fundamental neurobiology Flashcards
what are the two original theories for the composition of the nervous system?
. reticular theory-composed of a network of structures- (continous tubes)
. cell theory- composed of discrete cells
what is the nervous system composed of?
the nervous system is made of individual cells called neurons
what is the function of the nervous system?
the nervous system send electrical signals very rapidly throughout the body
describe the path of the reflex arc?
stimulus receptor - convert stimulus to electrical signal-transduction sensory-PNS interneurons-CNS-brain and spinal cord motor-PNS effector-muscle response
what is an example of a simple behaviour controlled by REFLEX ARC?
myotatic reflex
what is a myotatic reflex?
muscle contraction in response to stretching within the muscle
what are the 3 different types of muscle?
skeletal- attached to skeleton -striated-forceful-voluntary
cardiac-found in heart-striated-forceful-involuntary
smooth- hollow organs/glands-unstriated-involuntary
what is the afferent sensory system?
afferent neurons carry sensory signals from the body to the brain
what is the efferent motor system?
efferent neurons carry signals away from the brain
what are the two types of efferent motor system?
somatic-innervates skeletal muscle
autonomic-innervates smooth and cardiac muscle and glands
what are the two types of autonomic efferent motor system?
. sympathetic - increase respiration and decrease digestion
.parasympathetic - slows heart rate and respiration
when is the sympathetic motor system used?
during flight , fright , fight
when is the parasympathetic motor system used?
resting and digestion
how many nerves connect the CNS to the rest of the body?
.43 pairs of nerves connect the CNS to the rest of the body
.12 pairs of cranial nerves exit the brain
.31 pairs exit at various levels of the spinal cord
what are the two types of cells of the nervous system?
- neurons or nerve cells
2. supporting cells
what are neurons or nerve cells?
. found in adult PNS and CNS
.generate and transmit electrical signals
.have similar structures to most cells only difference is it conducts electricity
.10^11
what are supporting cells?
.they have supporting roles in nerve cell functions
.10^12- several different types
what do most neurons have?
.several dendrites
. a cell body (soma) that contains the nucleus
. along axon
. synaptic region(axon terminals)
what structure do neurons have?
polar structure- information comes in one end+leaves in another
how does information flow?
. information flow is usually in one end (dendrites to synapses)
what is the function of dendrites?
.receive incoming electrical information
.each cell in the body is connected to dendrite to form electrical signal.
what is the structure of dendrites?
.their branching increases surface area
.spines on dendrites increase surface area
what is axonsomatic?
incoming neurons connect to the cell body
what is axoaxonic?
incoming neurons connect to axons
what is the function of cell body (soma)?
sums electrical signals coming from dendrites
what is the structure of cell body(soma)?
contains the usual organelles including prominent nucleus and nucleolus and rough ER(known as nissl substance)
what is the function of axon?
takes electrical signals away from the body
what is the structure of axon?
.varies in length from «1mm to>1m
.usually unbranched but may have collaterals
.the axoplasm is surrounded by a phospholipid bilayer membrane embedded with proteins
.possession of a myelin sheath
.contains actin , mircrotubles and intermediate filaments
where does axon join the soma?
join soma at axon hillock (where signal is generated)
where does axon end?
ends in synaptic terminals(where it contacts other neurons)
how do substances move within axon?
movement of substances via “axonal transport” and axoplasmic flow.
what is axoplasmic flow?
anterograde transport from cell body to synapse
transport protein to maintain+repair flow
.involves intermediate filaments and is slow(1-5 mm day)
one direction
Slow
involves intermediate filaments
what is axonal transport?
.anterograde and retrograde
. mediated via microtubules and neurofilaments which are faster(400-2000mm day)
.goes both ways
fast
e.g chemical towards synapse and waste products back from synapse to cell body
where do axons terminate?
.axons terminate in a series of synapses(axon terminals)
what happens in synapses(axon terminals)
.this is where electrical signals are transferred to other neurons or muscles
. this usually occurs through release of a chemical (neurotransmitter)
.neuron has a synaptic region where neurotransmitters are released.
what is myelin?
mixture of proteins and phospholipids forming an insulating sheath around neurons
(membrane of schwann cells)
what do schwann cells produce?
they produce myelin in the PNS - myelinisation
what is the function of schwann cells?
