Chapter 9 Flashcards
CNS protected by
Glial cells
Bone- Skull, Vertebrae column
Connective tissue- meninges
Cerebrospinal fluid
100 billion neurons and 100 trillion synapses in CNS
Glial cells types
Schwann cells
Oligodendrocytes
Microglia
Astrocytes (most abundant)
Release growth factors
90% of CNS
Astrocytes
Form a link between neurons and non nervous tissue and ECF
develop neurons and synapses
regenerate damaged axons
Maintain homeostasis in EC envir (K+ levels)
Remove Glutamate (toxic) and biogenic amines from synapses
Synthesize and store molecules
Protect from toxins with microglia
Protect from oxidative stress and remove cellular debris
Microglia
Protect CNS from foreign matter, bacteria or dead cells using phagocytosis or cytokines
Protect against oxidative stress
Physical support of CNS
Cranium (Skull)
Vertebral column
Meninges
Cerebrospinal fluid
Meninges
3 connective tissue membranes:
Dura Mater- outermost, tough like leather
Arachnoid Mater- middle layer, weblike and joined with dura
Pia Mater-right above neurons, subarachnoid space filled with cerebrospinal fluid
*Subarachnoid space- between pia Mater and arachnoid Mater filled with CSF
Cerebrospinal fluid
Surrounds CNS and fills ventricles within brain and spinal cord, provides nutrients and remove waste, Maintains ionic composition
Total volume: 125-150mL recycled 3x a day
Choroid plexus produces 400-500mL/Day
Reabsorbed into venous blood in the subarachnoid space by arachnoid villi
Brain cavities (4)
Two C shaped lateral ventricles, connected to the third ventricle by inter-ventricular foramen.
The cerebral aqueduct connects the third ventricle to the fourth ventricle
*Ependymal cells line ventricles and central canal to help circulate CSF
Central canal
Long thin cylindrical cavity that runs the length of spinal cord, lined with ependymal cells
Choroid plexus
The choroid plexus is a plexus of cells that produces the cerebrospinal fluid in the ventricles of the brain. The choroid plexus consists of modified ependymal cells, pia Mater, and capillaries
CNS Blood Supply
Receives 15% of the body’s blood
High demand for glucose and oxygen 20%
Accounts for 50% of all glucose consumed
During starvation or diabetes mellitus, Ketones can supply energy
Blood brain barrier
Hydrophobic molecules diffuses easily (alcohol, gases)
Hydrophilic molecules rely on transport proteins (ions, catecholamines, amino acids)
Glucose (blood brain barrier)
Glucose transports across barrier using GLUT-1 Carriers
Receptors for insulin are located on certain CNS neurons to regulate food intake
Cannot penetrate blood brain barrier
Catecholamines Inorganic ions (H+) Several drugs (Antibiotics)
No transport carrier for these molecules
Gray matter (cerebral cortex)
40% of CNS, site of synaptic communication and neural integration
Makes up external surface of brain and beneath spinal cord
White matter
60% of CNS, white due to Myelinated axons
Below cerebral cortex, consist of areas of gray matter called subcritical nuclei
Organized into bundles or tracts that connect different regions of gray matter
Projection fibers
Tracts conncet the cerebral cortex with more levels of the brain or spinal cord
Fibers connect one region of gray to another
Association fibers
Connect one area of cerebral cortex to another on the same side of the brain
Arcuate fasciculus- connects broca and wernicks area
Commissural fibers
Connect cortical regions on one side of the brain with corresponding cortical regions on the other side
Located in bands of tissue called corpus callosum which connects the cerebral hemispheres
Spinal nerves
Nerves that branch of spinal cord, 31 pairs that exits the vertebral column between to adjacent vertebrae
Cervical nerves
There are 8 pair (C1-C8) emerge from neck region
Thoracic nerves
12 pairs (T1-12) emerge from chest region
Lumbar nerves
5 pairs (L1-L5) emerge from lower back
Conus medullaris: terminal end of the spinal cord which ends around L1-L2
Sacral nerves
5 pairs (S1-S5) emerge from tailbone or coccyx
Coccygeal nerve
1 nerve (C0) emerges from tip of coccyx
Spinal cord gray matter (Butterfly shaped)
Contains interneurons, cell bodies and dendrites of efferent neurons, and axon terminals of afferent neurons
Dorsal horn- posterior half of gray matter on either side, where afferent neurons terminate
Ventral horn- anterior half of spinal cord
Lateral horn- between dorsal and ventral horns,
origin of efferent neurons
Intermediolateral cell column-between dorsal and ventral horns, efferent neurons originate from autonomic sys
Dorsal root ganglia
Consist of the cell bodies of afferent fibers outside the spinal cord in clusters
Efferent neurons
Located in spinal cord, originate in ventral horn and travel to periphery to form synapses with skeletal muscles
Dorsal roots
Contain afferent axons, come together to form with Ventral roots to form spinal nerves
Ventral roots
Contain efferent axons, come together to form with Dorsal roots to form spinal nerves called mixed nerves
White matter of spinal cord
Surrounds outer region of cord, tracts provide communication at diff lvls in spinal cord or between brain and spinal cord
Ascending tracts- Carry sensory info to the brain (with three neurons), from receptor to the somatosensory cortex. Consist of: Posterior (Dorsal) Column, Spinothalamic Tracts, and Spinocerebellar Tracts.
