Lesson 13: Limbic and Reticular System Flashcards Preview

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Flashcards in Lesson 13: Limbic and Reticular System Deck (65)
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1
Q

What does the reticular system do?

A

The reticular system is a group of nuclei that integrates information from sensory input from all the pathways and broadcasts it to everywhere, performing both sensory-sensory integration and sensory-motor integration.

  • Responsible for maintaining the homeostatic state of the brain - regulates visceral, sensorimotor, and neuroendocrine activities;
  • Regulates emotion, mood, cognition
  • Energizes reticular activating system
2
Q

Where does the reticular system span?

What is it connected to?

A

Spans the entire brainstem from the spinal cord to the cerebral cortex
It is connected with the vast regulatory system controlled by hypothalamus

3
Q

What do the groups of cells of the reticular system do?

A

Groups of cells collaborate for functional patterns such as coughing, eating, copulation, and fighting, a reminder of the functional pattern strategy of behaviour

4
Q

What does the ascending reticular activating system respond to?

A

The ascending reticular activating system responds to general sensory input establishing levels of alertness.

5
Q

How does the reticular system monitor the circadian rhythm?

A

The reticular system monitors and controls the circadian rhythm affected by secretions of melatonin from the pineal gland in the epithalamus giving the reticular activating system a role in sleep.

6
Q

How does the reticular system participate in attention of stimuli?

How is attention triaged?

A

Attentiveness: these nuclei screen sensory stimuli and regulate input by increasing or decreasing attention to various sensory stimuli
Assigns importance to incoming signals and effecting increased attention to those of importance, the vast sensory milieu in which we function is prioritized, allowing us to focus on things of current importance.

7
Q

How does the reticular system work with the hypothalamus, vagus nerve and others?

A

The reticular nuclei integrate many motor functions critical to survival, notably the respiratory centres. Voluntary respiration is controlled by the motor cortex in the frontal lobe

8
Q

How does the reticular system work with the glossopharyngeal and vagus nerves?

A

Use the nucleus of tractus solitarius to regulate respiratory activity

9
Q

How is the diaphragm related to the reticular system?

A

Is located between the thorax and abdomen, it descended during development. Its origin is close to the cervical vertebra C3, C4 and C5).
“3, 4, 5 keeps the diaphragm alive”.

10
Q

Where does injury have to occur where individuals cannot survive without constant artificial respiration?

A

Spinal cord injury above the C3, 4, 5 level

11
Q

Reticular system: Which two tracts are involved with muscle tone?

A

Reticulospinal tract and the vestibulospinal tract. They are constitutively active (always active). With the constant input from the vestibular system and the always-awake network of the reticular system, there are constant descending signals to keep us upright and “standing”

12
Q

Limbic system: what are the 4 main “hardwiring” of survival functions?
What are the main roles of the limbic system?

A

Basic elements of memory, olfaction, visceral functions, and emotion
Limbic projections to the forebrain contribute to emotions and provide motivation for behaviours that are fundamental to survival.

13
Q

Which circuit in the limbic system connects centres that coordinate the MOVE functions?

A

The Papez circuit

14
Q

What does the limbic system use to function?

A

This system relies heavily on the hypothalamus and the automatic nervous system.

15
Q

What is learning/memory?

A
  • Learning involves accumulation of new information or skills
  • Memory is the ability to retain and recall what was learned
16
Q

What type of memory: Memory of factual information or events. Easily acquired, readily forgotten. (Also referred to as explicit memory)?

A

Declarative memory

17
Q

What type of memory: Memory for skills, habits, emotional responses and reflexes?

A

Non-declarative memory

18
Q

What type of memory: A type of non-declarative memory for behaviour and skills. Requires practice, and is not easily forgotten. (Also referred as implicit memory)?

A

Procedural memory

19
Q

What type of memory: Temporary information storage that is limited in capacity, and requires constant practice?

A

Working memory

20
Q

What type of memory: Retention of information of facts or about recent events that is newly acquired and has not yet been processed into long term memory?

A

Short-term memory

21
Q

What type of memory: Memory about recent events or facts that have been processed for longer retention?

A

Long-term memory

22
Q

What type of amnesia: the inability to form new memory prior to the injury?

A

Retrograde amnesia

23
Q

What type of amnesia: inability to form new memory after the injury?

A

Anterograde amnesia

24
Q

What are some sources of memory impairment?

A
  • Formation of new memory that is selectively damaged with head injury.
  • Nutritional damage to the temporal lobes (which is therefore bilateral) as seen with alcoholism or general aging produces significant memory impairment.
  • Alzheimer’s disease, declarative memory is lost before non-declarative memory
25
Q

What role does the viscera play? What are some examples?

