Lecture 3 Flashcards
Describe the major divisions of the nervous system*
The Nervous system (vertebrate)
Central (CNS): Brain & Spinal cord
Peripheral (PNS) everything else
Somatic (SNS) body, the somatic muscles and the skeleton; external environment, (mostly) conscious; mostly available to your self
**Afferent (sensory) **out from the body to the brain
**Efferent (motor) **out from the brain/ spinal cord to the muscles
Autonomic (ANS) internal environment, (mostly) non-conscious, acidity, ionic balance, sensory signals to your brain but you are not aware of it or knowledge of it (like how fast your gut is digesting rn); you can indirectly influence it but not directly control it like somatic information
Afferent (sensory) sensory information coming in
Efferent (motor) motor information going out
Sympathetic NS mobilize energy, fight-or-flight, do you have enough energy? Not evenly, think about how your hands get cold, there are some conserved
Parasympathetic NS conserve energy, rest-and-digest, prepares for future stressful events, turning energy into glycogens and fats to be stored
Not always mutually exclusive/ in opposition to one another
the neuroanatomical directional terms*
General terminology
**Nucleus (plural: Nuclei): **A cluster of cells found in the CNS (central nervous system), such as the brain.
**Ganglion (plural: Ganglia): **A cluster of cells located in the PNS (peripheral nervous system)
What happens when the cell cluster moves, which one is it? It is both.
The motor neuron cell body is the CNS, and the axon is the PNS
Tract (CNS) vs. nerve (PNS) vs. fibres (all)
Directionality
Neuraxis: from the brain down the spinal cord
Determines what anterior (front) and posterior (back or tail)
Top and bottom; the dorsal and ventral
Breaking you into two EQUAL halves, the line is the medial (mid-line)
Lateral in relation to the midline
in humans, 90 degree turn, everything from the spinal, hindbrain and midbrain are at the back of your head hence posterior
Nose is anterior; need to pass the midbrain to reach the forebrain
Sections and cuts
Coronal (frontal) section; face from the rest of the brain
Horizontal sectional; across your forehead horizontally
Mid-sagittal (medial) section; vertically, may not be the middle
Identify the cross section of the spinal cord
From anterior to posterior: Cervical, Thoracic, Lumbar, Sacral, and Coccygeal (not all of us have this last one)
Spinal cord
What is intermitten projection
Intermittent projections: covered in bone and the spinal cord comes out in intermittent projections
Nerves come out from the midbrain along the spine
Where would damage cause a greater loss of function in the spinal cord, and why?
loss of function related to a segment of damage!
Damage in the cervical cord is the worst because it blocks all post-posterior input, causing loss of all those afferents, losing all motor outputs
Narrows/tapers when from cervical to coccygeal – why?
Thick to thin, it narrows
Sensory information coming to the spinal cord has to travel up all the way from the bottom
More sensory information the closer it gets to the brain (like a highway with multiple lanes)
Ends in** cauda equina **
The horse’s tail, the fraying of the nerves at the end of the spinal cord
This also where all the sensory information comes in, as it’s the bottom
Motor information is thinning—making the bottom of the spine the smallest part
Discuss the Grey/white matter divisions and Dorsal/ventral organization of the spinal cord
**Grey/white matter divisions **
reversal of the grey and white matter—in a spinal cord it’s the opposite, the grey matter is in the middle (H), and the white matter surrounds all around it
Dorsal/ventral organization
Division of afference coming in—it comes in on the dorsal side
All motor info going out is coming in from the ventral side
When you have damage to your spinal cord
the dorsal side = sensation loss
the ventral side= loss in motor control
List the divisions of the brain in 3 and 5
Major Divisions of the Brain (3)
forebrain, midbrain and hindbrain
Major Divisions of the Brain (5)
Myelencephalon, Metencephalon, Mesencephalon, Diencephalon, Telencephalon
Describe the structures and functions of the Myelencephalon
hindbrain/ medulla
Intersection between brain and spinal cord; afference and efference pass here
Lots of tracts going in and out
A series of nuclei are found here that keeps your heart breathing, basic reflexing for digesting food (makes you swallow or move your diaphragm), etc
Involuntary control of life-sustaining functions
Doctors reluctant to perform surgery here
Even a small amount of damage is often fatal
It’s a incredibly delicate and important part