Descending tracts- Upper motor neurons (that originate in brain) descend through tracts in spinal cord to synapse in the lateral and ventral horns of gray matter to lower motor neurons. Consist of: Pyramidal System and Extrapyramidal System.
*found on both sides of spinal cord, link peripheral nerves to brain
Ipsilateral
When a sensory or Motor pathway remains on the same side as it’s origin
Contralateral
When a sensory or motor pathway crosses to the side opposite of it origin
Brain main parts
Forebrain- superior part of brain, hemispheres, consists of cerebrum and diencephalon (hypothalamus)
Cerebellum- Motor coordination, balance
Brainstem- connect forebrain and cerebellum to spinal cord
Brainstem (3 regions)
3 regions:
Midbrain: Connects forebrain
Pons: middle portion, connects cerebellum
Medulla oblongata: connects to spinal cord
Reticular formation: diffuse network of nuclei that regulates sleep wake cycles, arousal of cerebral cortex, and consciousness
Processing center for 10 of the 12 pairs of cranial nerves, regulates involuntary functions
Cerebral cortex
Carries out the highest level of neural processing. Consist of grooves called sulci and ridges called gyri
1.5mm to 4nm thick
Cortex arranged in 6 layers
Organization or cerebral cortex
Frontal lobe
Parietal lobe
Occipital lobe- visual cortex
Temporal lobe- auditory cortex
Frontal and parietal separated by central sulcus
Occipital and temporal lobe separated by lateral sulcus
Parietal lobe
Primary somatosensory cortex- processes somatic sensory info associated with somesthetic sensations (tough, itch, pain) and proprioception (awareness of muscle tension)
Frontal lobe
Primary motor cortex, voluntary movement, language, planning and personality
Motor homunculus- neural circuits for movement
Sensory homunculus- neural circuits for sensory
topographical organization
Body parts are mapped onto cortical surface which they correspond to called motor or sensory homunculus
Size of body part relative to cortical area devoted to it
Association areas
Involved in more complex processing that requires integrating different types of information
Brain latetization
Certain brain functions are dominant on one side of the brain relative to the other, 2 hemispheres
*Not for every person on same side
Right brain abilities
Movement of left side
Sensory perception of stimuli (left side)
Spatial orientation
Creativity
Face recognition
Music
Dream imagery
Philosophy
Intuition
Left brain abilities
Right side of body
Sensory perception of stimuli (right side)
Logic
Analytical processing
Strong language capabilities
Math skills
Subcortical nuclei
Regions of gray matter located within the cerebrum
Basal nuclei (basal ganglia)
Notable for their role in modifying movement
Caudate nucleus
Globus Pallidus
Putamen
Diencephalon
Inferior to cerebrum
Thalamus and hypothalamus
Thalamus
Cluster of nuclei that functions as relay center before being transmitted to the cortex
Important in directing attention
Relays info from cerebellum and basal ganglia to the motor cortex to provide feedback in controlling movement
Hypothalamus
Located inferior to the thalamus, regulates homeostasis. Link between endocrine and nervous system
Released hormones, hunger and thirst center, thermoregulatory, and behavior
Communicates with autonomic system direct and indirectly
Suprachiasmatic nucleus of hypothalamus
Generates and regulates the circadian rhythm (melatonin)
Limbic system
Brain areas associated with autonomic functions, motivation, memory and emotions
Amygdala, hippocampus, fornix, cingulate, and parahippocampal gyri of cerebral cortex, portions of the prefrontal cortex, thalamus and hypothalamus
Reflex arcs
Neural pathways for reflexes
5 components: sensory receptor, afferent neuron, integration center, efferent neuron, detects a stimulus
Receptor to CNS via afferent neuron to efferent
One single neuron if network of neurons
Reflex groups (5)
Spinal or cranial
Somatic or autonomic
Innate or conditioned
Monosynaptic or polysynaptic
Muscle spindle stretch
