reticular formation and limbic system

reticular formation and limbic system

1. SEMEY STATE MEDICAL
UNIVERSITY

2. Figure 9-7c (1 of 2)

3. Figure 9-8
Simple reflexes
can be
integrated by the
spinal cord
without input
from the brain

4. Figure 9-9d
Oldest and
most
primitive
region of
the brain.
Ascending
and
descending
tracts pass
through the
brain stem.

5. Divided into three regions- medulla oblongota, pons,
and midbrain
Each region contains cranial nerves & nuclei that
control autonomic function
Many nuclei are associated with reticular formation-
white fibers what interconnect different areas throughout
the brain.
Medulla Oblongata- controls involuntary funtions and
connects to spinal cord.
Somatosensory (ascending) and corticospinal (descending)
tracts in white matter
Pyramids- area where the fibers cross over thus the many
functions are controlled by the opposite side of the brain.

6. 2. Reticular formation-
These are clusters of
neurons (white
matter) that run
through the core of
the brainstem.
Involved in
maintaining the brain
alert, arousal, and
sleep. It also control
visceral functions like
heart rate & vomiting.
A motor tract goes
down the spinal cord
and is involved in
movement.
Reticular Formation

7. Various nuclei: 1) Nuclei of medullary reticular
formation
2) Nuclei of pontine reticular formation
3) Nuclei of midbrain reticular formation
Situated: - Downwards into spinal cord
- Upwards up to thalamus and subthalamus
Diffused mass of neurons and
nerve fibers forming an ill-defined
meshwork of reticulum in the
central portion of the brainstem.

8. Fig. 1 -Afferent connections
of reticular formation
Fig. 2 – Efferent
connections of reticular
formation

9. Receives fibers from the
sensory pathways via long
ascending spinal tracts.
Alertness, maintenance of
attention and
wakefulness.
Emotional reactions,
important in learning
processes.
Tumor or lession –
sleeping sickness or
coma.
Functional divisions of Reticular
Formation
Fig.3 – Brain
section.

10. Inhibitory:
-Smoothness and
accuracy of voluntary
movements
-Reflex movements
-Regulates muscle
tone
-Maintenance of
posture
-Control vegetative
functions
Facilitatory:
-Mantains the muscle
tone
-Facilitates autonomic
functions
-Activates ARAS

11. Emotion, memory,
learning, and
visceral responses
Links higher
cognitive functions
and primitive
emotional responses
Incorporates sensory
areas, basal ganglia,
and the
diencephalon
(hypothalamus)
relates state of mind
to physiological
functions
Figure 9-13

13. The brain may generate
information and output
signals in the absence of
external input
Motor output is influenced
by sensory information,
cognition, and behavior.
Thus cognitive input may
influence the motor output
sent without sensory
input.

14. Figure 9-15
Specialized sensations have separate designated
areas on the cortex

15. Cingulate cortex:
•Coordination of sensory signals
•Emotion
Hippocampus:
•Long-term memory development
Hypothalamus:
•Endocrine regulation
•Body temperature
•Regulation of thirst and hunger
•Regulation of circadian rhythms
Amygdala:
•Aggression and fear
Septal area:
•Sexual arousal

16. Three specializations – Sensory, Motor, and Association
(cognition and behavior).
Sensory areas - stimulus activates sensory receptors, info travels in
ascending pathways and stops at the cerebellum or sensory areas of
cerebrum
Sensory input translated into perception – brain’s interpretation
of various input regions
Motor areas – info travels in descending pathways, cross-over at
brainstem or spinal cord, and reaches muscles or glands
Direct skeletal muscle movement – initiated by cognitive system
based on input from cerebral motoer ares, cerebellum, & basal
ganglia
Association areas -
Integrate information from sensory and motor areas -
Can direct voluntary behaviors – control over conscious
actions

18. Primary somatic sensory cortex- found on the
post-central gyrus (parietal lobe)
Skin, musculoskeletal system, and viscera-
components that send information to this region
when a stimulus activates a sensory receptor
Somatosensory pathways – carry information of
senses in conscious awareness of general somatic
sense, damaged in brain area causes reduced sensitivity
in opposite side
Touch
Temperature
Pain
Itch
Body position

19. Special senses have devoted regions -
Visual cortex –Occipital lobe (Visual
Assosiaction area and Visual cortex)
Auditory cortex – Temporal lobe
(Auditory association area and
Audiotory Cortex
Olfactory cortex- Temporal lobe
(uncus)
Gustatory cortex – Frontal lobe
Processed into perception – allows the
stimulus to be translated into a
different aspect (photons=colors) and
“fills-in” missing information.
Perception is the brains interpretation
of sensory input and it is not directly
dictated by the input

