Midterm1 Flashcards
Neuroscience definition
Study of the nervous system
Psychology definition
Study of the mind
Mentalism ‘Theory’
Aristotle
Human intellectual functions are produced by the psyche (mind), a nonmaterial entitity
The brain’s purpose was to cool the blood
Psyche - proposed to be the source of human behaviour
-independent of the body
Dualism ‘theory’
Descartes
Thought the mind and body must be linked to form a person (duo)
- Definition: behaviour is controlled by 2 (dual) entities: a nonmaterial mind and a material body
- Hypothesized that the mind resides in the pineal gland where it directs fluid flow through the ventricles and into the muscles to move the body
Materialism idea
Darwin
Position that behaviour can be explained as a function of the nervous system without recourse to the mind
- Argues for objective and measurable descriptions of behaviour that can be referenced to brain activity
- Nonmaterial entity for mind - this idea was thrown out the window
Modern brain theory is materialistic
Darwin, however, did not propose a mechanism through which genes were inherited
behavioural neuroscience
the field that relates behaviour to biological processes
- how the brain regulates behaviour
- also how behaviour and experience can affect the brain
- Biological Psychology = behavioural neuroscience
What are some tasks faced by all living things?
Avoid harm or damage
secure energy and essential nutrients
secure conditions for reproduction
Darwin’s idea of Natural Selection. 3 Facts and 1 Inference
- Idvls of a given species are not identical - that is there is variation among individuals
- Some of this variation can be inherited (passed on from parent to offspring)
- Not all offspring survive. Some idvls live while others don’t
Inference: Variation among individuals affects the probability that they will survive to reproduce and pass along their traits/genes while doing so.
Mendel
Defined the laws of inheritance
Genes come in pairs and are inherited in distinct units, one from each parents
Hugo de Vries
Described the mechanism of mutation that leads to new traits forming - ie difference in phenotypes
What is the Linnaeus system?
An organization of animals that is based on morphology. It may not correctly reflect evolutionary history
ex Kingdom, Phylum, Class, Order, Family, Genus, Species
What is modern taxonomy?
An organization of animals based on evolutionary history. Compares the DNA to sort out evolutionary lineages. Can predict how long ago two species diverged from a common ancestor based on spontaneous mutation rates.
We now use a combination of both the Linnaeus classification system and modern taxonomy.
How many years ago was the first simple nervous system found in the fossil record?
700 million years ago
250 million ya - first brain
3-4 million ya - first human-like brain
1- 200 000 years ago - modern human brain
The Neuron Doctrine
Nervous systems are made up of discrete, individual, polarized nerve cells that contact eachother at synaptic junctions and form the developmental, functional, structural and trophic units of nervous systems.
Development of the Neuron Doctrine
Leeuwenhoek - POstulasted that nerves are tubes containing fluids/spirit carrying sensations from and to the brain
Purkinje - Identified cells within the nervous system
Schwann- Enunciates cell theory (how cells work/form)
Waller - discovered concept of anterograde nerve degeneration
Gudden - Traced connections between the main centres of the brain. Discovered trophic support
Kolliker - Supplied proof that nerve fibres are continuous with nerve cells
What were some key advances that lead to the development of the neuron doctrine?
Advances in microscopy - invention of compound light microscope
Golgi stain - guy named Golgi invented a stain for neurons although it only stain about 20% of the neurons which led to underestimating the amount of neurons in the brain - Why golgi thought neurons formed a continuous network (not discrete cells)
Continuous network vs Discrete cells in the nervous system
Cajal - thought neurons were discrete cells (neuronistas) and that they were NOT physically connected
Golgi - thought neurons formed a continuous network (reticulum). This was largely because the stain for neurons he developed only stain about 20% of the neurons and caused him to inaccurately picture brain functionality
Unity of Transmission
Synaptic contacts between two cells can be either excitatory or inhibitory, but will always be of the same type (with a couple exceptions)
Dale’s Law
Each nerve terminal releases a single type of transmitter (with a couple of exceptions)
Who is the only one that has a ‘true brain’?
The phylum Chordata
All of the members have a brain and spinal cord
Brain complexity generally mirrors behavioural complexity (largely due to proportionally larger cerebral cortex)
What are the three subphyla of Chordata?
Vertebrata, Tunicata, Cephalochordata
What characteristics of the brain can vary between different mammalian brains?