Monosynaptic reflex in the human body
Knee jerk reflex- stimulated by patella tendon; contraction of quadriceps inhibits the hamstring by interneurons
Withdrawal reflex
When subjected to painful stimulus and withdraw from it
To occur, The muscles that cause withdrawal should be excited muscles that oppose withdrawal should be inhibited
Info is processed in the brain before the withdrawal and reflex occurs
Pupillary light reflex
Autonomic cranial reflex
Light enters eye->Activate photoreceptors->Activate afferent neurons->info goes to midbrain of brainstem->Efferent neurons smooth muscles of the eye->pupillary constriction
Crossed extensor reflex
When a painful stimulus triggers the withdrawal reflex
(steps on tack)
Nociceptor stimulated->excite afferent neuron->excite interneuron->efferent neuron contracts hamstrings and inhibits/relax quadriceps (withdrawal)->activates crossed extensor reflex on opposite leg (interneurons)-> on opp leg-> causing contraction of quadriceps and inhibit hamstring
Voluntary motor tasks components
Developing the idea to move
Putting together a program of motor commands to carry out the movement
Executing the movement by activating the correct muscles at the correct time
Constant feedback to ensure that the movement is carried out smoothly and successfully
Association areas for movement
Prefrontal cortex, cerebral cortex, basal nuclei, limbic system
Based on sensory input, memories, emotions, or other motivating factors
Lower motor neurons or motor neurons
The afferent neurons that control skeletal muscles originate in the ventral horn of the spinal cord
Lateral pathways or ventromedial pathways
Pyramidal tracts
Direct pathways from the primary motor cortex to the spinal cord. Control movement of distal extremities
Most axons cross over to the opposite side of the CNS in an area of the medulla called the medullary pyramids
Forearms, hands, and fingers, smaller groups of muscles
Upper motor neurons
The axon of neurons from pyramidal tracts that terminates in the ventral horn of the spinal cord
Rubrospinal tracts
Direct pathways from the primary motor cortex to the spinal cord.
Originate in the red nuclei of the midbrain
Axons of these tracts decussate and join axons of the pyramidal tract
Ventromedial pathways
Indirect connections between the brain and spinal cord
These neurons do not form synapses on motor neurons
Influence large groups of muscles, trunk, neck, and proximal portions of the limbs
Vestibulospinal tracts
Originate in the vestibular nuclei of the medulla
Receives info from inner ear regarding movement of the head
Controls head, neck, and lumbar muscles to maintain posture and balance
Tectospinal tracts
Originate in superior colliculi of the midbrain
Receives input from the eyes, somewhat the skin and ears
Control head and eye movement/focus
Reticulospinsl tracts
Originate in reticular formation of pons or medulla
Important for balance
Cerebellum muscle coordination
To operate the cerebellum must both receive information from the cortex regarding planned woodlands and be continually updated about performance
Receives input from sensorimotor areas of cortex, the basal nuclei, brainstem, spinal cord, sensors from all over body
Sends to cortex to adjust planned movement
Basal nuclei motor control
Provide feedback to the cortex for the development of Moter strategies and smoothing out of movements
Necessary for automatic performance of learned repetitive motions
Receive input from cortex and send output back to the cortex via thalamus
Initiates purposeful movement, inhibits unwanted movement
Huntingsons Chorea – lethal genetic disease that causes loss of motor coordination and decline of cognitive f(x) until dementia, twitching face
Wernickes area
Located in the posterior and superior portion of the Temporel lobe and the inferior parietal lobe
Involved in language comprehension
Sound, written words, or hand signals
Broca’s area
Located in frontal lobe
Involved in language expression our ability to speak or right
Kinds of sleep
