Unit 2 Flashcards
How is the brain protected?
-cranium provides a rigid outer layer of protection
- connective tissue layers surround and partition brain
What are the types of connective tissue layers that surround and part the brain?
- dura matter
-pia matter - arachnoid matter
How do connective tissue layers protect and support brain?
-encloses and supports blood vessels serving the brain
-contains circulating CSF
- interior blood-brain barrier structures selectively control movement of materials between circulating blood and brain tissue
What is the dura mater of the cranium?
- tough double layer (meningeal and periosteal) of connective tissue that forms outer meningeal membrane
What are the layers of the dura matter?
-outer periosteal
-meningeal
What is dura matter made of?
- collagen, dense irregular connective tissue
What does the outer periosteal layer do?
- forms periosteum on the internal surface of cranial bones
-fused with meningeal layer in most places
What does the meningeal layer do?
- innermost dura matter layer
What layer is also called true dura matter?
-meningeal layer
What is the dural sinus?
- acts as modified vein collecting venous blood and CSF
Where is the dural sinus?
found in space between periosteal and meningeal layers
What is the dural septa?
-when two meningeal layers meet and extend inwards
What does the dural septa do?
- partitions specific regions of the brain, providing support and stabilization
What are the dura matter spaces?
-epidural space
-subdural space
What is the epidural space of the cranium?
a potential space that contains arteries and veins and support the bones of the cranium and meninges
What is the subdural space of the cranium?
- a potential space found between the dura and arachnoid matter where fluid can collect
- usually not present but can appear when filled with blood and other fluid
When do epidural and subdural hematomas occur in the cranium?
when blood pools in these regions and compresses blood regions
What causes epidural hematomas?
- High-impact traumatic injury
What causes subdural hematomas?
- usually violent movement or sharp turn breaks blood vessels
What is arachnoid matter?
- connective tissue membrane located next to, deep of, subdural space
What is arachnoid matter made of?
- arachnoid trabeculae
What are arachnoid trabeculae?
-collagen and elastic extensions
Where is arachnoid trabeculae located
-transverse to subarachnoid space
What does arachnoid trabeculae do?
connects superficial arachnoid matter to deep pia matter
What drives CSF movement?
- pressure gradient
-CSF pressure is greater than venous pressure
What do arachnoid villi do?
- help move CSF from subarachnoid space to dural sinus
How does CSF move?
- CSF forms in the ventricles of the brain and drains into and circulates through, the subarachnoid space of the meninges
- CSF goes from subarachnoid space into villi and transports into dural sinus where it mixes with venous blood
- ciliated ependymal cells beat synchronously aiding in the movement of CSF through ventricles and into subarachnoid space
What is a granulation?
- a collection of villi
What is pia matter?
- innermost, thin meningeal layer that adheres to the contours of the brain surface
- tender
What is a fissure?
- deep-defined depression in the brain surface
- in pia matter
What is a gyrus?
-elevated regions of the cerebral cortex
-in pia matter
What is a sulcus?
- shallow groove in the cerebral cortex
-in pia matter
Where is the choroid plexus found?
-each of the four ventricles
Where does CSF form?
- 30% forms at the choroid plexus
How does CSF circulate through the ventricles?
- lateral- interventricular foramen- 3rd- cerebral aqueduct- fourth before being routed into the subarachnoid space through the meninges
- small amounts of CSF enters the central canal of the spinal cord from 4th ventricle but most goes from the fourth ventricle to the subarachnoid space through lateral and medial apertures
What ventricle has the most CSF?
lateral because its the biggest
What are the CSF functions?
- buoyancy
-protection
-environment stability
-supports nervous tissue
How does CSF provide buoyancy?
- reduces brain’s weight by 95%
How does CSF provide protection?
-adds liquid cushion
How does CSF provide environment stability?
- helps with the transport of nutrients and wastes
-protects against fluctuations
How does CSF support nervous tissue?
-plays prominent role in brain development and homeostasis
What does the choroid plexus do?
- forms a selective barrier that determines what materials move from blood plasma into ventricles, forming CSF
What is the choroid plexus made of?
- capillaries, pia matter, ependymal cell
-capillaries bc CSF is product of blood
Where are all the places CSF is made?
-30% at choroid plexus
-additional CSF across ependymal cells lining ventricles 30%
- fluids moving into subarachnoid space 40%
How does CSF follow the pressure gradient?
