NEUROBIOLOGICAL BASES OF BEHAVIOR

MODULE 1RNSG 2213

PART IAnatomy and

Physiology Review

A & P ReviewThree Main Parts of the BrainThree Main Parts of the Brain1. Forebrain:1. Forebrain:

a. Cerebruma. Cerebrumb. Diencephalonb. Diencephalon

22. . MidbrainMidbrain3.3. Hindbrain or Brain StemHindbrain or Brain Stem

Cerebral cortex = Gray matter

CerebrumConsists of right and left hemispheres connected by the corpus callosum = deep band of nerve cell fibers

The Forebrain

1. Each cerebral hemisphere is divided into four 1. Each cerebral hemisphere is divided into four lobes:lobes:• Frontal lobesFrontal lobes• Parietal lobesParietal lobes• Temporal lobesTemporal lobes• Occipital lobesOccipital lobes

Lobes of the Cerebrum

The Lobes of the Cerebrum: The Lobes of the Cerebrum:

a Closer Looka Closer Look• Frontal LobesFrontal Lobes

– ““The Executive” or decision maker; regulation of The Executive” or decision maker; regulation of behavior, e.g. planning, adaptation to change, etc.behavior, e.g. planning, adaptation to change, etc.• Reliant on other parts of the brain for data. Reliant on other parts of the brain for data. • Prefrontal area relates to features of the personality, Prefrontal area relates to features of the personality,

motivation & goal settingmotivation & goal setting• Motor and Premotor areas: voluntary movementMotor and Premotor areas: voluntary movement

• Parietal LobesParietal Lobes– Perception, interpretation, touch, body perceptionPerception, interpretation, touch, body perception

Lobes of the Cerebrum, cont’d

• Temporal Lobes Temporal Lobes – HearingHearing

• Occipital LobesOccipital Lobes– VisionVision

Limbic System

• ““The Emotional Brain:”The Emotional Brain:” – Consists of many structuresConsists of many structures– Controls the “4 F’s”: Feeding, Fighting, Controls the “4 F’s”: Feeding, Fighting,

Fleeing and FornicatingFleeing and Fornicating– Functions include Memory, Pleasure, Functions include Memory, Pleasure,

Emotions, MotivationEmotions, Motivation

The Forebrain: Cerebrum, cont’d

Functions of The Limbic System

Other Functions of Limbic System

• Olfactory Functions• Feeding Functions (We won’t study these, but consider the

relationships between emotions, pleasure, smell, and food intake!)

Some Important Structures Connecting to the Limbic

System

• Hypothalamus-activates & controls many body functions: endocrine, sleep, appetite, body temp.

• Pineal Gland- role in sleep (secretes melatonin) and consciousness; exact function not known

Important Structures Connecting to Limbic System, cont’d

• HippocampusHippocampus-memory processing, and -memory processing, and making of new memoriesmaking of new memories

• AmygdalaAmygdala-stores feelings relating to -stores feelings relating to memories, i.e.: fear, anger, rage, love, memories, i.e.: fear, anger, rage, love, happiness, etc.happiness, etc.

Structures Connecting to Limbic System cont’d

• VTA (Ventral Tegmental Area)VTA (Ventral Tegmental Area)– ““Pleasure pathway” or “Reward Center”Pleasure pathway” or “Reward Center”– Contains many dopaminergic neurons that Contains many dopaminergic neurons that connect to sites in limbic systemconnect to sites in limbic system– seat of craving in addictionseat of craving in addiction

• Basal Ganglia or Extrapyramidal System Basal Ganglia or Extrapyramidal System Regulate motor behavior, appropriate Regulate motor behavior, appropriate muscle tone and posturemuscle tone and posture– Balances excitatory and inhibitory Balances excitatory and inhibitory

neurotransmitters. neurotransmitters.

