Limbic System & Hypothalamus/ Pituitary Gland (Exam 2) Flashcards
What is the limbic system?
Collection of cortical & subcortical structures located in medial & ventral regions of cerebral hemispheres
- Extend from forebrain to brainstem
What makes up the limbic lobe?
Cingulate gyrus and parahippocampal gyrus
What are the 4 functions of the limbic system?
- Homeostatis
- Olfactory
- Memory
- Emotion
What are the main components of the Limbic system?
- Limbic cortex
- Hippocampal formation
- Amygdala
- Olfactory cortex
- Diencephalon
- Septal Nuclei
- Brainstem
- Basal ganglia
- Basal forebrain
What is the function of the cingulate gyrus and the parahippocampal gyrus in the limbic cortex?
- Cingulate gyrus: Memory, emotional processing and autonomic nervous system
- Parahippocampal gyrus: memory processing
What are the 3 parts of the hippocampal formation and where are they located?
- Located on medial temporal lobe
1. Dentate gyrus
2. Subiculum
3. Hippocampus
What is the hippocampal formation involved in?
Memory
What are the functions of each part of the hippocampal formation?
Dentate Gyrus: Afferent (Input)
Subiculum: Efferent output
Hippocampus: Efferent output
What is the amygdala involved in?
- Emotions
- Behaviors
- Emotional response to smell and more
What are the nuclei of the amygdala?
- Corticomedial nucleus (olfaction)
- Central Nuclei (autonomic control)
- Basilar nuclear group (all other emotions)
What is within the hypothalamus?
- Mammillary Bodies (main nuclei involved in limbic pathways)
- ANS nuclei (give rise to para & sympathetic pathways)
What are 2 nuclei involved in the thalamus and what is their function?
- Anterior nucleus (memory)
- Mediodorsal (emotions & behavior)
What is the septal area?
Connected to Habenula, part of reward pathways and involved in dopamine & serotonin
What is an association cortex?
Cerebral cortex that is not directly involved with sensation or movement
- Prefrontal cortex & anterior temporal cortex
For each main limbic function what is the key structure associated with:
Olfaction
Memory
Emotion & drives
Homeostasis (autonomic & neuroendocrine control)
Olfaction: Olfactory cortex
Memory: Hippocampal formation
Emotion & drive: Amygdala
Homeostasis: Hypothalamus
What is the vascular system of the limbic system and what does each artery supply?
- Anterior cerebral artery (medial surface of frontal & parietal lobe)
- Posterior cerebral artery (medial, inferior surface of the temporal lobe)
- Anterior choroidal (cingulate, parahippocampal, amygdala)
- Branches off circle of Willis (hypothalamus, anterior commissure)
What is the fornix involved in and what is the pathway?
- Involved in memory pathways
- Goes from hippocampus formation to septal area OR to mammillary bodies of hypothalamus
What is the mammillothalamic tract involved and where does it travel?
- Involved in memory pathways
- Travels mammillary bodies of the hypothalamus to the anterior nucleus of the thalamus
Describe the Stria Terminalis: long way
- Amygdala Pathway
Goes from amygdala to septal area OR hypothalamus
Describe the Ventral AmygdaloFugal Pathway: Short cut
- Amygdala Pathway
Amygdala to Septal Area OR hypothalamus OR Mediodorsal nucleus of the thalamus
What is the Medial Forebrain Bundle involved in and describe the pathway?
- Involved in sending info about behaviors, emotions & personalities to the brainstem and back
- Goes from Amygdala to Hypothalamus to Brainstem
What is the only sensation to pass the thalamus?
Olfaction
What is the function of the olfaction?
Smell contributes to sensation of odors & to sensation of taste
Describe the overview of the Olfactory System
Smell stimulus –> activates Olfactory Receptors –> Olfactory nerves –> through cribriform plate of the ethmoid bone –> Olfactory bulb
After the olfactory bulb is stimulated, sends action potential down the olfactory tract and projects via what? And to where?
Via the medial and lateral olfactory stria
To the:
- Primary olfactory cortex
- Orbital Frontal Olfactory Cortex
- Corticomedial nucleus of the amygdala
- Parahippocampal gyrus
What does the primary olfactory cortex receive direct input from?
Secondary sensory neurons without an intervening thalamic relay
What is the function of the Corticomedial nucleus of the amygdala and the parahippocampal gyrus?
Corticomedial nucleus: Emotional & motivational response related to smell
Parahippocampal (enterohinal cortex): Evoke vivid memory of smells
Along with medial temporal lobes what is responsible for declarative memory?
Hippocampal Formation
What does the intrinsic circuity of the hippocampus formation play a role in?
Memory formation and processing
Hippocampal formation has important connections to prefrontal association cortex so memory is involved in what?
Decision making
Consult your memory to make sure this is the right decision
What is papez ciruit responsible for?
