Lecture 4 - Neuroanatomy & the Development of the Brain Flashcards
Anterior
meaning “FRONT,” sometimes referred to as frontal or rostral
Medial
meaning “MIDDLE”
Dorsal
meaning “ABOVE,” sometimes referred to as superior
Posterior
meaning “TAIL,” sometimes referred to as caudal
Lateral
meaning “SIDE”
Ventral
meaning “BELOW,” or “BELLY,” sometimes referred to as inferior
Horizontal plane
cut it horizontal
- It is created by slicing the brain perpendicular to the long axis of the body, and thus parallel to the floor in a person that is upright.
Sagittal plane
slice down the middle
- The sagittal plane divides the right and left side of the brain into parts.
Coronal plane
a coronal plane divides the brain into an anterior and posterior portion. It is created by slicing the brain parallel to the long axis of the body, and thus perpendicular to the floor in a person that is upright.
How do psychologists and radiologists differ in the way they look at the brain/read it?
Psychologists - normal left & right way
Radiologists - reverse left & right
Contralateral
opposite side
ex: if contralateral stroke, if lesion is on right then it affects left hand
Ipsilateral
same side
Unilateral
on one side only
Bilateral
on both sides
- severe stroke
Proximal
close to the body
Distal
further away from the body
Efferent signal
away from the CNS
Afferent signal
towards the CNS
What are the major subdivisions of the nervous system
- Central Nervous System (CNS) - brain and spinal cord
2. Peripheral Nervous System (PNS) - nerves
Parasympathetic branch/division
INHIBITORY: rest & digest
- constricts pupil
- stimulates saliva production
- constricts bronchi
- slows heart
- stimulates stomach, pancreas, & intestines
- stimulates urination
- promotes erection of genitals
Sympathetic branch/division
STIMULATION: fight or flight
ex: see a tiger
- dilates pupil
- inhibits saliva production
- dilates bronchi
- accelerates heart
- stimulates epinephrine & norepinephrine release
- stimulates glucose release
- inhibits stomach, pancreas, & intestines
- inhibits urination
- promotes ejaculation & vaginal constractions
What are the meninges?
OUTER covering of the brain
- Duramater
- Arachnoid layer
- Piamater
Duramater
Latin for “tough mother”
Arachnoid layer
Greek for “like a spider’s web”
Piamater
Latin for “soft mother”
Meningitis
infection of the meninges increases pressure on the brain.
Encephalitis
infection of the brain itself
Ventricles kinds
- lateral ventricles
- 3rd ventricle
- 4th ventricle
Cerebral aqueduct
connects 3rd & 4th ventricle
Brain is surrounded by ____
cerebrospinal fluid CSF
What are ventricles filled with?
CSF
Ventricles (filled with CSF) are continuous with…
the outer supply of CSF.
What does the CSF function as?
- CSF supports or ‘cushions’ the brain. (water bed for brain)
- Provides nutrients, removes waste, helps maintain the blood-brain barrier.
Contracuop injury
after it hits the front of your skull, it sloshes back & hits the back of your skull
- therefore, damage on front & back part of brain b/c of a violent collision
Where is the CSF produced & circulated?
CSF produced by the choroid plexus and circulated around the subarachnoid space before being reabsorbed by the arachnoid granulations.
or else head will explode or brain will be crushed, because skull doesn’t move
Hydrocephalus
excessive CSF
- can cause pressure in the brain
- ventricles are blown out
- end up having cell death & brain damage
Choroid Plexus Papilloma
type of ventricular tumor
- brain tissue will die away
- surgeries can help prevent it from happening
What does the CNS communicate with?
CNS communicates with the body via nerves that connect with the brain (cranial nerves) or the spinal cord (PNS).
