Chapter 12: The Central Nervous System Flashcards
4 regions of the brain
- Cerebrum: 2 cerebral hemispheres (right & left)
- Diencephalon
- Brain Stem
- Cerebellum: small brain, 2 hemispheres
Brain stem consists of:
- midbrain
- pons
- medulla
Cerebrum surface structures
- gyri; gyrus
- sulci; sulcus
- fissure
Cerebrum surface structures: Gyri
elevated ridges
Cerebrum surface structures: sulci
- shallow grooves
- some sulci are landmarks for dividing each hemisphere into 5 lobes
Cerebrum surface structures: fissure
- deep grooves
- longitudinal fissure: separates right from left hemisphere
- transverse cerebral fissure: separates cerebrum from underlying cerebellum
Hypothalamus
- main visceral control center; vital in maintaining homeostasis
- has many important nuclei: ex. mammillary bodies: acts as olfactory relay station
- primary homeostatic functions: controls ANS, physical response to emotions, body temp, hunger, water balance and thirst, sleep-wake cycle, control endocrine system: produces ADH and oxytocin
Infindulum
stalk at base of hypothalamus that connects to pituitary gland
Thalamus
- 80% of diencephalon
- relay station that sorts info traveling to cerebral cortex, info stored and edited before relayed
- mediates sensation, motor activities, cortical arousal, learning, memory
- involved in memory processing
Medulla Oblongata
- decussation of pyramids
- origin of VII, IX, X, XII cranial nerves
- brain stem: has autonomic reflex center, involved in maintaining homeostasis
- relays ascending sensory pathway impulses from skin and proprioceptors through nuclei cuneatus and gracile
- contains visceral nuclei controlling heart rate, blood vessel diameter, respiratory rate, vomiting, coughing, etc.
Medulla oblongata: Decussation of Pyramids
- spot where pyramidal tracts cross over another to opposite side of body: why each cerebral hemisphere control movement on opposite side of body
Medulla Oblongata: vital centers
- cardiovascular: adjusts rate and force of contractions, vasomotor center changes blood vessel diameter to control bp
- respiratory center: generates rhythm of respiration, controls rate and depth of breathing
- other centers control vomiting, hiccuping,swallowing, coughing, sneezing
Cerebellum
- “small brain”
- processes input from cerebral cortex, brain stem, and sensory receptors to provide precise, smooth, coordinated movements of skeletal muscles
- responsible for balance and posture
Limbic System
- group of medial cerebral hemispheres and diencephalon that collectively work together
- emotional-visceral brain (aka affective brain: responds to perceived threats, express emotion through gestures, resolve mental conflict, attach emotional response to odors
- mediates emotional response
- involved in memory processing
Reticular formation
- groups of nuclei running through central core of brain stem
- governs brain arousal via reticular activating system
- maintains cerebral cortical alertness (RAS)
- filters out receptive stimuli
- helps regulate skeletal and visceral muscle activity
Primary somatosensory cortex
- receives sensory info from the skin and proprioceptors found in skeletal muscle, joints, and tendons: proprioceptors tell the brain the body’s positioning in space
- uses sensory info to identify what part of body stimulated (spatial discrimination)
Primary motor cortex
allows conscious control or precise, skilled, skeletal muscle movement (voluntary muscle control)
Broca’s area: function and location
- typically present only in one hemisphere (usually left)
- motor speech area- controls muscles used in producing speech
- also used when planning/preparing to speak
- control voluntary movements of the eye
Anterior association area
- involved in intellect, cognition (complex learning activities), recall, and personality
- working memory found here: needed for abstract ideas, judgment, reasoning, persistence, and planning
Wernicke’s area: function & location
- posterior association area
- involved in understanding written and spoken language
- if damaged: fail to recognize body on opposite side of damage as part of their body
Commissural fibers: main one and location
