1. Overview of the Nervous System
Chapter 2
Overview of the
Nervous System

2. Anatomical Directions Help Us Locate Structures in the Nervous System
Need directions to help keep things straight when we talk about them, like we have for directions to locations on a map (north, south, etc.)
A map of the brain, by the way, is called an brain atlas
If you know these terms you can often find a structure just by looking at name (ventral medial hypothalamus – ventral means towards belly, so look near bottom of hypothalamus, medial means towards the middle, so look near midline)
VMH by the way was what I talked about during last class, if it is lesioned animal overeats
What happens if it is stimulated?

3. Anatomical Directions for a Four-Legged Animal
Anatomists have own terms, usually two or more for same thing
Anterior – ear is anterior to shoulder
Posterior – hip is posterior to shoulder
Dorsal – shoulder is dorsal to front paw (think dorsal fin of a shark)
Ventral – mouth is ventral to eyes
Lateral – ears are lateral to mouth
Medial – spine is medial to shoulders
Ipsilateral – left hand is ipsilateral to left foot
Contralateral – left hand is contralateral to right foot

4. Anatomical Directions in a Two-legged Animal
In humans, the dorsal parts of our brain form a 90-degree angle with the dorsal parts of the spinal cord.
Everything is fine until we get to humans, who walk upright, and therefore have 90 degree angle in part of their brain

5. Planes of Section
Book does a good job of color coding things, so if you start getting confused, try to follow colors
Coronal sections
divide the brain from front to back.
Sagittal sections
parallel to the midline and give us a “side” view of the brain.
Horizontal (axial) sections
divide the brain from top to bottom.

6. Basic Features of the Nervous System Meninges:
Dura mater:
Arachnoid membrane:
Brains is protected in many ways
What’s the most obvious one? Skull
2. Meninges: protective layers that cover the nervous system
CNS (brain & spinal cord)
Dura mater: tough and flexible (Dura: hard mother, word “durable” comes from same latin word)
Arachnoid membrane: web-like (Arachnoid: spider)
(subarachnoid space [Blood vessels and Cerebrospinal Fluid (CSF)]
Pia mater: thin and delicate (Pia: pious mother)
PNS (nerves in rest of body)
Dura mater
Pia mater
Pia mater:

7. Basic Features of the Nervous System
Ventricles:
Hollow spaces within the brain.
Each ventricle produces cerebrospinal fluid (CSF).
CSF supports the weight of the brain.
Prevents pressure on neurons, which would lead to false info
Helps reduce shock to the CNS caused by sudden head movements.
Choroid plexus:
The highly vascular tissue that protrudes into the ventricles and produces cerebrospinal fluid.
Ventricles: Hollow spaces within the brain.
Each ventricle produces cerebrospinal fluid (CSF).
Functions of CSF:
CSF supports the weight of the brain.
Prevents pressure on neurons, which would lead to false info
Helps reduce shock to the CNS caused by sudden head movements.
Choroid plexus converts material in blood into CSF

8. Circulation of the Cerebrospinal Fluid
Four ventricles:
2 lateral ventricles
3rd ventricle
4th ventricle
Central canal of the spinal cord
Subarachnoid space
CSF made in ventricles by choroid plexus, exits ventricles below fourth ventricle, flows into subarachnoid space thru small hole
Absorbed back into the blood supply at the top of the head, but never has direct contact with the blood
(blood toxic to the brain)
CSF made constantly – new supply about 3 times a day
Sometimes chemical signals sent through it

9. The Brain’s Blood Supply
Two major vessels get blood to brain, carotid and vertebral
When they get to brain they branch into three main arteries that serve different parts of the brain
Any interruption to blood supply can cause brain damage
Significant brain damage will occur less than 3 mins after heart stops
BUT… blood itself is toxic to the brain

10. Blood-Brain Barrier (barrier #1)
Blood-brain barrier – fluid (CSF) that surrounds brain is separated from blood
Some materials can get thru barrier, some cannot (chemicals, fluid levels for cells)
Why is it there?
The composition of the fluids surrounding cells is very important, if it changes even slightly it will interfere with a neurons ability to send signals to other cells
In rest of body
In brain
Copyright © 2004 Allyn and Bacon