-CSF pressure > ventricular pressure
- flows through subarachnoid space to arachnoid villi to dural sinuses, following the pressure gradient
What is the blood brain barrier?
- highly selective semipermeable barrier thast regulates which substances enter brain’s interstitial fluid
How do ependymal cells modify CSF so it has a unique composition?
-more Na+ and Cl-
-less K+, Ca2+, glucose
-compared to blood plasma
What does the blood brain barrier do?
-helps prevent neuron exposure to harmful substances such as drugs and waste products
- protects the brain from hormones and NT fluctuation, maintaining a constant environment
What is the blood brain barrier made of?
-endothelial cells
-astrocytes
What do endothelial cells do for the blood brain barrier?
-reduced permeability
-continuous basement and tight junctions between ells and pericytes
What do astrocytes do for the blood-brain barrier
- perivascular feet that surround the capillaries
- gatekeepers that selectively allow certain substances to cross
What is allowed to cross the blood-brain barriers and is ok?
- h20
-respiratory gases
-glucose
-soluble
What can cross the blood-brain barrier that you want to prevent
- drugs (cocaine, nicotine, caffeine, meth)
- alcohol
-pathogens
-medicine
Where is the blood-brain barrier missing or reduced
-choroid plexus
-hypothalamus
- pineal gland
Why is the blood-brain barrier missing or reduced in the hypothalamus and pineal gland?
its where we produce hormones that need to travel through the blood
How many hemispheres and lobes does the cerebrum have?
-2 hemispheres
- 5 lobes per hemisphere
What makes up the diencephalon?
-thalamus
- hypothalamus
- epithalamus
What are the parts of the brainstem?
-pons
-medulla oblongata
- midbrain
How much O2 does the brain receive?
20%
What percentage of body weight is the brain?
2%
Why is the brain highly folded?
increases surface area for neurons
What is another name for the cerebral cortex?
seat of intelligence
-enlarged in humans compared to other animals
Why do humans have larger frontal lobes?
allows for higher level functions
Is the brain ipsilateral or contralateral?
contralateral?
What does contralateral mean for the brain?
- cerebral hemispheres receive sensory info and send motor controls to the opposite side of the body
What does lateralization mean for the brain?
-each hemisphere specializes in specific high-order functions (like speech)
-still has some functional overlap tho
What percentage of the brain’s weight is the cerebrum?
- 85%
What connects the left and right hemispheres of the cerebrum?
- corpus calllosum
What is the corpus callosum?
- longitudinal fissure with axons “tracts”
-connects left and right sides
What does the frontal lobe control?
- voluntary movement
- decision making
- personality
-communication
What are the major parts of the frontal lobe?
-primary motor cortex
- premotor cortex
- frontal eye field
- motor speech area
What does the primary motor cortex control?
voluntary motor movement
What does the premotor cortex do?
- plans movements (skilled/learned movements like playing the piano)
-plans things that require coordination - just plans, doesn’t cause the muscle contraction
What does the frontal eye field control?
- eye movement muscles (where you look)
- helps with binocular vision
What is binocular vision?
you can see and focus both eyes on one spot
What is the motor speech area?
- controls muscles used for speech
What does the parietal lobe do?
- receives inputs related to touch and body positions; conscious of sensations received
What are some major parts of the parietal lobe?
- somatosensorry association
-somatosensory cortex
What does the somatosensory association area do?
-integrates sensory info allowing us to identify objects based on previous experience
- identifies pressure, texture, temperature, shape
What does the somatosensory cortex do?
receives info from skin and proprioceptors
What are proprioceptors?
muscle and joint receptors
What is the occipital lobe responsible for?
- receives, processes, stores visual info
What are the major parts of the occipital lobe?
- primary visual cortex
-visual association area
What is the primary visual cortex?
- receives and processes incoming visual info
What does the visual association area do?
- integrates color, movement, and form to identify things we see based on memory
What is the temporal lobe in charge of?
hearing and smelling
What are the parts of the temporal lobe?
- primary auditory cortex
- auditory association cortex
-primary olfactory cortex
What does the primary auditory cortex do?
-receives and processes sound
What does the auditory association cortex do?
-interprets sounds
-stores and retrieves memories of sound
What does the primary olfactory cortex do?
conscious awareness of smells
What is the insula in charge of?
-hidden cortex
- memory and interpretation of taste
What cortex is the primary gustatory cortex a part of?
insula
What is the primary gustatory cortex in charge of?
