Psy 137 Behavioral Endocrinology

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Psy 137 Behavioral Endocrinology Lecture 2
Nervous system overview
Website http//mentor.lscf.ucsb.edu/course/summer
/psyc137/
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Objectives

• Describe the cells of the nervous system and the
  basic principles of neuronal function including
  action potentials (electrical properties) and
  neurotransmission (chemical properties).
• Give an overview of different parts of the
  nervous system.
• Describe the organization of sensory and motor
  systems, as well as, their integration.
• Provide a brief description of basal ganglia and
  limbic systems.

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Cells of the Nervous System

• Nervous system (brain, spinal cord, and nerves)
  is made up of 100s of billions of cells (10
  neurons and 90 glia).

I. Neurons cells that are capable of sending
and receiving chemical signals. - specialized to
transmit information from place to place with
electrical signals.
II. Glial cells -Provide structural and
metrabolic support to neurons 1. Myelinating glia
(oligodendrocytes Schwann cells) enhance
electrical signalling 2. Astrocytes regulate
extracellular environment nutrients, waste,
neurotransmitters 3. Microglia involved in
response to injury or disease, remove debris,
form scars
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Gene Expression/Protein Synthesis
-The functional unit of biology is the
PROTEIN. -The code to make proteins are contained
in genes which needs to be expressed. -What
makes one cell different from another is the
types of proteins that they contain. -Within a
cell, proteins must be placed in the right
compartment for proper function.
1. Transcription
2. Translation

• Post-translational processing trafficking

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Compartmentalization
Dendrites input (chemical) Body protein
production Initial Segment integration Axon
conduction Terminal output (chemical)
Each compartment contains specialized proteins
associated with the function of the compartment.
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Electrical Properties of Cells
Recordings from Cells
Glia
Neuron
Action Potentials encode information based on
chemical (e.g. neurotransmission) input
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Forces on Ions (charged molecules)
-concentration gradient -electrostatic -gt
determines direction of movement thru channel
(type of protein)
Snyaptic Input results in opening Channels
causing dynamic post-synaptic potentials.
e.g. Na or Ca channel opens
e.g. K or Cl- channel opens
Note Ca same as Na high outside gt wants to
go in.
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Getting to threshold is based on synaptic input
(ie. Sum of EPSP sum of IPSP)
Rising phase open Na channel which is all or
none -gt Na enters cell
Repolarization open (extra) K channels -gt K
leaves cells
Hyperpolarization lasts as long as extra K are
open channels -gt K leaves cells
AP moves as chain reaction (think dominos)
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Neurotransmission
Action potential (Na depolarization)
Action potential neurotransmission
coupling -Ca carries depolarization of
terminal AND signals vesicle fusion
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Parts of a neuron and their roles in neural
communication
1. Dendrites receive chemical information from
other neurons or sensory information through
receptors
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Levels of Chemical Communication
Neurotransmission-point to point
Also, have the Local neurons process parallel
paths of information.
Diffuse Modulatory-coordination w.in brain
Autonomic-parallel networks coordination
throughout body
Endocrine-global via blood stream coordination
throughout body
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The Nervous System
Nervous System
Central Nervous System
Peripheral Nervous System
Definitions Nerves bands of axons in the
PNS Ganglia groups of cell bodies of neurons in
the PNS Tracts bands of axons in the
CNS Nuclei groups of cell bodies of neurons in
the CNS
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The Major Divisions of the Brain
Cortex
Basal forebrain
Brain Stem
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Brainstem Midbrain, Pons, Medulla, Cerebellum
Cerebral Cortex

• Medulla contains essential functions, e.g.
  regulation of breathing, heart rate, digestion
  (via autonomic NS outputs).
• Pons contains reticular formation with inputs
  to forebrain
• Midbrain contains inputs to forebrain and
  orienting nuclei (reflexive sensory-motor
  interface).
• Cerebellum contains circuits critical to
  coordination of motor outputs.

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Brain stem inputs to forebraindiffuse
modulatory systems
Brain stem inputs (e.g. tegmentum, reticular
formation, medulla) to forebrain are highly
diffuse with several thousand cells within a
nucleus innervated many forebrain areas (i.e.
millions-billions of cells). -figure shows brain
stem serotonin systems other monoamine systems
are similar in organization. -also descending
pathways innervating spinal cord.
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Basal Forebrain

• a group of subcortical (under the cortex) brain
  regions, each with distinct functions.

