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Module 14 NBL 655 hypothalamus, brainstem, etc

Terms in this set (58)

--The overarching function of the hypothalamus is integration and control of body functions for survival and reproduction.

--The hypothalamus acts as an integrator to regulate basic life- and species-sustaining functions such as fluid and electrolyte balance, drinking and feeding behavior, energy metabolism, thermoregulation, stress responses, and sleep-wake cycles, as well as sexual behavior and reproduction.

--To produce control over so many bodily functions, the hypothalamus uses 3 major outputs: 1) the behavioral
2) autonomic
3) endocrine systems.

--The hypothalamus receives sensory inputs necessary for the detection of changes in both the internal and external environments and controls behaviors related to those inputs.

--In addition, regions within the hypothalamus contain sensors for blood sugar, temperature, and ion levels and receptors for stress and appetite hormones.

--As part of the limbic system, the hypothalamus receives inputs from the hippocampus, amygdala, and cingulate cortex, which provide highly processed sensory and salience information from the rest of the cerebral cortex.
--These inputs to the hypothalamus contribute to a range of emotional responses, feelings, and expressions, as well as behaviors such as aggression and motivational behaviors, such as drinking, feeding, and sexual behaviors.

--Well interconnected with the brainstem and spinal cord, the hypothalamus is also involved in control of the autonomic nervous system (ANS).

--The hypothalamus links the nervous system to the endocrine system via the pituitary gland, which releases hormones into the bloodstream and consequently controls many physiologic functions of the body.
--Some neurons in the hypothalamus send their axons to form the posterior pituitary where they secrete oxytocin and vasopressin directly into the circulation.
--Other neurons in the hypothalamus send axons that release hypothalamic hormones, which act on the anterior pituitary to regulate secretion of specific anterior pituitary hormones into the circulation.

--Another key function of the hypothalamus is regulation of body functions in concert with the daily light-dark cycle, in which the suprachiasmatic nucleus is responsible for entraining circadian rhythms to the day-night cycle.
Considered one of the most primitive parts of the human brain, the brainstem (or brain stem) is the structure most important to life.

--The brainstem contains nuclei, which are essential for automatic, reflex, and autonomic functions that are critical for survival, and white matter tracks that connect the forebrain with the cerebellum and spinal cord.

--The white matter tracts are involved in transmission of motor impulses that control the body and head and the largest majority of sensory tracts.

-- In addition, 10 of the 12 pairs of Cranial Nerves emerge directly from the brainstem, with nuclei involved in both somatic motor and sensory functions of the head, face, and neck and in autonomic parasympathetic functions.

--The brainstem also contains nuclei involved in essential automatic processes, including breathing and nuclei for the control of cardiac, vascular and respiratory function, helping to control heart rate, blood pressure and breathing rate.

--It also contains the reticular formation, a group of nuclei located from the upper midbrain to the lower medulla that function in arousal, alertness, sleep and wakefulness, consciousness, and other motor and sensory functions.

--the midbrain contains the substantia nigra and ventral tegmental area, two regions that contain dopaminergic neuron cell bodies that contribute to the basal ganglia and are involved in motor control, and motivation and reward pathways.

--The pons contains the locus coeruleus, which contains the cell bodies of norepinephrine neurons (noradrenergic neurons).

--The Raphe nuclei, which contain the cell bodies or serotonergic neurons, are located in the midbrain, pons and medulla.
--An important role of the frontal lobe is to produce cognitive functions that orchestrate thoughts with the selection of appropriate actions to achieve particular goals.
--The two major areas in the frontal lobe are the motor cortex and the prefrontal cortex. We already covered the motor cortex in Module 13.
--It is the function of the prefrontal cortex to predict outcomes, project future consequences resulting from current activities, work toward a defined goal, make expectations based on actions and evaluate the consequences of a particular course of action, differentiate among conflicting thoughts, determine similarities and differences between things or events, choose between good (or better) and bad (or worse) actions, suppress impulses, and override and control socially unacceptable responses.
--The prefrontal cortex is involved in what are termed executive functions, including attentional control, short-term working memory, self-control and moderation of social behavior, decision making, judgment, planning, reasoning, problem solving, and abstract thinking, as well as the expression of emotion and personality.
--These cognitive functions require the prefrontal cortex but also involve other cortical and subcortical regions as well.
--Though we often think about the prefrontal cortex as mainly involved in the executive functions of decision making and problem solving, it also has major roles in cognitive, behavioral and emotional control.

--The prefrontal cortex can be divided into four main regions (also called domains) and each of these regions consists of particular gyri and sulci, and have specific functions.
--There are two regions in the dorsal prefrontal cortex: the dorsolateral prefrontal cortex (dlPFC) and dorsomedial prefrontal cortex (dmPFC).
--There are two regions in the ventral prefrontal cortex. One is the ventromedial prefrontal cortex (vmPFC), which is considered anatomically synonymous with the orbitofrontal cortex (OFC), and will be referred to as the OFC/vmPFC.
--The other is the ventrolateral prefrontal cortex (vlPFC).
--The prefrontal cortex is highly interconnected with much of the brain, including extensive connections with other cortical, subcortical, and brainstem regions.
--The prefrontal cortex receives massive inputs from the somatosensory, visual, and auditory sensory association cortices and also from the thalamus.
--The dorsal prefrontal cortex is especially interconnected with brain regions involved with attention, cognition, and action, whereas
--the ventral prefrontal cortex interconnects with brain regions involved with emotion.

Dorsal Regions:
--The DLPFC has connections with the OFC/vmPFC, thalamus, basal ganglia, hippocampus, and association areas of the temporal, parietal, and occipital lobes.
--An important function of the DLPFC is executive functions, such as working memory, decision making, planning, cognitive flexibility, inhibition, and abstract reasoning.
--However, the DLPFC is not exclusively responsible for these executive functions.
--All complex mental/cognitive activity requires the additional cortical and subcortical circuits with which the DLPFC is connected.
--The DLPFC is also the highest cortical area that is involved in motor planning, organization and regulation.

--The dmPFC is identified to play a variety of roles including processing a sense of self, integrating social impressions, theory of mind, morality judgments, empathy, decision making, altruism, fear and anxiety information processing, and top-down motor cortex inhibition. The dmPFC also modulates or regulates emotional responses and heart rate in situations of fear or stress and plays a role in long-term memory.

Ventral regions:
--The OFC/vmPFC has direct connections to the thalamus, amygdala, and cingulate cortex of the limbic lobe and are thought to be involved in impulse control and to provide the emotional and reward components to decision making, planned behavior, and memory.
--Other functions include the processing of risk and fear, as it is critical in the regulation of amygdala activity.
--It also plays a role in the inhibition of emotional responses, and in the process of decision making, self control, and the cognitive evaluation of morality.
--The vlPFC is thought to play a critical role in motor inhibition and spatial attention.
--Also, the vlPFC is the end point of the ventral pathway (stream) that brings information about the stimuli's characteristics.

-- Though the ACC is not a part of the prefrontal cortex, the ACC lies in a unique position in the brain, with connections to both the "emotional" limbic system and the "cognitive" prefrontal cortex.