- processing taste information
What is the cerebrum overall in charge of?
-intelligence and reasoning
- conscious thought, memory , judgement
-voluntary motor, visual auditory activities
What are petalias part of?
cerebrum
What are petalias?
-slight enlargement related to handedness
-part of lateralization
- ex. right-handed people have right frontal petaliass, left occipital petalias
Is there ever lateralization overlap?
yes especially for complex functions
What does the left side of the brain control?
- speech
- categorical things like math
Wernicke’s area is in left, controls language comprehension
What does the right side of the brain control?
- representational lings like visual-spatial relationships
-art and music
How are jobs in the brain divided?
- 50% function in right 50% function in left
By what age is lateralization established
5
How is the brain sexually dimorphic?
- males have more lateralization - suffer more loss when a hemisphere is damaged - thicker corpus callosum
- females have bilateral language processing - more coordination between hemispheres
What does the prefrontal cortex do?
- retrieves and coordinates info from multiple areas of the brain
- involved in planning future behaviors, evaluating consequences, decision making, impacts behavioral choices made based on societal norm
What age does the prefrontal cortex develop into?
develops into the 20s
What is gray matter made of?
- cell bodies
-dendrites
-unmyelinated axons
What is white matter made of?
myelinated axons
What are tracts?
- bundles of parallel axons in the CNS
What are cerebral nuclei?
- internal clusters of gray matter embedded within white matter
-not like nucleus
What are association tracts?
- bundles of axons that connect regions of the cerebral cortex within the same hemisphere
- localized to only R or L hemispheres
What are arcuate fibers?
-part of association tracts
- connects areas in the same lobe
What are longitudinal fasciculi?
-part of association tracts
-connects different lobes
-runs the length of the hemisphere like posterior to anterior…
What are projection tracts?
-link cerebral cortex to inferior brain regions and spinal cord
-contains decussation
What is the decussation?
where crossing over occurs
What are commissural tracts?
-link right and left hemispheres
- corpus callosum = largest
-also anterior commissure
What is the Diencephalon thalamus?
-contains right and left thalamic bodies, each with multiple groups of nuclei that are connected by the intermediate mass
What are the functions of the diencephalon thalamus?
- thalamus is the final relay point for incoming sensory info
- info is processed and selectively sent to the coordinating cerebral region
- acts as an info filter, relaying some signals to cortex but not others
- gateway to cerebral cortex
What is the largest region of the diancephalon?
thalamus
What is the diencephalon hypothalamus?
- connected to te pituitary gland through the hypothalamus
What are the functions of the diencephalon hypothalamus?
- controls the autonomic nervous system
- controls endocrine system
-regulation of body temp - emotional behavior
- food intake regulation
-water intake regulation
-sleep-wake cycle
How does the diencephalon hypothalamus control the autonomic nervous system?
sends signals to brain stem in order to regulate HR, BP, respiration
How does the diencephalon hypothalamus control the endocrine system?
- secretes hormones
-regulates hormones
-hypothalamus affects pituitary and pituitary affects everything else
How does the diencephalon hypothalamus control body temp?
detects altered temperature and signals to heat or cool body
How does the diencephalon hypothalamus control emotional behavior?
-part of the limbic system, controls emotional responses like pleasure or fear etc..
How does the diencephalon hypothalamus control food intake?
- monitors nutrient levels and regulates hunger
How does the diencephalon hypothalamus control water intake?
monitors concentration of dissolved substances in blood and regulates thirst
How does the diencephalon hypothalamus control the sleep wake cycle?
directs pineal gland in its role to regulate sleep-wake cycles
Where is the diencephalon hypothalamus located?
below thalamus
What are the parts of the diencephalon epithalamus?
-pineal gland
- habenuclear nuclei
What does the pineal gland do?
- the endocrine gland that secretes melatonin
-helps regulate circadian rhythm
When should melatonin levels be highest?
at night when you are sleeping
What is the circadian rhythm?
day-night cycles
What effects melatonin?
- light inhibits melatonin formation
What is the habenuclear nuclei?
-involved in visceral and emotional responses to odors
-helps keep us from eating spoiled food
What is the limbic system?
- composed of multiple cerebral and diencephalic structures that collectively process and experience emotions, form memories, and regulate motivation
-“emotional brain”
What are the parts of the limbic system?
-cingulate gyrus
-hippocampus and parahippocampus gyrus
- amygdaloid body
-olfactory structures