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92 Cards in this Set

  • Front
  • Back
Give a definition of "Nervous System"
A collection of tissues and their cell processes (nerves) that collect info from external/internal environment, analyze and store info, and provide appropriate responses that promote survival of the organism
How is the CNS protected?
1. Brain and spinal cord = within cranium and spinal canal and covered by 3 sheets of tissue (meninges)
2. tight juctions b/w endothelial cells of blood vessels in brain form blood-brain barrier
3.Cerebrospinal fluid within the ventricles of the brain that flows down to brainstem and exits to bathe the external surface of the brain
What is the "Blood-Brain Barrier"
-Tight juctions that seal together endothelial cells of brain capillaries
-thick basement membrane around the caps
What structure is responsible for the production of cerebrospinal fluid
-choroid plexus = networks of capillaries in walls of ventricles
-caps covered by ependymal cells that form CSF from blood plasma by filtration and secretion
How does the CSF protect the brain?
-Protects brain from mechanical shock
-Draws away metabolic breakdown products (waste)
How much CSF flows and is resorbed?
480ml per day
What is the function of the blood CSF barrier?
-Prevents passive diffusion of solutes from blood into the CSF
Where is the CSF absorbed?
-CSF absorbed into venous blood through the arachnoid granulations
-arachnoid granulations protrude from thin 2nd covering of brain (arachnoid) and extend to venous sinus of brain, allowing CSF to exit into bloodstream
What makes up the central nervous system?
brain + spinal cord
What makes up the peripheral nervous system?
1.nerves (and ganglia) carrying info from limbs (afferent)
2.nerves carrying info to muscles to control movement (efferent)
3.nerves + ganglia of autonomic NS
4.nerves + ganglia of enteric NS controling gut function
Where does the spinal cord lie, and how/what is it connected to?
-Spinal cord lies within spinal canal of the vertebral column (spine)
-spinal cord is connected by nerves to limbs and torso
What types of tissue are contained in the spinal cord
1.White matter = forms external part of cord (myelinated axons, thus white)
2.Gray matter = forms butterfly shaped inner core (neuron cell bodies, dentrites, synapses)
In which type of matter (white or gray) does axonal conduction take place in?
White matter (contains axons carrying info up and down axis of spinal cord)
In which type of matter (white or gray) does neurotransmission take place in?
Gray matter
How do action potentials (info) enter the spinal cord?
via spinal nerves
How many nerves are there per spinal vertebra?
one pair
What are spinal nerves?
-Mixed nerves carrying sensory info to the spinal cord and motor information from the spinal cord to muscle nerves
What do nerves from lower regions (caudal end, lumbar region) of spinal cord innervate?
Lower limbs
What do nerves in mid regions (thoracic regions) of spinal cord innervate?
chest + abdomen
What do nerves of upper part (cervical) of spinal cord innervate?
upper limbs
What requires more sensory and motor axons, chest + abdomen OR lower + upper limbs
-Upper and lower limbs require more sensory and motor axons
(For this reason, spinal cord is larger in lumbar and cervical regions than thoracic region = cervical + lumbar enlargements)
What is longer, the vertebral column or the spinal cord?
-Vertebral column is longer; spinal cord ends @ L1 and the lumbar nerves descend within a CSF filled sac
What makes up the CSF filled sac?
Meninges = the layer of membrane covering the brain and spinal cord form walls of sack and trap the fluid
What is the lumbar cistern?
-Fluid space caudal to end of spinal cord
(point that CSF can be sampled using lumbar puncture = spinal tap)
What do the nerves split into when they reach the spinal cord?
dorsal (posterior) root + ventral (anterior) root
What does the dorsal root contain?
sensory axons of the mixed nerve
What does the ventral root contain
motor axons of the mixed nerve
Where does the dorsal root connect to the spinal cord?
At the dorsal horn of the gray matter
What is the dorsal horn of the grey matter and what does it contain?