Memory processing and learning
Describe the Papez Ciruit
Subiculum (output) of the hippocampus –> through fornix to Mammillary Bodies of the Hypothalamus –> through the mammilo- thalamic tract to anterior nucleus of the thalamus to –> upward cingulate sulcus and prefrontal association cortex –> to parahippocampal gyrus (enterohinal) –> to dentate gyrus of the hippocampus
What is retrograde amnesia?
- Loss of memories for events that occurred before the trauma or disease
- Retrieving memories from 1-12 years ago (medial temporal lobe)
- Retrieving memories from 13-30 years ago (prefrontal, parietal, & temporal association cortex)
What is anterograde amnesia?
Loss of memory following an event
(Medial temporal lobe)
What is wernicke’s Encephalopathy/ Wernicke Korsakoff Syndrome?
Destruction of mammillary bodies of hypothalamus due to thiamine (B1) deficiency (alcoholism)
- Sxm: profound memory loss, confabulation, impulsive, eye movement abnormalities, ataxia
What is Alzheimer’s Disease?
Bilateral hippocampal, temporal & basal forebrain structures disruption of cholinergic neurons resulting in progressive dementia/memory loss
What psychogenic amnesia?
Memory loss for events of particular emotional significance
In patients presenting amnesia with TBI what structures are injured?
Those involving memory
- Upper brain stem for arousal (reticular formation): need to pay attention
- Hippocampus: lay down new memory
- Frontal Lobes: retrieve these memories
In patients with amnesia with TBI what happens because of excess neurotransmitters?
- Overload causes less neurotransmitter being used for attention & memory
- Later in recovery (these neurotransmitters become deficient and healing varies)
What is effected in an anoxic brain injury?
- Hippocampus, cerebellum & basal ganglia with worse prognosis
What are some treatment for patient with amnesia with a TBI?
- Use organizers, checklists, cell phone calendars
- Memory station: keep keys, wallet there
- Reduce distractions
- Ask other to speak slowly & repeat
What is a seizure?
High frequency electrical discharge and firing of neurons in brain resulting in abnormal experience or behavior
What are the two types of generalized seizures?
Grand mal or Tonic-clonic seizure
What is the difference between the tonic and clonic phase?
Tonic: all muscles stiffen & person falls over
Clonic: rhythmic bilateral jerking
What is the symptoms of a Ictal autonomic response?
- Tachycardia
- HTN
- Hypersalivation
- Pupillary dilation
What are the symptoms post- ictal?
- Fatigue
- Amnesia
- Headache
- Deep breathing to compensate for respiratory acidosis
What is the difference between a simple and complex seizure?
Simple: aware during seizure & symptoms depend on brain region
Complex: Impaired consciousness & affects a wider ares
In a simple seizure what will the right motor cortex hand area cause and what will the visual association cortex?
Right motor cortex hand area: hand twitching
Visual association cortex: hallucinations
Where are seizures common?
Medial Temporal lobe
What are some causes of seizure?
- Genetic
- Fever
- Head trauma
- CVA
- Infection
- Electrolyte abnormality
What are some treatment options of seizures?
- Meds
- Surgery
- Ketogenic diet
- Neurostimulation
- Hemisperectomy in under 2-3 y/o
A patient may report an aura before seizures, what is that?
Visceral sensation in epigastric area, feeling of déjà vu, strange/unpleasent odors, feelings of extreme dear & anxiety
When may memory loss happen during seizures?
repeated resulting in hippocampus sclerosis
How may symptoms present during seizures on contralateral & ipsilateral?
Contra: dystonia
Ipsi: automatisms (repetitive behavior such as limb patting or stroking or lip smacking)
What is the function of the amygdala in emotional response?
In a situation where you feel fear, anger, rage, sadness the amygdala needs to communicate with other structures
How do the amygdala and olfaction interact?
- Emotional & motivation aspects of olfaction
- Goes from amygdala to the olfactory bulb
How do the hippocampus and amygdala interact?
- Hippocampal formation & amygdala have reciprocal connections
- Amygdala attaches emotional significance to memories (more likely to remember if a memory is linked with emotion)
Where does the amygdala receive info from that gives specific emotion?
- Association cortex
-prefrontal cortex (reasoning, judgement, decision making, personality, behavior)- Somatosensory association cortex
- Visual association cortex
- Auditory association cortex
- Olfactory association cortex
- Temporal Lobe (memory)
Where is the voluntary ability to regulate emotions?
Through lateral prefrontal cortical areas
What is the long way of the amygdala pathways?
- Stria Terminalis
- Fornix of the amygdala
- Travels along the wall of the lateral ventricle (C-shaped)
What is the shortcut of the amygdala pathway?
- Ventral Amygdalofugal Pathway
- Also provides input to the mediodorsal nucleus of the thalamus
Both the stria terminals and ventral amygdalofugal pathway travel to/from amygdala to/ from where?