• contains the forebrain parts of the basal ganglia
  (groups of brain regions involved in movement)
  and the limbic system (groups of brain regions
  involved in emotion and motivation-incl. thalamus
  and hypothalamus)

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The Hypothalamus

• Small structure located at base of the
  diencephalon (forebrain)

• MAJOR ROLE 1
• Controlling homeostasis maintenance of a stable
  internal environment.
• Control of hormones and autonomic nervous system.
• Regulates the balance of
• water/salt?thirst nutrients/glucose?hunger
• sex hormones?sex

ventricles

• MAJOR ROLE 2
• Regulating emotional arousal
• sex hormones?aggression cortisol?stress

hypothalamus

• These roles are interrelated!

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Autonomic NS
Sympathetic and Parasympathetic NS regulate all
other parts of the body. Sympathetic and
Parasympathetic have opposite effects on
targets. -Pre-ganglionic neurotransmitter is Ach
for both sympathetic and parasympathetic
NS. -Post-ganglionic neurotransmitter is Ach for
both parasympathetic NS and NE for sympathetic
NS. -Some targets are glands Sympathetic
activated during stress i.e. need energy
fast. Parasympathetic activated when relaxed
stores energy.
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Dorsal Forebrain Telencephalon

• Cerebral cortex (named after the bark on a tree)
  is the layers of cell bodies that lie on the
  outside most part of the brain send axons to
  other cortical areas and to lower brain regions

• is divided up into many regions that serve
  different function (Penfield experiments) and is
  the youngest part of the brain

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A word about cortex layers in general

• The cortex consists of 6 layers of cells
• Each layer consists of different cell types
• Some layers receive information and process it
• Other layers send information following
  processing i.e. cortex contains multiple-layer
  circuits.
• In most cortex, the cells responding to a certain
  type of information are arranged in columns
  comprises a functional unit

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Organization of the Cortex.

• Sensory and motor cortex are dedicated to a
  single modality (type) of information.
• The majority of the human brain is association
  cortex (not colored) which is multimodal
  (processes more than one type of info).

• The association cortical areas allow for higher
  integration of sensory and motor information
  prior to planning and carrying out action.

Human
Rat
Cat
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Principles of Sensory Systems

• Receptor (Transduction) Mechanism detection
  of environmental info and convert to neuronal
  info (i.e. change in frequency of action
  potentials).
• Relay Centers series of projection neurons
  between specific brain nuclei.
• Cross Midline it just does
• Hierarchical organization convergence of
  parallel pathways into cortical nuceli (areas)
  (e.g. primary sensory cortex, secondary sensory
  cortex, etc).

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Topographical mapping in visual paths
Spatial organization of relay centers carries
information on where in world stimulation was
derived. Information is mapped within the
nuclei. Anatomy information
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Relay Parallel Pathways

• Each sensory system is associated with a specific
  transduction mechanism localized in a sensory
  organ.
• Transduction converts environmental info into
  biological signals (eventually encoded as action
  potential in neurons) that is transmitted along
  specific parallel pathways.
• These parallel neuronal pathways are relayed at
  specific points in the brain and is kept separate
  to maintain stimulus info.

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Pathways Thalamus
Thalamus is a major relay for all sensory systems
(for most prior to info arriving at
cortex). MDN-olfaction VPM-taste VPL-somatosensati
on MGN-auditory LGN-visual
Also, contains many motor nuclei and some
involved in complex processes (memory, emotional,
etc poorly understood).
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Pathways Primary Cortex

• Area of cortex that first receives sensory
  information of a given modality (i.e. vision,
  auditory, somatic, olfactory etc or motor) is
  referred to as primary sensory cortex.
• Primary motor cortex is the area that directly
  controls output to muscles (later)

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Pathways Sensory, Motor, Association Cortex

• Cortical areas that are only associated with
  function of primary (sensory/motor) cortex are
  referred to as secondary sensory/motor cortex.
• Areas that are indirectly associated with primary
  cortices (involve multiple sensory modalities or
  sensory-motor information processing) are
  referred to as association cortex mediate
  higher cognitive functions.

