4b: Nervous System - Brain

how many dura layers are in the brain? and spinal cord?

2 layers in the brain, 1 layer in spinal cord

which cranial meninge is the toughest layer? what are the 2 layers of this meninge called?

dura mater

periosteal (outer), meningeal (inner)

how is the dural venous sinuses formed in the brain?

from the separation of dura layers

what do the dural venous sinuses contain? where does it drain to?

collects venous blood and CSF

internal jugular veins via the arachnoid granulations

what separates the L/R hemisphere of the cerebrum? what about L/R hemispheres of cerebellum? what about separation cerebrum from cerebellum?

(meningeal layer of dura mater)

falx cerebri

falx cerebelli

tentorium cerebelli

what space holds CSF?

subarachnoid space and the 4 ventricles

what is the function of CSF?

bathes and protects the brain and spinal cord by absorbing shock

which meninge layer directly adheres to the brain and is the thinnest layer?

pia mater

what is the function of pia mater?

directly covers the brain, anchors blood vessels that supply the brain and spinal cord which prevent excessive mvmt and damage to brain

how many ventricles are there in the brain? name them

4

2 lateral ventricles (side horns), the 3rd ventricle (middle one with a hole), and 4th ventricle (triangular, superior end)

what connects the lateral ventricles to the 3rd ventricle

interventricular foramen

what connects the 3rd ventricle to the 4th ventricle

cerebral aqueduct

where does the CSF flow through after the 4th ventricle

central canal of spinal cord

what structure in the ventricles produce CSF? where can you find these structures?

the choroid plexus

there is a choroid plexus in each of the ventricles

describe the flow of CSF starting from lateral plexus until the heart/lungs (include the ducts)

lateral ventricles > (interventricular foramen) > 3rd ventricle > (cerebral aqueduct > 4th ventricle > central canal OR sub arachnoid space (via lateral aperture) > subarchnoid granulations > drain into dural venous sinus > drains into internal jugular vein > back to heart/lungs > gets oxygenated > back to ventricles

how does CSF get to subarachnoid space and into internal jugular vein?

from 4th ventricle > subarachnoid space/arachnoid granulations > dural venous sinuses > internal jugular vein

what creates the blood-brain-barrier? what exactly is it

the tight junctions of the capillary’s endothelial cells (between blood vessels and the brain)

what makes the tight junctions so tight in the BBB?

astrocytes (glial cell - supporting cell of neurons)

- they push up against the capillaries

what substances are allowed to pass through the BBB?

there are quite a lot actually

lipid soluble substances: O2, H2O, Co2, alcohol, barbiturates (depressants/sedative), nicotine, caffeine

glucose via facilitated diffusion

some ions can diffuse very slowly

what kind of substances are not allowed to pass thru BBB?

proteins, most anti-biotics, pathogens

which part of the brain is the major relay station between sensory and motor signals? and plays a role in maintaining consciousness?

thalamus

which part of the brain regulates homeostasis?

hypothalamus

how does the hypothalamus regulate homeostasis? (6)

1. communicates with autonomic NS: (heart rate, smooth muscle for stomach, urinary bladder contractions, glands)

2. produces hormones

3. regulates emotional and behaviour patterns with limbic system (emotional expression and sexual arousal)

4. regulates eating and drinking (hunger, satiated, thirsty)

5. regulates body temperature

6. regulates circadian rhythm

which hormones does the hypothalamus have an effect on via the pituitary gland

releasing hormones, inhibiting hormones, oxytocin

which part of the brain is the “emotional brain”? what is included in this system ?

limbic system: amygdala, hippocampus, thalamus, hypothalamus, cingulate gyrus

what part of the brain plays a role in emotions, memory, motivation, and smell?

for example: when you smell a nice cinnamon candle it provokes a certain feeling/memory

limbic system

what part of the brain is in control of the start/stop of movement + start/stop of cognitive processes (ie: attention, memory, planning) + autonomic subconscious mvmts (ie: arm swings when walking)

basal nuclei aka corpus striatum

what is makes up the basal nuclei/corpus striatum?

caudata nucleus, putamen, globus pallidus

which part of the brain controls for coordination during movement, balance, and posture? how does it do this?

cerebellum

-evaluates voluntary mvmts and controls for subconscious muscle

how does the cerebellum attach to the brainstem? what is contained in this?

cerebellar peduncles: axons that connect cerebellum to brainstem and cortex (used for coordination and balance)

what is contained in the midbrain of brainstem?

cerebral peduncles, tectum, substantia nigra, red nuclei

what is the function of the midbrain’s cerebral peduncles?

axons of motor pathway

what is the function of the midbrain’s tectum? give an example

reflex center for audio & visuals, and startle reflex

ex: sudden mvmt when you’re surprised by unexpected presence

what is the function of the midbrain’s substantia nigra?

release dopamine and help control subconscious muscle

what happens if there is a loss of neurons in the substantia nigra (midbrain)?

parkinson’s disease

what is the function of the midbrain’s red nuclei?

this is the synapse spot for the cerebral cortex and cerebellum that controls for mvmt

what part of the brainstem coordinates voluntary motor output and breathing?