Important Structures Connecting to theLimbic System, cont’d

The Forebrain, cont’d

DiencephalonDiencephalon– The diencephalon connects the cerebrum with The diencephalon connects the cerebrum with

the lower brain structuresthe lower brain structures

The Midbrain• Midbrain, or Midbrain, or

MesencephalonMesencephalon --Responsible for visual, --Responsible for visual,

auditory, and balance reflexes. auditory, and balance reflexes. Substantia NigraSubstantia Nigra produces produces Dopamine Dopamine in this area in this area

PonsPons: regulates respiration and muscle : regulates respiration and muscle tonetoneMedullaMedulla: reg. heart rate, blood pressure: reg. heart rate, blood pressureCerebellumCerebellum: muscle tone and coordination: muscle tone and coordination

The Hindbrain• Brain Stem

More (Hindbrain) Brainstem Structures

• Reticular Formation- Integrates sensory input– Reticular Activating System-regulates

alertness and ability to pay attention; allows us to fall asleep as well as wake up

A & P: Systems• Autonomic Nervous SystemAutonomic Nervous System

– Sympathetic:Sympathetic: Dominates in stressful Dominates in stressful situations, prepares body for fight or flightsituations, prepares body for fight or flight

– ParasympathicParasympathic: Dominates when person is : Dominates when person is relaxedrelaxed

Neurons: A ReviewNerve TissueNerve Tissue• CNS: neurons, composed of: CNS: neurons, composed of:

– Cell bodyCell body contains nucleus contains nucleus – AxonAxon transmits message to next cell transmits message to next cell– Dendrites receive messages from cell

Neurons: Review, cont’d

Three classes of neurons in CNSThree classes of neurons in CNS• AfferentAfferent (sensory) (sensory)• EfferentEfferent (motor) (motor)• InterneuronsInterneurons

Neurons: Review, cont’d

• Synapse: Synapse: the contact point between two the contact point between two neurons.neurons.

• Synaptic CleftSynaptic Cleft: space between neurons: space between neurons• Pre-synaptic neuronPre-synaptic neuron: area of axon where : area of axon where

neurotransmitters are stored.neurotransmitters are stored.• Postsynaptic neuronPostsynaptic neuron: area of dendrite : area of dendrite

where receptor sites are located.where receptor sites are located.

Neurotransmission (Physiology)

• Neurotransmitters are released into the synaptic Neurotransmitters are released into the synaptic cleft (space) from the axon to the dendrite. cleft (space) from the axon to the dendrite.

(--Calcium ions facilitate NT release)(--Calcium ions facilitate NT release)• NTs bind with receptors on post-synaptic neuron NTs bind with receptors on post-synaptic neuron

(dendrite) and activate it(dendrite) and activate it• Then NT substance is either deactivated or Then NT substance is either deactivated or

returned to the axon (“returned to the axon (“reuptakereuptake”).”).• Nerve cells can release more than one type of Nerve cells can release more than one type of

neurotransmitterneurotransmitter

Pre-synaptic and postsynaptic neuron interchange

Neurotransmission Across the Synapse

Role of Neurotransmitters

in Mental Health• NeurotransmittersNeurotransmitters

– Play an important role in human emotions and Play an important role in human emotions and behavior behavior

– Influence motor activity and hormone levelsInfluence motor activity and hormone levels– Are the target for the mechanism of action for Are the target for the mechanism of action for

psychotropic medicationspsychotropic medications

Categories of Categories of NeurotransmittersNeurotransmitters

CholinergicsCholinergics• Acetylcholine (ACh):Acetylcholine (ACh): involved in involved in

sleep, arousal, movement, sleep, arousal, movement, memorymemory

Categories of Neurotransmitters, cont’d

MONOAMINESMONOAMINES• NorepinephrineNorepinephrine: affects mood, cognition, : affects mood, cognition,

perception, locomotion, CV functioning, sleep perception, locomotion, CV functioning, sleep and arousaland arousal

• DopamineDopamine: effects movement, coordination, : effects movement, coordination, emotions, voluntary judgment, and release of emotions, voluntary judgment, and release of prolactinprolactin

