Central Nervous System (CNS) Flashcards
What are the two divisions of the nervous system?
Central nervous system and peripheral nervous system
What factor gives humans more intelligence than animals?
The human brain has a high ratio of brain to body
What is the frontal lobe responsible for?
Human’s consciousness, cognitive abilities such as learning and memory
What impact does the high degree of gyrification (folding) of the cerebral cortex have?
Provides a higher surface area and greater cognitive functionality that can fit into a smaller cranium
What is the function of the cerebral cortex?
Sends messages to move skeletal muscles. Also performs activities like thinking, learning and remembering
What is the function of the basal ganglia?
Helps coordinate slow, sustained movements and supresses useless patterns of movement
What is the role of the thalamus?
Interprets sensory messages such as pain, temperature and pressure
What is the function of the hypothalamus?
Directs hormone secretions of the pituitary and controls homeostatic functions
What are the homeostatic functions of the hypothalamus?
Temperature, heartbeat and respiration
What is the role of the cerebellum?
Coordinates subconscious movements
Function of the brain stem
Origin of many cranial nerves
Regulates heartbeat and breathing
Transmits impulses between brain and spinal cord
What features does the cerebrum consist of?
Cerebral cortex and white matter (myelinated axons) and grey matter (neurons)
What are the deep folds (gyri) of the cortex called?
Fissures
What are the shallow folds of the cortex called?
Sulci
What is the main neuron that is found in the cortex?
Pyramidal neuron
Which neurotransmitter is released by pyramidal neurons?
Glutamate which causes excitation
Which neurotransmitter is released by interneurons?
GABA to cause inhibition
Which neurons are found in the cortex?
Interneurons and pyramidal
Where are basal nuclei found?
Cortex
What is the function of the 3 basal nuclei?
Initiate and terminate movement
Supress unwanted movement
Regulate muscle tone
Which diseases do basal nuclei have an effect on?
Parkinson’s and Huntington’s
What is the limbic system composed of
Parts of the cerebral cortex, diencephalon and midbrain
What are the main regions of the limbic system
Amygdala, the hippocampus, cingulate gyrus and fornix
Limbic system- Amygdala
Emotional processes
Limbic system- the hippocampus
Consolidation of new memories
Limbic system- cingulate gyrus
Linking motivational outcomes to behaviour
Limbic system- fornix
Memory
Diseases of the cortex
Alzheimer’s/Dementia
Epilepsy
Schizophrenia
Stroke
The structures of the thalamic region (Diencephalon)
Epithalamus, thalamus and hypothalamus
The structures of the thalamic region (Diencephalon)
Epithalamus, thalamus and hypothalamus
Function of the thalamus
Relay station for sensory impulses to the cerebral cortex (except smell)
Function of the hypothalamus
Uses neurochemicals and hormones to maintain homeostasis
Fight or flight- step 1
Amygdala senses a threat and signals to the hypothalamus
Fight or flight- step 2
Hypothalamus activates the sympathetic nervous system to release adrenaline
Fight or flight- step 3
Adrenaline increases heart rate, alertness and oxygen
The brain stem is made up of:
The midbrain, pons and medulla oblongata
The functional centres regulated by the medulla
Cardiovascular
Respiratory rhythmicity
Vomiting, coughing and sneezing
How does the medulla regulate body functions
With nuclei associated with the 5 cranial nerves
Where are the largest motor tracts in the body
The medulla oblongata, forming the pyramids
What is the decussation of pyramids
The left hemisphere of the brain controls muscles on the right and vice versa
What causes the decussation of pyramids
Axons from the left pyramid cross over to the right and vice versa
Role of the pons
Helps to control breathing
Role of the pontine (pons) respiratory group neurons
Act as an off-on switch where they increase and decrease breathing
The hormone released by Substantia nigra neurons (MIDBRAIN) and its role
Release dopamine and help control subconscious muscle activity
Loss of substantia nigra
Leads to Parkinson disease
The nuclei in the midbrain
Substantia nigra
Raphe nuclei
Locus coeruleus
Pedunculopontine nucleus
Hormones released by the Raphe nuclei
Serotonin
Hormones released by Locus coeruleus
Noradrenaline
Hormones released by Pedunculopontine nucleus