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Cortex and Brain Output Overview
Basics Organization Sensor/Perceptual Decision Co
mmand
Precentral Gyrus primary motor cortex (M1)
stimulate muscle contraction. Supplemental and
Premotor cortices secondary motor cortices (SMA
PMA) involved in coordination of input to
M1. Prefrontal cortex involved in executive
function ie conscious decisions Posterior
Parietal cortex involved in perception of body
surroundings input to PFC subcortical systems
(primarily brainstem, cerebellum)
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Levels of sensorimotor systems

• Spinal cord reflex
• Involves somatosensory input to motor neurons
  can be 1 synapse.
• Brainstem reflex
• Involves visual, auditory input to motor neurons
  e.g. orienting reflexes.
• Cortical control of behavior
• Involves perception of sensory input and frontal
  cortex control of motor cortices.

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Sensorimotor System
Posterior parietal association cortex integrates
all sensory info and projects to prefrontal
cortex.
Prefrontal cortex makes decision and sends
commands to secondary motor cortex (via basal
ganglia subcortical cortex-cortex loop).
Secondary motor cortices (Premotor and
Supplementary motor areas) produce precise
pattern of activation of Primary motor cortex
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Motor Cortex control of Descending Paths

• All descending paths are under control of M1
  (primary motor cortex).
• M1 has direct projection to spinal motor neurons
  (cortiocospinal tract)
• M1 also projects to other indirect descending
  pathways.
• Each paths interact with other brain structures
  to produce meaningful, coordinated behavior.

Basal ganglia provides input from Prefrontal
cortex to Secondary motor cortex via the
ventrolateral thalamus.
Cerebellum/Pons -receives massive input from
sensory ctx. -projects to thalamus (VLc) which
relays info to M1 -Coordinates ongoing motor
ouptut
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Lower Motor Neurons

• Lower motor neurons cell bodies are in the
  ventral horn of spinal cord and send axons via
  the ventral root to innervate muscle fibers.
• Activation of muscle fibers causes contraction -gt
  muscle shortens -gt move body (i.e. behavior).

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Limbic system and the basal ganglia

• Both the limbic system and the basal ganglia are
  located in the telecephalon and diencephalon,
  where they curve around the thalamus

• Both the limbic system and the basal ganglia
  receive monamine (particularly dopamine) inputs
  from structures in both the midbrain

• Both the limbic system and the basal ganglia are
  surrounded by cortex enabling these circuits to
  receive primary, secondary and associative
  sensory information and to send motor information
  to the primary and secondary motor cortices.

Limbic system
Basal ganglia
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The Basal Ganglia

• The basal ganglia is a circuit of inter-connected
  brain regions located in the basal forebrain (all
  diencephalon)

• Key role of the basal ganglia is the initiation,
  coordination and control of motor movements

• Basal ganglia also plays a major role in
  procedural memory (the memory of performing an
  act e.g. riding a bike, writing)

• Basal ganglia is considered the habit circuit
  of the brain and can be, but is not necessarily,
  driven by emotionally or motivationally relevant
  items
• The non-cortical system responsible for voluntary
  movements

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The limbic system

• The limbic system is a group of inter-connected
  brain regions consisting of cortical and
  sub-cortical structures within the diencephalon

• The limbic system subserves many functions but
  plays a particularly critical role in emotion,
  motivation and cognition

• The limbic system includes
• Cingulate and prefrontal cortex (emotional
  experience thinking)
• Hypothalamus (homeostasis drive)
• Thalamus (sensory relay)
• Amygdala (learning and fear)
• Hippocampus (learning and memory)
• Nucleus Accumbens (reward drive)

• Motivation and emotion typically involve
• co-activation of several members of the
• limbic system

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Dopamine Inputs.There are 2 major dopamine
systems in the brain with specific midbrain to
forebrain projects.
Mesocorticolimbic system (from midbrain VTA to
PFC, cingulate, limbic, and n. accumbens)
-attention and turning motivation into
action mediates motivational /goal-directed
behavior.
Mesostriatal system (from midbrain SN to dorsal
striatum, basal ganglia) initiation,
termination, direction and fine control of motor
movements mediates habitual responding.
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Putting it all together
Parietal Cortex Sensory/perceptual inputs