Lecture 2 Flashcards
What makes a species?
Group isolated reproductively from other organisms (geographically, historically, behaviourally - courtship rituals)
Branching off when barrier separates subpopulations
- evolve independently until impossible to cross-fertilize
What is the evoltution of vertebrates?
Chordates - dorsal nerve cords Vertebrates -bone protecting nerves (Had neural tubes, have simple nervous systems)
What does primate mean?
Primus "first" "foremost" No single characteristic possessed by all 16 families -old world monkeys -hominid Apes are closest human living relative (chimps share 99% human genome) Homo, evolved from Australopithecus (8 species; 1=living homo sapient.) -many coexisted and inter-mated - homo sapient a combination of homo species Large brain cavity; largest homo species Used fire and tools Walked up right Modern humans (40K ya) -art writing agriculture ranching
How is the evolution of the brain and behaviour understood?
Constantly tinkering, not following a blueprint of some perfect design
-changes based off environmental context
-Rapid changes by advantageous mutation and or changes in environment
Exaptations are evolved functions that were coopted to serve additional functions
-High level motor sequencing - language
Similar traits are not always from the same origin. What is the difference between analogous and homologous?
Analogous - results from convergent evolution. (similar solution to same environmental problems (fins))
Homologous - from the same origin (sleep cycles)
What does the evolution of the brain look like?
Brain size does not = IQ
Relative brain size does not = IQ
Relative cerebrum to brain stem = best prediction of intelligence
(Increase in cerebrum size and convolutions (surface area))
Brain homologous in anatomy, structure, connectivity, function in related species
What is epigenetic?
The study of all mechanisms of inheritance other than the genetic code and its expression
Regulation of gene expression by environment
Only 1% of DNA is genes
Other 995 is regulatory coding like non coding RNA (regulates RNA expression)
Gene - environment regulate methylation and histone acetylation (exercise/diet, can be trans-generational (stress))
What is Methylation?
Is the reaction that occurs when a methyl group attaches to a DNA molecule
Reduce the expression of genes
What is histone
The reaction that occurs when a histone changes their shape and in so doing influences the shape of the adjacent DNA
Either decrease or increase gene expression
What does RNA do?
It translates the genetic code as it proceeds. It regulates whether to not genes are expressed
What is epigenetic in twin studies?
Epigenetic changes are a byproduct of experience and not genetics
Similar in early life and diverge with age
(depending on tissue type, monozygotic twins are not genetically identical - disease discordant monozygotic twins)
-See disease states that are different between them because of epigenetic
One is an alcoholic and the other isn’t because it is experience driven.
What are the 2 divisions of the nervous system?
Central nervous system (brain and spinal cord)
Peripheral nervous system ( nerves located outside the brain and spinal cord (motor and sensory))
What are is under the autonomic division of the peripheral nervous system?
Involuntary
Afferent nerves (info on state of organs, sensory)
Sympathetic and parasympathetic nervous system (oppose each other , fight/flight vs rest/digest - mobilize or store energy, indicative of arousal state
efferent nerves)
What is under the Somatic divisions of the peripheral nervous system?
Voluntary
Afferent nerves: bring info into the CNS A= approach
Efferent nerves: carry info out of CNS (motor) E= exit
What are anatomical difference in the sympathetic?
Come from different regions of the CNS
-Sympathetic - from the thoracolumbar region
Differing locations of ganlgia
- Sympathetic - close to spinal cord
Differing lengths of postganglionic fibres
- long
Postganglionic branching
-Lots, so that multiple organs can be mobilized at once
What is the anatomical difference in the parasympathetic?
Come from different regions of the CN -Parasympathetic - from the craniosacral region Differing locations of ganlgia -close to target organs Differing lengths of postganglionic fibres - short Postganglionic branching -very little branching
What are cranial nerves?
There are 12 pairs of nerves in periphery that originate on ventral surface of brain instead of spinal cord.
Purely sensory; olfactory and optic
Rest are autonomic, motor and sensory
Not part of the brain or spinal cord
How is the CNS protected?
3 layers of meninges -Dura -Arachnoid membrane -(subarachnoid space) -Pia Cerebralspinal fluid (cushions) Encased in bone
What are the three layers of the meninges?
Dura mater - hard outer layer - restrict movement within skill -sinus (drain deoxyblood and CSF waste) Arachnoid mater (web like) - subarachnoid space (CSF, large blood vessels) Pia mater -adheres to surface of the CNS -enclose CSF
What is the CSF locations?