main one: corpus callosum commissural fibers that connect 2 hemispheres (center of the brain between right and left hemispheres)
* horizontal
* connect gray matter of 2 hemispheres
Structures protecting the brain
- 3 meninges (connective tissue membranes covering CNS): dura mater, arachnoid mater, pia mater
- cerebrospinal fluid (CSF)
- blood brain barrier
Meninge 1: Dura mater
- “tough mother”
- stronger, most external
- periosteal layer: outer layer, attached to periosteum of skull
- meningeal layer: inner layer, true external covering of brain
- layers fused except at dural venous sinuses between layers
- extends forward, forming partitions (dural septa) that divide cranial cavity
Meninge 3: Pia mater
- “gentle mother”
- delicate layer of connective tissue, most internal
- clings tightly to the brain along every gyrus and down each sulcus
- has numerous tiny blood vessels supplying the brain
Meninge 2: arachnoid mater
- middle meninges layer; subdural space separates arachnoid mater from dura mater; arachnoid granulation (villi) protrude into superior sagittal sinus so CSF can be reabsorbed
- underneath arachnoid mater is subarachnoid space which contains CSF and the largest blood vessels supplying the brain
Formation of CSF
- choroid plexus of each ventricle produces CSF
- CSF flows thru ventricles into subarachnoid space via median lateral apertures
- CSF flows through subarachnoid space
- CSF is absorbed into dural venous sinuses via arachnoid granulations
Blood Brain Barrier: components
- tight junctions: between capillary endothelial cells: most important because they prevent substances from squeezing between endothelial cells, anything crossing the BBB must go thru an endothelial cell
- astrocytes: help maintain tight junctions
- basement membrane: surrounds endothelial cells
Spinal cord: gross anatomy
- spinal dura mater is not fused to vertebrae
- epidural space: between vertebrae and spinal dura. fat padding with network of veins
- CSF in subarachnoid space between arachnoid and pia mater
- dural and arachnoid membranes extend beyond the end of spinal cord at L1/L2 own to S2 of sacrum: lumbar puncture or spinal tap procedure tiste below L1/L2 because no spinal cord here to damage
Spinal cord: where does it begin/end
- end tapers to conus medullaris; cone-shaped structure marking end of spinal cord
- spinal nerves (31 pairs) branch off spinal cord
- spinal cord begins at base of skull at foramen magnum
Spinal cord: cross-section anatomy
- central canal: filled with CSF, runs length of spinal cord
- Gray matter: forms butterfly shape in center
Spinal cord cross-section anatomy Gray matter
- dorsal horn (posterior)
- ventral horn (anterior)
- lateral horns (only in thoracic and lumbar regions)
Cross-section anatomy roots and nerves
- ventral roots: motor neuron axon bundles exiting spinal cord
- dorsal roots: sensory input to spinal cord
- dorsal roots (spinal) ganglia: sensory neuron cell bodies
- spinal nerves: formed by fusion of ventral and dorsal roots
Ascending pathways vs descending pathways: what do they od
conduct sensory pathways superiorly through a chain of 3 neurons to the brain:
first-order neurons
second-order neurons
third-order neurons
First-order neurons
impulses conducted from cutaneous receptors and proprioceptors to spinal cord or brain stem where they synapse with second-order neurons
Second-order neurons
- interneurons
- in dorsal horn of spinal cord or medullary nuclei; axons extend and transmit impulses to cerebellum or synapse with 3rd order neuron in thalamus
Third-order neurons
- interneurons
- cell bodies in thalamus
- axons extend and transmit impulses to somatosensory cortex
- none in the cerebellum
3 pathways that transmit somatosensory info to the brain
- dorsal column-medial lemniscal pathways
- spinothalamic pathways
- spinocerebellar tracts
Dorsal column-medial lemniscal pathways
- impulses relayed through thalamus to somatosensory cortex
- relays discriminative touch, vibration, and info from proprioceptors
Spinothalamic Pathways
- impulses relayed through thalamus to somatosensory cortex
- transmit pain, temp, coarse touch, and pressure
Spinocerebellar tracts
transmit info about muscle or tendon stretch to cerebellum, which then coordinates skeletal muscle activity