Dorsal horn = sensory part of the gray matter of the spinal cord
-Contains synaptic terminals of some sensory axons of the nerve and cell bodies and dentdrites of the neurons that will send projections to the brain
What is the ventral horn and what does it contain?
Ventral horn= motor part of the spinal gray matter
-Contains cell bodies of motor neurons which will innervate muscle and activate neuromuscular junction to cause muscle contraction
Explain the withdrawal reflex.
-touch hot object, pain fibers (axon) send series of APs to dorsal horn of spinal cord
-nerve terminal of these axons contact dendrites of motor neurons; motor neurons innervate muscle gr. causing arm to flex from source
Where do the axons contained in the white matter project to?
From the spinal cord to the brain
From the brain to the spinal cord
What are tracts?
Bundle of axons w a similar function (starting pt and end pt)
What is the corticospinal tract
-Important descending tract found in lateral white matter
-carries the axons of neurons in the cerebral cortex that project down to the spinal cord
-Innervate ventral horn to control movement
What is the dorsal column and what does it contain?
-White matter found in between the two dorsal horns
-Contains axons of sensory neurons that DONT synapse in the dorsal horn but instead project to brain stem to synapse
what is the foramen magnum and what happens @ this structure?
-foramen magnum = big hole @ base of skull
-spinal cord merges w caudal part of brain stem
Whats parts is the brain composed of?
What is the conscious decision-making part of the brain?
What is the gateway for sensory information in the brain?
What part of the brain exerts fine control over motor function?
What part of the brain carries info to and from sipinal cord and also controls motor and sensory function of head + neck?
brains stem
How does the brainstem connect to the spinal cord and to the diencephalon?
-brainstem connects to the spinal cord @ its caudal end (tail)
-brainstem connects to diencephalon @ its rostral end (beak)
What does the brainstem consist of ?
1. Medulla Oblongada (caudal)
2. Pons (middle)
3. Midbrain (rostral)
What is superior to the brainstem? What is posterior?
Superior = Diencephalon
Posterior = Cerebellum
What does the diencephalon consist of?
1. Thalamus
2. Hypothalamus
3. Epithalamus
What structure is supported on the diencephalon?
What is the purpose of the BBB?
-blood brain barrier protects brain cells from harmful substances and pathogens
-prevents passage of many substances from blood into brain tissue
Name a few substances which cross the BBB by active transport.
-a few water soluble substances ex. glucose
Name a few substances with cross the BBB very slowly.
-Urea, creatinine, most ions
Which substances do not cross the BBB (from blood to brain tissue) at all?
-proteins and most antibiotic drugs
What substances easily cross the blood-brain barrier?
Lipid soluble substances such as oxygen, carbon dioxide, alcohol, most anesthetic agents
How does the cerebral spinal fluid contribute to homeostasis?
1. Mechanical protection (shock absorbing medium)
2. Chemical protection (provides optimal chemical env for neuron siganaling)
3. Circulation (allows exhange of nutrients & waste b/w blood and nervous tissue)
How is the blood-cerebrospinal barrier formed?
-Ependymal cells covering caps of choroid plexuses are joined by tight juctions
-Thus, materials entering CSF from choroid caps cannot leak b/w these cells
-Must pass through ependymal cells
Name a few structures contained in the brainstem spinal cord
1. Inputs and outputs (cranial nerves)
2. ascending and descending axon tracts that pass through it
3. Collection of neurons (or nerve cell bodies) that process info and perform functions
What tracts are found in the medulla?
-Ascending tracts like the dorsal columns (sensory)form synapses in medulla
-Descending tracts like the corticospinal tract (motor)
What are some of the functions performed by neurons found in the medulla?
-control of breathing and vomitting
What are the inputs/outputs found in the medula?
-Cranial Nerves
Compare spinal and cranial nerves.
-Spinal nerves carry sensory & motor info from sacrum and coccyx to the level of the neck (upper cervical nerves)
-Above this level, in region of head and face, nerves enter the cranium rather than spinal cord = cranial nerves
How many cranial nerves are there?