Subarachnoid space
Central canal (runs the length of the spinal cord
Ventricles (interconnected by a series of opening, single reservoir, hydrocephalus)
Shock absorptions
What are ventricles?
Large internal chambers Produce and circulate CSF in brian (central canal in spinal cord) 4 ventricles -2 lateral -3rd -4th
What is the CSF?
Continually made in choroid plexus of ventricles (capillary network, protrude into ventricles via pia mater)
Circulates through ventricles to subarachnoid space (drain into jugular)
Cleans out metabolite and toxins
Supports and cushions the brain
What is the Blood brain barrier?
Keeps CNS physiologically separated from PNS
Semipermeable (transport mechanism)
Tightly packed cells surrounding blood vessels epithelial and glial cells
Electrochemical homeostasis
Kepp molecules outside of the brain
-hormones, drugs, bacteria, viruses, toxins, neurotransmitters
How does the BB break down?
High blood pressure At birth not completely forms High concentration of non permeable molecules (drug effects) Brain injury or disease Infection Microwaves and radiation
What are the cells of the nervous system?
Neurons
Glia (CNS)
Satellite cells (PNS)
Hundreds of billions
What is the anatomy of neurons (internal and external)?
Specialized cells for electrochemical signals -reception -conduction -transmission LOOK IN TEXTBOOK
What are nerve fibres
Nerve tracts
Ganglion and nucleus?
Nerve fiber = nerve process(axon or dendrite)
Nerve = bundle of nerve fibres in PNS
Tract= bundle of nerve fibres in CNS
Ganglion = cluster of neuronal cell bodies in PNS
Nucleus = cluster of neuronal cell bodies in CNS
What are astrocytes?
Largest glial cell -9 subtypes Star shaped Provide metabolic support to neurons Clean up neurotransmitters Signal NTs Hold neurons in place - rearrange synapses -control establish and maintain synapses Regulate ions in extracellular space Regulate blood floe to activate regions Form BBB Astrocytes sanctum : connected by gap junctions
What are microglia?
Really small Macrophages -engluf debris Multiply in response to injury/disease -mediate cell death Activate immune defence - antibodies can't pass bbb Fast acting Synaptic plastcity (formation or pruning) Sensitive to changes in K+
What are oligodendrocytes?
Only in the CNS Extensions wrap around axons -multiple axons -mulitple segments Rich myelin Form myelin sheath -speed condution -nourish axon -white matter - necessary for complex nerve interaction -occurs for 20 years postnatally
What are schwann cells?
Only in PNS
Each cell has only one axon segment
Guide regeneration
(only can occur in PNS)
What is the myelin sheath?
Composed of fats and proteins
• Synthesized by oligodendrocytes and schwann cells
• -Wrapped 250X+
• Speed conduc2on
• Saltatory conduc2on • Jump
• Not all axons myelinated • Large diameter
• Providenutrientsto segments far from cell body
• Loss=MS
What is the difference between glia and neurons
Glia
REGENERATE
• SUPPORT NEURONS
• MORE NUMEROUS THAN NEURON
Neurons
MULTIPLE PROCESSES (DENDRITES, AXONS, AND SYNAPSES)
• CANNOT REGENERATE
• REQUIRE GLIA TO SURVIVE
What is the orientation and direction of the nervous system?
First axis • Anterior= nose or front • Posterior=tail or back • Second axis • Dorsal=top of head (think dorsal fin) • Ventral=bodom of head • Third axis • Medial=midline • Lateral= away from middle
Spinal cord
Links brain to body & body to brain • 2 nerve roots • Dorsal • Sensory=afferent • Unipolar • Ventral • Motor=efferent • Mul2polar • 31 pairs • 4 regions • Cervical • Thoracic • Lumbar • Sacral • 2% of CNS • Major site of injury • Diagnose nature and loca2on of injur
What is the internal structure of the spinal cord?
White mader in periphery • Myelinated axons • Grey mader in middle • Cell bodies • Unmyelinated • Buderfly or H-shaped • CSF in central canal • Differs across 4 regions • Lower regions grey:white is higher • Lower level has less afferent & efferent nerves
What is spinal cord grey matter?
- Consists of neuronal cell bodies, interneurons and glia
- 4 main columns
- Dorsal horn
- Somatosensory nuclei
- Axon terminals of sensory nerves
- All levels of spinal cord • Ventral horn
- Motor neurons dendrite and cell body
- Innervate skeletal muscle (SNS) or internal organs (ANS)
- Lateral horn
- Intermediate column
- Autonomic nerves innervate visceral and pelvic organs (also lateral horn)
What are the 5 major divisions of the brian?
