Nervous system Flashcards
function of astrocyte?
regulate extracellular composition of brain fluid via BLOOD BRAIN BARRIER
form a support framework for the CNS
what are nissl bodies?
cluster of ribosomes and rough ER within nerve cell body cytoplasm
function of oligodendrocyte?
production of myelin
function of myelin?
insulates nerve fibre from surrounding extracellular fluid, speeds up action potential conduction
function of Microglial cell
phagacytic cells that remove dead nervous tissue, micro-organisms and other foreign material
which neuroglial cell would you expect to be most common in grey matter?
astrocytes
why is there so little myelin present in grey matter?
as myelin is not present near cell bodies and grey matter is full of nerve cell bodies
where are ependymal cells located?
edge of CNS tissue,
lining the ventricles of the brain and central canal of the spinal cord
function of ependymal cells
ependymal cells (+ blood vessels) form the choroid plexuses within the ventricles of the brain...this secretes cerebrospinal fluid the free surface of ependymal cells has patches of cilia that help move fluid around the brain and spinal cord
what are the sulcus?
grooves(vallys) of the surface of the brain
what are gyrus?
hills or folds of the cortext of cerebellum/cerebrum
what is the function of the precentral gyrus?
primary motor area - controls voluntary movements
function of post central gyrus?
primary sensory - conscious perception, localisation and identification of stimulus
function of occipital lobe?
vision!
function of the thalamus?
considered the sensory relay station of the brain.
auditory, visual, sensory input eg. pain, temp, touch all pass through thalamus
function of hypothalamus?
1) autonomic nervous system eg. heart rate
2) endocrine system(hormones -> pituitary gland eg. metabolism
3) limbic system - rage, fear, sexual feelings
4) basic body functions eg. body temp control
what vertebra marks the inferior end of the spinal cord?
T12 - L1
how do we check for an infection in the brain?
lumbar puncture
where is the needle in a lumbar puncture inserted?
the subarachnoid space at either T3-T4 or T4-T5
why are cervical and lumbar parts of the spinal cord enlarged?
more nerves exit spinal cord at these regions to supply arms and legs respectively
what is the meninges?
protective layers of tissue surrounding the brain and spinal cord
name the meninges from the outer most to the inner most
dura mater
arachnoid mater
pia mater
what is the function of the dura mater?
tough, thick, outer layer of meninges
made of dense irregular connective tissue protects the CNS tissue
function of the arachnoid mater
very thin, spider like, that connects to pia mater
space contains cerebrospinal fluid which protects and cusions the CNS + provides nutrients
why is dura mater white in colour?
as its dense irregular connective tissue, hence containing a lot of COLLAGEN
what is the space called between the dura and skull/vertebral bones?
epidural space!
what is normally located in the epidural space?
adipose tissue, blood vessels and nerves
describe movement of CSF:
flows from lateral ventricle -> 3rd ventricle -> 4th ventricle
then exits ventricle and enters subarachnoid & central canal of spinal cord. flows up & down vertebral column then resorbed in arachnoid villi
what makes CSF circulate
itself…driven by its own pressure + rhythmic pulsations of the brain produced by heart beating
where is CSF formed?
choroid plexus of each lateral ventricle
how can you tell which side of spine is dorsal and ventral?
presence of dorsal grey horn and ventral median fissure
where is grey matter located in the brain?
edge of cerebrum/cerebellum?
what are ganglia?
cell bodies of neurons in the PNS
where is grey matter located in the spinal cord
it forms a H/butterfly in the centre of spinal cord
where are the cell bodies of motor neurons of the PNS located?