List the 12 cranial nerves
- Olfactory
- Optic
- Oculomotor
- Trochlear
- Trigeminal
- Abducens
- Facial
- Vestibulocochlear
- Glossopharyngeal
- Vagus
- Accessory
- Hypoglossal
Olfactory Nerve
smell
Optic Nerve
vision
Oculomotor Nerve
eye moves
Trigeminal Nerve
chewing, touch, pain for mouth
- has sensory & motor divisions
Abducens Nerve
eye moves
Facial Nerve
motor & sensory nerves
- carries nerve fibers that control facial movement and expression
Vestibulocochlear Nerve
hearing, equilibrium
Glossopharyngeal Nerve
taste, BP
- sensory & motor fibers
Vagus Nerve
heart rate, digestion
Accessory Nerve
swallowing
- impulses from muscles in back & neck
Hypoglossal Nerve
tongue moves
- swallowing, chewing
Medulla Oblongata
- 12 cranial nerves – many attached to medulla.
- RETICULAR ACTIVATING SYSTEM – arousal, attention and sleep-wake cycle.
- motor fibres cross to CONTRAlateral side.
- controls reflexes, respiratory and heart rate.
- damage can be fatal – swelling of other brain regions following injury can also affect the medulla.
(sensitive area)
Reticular activating system
arousal, attention & sleep wake cycle
Cerebellum
- precise or fine motor control (tune-up shop of brain)
- balance
- neuroimaging suggests a role for the cerebellum in many cognitive processes – a ‘mini-brain’?
- IPsilateral motor organization (R cerebellum activates when R side of body moves)
Pons
- main connection between cortex and cerebellum.
- vestibular functions (e.g., balance).
- sleep and arousal.
- contains SUPERIOR OLIVE
Superior olive
point at which information from both ears converges – important for localization of sounds.
(if sound if coming from R, it will 1st hit R ear before L)
Two important midbrain structures:
- superior colliculus (rapid eye movements)
- inferior colliculus (auditory equivalent of SC)
This area is also known as the TECTUM (roof)
- tegmentum - floor
Hypothalamus
- group of nuclei.
- maintain equilibrium or homeostasis. (not too hungry, not to cold etc.)
- ventromedial lesions affect regulation of food intake.
- regulate body temperature (anterior and posterior nuclei).
- regulates hormones (involved in sexual behaviour, biological rhythms, fight or flight responses, etc.).
Thalamus
- group of nuclei.
- sensory and motor relay centre.
- LATERAL GENICULATE NUCLEUS
- MEDIAL GENICULATE NUCLEUS
Lateral geniculate nucleus
relays information from the retina to visual cortex
Medial geniculate nucleus
relays information from auditory pathway to cortex
Basal Ganglia
- group of nuclei – functionally related. (b/c all involved in motor control)
- primarily involved in motor control.
- Caudate nucleus, Globus pallidus, Putamen
Damage to the basal ganglia
Parkinson’s disease, Huntington’s disease, Tourette’s syndrome
Parkinson’s disease
lack of movement
- M. J. Fox
damage to BG
Huntington’s disease
too much movement
- common to be falling over (hunched) & tremors
damage to BG
Tourette’s syndrome
swearing is rare
motor tics
damage to BG
Limbic System
- Originally thought to be solely involved in emotional regulation. (ex: remembering a funeral or wedding)
- This is partly true but only tells half the story.
- learning and memory
- emotional memories
- recognition of emotions in other people (hard to describe emotion they are seeing, ex: smile)
What are the structures of the Limbic System?
Structures are: Amygdala
Hypothalamus
Cingulate cortex
Anterior thalamus
Mammilliary bodies
HippocampusDevelopment of the brain
25 days: neural tube
40 days: forebrain, midbrain, hindbrain, spinal cord
50 days: more dev.
100 days: cerebral hemisphere, cerebellum, pons, medulla
9 months: formed
Neural tube
serves as the origin of the central nervous system.
Major subdivisions of the nervous system
Forebrain
- telencephalon
- diencephalon
Midbrain
- mesencephalon
Hindbrain
- metencephalon
- myelencephalon
Preformation
- Seneca (Roman philosopher) – suggested embryo was just a miniature person.
- Claims made that microscopic horses could be seen in horse semen!
In fact, there’s a striking similarity in embryos across species!
Basic structure of brain
All vertebrates share the same CNS structures:
- Forebrain
- Brainstem (midbrain and hindbrain)
- Neural tube (spinal cord)
In humans these structures are evident at 28 days gestation.
