Cranium, Scalp, Meninges, And Brain Flashcards
What are the contents of the scalp?
S -> skin
C -> CT
A -> aponeurosis
L-> loose CT
P -> pericranium
What are the neurocranium tissue layers?
- epicranial aponeurosis
- loose areolar tissue
- pericranium
- bone
- dura, arachnoid, pia mater
- cerebral cortex
What are the cranial meninges?
- three dense regular CT layers that separate the soft tissue of the brain from the bones of the cranium
- enclose and protect blood vessels that supply the brain
- contain and circulate CSF
- parts of the cranial me enigma form some of the veins that drain blood from the brain
- dura, arachnoid, pia mater
Describe the dura mater.
- tough membrane composed of two fibrous layers
- strongest of the meninges
-composed of two layers:
+periosteal layer (superficial) attaches to the periosteum of the cranial bones
+meningeal layer lies deep
The periosteal and meningeal layers are usually fused together except where?
-in specific areas where the two layers separate to form large, blood filled spaces called dural venous sinuses
Describe the arachnoid mater.
- lies immediately internal to the dura mater
- partially composed of a delicate web of collagen and elastic fibers, termed arachnoid trabeculae
- between the arachnoid and dura mater is the subdural space
- under arachnoid is the subarachnoid space
Describe the pia mater.
- innermost of the cranial meninges
- thin layer of delicate CT that tightly adheres to the brain and follows every contour of the brain surface
What are the cranial dural septa? What are in the septa?
- meningeal layer of the dura mater extends as flat partitions/septa deep into the cranial cavity at four locations
- membranous partitions separate specific parts of the brain and provide additional stabilization and support to the entire brain
- contain venous sinuses
What are the four cranial dural septa?
- falx cerebri
- tentorium cerebelli
- falx cerebelli
- diaphragma sellae
What nerves can be found in the cavernous sinus? What artery?
- oculomotor n
- trochlear n
- abucent n
- trigeminal n
- internal carotid artery
What are the arteries that supply the meninges?
- frontal branch of middle meningeal artery
- middle meningeal artery
- parietal branch of middle meningeal artery
What is CSF?
- clear, colorless liquid that circulates in the ventricles and subarachnoid space
- bathes the exposed surfaces of the central nervous system and completely surrounds it
- formed by the choroid plexus in each ventricle
- produced by secretion of a fluid from the ependymal cells that originate from the blood plasma
- similar to blood plasma but has greater amounts of Na, H, and Ca -> less K and Ca
What are the functions of CSF?
- buoyancy
- protection
- environmental stability
What are the brain ventricles?
- cavities within the brain that are derived from the lumen of the embryonic neural tube
- continuous with one another as well as with the central canal of the spinal cord
What are the four ventricles of the brain?
- 2 lateral ventricles in the cerebrum separated by septum pellucidum
- in diencephalon is a smaller ventricle called the third ventricle -> communicates with lateral ventricles via interventricular foramen
- fourth ventricle is located within the pons and cerebellum
How is CSF circulated?
- produced by the choroid plexus in the ventricles
- flows from the third ventricle through the mesencephalic aqueduct into fourth ventricle
- as CSF flows through the subarachnoid space, it removes waste products and provides buoyancy to support the brain
- excess CSF flows into the arachnoid villi, then drains into dural sinuses
How is CSF released into blood?
-pressure allows the CSF to be released into the blood without permitting any venous blood to enter the subarachnoid space. The greater on the CSF in the subarachnoid space assures that CSF moves in the venous sinuses
What causes hydrocephalus? How can it be treated???
- typically from an obstruction in CSF flow that restricts its reabsorption in the venous bloodstream
- treated by inserting a ventriculoperitoneal shunt that drains to the abdominal cavity
- also treated by ventriculostomy that creates a hole in the floor of the third ventricle that drains into the subarachnoid space
What does the BBB do?
- strictly regulates what substances can enter the interstitial fluid of the brain
- prevents exposure of neurons in the brain to drugs, waste products in the blood, and variations in levels of normal substances that could adversely affect brain function
What features of the BBB regulate flow?
- tight junctions prevent materials from diffusing across the capillary wall
- astrocytes act as gatekeepers that permit materials to pass to the neurons after leaving the capillaries
- reduced or missing in three distinct locations in the CNS: choroid plexus, hypothalamus, and pineal gland
What protects the brain?
- boney structures
- CT membranes called meninges surround and partition portions of the brain
- CSF acts as a cushioning fluid
- BBB to prevent entry of harmful materials from the bloodstream
What composes gray and white matter?
- gray matter: motor neuron and interneurons bodies, dendrites, axon terminals, and unmyelinated axons
- white matter: myelinated axons
Generally how is brain tissue organized?
- during brain development, an outer, superficial region of gray matter forms from the migrating peripheral neurons
- external sheets of gray matter, called the cortex, cover the surface of most of the adult brain (cerebrum and cerebellum)
What are the three initial brain vesicles that are formed at the end of the 4th week?