Slow wave sleep (SWS)- multiple stages of low frequency waves in EEG
REM sleep- hit frequency waves in EEG and periodic episodes of rapid eye movement
Ascending reticular activating system (ARAS)
Critical in maintaining alert wakefulness
Send info to cortex thru thalamus, hypothalamus, and forebrain
Neurotransmitters: acetylcholine, norepinephrine, and dopamine
Nicotine, orexin, histamine amphetamines and cocaine
Wake and alert
EEG shows high frequency low amplitude
Beta waves
Awake but resting
EEG of lower frequency and higher amplitude
Alpha waves (greater synchronization among neurons vs beta)
SWS stages
Stage 1: drowsey period (asleep and awake)
Stage 2: light sleep
Stage 3: moderate sleep
Stage 4: deep sleep
Cortisol
Helps the body adjust to stress by mobilizing energy stores, even at the expense of breaking down so proteins to amino acids
Emotions
Cerebral cortex, limbic system, and hypothalamus (anger, aggression), Amygdala (Fear, anxiety)
Triggered by sensory input or memories
Autonomic, Motor, and hormonal changes
Left brain: positive emotion
Right brain: negative emotion
Procedural memory (implicit memory)
Memory of motor skills and behaviors
Includes cerebellum, basal nuclei, and pons
Ex. Learning to ride a bike, you never forget
Declarative memory (explicit memory)
The memory of learned experiences
Ex. facts and events
Plasticity
The ability to alter the nervous systems anatomy and function in response to changes in it’s activity patterns
Synapses can be developed and altered
New neurons in areas of memory
Long term potentiation
Repetitive stimulation of a particular synapse leading to increased and the strength of that connection. Better able to trigger a action potential in the postsynaptic cell caused by an increase in the size of EPSPs
Hippo campus and occurs at preexisted synapsis
Multiple sclerosis
Autoimmune disorder, stops neural signals, muscle weakness and balance problems
Treatment: corticosteroids, interferons, immunosuppressants
Alzheimer’s disease
Decrease in the #of cholinergic neurons, microglia and astrocytes release inflammatory chem, causes memory loss and confusion, Motor dysf, loss of cognitive f(x)
Treatment: antioxidants, acetylcholinesterase inhibitors, Antidepressants
Parkinson’s Disease
Decrease in dopaminergic neurons in the substantia Niagra, causes movement disorders
Treatment: Levodopa, COMT inhibitors, Surgery
Analysis of CSF
Tested by extracting between L3 and L4
Cloudy CSF: Bacterial meningitis, Viral meningitis, Fungal meningitis(HIV), Tuberculosis meningitis, neurosyphilis, neoplasm (growth)
Red CSF: intracranial hemorrhage
Analyzed: Glucose, protein, leukocytes, RBCs, Pressure
Flow of CSF
1) Lateral ventricle
2) Interventricular Foramen
3) Third Ventricle
4) Central aqueduct
5) Forth Ventricle
6) through foramen of luschka (lateral hole)
7) Up cross cerebral hemisphere and down spinal cord
8) enters subarachnoid space is reabsorbed in arachnoid villi —> then taken to heart via jugular vein
Intracranial hypotension
CSF Leakage caused by tear in Dura by head brain or spinal injury, bad placement of tubes ex. Epidural, spinal tap (lumbar puncture)
Symptoms: runny nose, ear leak, bad headache when sitting up
Testing: MRI, X Ray with contrast
Assessing brain death
1) Pupillary reflex
2) Response to pain
3) Respond to sound
4) Ability to breathe w/o the ventilator
Amyotrophic Lateral Sclerosis (Lou Gehrig’s Disease)
Neurons die
Causing muscle weakness, paralyzed body, breathing and swallowing affected first, does not affect special senses
Symptoms begin age 50
Stephen Hawking
Control of Posture
Extrapyramidal tracts – include all motor control pathways outside the pyramidal system. Indirect conections b/w the brain and spinal cord.
Involuntary control of posture: Muscles constantly adjust changes in posture standing still or moving.
•Postural control, Brain uses info from sensory, propioceptors in muscles and joints and receptors in the vestibular system (inner ear that detect motion of the head).
•Brain also uses info from eyes and ears.
