Download - Neurons and neuroanatomy v1.11
Brain Mind and Education
•Blackboard, Timetable Issues
•Books for this unit:
Paul Howard-Jones
Howard-Jones, P. (2010) Introducing Neuroeducational Research, Abingdon: Routledge.
Ward, J. (2010) A Student’s Guide to Cognitive Neuroscience (2nd Edition). New York: Psychology Press.
Neurons and Neuroanatomy• Neurons and other cells• Neural networks• How communication occurs
within them (AP)• Our nervous systems – key
orientation terms• Neuroanatomy: 3 parts of
brain, cortex (lobes) and some subcortical structures.
• Brodmann areas, some associated functions
• Locating function
© MethoxyRoxy / Wikimedia Commons / CC-BY-2.5
The neuron- a type of cell
© Quasar Jarosz . Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".
Dendrite
Axon
Node of Ranvier
Presynaptic terminal
Myelin sheathNucleus
Schwann cell
The membrane of the neuron has selective ion channels:
At rest , Potassium ions (K+) cross the membrane easily
Chloride ions (Cl-)and sodium ions (Na+) more difficulty crossing
Negatively charged protein molecules (A-) inside the neuron cannot cross
Also, a PUMP moves 3 Na+ out for every 2 K+in.
Result: Resting Potential (- 70 mV)
Resting Potential - neurons not sending signals….
outside
inside
Image attributed to @ Chris 73, updated by en:User:Diberri, converted to SVG by tiZom”/Wikimedia Commons / CC-BY-SA-3.0
Threshold (-55 mV) - something has to get the cell this far depolarized: then it all happens!
Sodium Channels open
More sodium Channels open
Sodium Channels close
Potassium Channels open Potassium
Channels close
LISTEN: Activity from a ganglion cell after the tooth of an anesthetized rat was tapped 5 times: ANIMATION
© Laurentaylorj /Wikimedia Commons / CC-BY-SA-3.0
Networks of neurons•Stimulated peripheral neuron depolarises neuron beyond threshold
•AP’s conveyed along axon often to dendrites of another neuron (via a connection: synapse)
•from whence signal may continue.
•So, neurons generate & mediate electrical signals in a complex and interconnected manner.
Image © Paul Howard-Jones 2014
Information Superhighways: Axons and Myelin
Myelin insulates, reducing losses and speeding up transmission from one node of Ranvier to the next
Loss of myelin (muscle weakness and seizures) associated with MS, and (temp.) viral infections
Myelin is whitish and gives rise to the colour of “white matter”N.B. Nuclei (s. nucleus) Densely packed grey matter areas
Afferent axons carry information to a particular place in CNS
Efferent axons carry information away
Cells other than neurons
Glial Cells: the housekeepers of the CNS:
Macroglia: Astrocytes (remove XS potassium ions, mop up leaked neurotransmitters)
Oligodendrocytes - make myelin - one cell can wrap several axons
Schwann cells - make myelin too- wrap single axons (chiefly peripheral NS)
Microglia: Cleaning up CNS debris – multiply with damage
Astrocyte© Magnus Manske / Wikimedia Commons / CC-BY-SA-3.0
Oligodendrocyte
Nervous systems (where neurons live)
Peripheral
Central
Brain
Spinal cord
Autonomic
- controls internal organs/glands
Somatic
- sensory to CNS (I/P), motor nerve fibres to skeletal muscle (O/P)
Sympathetic
- fight or flight, increasing energy use
Parasympathetic
- rest and digest, reducing energy
Key Orientation Termsdorsal/superior
ventral/inferior
caudal/ posterior
rostral/anterior
Image © Paul Howard-Jones
Ipsilateral: same sidebilateral: both sidesContralateral: oppositeMedial: towards middleLateral: away from middle
Proximal: nearDistal: far
Planes:
Sagittal: down middle Horizontal: horizontalCoronal: vertical between ears
More Key Orientation Terms
Ipsilateral Contralateral
lateral
brain stem (life support)
Neuroanatomy
internal organs input/output
fight/flight rest/digest
(Rhombencephalon)
© Looie496 created 2001
Brain = forebrain + midbrain + hindbrain
Brain = forebrain + midbrain + hindbrain
Brain 6wks after conception Adult brain
Image © Paul Howard-Jones 2014
Hindbrain
Medulla Pons Cerebellum
– maintains breathing, blood circulation
- relays movement, regulates breathing, taste and sleep
- motor coordination, precision, and accurate timing…and much more..
© Was a bee / Wikimedia Commons / CC-BY-SA 2.1 © Was a bee / Wikimedia Commons / CC-BY-SA 2.1
Tegmentum: nuclei connected to motor controlTectum: controls and relays sensor information
tegmentum
tectum
Midbrain
© Lypothymia. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".