Monoamines, cont’d• SerotoninSerotonin: effects sleep, arousal, libido, : effects sleep, arousal, libido,

appetite, mood, aggression, pain perception, appetite, mood, aggression, pain perception, coordination, and judgmentcoordination, and judgment

• HistamineHistamine (role not well understood): (role not well understood): involved in the immune/inflammatory response involved in the immune/inflammatory response appears to be involved in moodappears to be involved in mood

Categories of Neurotransmitters, cont’d

• Amino AcidsAmino Acids– Gamma Aminobutyric Acid (GABA)Gamma Aminobutyric Acid (GABA)

functions as an inhibitory functions as an inhibitory neurotransmitter (“neurotransmitter (“brain calmerbrain calmer”)”)

• NeuropeptidesNeuropeptides: : endorphins and endorphins and enkephlinsenkephlins, modulate pain and reduce , modulate pain and reduce peristalsis. Also called peristalsis. Also called “natural or “natural or endogenous opiates”endogenous opiates”

NeuroendocrinologyNeuroendocrinology• HypothalamusHypothalamus- the “master gland,” has direct - the “master gland,” has direct

control over the pituitarycontrol over the pituitary• HormonesHormones: all of these affect health. Our main : all of these affect health. Our main

focus in this course = TSH, Melatonin, ACTHfocus in this course = TSH, Melatonin, ACTH

• Circadian Rhythms-Circadian Rhythms- implications in many implications in many mental illnesses: affect sleep cycles and mental illnesses: affect sleep cycles and regulate hormones which influence mood and regulate hormones which influence mood and emotions. emotions.

Other Factors in Other Factors in NeurobiologyNeurobiology

• GeneticsGenetics: research has shown that all : research has shown that all major mental illness seem to have genetic major mental illness seem to have genetic markers. (Increases “risk for”)markers. (Increases “risk for”)

• PsychoimmunologyPsychoimmunology: Normal immune : Normal immune responses are decreased with acute and responses are decreased with acute and chronic stress, grief, bereavement, and chronic stress, grief, bereavement, and depression.depression.

PART 2

Neurobiology and Mental Illness

Neurobiology and Mental Illness

• Neuroanatomical Changes (examples)

-Enlargement of ventricles: schizophrenia, alcoholism-Atrophy of hippocampus: trauma or severe stress in early life

Which one is the schizophrenic brain?

Neurobiology and Mental Illness, cont’d

• Decreased Cerebral Blood Flow (Some examples)

-In Prefrontal cortex: Schizophrenia-In Frontal lobe: Attention-Deficit Hyperactivity Disorder (ADHD)

Which one is the schizophrenic brain?

Cerebral blood flow (CBF) levels in middle cerebral artery of gray matter

Source: Romanian Journal of Psychopharmacology, 2008

Neurobiology and Mental Illness, cont’d

• Neurotransmitter Dysfunction Lack of availability or lack of secretion (Some examples)

– Too much dopamine: Schizophrenia– Insufficient serotonin: Depression– Insufficient norepinephrine: Depression– Insufficient GABA: Anxiety disorders

NB and MI, cont’d

• Neuroendocrine Dysfunction (examples)

-Altered Hypothalamic regulatory mechanisms: Anorexia Nervosa

-Increased Hypothalamic-Pituitary-Adrenal Axis (HPA) activity causing elevated cortisol (stress hormone) levels: Caused by early life deprivation, trauma or stress

-Thyroid dysfunction: (Hyper-)Anxiety, (Hypo-) Depression

Implications for NursingImplications for Nursing• Nature-NurtureNature-Nurture dichotomy does not dichotomy does not

exist. Each affects the other.exist. Each affects the other.• Nurses need to take a holistic Nurses need to take a holistic

approach to mental healthapproach to mental health• Psychiatric/mental health nurses Psychiatric/mental health nurses

can not “just take care of the mind.”can not “just take care of the mind.”• Medical needs of mental health Medical needs of mental health

clients: Physical status, responses clients: Physical status, responses to drug effects, and diagnostic/ lab to drug effects, and diagnostic/ lab work need to be monitored.work need to be monitored.