Week 2 Lecture Flashcards
dendrites
processes that often make synaptic contacts with neighboring neurons to receive information at small protrusions called dendritic spines
neural plasticity
configuration of synapses on dendrites and cell body is constantly changing
what do dendritic spines do?
increase surface area for synapses
types of dendritic spines
- stubby
- filopodia
- thin
- mushroom
stubby and filopodia dendritic spines main characteristic
believed to be the precursor of other spines
- filipodia spines are > 2 um
- stubby spines are < 1um
thin dendritic spine main characteristics
- appear and disappear in a few days
- flexible structure, making them “learning spines”
- 1 um - 2 um
mushroom dendritic spines main characteristics
- more stable and can last for months
- contain more AMPA receptors
- the “memory” spine
- pronounced head and neck, 1 um - 2 um
common components of a neuron
soma, axon initial segment/axon hillock, myelin sheath, nodes of ranvier
soma
cell body (part of the gray matter in the CNS)
- contains the important cellular components to help keep the neuron alive (nucleus/DNA, ribosomes, etc.)
axon initial segment/axon hillock
the section of the neuron where there is a dense concentration of sodium channels to facilitate threshold responding - the decision making area of the neuron
myelin sheath
conductive and insulative material that normally covers the axons to increase the effectiveness and efficiency of cellular transmissions
- covers leak channels and prevents ions from leaking out
nodes of Ranvier
breaks between bundles of myelin (un-myelinated segments) with a dense concentration of sodium and potassium channels
- site of saltatory conduction
what causes multiple sclerosis
the immune system attacks the protective sheath (myelin) that covers nerve fibers and causes communication problems between your brain and the rest of your body
components of input zone
dendrites, dendritic spines, soma
main component of the integration zone
axon initial segment/axon hillock - decision making location
main components of conduction zone
axon, myelin sheath, nodes of Ranvier
main component of output zone
axon terminals - chemical transmission of message
input zone
where neurons collect and process information, either from the environment or from other cells
integration zone
where the decision to produce a neural signal is made
conduction zone
where information can be electrically transmitted over great distances
output zone
where the neuron transfers information to other cells
nuclei
where neurons synapse with other neurons
what are a group of myelinated axons called?
fibers, tracts, columns, funiculi, fascicles, capsules, peduncles
nucleus/nuclei or ganglia
a group or cluster of neuron cell bodies
gray matter
location of neuron cell bodies
white matter
location of myelinated axons
the dendrites and cell body are the ______ zone of the neuron, while the axon terminal boutons are the ______ zone
input; output
characteristics of an action potential
- originate in the axon hillock
- propagate at a high speed along the axon
- greater stimulus = greater response (graded response)
what do local potentials do
serve as the initial signals that can either initiate or inhibit the generation of action potentials
when is an action potential fired?
when the sum total of all the excitatory and inhibitory input on the neuron raises the membrane voltage at the hillock above the threshold for firing
why does an action potential only travel in one direction
the membrane segment behind it is refractory (not yet back to the resting state)
- it can propagate down the length of the axon without diminishing in strength because it is an all or nothing signal
types of synapses
axo-dendritic, axo-somatic, axo-axonic, and dendro-dendritic
axo-dendritic synapse
the axon terminal synapses on a dendrite
axo-somatic synapse
synapse between axon and cell body (soma)
axo-axonic synapse
synapse between two axons
- does not result in action potential
dendro-dendritic synapse
synapse between two dendrites
electrical synapses
potential jumps directly to the postsynaptic region without using chemicals
are neural messages soup or sparks?
soup
what happens when the action potential reaches the axon terminal?
the neuron releases neurotransmitters
what are neurotransmitters
chemical messengers that are sent from the presynaptic neuron to the postsynaptic neuron
what series of events is required for synaptic transmission?
- action potential arrives at axon terminal
- voltage-gated calcium channels open and Ca2+ ions enter
- synaptic vesicles fuse with membrane and release transmitter into the cleft
- transmitter crosses the cleft and binds to postsynaptic receptors, which opens ion channels
what do SNAREs and synaptotagmin do
mediate exocytosis
three general types of neurons (regarding types of axon)
multipolar neurons, pseudo-unipolar neurons, bipolar neurons
multipolar neuron characteristic
one axon, many dendrites
pseudo-unipolar neuron characteristic
- born from bipolar neurons
- 2 processes that extend from a single point from the cell body
- send touch info from the body to the spinal cord
bipolar neuron characteristics
- sensory neurons found in olfactory epithelium, the retina of the eye, and ganglia of the vestbulocochlear nerve
- 2 processes (1 dendritic process and 1 axon)
sensory - afferent neurons purpose
carry information from peripheral nervous systems and sensory receptors to the CNS
afferent meaning
carrying information from PNS to CNS, often paired with sensory neurons
motor - efferent neurons purpose
carry information from the CNS to the motor organs (muscles)
efferent meaning
carrying information from the CNS to PNS, often paired with “motor” neurons
interneurons (relay and local) purpose
relay interneurons have long axons to project to far away targets; local interneurons stay local w/ short axons
are all interneurons inhibitory?
not all
where are interneurons found, and what do they transmit ?