pons

which part of the brainstem contains the axons that connect L/R of the cerebellum AND connects the cortex to cerebellum (contralaterally)?

pons

what part of the brain stem regulates heart beat and normal breathing? and autonomic reflexes of: swallowing, vomiting, sneezing, coughing and hiccuping

medulla oblongata

what 2 things are part of the medulla oblongata?

pyramids and olive

what is the “pyramid” in the medulla oblongata?

decussation of cortico-spinal tracts (crossing over)

→ tracts (axons) that control for voluntary mvmt of the limbs and trunk

what is the “olive” in the medulla oblongata?

communicates with cerebellum to provide instructions when learning new motor skills → adjusts movements

the cerebellum communicates with what part of the brain stem when leanring new motor skills?

olive part of the medulla oblongata

which brain lobe is in charge of executive functioning, motor control, personality

frontal lobe

which brain lobe is in charge of sensory perception and integration?

parietal lobe

which brain lobe is in charge of auditory processing, memory, and emotion?

temporal lobe

which brain lobe is in charge of visual processing?

occipital lobe

identify these structures in the picture:

• central sulcus

• longitudinal fissure

• pre-central gyrus

• post-central gyrus

where do you find the primary MOTOR cortex?

pre-central gyrus

where do you find the primary somato-sensory cortex?

post central gyrus

what is an association area?

area that combines motor and sensory info to make sense of things

somatosensory association area recognizes what

recognizes objects just by touching it

(can have eyes closed and hold something and know what that object is)

which lobe stores facial recognition?

inferior, temporal lobe

what does the orbito-frontal lobe cortex recognize? where is this area?

discriminate among different odours,

lateral frontal lobe

which association area allows for the formation of thoughts based on all incoming sensory inputs? where is this area

common integrative around the parietal lobe

(sensory, visual, auditory info)

what is the pre-frontal cortex in charge of?

higher cognitive functioning: personality, intellect, complex learning, recall info, initiative, judgement, reasoning, planning, conscience, mood

where is wernicke’s area and what is it for?

language comprehension (ability to understand what is being said)

temporal/parietal lobe

dominant in left hemisphere

where is broca’s area and what is it for?

speech production (ability to speak)

frontal lobe, anteriorly

dominant in left hemisphere

think: broca’s = speech = closer to tongue = anterior frontal lobe

name the 3 spaces in the spinal cord

epidural space, subdural space, subarachnoid space

what attaches the spinal cord to the arachnoid and dura mater in order to protect the spinal cord from shock/displacement? hint: it’s part of the meninges mater

denticulate ligaments (extensions of pia mater)

why is there a cervical and lumbo-sacral enlargement in the spinal cord?

these have the nerves that innervate the upper and lower limbs

what is the difference between conus medularis, cauda equina, and filum terminale in the spinal cord?

• conus medularis: end of the cord (around L1)

• cauda equina: horse’s tail, nerves of lumbar, sacral, and coccygeal regions

• filum terminale: the final end of the cord, attaches to the coccyx

the dorsal root ganglion contains what kind of cell bodies ?

sensory neuron cell bodies

motor neurons are in the ___ nerve root

sensory neurons are in the ___ nerve root

motor: anterior/ventral

sensory: posterior/dorsal

gray mater and white mater contains what part of the nueron

gray mater: cell bodies

white mater: myelinated axons

where would you find the cell bodies (gray mater) of autonomic motor neurons in the spinal cord? < this would be the pre-ganglionic neuron

lateral gray horn

what is meant by “tract” in the spinal cord

a tract is a bundle of myelinated axons

“track” = road = highway of neurons

what information does the anterior and lateral spinothalamic tracts carry to the cns?

pain, temperature, itch, tickle (the “uncomfortable” feelings)

describe the anterior and lateral spinothalamic tracts

tracts = white mater = axons

spine → thalamus = ascending pathway = sensory neurons

anterior and lateral spinal column

what information does the posterior column-medial lemniscus tracts carry? is this an ascending or descending pathway?

info about touch, pressure, vibration, proprioception

ascending pathway

describe the anterior and lateral corticospinal tracts

tracts = white mater = myelinated axons

cortico-spinal = descending pathway = motor neurons

anterior and lateral white column on spinal cord

what do the anterior and lateral corticospinal tracts innervate?

somatic/voluntary skeletal muscle

what makes a reflex a spinal reflex

when synapse happens only within the spinal cord

define these components of a spinal reflex:

• sensory receptor

• sensory neuron

• integrating center

• motor neuron

• effector

• sensory receptor: detects stimuli

• sensory neuron: sends signal from receptor to spinal cord

• integrating center: synapse between sensory neuron to motor nueron (may contain an interneuron)

• motor neuron: sends impulse from spinal cord down to effector muscle

• effector: muscle that responds

give an example for each component of a spinal reflex for touching a hot object:

• sensory receptor

• sensory neuron

• integrating center: this is a polysynaptic reflex

• motor neuron

• effector

• sensory receptor: pain receptors in skin

• sensory neuron

• integrating center: interneuron

• motor neuron

• effector: finger/arm muscles = move hand away