within the grey matter of the spinal cord
name the protective layers of a peripheral spinal nerve from outer most to inner most
epineurium, perineurium, endoneurium
describe refractory period:
period of depolarisation of the neuron during which it cannot respond to a second stimulus
describe depolarisation:
state in which the resting potential is reversed as sodium ions rush into the neuron
describe polarised:
electronic condition of the plasma membrane of a resting neuron
describe repolarisation:
period in which potassium ions diffuse out of the neuron
describe action potential:
transmission of the depolarisation wave along the neurons membrane(axon)
describe potassium ions:
chief positive intracellular ion in a resting potential
describe sodium-potassium pump
process by which ATP is used to move sodium ions out of the cell and potassium ions back into the cell; completely restores the resting conditions of the neutron
describe the events that occur at a chemical synapse between 2 neurons
1) neurotransmitters diffuse from presynapic terminal across the synaptic cleft (2) calcium ions diffuse into the cell and cause synaptic vesicles to release neurotransmitters (3) neurotransmitters combine with their receptor sites and cause ligand-gated ion channels to open. Ions diffuse into/out of the cell and cause a change in membrane potential. (4) action potentials arriving at the presynaptic terminal cause voltage-gated Ca2+ channels to open
name the parts of the neuron that can conduct and action potential
axon and just before the synaptic terminals
composition of corpus callosum:
primarily composed of over 200 million axons, called commissural fibres
function of corpus callosum?
axons(commissural fibres) interconnect allowing communication between left & right cerebral hemispheres
transfer of motor, sensory and cognitive info between hemispheres
components of brain stem:
midbrain
pons
medulla oblogata
function of axon
conduction of action potential away from cell body
function of dendrites
receive synaptic input from other cells or sensory stimuli that generate local electrical responses (graded potential) that conducts towards cell body
what do nodes of ranvier allow?
propagation of action potential in myelinated neurons
or SALTATORY conduction - allowing potential to jump from one node to another making it much faster
function of grey matter
site of synapse formation
Integration of sensory inputs and neuronal computation
site of integration of sensory inputs and neuronal computation
grey matter
function of white matter?
site of axons and tracts of neurons that link different parts of the CNS
why is white matter white?
myelin
function of microglia
act as macrophages in the brain and spinal cord
main form of active immune defense in the CNS
function of Astroglia
- biochemical support of ependymal cells
- provision of nutrients to neurons
- maintenance of extracellular ions
- repair
define continuous propagaion:
entire axon contains voltage gated ion channels, action potential gradually conducts along the length
define saltatory propagation:
voltage gated channels only at nodes of ranvier so action potential is regenerated at each node by current conducting axially (along the length), fast!
what tissues react during reflexes?
muscles or glands
what does the typical reflex involving muscle require?
sensory receptor(in muscle) sensory neuron(receptor to spinal cord) integrating centre(within spinal cord, determines magnitude of respons motor neuron(motor neuron to skeletal muscle)
what does the term monosynaptic reflex ARC mean?
| sensory neuron synapses directly with motor neuron in the grey matter of spinal cord (no interneuron)
mono = one | synaptic = synapse |
what type reflex is the platella reflex an example of?
postural reflex
so what movement of the arm does the bowler in cricket do?
circumduction
describe location of nuclei in skeletal muscle?
they’re peripherally located
what is the synaptic delay?
time between arrival of action potential at axon terminal and action at synapse
describe what happens after neurotransmitter release?
binds to receptors on post-synaptic
destroyed by enzymes (prevents neurons becoming too excited)
reuptake by presynaptic terminal - recycling
diffuse away(move away from synapse)
reuptake into glia eg. astrocytes
types of neurotransmitters
ionotropic - directly bind to and open ion channels
metabotropic - act via second messengers
what do the names of neurotransmitters end in?
“ine”
what is serotonin?
“feel good” moon neurotransmitters
90% in intestine
lower levels of serotonin are found in patients with depression
what happens with the parasympathetic activity?
Salivation
Lacrimation (tears)
Urination
Defecation
rest and digest
cut the brain in left and right sides
sagittal
cuts the brain in top and bottom
axial
horizontal
cuts brain in front and back
coronal
left hemisphere
spoken written language
numeric and scientific skills
reasoning
ability to use sign language
right hemisphere
"Creative side" musical and artistic awareness spatial and pattern awareness recognition of faces emotional content of language
what matter is the cortex made of?
grey matter!
primary function of motor cortex
Maps out/plans behaviours leading to skeletal muscle contraction
primary function of sensory cortex
Interprets incoming information
Makes information identifiable and useful
What is the main function of the basal ganglia?
