The Central Nervous System

neurovascular unit

a functional unit of groups of neurons and their associated astrocytes that interact with smooth muscle cells and endothelial cells

• responsible for blood supply and regulating blood flow

chorid plexus

site of production for CSF in adults

• formed by invagination of ependymal cells into the ventricles which then become vascularized

interstitial fluid

the extracellular fluid filling the interstices of the tissue and bathing the cells

tight junction

belt-like region of adhesion between adjacent cells that regulate paracellular fluid and contribute to the maintenance of the cell polarity by stopping molecules from diffusing

meninges

arrangement of three protective membranes surrounding the brain

• dura: thick outer connective tissue layer

• arachnoid: barrier layer

• pia mater: thin layer covering glia limitans

receptor-mediated transcytosis

mechanism for vesicle-mediated transfer across the cell that requires specific binding to the ligand followed by internalization (endocytosis)

adsorptive mediated transcytosis

mechanism for vesicle-mediated transfer across the cell that requires non-specific binding to the ligand followed by internalization (endocytosis)

perivascular endfeet

specialized foot processes of perivascular astrocytes that are opposed to the outer surface of brain microvessels and have specialized functions to induce and regulate the BBB

pericyte

a cell with mesodermal origin and contractile phagocytic phenotype that is associated with the outer surface of capillaries

basal lamina

extracellular matrix layer produced by the basal cell membrane and used as an anchoring and signaling site for cell-cell interactions

protection in the brain includes

the bones of the cranium, the cranial meninges and the cerebrospinal fluid

what are the 3 cranial meninges?

• dura mater: has two fibrous layers with a space in between containing tissue fluids, blood vessels, and the lymphatic system

• arachnoid: contains arachnoid membrane (epithelial layer) and subarachnoid space (CSF)

• pia mater: accompanies the branches of cerebral blood vessels

what is the difference between the arachnoid and the pia mater?

the arachnoid does not follow the brains underlying folds while the pia mater does

how is oxygen passed through the brain?

it moves freely through the blood-brain barrier

how is glucose passed through the brain?

it requires membrane transporters and the contribution of astrocytes through lactate

during a period of development or starvation what does the brain utilize?

ketone bodies

during a period of intense physical activity, what does the brain use for energy?

lactate (produced by astrocytes)

what are the types of arteries that supply blood to the brain

internal carotid arteries and vertebral arteries

• anterior, middle, and posterior cerebral artery

• basilar artery

• internal carotid artery

• vertebral artery

what are the types of veins that supply blood to the brain?

internal jugular veins

what is anastomosis and what is an example of it that we talked about?

it is a cross-connection between adjacent channels (in this case arteries)

• circle of Willis: collateral circulation

what is the brain interstitial fluid?

space among neural cells and capillaries that make up 15-20% of the brain volume

what does the brain interstitial fluid consist of?

interstitial fluid and extracellular matrix

where does the brain interstitial fluid originate from?

cerebral spinal fluid, cell metabolism and the vascular system

what is the BBB composed of?

capillary endothelial cells, basal lamina, endfeet of astrocytes, and pericytes

what are the features of the BBB?

highly selectively permeable, very limited paracellular solute flux, and regulates composition and volume of the brain interstitial fluid

what does the neurovascular unit do?

regulates the BBB and regional blood flow

what does the neurovascular unit consist of?

capillary endothelial cells, pericytes, glial cells (astrocytes and microglial cells) and neurons

compare the brain interstitial fluid to the plasma

the brain interstitial fluid has

• lower pH, protein content, glucose concentration, potassium amount and HCO3

why does the brain interstitial fluid have a lower pH

because of the high permeability of CO2

what does a low protein content result in?

low buffering capacity

what does the brain interstitial fluid have low potassium?

due to potassium absorption into the blood

from breath to breath, what is most likely to be more subjected to a change in pH?

brain interstitial fluid

• pH decreases as phrenic activity increases (as we take in air)

true or false: the BBB is involved in many PNS pathologies

false

• CNS pathologies

disruption of the BBB will likely lead to…

an increase in extracellular potassium which increases Ek

describe the cerebral spinal fluid: location and purpose

• location: around and inside the spinal cord

• purpose:

  • cushion and protection

  • maintain chemical stability

  • clear waste products

what is the CSF produced?

the choroid plexus in the ventricles

• fourth, third, and lateral

circulation of the CSF

• leaves the 4th ventricle via paired lateral apertures or the single median aperture

• flow through the subarachnoid space

• flows into the arachnoid villi and then drains into the dural venous sinuses

as CSF circulates and the CNS's interstitual fluid have been shown to have similar ion concentrations, what kind of movement is involved?

diffusion

how do glial cells control the glymphatic system?

through changing their sizes

• need to regulate extracellular volume to maintain brain function

what functions does the cerebrum control?

higher brain functions

what is the center for homeostasis?

diencephalon

what does the brainstem control?

autonomic and reflex centers

what does the cerebellum control?

coordination of movement and much more

what are the four cerebrum lobes?

frontal, parietal, occipital and temporal

• occasionally the insula which is located deep in the temporal lobe

what does the frontal lobe do?

motor, speech, memory formation, personality and emotion

• makes you who you are

what does the parietal lobe do?

somatosensory cortex

• pain, temperature, etc.

what does the occipital lobe do?

visual processing and storing visual memories

• eyes in the back of your head

what does the temporal lobe do?

hearing, speech, language and smell

• ears on the sides of your head

describe functions of the frontal cortex

motor control, goal directed behavior, planning and organizing strategies, working memory problems, problem solving and inhibitions

