Lecture 8-10: Central Nervous System Flashcards
fxn of NS
maintain homeostasis (along with endocrine system)
which is faster, endocrine or nervous? more widespread?
longer lasting effect?
nervous sytem=faster
widespread and long-lasting effect: endocrine
components of
NS
CNS=brain, spinal cord
PNS= cranial nerves, spinal nerves, peripheral ganglia
define ganglia
group of nerve cell bodies which reside outside CNS
nucleus
group of nerve cell bodies which reside inside CNS
fxn of CNS vs PNS
PNS: collecting sensory info from body & distribute motor response
CNS:Process that information, initiate motor repsonse to sensory stimulus. motor response will be distributed my PNS
possible sources of sensory info collected by PNS
somatic senses=touch,temp,pain (i.e. skin)
visceral senses= VAGUE sense. info from internal organs. doesn’t reach concious level mostly (i.e. BP from blood vessel)
special senses=vision,smell,hearing
Divisions of Motor Output PNS
Somatic Nerves: target skeletal muscle
Autonomic division
1) Sympathetic (smooth muscle, cardiac muscle, glands)
2) Parasympathetic (smooth muscle, cardiac muscle, glands)
3) Enteric plexus (smooth muscle and glands of digestive canal)
when do u start to develop NS
end of week 3 gestation. hollow straiht tube (neural tube) develops
what are the three primary cerebral vesicles that are first to develop at week 3/4
- prosencephalon
- mesencephalon
3.rhombencephalon
what happens at week 5
primary vesicles subdivide into secondary cerebral vesicles
prosencephalon ==> Telencephalon & DIencephalon
Mesencephalon
Rhomebencephalon = Metencephalon & Myencephalon
what do the 5 secondary cerebral vesiscles give rise to
- Prosencephalon
- Mesencephalon
- Rhombencephalon
green part to become spinal cord
- Telencephalon
- Diencephalon
MESENcephalon - Metencephalon
- Myelencephalon
whats what
left=cerebellum
right=pons
midbrain
diencephalon
cerebrum
medulla oblongata
length of spinal cord
43-45 cm
where is spinal cord enlarged
- cervical enlargment- nerves to upper limbs
- lumber enlargment- nerves target lower limbs
more nervous tissue here
Conus Medularis
reverse cone shaped part at distal end of spinal cord
where does spinal cord start/end
start: CI
End: intervertebral disc btw LI-LII
two types of nervous tissue
- gray matter: nerve cell bodies
- white: myelinated nerve fibres
gray matter in spinal cord
at the core.
white matter in spinal cord
surrounds gray matter
Horns of spinal cord
Anterior horn: MOTOR neurons
Posterior horn: SENSORY neurons
Lateral horn: not present throughout length of spinal cord, only certain segments. Present btw TI to LII segments [sympathetic neurons & SII and SIV [parasympathetic neurons]
where is lateral horn
btw tI and LII [sympathetic]
SII and SIV [parasympathetic]
Columns of spinal cord
=bundles of white matter = tracts
- Anterior column
- Posterior column
- Lateral column
columns are mixed btw sensory and motor but INDIVIDUAL TRACTS cannot contain both
ventral root
axon of MOTOR NEURON which reside in anterior root
Dorsal Root
carries nerve fibres which are arising from sensory neuron, come together very close to spinal cord. form cluster outside spinal cord (DRG)
dorsal root carries sensory fibre
how many spinal nerves are there
31 pairs. each spinal nerve is MIXED (both sensory and motor fibres)
ascending vs descending pathway
ascending= sensory
descending = motor
Typical sensory pathway
First order neuron in DRG
Second order neuron either in posterior horn of spinal cord OR brainstem. Decussates e
Third order nucleus in thalamus
Medial Lemniscal/dorsal column
Collects proprioception and fine touch. SENSORY pathway
Spinothalamic pathway
SENSORY pathway
picks up pain, temp, crude touch.
First order in DRG
Second in posterior horn, decussates
ascend contralaterally to medulla
typical motor pathway
Upper MN: in cortex. sends axon to brainstem. Decussation always done by UMN. either in Brainstem, or in spinal cord
Lower MN in spinal cord (anterior horn)
anterior corticospinal pathway
sits in anterior column of spinal cord
Upper MN decussates in medulla
targest muscles of core
lateral corticospinal pathway
in lateral column of spinal cord
targets limbs
upper MN decussates in medulla
label these brainstem structures
- Midbrain
- Pons
- Medulla Oblongato
- Spinal cord
4th cerebral ventricle
label A,B,C
A: CNVIII Nuclei: Sensory nerve
B:CNX Nucleus: Parasympathetic nucleus
C: CNXII nucleus: Motor nerve (supplies muscles of tongue)
within brainstem, motor nuclei are closest to midline. sensory are quite lateral, PSN nuclei are in btw
how is gray matter organized in brainstem?
no longer in horns. divided into smaller pieces = nuclei. majority associated with cranial nerves
note: ALL motor/sensory pathways are present in brainstem
reticular forrmation
controls alertness
connects everything, receives all senses, projects everywhere
controls visceral reflexes
inferior olivary nucleus
enables you to learn new motor skills
A= medial leminiscus (sensory pathway)
B= corticospinal tract (motor)
A=mibrain
B=pons
C=medulla oblongata
A= superior (controls visual reflexes) and inferior (controls auditory reflexes) colliculi
B=4th cerebral ventricle
C=Cerebellar peduncles. connecting points btw cerebellum and brain stem on either side of ventricle
D=Cranial Nerves
structure? function?