Size (of brain areas, brain), size of olfactory bulb and size of cortex
Number of cells
Density of cells
What types of changes are there within neuroplasticity?
- chemical change
- structural change
- functional change
These changes occur in response to inputs from the environment and growth ie. learning, experiencing
Plasticity definition
the ability of one genotype to produce more than one phenotype when exposed to different environments
ie. can alter traits based on changes in the environment
behavioural plasticity - ex. tool use
Two approaches to studying evolution of the brain/ancestral brains
2 is beneficial because you can see the live behaviour of the animals and compare it to their brain structures/ relative size of parts of their brain etc.
- Endocasts -look at skull/fill skull with a model to visualize what brain looked like
- study the brains of organisms who have not changed much since ancient times (salamanders, opposums)
Cerebellum
- Part of the hind brain associated with motor control and sensory processing
- Not included in the brain stem
- Gets larger specifically in mammals and birds compared with other vertebrates (Birds and mammals have complex motion/ sensory processing and thus require larger brain areas for these functions)
encephalization factor
a concept implying an increase in brain size relative to body size
associated with the evolution of the brain and intelligence
- on a graph, the encephalization factor is the distance away from the line. The further the distance from the line, the larger the encephalization factor
Changes in size of mammalian brain parts with increase in body size
- Medulla takes up a smaller portion of the brain
- Cerebellum maintains the same proportion of the brain size
- IsoCortex takes up a larger portion in the brain
Brain areas dedicated to visual processing in different vertebrate groups
Lampreys - Midbrain
Amphibians/Reptiles - Midbrain and Tectum
Mammals - Midbrain and Tectum and Cortex
Sulci vs gyri
Sulci are grooves (U) while gyri are folds (n)
Forebrain
Consists of the telencephalon for sure and maybe the diencephalon
What makes up the telencephalon?
isocortex, basal ganglia, limbic system
What makes up the diencephalon?
Thalamus and hypothalamus. Connect the forebrain and midbrain
What makes up the midbrain?
Mesencephalon
2 pairs of bumps on the back of the brain stem
-superior colliculus
-inferior colliculus
Also includes:
- the substantia nigra (part of the basal ganglia)
- red nucleus - connected with motor neurons in spinal cord
- start of the reticular formation (sleep and arousal, temperature, motor control)
What makes up the hind brain?
The metencephalon and the myelencephalon
What structures make up the metencephalon?
Cerebellum, pons
What structures make up the myelencephalon?
medulla
What does the brain stem include?
The midbrain + hindbrain - the cerebellum
Connects the brain to the spinal cord
Idea of phrenology
That certain brain areas have localized, specific functions or modules (Gall, Penfield, Broca, Wernicke)
Current view is that some actions have more localized parts of the brain but others, like more complex behaviours, require multiple brain areas.
Aggregate Field theory (Mass action)
Idea that the brain acts as a single functional unit
Current view is that some actions have more localized parts of the brain but others, like more complex behaviours, require multiple brain areas.
Basal ganglia
Part of the telencephalon (forebrain)
3 pairs of nuclei
2 associated pairs of nuclei
Includes: caudate nucleus, putamen, and globus pallidus
Substantia nigra, subthalamic nucleus
What brain parts are part of the limbic system?
thalamus, hypothalamus, hippocampus, amygdala
Involved in emotion, learning, memory, smell
Thalamus
Lots of nuclei. Filters sensory input - output to cortex
Hypothalamus
Lots of nuclei. Involved in homeostatic and endocrine functions
What does the pons do?
motor and sensory functions
input from some cranial nerves (sends output)
medulla
Receives input from the cranial nerves innervating the neck and the tongue
Regulates breathing and heart rate
Cerebellum
Part of the hind brain
Highly folded structure - neurons (Purkinje cells) tightly packed with lots of dendrites
Involved in motor control (fine motor movements) and various cognitive functions
Cerebral Cortex
Often called the neocortex/isocortex/cortex
- Well-developed in birds and mammals
- Has 6 layers of gray matter on top of white matter.
