3. Nerve signals in brain stem activate cerebrum in 2 ways:
• Background neuronal activity
• Neurohormonal system
4.
5. • Without continuous transmission of nerve signals from the lower brain into the
cerebrum, the cerebrum becomes useless
• Control of cerebral activity by continuous excitatory signals from the brain stem by
reticular excitatory area of the brain stem—a driver of brain activity
• located in the reticular substance of the pons and mesencephalon. This area is also
called the bulboreticular facilitory area
• Increased Activity of the Excitatory Area Caused by Feedback Signals Returning From
the Cerebral Cortex
• A Reticular Inhibitory Area Is Located in the Lower Brain Stem
• The Thalamus Is a Distribution Center That Controls Activity in Specific Regions of the
Cortex
6. NEUROHORMONAL CONTROL OF BRAIN ACTIVITY
Neurohormonal Systems in the Human Brain
I. Norepinephrine system
II. Dopamine system
III. Serotonin system
IV. Acetylcholine system
7.
8. LIMBIC SYSTEM
Ring of forebrain structures that surround the brain stem and are interconnected
by intricate neuron pathways
entire neuronal circuitry that controls emotional behavior and motivational drive
9.
10. 2 routes of communication between limbic system and brain stem
• Medial forebrain bundle extending from the septal and
orbitofrontal regions of the cerebral cortex downward through
the middle of the hypothalamus to the brainstem reticular
formation
• Short pathways among reticular formation of brain stem,
thalamus, hypothalamus and most other contiguous areas of
the basal brain
11. Limbic Means: border (border structures around basal ganglia)
COMPONENTS OF LIMBIC SYSTEM
• Subcortical
• Cortical
18. • Less than 1% of the brain mass but, most important of the control pathways of
the limbic system.
• Two-way communicating pathways with all levels of the limbic system
• Output signals in three directions
i. backward and downward to the brain stem
ii. Upward toward diencephalon and cerebrum( anterior thalamus and
limbic portions)
iii. Hypothalamic infundibulum
21. VEGETATIVE FUNCTIONS
• Cardiovascular Regulation/Arterial pressure regulation
• Body Temperature regulation
• Body water regulation/Thirst and water conservation
• Regulation of Uterine Contractility and Milk Ejection from the Breasts
• Gastrointestinal and Feeding Regulation/Appetite and energy expenditure
• Hypothalamic Control of Circadian Rhythms—The Suprachiasmatic Nucleus
22.
23.
24.
25. Cardiovascular Regulation
Hypothalamic stimulation can cause changes in arterial pressure and heart rate
Stimulated area/nucleus Arterial pressure & heart
rate
Posterior and lateral
hypothalamus
Increase
Preoptic area Decrease
26. Body Temperature Regulation
Preoptic area, anterior portion of hypothalamus responsible
Increased temperature blood
Flows through preoptic area
Increases activity of temperature-sensitive neuron
Decrease in temperature will decrease neuronal activity
27. Body Water Regulation
Two ways
1Thirst
• Thirst center-lateral hypothalamus
• Fluid in this & surrounding area becomes concentrated
• Desire to drink/thirst sensation develop
• Intake of water from nearby source to compensate electrolyte
28. 2 Control of water excretion in urine
• Supraoptic nuclei control renal water excretion
• Stimulate when body fluids become too concentrated
• Nerve fibers pass to posterior pituitary
• Here ADH/vasopressin is secreted
• Transported via blood to kidneys
• Collecting tubules & ducts increase water reabsorption for electrolyte
balance
29. Regulation of Uterine Contractility and Milk Ejection from the Breasts
Paraventricular nuclei secrete the hormone oxytocin on stimulation
• Oxytocin released at the end of pregnancy
• Stimulates Uterine/ labor contractions
• Expels the baby
30. • Baby suckles the mother’s breast
• Reflex signal from the nipple to the posterior hypothalamus releases
oxytocin
• Contracts the ductules of the breast
• Expels milk through the nipples
31. Gastrointestinal and Feeding Regulation
Lateral hypothalamic area (hunger area) stimulation
• extreme hunger
• a voracious appetite
• an intense desire to search for food
Damage to it causes loss of desire for food, sometimes causing lethal starvation
Ventromedial nuclei- satiety center
Stimulation ceases food intake & indifference to food
Bilateral destruction will cause overeating/voracious eating leading to
tremendous obesity
32. Arcuate nucleus
Stimulation causes increased or decreased appetite
Mammillary bodies
partially control the patterns of many feeding reflexes, such as licking the lips
and swallowing
33. Hypothalamic Control of Endocrine Hormone Secretion by the Anterior Pituitary
Gland
Blood flows first through lower part of hypothalamus than towards the pituitary
gland
Upon coursing through the hypothalamus, specific releasing and inhibitory
hormones are secreted into the blood by various hypothalamic nuclei
These are transported via the blood to the anterior pituitary gland
Act on the glandular cells to control release of specific anterior pituitary
hormones
34.