CNS; can transmit motor and sensory information
cholinergic neuron function
motor control, memory, attention, and autonomic functions (acetylcholine)
cholinergic neuron location
neuromuscular junction, basal forebrain, and brainstem
dopaminergic neuron function
reward, motivation, motor control, and regulation of mood
dopaminergic neuron location
substantia nigra, ventral tegmental are (VTA)
GABAergic neuron function
the primary inhibitory neurotransmitter in the CNS, important for reducing neuronal excitability and regulating muscle tone
glutamatergic neurons function
primary excitatory neurotransmitter in the CNS, crucial for synaptic plasticity, learning, and memory
seratonergic neurons function
mood regulation, appetite, sleep, and cognitive function
seratonergic neuron location
raphe nuclei of the brainstem
three CNS neuronal cell types
excitatory, inhibitory, modulatory
excitatory neuron function
stimulate excitation in their target neurons
inhibitory neuron function
neurons that evoke inhibition in their targets
modulatory neuron function
evoke more complex effects on their target neurons
astrocyte function
mechanical and metabolic support for neurons; form a barrier along capillaries (blood brain barrier)
- contain sucker-like extensions that contact blood vessels
what do astrocytes release?
gliatransmitters
what do gliotransmitters do
modulate neuron function
what are the gliotransmitters released by astrocytes?
glutamate, taurine, and ATP
how do astrocyte signals control flow of oxygen and nutrients?
through connections called “end feet” that expand or narrow blood vessels
microglia
immune cell, protective, clean-up debris
ependymal cells
form the inner lining of ventricles, facilitate production of CSF
satellite cells
protect neurons and ganglia in the PNS
- in sensory, parasympathetic, and sympathetic neuron ganglia in the PNS
- thin, flattened cells that surround the soma of peripheral neurons in a manner that resembles the outer covering of a soccer ball
how to tell difference between CNS and PNS glia
“S” glia are PNS, non “S” glia are CNS
function of satellite glia cells
- supply nutrients
- protective covering against physical damage
- regulate neurons ionic environment & membrane potential
- prevent somatic synapses from forming from other neurons (which are usually inhibitory on the somatic)
- alter neuro-transmission
Schwann cells
form the myelin sheath around 1 PNS axon
- creates 1 myelin segment on 1 axon
oligodendrocyte
form the myelin sheath around multiple axons (acts as an insulator) in the CNS
- produce myelin segments on 30-40 axons in CNS
saltatory conduction
electrical signal jumping from one node to another; accelerates speed of nerve impulses up to 120 m/sec
types of neuroglia
ependymal cells, oligodendrocytes, satellite cells, astrocytes, microglia, Schwann cells
four main parts of a neuron
dendrites, soma, axon, axon terminal
function of meninges
protection, CSF circulation, blood supply
how do the meninges protect the brain
providing a barrier against physical impacts and infections
three protective membranes
dura mater, arachnoid, pia mater
layers of dura mater
periosteal layer, meningeal layer
periosteal layer
the outer layer of dura mater, which is attached to the inner surface of the skull
- serves as the periosteum (a membrane covering bones) of the cranial bones
meningeal layer
the inner layer, which lies closer to the brain
- continuous with the dura mater of the spinal cord
dural reflections
important folds that separate different parts of the brain
falx cerebri
a sickle-shaped fold that descends vertically in the longitudinal fissure, separating the two cerebral hemispheres
falx cerebelli
a small vertical fold that partially separates the two hemispheres of the cerebellum
tentorium cerebelli
a horizontal fold that separates the cerebrum from the cerebelluj
diaphragma sellae
a small, circular fold that covers the pituitary gland which allows the passage of the pituitary stalk (infundibulum) through it to connect with the hypothalamus
tentorial notch
an opening in the tentorium cerebelli which allows the brainstem to pass through
dural venous sinuses
receive blood from the brain through the cerebral veins and receive CSF from subarachnoid space; ultimately drains into the jugular veins in the neck
- don’t constrict or dilate; they are spaces
what are the paired dural sinuses
- cavernous sinus
- superior petrosal sinus
- inferior petrosal sinus
- transverse sinus
- sigmoid sinus
what are the unpaired dural sinuses
- superior sagittal sinus
- inferior sagittal sinus
- straight sinus
- occipital sinus
arachnoid layer
middle layer of the meninges and part of the leptomeninges
- attached to the inside of the dura mater and surrounds the brain and spinal cord but doesn’t line the brain down into its sulci
- CSF flows underneath in the subarachnoid space full of delicate fibers that attach to pia mater
arachnoid mater structures
arachnoid trebecula, arachnoid cisterns, and arachnoid villi/granulations
arachnoid tebeculae
strands of connective tissue that loosely connect the arachnoid and pia mater