- Seat of cognition (Zero activity indicative of ‘brain death’)
-Includes the limbic cortex (3-4 layers of grey matter)
- 2500 cm2 SA
1.5 - 3 mm thick
Allocortex
aka mesocortex aka archicortex
- includes the hippocampus, and the olfactory cortex
- has only 3 layers
- projects information into the cerebral cortex
Layers of motor and sensory cortex
Layers l-lll: Integrative function
Layer lV: Input of sensory information
Layer V-Vl: Output to other parts of the brain
Cortical columns
Cohesive processing units
- All of the cells in the column respond to the same stimulus
- Adjacent columns respond to slightly different stimuli
- Span the entire thickness of the cortex
- The columns communicate with the columns next door - distinguish between stimuli (each respond slightly differently than the other)
What is a tract?
A collection of axons/nerve fibres running along in the CNS
What is a nerve?
A collection of axons/nerve fibres running along outside of the CNS (in the PNS)
What are the divisions of the peripheral nervous system?
Cranial nerves, spinal nerves (somatic NS), autonomic nervous system
Cranial nerves
12 pairs
Input and output for sensory organs and the face
Each cranial nerve deals with half of the face
They ALL emerge from the brain stem EXCEPT for the optic and olfactory nerve
Which cranial nerves DO NOT emerge from the brain stem?
Olfactory and Optic nerve
Where does the olfactory nerve emerge from ?
The olfactory bulb
Where does the optic nerve emerge from?
The lateral colliculis, a swelling on the temporal lobe of each hemisphere
How many pairs of spinal nerves are there?
31 Pairs of spinal nerves
8 Cervical
12 Thoracic
5 Lumbar
5 Sacral
1 Coccygeal
Bell-Magendie Law
The dorsal roots relay sensory information (AFFERENT)
and the ventral roots relay motor information away from the CNS (EFFERENT)
Sensory/Motor segregation in the brain
Sensory is dorsal - Midbrain - Colliculus
Motor is ventral - Midbrain - Tegmentum
The thalamus and the cortex are EXCEPTIONS to the dorsal/ventral associations with sensory/motor, respectively.
Sensory/Motor segregation in the brain
Sensory is dorsal - Midbrain - Colliculus
Motor is ventral - Midrbrain - Tegmentum
The thalamus and the cortex are EXCEPTIONS to the dorsal/ventral associations with sensory/motor, respectively
What are the two main divisions of the Autonomic NS?
Sympathetic and Parasympathetic NS
Consists of neurons both in the CNS and PNS
- Controlled by neurons in the CNS but there are also collections of neurons outside the CNS (ganglia) that play a role as well
Where do sympathetic nerves exit the CNS?
Thoracic and Lumbar regions
They innervate the sympathetic chain ganglia that are adjacent to the spinal cord.
Fight or flight
Where do the parasympathetic nerves exit the CNS?
Cranial and sacral regions
Rest and digest
The ganglia that these nerves innervate are further away from the spinal cord, adjacent to target organs
meninges
3 Layers
Dura Mater - tough mother - outer layer that is connected to the skull - surrounds the brain like a sac
Arachnoid Layer - thin, delicate membrane that follows the contours of the brain.
Pia Mater - delicate tissue that clings to the brain surface
Which meninge layers does the cerebral spinal fluid flow between?
The Arachnoid layer and the Pia mater
Ventricles
4 Interconnected compartments within the brain
Waste management system
Lateral ventricles, 3rd ventricle, 4th ventricle
Fluid-filled w/ CSF - cushion and support the brain
What produces cerebral spinal fluid?
Choroid plexus in the lateral ventricles
Cushions
Brings nutrients to the brain and takes away waste.
Flows through the ventricular system then exits the CNS
Circle of Willis
Provides collateral blood flow between the anterior and posterior regions of the brain
3 major arteries in the brain
Anterior, middle, and posterior cerebral artery
Parts of the axon
Axon hillock (where the axon starts)
Can branch into axon collaterals
Near the end, there are branches called teleodendria
Each ends with a terminal button
Between the terminal button and the next dendritic spine is a synapse
Axon collaterals can feedback to regulate the activity of the neuron (negative feedback system)- this prevents over activation. Turns self off after sending message.
How does neuron size predict function?
- neurons with long extensions likely relay information- neurons with short extensions likely engage in local processing
How many dendrites do sensory neurons have?
One simple dendrite
Efficient relay cells
Stellate cells
INTERNEURON - star-shaped
Collect information over a small area and project it locally
Many dendrites extend out from the cell body. Short axon
Pyramidal cells
INTERNEURON
Collect info in a small area but can project it a long way
Has a long axon and a pyramid shaped cell body
Has 2 sets of dendrites, apical and basal
Carries information from the cortex to the rest of the brain and spinal cord
Purkinje Cells
INTERNEURON
Extremely branched dendrites arranged in a fan-shape
Carry information from the cerebellum to the rest of the brain and spinal cord
One of the largest cells in the brain
Where are motor neurons located?
