Brain Basics 5 & 6

Peripheral Nervous System

Spinal nerves, cranial nerves, autonomic nervous system

Central Nervous system

Brain + spinal cord

Nervous system

central and peripheral

Spinal nerves

31 pairs that branch out from spinal cord

Types of spinal nerves

cervical, thoracic, lumbar, sacral

Cranial nerves

12 pairs, don’t enter spinal cord go straight to brain

Nucleus

cluster of neurons

Autonomic Nervous System

sympathetic + parasympathetic (involuntary nervous system)

Triune Brain Model

Reptilian brain, palleomammilian, neomammilian

Reptilian brain has

medulla, pons, midbrain, cerebellum, thalamus, basal ganglia

Paleomammalian

hypothalamus, limbic system

Neomammalian brain has

cerebral cortex

Reptilian stereotypical instinctive behaviors

sex, aggression, pursuit of food, fixed action patterns

reptilian brain formed by

Basal ganglia wrap around brain stem

Paleomamilian brain characteristics

• Characteristics of early mammals 

• Involved in experience and expression of emotions 

• Social attachment (between mother and offspring)

  • Explains why mammalian mothers are better parents than reptiles 

• This later expanded in mammals

Neomammalian brain characteristics

• Characteristics of higher mammals 

• Thinking and reasoning (cognition)

• Suppression/regulation of instincts & emotions form reptilian and paleomammalian brain

  • Overrides instincts, -> flexible behavior 

• Expanded the most in primates 

• Everything outside limbic system (neocortex)

Limbic System feeds into ___

hypothalamus, which drives the physiological expression of emotion

Brain development:

Vesicles form at end of neural tube: forebrain, midbrain, hindbrain, spinal cord 

Hindbrain

Medulla, pons, cerebellum

Medulla

• respiration, heart rate (functions critical for survival), blood pressure regulation, 

• If damaged, fatal

• Carries info from spinal cord up to the brain 

Pons

• Involved in similar functions as medulla 

• Has bulge on ventral surface -> relay station for info from cerebral cortex to cerebellum 

• Cerebrocerebellar connections

Cerebellum

• Allows for more fluid motions

• Modulator of neurological function 

Cerebellum - vermis

balance & posture

Cerebellum - Lateral

motor coordination and cognition

Midbrain

Tectum, tegmentum

Tectum

Has two bumps: superior and inferior colliculus

Superior colliculus

reptilian form of vision inherited

Inferior colliculus

reptilian form of hearing

Tegmentum 

Contains dopamine neurons - crucial for reward and motivation

2 main dopamine neurons (starts w/nuclei that are clusters of neurons that make dopamine)

1. Substantia nigra -> damage leads to Parkinsons, very important source of dopamine

2. Ventral Segmental area 

Forebrain

Diencephalon, Telencephalon

Telencephalon

limbic system (paleomamillian system)

Diencephalon

Enclosed by cerebral ventricles that are filled with cerebrospinal fluid (cushions brain)

Thalamus

Sensory info travels to thalamus before it goes to the brain (visual, auditory, all sensory info)

Decides whether info should be passed on to cortex -> become conscious of sensory info, thalamus blocks everything out

The thalamus is made up of __

two masses of gray matter (right and left) joined together by the internal contingent

Hypothalamus

1. Much smaller in size and volume compared to thalamus 

2. Homeostasis 

3. Regulates appetite, sexual arousal, emotions, connected to endocrine glands (pituitary gland), can control hormone secretion 

Medial

Middle

Lateral

outward areas of hemisphere

Horizontal Plane

rostral: front claudal: back

Coronal Plane

Dorsal: top, Ventral: bottom

Sagittal Plane

Dorsal: top, Ventral: bottom

sulci

inward fold of cerebral cortex

gyri

outward fold of cerebral cortex

Cerebral cortex

thin strip of grey matter

Central sulcus

border between frontal and parietal lobe

Sylvian Fissure (lateral sulcus)

separates temporal lobe from parietal and frontal

Corpus Callosum

communication between right and left side of the brain, links the two hemispheres

Homunculus

proportion of cortex allocated for different body parts

Axons

white matter = myelinated (fatty) axons 

Neuron cell body + dendrites

gray matter 

Subcortical gray matter areas

clusters of neuronal cell bodies and dendrites

Neuron structure

axon, dendrite, axon terminal, cell body,

Axon wrapped in ___

myelin sheath

myelin sheath

allows for insulation but also for electrical signals to travel down the axon more rapidly

Cortex has ___ that varies across space 

cellular architecture 

___ cortical areas, each with different functions

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Cortex has _ layers

Has 6 different layers

Outermost: 1, deepest: 6 (closest to the white matter)

layer 4 is the _ layer

input, information that enters the cortex enters through layer 4

Visual information enters primary visual cortex through the 4th layer

Layer 4 has

Afferent cortical inputs

Layer 5 is the _ layer

output

Layer 5 has _

Efferent cortical inputs

Neurons form modules called ___

cortical columns 

Cortical columns have about ___

50-100 neurons that are all connected to each other and respond to the same stimuli

cortical matter in ___ matter

gray

gyri part of occipital lobe

Lingual and cingulate (part of limbic system)

White Matter

Has myelinated axons that travel in fiber tracts

Projection fibers

connect cerebral cortex to brain stem and gray matter nuclei

ex. Corona radiata

Commissural fibers

connect gray matter in two cerebral hemispheres

ex. corpus callosum

Association fibers

link cortical regions within the same cerebral hemisphere

ex. Arcuate Fasciculus -> sends info towards prefrontal cortex 

Cortico-Limbic interactions

bridge between cognition and emotion 

Orbitofrontal Cortex

Underbelly of frontal lobe above orbits of eyes

Important for social behavior and social cognition -> where they interact with each other

Phineas Gage

• Orbitofrontal cortex damage

• Caused inappropriate social behavior

  • Couldn't regulate emotions and control impulses 

Orbitofrontal Cortex damage

moral dilemas!

People with OFC are more likely to say its ok to violate rights for utilitarian reasoning

___: reaction to task that isn't right is not present in people with OFC 

somatic marker

Input zone

where neurons collect and integrate info 

Output zone

where neuron transfers info to other cells (axon terminal)

Excitatory/inhibitory inputs

(tell neuron to(not) fire)

Neuron connects to ___ of other neurons (gets input from them)

thousands

Neurons integrate inputs and decides in ____ whether to fire or not fire

axon hillock

If fired: action potential travels down ___ to conduction zone to axon terminal where connection w/other neuron is made

myelinated axon

synaptic cleft

Physical gap from one axon terminal to the other -> chemical communication between neurons

vesicles

store different neurotransmitters at different chemicals.

When action potential reaches axon terminal ->

neurotransmitters get released into synaptic cleft -> neurotransmitters bind to receptors in the postsynaptic dendrite

Excitatory input 

makes postsynaptic cell more likely to fire (glutamate)

Inhibitory input

makes postsynaptic cell less likely to fire (GABA)

There are atleast __ neurotransmitters in the brain

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Neuromodulatory neurotransmitters

Serotonin (mood), dopamine (reward), norepinephrine (stress response)

Dopamine, serotonin, norepinephrine have ___ in brainstem -> send exons through the brain to release signal

nuclei