CNS 1 Flashcards
what are the major brain structures?
- hindbrain
- midbrain: tectum, tegmentum
- forebrain: telencephalon, diencephalon
what does the hindbrain consist of?
cerebellum
pons
medulla
reticular formation
what does the tectum consist of?
superior and interior colliculi
what does the tegmentum consist of?
periaqueductal gray
substantia nigra
red nucleus
what does the telencephalon consist of?
- cerebral cortex
- corpus callsoum
- limbic system (hippocampus…)
what does the diencephalon consist of?
- thalamus
- hypothalamus
- pituitary gland
- pineal gland
what are the major neurochemical systems in the brain?
- noradrenaline
- dopamine
- serotonin
- ACh
- glutamate
- GABA
what does the surface anatomy of the brain include?
cerebral hemispheres
cerebellum
brain stem
what is the brain composed and constituted of?
wrinkled pinkish gray tissue
nerve cells, glial cells, blood vessels and cerebrospinal fluid
the brain contains almost …. of the body’s neural tissue
98%
the brain exerts vital and adaptive functions
give examples of these?
- sensory reception and integration
- muscle control + coordination
- temperature + sleep wake cycle regulation
- speech production, memory storage, reasoning, judgement ..
what does the CNS do?
integrates info that it receives + coordinates activity
what forms the CNS?
brain + spinal cord
what are dendrites?
short fibres
through which neurones (cell body) receive info
what do axons carry?
outgoing messages from cell
what does a group of axons bundled together make up?
- nerve in PNS (cranial + spinal nerves)
- tract in CNS
define nucleus?
collection of neuron cell bodies in CNS
define ganglion?
collection of neurones cell bodies in PNS
what is an exception to the ganglion?
basal ganglia
located in forebrain
what does the basal ganglia consist of?
subcortical nuclei
inc: caudate putamen, globus pallidus in cerebrum, substantia nigra in midbrain, subthalamic nucleus in diencephalon
what are the 3 main nerve tracts in the CNS?
- association fibres
- commissural fibres
- projection fibres
association fibres
connect cortical areas within same hemisphere
commissural fibres
connect corresponding cortical areas in 2 hemispheres
cross from one cerebral hemisphere to other via bridges = commissures
projection fibres
connect cerebral cortex with corpus striatum, diencephalon, brainstem + spinal cord
what are the categories of nerves?
- afferent nerves
- efferent nerves
- mixed nerves
afferent nerves
signals from sensory neurones to CNS (from mechanoreceptors in skin)
efferent nerves
signals from CNS long motor neurones to target muscles/glands
mixed nerves
have both afferent + efferent axons
conduct both incoming sensory info + outgoing muscle commands in same bundle
what is the ascending/afferent pathway?
one/series of neurones projecting from periphery toward brain
what is the descending/efferent pathway?
one/series of neurones projecting from brain toward periphery
nerves can be categorised into 2 groups based on where they connect to CNS
what are these 2 groups?
- spinal nerves
- cranial nerves
spinal nerves
connect through vertebral column to spinal cord and to CNS
given letter-number designations according to vertebra which connect to spinal column
cranial nerves
innervate parts of head + connect directly to brain (espesh brain stem)
assigned Roman numerals from 1-12 + descriptive names
what are some axons covered with?
myelin sheath
made up of glial cells
myelin sheath inc neutron efficiency + provides insulation
what is multiple sclerosis (MS)?
most common demyelinating disease of CNS
when does Guillain-Barre syndrome (GBS) happen?
when body’s immune system attacks myelin sheath in PNS
both the spinal cord and brain consist of white + gray matter
describe both matters?
white matter = bundles of axons coated with myelin sheath
gray matter = masses of cell bodies + dendrites -> covered with synapses
sensory neurones
carry signals from outer parts of body (periphery) into CNS
motor neurones
carry signals from CNS to outer parts of body
interneurones
connect various neurones in brain + spinal cord
which nerves fibres are myelinated?
A-alpha
A-beta
A-delta
A-alpha (motor neurones)
which nerve fibres are unmyelinated?
C-nerve fibres
the thicker the nerve fibre the ….
faster info travels in it
what does the axon hillock control?
firing of neuron
what does a gate keeper/sensor do?
sums total inhibitory + excitatory signals
if the sum of inhibitory + excitatory signals inc, what will happen?