- prosencephalon
- mesencephalon
- rhombencephalon
What are the 5 secondary brain vesicles that are differentiated by the end of week 5? What do they form?
- telencephalon -> cerebrum
- diencephalon -> thalamus, hypothalamus, and epithalamus
- mesencephalon
- metencephalon -> pons and cerebellum
- myelencephalon -> medulla oblongata
What are the 4 major brain regions?
- cerebrum
- diencephalon
- brainstem
- cerebellum
How is the cerebrum divided?
- divided into two halves
- each hemisphere is subdivided into five functional areas called lobes
- folds = gyri, depressions = sulcus
- brain associated with 12 cranial nerves
What are the 5 lobes?
- frontal lobe
- parietal lobes
- occipital lobe
- temporal lobe
- insula
Primary motor and sensory cortical regions are connects to what?
-adjacent association areas that process and interpret incoming data or coordinate a motor response
What does the premotor cortex do?
- coordinate learned skilled motor activities (playing piano)
- frontal lobe
What does the somatosensory association area do?
- parietal lobe
- integrates and interprets sensations to determine the texture, temperature, pressure, and shape of objects
What does the auditory association area do?
- temporal lobe
- interpret characteristics of sound and stores memories of sounds heard in the past
What does the visual association area do?
- occipital lobe
- process visual info by analyzing color, movement, and form to identify things we see
What is Wernicke’s area?
- left hemisphere
- recognize, understand, and comprehend spoken or written language
- works with Broca’s area which is the motor speech area
What is the Gnostic area?
- parietal, occipital, temporal
- clock indicates 12:30, smell food cooking, friend talks hunger, you interpret it to be lunch time
What are tracts?
-central white matter
What are association tracts?
-connect different regions of cerebral cortex within the same hemisphere
What are commissural tracts?
-between cerebral hemispheres
What are projection tracts?
-link cerebral cortex to the caudal brain regions
What are cerebral nuclei?
-paired irregular masses of gray matter buried deep within the central white matter
What is the caudate nucleus?
- C shaped
- neurons within stimulate appropriate muscles to coordinate arm and leg movements associated with walking
What is the amygdaloid body?
- expanded region at the tail of the caudate nucleus
- participates in the expression and control of moods and emotions
What is the putamen and globus pallidus?
- both form lent inform nucleus
- putamen controls muscular movement at a subconscious level
- the globus inhibits activity of the thalamus
What is the claustrum?
-subconscious processing of visual information
What is the diencephalon?
-provides the relay and switching centers for some sensory and motor pathways and for control of visceral activities
What does the epithalamus do?
- posterior part is the pineal gland which secretes melatonin
- habenular nuclei help relay signals from the limbic system and control visceral and emotional responses to odors
What is the thalamus responsible for?
-sensory impulses from all conscious senses except olfaction converge on the thalamus
What is the hypothalamus responsible for?
Various functions controlled by specific nuclei
- mammillary body -> smell and swallow
- dorsomedial nucleus -> sympathetic
- para ventricular nuclei -> oxytocin
- preoptic area -> body temp
- anterior nucleus -> parasympathetic
- supraoptic nucleus -> ADH
- suprachiasmatic nucleus -> circadian rhythm
What are structures in. The mesencephalon?
- cerebral peduncle
- substantia nigra
- tegmentum
- tectum
What does the cerebral peduncle do?
-motor tracts, corticospinal tracts run through pyramidal system
What does the substantia nigra do?
-inhibitory signals to skeletal muscles
What does the tegmentum do?
-sends involuntary motor commands to the erector spinal to maintain posture
What does the tectum do?
-relay station for visual and auditory sensations, visual reflex centers (superior colliculi), auditory reflex centers (inferior colliculi)
What is the pons responsible for?
-regulate rate and depth of breathing, house nuclei for V, VI, VII and VIII
What does the medulla do?
- corticospinal tracts and sensory relay
- nuclei for VIII, IX, X, XI, XII
- also cardiac, vasomotor, respiratory, and those related to coughing, gagging, sneezing, salivation, swallowing, and vomiting
What is the cerebellum responsible for?
- coordinates and fine tunes skeletal muscle movements and ensured that skeletal muscle contraction follows the correct pattern leading to smooth coordinated movements
- performs indirectly with voluntary and involuntary motor pathways
Where is the limbic system?
-ring around the diencephalon
-composed structures that collectively process and experience emotions
+parahippocampal gyrus
+hippocampus (storing memories and long term memory)
+amygdaloid body
+olfactory bulb
+fornix
+various nuclei in diencephalon
What composes sensory pathways?
-have primary neurons, secondary neurons, and sometimes tertiary neurons that facilitate the pathway’s functioning
What composes the motor pathways?
-use upper motor neurons and lower motor neuron
Lateral corticospinal tract
Voluntary limb muscles
Rubrospinal tract
-discrete movement: flexors of limbs
Anterior corticospinal tract
Voluntary: axial muscles
Reticulospinal tract
Posture
Vestibulospinal tract
Balance during movement
Tectospinal tract
Visual and auditory integration with movement
