Lecture 2 Anatomy (CNS Overview) Flashcards
What is the brain made up of?
100 billion neurons
1 trillion neuroglia
-Neurons are primarily interneurons (associative) involved in associative function (intellect, emotions, behavior, and memory)
Brain development:
Describe the stages -
Ectoderm -> neural fold -> neural tube -> 3 primary vesicles -> 5 secondary vesicles
5 Principle parts of the brain (derived from secondary vesicles):
- Telencephalon - cerebral hemispheres, basal ganglie, limbic system
- Diencephalon - thalamus, hypothalamus, epithalamus
- Mesencephalon (midbrain) - cerebral peduncles, corpus quadrigemina
- Metencephalon - cerebellum, pons
- Myelencephalon - medulla oblongata
Brain stem (parts):
- Medulla oblongata (myelencephalon)
- Pons
- Midbrain (mesencephalon)
Protective covering of brain:
Start with scalp -
1. Scalp - skin, CT, aponeurosis, lipid, and periosteum 2 Cranial bones (skull) 3. Epidural space with far 4. Dura matter 5. Subdural space - with interstitial fluid 6. Arachnoid mater 7. Subarachnoid space - with CSF 8. Pia matter
Folds of the dura matter (hold brain in place)
Falx cerebri -
Falx cerebelli -
Tentorium cerebelli -
Falx cerebri - sagittal between cerebral hemispheres
Falx cerebelli - sagittal between cerebellar hemispheres
Tentorium cerebelli - transverse between cerebrum and cerebellum
What is brain’s normal fuel source and how much does it use during rest?
Glucose (unable to store)
Uses 20% of bodies oxygen and glucose
Blood brain barrier composed of 3 parts:
- Tight junctions between blood vessel endothelial cells
- Continuous endothelial cell basement membrane
- Astrocytes (neuroglia) wrapped around endothelial cell basement membrane
What can/can’t cross BBB?
Not found in which organs (give general name and name 3 organs)?
Can - lipid soluble, hydrophobic substances Can't - Water, hydrophilic substances Circumventricular organs: 1. Hypothalamus 2. Pituitary 3. Pineal Gland
Medulla Oblongata (Myelencephalon): Overall Functions -
- Contains nuclei for vital centers and cranial nerves
2. Signal Propagation via ascending (sensory signals) and descending (motor signals) tracts
Medulla Oblongata (Myelencephalon): Nerve tracts -
Nerve tracts - (bundles of axons) both sensory (ascending) and motor (descending)
Medulla Oblongata (Myelencephalon): Pyramids -
Pyramids - paired ventral surface ridges that contain motor descending tracts
Medulla Oblongata (Myelencephalon): Decussation of pyramids -
Decussation of pyramids - motor tracts from the right brain cross to control muscles on the left side and motor tracts from left brain cross to control muscles on the right side
*motor
Medulla Oblongata (Myelencephalon): Olives -
Olives - paired bulges lateral to pyramids which contain the inferior olivary nuclei which links brain and spinal cord motor signals to the cerebellum for perception of time
Medulla Oblongata (Myelencephalon): Fasciculus gracilis and fasciculus cutaneous -
Fasciculus gracilis and fasciculus cutaneous - ridges found on dorsal medulla which relay sensory ascending input to opposite side of the brain
Medulla Oblongata (Myelencephalon): Decussation of the medial lemniscus -
Decussation of the medial lemniscus - crossover of ascending sensory input to the contralateral brain hemisphere
*sensory
Medulla Oblongata (Myelencephalon): Nuclei
Nuclei - masses of neuronal cell bodies
- Vital body functions: cardiovascular, respiratory
- CN nuclei for CN 8, 9, 10, 11, & 12
Pons: Where is it found? What part of brain is it? Contains - Functions -
- Found on ventral surface of brain stem
- Apart of metencephalon with cerebellum (which is not apart of the brain stem)
Contains - CN nuclei 5, 6, 7 and ascending and descending tracts
Functions - information relay for cerebellar hemispheres
Midbrain:
Where is it found?
What CN?
- Mesencephalon
- CN 3, 4
Midbrain:
Superior colliculi -
Superior colliculi - reflex movement of eye, head, and neck to visual and other stimuli
Midbrain:
Inferior colliculi -
Inferior colliculi - reflex movement of head and neck to auditory stimuli
Midbrain:
Cerebral peduncles -
Cerebral peduncles - contain descending motor axon tracts from cerebral hemispheres to spinal cord, medulla and pons
-Ascending sensory axons going to cerebrum
Midbrain:
Cerebral peduncles -
Cerebral peduncles - contain descending motor axon tracts from cerebral hemispheres to spinal cord, medulla and pons
-Ascending sensory axons going to cerebrum
Midbrain:
Red nucleus and substantia nigra -
Red nucleus and substantia nigra - function to modify motor signals
Functions of the midbrain?