AP = triggered
electrical signal transmitted down axon away from cell body
what is an AP carried by?
neurotransmitters
what are neurotransmitters made by?
cell sending impulse (pre-sn)
stored in synaptic vesicles at end of axon
define receptors in post sn?
chemical-gated ion channels
what are sensory receptors either?
specialised endings of afferent neurones / separate cells that signal to afferent neurone
detect + respond to physical/chem stimuli
convert one form of energy to another
give examples of external and internal sensory receptors?
external - cutaneous
internal - (visceral/somatic)
contribute to variations in sensitivity (2 point discrimination)
give examples of sensory receptors?
- photoreceptors
- mechanoreceptors
- thermoreceptors
- osmoreceptors
- chemoreceptors
- proprioreceptors
- polymodal receptors
- nociceptors
chemoreceptors
chemical composition (O2, CO2 + chemicals linked to taste and smell)
proprioreceptors
joint position sense
polymodal receptors
to more than 1 type of stimulus
nociceptors
damage/distortion of tissues (pain)
what is a neuroreceptor?
membrane receptor protein activated by neurotransmitter
what are the 2 major classes neuroreceptors are divided into?
- ligand-gated ion channel (LGIC receptors): gabaa, nicotinic / nmda receptors
- G protein coupled (GPCRs) receptors: gabab, muscarinic / adrenergic receptors
what are the 2 inhibitory neurotransmitters and their receptors for ligand gated ion channels?
GABA - GABAA
glycine - alpha1, alpha2, alpha3, alpha4 and beta
kinase-linked receptors
transmembrane receptors
- uses second messenger singling -> triggers cascade
ligands bind to binding site at extracellular domain
- causes phosphorylation of AA (mainly tyrosine in intracellular domain)
e.g. cytokine receptors, epidermal growth factor (EGF), platelet-derived growth factor (PDGF) + fibroblast growth factor (FGF)
nuclear receptors
in nuclear of cells
activated when ligand mol enter nuclear membrane + bind
e.g. estradiol, progesterone, testosterone, cortisol, aldosterol + thyroid hormone
what does a synapse consist of?
- presynaptic ending
- postsynaptic ending
- synaptic cleft
presynaptic ending
contains neurotransmitters, mitochondria + other cell organelles
postsynaptic ending
contains receptor sites for neurotransmitters
synaptic cleft
space between presynaptic + postsynaptic endings (about 20nm wide)
presynaptic
situated/occurring proximal to synapse
postsynaptic
situated/occurring after synapse
where are neurotransmitter receptors present?
plasma membrane of postsynaptic cells (sometimes in pre-sn)
what are neurotransmitter receptors?
- integral membrane glycoproteins
- pharmacological compounds bind to receptor + reproduce (agonists) / block (antagonist) action of neurotransmitter
what is a ligand?
substance that forms complex with biomolecule to serve biological purpose
in protein-ligand binding: ligand = mol which produces signal by binding to site on target protein
what is a pro-drug?
chemical compound that undergoes chem conversion by metabolic processes before = pharmacological agent
what is diamorphine?
pro-drug
when enters brain, converted into morphine which binds to mu (mew) opioid receptors
what is an agonist?
neurotransmitter/drug that mimics action of neurotransmitter + binds to counterpart receptor of neurotransmitter
what can an agonist produce?
excitation/inhibition of post-sn
neurotransmiter = agonist
has high affinity for own receptor
what is a partial agonist?
agonist ligand that produces lower response than full agonist after binding to same number of receptors
what can a partial agonist act as?
competitive antagonist when in presence of full agonist
what is an inverse agonist?
ligand that binds to same receptor-binding site as agonist
what do inverse agonists do?
inhibits constitutive activity
displays negative efficacy
suppresses spontaneous receptor signalling
give an example of a receptor that possesses basal activity and for which inverse agonists have been identified?
GABA receptor
what do agonists of GABA receptors do?
they create CNS relaxant effect
inverse agonists have agitation effects
what is an antagonist?
drug that has affinity for neurotransmitter receptor + prevents action of neurotransmitter to bind to its own receptor
define inhibitor?
mol that binds to enzyme and dec activity
how can neurotransmitters/drugs inhibit activity of neurones?
- hyperpolarization of neurone
- blockade of binding of neurotransmitter to own receptor
give examples of inhibitors?
- GABA, enkephalin, diazepam, morphine (agonists)
- nifedipine (antagonist)
- atenolol (beta blocker - antagonist)
what is disinhibition?
inhibition of inhibitor