11. Blood-Brain Barrier (barrier #2)
Blood-brain barrier – fluid (CSF) that surrounds brain is separated from blood
Some materials can get thru barrier, some cannot (chemicals, fluid levels for cells)
Why is it there?
The composition of the fluids surrounding cells is very important, if it changes even slightly it will interfere with a neurons ability to send signals to other cells

12. The Organization of the Nervous System
PNS – has all of the nerves that exist the spinal cord and brain, which carry sensory info into CNS and motor info out of the CNS
Two major parts: somatic - voluntary movement of skeletal muscles
Autonomic - Controls the body’s vegetative functions. Sympathetic division: arousal and expenditure of energy.
Parasympathetic division: a relaxed state.
We’ll talk more about this towards end

13. The Spinal Cord Functions: The “information superhighway”
Protective withdrawal reflexes
Patellar reflex
Postural reflexes
Show nerves exiting spinal cord
That most of the info going to and from the brain must pass thru spinal cord
Sensory comes in dorsal side
Motor goes out ventral side
And
Do not need to memorize these names, but you do need to know that different levels of the spinal cord control different parts of the body
Gray matter/white matter in spinal cord
Reflexes
Some behaviors happen without any info needing to go the rest of the brain at all, they are automatic
patellar involves just two neurons, one taking sensory info in, another making leg kick out
Afferent input (access to) – sensory info going into spinal cord, always enters from dorsal side
Efferent input (exit from) – motor info going out of spinal cord, always exits from the ventral side
Afferent root swells into dorsal root ganglion outside of spinal cord (cell bodies of nerve cells)
Then axons from afferent and efferent nerves combine – mixed nerve – to go to part of body they serve

14. Divisions of the Brain
Talk about brain being like a cup, with layers piled on top of each other
Hindbrain: (heart rate, breathing, sleep, balance)
Cerebellum (means little brain): Maybe other functions? Cognitive? Autism (reliable marker – abnormal cerebellum); also seems to be important for learning classical conditioning associations
Midbrain: visual/auditory reflexes, like pupil changing size in different light and turning to look at movement out of corner of eye, or toward a sound
Forebrain has a lot of parts, where what we think of as cognition mostly takes place

15. The Three Main Sections of the Brain: The Hindbrain
Medulla
Cerebellum
Pons
Raphe Nuclei
Locus Coeruleus
Medulla: breathing, heart rate, blood pressure; damage usually fatal
Also, has groups of cell bodies, called nuclei, that control cranial nerves, which are part of the PNS and important for getting a lot of sensory info into brain (from eyes, nose, ear) some motor control (eye muscles, tongue) and sending info back and forth to glands like liver, kidney, pancreas
Pons (means bridge): connects two halves of cerebellum, and medulla to higher brain areas; cranial nerve nuclei; arousal and sleep
raphe nucleus – sleep/arousal
locus coeruleus – attention/arousal
Cerebellum (means little brain): muscle tone, balance, coordination of voluntary movements – helps plan them – info from spinal cord tells it where body currently is, info from cortex tells it what movement you intend to do, cerebellum makes it happen in right order
cerebellum one of first areas to be affected by Alcohol, has adverse effects on – walking straight line
Maybe other functions? Cognitive? Autism (reliable marker – abnormal cerebellum); also seems to be important for learning classical conditioning associations
Reticular formation travels from the top, or dorsal, part of medulla, thru pons (sleep and arousal)

16. The Three Main Sections of the Brain: The Midbrain
Tectum:
Superior Colliculus
Interior Colliculus
Tegmentum:
Periaqueductal Gray
Substantia Nigra
Tectum (roof): top part
Tegmentum: bottom part
This is where the third and fourth ventricles meet, at the cerebral aqueduct
Colliculi- vision (reflexes – having pupil change size with different light, eye movements) and hearing (turning head to noise, timing of sounds to localize them in space)
Peri (around) grey – pain, responds to opiates like morphine
Substantia nigra (black stuff): important part of motor system, this is the area that degenerates with people with Parkinson’s disease (have problems moving)