- Relay motor impulses from cerebral cortex
1. Relay sensory impulse from spinal cord to thalamus
Reticular (net) formation -
Diffuse structure, composed of areas of gray matter interspersed among areas of white matter in central portions of diencephalon, brain stem, and spinal cord
Reticular functions -
- Alerting cerebral cortex to sensory signals
- Reticular activating system function in maintaining consciousness and awakening from sleep by stimulating the cortex
- Filter sensory input to remove unimportant input (prevent sensory overload)
- Efferent motor function in maintaining muscle tone
Cerebellum:
What part of brain?
Compose of?
-Metencephalon with pons Composed of: 1. Vermis (worm) which splits the two hemispheres 2. Cerebella hemispheres 3. Peduncles
Cerebellum: Cross section anatomy Cortex - Folia - Arbor vitae nerve tracts - Cerebellar nuclei -
Cortex - gray matter
Folia - ridges
Arbor vitae nerve tracts - white matter
Cerebellar nuclei - gray matter within arbor nuclei
Cerebellar Functions:
- Smooth and coordinate cerebral control of skeletal muscle movements to facilitate complex muscle activity
- Regulate muscle tone
- Posture and balance
Diencephalon:
Composed of -
- Not part of brainstem Composed of: 1. Thalamus 2. hypothalamus 3. Epithalamus 4. Subthalamus
Diencephalon:
1. Thalamus
What is it composed of?
What are functions?
- Composed of paired masses of mixed gray nuclei and white tracts connected by intermediate mass (crossover point)
Functions: - Sensory (visual, auditory, smell, taste, somatic sensation) relay to the correct region of the cerebral cortex
- Refine motor signals with the basal nucleus
Diencephalon:
2. Hypothalamus
Function (general) -
Composed of -
- Function: maintain homeostasis
- Circumventricular organ
Composed of: - mammillary bodies visible on inferior surface
-infundibulum connects pituitary (hypophysis) to the hypothalamus
Diencephalon:
2. Hypothalamus
Specific Functions -
- Control of autonomic nervous sustem (heart, gut, bladder)
- Control endocrine system - control pituitary
- Regulate emotional behavior (limbic system)
- Regulate eating and drinking
- Control body temp
- Regulate circadian rhythms and state of consciousness
Diencephalon:
3. Epithalamus
Composed of -
Functions -
Composed of:
1. Pineal gland - endocrine gland secretes melatonin
2. Habenular nuclei (paired)
Functions:
1. Pineal gland melatonin production to set biological clock
2. Habenular - emotional response to smell
Diencephalon:
4. Subthalamus
Composed of -
Functions -
Composed of: 1. Subthalamic nuclei 2. Parts of red nuclei 3. Parts of substantia nigra Functions: 1. Connects to cerebellum and motor cortex for control of body movements
Circumventricular Organs:
What are they?
Function?
Name the 3
- Areas of brain that do not have BBB therefore are able to monitor chemical changes in blood
- Function as part of body’s internal sensory system to maintain homeostasis
- Hypothalamus, pineal, pituitary (hypophsysis)
Basal Ganglia:
What part of brain?
What does is consist of?
Function?
- Telencephalon
- Consists of paired nuclei (gray matter)
- Function in control of skeletal muscle movement (motor neuron) and muscle tone
Limbic system:
What part of brain?
Composed of what?
Describe what it is
- Telencephalon and Diencephalon
- Composed of paired nuclei, tracts, and cortex (parts of frontal/parietal/ and temporal lobes)
- Primitive brain function in emotional aspects of behaviors and memory/pain, pleasure, affection, and anger to determine feelings
Cerebrum:
Composed of -
-Telencephalon
Composed of:
1. Cerebral cortex (gray matter) - 10s of billions of associative (inter) neurons typically arranged in 6 layers to allow vertical integration
2. Cerebral white matter containing 2 types of neurons:
-Association fibers - connect diff gyri in same hemi
-Commissural fibers - connect diff gyri in opposite hemi
-Projection fibers - connect cerebrym to rest of body (sensory/motor)
Cerebrum:
Functions
- Conscious sensation (receive conscious sensory input)
- Voluntary motor activity (sends voluntary motor output)
- Higher brain function (cognition, association of sensory input with memory to produce more memory, language, abstract thought - humanity)