Gross development
18 days: neural plate (primitive neural tissue)
21 days: neural plate –> neural groove
22 days: neural groove (closing to form neural tube) –> neural tube & ventricle
23 days: anterior neural folds (close to form brain) –> neural tube
- “wrinkles” in the brain don’t start forming until about 7 months (post birth)
= more real-estate, able to fit more cortex into skull
Principle structures of the subdivisions
Telencephalon:
- cerebral cortex
- basal ganglia
- limbic system
Diencephalon:
- thalamus
- hypothalamus
Midbrain:
- tectum tegmentum
Hindbrain:
- cerebellum
Origins of Neurons and Glia
- lining of neural tube – neural stem cells.
- extensive capacity for self-renewal. (regenerate itself & you can keep testing that line of stem cells)
- in the adult stem cells line the ventricles – VENTRICULAR ZONE
Ventricular zone
in the adult stem cells line the ventricles
Growth and development
- Cell birth (neurogenesis, gliogenesis)
- Cell migration
- Cell differentiation
- Cell maturation (axon and dendritic growth)
- Synaptogenesis (formation of synapses)
- Cell death – synaptic pruning
Cell migration
- road map provided by radial glial cells. (act like ladders for baby neurons)
- layers of the cortex are added on from the inside out.
Cell migration – path finding
normally particular neurons from the retina migrate to specific sites on the optic tectum.
if the neurons are severed and the eye rotated in its socket 180 degrees, they continue to seek out the preprogrammed sites on the optic tectum!
- leads to messed up frogs
a remapping occurs that is maladaptive. (not normal)
Normal mapping vs abnormal mapping in frogs
Normal mapping:
- normally frogs don’t have to identify what a thing is before they snap their tongue at it
- fly senses movement & snaps tongue out at it
- therefore, good at catching flies
Abnormal mapping:
- frogs that went through surgery & have an upside down eye
- b/c visual system doesn’t know it’s upside down
- sends electrical signal along cells that it should be sending them on for a right side up eye, but an abnormal mapping
- therefore, frog snaps in the opp. direction when fly flies above it b/c eye is physically upside down, but connections are in the same place as if eye was right side up
What does path findings tell us?
that they’re strong
- go to a specific location, even if you manipulate the eye, it still goes to the og intented location
Neural maturation
- dendritic arborization (growing branches) and growth of dendritic spines.
- axons grow faster (mm per day) than do dendrites (micrometers per day) – so axons may play a role in dendritic differentiation as they reach their target BEFORE the dendrites are fully formed.
Cell death and synaptic pruning
After ~6 months
- unnecessary connections are killed off. (not good connections)
- up to 100,000 synapses per second!
- neuron relies on its target for survival.
- NEUROTROPHIN promotes survival - without successful contact the dendrite will not receive enough.
think: sculpter or gardener for pruning
Neurotrophin
promotes survival - without successful contact the dendrite will not receive enough
Synaptic pruning
- cell death (APOPTOSIS) can’t completely account for synaptic pruning.
- instead reinforcing functional circuits may lead to synaptic pruning of non-functional circuits.
(if you have a good synaptic connection it stays)
A \_\_\_\_\_\_\_\_ section is made through a human brain parallel to the ground. A) transverse B) horizontal C) sagittal D) frontal E) parasaggital
B) horizontal
Electrical stimulation of the right motor cortex elicits limb movements on the left side of the
body. ________ would describe this organization of motor cortex and the muscles of the body.
A) Contralateral
B) Contramedial
C) Ipsilateral
D) Bilateral
E) Parasaggital
A) Contralateral
The \_\_\_\_\_\_\_\_ is a tough protective sheath that covers the brain and that lies closest to the skull. A) dura mater B) pia mater C) dorsa mater D) arachnoid membrane E) midsagittal sinus
A) dura mater
The third and fourth ventricles are joined together via the A) choroid plexi. B) subarachnoid spaces. C) massa intermedia. D) arachnoid granulations. E) cerebellar aqueduct.
E) cerebellar aqueduct.
CSF is reabsorbed via the A) arachnoid granulations. B) choroid plexus. C) foramen of Magendie. D) nodes of Ranvier. E) All of the above are correct.
A) arachnoid granulations.
What is #2 and what is it’s function?
optic nerve, vision
