Chapter 7: The Structure of the Nervous System Flashcards
What does brain organization follow?
The mammalian plan
What are the nervous system divisions?
Cerntral Nervous System (CNS) and Peripheral Nervous System (PNS)
Ipsilateral v. Contralateral
Ipsilateral is same side, while contralateral is opposite sides
What are the anatomical plans of section?
Midsagittal, horizontal, coronal
What is the CNS encased in?
Bone
What is the cerebrum?
-Largest part of the brain
-2 Hemispheres
-Sensations and movement
-Right side controls left side of body
-Left side controls right side of body
What is cerebellum?
-Latin for “little brain”
-Same number of neurons as cerebrum
-Movement control center
-Right side controls the right side of the body
Brain Stem
-Relay nerve fibers
-Vital functions-breathing, consciousness, body temp,
-Damage is usually fatal
Spinal Cord
-Attached to the brain stem
-Major conduit of information from skin, joints, muscles to brain and vice versa
How does the spinal cord communicate?
Via spinal nerves (PNS)
Dorsal root
Sensory info. to the spinal cord
Ventral Root
Motor info. from the spinal cord
Somatic PNS
Under voluntary control, innervates skin, joints, muscles
Somatic Motor Axons
Innervate muscle (NMJ)
Somatic Sensory Axons
Dorsal root ganglia
Dorsal root ganglia
Clusters of neuronal cell bodies outside the spinal cord
Visceral PNS/Autonomic nervous system
-Involuntary vegetative
-Innervates internal organs, blood vessels, glands
-Non-voluntary emotional reactions like butterflies in stomach/blushing
Visceral Sensory
Blood pressure, oxygen content in blood
Visceral motor: contraction/relaxation of:
-Smooth muscle in walls of intestines and blood vessels
-Cardiac muscle
-Secretory function in glands
Afferent
(“Carry to”) Carry information toward a particular point
Efferent
(“Carry from”) Carry information away from a point
The Cranial Nerves
-12 nerves from brain stem (Numbered anterior to posterior
-Mostly innervate the head
-Some are axons from CNS, somatic PNS, or visceral PNS
Meninges
-Greek for “covering”
-3 membranes that surround the CNS
Dura Mater
-Latin for “hard mother”—leather-like consistency
-Tough, inelastic bag
Arachnoid Membrane
-Greek for “spider”
-Subdural hemtoma (bleed) in the subdural space compresses brain and disrupts function (drill/drain)
Pia Mater
-Latin for “gentle mother”
-Thin membrane that adheres to the brain’s surface
-Blood vessels that innervate the brain
-Seperated from arachnoid by fluid-filled space=subarachnoid space
Ventricles
Cerebrospinal fluid (CSF)-filled caverns and canals inside brain
Choroid Plexus
Specialized tissue in ventricles that secretes CSF
How does CSF moves through the ventricles?
It circulates through the ventricles and exits into aubarachnoid space through apertures (small openings) and is absorbed by the blood vessels: arachnoid villi
Hydrocephalus
-“Water on the brain”
-Flow of CSF is impaired so ventricles swell and compress CNS
What is the treatment of hydrocephalus?
Inserting a tube into the ventricle to drain off excess fluid into peritoneal cavity
The direction closest to the rat’s nose traveling from the tail up through the spinal column is called
Rostral
What part of your brain functions as the movement control center?
Cerebellum
Which part of the nervous system is responsible for the feeling of butterflies in your stomach?
Autonomic NS
Which of the meninges derives its name from the Latin phrase for hard mother?
Dura mater
What term means water on the brain?
Hydrocephalus
Which technique measures activity in the brain by comparing the oxygenation levels of hemoglobin?
fMRI
From which part of the neural tube does the nervous system originate?
Ectoderm
The hindbrain is also called the
Rhombencephalon
What is the axonal bridge that links the 2 cerebral hemispheres?