- Septal area
- Hypothalamus
- Then goes to other areas including brainstem, basal ganglia & prefrontal association cortex to guide decisions, behaviors & movement
Amygdala sends information to hypothalamus via stria terminals or ventral amygdalofuglal pathway, what behaviors does it control?
- Appetite (satiety or hunger)
- Sexual behavior to release oxytocin or gonadotropin
Besides the amygdala what two main areas are involved in the reward seeking pathway?
- Medial Prefrontal Cortex
- Ventral Striatum
What does lesion or dysfunction in ventral striatum cause?
-Apathy
-loss of initiative
- spontaneous thought
- emotional response
What does excessive activity in ventral striatum cause?
Obsessive compulsive disorder
Hypothalamus connections are important for what 3 mechanisms?
- Emotional influence on autonomic pathways
- Homeostasis including immune function
- Homeostasis as it related to motivation & reproduction
How does the mesolimbic pathway work?
- Ventral Tegmentum to Ventral Striatum
–> communicate with ventral tegmental area (midbrain) –> send dopaminergic neurons –> nucleus accumbens
How does the cortico-basal ganglia thalamic circuit/mesocortical pathway work?
- VTA to medial prefrontal association cortex
–> communicates with ventral tegmental area –> send dopaminergic neurons –> medial dorsal thalamic nuclei –> medial prefrontal cortex
Overall how does the reward seeking pathway work?
Dompaminergic neurons from ventral tegmental area (VTA) in the midbrain to the ventral striatum and medial prefrontal cortex
What do people with addiction have lower numbers of?
- Lower levels of dopamine receptors than typical people
in depression what region is hypoactive?
Ventral striatum
In OCD what region is hyperactive?
Ventral striatum
In anxiety what region is hyperactive?
Amygdala
What homeostatic change is seen with emotion?
Really scared: shaking, pilo errection
Embarrassed: cheeks get red (vasodilation)
Nervous: blotchy, sweaty
What nuclei of the amygdala sense the emotion of fear & anxiety?
Central nuclei
Describe the homeostasis pathway: autonomic response
Hypothalamus via (stria terminalis or ventral amygdalofugal)
Descending autonomic fibers go to brainstem (via medial forebrain bundle)
Synapse onto: parasympathetic nuclei (brainstem & sacral region) & sympathetic nuclei (T1-L2 in thoracolumbar region)
What is within the diencephalon?
- Thalamus
- Hypothalamus
- Epithalamus
- Subthalamus
What functions is the hypothalamus involved in?
- Homeostasis
- Endocrine
- Autonomic
- Limbic
what effect does the hypothalamus have on homeostasis ?
-Circadian rhythms
- Appetite
- Thirst
- Drive
What is the function of the hypothalamus in endocrine control?
Release hormones and stimulatory/inhibitory factors to pituitary
What is the function of the hypothalamus in autonomic nervous system?
Descending projection influence sympathetic & parasympathetic divisions of the ANS
What function does the hypothalamus have on limbic system?
Emotions & memory
What structures are involved in homeostasis?
Behaviors via connection with limbic & release of hormones
What structures are involved in endocrine control?
Hypothalamic - Pituitary feedback loop control the release of hormones
What structures are involved in the autonomic nervous system?
Medial forebrain bundle
What structures are involved in the limbic system?
Connections with amygdala via: stria terminalis & ventral amygdalofugal pathway
Hippocampus to mammillary bodies (fornix)
Mammillary bodies to anterior thalamic nuclei (mammillothalamic tract)
What hormones are released from Anterior Pituitary Gland?
- Adrenocorticotropic hormone (ACTH)
- Growth hormone (GH)
- Prolactin
- Thyroid- stimulating hormone (TSH)
- Luteinizing hormone (LH)
- Follicle- stimulation hormone (FSH)
What does ATCH do?
- Stimulates adrenal cortex to produce corticosteroid hormones
- Important for BP & electrolyte regulation
What does GH do?
Stimulate organs to secrete hormones to promote growth in long bones & other tissues
What does prolactin do?
Mammillary glands to produce milk
What does TSH do?
Cellular hormone
What does FSH do?
- Regulate ovarian hormones for mentration & ovulation in females
- Regulate testicular hormones & spermatogenesis in males
Where is antidiuretic hormone released from and what does it do?
-Posterior pituitary gland
- Increase reabsorption of water in kidney
- Allows concentration of urine
Where is oxytocin released and what does it do?
- Posterior pituitary gland
- Stimulates smooth muscle in uterus
- Elicits milk expulsion in lactating females
What are some things that pituitary tumors can cause?
- Headaches
- Nausea & vomitting
- Irregular menses & lactation
- Secular dysfunction
- High blood pressure
- Increased glucose
- Acromegaly
- Cushings disease
- Bitemproal hemianopia