35. Control of Circadian Rhythms—The Suprachiasmatic Nucleus(SCN)
SCN located above the optic chiasm where the optic nerves cross underneath
the hypothalamus
SCN neurons serve as “master clock,” with a pacemaker firing frequency that
follows a circadian rhythm
This pacemaker function is critical for organizing sleep into a recurring 24-hour
circadian pattern of sleeping and waking
36.
37. The SCN receives direct innervation from the retina via the retinohypothalamic
tract (RHT) to entrain/alter its activity to day–night cycles
SCN neurons project to various brain centers, which contain local circadian clocks
that direct feeding–fasting, sleep–wakefulness, autonomic and neuroendocrine
circadian rhythms
These systemic cues synchronize local molecular clocks in peripheral tissues
These local clocks then direct circadian gene expression that regulates
physiological rhythms, including those related to mental alertness and cognition,
cardiovascular regulation, metabolism, and renal function
42. Hypothalamic stimulation affects behavior
Lateral
Overt rage, fighting + (thirst and eating)
Ventromedial nucleus
Satiety, decreased eating, and tranquility
Thin periventricular zone
Fear and punishment
Anterior and posterior regions
Sexual drive
43. EEFECTS OF HYPOTHALAMIC LESIONS
Bilateral lesions in the lateral hypothalamus
• Decrease drinking and eating almost to zero, often leading to lethal
starvation.
• Extreme passivity with loss of most of its overt drives
Bilateral lesions of the ventromedial areas
• Excessive drinking and eating
• Hyperactivity
• Frequent bouts of extreme rage on the slightest provocation
45. Limbic system concerned with affective nature of sensory sensations
• Pleasant reward satisfaction
• Unpleasant punishment aversion
Major reward centers
Along medial forebrain bundle
Lateral (weaker stimuli give reward) and Ventromedial nuclei of hypothalamus
Minor/less potent Reward centers
Septum
Amygdala
Certain areas of thalamus and basal ganglia
Few parts of basal tegmentum
46. Major Punishment centers
central gray area surrounding the Aqueduct of sylvius extending to
periventricular zones
Minor/less potent Punishment centers
• Amygdala
• hippocampus
Effects
Displeasure, fear, terror, pain, punishment, sickness
Punishment and fear can take precedence over pleasure and
reward
47.
48. Association of Rage with Punishment
• Emotional pattern associated with punishment is Rage pattern
• Can be elicited by Strong stimulation of the punishment centers of the brain,
especially in the periventricular zone of the hypothalamus and in the lateral
hypothalamus
Inhibition
Ventromedial nuclei of hypothalamus, hippocampi and ant. limbic cortex
Placidity and Tameness
Stimulation of reward centers
Effect opposite to that of punishment center
49. Importance of reward and punishment in Behavior
Rewarding act is continued
Punishing act is ceased
Tranquilizers
chlorpromazine, usually inhibits both the reward and the punishment
centers, thereby decreasing the affective reactivity of the animal
Learning and memory
• Habituation
• Reinforcement
53. AMYGDALA
• Behavioral awareness areas that operate at a semiconscious level
• Project one’s current status into the limbic system in relation to both
surroundings and thoughts
• Believed to make the person’s behavioral response appropriate for each
occasion
54. • Complex of multiple small nuclei
• Bidirectional connections with limbic system and hypothalamus
Afferents
Efferents
• Concerned with olfactory stimuli in lower animals
• In humans , Basolateral nuclei concerned with Behaviour
Due to multiple connections, the amygdala has been called the “window”
through which the limbic system sees the place of the person in the world
55. STIMULATION OF AMYGDALA/FUNCTIONS
Effects from Amygdala via hypothalamus
• Arterial pressure & heart rate (Increase or decrease)
• GIT’s motility and secretion (Increase or decrease)
• Defecation or micturition
• Pupillary dilatation (rarely constriction)
• Piloerection
• Secretion of various anterior pituitary hormones
56. Other effects
• Involuntary movements
(1) tonic movements, such as raising the head or bending the body
(2) circling movements
(3) occasionally clonic, rhythmical movements
(4) different types of movements associated with olfaction and
eating, such as licking, chewing, and swallowing
• Rage, escape, punishment, severe pain, and fear
• Reward and pleasure
• Sexual activities
57. Klüver-Bucy Syndrome
Bilateral Ablation of the Amygdala
Both Anterior temporal lobes destroyed in a monkey (rare in humans) results
in
• Not afraid of anything
• Extreme curiosity about everything
• Forgets rapidly
• Puts everything in mouth and tries to eat
• Abnormal sex drive
60. • Emotional and motivational aspects of behavior
Reward and punishment
• Autonomic functions
Heart rate, Blood pressure, water and temperature regulation
• GI/Feeding habits- hunger & satiety
• Circadian Rhythms
• Endocrine function
• Memory/learning
• Sexual functions