The beginning of the reticular formation
(Runs from myelencephalon to mesencephalon)
Critical for arousal, wakefulness, attention, sleep
Parts of your brain that generate consciousness
Damage to this region causes major disruptions to life, and/or can be fatal
Describe the structures and functions of the Metencephalon
hindbrain/ pons (ventral)/ cerebellum (dorsal)
Lots of tracts for afference and efference
Comprised of multiple regions
Also houses reticular formation
pons: large white-matter bulge, continuing from spinal cord/medulla, has many myelinated axons traveling in and out
Damage to this region: fibres come in and out, which means it could cause muscle weakness, numbness in body, and problems with sleeping and waking states
**cerebellum: **
10% of brain volume,
>50% of neurons
Critical for motor coordination, more, not motor control
Damage: you have to make conscious corrects with other parts of the brain
The masked corrects is no longer there
Not loss of motor control but coordination
Controls motor coordination (not motor control)
Describe the structures and functions of the Mesencephalon
midbrain
Dorsal side: Comprised of a roof (tectum)
Made of two bumps (or hills), referred as colliculi
- The **superior colliculi **are visual coordination center, it guides your eye movement (curious in bright, flashy, intense visuals)
- The **inferior colliculi **is for auditory control, attracted to loud noises
EX. Sensory overload at boston pizza
Your colliculi keeps wanting to look or hear the flashy noises and visuals
Damage to here might affect troubles with eye movements (like with Parinaud’s syndrome)
Like with having conscious control over movements
Ventral side: and a floor (tegmentum)
Contains part of reticular formation
Periaqueductal grey (PAG) main input is the amygdala which sends signals to the Peri, makes you freeze, flitch, scream
Associated with emotion (like fear)
Dopamine-producing regions
Substantia nigra: dark substance
Ventral tegmental area (VTA): another dopamine producing region, Ddopamine is important for movement
We learn it’s about rewards, but it’s more like movement and motivation
Associated with species-specific behaviors
Like how a human or chimp hoots, how mouse squeaks
Red nucleus
Species-specific behaviours; instincts, motor sensors, but doesn’t play as much of a role in humans
Pattern of function for these: movement-based
Damage to these: Effects movement, Parkinson disease
Describe the structures and functions of the Diencephalon
forebrain
Thalamus:
Many nuclei: inputs from sensory systems, cerebellum, basal ganglia
relay center for sensation, movement , and motor coordination
And so many other inputs Corticothalamic loops?
Play a key role in consciousness
We see people who have damage in the thalamus look awake, eyes open, but unaware, disorders of consciousness
People who have damage to the thalamus have disorders with consciousness or inability to demonstrate conscious thoughts
They look awake, but they are often not aware
Stimulation to the brain can help (a wire is put to the thalamus, and a current is ran through the thalamus)
In some individuals, this will help with arousing some levels of consciousness
Would affect aspects of consciousness and awareness
Hypothalamus: (below)
Many nuclei, collection of nuclei—including as a intersection between the nervous system and the endocrine system (the brain and your hormones)
Diverse functions: sex, aggression, feeding, sleep, wake, more
Regulatory role by the hypothalamus
Example: narcolepsy, can’t stay awake, due to specific neurons in your hypothalamus
Damage to this region?
Hard to pin down but focus collectively on those characteristics
Describe the structures and functions of the Telencephalon
forebrain
The largest in volume, not the most neurons
Not just the cortex, but also the underlying structures
Amygdala, hippocampus
The neocortex or cortex
Does have 6 layers
The hippocampus is a cortex—a layered structure—but we call it an older type of cortex
Neocortex is called its name because it’s a new cortex
Damage here is wide-ranging in its symptoms and is much of what we’ll be discussing in this course
Discuss major fissures and the corpus callosum
The cerebrum is divided into two hemispheres Separating the hemispheres—left and right—by the longitudinal fissure.
The hemispheres are primarily connected by the corpus callosum, the largest and most significant commissure. It allows the two sides of the brain to share information.
Other Commissures: A few smaller tracts also connect the hemispheres, but they are much less prominent than the corpus callosum.
ex: i.e. Split-brain patients
Callosotomy, a rare treatment for epilepsy A person with two minds?