Voluntary motor control habits Eye movements Cognitive functions Emotional functions
state the sequence of events in an action potential:
resting threshold -50mv reached depolarisation repolarisation hyperopolarisation resting
state the activity of gates during resting of an action potential
Na+/K+ ATpase
Na+ gated channels closed
state the activity of gates during threshold
Na+ gated channels open
state the activity of gates during depolarisation
Na+ channels open
state the activity of gates during repolarisation
Na+ gated channels close
K+ gated channels open
state the activity of gates during hyperopolarisation
Na+/K+ ATpase active
what is the action potential threshold?
-50mv
what stimulates vesicles to fuse with membrane?
Ca2+
action potential triggers influx of Ca2+
what is exocytosis?
release of contents from cell into the extracellular space, in this case it is released into synapse
what does the binding of neurotransmitters to receptors on post-synaptic neuron do?
stimulate post-synaptic potential
change in membrane potential
what is graded potential?
summation of individual actions of the ligand-gated ion channel proteins
why are neurotrasmitters reabsorbed?
saves energy as pre-synaptic cell doesn’t need to make new neurotransmitters from scratch
why are some neurotransmitters pumped back into glia?
to avoid overstimulation of the post-synaptic neuron
what is electrical synapse?
direct neural connection through gap junctions
3 groups of neurotransmitters
amino acids
classical neurotransmitters
neuropeptides
how do anti-depressant drugs work at serotonin synapses
Selective Seretonin Reuptake Inhibitors, inhibit the reuptake of serotonin at the synapse, continues to stimulate post-synaptic cell, prolongs effect
why is too much Glutamate bad for the brain?
overestimates the brain and spinal cord -> seizures
excitotoxcity -> cell death
what are the 2 main second messengers?
Cyclic AMP
Inositiol triophosphate
briefly describe how second messager cyclic AMP (cAMP) works to transmit signal in post-synaptic cell
activates membrane potential G PROTEIN
ATD -> cAMP
impacts membrane permeability, metabolic pathways, protein synthesis
briefly describe second messenger Inositol Triphosphate
activates G PROTEIN and PHOSPHOIL[pase
IP3 -> diacylglycerol (DAG)
what is an IPSP
inhibitory post-synaptic potential
synaptic potential that makes post synaptic neuron LESS likely to generate and action potential
what is an EPSP
excitatory post synaptic potential
MORE likely to generate an action potential in post synaptic neuron
ESPS’s summate when there are enough synapses close together
when there is enough synapses close together what is it called?
spatial summation
what happens with EPSP’s when post synaptic membrane is depolarised in rapid succession?
EPSP’s provide temporal summation
what is contained in the brain stem
midbrain, pons, medulla
what region of the brain is responsible for maintenance of body temperature
hypothalamus
what part of part of the brain contributes to coordination, precision and accurate timing?
cerebellum
function of pons?
basically to replay signals from forebrain to cerebellum
what do the signals that pass through pons control?
respiration, sleep, swallowing, bladder control, hearing, taste, facial exression/sensation
why is the medulla so important?
controls cardiac(heart rate)
respiratory centers(breathing)
Vasomotor (blood pressure)
vomiting
what does the medulla contain?
nuclei concerned with Vital Visceral functions
what dural fold separates left and right hemispheres
falx cerebri
what dural fold separates left and right lobes of the cerebellum?
falx cerebelli
what dural fold separates the cerebral hemispheres from the cerebellum?
tentorium cerebelli
whats the little pocket of fluid below protective layers of the skull
superior sagittal sinus
where is CSF reabsorbed?
arachnoid villi (finger like projections of arachnoid membrane that project fluid into superior sagittal sinus)
