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Chemical Control of the Brain and Behavior. Ryan Mruczek Point to Point LGN to V1 Fast Onset Short Duration Specific Disruption leads to specific sensory/motor deficit, such as a blind spot. Widespread Hormone released into blood stream Expanded in space and time

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chemical control of the brain and behavior

Chemical Control of the Brain and Behavior

Ryan Mruczek

types of communication
Point to Point

LGN to V1

Fast Onset

Short Duration


Disruption leads to specific sensory/motor deficit, such as a blind spot


Hormone released into blood stream

Expanded in space and time


Slow Onset and Prolonged Effects

Disruption has more global consequences

Types of Communication
widespread systems
Widespread Systems
  • Neuroendocrine System
    • Maintain homeostasis through controlled hormone release
  • Autonomic Nervous System
    • Coordinates the response of all body organs in response to environment
  • Diffuse Modulatory Systems
    • Small groups of neurons that send axons to many thousands of postsynaptic cells throughout the brain
widespread systems5
Widespread Systems
  • Neuroendocrine System
  • Autonomic Nervous System
  • Diffuse Modulatory Systems
neuroendocrine system
Neuroendocrine System
  • Hypothalamus controlled hormone release
  • Control organs to maintain homeostasis
    • Monitors bodies internal environment
      • Temperature
      • Salt and acidity of blood
      • Glucose concentrations
      • Blood pressure and heart rate
      • Sleep/Wake cycle (Circadian Rhythm)
    • Keeps within small physiological working range
    • Reproductive behaviors
  • Sits ventral to the thalamus
  • Abuts the third ventricle
hypothalamic zones
Hypothalamic Zones
  • Lateral/Medial
    • Connections with brainstem and telencephalon
    • More on this structure later in the course
  • Periventricular Zone (next to the third ventricle)
    • Superchiasmatic nucleus
    • Control autonomic nervous system
    • Neuroendocrine System (hormone communication)
  • Below the hypothalamus
  • Connected by pituitary stalk
    • Neurosecretory neurons project to pituitary
  • Allows hypothalamus to communicate with the rest of the body
  • Two Divisions of Pituitary
    • Anterior
    • Posterior
posterior pituitary
Posterior Pituitary
  • Magnocellular neurosecretory cells of hypothalamus
  • Directly release hormones into bloodstream
  • Neurons act like glands
  • Neurotransmitter (peptides; neurohormones) act like hormones
    • Oxytosin
    • Vasopressin (ADH)
  • Facilitates birth
    • causes uterus to contract
  • Stimulates release of milk from mammary glands
    • In response to sensory stimulus (visual, auditory, somatic)
    • Suppressed during anxiety
  • Also found in men and non-pregnant women so must have other functions as well
vasopressin adh
Vasopressin (ADH)
  • a.k.a. Anti-Diuretic Hormone (ADH)
  • Regulates blood volume
    • Low blood vol, high [salt], low blood pressure
    • Detected by circulatory system and hypothalamus
    • Hypothalamus releases vasopressin
    • Kidney senses vasopressin and increases water retention and lowers urine production
  • Kidney also communicates with brain
2 way communication
2-Way Communication
  • Low blood vol. and high [salt] lead kidney to release renin
  • Renin converts Angiotensin to Angiotensin I
  • Angiotensin I breaks down to Angiotensin II
  • Angiotensin II
    • Kidney and blood vessels increase blood pressure
    • Detected by subfornical organ in brain (no blood brain barrier) and leads to vasopressin release and increase thirst (behavior).
anterior pituitary
Anterior Pituitary
  • Acts as a gland, not part of brain.
    • Synthesize and secrete many hormones
  • But hypothalamus is “master gland”
    • parvocellular neurosecretory cells tell anterior pituitary what to do
    • Release hypophysiotropic hormones which cause increase/decrease secretion of pituitary hormones into bloodstream
hypophysiotropic hormones
Hypophysiotropic Hormones

Luteinizing hormone (LH)

Follicle-stimulating hormone (FSH)

  • Hypothalamus controls hormone release from anterior pituitary

Self regulating:

Inhibit more CRH release

  • Stress response
  • Hypothalamus releases CRH (corticotropin releasing hormone)
  • Anterior pituitary releases adrenocorticotropic hormone (ACTH)
    • a.k.a corticotropin
  • Adrenal glands sit on kidney
    • Adrenal medulla inside
    • Adrenal cortex outside
      • Produces cortisol in response to ACTH
  • Cortisol mobilizes energy storages and inhibits immune system


