Neurobiology A

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Sagittal plane

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front to back

http://upload.wikimedia.org/wikipedia/commons/e/e1/Human_anatomy_planes.svg

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Coronal plane

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left to right

http://upload.wikimedia.org/wikipedia/commons/e/e1/Human_anatomy_planes.svg

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Transverse

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horizontal (standing)

http://upload.wikimedia.org/wikipedia/commons/e/e1/Human_anatomy_planes.svg

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Central nervous system includes?

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Brain and spinal cord (anything surrounded by bone)

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chiasm

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point in the brain where the optic nerves cross over (the majority of the nerve fibers coming from the left eye cross over to the right side of the brain and vise versa for the right eye)

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peripheral nervous system

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Anything outside CNS (anything except brain and spinal cord)

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divisions of peripheral nervous system

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autonomic nervous system (ANS): internal organs, unconscious
somatic nervous system: voluntary control of body movements via skeletal muscles

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somatic motor neuron neurotransmitter

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acetylcholine

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somatic nervous system

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Motor: striated muscles (so-called because of their striated or stripped appearance)

Sensory: give the brain information concerning the extent of stretching

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motor neuron location

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The motor neurons have their cell bodies
(containing the cell nucleus) in the CNS and their terminals in periphery

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striated muscles

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Muscles of movement; "skeletal muscles"

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acetylcholine

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released from the nerve terminals of the motor neurons, causes contraction of the striated muscles

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(neuron arrangement) autonomic motor innervation of peripheral targets

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two motor neurons; the neuron coming from the spinal cord (preganglionic) makes synaptic connection with another neuron (postganglionic) that innervates the peripheral target; synapses grouped in ganglion

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ganglion

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collection of neuronal cell bodies

(visible with naked eye)

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cerebrum

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brain

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synapse

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a structure that permits a neuron to pass an electrical or chemical signal to another cell (neural or otherwise)

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Autonomic motor neurotransmitter

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pre-ganglion: acetylcholine
post-ganglion: parasympathetic acetylcholine, sympathetic noradrenaline

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autonomic nervous system

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Motor: smooth muscles (internal organs)

Sensory: informs the brain about the extent of the filling of the tubes

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smooth muscles

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Internal organs (usually autonomic nervous system). Often these muscles are found around tubes such as the gut, bladder, heart, blood vesicle
and uterus.

Exception: heart is striated, but part of autonomic nervous system

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heart

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striated muscle (usual for somatic) but controlled by autonomic nervous system

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division of autonomic nervous system

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parasympathetic: rest-and-digest = trophotropic
sympathetic: fight-or-flight
differ in the nature of the post-ganglionic neuron

(Some sources distinguish an additional third: enteric nervous system, for digestion, but the course doesn't seem to mention it)

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Parasympathetic function

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rest-and-digest

Situations: sexual arousal, salivation, lacrimation (tears), urination, digestion, and defecation

Actions: increase blood flow to digestion, stimulate arousal, constrict pupils for closer vision

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Sympathetic function

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fight-or-flight

Situations: danger, stress, ...

Actions: accelerated heart and lungs, slow digestion, increased liberation of nutrients...

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Parasympathetic neurotransmitter

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acetylcholine (excitory for some organs and inhibitory for others)

(Note that this is the postganglionic neuron; the preganglionic neuron always uses acetylcholine)

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Sympathetic neurotransmitter

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noradrenaline (excitory for some organs and inhibitory for others)

(Note that this is the postganglionic neuron; the preganglionic neuron always uses acetylcholine)

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parasympathetic and sympathetic synergy

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parasympathetic and sympathetic typically have opposite effects: some organs are inhibted by sympathetic and excited by parasympathetic, while for others it's the other way around.

Together they make up the autonomic nervous system

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trophotropic

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At rest; eating and elimination of
body wastes
parasympathetic system

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ergotropic

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Active;
sympathetic system

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"rest" and "active" systems

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rest: trophotropic
active: ergotropic

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CNS communication with the periphery

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peripheral nervous system
neuroendocrine system

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adrenal medulla

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Part of adrenal gland (Dutch: bijnier) that releases hormones basedon neural input from the CNS

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adrenal medulla resemblance to sympathetic nervous system.

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equivalent to a post-ganglionic neuron of the sympathetic nervous system; pre-ganglionic neuron innervates the chromaffin, which releases noradrenaline and adrenaline into the blood (hormones)

"these hormones bind adrenergic receptors on target cells, where they induce essentially the same effects as direct sympathetic nervous stimulation." www.vivo.colostate.edu/hbooks/pathphys/endocrine/adrenal/medhormones.html

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chromaffin
(hint: synapse?)