Cut the corpus callosum in an effort to reduce seizures
Some axons that cross are cut
Patients don’t feel any different but unusual behaviour started to occur
Manual disagreement: one hand does one movement while the other does the opposite
Contralateral organization
The left hemisphere controls the right side of the world, and the right hemisphere controls the left side of the world
For most of us, language is lateralized to the left hemisphere
Which means the right hemisphere might have limited capacity to help with speech and
understanding
If you ask ’how are you’ only the left hemisphere can answer’
But the right hemisphere can respond by drawing or writing
The two hemispheres can act somewhat independently
The four lobes of the brain
The frontal lobe, the parietal lobe, occipital lobe, temporal lobe
They all are categorized as specialized functions but these areas are named after the bones (the frontal bones, parietal bones, etc)
These lobes are not functionally meaningful
**Central fissure: **the main sulcus that divides the frontal and parietal lobe
**Lateral fissure: **the main sulcus that divides the frontal lobe to our temporal lobe
The insular cortex or the insula: an older cortex under the cerebral cortex
What are the major components of the limbic system and basal ganglia.
The limbic “system”: not a system
The Papez “Circuit”, aka the Limbic (on the boarder of) “System”
Many regions were affected by rabies in the limbic (meaning on the border of, referring to the cortex and brainstem) area, but it’s not an actual system, they’re not interconnected at all (mostly)
People often put different parts in the limbic system
Amygdala (almond) Related to emotions
hippocampus (seahorse) Related to memory
cingulate cortex (self and decision-making ) Looks like neocortex, but it’s different (it has a different amount of layers)
Many roles, related to autobiographical memory, decision making, pain sensations, and an agonizing decisions (the same between cost and benefit)
Basal ganglia **
Includes striatum (stipped structure) (caudate + putamen) and globus pallidus** (pale globe), sometimes others (e.g. subthalamic nucleus)
Think of caudate + putamen together as the striatum
Nucleus accumbens is a subregion of striatum/caudate, sometimes called ventral striatum
Motivated behaviours
Critical in movement, skills, habits, decision making
Muscle memory, you being good at doing things
Basal ganglia are about learning skills
These two parts are often working on similar processes
This system is a critical part of you doing things—your muscle memory
The cerebellum is important or coordination and movement, but for habits and skills will be basal ganglia
Basal ganglia is about skilled habits, like remembering how to ride a bike, remembering where your coffee is at home, or reaching for the TV remote (motivation)
Has aspects of motor coordination and addiction (our motivations behind actions)
what are the lobes of the cerebral cortex*
**The cerebral cortex: **aka The cortex, neocortex (neo=new) (cortex= sheeted, layer structure) (cortex refers to the structure, other areas of the brain have layers too)
6 layers
The largest and most prominent feature of the human brain
The cortex is highly convoluted — why?
We need to fit the brain in our head
cf. The lissencephalic (smooth) cortices of other mammals, birds, etc.
Convolutions
Gyrus/gyri (outward folding) and sulcus/sulci (inward folding)
Sulci are sometimes called fissures when they are deep and prominent
Not functionally meaningful, per se
The gyrus is visible and prominent, hence scientists refer to it more than the sulcus, functionally the same
Know the anatomical features that protect the brain*
We have two arteries on the spine side (back) and two arteries on the belly side (front)
Right internal carotid and left carotid
Right and left vertebral arteries
We have all these arteries moving to the brain which have patches that don’t overlap with other arteries
Every brain region will get blood supply from one artery
Strokes: our brain needs constant supply of blood, and when it doesn’t it becomes very damaged
We have no extra supply of energy and blood
The blood-brain barrier
Has two major features: to separate the brain from the rest of the body, and
Tight junctions
A passage is in our capillary
In our brain, capillaries are pushed tightly together and have no junctions—tight junctions
Astrocyte feet
All nutrition is mediated by astrocytes
For amino acids, astrocytes have specialized processes called active transport
The skull and meninges
Meninges create a pocket that fills with fluid
Referred as being dura mater (means tough mother)
The middle layer is the arachnoid membrane —very hard to spot and see
Has a spider web quality to it
Between layers, there’s a fluid called cerebral spinal fluid (CSF)
Generated in the lateral ventricles, and there’s a flow of CSF from the lateral ventricles and goes down into the third ventral and tom the 4th ventral then goes either to the brain or spine
Plays a role in nutrition
Helps remove wastes from the brain
It is important for protecting the brain
In some cases, these passageways get blocked but ventricles still produce CSF
Fluid builds up in brains, pushing against neurons
Ventricles get larger
Called hydrocephalus
Cognitive deficits and pain
An artificial tube is implanted to help drain the liquid
The last layer is transparent and thin, called the pia mater (little mother)
Clings tightly to the brain