A

From the time in which hunger signals the need to find food to the time that food is found and the entire gastrointestinal tract participates in feeding, the viscera play a role in satisfaction of drives.

26
Q

How is the olfactory system important to the limbic system?

A

Infant finding the breast, animals foraging for food, remembering eating something that makes them ill, recognizing the scent of fear, to the effect of scents on reproductive behaviour, smell is very important to survival

27
Q

What is the role of the septal nuclei in the viscera?

Which structures is it involved with?

A

Play an important role in reward. These septal areas involving an experience of “reward” are involved in substance abuse.
Connecting the limbic lobe to the hypothalamus, thalamus, and midbrain.

28
Q

What are the tegmentum in the brainstem connected to in the visceral system?

A

-On the Papez circuit - tegmentum (core) of the brainstem connecting the hypothalamus and mammillary bodies with the reticular system and cranial nerve nuclei (especially CN X)

29
Q

What role does the amygdala play in emotion?

A
  • Directly controls drive and motivation associated with visceral brain activities and accompanying internal feelings
  • Can produce all the behaviours that are elicited from the hypothalamus – ex. blood pressure and heart rate change
  • motor activities such as head movements, circling, licking, chewing and swallowing.
30
Q

What are the structures that make up the limbic system? (4 generally; 8 specifically)

A

Functional structures of the limbic lobe, diencephalon, septum and midbrain. Includes the subcallosal gyrus, cingulate gyrus, isthmus, parahippocampal gyrus, hippocampus, olfactory cortex, uncus and amygdala.

31
Q

What type of network are the key limbic structures connected to?

What do they account for?

A

Connected by an extensive network of afferent and efferent fibers. These account for the limbic influence on virtually all cortical, brainstem, as well as visceral functions and the regulation of emotions and motivation.

32
Q

What is the major input/output of the limbic system?

A

Inputs: neocortex, olfactory bulb, thalamus, hypothalamus, septum and RF.
Output: neocortex, hypothalamus, thalamus, and RF.

33
Q

What do projections of the prefrontal lobe in the neocortex regulate? Projections to the hypothalamus?

A

Projections to the prefrontal lobe in the neocortex regulate affective aspects of emotion.
Projections to the hypothalamus and RF regulate ANS activities and motor aspects of emotions.

34
Q

What are the major ascending and descending pathways of the limbic system? (7)

A

Medial forebrain bundle, stria medullaris, stria terminalis, mammillothalamic tract, mamillotegmental tract, fornix, and medial longitudinal fasciculus.

35
Q

Which pathway: forms the limbic-thalamic pathway, which reciprocally connects the septum with the thalamus?

A

Stria medullaris

36
Q

Which pathway: mediates limbic outputs from the hypothalamic mammillary bodies to the neocortex via the anterior nucleus of the thalamus?

A

Mamillothalamic tract

37
Q

Which pathway: circulates limbic information from the cingulate gyrus to the parahippocampal gyrus and then to the hippocampus?

A

Cingulum

38
Q

Which pathway: connects the hypothalamus with both the hippocampus and olfactory cortex?

A

Fornix

39
Q

What structures is the amgydala reciprocally connected to?

What does it project to?

A

Hypothalamus, RF, olfactory system, orbital region, hippocampal formation, and neocortex.
Projects to medial dorsal nucleus of thalamus, septum, cingulate gyrus and prefrontal regions

40
Q

What is Kluver-Bucy Syndrome?

A

Indiscriminate eating, oral exploration, psychic blindness, and inappropriate hypersexuality

41
Q

What are the principal sources of afferents to the hippocampus?
Where do impulses to the hippocampus travel?

A
  • Polysensory association cortical areas.

- Parahippocampal and occipitotemporal gyri.

42
Q

What are the primary efferents from the hippocampus?

A

Amygdalae, septum, thalamus, and hypothalamus

43
Q

Where does the cingular gyrus receive projections from?

A

It receives projections form the hypothalamic mammillary bodies by way of the mamillothalamic tract and the anterior thalamic nucleus.

44
Q

Where does the cingulate gyrus project to?

A

Projects to the hypothalamic mammillary bodies via the fornix fibers that arise in the entorhinal cortex.

45
Q

What vital portal entry does the fornix provide?

What does the fornix do?

A

Provides a vital portal entry connecting the limbic lobe to the diencephalon and brainstem.
- Processing autonomic, visceral, endocrine, sensorimotor reproductive, neurotransmitter, emotional and motivational functions

46
Q

What are the two parts of the septum?

What is the name of its continuum?

A
  • Dorsally, it consists of a midline fibrous sheet attached to the corpus callosum.
  • Ventrally, it consists of a collection of nuclei.
  • sept-hypothalamus midbrain continuum
47
Q

What is the reticular formation composed of?