20. Three major types
Skeletal muscle movement
Somatic motor division, involves voluntary actions processed at
cerebrum or reflexes processed at the spinal cord
Neuroendocrine signals
Hypothalamus and adrenal medulla- secrete neurohormones that
influence motor output
Visceral responses
Autonomic division- brains stem and diecephalon stimulate
involuntary muscle and glands to maintain involuntary actions
needed for function of internal organs and homeostasis
Voluntary movement
Primary motor cortex and motor association- contralateral control,
also influence by behavioral and cognitive system

21. Each lobe has special functions- these are not equally shared
by the opposite lobe. Right handed people tend to have left
hemisphere dominance.
Figure 9-16

22. Modulator of sensory and cognitive processes – incorporates
the reticular formation, hypothalamus, limbic system, and regions
of the cerebral cortex
Neurons known as diffuse modulatory systems- regulate
brain function by affecting attention, motivation, wakefulness,
memory, motor control, mood, and metabolic homeostasis
In reticular formation in brain stem- most originate at brain stem
and innervate areas of the cerebrum and diencephalon, classified by
neurotransmitters used
Four modulatory systems
Adrenergic – secretes norepinephrine, originate at pons, modulate:
attention, arousal, sleep-wake cycles, learning, memory, anxiety,
pain, and mood.
Serotonergic – secretes serotonin, originate at brain stem midline,
modulate pain, movement, sleep-wake cycles, mood, emotion
Dopaminergic – secretes domamine, originate at midbrain, modulate
motor control and addictive behaviors
Cholinergic – secrete acetylcholine, originate at cerebrum and brain
stem, modulate sensory information pathways through thalamus,
arousal, sleep-wake cycles, learning, memory

23. See table 9-3 for
information on
neurotransmitter
function

24. Consciousness- a state of arousal in which the brain is aware of
self and environment
Reticular formation- actively interacting through ascending tracts
Anesthetics- block signals from reaching the reticular formation
Electroencephalograms (EGG)
Dectect level of activity of cerebral cortex neurons used electrodes
Awake State- various stage of awareness
Uncoordinate firing of cortical neurons due to ascending signals in
reticular formation results in low-amplitude high-frequency waves
As awareness declines signals the frequency of waves declines and
amplitute increases
Sleep- major rest period for the body, no external interaction,
easily reversible, brain is as active as when awake, sleep
inducing factors also boost immunity

25. Electroencephalograms
(EEGs) and the
sleep cycle
Wave frequency
lessens and
amplitude increaes
as arousal
diminshes
During sleep the
brain cycles
multiple types
between all stages
Delta waves are high
amplitude, low
frequency
Figure 9-20a

26. Four stages with two major phases
Slow-wave sleep – delta waves,
Adjust body without conscious commands
REM sleep
Brain activity inhibits motor neurons to skeletal
muscle, paralyzing them –also reducing homeostasis
responses
Dreaming takes place
Circadian rhythm
Suprachiasmatic nucleus- location of neurons that
signal light-dark cycle phases and responses

27. The link between emotions
and physiological
functions
The amygdala is the center
of emotion in the brain
Stimulus to Cerebrum-
creates perception, limbic
creates emotion,
cerebrum becomes aware
of emotion while
hypothalus stimulates
multiple responses
Figure 9-21

28. Defined as internal signals that shape voluntary
behavior (related to survival or emotions)
Some states known as drives create increased
arousal, goal-oriented behavior, and disparate
behavior to achieve the goal.
Works with autonomic and endocrine
responses to maintain homeostasis
Motivated behaviors stop
 Satiety
Pleasure is related to addictive behaviors which can be
changed if given a different motivation.

29. Similar to emotions but longer-lasting- related
to sense of being, not purely psychological, related
to sense of well-being and proper neurotransmitter
function
Mood disorders
Fourth leading cause of illness worldwide today
Depression
Sleep and appetite disturbances
Alteration of mood and libido
Antidepressant drugs alter synaptic transmission –
allow a neurotransmitter to remain at the synapse longer,
change the receptor, or the amount of NT released.

30. Learning has two broad types
Associative – links two stimuli or a stimulus to a behavior
Nonassociative- change behavior due to repeated exposure
Habituation – do not respond to an irritant stimulus, filters out
insignificant stimulus
Sensitization- enhanced response to irritant stimulus, helps avoid
harmful stimuli
Memory has several types
Short-term and long-term- combined by working memory,
consolidation turns short-term into long term. Changes in
synaptic connections are required
Reflexive and declarative- requires unconscious (procedural) or
conscious recall (infer, compare, evaluate). Declarative can
become reflexive

31. THANK YOU