- CSF flows around them within the subarachnoid space that they create
arachnoid villi
small protrusions of the arachnoid mater into the dural venous sinuses of the brain that allow CSF to exit the subarachnoid space and enter the blood stream
arachnoid granulations
aggregations of arachnoid villi
subarachnoid cistern function
small cavities in the space between the arachnoid and pia mater
- filled with pools of cerebrospinal fluid; provide buoyancy
subarachnoid cisterns names
- suprasellar (chiasmatic) cistern
- interpenduncular cistern
- pontine cistern
- quadrieminal cistern
- supracerebellar cistern
- cisterna magna (largest)
pia mater
delicate innermost membrane enveloping the brain and spinal cord that is adherent to the brain tissue surface and follows the contours of the brain including the sulci and gyri
- impermeable to fluid which allows it to enclose and contain CSF between it and the meningeal layer to protect and cushion the brain
- blood vessels run through the pia material to enter the brain
ventricular system
a set of 4 interconnected cavities (ventricles) in the brain, where the CSF is produced
what is CSF
- clear, colorless body fluid found in brain and spinal cord
- made from blood plasma
- mostly water and contains energy substrates, oxygen, vitamins, and ions
- cell and protein free
- made everywhere except cerebral aqueduct
choroid plexus anatomy
- composed of tightly linked ependymal cells that are attched to pia mater outcroppings into the ventricles
- underneath ependymal cells are blood capillaries
- blood plasma diffuses from capillaries into ependymal cells where it is converted to CSF
steps of CSF formation
- filtered form of blood plasma moves from capillaries into an interstitial space via a difference in pressure b/ween blood in capillaries and interstitial fluid
- fluid passes through ependymal cells in an active process requiring energy for the transport of Na, K, and Cl that craws water, nutrients, and O into CSF w/ osmotic pressure
- CSF returns to the vascular sytem by entering dural venous sinuses via arachnoid granulations
why are ventricular, vascular, and meninges taught together in one lecture?
they are interconnected in an important brain recycling system
what causes hydrocephalus
a blockage in the ventricular system that prevents drainage of CSF into the sinuses and results in an accumulation of CSF and high intracranial pressure which compresses brain tissue against the skull
three main types of blood vessels
arteries, capillaries, veins
arteries
blood vessels that carry oxygen-rich blood away from the heart to various parts of the body
- branch into arterioles, which divide into capillaries
capillaries
smallest and most numerous blood vessels in the body
- connect arteries and veins
veins
blood vessels that carry oxygen-depleted blood back to the heart from the body’s tissues and organs
carotid arteries
major blood vessels located on each side of the nectar
- divide into internal and external carotid arteries
vertebral arteries
paired arteries that ascend through the neck to supply blood to the brainstem, cerebellum, and posterior parts of the brain
basilar artery
the basilar artery is formed by the convergence of the two vertebral arteries at the base of the brain
cerebral arteries
once inside the skull, the carotid and vertebral arteries give rise to a network of smaller arteries known as the cerebral arteries
what are the two major systems that bring blood to the brain
common carotid and vertebral arteries
what does the common carotid divide into
external carotid, internal caroti
external carotid function
supplies the face and scalp
what does the internal carotid divide into
- middle cerebral artery
- anterior cerebral artery
- anterior choroidal artery
- posterior communicating artery
what do the vertebral arteries divide into
- posterior cerebral artery
- basilar artery
- superior cerebellar
- pontine arteries
- anterior inferior cerebellar artery
- posterior inferior cerebellar artery
what does the middle cerebral artery supply
- lateral frontal lobe
- lateral parietal lobe
- lateral occipital lobe
- lateral temporal lobe
- insula
- basal ganglia
- internal capsule
what does the anterior cerebral artery supply
- medial frontal lobe
- medial parietal lobe
- limbic lobe
- basal ganglia
- internal capsule
- corpus callosum
what does the anterior choroidal artery supply
- basal ganglia
- amygdala
- hippocampus
- internal capsule
- thalamus
what does the posterior communicating artery supply
- medial occipital lobe
- medial temporal lobe
- thalamus
what does the posterior inferior cerebellar artery supply
- cerebellum
- brainstem (medulla)
what does the anterior inferior cerebellar artery supply
- cerebellum
- brainstem (pons)
what does the basilar artery supply
brainstem (midbrain, pons)
what does the superior cerebellar artery supply
- cerebellum (superficial)
- brainstem (midbrain)
what does the posterior cerebral artery supply
- brainstem (midbrain)
- medial occipital lobe
- medial temporal lobe
- limbic lobe
- hippocampus
- corpus callosum
- thalamus
