic nerves

What are the targets of the Optic Tracts? What are the function of these targets?

- LGN of the thalamus: Project further
- Hypothalamus: Biological rhythms & sleep
- Midbrain: Pupil size control
- Midbrain tectum (superior colliculus): Eye orientation

What is the input & output of LGN neurons in the thalamus?

Input:
- Retinal Ganglion cells
- V1 (corticofugal feedback)
- Input from brain stem neurons (attention, alert)

Output:
- Visual cortex (via optic radiation)

What are the 3 streams of visual information in the LGN?

1. M-type cells: Magnocellular (larger neurons)
2. P-type cells: Parvocellular (smaller neurons)
3. Koniocellular LGN layers: Tiny neurons (input from nonM&nonP cells and project to visual cortex)

What is so special about visual pyramidal cells?

Only pyramidal cells send axons out of the striate cortex to connect with other neural parts

What is the input & output of the different layers of striate cortex?

Input: LGN of the thalamus (IVC layer)
- IVCa: Magno
- AVCb Parvo

Output:
- Layer 2,3,4b pyramidal cells: Other cortical areas
-Layer 5: Superior Colliculus & Pons
-Layer 6: Feedback to LGN

How can we see ocular dominance in the striate cortex and in what layer?

There are Ocular Dominance Columns: Bands of cells>?

Layer 4

What is orientation selectivity and what neuron-layers are this? (visual)

- Neurons respond more if light matches size & orientation of receptive field

Layers:
- LGN
- Retina layers of the IVC

What is direction selectivity?

Neuron responds more if something moves optimally perpendicular to its orientation (motion)

What are simple cells (visual)?

Cortical neurons tha receive LGN input with receptive field aligned to 1 axis
- ON/OFF Fields

What are complex neurons (visual)?

Orientation selective cells that only fire when the orienation matches.
No ON-OFF center

What are Blob Receptive fields? (visual)

Neurons inside a Blob (a lot of input) respond differently from other visual cells
Most importantly: Wavelength sensitive
- No simple way to distinguish blob vs interblob cells

What is the path of the M-Type (magno-cellular) pathway? (& What function?)

M-type ganglion cells in retina --> Magnocellular LGN layers --> IVCa layer striate cortex --> (IVb layer striate cortex?)

- Motion perception & motor action guidance (WHERE PATHWAY)

What is the P-type pathway (Parvo-interblob pathway)? & Function?

P-type ganglion cells in the retina --> Parvocellular layers of the LGN --> IVa striate cortex layer --> Layer 2&3 interblob regions (striate cortex?)

Fine object analysis: (WHAT pathway)

What is the path of the Blob pathway of visual processing? (what is the function?)

Ganglion cells (notM or notP) --> Koniocellular layers of the LGN --> Blobs in layers 2&3 of the striate cortex --> Color object analyis (function)

What is a cortical module? What is nescessary & sufficient when talking about a cortical module?

When talking about vision:
Cortical Module: Block of cortex that is either:
- Nescessary: Removing the block leaves a blind spot
- Sufficient: This block contains all neural imagery to analyze both form & color

What area's are in the ventral stream? & Functions

Main function: Perception & Recognition

Area V4:
- Input: Blobs & interblobs of striate
- Large receptive fields
- Color & Orientation selective

Area IT:
- Input: output of V4
- Output to: Temporal lobe
- Complex neurons that respond to faces & objects
- Fusiform face area

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