Corpus Callosum
Bumps on the surface of the cerebral cortex are called
Gyri
Describe the CLARITY method and why it’s used
-It renders tissue optically clear
-Replaces light-absorbing lipids w/ water soluble gel
-Used for seeing flourescently-labeled cells
CT
-Generates image of brain slice
-X-ray beams used to generate data for digitally reconstructed image
MRI
-Hydrogen atoms respond in the brain to perturbations of a strong magnetic field
-More detail, doesn’t need X-irradation
-Brain slice image in any plane
Diffusion Tensor Imaging
-Visualizes large bundles of axons
-Compares position of hydrogen atoms in water molecules over time
-Water diffuses more readily alongside axons than across them
Positron Emission Tomography (PET)
-Radioactive solution in blood stream emits positrons
-Measures metabolic brain activity
-Disadvantages: Spatial resolution is 5-10 nm, radiation exposure, 1 scan may take several minutes
fMRI
-Detects increased neuronal activity by measuring the ratio of oxyhemaglobin to deoxyhemoglobin
-More activity means more donated oxygen
-Advantages over PET: Rapid scans (50 msec), Good spatial resolution, noninvasive, no radiation
What does the CNS form from?
The walls of a fluid-filled neural tube
Endoderm
Lining of many internal organs
Mesoderm
Bones and muscles
Ectoderm
Nervous system and skin
—>Neural plate: nervous system
Neurulation
Neural plate becomes the neural tube
Neural groove forms:
Groove in the neural plate, runs from rostral to caudal
What forms from the walls of the groove?
Neural folds, which fuse to form the neural tube
What does the neural tube form?
The entire CNS
Neural crest
Some of neural ectoderm is pinched off and lies just lateral to the neural tube
Somites
-Mesoderm forms bulges on either side of the neural tube
-Forms spinal vertebrae, skeletal muscle
Somatic Motor Nerve
Nerves innervating the skeletal muscles
Anencephaly
-Anterior failure to close
-Degeneration of forebrain and skull
-Fatal
Spina Bifida
-Posterior failure to close
-Most severe: Posterior spinal cord may fail to form
-Less severe: Defects in meninges/vertebrae
-Requires extensive and costly medical care
How can you prevent a large number of neural tube defects?
Vitamin folic acid
What are the 3 primary vesicles of the neural tube?
Prosencephalon, mesencephalon, rhombencephalon
Prosencephalon
-Pro is Greek for before, encephalon for brain
-Forebrain
Mesencephalon
-Midbrain
Rhombencephalon
-Hindbrain
-Connects to caudal neural tube, which forms the spinal cord
Differentiation
Process by which structures become complex and specialized
Optic Vesicles
-Grow and invaginate to form the optic cups (retina) and optic stalk (optic nerve)
—>Retina and optic nerve are part of CNS
What is produced from the telencephalic vesicles?
Telencephalon (end brain)
Diencephalon
“between brain”, is in the middle
Telencephalon
Cerebral hemispheres, olfactory bulbs, basal telencephalon
How do telencephalic vesicles grow?
Posteriorly, over and lateral to the diencephalon
Where do olfactory bulbs sprout off of?
The Ventral surface
Diencephalon
Thalamus and hypothalamus
Cortical white matter
Axons to/from cerebral cortex
Corpus callosum
Axonal bridge b/t cerebral hemispheres
Internal capsule
Links the cortex w/ the brainstem/thalamus
Cerebral Cortex
-Analyze sensory input and command motor output
-Conscious awareness, cognition, perceptions
-Info. from the senses gets sent to the cortex
Thalamus
-Gateway to the cortex
-Vision, audition, somatic sensation synapse in thalamus before cortex
Voluntary movement
-Corticospinal tract
-Basal ganglia
Corticospinal Tract
Axons form cortex directly to spinal cord
What do axons from thalamus to cortex, or cortex to thalamus pass through?
The internal capsule
How do axons carry information?
Contralateral side of the body
How does hypothalamus control visceral nervous system?
-Fight/flight response
-Controls ANS: HR, BP
-Controls body temp.
-Motivates animals to find food/drink/sex in response to needs
-Directs pituitary to release hormones
Amygdala
-Fear conditioning
-Memory
-Emotional responses
What does the dorsal surface become?
