Transcript NEUROBIOLOGICAL BASIS OF BEHAVIOR

NEUROBIOLOGICAL
BASES OF BEHAVIOR
MODULE 1
RNSG 2213
PART I
Anatomy and Physiology
Review
A & P Review
Three Main Parts of the Brain
1. Forebrain:
a. Cerebrum
b. Diencephalon
2. Midbrain
3. Hindbrain or Brain Stem
Cerebral cortex
= Gray matter
The Forebrain
Cerebrum
Consists of right and left hemispheres
connected by the corpus callosum = deep
band of nerve cell fibers
1. Each cerebral hemisphere is divided into four
lobes:
• Frontal lobes
• Parietal lobes
• Temporal lobes
• Occipital lobes
Lobes of the Cerebrum
The Lobes of the Cerebrum:
a Closer Look
• Frontal Lobes
– “The Executive” or decision maker; regulation of
behavior, e.g. planning, adaptation to change, etc.
• Reliant on other parts of the brain for data.
• Prefrontal area relates to features of the personality,
motivation & goal setting
• Motor and Premotor areas: voluntary movement
• Parietal Lobes
– Perception, interpretation, touch, body perception
Lobes of the Cerebrum, cont’d
• Temporal Lobes
– Hearing
• Occipital Lobes
– Vision
The Forebrain: Cerebrum, cont’d
Limbic System
• “The Emotional Brain:”
– Consists of many structures
– Controls the “4 F’s”: Feeding, Fighting,
Fleeing and Fornicating
– Functions include Memory, Pleasure,
Emotions, Motivation
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
• Hippocampus-memory processing, and
making of new memories
• Amygdala-stores feelings relating to
memories, i.e.: fear, anger, rage, love,
happiness, etc.
Structures Connecting to Limbic System cont’d
• VTA (Ventral Tegmental Area)
– “Pleasure pathway” or “Reward Center”
– Contains many dopaminergic neurons that
connect to sites in limbic system
– seat of craving in addiction
Important Structures
Connecting to the
Limbic System, cont’d
• Basal Ganglia or Extrapyramidal System
Regulate motor behavior, appropriate
muscle tone and posture
– Balances excitatory and inhibitory
neurotransmitters.
The Forebrain, cont’d
Diencephalon
– The diencephalon connects the cerebrum with
the lower brain structures
The Midbrain
• Midbrain, or
Mesencephalon
--Responsible for visual,
auditory, and balance reflexes.
Substantia Nigra produces
Dopamine in this area
The Hindbrain
• Brain Stem
Pons: regulates respiration and muscle
tone
Medulla: reg. heart rate, blood pressure
Cerebellum: muscle tone and coordination
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 System
– Sympathetic: Dominates in stressful
situations, prepares body for fight or flight
– Parasympathic: Dominates when person is
relaxed
Neurons: A Review
Nerve Tissue
• CNS: neurons, composed of:
– Cell body contains nucleus
– Axon transmits message to next cell
– Dendrites receive messages from cell
Neurons: Review, cont’d
Three classes of neurons in CNS
• Afferent (sensory)
• Efferent (motor)
• Interneurons
Neurons: Review, cont’d
• Synapse: the contact point between two
neurons.
• Synaptic Cleft: space between neurons
• Pre-synaptic neuron: area of axon where
neurotransmitters are stored.
• Postsynaptic neuron: area of dendrite
where receptor sites are located.
Neurotransmission (Physiology)
• Neurotransmitters are released into the
synaptic cleft (space) from the axon to the
dendrite.
(--Calcium ions facilitate NT release)
• NTs bind with receptors on post-synaptic
neuron (dendrite) and activate it
• Then NT substance is either deactivated or
returned to the axon (“reuptake”).
• Nerve cells can release more than one type of
neurotransmitter
Pre-synaptic and postsynaptic
neuron interchange
Neurotransmission Across the Synapse
Role of Neurotransmitters in
Mental Health
• Neurotransmitters
– Play an important role in human emotions and
behavior
– Influence motor activity and hormone levels
– Are the target for the mechanism of action for
psychotropic medications
Categories of Neurotransmitters
Cholinergics
• Acetylcholine (ACh): involved in
sleep, arousal, movement,
memory
Categories of Neurotransmitters, cont’d
MONOAMINES
• Norepinephrine: affects mood, cognition,
perception, locomotion, CV functioning, sleep
and arousal
• Dopamine: effects movement, coordination,
emotions, voluntary judgment, and release of
prolactin
Monoamines, cont’d
• Serotonin: effects sleep, arousal, libido,
appetite, mood, aggression, pain perception,
coordination, and judgment
• Histamine (role not well understood):
involved in the immune/inflammatory response
appears to be involved in mood
Categories of Neurotransmitters,
cont’d
• Amino Acids
– Gamma Aminobutyric Acid (GABA)
functions as an inhibitory
neurotransmitter (“brain calmer”)
• Neuropeptides: endorphins and
enkephlins, modulate pain and reduce
peristalsis. Also called “natural or
endogenous opiates”
Neuroendocrinology
• Hypothalamus- the “master gland,” has direct
control over the pituitary
• Hormones: all of these affect health. Our main
focus in this course = TSH, Melatonin, ACTH
• Circadian Rhythms- implications in many
mental illnesses: affect sleep cycles and
regulate hormones which influence mood and
emotions.
Other Factors in Neurobiology
• Genetics: research has shown that all
major mental illness seem to have genetic
markers. (Increases “risk for”)
• Psychoimmunology: Normal immune
responses are decreased with acute and
chronic stress, grief, bereavement, and
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 Nursing

• Nature-Nurture dichotomy does
not exist. Each affects the other.
• Nurses need to take a holistic
approach to mental health
• Psychiatric/mental health nurses
can not “just take care of the
mind.”
• Medical needs of mental health
clients: Physical status,
responses to drug effects, and
diagnostic/ lab work need to be
monitored.