Hypothalamus: (= below thalamus) maintains internal environment of body (homeostasis)
Forebrain – Diencephalon -> (caudal part of forebrain)
Thalamus: sensory relay to cerebral cortex
© Was a bee / Wikimedia Commons / CC-BY-SA 2.1
Forebrain – Telencephalon ->CORTEX
+ many subcortical structures (striatum, amygdala, hippocampus etc)
Brain Stem (life support)
Neuroanatomy
The human cerebral Cortex is highly folded (original area = double page of tabloid newspaper)
gyrus/gyri = ridge(s)
sulcus/sulci = valley (s)
Cerebral hemispheres- Separated by the longitudinal fissure (red below)– connected by commissures, esp: corpus callosum (bundles of myelinated axons)
© Was a bee / Wikimedia Commons / CC-BY-SA 2.1
Four lobes
Image © Paul Howard-Jones 2014
Hidden cortex: the cingulate (=“island”) cortex
Image © Paul Howard-Jones 2014
Find the region…..and mark on your colouring book
• Inferior frontal sulcus
• Superior temporal gyrus
• Dorso-lateral prefrontal cortex (DLPFC)
• Superior frontal gyrus
• Anterior cingulate
Dorso-lateral prefrontal cortex (DLPFC) – band running across top of frontal lobes
Superior temporal gyrus – highest ridge travelling along the temporal lobe
Inferior frontal sulcus – lowest valley travelling along the front
Anterior cingulate - front of the large inner island
Superior frontal gyrus – highest ridge along frontal lobe
Medial/Sagittal section
Images © Paul Howard-Jones 2014
Brodmann Areas (or regions)
• Brodmann divided according to cytoarchitecture (organization of cells)
• BA 1, 2, 3 = primary somatosensory cortex
• 4 = motor cortex
• 5, 7 = secondary sensory cortex
• 6 = supplementary motor area (medial) and premotor cortex (lateral)
• 9/46 = dorsolateral prefrontal cortex24, 32 = anterior cingulate cortex 17 = primary visual cortex
41 = primary auditory cortexmedial or sagittal section
Functional Architecture - some initial principles and warnings...
* Memory, attention, emotion, etc. are more complex than sensory and motor functions – no one part of the brain is responsible for these. (Higher functions such as creativity even more complex)
* Avoid Phrenology!
The complexities of touching a cup of soup….
+
Distributed multimodal activations will instigate further even more complex activations (type of handle, spilling, burning tasty cups of soup – tomato – mmmm -> anticipation in the striatum) and anterior cingulate (concentration), frontal cortices (decision-making )…..
motor somatosensory
parietal
premotor posterior parietal
parietal
temporal association
cingulate
parahippocampal
The complexities of touching a cup of soup….
Motor and somatosensory are topographically organised (fingers, hand, arm, etc) and close – good to have input/output close together – feeling/moving
e.g. Information from the thalamus reaches somatosensory cortex, and from there to motor and also to there into a unimodal somatosensory association area – allowing the shape to be formed from touch.
From here, it feeds to premotor areas (e.g. preparing movement in respect of feeling the shape), and to higher order more posterior unimodal association areas.
It then converges with information from other sensory systems in multimodal association areas, e.g parahippocampal, temporal association and cingulate cortices
Image © Paul Howard-Jones 2014
Activity via blood flow with radioactive water
- or via glucose metabolism with radioactive deoxyglucose
•Accurate targeting using chemical messengers
•Poor spatial and temporal resolution, safety limitations
PET - Positron Emission Tomography
Locating brain function …..
- records the low level electrical fields created by neural activity.
Very good temporal resolution, good for children.
Spatial resolution not great –but improves with number of electrodes!
Can use with specific behavioural markers – event-related potentials (ERP’s)
EEG - Electroencephalography
© Kristina Walter / Wikimedia Commons / CC-BY-SA-3.0 / GFDL
Theta 4 Hz to 7 Hz - relaxed, meditative, and creative states.
Alpha 7 Hz to 14 Hz – emerges with relaxation
Beta 15 Hz to about 30 Hz – dominant when anxious
Copyright (c) Hgamboa Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License“.
fMRI
- functional Magnetic Resonance Imaging
- Blood flow links to neural activity: active neurons consume oxygen, but increased blood flow occurs without matched oxygen extraction - causing an overall increase in blood oxygen.
- Hemaglobin (blood) differs in its magnetic properties from dioxyhemaglobin (oxygenated blood) and thus has a different magnetic resonance (MR) response to a magnetic field (being pulsed by radio waves).
- Differences in MR response allow an image to built up of the blood oxygenation. By subtracting the data from two conditions, which differ only with respect to the cognitive function being studied, brain activity due to the function can be mapped from the Blood Oxygenation Level Dependent (BOLD) signal.
Anatomy Function
fMRI - functional Magnetic Resonance Imaging
Spatial resolution (visual detail): Very good
Temporal resolution: OK - in terms of seconds
Comfort of participants and convenience: Not great really – loud sound, confined space
Apparently no health limit
Image © Paul Howard-Jones 2014
Image © Paul Howard-Jones 2014Image © Paul Howard-Jones 2014
www.cricbristol.ac.uk
Summary
• Neurons and other cells• Neural networks• How communication occurs within them (AP)• Our nervous systems – key orientation terms• Neuroanatomy: 3 parts of brain, cortex
(lobes) and some subcortical structures. • Brodmann areas, some associated functions• Locating function