neuroendocrine summary
Neuroendocrine Summary
  • Hypothalamus (periventricular zone), pituitary and the released hormones form the neuroendocrine system
  • Neurosecretory neurons controls the release of hormones from the pituitary gland
    • Posterior pituitary: direct release of neurohormones
    • Anterior pituitary: releasing factors control hormonal release
  • Periventricular zone also controls the autonomic nervous system
autonomic nervous system ans
Autonomic Nervous System (ANS)
  • Widely distributed network of neurons controlling highly coordinated, automatic functions
    • Thermoregulation
    • Fluid Balance
      • Salt and acidity balance
    • Food Intake and Energy Regulation
      • Glucose storage and mobilization
    • Cardiovascular Reflexes
      • Blood pressure, vasculature, heart rate, blood volume
    • Circadian Rhythm
    • Stress response (fight/flight)
    • Sexual responses
divisions of the ans
Divisions of the ANS
  • Sympathetic
    • Fight or flight response
    • Mobilize energy source and prepare body to handle stress
  • Parasympathetic
    • Active during rest, digestion, energy storage, immune response
  • Antagonistic functions
    • Divisions in competition with each other, but more of a balance between the two systems at any one time.
ans divisions
ANS Divisions
  • Note distinctions
    • Source
    • Preganglionic nt
    • Postganglionic nt
    • Postgangionic cell bodies
    • Unique targets
ans as widespread system
ANS as Widespread System
  • Looks point to point, but activity is expanded in space and time
    • Typically, many pathways active at one time, especially for sympathetic response
    • Long lasting effects, even after initial stimulus is removed (partially due to nt receptors)
    • Large number of targets controlled by small number of cells
    • Responds to circulating hormones
      • Epinephrine (adrenaline) released from adrenal medulla and activates sympathetic nervous system throughout body
ionotropic vs metabotropic receptors
Ionotropic vs. Metabotropic Receptors

Metabotropic Receptor

longer lasting

amplified effects

usually modulatory

Ionotropic Receptor

fast on/off

direct ion flow

signal propagation

drug interactions of the ans
Drug Interactions of the ANS
  • Drugs typically interact with specific neurotransmitter receptors and either mimic (agonist) their effects, or inhibit (antagonist) normal effects.
  • Sympathomimetic – bias towards sympathetic division
  • Parasympathomimetic – bias towards parasympathetic division
  • Atropine: block muscarinic ACh
    • General block of parasympathetic system (sympathomimetic)
    • Counter act poison gas: organophosphates block acetylcholinesterase
      • Symptoms look like overactive parasympathetic system
  • Selectivity of drugs
    • Place drug where you want it
      • Dilate pupils with atropine drops
    • Different receptor subtypes in different organs
      • Lower heart rate by blocking NE with propranolol
      • But also blocks NE receptors in lungs; especially bad for asthmatics
        • Block heart NE receptor (B1) only: atenolol
        • Stimulate lung NE receptor (B2) only: albuterol
enteric system
Enteric System
  • Division of ANS
  • Controls digestion
  • As many neurons as spinal cord
  • Operates relatively independently from CNS
    • Supplemental control by ANS
diffuse modulatory systems dms
Diffuse Modulatory Systems (DMS)
  • Control behaviors that require the coordination of many brain areas
    • Sleep/wake cycles
    • Attention and arousal
    • Learning and memory
    • Motivation and reward (and addiction)
  • Typically modulate normal activity
    • Increase/decrease neural excitability
    • Adjust synchrony and rhythms
dms general anatomy
DMS General Anatomy
  • Source
    • Small core of neurons, typically in brainstem
  • Projections
    • Send each axon to more than 100,000 postsynaptic neurons
    • Widely divergent
      • One axon can have branches in cortex and cerebellum
  • Targets
    • Many parts of cortex, spinal cord, cerebellum, thalamus…
  • Synapses
    • Non-specific
      • Release nt into extracellular fluid, which can diffuse to many surrounding neurons
noradrenergic locus coeruleus
Noradrenergic Locus Coeruleus
  • Many functions because of very widespread connections
    • Attention and arousal
    • Sleep/wake cycles
    • (Learning and memory, pain, metabolism, mood)
  • Most active in the presence of new or unexpected, non-painful stimuli
    • NE may make neurons more responsive and easier to activate
  • Least active during rest
seretonergic raphe nuclei
Seretonergic Raphe Nuclei
  • Caudal nuclei (medulla) innervate spinal cord and are involved in pain modulation
  • Rostral nuclei (pons and midbrain) similar to locus coeruleus
    • Widespread cortical and subcortical projections
    • Most active when animal is awake and aroused
    • Least active during sleep
    • NE and 5-HT DMS form the ascending reticular activating system
dompaminergic dms
Dompaminergic DMS
  • 1. Substantia nigra

to striatum

    • Facilitate initiation of voluntary movements
    • Damage leads to Parkinson’s Disease
  • 2. Ventral tegmental area to frontal cortex and limbic system
    • “Reward” system that reinforces adaptive behaviors
    • Also involved in addiction and some psychiatric disorders
cholenergic dms
Cholenergic DMS
  • 1. Basal forebrain complex
    • Medial septal nucleus to hippocampus
    • First cells to die in Alzheimer’s disease thus linked to cognitive funcitons, learning and memory
  • 2. Pontomesen-cephalotegmental complex
    • Pons and midbrain nuclei to thalamus
    • Regulates excitability of thalamic relay neurons
      • Perfect position to control arousal and attention!