(1) Overview 1/2 Flashcards
nervous system is divided into…. (2)
central nervous system (CNS)
Peripheral nervous system (PNS)
nuclei vs ganglia
nuclei= cell bodies in CNS (similar structure & function)
ganglia= cell bodies in PNS (similar structure & function)
what makes up the CNS
brain
retina
spinal cord
what makes up the PNS?
cranial and spinal nerves
various ganglia
what are cranial nerves
emerge from brain and go to structures
theres 12
what are cranial nerves?
emerge form brain and go to spinal cord
3 main subdivisions of the brain
forebrain
cerebellum
brainstem
what is the forebrain composed of
2 massive cerebral hemispheres and diencephalon
what separates the 2 cerebral hemispheres?
(medial) longitudinal fissure
are there more neurons or glial cells in the brain??
MORE GLIAL CELLS
how many neurons in the brain
100 billion neurons
how many glial cells in the brain
1 trillion glial cells in brain/spinal cord and PNS
what are neurons
information processing and signalling elements
used to convey information (electrical signals)
3 major components of a neuron
1) cell body/soma
2) dendrites
3) axon
function of cell body/soma?
supports metabolic and synthetic needs of neuron
function of dendrites?
RECEIVE information
- they are tapering processes
function of axons?
conducts information AWAY from cell body
- long, cylindrical processes
what are sensory neurons
either directly sensitive to various stimuli, or receive direction connections from non-neuronal receptor cells
where do motor neurons end?
directly on muscles, glands or other neurons in PNS ganglia
where are the processes of interneurons
processes confined to single small area in CNS
what are projecting neurons
have long axons connecting different areas
who is Ramon Cajal?
Father of Modern Neuroscience
- neurons are individual elements
- described functional circuits
- pyramidal cell from layer 3 impregnanted with Golgi method
- small number of cells get stained, able to differentiate structure led to identification of different cell types
what is Cajal famous for?
Golgi Technique & Silver stain
what are synapses
location where neurons COMMUNICATE with each other
- input= dendrite
- output= axon
what is neuroanatomy?
describes connections between neurons that lead to pathways and circuits that subserve specific functions
3 types of neuroglial cells
1) Macroglia
2) microglia
3) ependymal cells
3 types of MACROGLIA
1- astrocytes
2- oligodendrocyte
3- Schwann Cell
2 types of astrocytes and associated with?
protoplasmic= associated with neuron CELL BODIES (gray matter)
fibrous= associated with dendrites and axons, processes of neurons (white matter)
function of astrocytes
- regulate exchange of molecules
- contributes to BBB
- regulate blood flow
- contribute to structural integrity of nervous tissue (structural support)
- sense/monitor neural activity
what happens if increase Ca in astrocyte?
increase diameter of arteries (VASODILATION)
- because astrocytes have processes onto them
how do astrocytes maintain composition of ECF?
have ability to clear away neurotransmitters released
are astrocytes in the CNS or PNS?
CNS
are oligodendrocytes in CNS or PNS?
CNS
structure of oligodendrocytes
- larger axons
- thicker myelin
- longer internodes
what do oligodendrocytes do?
myelin- producing cells
where do you find oligodendrocytes?
mostly in white matter
some in grey matter
are Schwann cells in CNS or PNS?
PNS
function of Schwann cells
- myelin forms electrical insulation around axons, allowing electrical signal generated in cell body to rapidly reach axon terminal
- role of processes= provide metabolic support and electrical insulation
what is myelin
lipid wrapping around axons of neuronal processes
benefit of insulation (myelin)
reduces/prevents leakage of electrical currents
allows signal to go long distances
special feature of Schwann cells
Nodes of Ranvier (gaps in myelin)
purpose of nodes of ranvier
permit regeneration of electrical signals passing down axon (with myelin signal degrades)
- contain high density voltage-gated Na channels
are microglia in CNS or PNS?
CNS
role of Microglia
phagocytic role
respond to CNS injury
what does microglia do when damage occurs?
become active and proliferate, reproduce and migrate from one region to another
- clear damage, protect structures, allow recovery
where are Ependymal cells found?
line walls of ventricular system
hollow cavities in brain that contain CSF
3 characteristics of grey matter
darker
less myelin
rich in cell bodies
2 characteristics of white matter
paler colour
rick in processes (mostly axons, some dendrites)
- axons have myelin sheath that is mostly lipid (white appearance)
afferent vs efferent
afferent= sensory
efferent= motor
2 divisions of the peripheral nervous system
somatic
visceral/motor
where is the somatic NS located
in outer tube of body
- skin, muscles on outside, joints, bones (etc)
afferent component of somatic NS
sensory= conscious or unconscious
- sensation from skin: pain, temperature, touch
- muscle and joint position: proprioception
efferent component of somatic NS
motor= conscious or unconscious
- innervation of skeletal muscle (conscious or unconscious— reflex)
where is the visceral NS located
inner tube of body
- blood vessels, gut, digestive system, glands, arteries (etc)
afferent component of visceral NS
sensory= usually unconscious
- monitoring status of internal organs (heart, lungs, digestive tract, etc.)
efferent component of visceral NS
motor= unconscious
- innervation smooth muscle (gut, arteries) and glands (salivary, tear)
purpose of convolutions on cerebrum and cerebellum
to increase surface area
2 types of convolutions on cerebrum
gyri= mountains (bumps)
sulci= valleys (grooves)
2 types of convolutions on cerebellum
folia= mountains (bumps)
fissures= valleys (grooves)
6 lobes of the cerebral hemispheres
frontal parietal temporal occipital limbic insula
function of central sulcus
separates frontal and parietal lobe
aka sulcus of Rolando
function of lateral sulcus
separates frontal/parietal lobe from temporal lobe
3 components of brainstem
midbrain
pons
medulla
function of corpus callosum
white matter
connects cerebral hemispheres
corpus callosum is divided into 3 parts
R= rostrum G= genus S= splenium
diencephalon consists of…. 3 things
thalamus
hypothalamus (below thalamus)
epithalamus (pineal gland)= above thalamus
2 arterial blood supplies to the brain
internal carotids
vertebral arteries
what are internal carotids
principal source of blood to the brain
what are vertebral arteries
blood supply to brain
passes along vertebral column, enters skull posteriorly
come together on surface of brainstem to form singular midline artery= basilar artery
how many vessels from heart to brain
4 in total
what does the external carotid artery supply?
blood to the face
what is the circle of willis
aka cerebral arterial circle
connects arteries together
what 3 arteries emerge from the circle of willis
posterior, middle and anterior cerebral artery
which artery is primarily affected is someone has a stroke affecting the brain?
middle cerebral artery
