Organization of the nervous system 2 - IISER Puneraghav/pdfs/neurobiology1/Lecture6... · 2013. 8....

19th August 2013 Bio 334 - Neurobiology I - Organization of the nervous system 1

Organization of the nervous system 2

Raghav RajanBio 334 – Neurobiology I

August 22nd 2013


Orienting within the brain – absolute axes and relative axes

ANTERIOR(in front)

POSTERIOR(behind)

INFERIOR(below)

SUPERIOR(above)

● Anterior/Posterior, Superior/Inferior – absolute axis system

● Rostral/Caudal, Dorsal/Lateral – relative to the long axis of the brain or spinal cord

http://www.rci.rutgers.edu/~uzwiak/AnatPhys/APFallLect19.html


Medial – lateral axes

MEDIAL(near the midline)

LATERAL(away

from the midline)

LATERAL(away

from the midline)

Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007) – Chapter 7


Ipsilateral and contralateral – things on the same side or the opposite side

IPSILATERAL (same side)

CONTRALATERAL (opposite side)



Planes of brain sections

Kandel, Schwartz and Jessell, Principles of Neural Science


Divisions of the nervous system

http://serendip.brynmawr.edu/exchange/brains/structures


Basal ganglia are a set of nuclei within the brain

● Clearly distinguishable cluster of neurons usually deep in the brain

● Shows up as a some gray matter often surrounded by white matter



Basal ganglia consist of 4 nuclei

● Striatum

● Pallidum

● Substantia nigra

● Subthalamic nucleus



The basal ganglia form loops with the cortex and thalamus

● Cortex - Basal ganglia-thalamus – cortex loops are important in the initiation and selection of movements

● Normal function disrupted in many diseases – Parkinson's disease, Huntington's disease

● Multiple parallel loops involved in other functions too



They are involved in movement selection and movement initiation

● Two pathways:

● Direct pathway – initiates movements

● Indirect pathway – suppresses movements

● Recent optogenetic experiments show this very nicely

– Supplementary videos 2 and 3 from http://www.nature.com/nature/journal/v466/n7306/full/nature09159.html#supplementary-information

Yin and Knowlton, The role of the basal ganglia in habit formation. Nature Reviews Neuroscience (2006)http://www.nature.com/nrn/journal/v7/n6/fig_tab/nrn1919_F1.html


Songbirds have served as a good model system for understanding the function of these loops

● Evolutionarily conserved – neuronal morphology, molecular markers, activity patterns, connections

● Specialized portion of this loop appears to be involved only in song learning

http://www.nbb.cornell.edu/goldberg/Doupe AJ et al. Songbirds could teach basal ganglia research a new song. Trends in Neurosciences 2005

http://www.nbb.cornell.edu/goldberg/


This loop is important for learning and is involved in generating variability required for learning

● Learning of complex movement sequences requires three steps

– Exploration using variability

– A mechanism to decide “good” and “bad” outcomes

– Selectively re-inforce “good” outcomes

Doupe AJ et al. Songbirds could teach basal ganglia research a new song. Trends in Neurosciences 2005


Basal ganglia loops are thought to form parallel circuits that have a number of other functions too

● Parallel loops with high degree of organization



Hippocampus and associated structures are involved in learning and memory



H.M. (Henry Molaison) revolutionized our understanding of function of hippocampus

● Surgery when he was 27

● Died at the age of 82

● Could not form new memories

● Only some types of memories were affected

● Could remember most things from before surgery

● CAVEAT: Lesions encompass larger area than just hippocampus

http://en.wikipedia.org/wiki/Henry_MolaisonMark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007) – Chapter 7


Diencephalon gives rise to thalamus and hypothalamus



Thalamus is the “gateway” to the cortex

● All sensory (except olfactory) are relayed to the cortex through the thalamus

● Thalamo-cortico-thalamic loops are believed to be important for consciousness



Midbrain gives rise to tectum and tegmentum

● Tectum consists of superior and inferior colliculus

● Superior Colliculus gets information from eye and controls eye movements

● Inferior colliculus gets information from the ears



Midbrain gives rise to tectum and tegmentum

● Tegmentum consists of red nucleus and substantia nigra

● Both are involved in controlling voluntary movement

● Corticospinal tract passes through the midbrain



Rostral hindbrain gives rise to cerebellum and pons



Caudal hindbrain gives rise to medulla



Cerebellum is again involved in modifying movements

● Gets detailed motor information through the pons about the commands that have been sent out from cerebral cortex

● Receives sensory information from the spinal cord about body position, etc

● Can then compare and adjust movements

● Lesions result in uncoordinated movements



Pons – a “switchboard” for the cerebellum

● Carries information from cerebral cortex to cerebellum

● Also controls a number of vital functions like breathing, sleep, bladder control, swallowing, etc.

Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007)


Medulla -

● Has motor neurons that control the tongue

● Receives a lot of sensory information from various senses

● A number of other autonomous functions

Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007)

Organization of the nervous system 2 - IISER Puneraghav/pdfs/neurobiology1/Lecture6... · 2013. 8....

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