.the schwann cell membrane repeatedly wraps itself around an axon
.a single schwann cell provides myelin for only one neuron
.a single neuron receives its myelin from several schwann cells
how are the gaps in the myelin sheath formed?
gaps in the myelin sheath are formed between the bits of myelin provided by individual schwann cells
what are the nodes of ranvier?
nodes of ranvier are where electrical signal is generated
what is the structure of small axons?
some small axons remain umyelinated and rather than being wrapped in schwann cell cytoplasm they lie in a groove on the surface of a cell
what are oligodendrocytes?
. wrap themselves around a neuron
.produce myelin in the CNS
.a single oligodendrocytes provides myelin for only several neurons
what are the neural supporting cells in the PNS?
. schwann cells- produce myelin
.satellite cells
what are the neural supporting cells in the CNS?
. oligodendrocytes
.microglia
.ependymal
.astrocytes
what is the structure of astrocytes?
. star-shaped with ‘feet’ covering blood vessels
what is the function of astrocytes?
. important for blood:brain barrier .have a role in damage repair . store nutrients(glucose) .astrocytes replicate - main source of CNS tumours .isolate synapes
what is the function of ependymal cells?
. line ventricles of brain and central canal of spinal cord
.involved in secretion of CSF
what is the function of microglia
.normally 'dormant' . involved in CNS injury/inflammation .move to damage site .phagocytose pathogens .release cytokines to attract other immune cells
what are the four basic morphological types of nerve cells?
- anaxonic
- unipolar
- bipolar
- multipolar
what are anaxonic nerve cells?
.no axon
. e.g. retinal amacrine cell
what are unipolar nerve cells?
. only one neurite emanating from the cell body
.e.g. sensory neurons
what are bipolar nerve cells?
. one dendritic process and one axon leave the cell body
. e.g. retina
what are multipolar nerve cells?
. many neurites emanating from the cell body
e.g. most CNS neurons
what is the organisation of a nerve?
dont confuse nerve for neuron
. a nerve is a collection of neurons
.contain both afferent and efferent fibres
what are neurons separated by?
a connective tissue sheath- endoneurium
what does the perinurium split nerves into?
the perinurium splits nerves into fascicles
what forms the outer coat of a nerve?
epineurium forms an outer coat
What is transduction?
receptor converts stimulus to an electrical signal.
What needs to happen to a stimulus?
needs to be converted into an electrical signal via the receptor
What is mostly the effector?
a muscle
sometimes gland
What makes up the PNS?
Sensory and motor neurones
What makes up the CNS?
Brain and spinal cord
Describe the receptor role in reflex arc
sends the electrical signal to CNS via sensory neurones.
What happens when you hit the patellar tendon with a hammer?
it stretches a muscle, which activates a muscle stretch receptor/muscle spindle and causes to send signal to sensory neurone to spinal cord to then motor neurone. e.g of myotatic reflex
Whys is the skeletal muscle striated?
due to regular arrangement of actin and myosin
powerful/fast
What is the neurone which goes to skeletal muscle?
somatic
What is the neurone which goes to cardiac muscle and smooth muscle?
autonomic (involuntary)
What are the 2 systems the autonomic system is divided into?
Sympathetic
Parasympathetic
What makes nerve cells unique?
their function; the transmission and storage of information.
What do neurones form?
networks
What does the large surface area of dendrites tell us?
that they can gather lots of information from lots of neurones coming into them.
How does the electrical signal move?
each cell connecting to a dendrite will produce an electrical signal which will be conducted along dendrite to the cell body.
What does the cell body contain?
all organelles, nucleus, golgi, lots of E.R (RESPONSIBLE FOR MAKING proteins)
What do the E.R appear as under a microscope?
nissl granules
What can the length of an axon vary till?
either 1mm or 1m long.
What is an axon surrounded by?
surrounded by regular plasma membrane
How do you get proteins to the synaptic region?
via microtubules, microfilaments and intermediate filaments - axoplasmic flow
What is anterograde?
travel from cell body to synapse
What does the synaptic region contain?
vesicles containing neurotransmitters
How much does the glial cell take?
makeup half of the bulk of the nervous system
Whats the difference between oligodendrocytes and schwann cells?
they give myelin to many neurones but schwann cells only give to one neurone
What is a nerve ?
a collection of neurones
contains both afferent and efferent fibres
an organ made up of a thousand of cells
Who is camillo golgi?
stained the CNS tissue and showed many discrete cells, different shapes and sizes
1873
Who is Ramon y cajal?
from 1888
Used Golgis stain on the CNS and PNS tissues to draw and classify the different cell types and the contacts between them