17. The Three Main Sections of the Brain: The Forebrain - Diencephalon
Thalamus
Hypothalamus
Forebrain has two parts
One the diencephalon – two structures
Everything else belongs to something called the telencephalon (to come later)
Thalamus – two halves, third ventricle here, almost all sensory info comes through here, also has lots of connections from cortex
Hypothalamus (below): eating, drinking, sex, body rhythms, and controls the autonomic nervous system (body glands and organs)

18. The Three Main Sections of the Brain: The Forebrain - Telencephalon
Basal Ganglia
Brown and orange area
Motor control, primary motor control area for many animals (nonmammals)
Degenerates in parkinson’s
May have something to do with ADHD and OCD

19. The Three Main Sections of the Brain: The Forebrain - Telencephalon
Limbic System:
Hippocampus
Amygdala
Cingulate Cortex
(hypothalamus)
Septum
Olfactory Bulb
Limbic: Emotion, Learning and Memory
Hippocampus (seahorse) – learning and memory – damage, can’t form new memories
Amygdala – fear, rage, aggression
Hypo – technically part of the midbrain, but has to do with emotions, so sometimes included here as well
Septal area – pleasure, damage  rage and attack
Olfactory – smell

20. The Three Main Sections of the Brain: The Forebrain - Telencephalon
What plane of section?
How do we know what is white and grey?
(trick question – what is BG?)
Sulcus: A groove in the surface of the cerebral hemisphere.
Gyrus: A convolution of the cortex of the cerebral hemispheres, separated by sulci or fissures.
Why is cortex so wrinkled?
Cerebral hemisphere: One of the two major portions of the forebrain, covered by the cerebral cortex.
Cerebral
Cortex
Copyright © 2004 Allyn and Bacon

21. Connections Between the Hemispheres
The corpus callosum
The anterior commissure
Corpus callosum: A large bundle of axons that interconnects corresponding regions of the association cortex on each side of the brain.
As long as we have this vieiwpoint – show cingulate, amygdala

22. The Cerebral Cortex II Lobes: Frontal Parietal Occipital Temporal
Functions:
Sensory
Motor
Association
Frontal – motor, planning
Parietal- somatosensory
Occipital - vision
Temporal – hearing, memory
Localization of function
motor, sensory
assoc. some areas put info together

23. The Peripheral Nervous System
Autonomic nervous system:
Controls the body’s vegetative functions.
“fight or flight” response
Sympathetic division:
Controls functions that accompany arousal and expenditure of energy.
Parasympathetic division:
Controls functions that occur during a relaxed state.
Somatic nervous system:
Controls the movement of skeletal muscles or transmits somatosensory information to the central nervous system.
Auto – is sort of like cruise control, works automatically without thought most of the time, although we can consciously control parts of system if we pay attention to them
Symp – usually reacts to outside stimuli
Turns off systems we don’t need, like digestion, redirects oxygen/blood to muscles bundles and brain
Para – usually reacts to internal stimuli
It’s job is to store energy for future use, provide rest and repair tissues
Vagus – input to/sensation from heart, liver, digestive tract (part of autonomic nervous system)

24. Autonomic Nervous System Sympathetic
Parasympathetic
Auto system control mostly by hypothalamus
symp system evolved to work for short periods; in current society, we sometimes have this system active for longer periods of time, which leads to problems
Para system can’t do its job (resting, repairing, storing energy)
Uses up lots of energy

25. Somatic Nervous System
The Cranial Nerves
Twelve pairs of cranial nerves exit the brain.
Provide sensory and motor functions to the head and neck.
The Spinal Nerves
31 pairs exit the spinal cord
Provide sensory and motor functions to the torso, arms, and legs

26. Cranial Nerves Blue – sensory info; red – motor control
Ones I want you to know:
Olfactory – smelling
Optic – vision
Oculomotor – eye movements
Trigeminal – touch, pain in face, jaw muscles
Facial – face expression
Vagus – input to/sensation from heart, liver, digestive tract (part of autonomic nervous system)
Copyright © 2004 Allyn and Bacon