Acetylcholine
What is the reticular formation in the brain stem
Netlike arrangement of neuronal cell bodies and myelinated axons
The function of the reticular activating system (RAS)
Maintains consciousness (state of being awake) and prevents sensory overload
The cerebellum
Contains purkinje neurons that allow it to process a lot of information
Second largest part of the brain
Important role of the cerebellum
Unconscious motor coordination
Diseases associated with the cerebellum
Autism and ataxia
Definition of neuroscience
The study of how the nervous system develops, its structure and what it does
Function of glial cells
Helps to regulate neurons, insulates, supports, nourishes
Function of neurons
Sense environmental changes
Process information
Communicate changes to other neurons
Command body response
Reticular theory
Until 1888, Camillo Golgi siad the nervous system was a single continuous network
The neuron doctrine
1888- Santiago Cajal said the brain is made up of a single discontinuous cells (neurons)
Neuron charges
Negative intracellular charge and positive extracellular generates action potentials
Neuron charges
Negative intracellular charge and positive extracellular generates action potentials
Role of axons
Relaying information from one neuron to the next
Lack of synaptic transmission
Leads to death of neurons and mental disorders
Role of dendrites
Receive and process information sent from axons
Spiny/rough dendrites
More branched so they receive more information
How are astrocytes identified
By using glial fibrillary acidic protein as a marker (GFAP)
How does phenothiazine have antipsychotic activity
R2 hydrophilic side chain
3 subtypes of R2 groups of phenothiazine
Aliphatic chain, piperidinyl group and piperazinyl chain (more potent)
Mode of action of phenothiazines (antipsychotic)
Block dopaminergic receptors D2 in a stereoselective manner
How do neurons communicate
Electrical and chemical signals that inhibit or excite neuronal activity
Link between astrocytes and the blood brain barrier
Astrocytes processes surround the tight junctions and maintain and regulate the BBB
What is the main way that drugs cross the BBB
Specific transporter proteins and specific carrier transcytosis
What is excitotoxicity
High levels of glutamate causes overactivity of neurons which is toxic and destroys neurons
Most common cause of excitotoxicity
Stroke- lack of oxygen causes glutamate transporter to fail and glutamate accumulates
How do astrocytes prevent epilepsy
They take up potassium and stop it from building up
What is the myelin sheath in the CNS made of
Oligodendrocyte layers that are fatty and good for insulation
Role of the myelin sheath
Increases the speed of electrical impulses along the axon
What is the myelin sheath in the PNS made of
Schwann cells that only myelinate one axon each
Main cause of demyelination
Multiple sclerosis disease
What is demyelination
loss of myelination which causes axonal conduction block and degeneration
Role of microglia
Detect damage and respond rapidly
Become phagocytic
Activate during injury, inflammation, immune insults
Classification of neurotransmitters
- Synthesised and stored in presynaptic neuron
2.Released by presynaptic axon terminal
3.Produce response in postsynaptic cell
What is an agonist
Agents that bind to and activate receptors
What is an inverse agonist
Agents that bind to the same receptor as an agonist but produce the opposite response to the agonist
What is an antagonist
Agents that block receptors and stop agonists/inverse agonists from binding
Two major classes of receptors
Ionotropic (fast neurotransmission) and metabotropic (slow neurotransmission)
How do ionotropic receptors work
They form pores and channels that allow ions in and out of the cell when activated
How do metabotropic receptors work
G-protein coupled receptors that carries out biochemical cascades that increase or decrease proteins or calcium levels
Main excitatory CNS neurotransmitter
Glutamate- fast acting neurotransmitter
4 main glutamate receptors
NMDA, AMPA, Kainate and mGluR1-8
Most important drug targets for the glutamate system
NMDA receptors
Glutamate in brain function
Important for learning and memory because it mediates long term potentiation (LTP)
What is long term potentiation (LTP)
Strengthening of synapses which allows learning and memory to occur
Link between glutamate and dementia ?