Cerebral Cortex, brain stem, and spinal cord
They have bushy dendrites to collect information
Usually large cell body and axon
Motor neurons
Have bushy dendrites to collect lots of information
Connect to muscles and therefore PRODUCE BEHAVIOUR
Large cell body and axon
Grandmother cell
Theory associated with function of neurons that states that each neuron controls a different aspect of behaviour - this idea is generally rejected now
INSTEAD - neurons work together in complex networks to code for specific aspects of behaviour –> the loss of one or more neurons would not affect behaviour typically, network can still function - NETWORK HYPOTHESIS
Network Hypothesis
INSTEAD - neurons work together in complex networks to code for specific aspects of behaviour –> the loss of one or more neurons would not affect behaviour typically, network can still function - NETWORK HYPOTHESIS
Ependymal cells
Cells that line the ventricles of the brain
They help generate cerebrospinal fluid and create/assist in the flow of the fluid
FOUND IN THE CNS
Microglia
FOUND IN THE CNS
Involved in the immune system and repair in the CNS
They clear dead cells (including apoptic neurons) - they work similarly to macrophages
Astroglia (Astrocyte)
FOUND IN THE CNS
They are star-shaped and provide structural support. They convey nutrients between the blood vessels and the neurons
Regulate blood flow
Help form the tight junctions for the blood brain barrier!
Can play a role in healing the brain after damage
Satellite glial cells
SUPPORT CELLS FOUND IN THE PNS
These are small cells that surround cell bodies of neurons located in the autonomic NS
Resemble the astrocytes of the CNS and assist in regulation of the external chemical environment
They are very sensitive to injury and may exacerbate pathological pain - lots of pain felt might be due to injury in these cells
Oligodendrocytes
FOUND IN THE CNS
These cells myelinate axons in the CNS. One oligodendrocyte can myelinate parts of multiple different axons
- Branch and myelinate several axon segments on different cells
Schwann Cells
FOUND IN THE PNS
Myelinate axons in the PNS
Myelinate only one segment of only one cell. There are multiple Schwann cells on a single myelinated axon.
Glioma
A brain tumor arisen from abhorrent glial cells
Multiple Sclerosis
A disease caused by damaged myelin on neuron axons. This affects the speed of transmission of neuronal signals and therefore affects communication in the nervous system
Why is repair within the CNS nearly impossible?
Formation of Glial scars - Astrocytes group around the injury and block communication through the axon. Blocks messages from getting communicated.
In the PNS, repair is possible due to glia
Successful Nerve regeneration in the PNS
Wallerian degeneration in the DISTAL END of the injured neuron. Myelin sheath and fibres are degenerated and consumed by macrophages. Distal end is removed and there is regrowth from the proximal end. Schwann cells regress and divide
Schwann cells form a path along which the axon can regrow and they myelinate the new axon.
Unsuccessful nerve regeneration
In the PNS
Wallerian degeneration whereby myelin and fibres are degenerated and phagocytized by macrophages. But then too many Schwann cells invade and form a blockage/scar that inhibits signal transduction - This nerve will not be capable of reinnervating the given muscle.
How many protein coding genes do humans have?
About 22 300
Tay-Sachs disease
A recessive disease caused by the enzyme hexosaminidase A (HexA) being non-functional. This enzyme normally breaks down certain lipids in the brain
Thus - when non-functional, the lipids will build up which can cause seizures, blindness, degenerating motor and mental function.
It eventually leads to death.
Because this disease is recessive, both alleles must be of the mutant genotype for the idvl to have the disease
Huntington’s disease
A dominant disease.
Caused by a mutant huntington protein building up in NS cells – this kills brain cells, especially in the basal ganglia and cortex
It is a movement disorder characterized by exaggerated movements (chorea)
Causes memory impairments and dementia
Symptoms often begin to appear after the idvl has had children
Down Syndrome
When an idvl has 47 chromosomes (Trisomy 21) instead of 46
This has profound effects on phenotype including changes to facial features, mental function, and susceptability to disease (Leukemia, Alzheimer’s, Respiratory infection)