“ENCEPHALON” • IN THE HEAD BRAIN DEVELOPS AS 3 SWELLINGS • FORE • Forms into tele and di • MID • HIND • Met and myel
What is the myelencephalon?
• Most posterior—in hindbrain • AKA medulla • Ascending and descending tracts at core • Origin of re2cular forma2on • Core network of 100 nuclei • Also composes core of hindbrain and midbrain • Arousal system (re2cular ac2va2ng system) • Not really func2oning as a system
What is the mesencephalon?
Acsending and descending tracts • Cerebellum • Sensorimotor coordina2on • Maintain fine motor skills • Role in cogni2on/language/ aden2on • Pons • Contains re2cular forma2on • Swelling on ventral surface of brainstem • Transfer informa2on between the brainstem and the
What is the mesencephalon?
- Midbrain
- Tectum “roof”
- Superior collliculi • visuomotor
- Inferior colliculi
- Tegementum
- Re2cular forma2on (arousal) • Red nucleus (sensorimotor)
- Motor coordina2on: gait • Hemoglobin and ferra2n
- Substan2a nigra (sensorimotor)
- Reward, addic2on, and movement • Melanin
- Periaqueductal grey (analgesia) • Defensive behaviour
- Gate control theory of pain
- Releaseendorphinsanddense endorphin receptors
- Stimulaton=analgesia
What is the diencephalon?
- Thalamus
- 2 lobes
- Massa intermedia
- Runs through third ventricle to connect
- Sensory relay nuclei :see appendix V
- LGN: vision
- MGN: audi2on
- Ventral posterior nuclei: touch
- Feedback bidriec2onal to and from Thal ctx
- Consciousness?
Diencephalon
- Hypothalamus
- Under the thalamus
- Pituitary gland suspended by hypothalamus
- Release hormones via pituitary gland that modulate behaviour
- Stress
- Reproduc2on • Feeding
- Mammillary bodies
- Op2c chiasm • Decussate
- Contralateral • ipsilateral
What is the telencephalon?
• Cerebral hemispheres separated by longitudinal fissure • Corpus callosum • Largest tract connecting 2 hemispheres • Cortex convolutions • Gyri (hills) • Sucli/fissures (valleys) • Largest division of human brain • Controls sensory perception • Limbic system • Basal ganglia
telencephalon
4 lobes defined by fissures, not unitary
system
• Frontal
• Parietal
• Central fissure
• Occipital
• Temporal
• Lateral fissure
• STG=auditory
• IFT=object identity
• MTL=memory
• Longitudinal fissure
• Between hemispheres
• Precentral gyri
• Primary motor cortex
• Postcentral gyri
• Primary somatosensory cortex
• Superior temporal gyri
• Auditory cortex
• Prefrontal cortex
• Nonmotor portion of frontal lobeWhat is the neo cortex?
- 6 layers
- Layer 1 at surface
- Differ in
- Size of cell body
- Density of neurons
- Proportion of cell types
- Thickness
* Varies across brain
- Columnar organization
- Vertical flow of information
- Mini circuit
What are the two types of neurons in the neocortex?
- 2 types of neurons
- Pyramidal
- Large
- Multipolar
- Large dendrites
- Apical dendrites
- Reach surface
- Long axon
- Pyramidal
- Stellate
* Interneurons
* Small
* Star-shaped
What is the limbic system?
- Regulation of motivated behaviours
* 4 Fs
* Feeding
* Fleeing
* Fighting
* Sex - Structures circle thalamus
- Primitive cortex
* Hippocampus
* Spatial Learning and memory
* Cingulate cortex - Subcortical structures
* Amygdala
* Emotional memory
* Fear and anger
* Kluver-Bucy syndrome- Fornix
* Tract
* Hippocampus -> septum - Septum
* Anterior tip of cingulate cortex - Mammillary bodies
- Fornix
What is the basal ganglia?
- Motor system
- Voluntary
- Procedural learning
- Deep subcortical structures
- Amygdala
- Part of both limbic and bg
- Nucleus accumbens
- Medial ventral striatum
- Reinforcement learning
- Drug reward learning
- Amygdala
- Striatum (caudate nucleus+putamen)
- Striped
- Projections from substantia nigra
- Depleted in PD
- Globus pallidus