12 pairs
What are pyramids?
-Part of medulla; bulges formed by large corticospinal tracts that pass from cerebrum to spinal cord
What is the "decussation of pyramids" and what are its implications?
-90% of axons in left pyramid cross to right side (vice versa)
-Cortex on right side of brain send and receives info from left side of body (vice versa)
What happens @ the dorsal column nuclei?
-Sensory axons that do not synapse in the spinal cord dorsal horn ascend the spinal cord in the dorsal column nuclei and synapse there, in the medulla
What are cranial nerve nuclei?
-Are nuclei (collection of cell bodies) that receive sensory info from cranial nerves
-OR are collections of motor neurons that send out info to muscles of the head and face
What are the pons?
Bridge that connects parts of the brain with one another (medulla + midbrain)
What kind of structures are contained in the pons?
-Inputs and outputs (some cranial nerves)
-ascending and descending axon tracts passing through it
-collection of neurons (or nerve cell bodies)
What structure is the upper part of the brainstem?
What structures are contained in the midbrain?
-Inputs and outputs (some cranial nerves)
-Ascending and descending axon tracts passing through it (some which form synaptic terminals
-Collection of neurons (or nerve cell bodies) that process info and perform functions
What are some of the notable anatomical structures in the midbrain?
1. Cerebral peduncles
2. Medial lemniscus
3. Superior (and inferior) colliculus
4. Substantia nigra
What are the cerebral peduncles?
-pair of tracts
-contain descending corticospinal fibers (conduct nerve impulses from cerebrum to spinal cord)
What is the medial lemniscus?
-large bundle of heavily myelinated ascending sensory fibers
What is are superior colliculi?
-serve as reflex centers for some visual activities
What are the inferior colliculi
-part of the auditory pathway
-relay impulses from the receptors for hearing in the ears to the thalamus
What is the substantia nigra?
-very important nuclei for motor control
What are the 2 parts of the diencephalon?
1. Thalamus
2. Hypothalamus
In a sentence, describe the role of the thalamus.
-Thalamus = part of the brain that recieves synapses from all ascending sensory innervation and sends projection to the appropriate part of the cerebral cortex
The thalamus is said the be the gateway to the cortex for all sensations except for one. Which one?
How many cranial nerves enter @ the level of the diencephalon? Name them.
-Only one cranial nerve enters @ level of diencephalon = optic nerve carrying visual sensory info
What is the role of the hypothalamus?
-Hypotalamus = high command center for homeostasis within the brain
-Controls BP, body temp, blood glucose, and other housekeeping functions
Where do ascending and descending info within the diencephalon travel?
-In axon tracts within the internal capsule
What 2 structures compose the cerebrum?
1. Cerebral cortex
2. Basal Ganglia
What is the cerebral cortex?
-Outer coating of "brain"
-Gray matter of cerebral cortex is outside, white matter inside (inverse of spinal cord)
Describe the spacial arrangement of the cortex
-Cortex is convoluted into ridges called gyri and folds called sulci
Why is the cortex convoluted?
To increase surface area in a small space
What are the main roles of the cerebral cortex?
-Cortex receives and perceives sensory input
How does the cerebral cortex make sense of the sensory input received?
-Relative to past experience (memory and sends out appropriate response commands)
What are lobes?
Territories into which is organised the cerebral cortex
How many lobes are found in the cerebral cortex and what are they?
- 4 lobes
1. Frontal lobe
2. Parietal lobe
3. Occipital lobe
4. Temperal lobe
What is the frontal lobe?
-Site of motor commands that are sent out to the brainstem and spinal cord
What is the parietal lobe?
-Site of receipt of sensory info for pain, temperature, touch and pressure
What is the occipital lobe?
-Site of receipt of visual information
What is the temperal lobe?
-Site of receipt of auditory info
Briefly, what is the basal ganglia?
-Part of cerebrum lying deep to the cortex and its underlying white matter
-Large collections of neuronal cell bodies that are important in motor function