Tectum
Superior colliculus/optic tectum
-Direct input from eye
-Controls eye movements
-Cranial nerves III and IV
Inferior Colliculus
Direct input from ear, sends to thalamus
Cerebral Aqueduct
-Contains CSF
-Connects rostrally w/ the 3rd ventricle
Corticospinal Tract
-Info. conduit from spinal cord to forebrain and vice versa, sensory systems, control of movements
-Damage causes impairment on contralateral side
What does the floor of the midbrain become?
Tegementum
Substantia Nigra
-Black substance; neuromelanin in dopaminergic neurons
-Control of voluntary movement
Red Nucleus
-Pale pink (iron)
-Control of voluntary movement
Mentecephalon
Rostral
Cerebellum
-Movement control center —> coordination
-Inputs from spinal cord and pons (goals from cortex)
Pons
-Latin for “bridge”
-90% of descending axons from midbrain synapse here
-Relay info to cerebellum
Myelencephalon
-Caudal
-Medulla oblongata
Is there a 4th ventricle?
Yes
Rostral development
Rhombic lip along dorsal-lateral wall grows dorsally and medially
—>fusion into cerebellum
The ventral and lateral walls swell to form?
Medulla
Cochlear Nuclei
-Hearing
-Axons of auditory nerves synapse here
-Send axons to inferior colliculus and others
-Damage lead to deafness
Touch
Somatic sensory information from spinal cord to thalamus
Taste
From tongue to thalamus
-Cranial nerve XII: Tongue motor neurons
Medullary pyramids
-White matter tracts
-Axons don’t synapse in pons
-Most from cortex (CST)
Pyramidal Decussation
Axons cross to the other side of the midline
What does the ependymal layer form?
Roof of the 4th ventricle
Caudal neural tube expands to form?
Spinal cord
Does the spinal canal contain CSF?
Yes
What does the cross section of the differentiation of the spinal cord look like?
Has a gray matter butterfly appearance
Dorsal horn
-Upper part of butterfly wings
-Recieve sensory input from dorsal root fibers
Ventral Horn
-Lower part of butterfly wings
-Motor neurons project axons to muscle
Intermediate Zone
-In b/t dorsal horn and ventral horn
-Interneurons that shape motor outputs in response to sensory inputs and descending outputs from the brain
What does the white matter consist of?
Dorsal columns, lateral columns, ventral columns
Dorsal Columns
-Somatic sensory (touch) information toward the brain
-Descussate (cross) and synpase in medulla —> right brain feels left body
Lateral Columns
-Descending corticospinal tract (CST;voluntary movement)
-Cross in medulla
-Innervate intermediate zone and ventral horn
Spinal Cord Function
-Relay information from skin, joints, muscles to brain and vice versa
-Beginning analysis of sensory information
-Coordinating movements
-Simple reflexes
What are the differences in rat and human brains?
Sulci and Gyri, smaller human olfactory bulb, growth of cerebral hemisphere: temporal, frontal, parietal, occipital
Sulci
Grooves
Gyri
Bumps
What do the sulci and gyri do for the human brain?
Increased surface area of the brain
Temporal lobe
Hearing
Frontal lobe
Executive function/memory/motor function/etc.
Central sulcus
Posterior border of frontal lobe
Parietal lobe
Sensory/language
Occipitial lobe
Vision
What are common features of the cerebral cortex in vertebrates?
- Cell bodies in layers/sheets parallel to surface of brain
- Surface layer separated from pia mater, layer I or molecular layer
- Large apical dendrites from pyramidal cells form multiple branches in layer I
Hippocampus
-Greek for “seahorse”
-Single layer of cells, folded
-Limbic system
-Learning and memory
Olfactory cortex
-2 cell layers
-Continuous w/ olfactory bulb
Neocortex
Found only in mammals
What separates olfactory cortex from neocortex
Rhinal fissure
Area 17
Visual cortex
Area 4
Motor cortex
Smallest function unit
-Neocortical column
What is the conncectome of the neocortex?
Detailed wiring diagram of connections
Primary Sensory Areas
First to recieve signals
Secondary Sensory Areas
Heavy connections w/ primary areas
Motor Areas
Control of voluntary movement
What are more recent evolutions of association areas of cortex?
-The “mind”
-Interpreting behaviour in terms of unobservable mental states
Which is NOT common to most mammals?
Association