red nucleus. cooperates with cerebellum for coordination of fine movement
damage= intentional tremors
structure? function?
coordinatino of gross movements. lesion=PD (shufling gait)
strucuter? function?
reticular formation. role in being awake, visceral things. found throughought midbrain
cerebral aquaduct. upward continuation of 4th ventricle
superior colliculus
CNIII nucleus= motor nucleus.
cerebral peduncle. contains all motor pathways
what divides the anterior and posterior cerebellum
primary fissure
what separetes RH and LH of cerebellum
Vermis
folia
folding
differences btw fissure and sulcus
fissure is deeper
most important functino of cerebellum
maintain ballance.
A: anterior lobe
B: primary fissure
C: cerebellar cortex
A: arbor vitae (white matter)
B: posterior lobe
C: 4th cerebral ventricle
Cerebellar peduncles
3 pairs of myelinated fibres
1. Superior Cerebellar Peduncle: connects to midbrain
2> Middle Cerebellar Peduncle: connects to pons
3. Inferior Cerebellar Peduncle: connects to medulla
where is third ventricle
btw two hemispheres. Diencephalon surrounds it
main structures of diencephalon
thalamus: sensory relay
hypothalamus: regulate endocrine, ANS
Pineal: produce melatonin, circadian rhtym, sex
gyrus
= holds
separated by sulci
Frontal lobe
motor centre
personality, judgement, planning, decision
Occipital lobe
visual
temporal lobe
sensory (hearing)
parietal
general sensory (pain, temp, touch)
3 main sulci:
Central: separates frontal and prietal
lateral: separates temporal and frontal
Parietal occipital: btw paretal and occipital
Basal Ganglia made up of?
- Caudate Nucleus
- Lentiform Nucleus (Putamen, Globus Pallidus)
Caudate Nucleus
A: Putamen
B: Globus Pallidus
Together = lentiform nucleus
fxn basal ganglia
coordinate gross movement, initiate/stop thoughts
association fibres
connect gyri of same hemisphere
commissural fibres
connect same structure in diff hemispheres (i.e. corpus callosum)
projection fibres
connect cerebrum to lower centres (i.e. internal capsule)
lateral ventricle anterior horn
inter-ventricular forament
posterior horn
left= cerebral aquaduct
right = fourth ventricle
top = third ventricle
bottom = inferior horn
How much CSF is produced each day?
500 mL
only 150 mL in body at once, replaced 3x a day
what are the layers of meninges
Dura mater (tough, thick, external fibrous layer)
Arachnoid matter (thin intermediate_
Pia mater (delicate internal vascular)
how is pia and arachnoid mater separated
subarachnoid space, which contains CSF
how is CSF formed
by the choroid plexus within the 4 ventricles
what are the layers of dura mater
peiosteal layer (external)
meningeal layer
dural infoldings
The internal meningeal layer of the dura reflects away
from the external periosteal layer of the dura to form
dural infoldings (reflections), which divide the cranial
cavity into compartment
The four dural infoldings are the falx cerebri, tentorium cerebelli, falx cerebelli, and diaphragma
sellae.
superior and inferior sagittal sinus
between the periosteal and meningeal layers of the dura dura. large irregular veins. carry venous blood. superior is one of the largest sinuses in cranial cavity, it is attached to the falx cerebri
explain pathway of CSF from lateral ventricle into the circulatory system
Lateral ventricles produce CSF
travels via interventricular foramen to third ventricle
CSF flows from there into 4th through cerebral aqueduct
More CSF added here,
Median aperture: midline of fourth ventricles. One opening where CSF can escape
After exiting through median aperture, CSF enters subarachnoid space.
Arachnoid villus: finger like projections into subarachnoid space. Act as unidirectional bows. Allow CSF to drain into sinuses
arachnoid villus/granulation
top=median aperture (midline of 4th ventricle. one opening where CSF can escape)
bottom= subarachnoid space
top= interventricular foramen (connects third to lateral)
mid: third ventricle
bottom; cerebral aqueduct
top= superior sagital sinus
bot= lateral ventricle
label A-D
A: Subarachnoid Space
B:skin
C: superior sagittal sinus
D: arachnoid villus
label E-H
E: periosteal
F: meningeal
G: Arachnoid Mater
H: Pia Mater
where does spinal cord end
vertebrae LI-LII
lumbar cistern
the subarachnoid space in the lower lumbar spinal canal.
space btw end of spinal cort LI-LII) and vertebra SII. contains roots spinal nerves and CSF
The bundle of spinal nerve roots in
the lumbar cistern of the subarachnoid space caudal to
the termination of the spinal cord resembles a horse’s tail,
hence its name cauda equina
cauda equina
bundle of ventral and dorsal roots of the lumbar, sacral, coccygeal spinal nerves
dermatome
area of skin innervated by single spinal nerve/spinal cord segment
myotome
part of skeletal muscle innervated by a single spinal nerve/cord segment
how are spinal nerves named
after spinal cord segments
- C1-C8
- T1-T12
- L1-L5
- S1-S5
5.Co (pair of nerves)