Enhances cognition so research is ongoing
Main inhibitory CNS neurotransmitter
GABA (Gamma-Aminobutyric acid), less chance of action potentials
Dysregulation of glutamate activity leads to
Excessive excitability of neurons which causes epilepsy
NMDA impairment is linked to
Schizophrenia
GABA in pathogenesis of anxiety
Benzodiazepines relieve anxiety by producing GABAa transmission
GABA in muscle tone and epilepsy
GABAb agonists inhibit release of excitatory transmitters
Drugs that are used in epilepsy that work on GABA
Benzodiazepines treat status epilepticus and baclofen treats spasticity
What is status epilepticus
A seizure that lasts longer than 5 minutes or having multiple seizures without recovery in between
GABA in movement control
A major transmitter in basal ganglia so it is associated with movement disorders
Where are monoamine neurotransmitters derived from
Aromatic amino acids like tryptophan (serotonin) and tyrosine (noradrenaline)
How do monoamines and acetylcholine differ from other transmitters
Only expressed by a group of neurons in specific brain regions, they are called nucleus
What makes a group of neurons, a nucleus
Express a common chemical eg dopaminergic nuclei
Major Dopamine (DA) nuclei
Substantia nigra
Ventral tegmental area
Hypothalamus
Dopamine receptors (metabotropic)
D1, 2, 3 ,4, 5
What type of receptors are dopamine receptors
Metabotropic, they excite or inhibit
How does Reserpine work at NA and DA synapses
Inhibits VMAT and depletes dopamine stores
How does AMPT work at NA and DA synapses
Inhibits tyrosine hydroxylase and dopamine and noradrenaline synthesis
How does cocaine work at DA synapses
Inhibits the dopamine transporter
How does amphetamine work at DA synapses
Increases dopamine release via the transporter
How does pramipexole work at DA synapses
Partially selective D3 agonist
How does tropolone work at DA and NA synapses
Inhibits COMT
How does selegiline work at DA synapses
Inhibits MAOb
How do most antipsychotics work at DA synapses
Block D2 receptors but aripiprazole is a partial agonist
How do most antipsychotics work at DA synapses
Block D2 receptors but aripiprazole is a partial agonist
How does bromocriptine work at DA synapses
D2 agonist
How is DA and NA recycled
By MOA or COMT enzymes
Major noradrenergic nuclei
Locus coeruleus
Noradrenergic receptors (metabotropic)
Alpha 1 and 2 and Beta 1, 2, 3
Role of NA in brain function
Arousal (how awake you are), memory & cognition and stress response
How do SNRI and NRIs work at NA synapses
Antidepressants that inhibit noradrenaline transporter
How do SNRI and NRIs work at NA synapses
Antidepressants that inhibit noradrenaline transporter
How do MOA inhibitors work at NA synapses
Antidepressants that inhibit MAOb
How does prazosin work at NA synapses
a1 antagonist
How does yohimbine work at NA synapses
a2 antagonist
How does clonidine work at NA synapses
a2 agonist
How does propranolol work at NA synapses
B antagonist
Main serotonin (5 hydroxytryptamine- 5HT) nuclei
Collection of raphe nuclei in midbrain and pons
Serotonin (5HT) receptors
7 subclasses, all metabotropic except 5HT3
Functional role of serotonin
Sleep, pain, emotion
Major ACh nuclei
Nucleus basal
Medial septal nucleus and diagonal band
Pedunculopontine nucleus
ACh receptors
Nicotinic (ionotropic) - 17 subtypes
Muscarinic (metabotropic) 5 subtypes (M1-5)