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Endocrine cells in adrenal medulla that release noradrenaline and adrenaline into the blood

Recieves information from CNS through neurons that don’t form synapses with postganglionic neurons, but rather run through the ganglions to directly innervate the cells

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hormone

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message molecule that travels through blood

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endocrine cell

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cell releasing molecules within the body
E.g. hormones

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exocrine cell

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cell releasing molecules outside the body
E.g. sweat

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Noradrenaline

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Neurotransmitter in sympathetic autonomous system (post-ganglionic)

Hormone in adrenal medulla

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adrenal medulla function

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The CNS activates the adrenal medulla when a massive activation of ergotropic functions in the body is requires

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hypothalamo-hypophyseal system

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hypothalamus plus pituitary gland, major neuroendocrine organ of the body

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pituitary

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directly or indirectly regulated by neurons from the hypothalamus,

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Brain input

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sensory nervous system (e.g. sensory divisions of the autonomic and somatic nervous systems)

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Brain output

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autonomic and somatic nervous system and the neuroendocrine system

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Receptor cells

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sense changes in the periphery (internal or outside world) and relay to brain

Also called 'sensorycells' and not to be confused with receptor proteins

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sensory transduction

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change in the periphery causes a change in the electrical potential of the cell ("receptor potential");

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receptor potential

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change in the electrical potential of receptor cell based on some change in periphery (large environment change -> large potential change; the signal is analog)

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sensory coding

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convert the receptor potential into action potentials; digitalisation of signal

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action potential

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signal of fixed shape that travels along neuron. (large signal -> high frequency of action potentials; the potential change is always the same size; the signal is digital)

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Axon

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Branch of neural cell that transducts information away from the cell body to other cells.

Exception: In some sensory cells, an axon (different branches) transduct information to and from the cell.

http://www.naturalhealthschool.com/img/nervecell.gif

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Dendrite

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Branch of neuron that transducts information (usually from other cells) to the cell body of the neuron.

http://www.naturalhealthschool.com/img/nervecell.gif

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What determines the amount of neurotransmitter (stepwise) from receptor cells to CNS?

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Magnitude of environmental input -> size(/freq) receptor potential -> frequency of action potentials -> amount of neurotransmitter release

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sensory types

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olfactory (smell)
auditory (hearing)
vision
somatic (pain, posture, ...)
gustatory (taste)

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Four receptor cell types

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chemoreceptors
photoreceptors
thermoreceptors
mechanoreceptors

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Vision

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Protein opsin combined with chemical retinal (light-sensetive) transfucts sensory information in the eye

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Opsin

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Protein that transducts visual information, very similar to the structure of a G protein coupled receptor (especially noradrenaline).

(Absorption is done by retinal)

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Olfaction

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Smell

Large family of G protein coupled receptors, for detecting the various chemicals

Only sense that does not go though the thalamus

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Taste

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G protein coupled receptor for sweet and bitter
Ion channel for salt (Na), H (sour)

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Mechanoreceptors

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Mechanoreceptors anchored within and outside the cell; relative changes cause the ion channel open probability to change to create a receptor potential
(A fast system, which is necessary)

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Touch vs pain vs itch

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Different neurons for touch, pain and itch, having different tresholds and different types of ion channels and GPCRs

Pain receptors inhibit itch receptors

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Touch receptor

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Receptor: Na+ ion channel called Brain sodium channel 1 (BNC1)

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Pain receptor

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Receptor: Trp Channel

Inhibits itch receptors (that's why scratching helps)

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C fibers

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Somatic sensory system, unmyelinated (so it is slow transduction)

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Itch receptor

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Receptor: GRPR, a G protein coupled receptor

Inhibited by pain

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myelinated

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Structure around transduction part of many (not all) neurons that causes signal transduction speed to increase greatly

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KO

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Knock out; disabling a protein, research differences between normal and KO (without the protein) animals, to know function of the KO protein

(If the animal can live without the protein)

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Capsaicin

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chemical in hot chili pepers that is responsible for the sensation of heat

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Way to find receptor protein

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Locate the cell group, find expressions of genes by cDNA; trigger the cells (e.g. by capsaicin for heat), find which genes increase expression.

Possibly measure Ca2+ changes to find which cells respond, before looking into expressions

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Heat sensor

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A.k.a. "capsaicin receptor"
TRP ion channel
Can also act as mechanoreceptor

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TRP (what is it & 3 types)

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Very large system of ion channels in vertebrates (Dutch: gewervelden)

Originate from K+ channels

TrpC
TrpV
TrpM

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Cold receptor

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TRP channel (TrpM6), comparable to heat

(In fact it was found by looking for things structurally related to heat receptor)

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CMR

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Cold and menthol receptor (because menthol has a cold sensation)

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Why do chili peppers produce capsaicin?