• trying to cross the street example

the primary motor cortex is associated with what?

homunculus (little person)

orbitofrontal cortex

cognitive processing of decision making

ventromedial prefrontal cortex

inhibiting inappropriate behavior

phineas gage’s example

resulted in personality change, little self-restraint, and changes in reasoning and capacity to understand and follow social norms

• most likely affected orbitofrontal cortex and ventromedial prefrontal cortex

describe the functions of the parietal lobe

senses and integrates sensations; spatial awareness and perception

what is proprioception

awareness of body

• parts in space and in relation to others

what does the primary somatosensory cortex/postcentral gyrus do?

receives information

what does the somatosensory association cortex do?

processes information

what does the primary gustatory cortex do?

taste sensation

describe functions of the temporal lobe

hearing, organization, and comprehension of language, information retrieval

• information not stored in the temporal lobe necessarily

what does the primary auditory cortex do?

processes auditory information

wernike’s area

processing sound: specifically comprehension of language

• long run on sentences that dont make sense

the primary olfactory cortex (deep) is responsible for what?

smell (conducted from olfactory bulb)

describe the function of the occipital lobe

processing, integration and interpretation of vision and visual stimuli

primary visual cortex

gives you a 2D sketch

• just tells you something is moving

visual association area

interprets information acquired through the primary visual cortex

what are the primary language areas?

broca’s area, wernicke’s area, angular gyrus and arcuate fasciculus

what is broca’s area responsible for?

speech articulation

• hard to get words out

where is the angular gyrus

superior edge of temporal lobe

what is the arcuate fasciculus

a white matter tract that connects to broca’s and wernicke’s area

what does the arcuate fasciculus allow?

coordinated comprehensible speech

• makes the connection!

what is preserved in the arcuate fasiciculus?

auditory comprehension and speech articulation

what is affected by the arcuate fasciculus?

repeating heard speech/paraphrasing

what is brain lateralization?

cerebral dominance

• left: language, math and logic

• right: spatial abilities, face recognition, visual imagery and music

split brain syndrome

cut of the corpus callosum so there is a disconnect between the left and right hemispheres

basal ganglia

a group of structures below the cortex involved in motor, cognitive, and emotional functions

• forebrain and midbrain structures

  • caudate nucleus

  • putamen

  • globus pallidus

  • claustrum

  • amyloid body

brain-derived neurotrophic factor (BDNF)

sometimes referred to as brain fertilizer and is a protein that helps promote the growth maintenance and survival of neurons

hypothalamus

a small structure located at the base of the brain where signals from the brain and body’s hormonal system interact

limbic system

a group of evolutionarily older brain structures that encircle the top of the brain stem

• have complex role in emotion, instinct and appetitive behaviors

medulla olongata

lower part of the brain stem responsible for life-regulating functions like breathing and heart rate

parkinson’s disease

a neurodegenerative disease characterized by tremor, slowed movement and speech changes due to death of dopamine neurons located on the substantia nigra

pituitary gland

an endocrine organ at the base of the brain that is closely linked to the hypothalamus.

• composed of two lobes

  • anterior and posterior

• secretes hormones that regulate the activity of the other endocrine organs in the body

spinal cord

the other half of the central nervous system

• a cable that descends from the brain stem to the lower back and consists of an inner core of grey matter surrounded by white matter

straitum

a small group of subcortical structures

• caudate nucleus

• putamen

• nucleus accumbens

located in the midbrain

involved in movement and reward-driven behaviors

substantia nigra

small region in the midbrain thats part of the brains reward system

• in parkinson’s disease, the dopamine neurons in this region die off leading to the disorders side effects

subthalamic nucleus

a small brain structure located in the basal ganglia that plays a role in coordinating movement

• most common target for neuromodulation techniques such as deep brain stimulation to help diminish symptoms of parkinson’s

thalamus

a brain structure at the top of the brain stem

• acts as a two-way relay station, sorting, processing and directing signals from the spinal cord and midbrain structures to the cerebrum

what is the basal ganglia considered as?

the “side loop” controlling the subconscious

what does the basal ganglia do?

• receive input from the entire cerebral cortex and thalamus

• sends output to cerebral cortex through thalamus

• modulates motor output and prevents unwanted movement

what makes up the straitum?

caudate nucleus and putamen

what does the globus pallidus contribute to?

muscle tone (via thalamus)

the direct pathway of movement related to the basal ganglia is (excitatory/inhibitory)

excitatory

the indirect pathway of movement related to the basal ganglia is (excitatory/inhibitory)

inhibitory

nigrostraitial projection

dopaminergic neurons going from the substania nigra to the striatum

• direct pathway neurons have D1 receptors (depolarize) while indirect pathways have D2 receptors (hyperpolarize)

how does the nigrostraitial projection affect the direct pathway

reinforces it

how does the nigrostraitial projection affect the indirect pathway?

inhibits it: suppresses the inhibitory neurons

what does the amygdala control?

emotion/mood

what does the diencephalon consist of?

• epithalamus: posterior/superior

• thalamus: superior

• hypothalamus: inferior/anterior

what dies the epithalamus include? whats its function?

pineal gland: secretes melatonin which is a hormone that helps regulate day and night cycles

what does the thalamus do?

sensory impulses from all conscious senses converge on the thalamus

• except olfactory sense

principal and final relay for all sensory information

efficient filter

what does the hypothalamus do?

• master control of the autonomic nervous system

• regulates many homeostatic mechanisms throughout the entire body

• regulation of body temperature

• control of emotional behavior, food and water intake and sleep-wake cycles