A

Composing most of the brainstem (medulla, pons and midbrain), it is also functionally wired to nuclei in the thalamus and spinal cord

48
Q

What do the neuronal circuits of the RF do?

A

Converge or diverge to inhibit, facilitate, modify and regulate all cortical functions; they also integrate all sensorimotor stimuli with internally generated thoughts, emotions, and cognition.

49
Q

How are the brainstem reticular cells arranged in the median, medial and lateral columns?

A

Median cell column: contains the midline nucleus raphe, which forms a continuous cellular column in the brainstem and consists of regions that provide projections to the brain and spinal cord
Medial cell column: consist of a central group of reticular nuclei, including gigantocellular reticular nucleus
Lateral cell column: contains small to intermediate-size nuclei

50
Q

What do the afferents of the RF consist of? (10)

A

Collaterals from the ascending and descending spinal tracts, cranial nerve nuclei, cerebellum, midbrain, thalamus, subthalamus, hypothalamus, striatum, limbic lobe, and various cortical areas

51
Q

Where does the RF send projections?

A

To somatic and autonomic nuclei in general, autonomic and somatic motor nuclei of cranial nerves in the brainstem, and interneuronal pools in the spinal cord.
Also places like cerebellum, red nucleus, substantia nigra, midbrain tectum, subthalamic nuclei, thalamus, hypothalamus, limbic lobe, forebrain

52
Q

Which cells of the ascending RAS contribute to cortical arousal?

A

Serotonergic, cholinergic, and catcholaminergic cells and their projections from the brainstem to the neocortex and limbic structures

53
Q

Where are most coma or altered consciousness-causing lesions?

A

Midbrain, hypothalamic and thalamic junctions

54
Q

How do the reticular projections modulate sensory information?

A

Modulate the quantity and quality of sensory information and employ a gating mechanism that screens information at both the spinal and thalamic levels
Direct reticular projections influence information processing by either accentuating or attenuating the sensory stimuli.

55
Q

How is cardiovascular activity controlled by the reticular nuclei?

A

Project info via fibres of the vagus nerve (CN X). Stimulation of the lateral reticular pressor centre increases heart rate and causes vasoconstriction. Stimulation of the depressor centre in the lower medulla decreases heart rate and causes vasodilation.

56
Q

How is respiration controlled by CO2?

A

Higher CO2 in the blood stimulates the respiratory centre through inspiratory and expiratory signals to the respiratory muscles

57
Q

How are the voluntary and automatic respiration mechanisms controlled?

A
  • Nuclei forming the voluntary respiratory control centre are in the motor cortex.
  • Autonomic brainstem respiratory centre is formed by several groups of scattered neurons in the pontomedullary RF
58
Q

How is reflexive breathing initiated?

A

Descending signals from respiratory network to spinal motor neurons initiate reflexive breathing and control respiratory activityEfferent projections from C3-C5 form phrenic nerve – causes contraction of the diaphragm (increases intrathoracic volume, beginning cycle of inspiration

59
Q

What are the 4 components of reflexive respiration?

A

Regulation of respiratory rhythm, regulations of inspiratory-expiratory phases, and phase switching between inspiration and expiration.

60
Q

What does the inspiratory phase consist of?

A

Contraction of diaphragm and external intercostals increases the intrathoracic volume, lowers pressure within the lungs and thoracic cavity. Reduced intrathoracic pressure forces air (inhalation) into the lungs.

61
Q

What does the expiratory phase consist of?

A

Exhalation is initiated by an increase in intra-abdominal pressure and a decrease in intrathoracic volume caused by the abdominal and internal intercostal muscles.

62
Q

Which nerves are involved in swallowing? (5)

How does it work?

A

Trigeminal (CN V), facial ( CN VII), glossopharyngeal (CN IX), vagus (CN X), and hypoglossal (CN XII)
- Swallowing is a reflexive action instigated by the sensory and motor components of these cranial nerves along with reticular participation. Has two stages - voluntary and involuntary

63
Q

What nuclei regulate vomiting?

How does it work?

A
  • Reticular nuclei are in the medulla that regulate vomiting
  • Projections from the vomiting centre in the medulla descend through the fibres of the glossopharyngeal (CN IX) and vagus nerve (CN X) and coordinate the contraction of the abdominal, diaphragmatic, and intercostal muscles
64
Q

How is the coughing reflex initiated?

A

-Afferents mediating irritation from laryngeal and tracheal lining tissues initiate the coughing reflex via the vagus nerve (CN X) and solitary tract nuclei.

65
Q

How does the RF contribute to self-awareness with the superior colliculus?

A
  • Input stems from overlapping visual, auditory, and somatic stimuli, representing various temporal and spatial reference points surrounding the body
  • These stimuli form a 3-D body image in the midbrain RF