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Chili seeds don't survive mamal digestion so discourage mamals from eating

Seeds do survive for birds, which are immune to capsaicin

(Both use TRPV1 receptor but slightly different version)

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TRPV1

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Heat receptor

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Hypothalamus

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Important area for brain output (autonomic nervouw and neuroendocrine)

"Full of programs"

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Stereotactic method (2 steps)

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Method to artificially activate brain area's (in live animals)

1. Construct a map of the brain, usually by dissecting dead animal
2. Put electrode in brain of a highly resembling living specimen (operate while unconscious but can experiment while conscious)
(3. Usually, the animal is killed and the brain examined, e.g. to verify position)

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Stereotactic method (5 different experiments)

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1. Weak current to activate region
2. High current to disable region (permanently) ('lesion')
3. Record action potentials
4. Put fluid in the brain (e.g. neurotransmitter)
5. Remove chemicals from the brain

All these are very localised

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Iontophoresis

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Put chemicals in a precise location of the brain (one application of stereotactic method) when current is applied
Alternatively pump chemicals out of the brain

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Hypothalamus programs

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Complete programs, e.g. 'eating' which encompasses walking to food, raising blood to digestive tract, etc.

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Brain information flow

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Cortical fields -> limbic system -> hypothalamus

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Cortex

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Learned programs

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Hippocampus

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Inborn programs

Part of limbic system

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Limbic system

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Inborn programs

There are some plastic (changable) parts, e.g. short term memory

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Fornix

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Bundle of axons between limbic and hypothalamus

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Amygdala

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Store fear memories

(related to hippocampus)

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Toxoplasma
(probably not important)

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Infects the brain of rodents so they lose feat of felines; this this way the toxoplasma can sexually reproduce

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Avoidance behaviour functioning

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When treat is far away, lateral amygdala shows strongest response under control of prefrontal cortex: learned behaviour

When treat is close, central amygdala shows strongest response; hard-wired behaviour (advantageous because faster)

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PFC

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Prefrontal cortex; complex behaviour (planning complex cognitive behavior, personality expression, decision making and moderating social behavior)

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Primary somatic cortex

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Information is sent to motivational system (limbic) and directly to motor cortex; limbic system sends through to motor cortex if deemed appropriate

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Celebellum

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Information on muscles positons, sense of balance and motor neurons is combined to adjust movement directed by motor cortex

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Vestibular system

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Sensor of balance, in inner ear

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Vector coding

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Different types of receptors are activated to different extent; this is combined into a vector containing a combined sensation.

E.g. a score for sour, bitter, sweet, salt and umami on a scale from 1 to 10 would combine to 10^5 = 100.000 tastes.

(This is of course much more efficient than 100.000 different receptos)

Olfaction (smell) is an exception, using many different cells rather than vector coding. (You can apparently also think of it as advanced vector coding)

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Umami

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Fifth taste sense
Detects amino acid L-glutamate among other things
Japanese for "meaty"

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Retinal

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Compound responsible for absorption of light in the eye

Wavelength is determined by the type of protein to which retinal is attached

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Vision

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Red, green and blue (cone opsin red cell etc) are vector coded to represent all visible colors

Absorption is done by retinal and passed on by opsin

Most mammals can detect 2 colors, many birds/fish can detect 4/5

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Two -> threechromatic

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red light gene into mouse -> mouse could see red (apparently any neural rewiring necessary just follows)

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Taste

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Sweet, sour, bitter, salty, umami are vector coded

There is no tongue map, all tastes on all taste-sensetive parts of tongue

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Sweet

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One receptor for sugar (different sugars are sufficiently similar to be detected by one receptor)

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Sour

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One receptor for H+ (proton)

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Salt

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One receptor for Na+

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Bitter

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There are many receptors but they are all in the same cells. As such, many unrelated chemicals are bitter, but we cannot distinguish them

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Olfaction

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Many (hundreds) of receptors, each having it's own cell type (unlike bitter taste). Not the usual vector coding

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Olfaction - control over types

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One receptor activates at random, suppressing the suppression of all others in that cell.

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Ca2+

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all transmembrane signaling mechanisms, including sensory transduction, will ultimately cause a change in intracellular Ca2+ (probably a safe assumption)

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Olfaction recognition (& speed)

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Different inputs are in the brain translated to signals corresponding, for example, to a specific other individual (in mice or other animals with better smell than humans)

When recognizing individual mice, the response takes several seconds, which is the cost for high accuracy. When recognizing predators, less accuracy is needed and the response takes milliseconds instead.

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Pheromones

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a secreted or excreted chemical factor that triggers a social response in members of the same species.

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Olfaction genes

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There are around 1000 olfaction genes in the family for many animals, but for animals with poor smell (humans) many of them are pseudogenes.

Animals who can see more colors can generally distinguish fewer smells; it seems the brain can handle a maximum amount of input

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Thalamus

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relaying sensory and motor signals to the cerebral cortex

regulation of consciousness, sleep, and alertness

positioned in the center, sagitally

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Vision, olfaction, taste, mechano
GPCR or ion channel?

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Vision, olfaction GPCR
Mechano ion channel
Taste: bitter/sweet GPCR; saltsour ion channel

(unami unmentioned, hearing is perhap mechano)