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Hypothalamus and Limbic System

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imissyou419's version from 2017-01-30 03:28

Section 1

Question Answer
7 motivational states and behaviours associated with limbic systemHunger (Feeding),
Thirst (Drinking),
Feel Hot/Cold (Clothes - detected by hypothalamus and get urge to do something about it),
Feel tired (sleep),
Rage/fear (attack/defense),
Sexual arousal (mate),
Pain (avoidance)
Limbic systemring of phylogenetically old, primitive (reptilian) cortex around rostral border of brain stem, and its interconnecting structures (cingulate cortex, hypothalamus, amygdala, hippocampus). Concerned with emotion, certain motivational states and behaviours (homeostatic and instinctual drives) and memory.
Rabies virusattacks limbic cortex, patients have profound changes in emotional states, including bouts of terror and rage
What are some examples of limbic rage behaviour in daily life?fights (slap face), road rage
Pain goes where and what happens if there is lesion in 1 part of it?Pain goes up spinothalamic to somatosensory cortex (location, intensity, timing) and cingulate cortex (emotional component); If stroke in cingulate cortex (where some pain afferents terminate), feel pain but are not bothered by it
Hypothalamus, total volume, part of what?<1% of total volume of brain but has lots of functions, part of limbic system, connected to ANS and endocrine system
Hypothalamus receives input fromretina (suprachiasmatic nuclei), limbic system (b/c part of it), sensory info from body and environment through thalamus, circulating blood through receptors on hypothalamus, spinal cord through medulla
Leptin, what does it do? What happens in obese people?a hormone produced in fat storage cells, released from cells into blood and binds to leptin receptors in hypothalamus where it signals size of fat stores to reduce motivational feeding behaviour.
Obese people have insensitivity to leptin or have a mutation in gene for leptin or leptin receptor
How does hypothalamus release hormones?through posterior pituitary (axon where cell bodies are in hypothalamus) - oxytocin and ADH,
and through hypophysial portal veins to anterior pituitary for LH, FSH, ACTH, etc (FLAT PAG)
What receptors are on hypothalamus?hypothalamic osmolarity, gluco, temp, Na+, leptin receptors
4 Function of hypothalamus simply stated1. receives wide range of sensory info.
2. compares this sensory info with Set Points.
3. Coordinates a variety of Responses: Autonomic, Endocrine, Behaviour.
4. Maintains homeostasis.
5. Coordinates certain motivated behaviours
7 Major functions of hypothalamus KNOW THESE1. Regulation of body temp.
2. Control of BP and electrolyte composition.
3. Regulation of reproduction.
4. Control of energy metabolism.
5. Control of emergency response to stress.
6. Coordination of response to threatening situation (stimulation of lateral hypothalamus produces responses).
7. Control of cardiac rhythms (suprachiasmatic nucleus)
Lesion above midbrain (decerebrate)no spontaneous behaviours, no consciousness
If you remove cerebral hemispheres and leave hypothalamus and brainstem intactno consciousness but hypothalamic functions can occur (animal can maintain its homeostatic functions, defend itself, and reproduce which are instinctual/innate behaviours)
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Section 2

Question Answer
What is the autonomic for regulation of body temp?metabolic rate (sympathetic), cutaneous vasoconstriction (sympathetic)
What is the autonomic for control of BP and electrolyte composition?vasomotor tone
What is the autonomic for regulation of reproduction?genital response in sexual arousal, ejaculation
What is the autonomic for control of energy metabolism?metabolic rate (sympathetic), digestion (parasympathetic)
What is the autonomic for control of emergency response to stress?epinephrine (increase HR)
What is the autonomic for coordination of response to threatening situation (stimulation of lateral hypothalamus produces responses)pupils dilate, increased BP, vasoconstriction, raised hair (all sympathetic)
What is the autonomic for control of cardiac rhythm (suprachiasmatic nucleus)? Blood pressure, temp, ADH
What is the endocrine response for regulation of body temp?Thyroxine (thyroid)
What is the endocrine response for control of BP and electrolyte composition?ADH
What is the endocrine response for regulation of reproduction?Menstrual cycle, pregnancy, lactation
What is the endocrine response for control of emergency response to stress?cortisol
What is the endocrine response for control of circadian rhythm?hormone levels: ADH, cortisol, etc
What is the behavioural response for regulation of body temp?shivering (ANS), clothes, move to new environment (motivational behaviour)
What is the behavioural response for control of BP and electrolyte composition?Drinking, salt appetite
What is the behavioural response for reproduction?Mating, parental behaviour
What is the behavioural response for control of energy metabolism?feeding
What is the behavioural response for coordination of response to threatening situation (can be produced by stim of lateral hypothalamus)?Rage/fear behaviour
What is the behavioural response for control of circadian rhythm (suprachiasmatic nucleus)?sleep
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Section 3

Question Answer
Hypothalamus neural centreA particular physiological parameter is not controlled by 1 neural centre. E.g. there are neurons in the limbic system, hypothalamus, medulla and spinal cord that contribute to control of BP
Hypothalamus problems with stimulations and lesionsHypothalamus is small but packed with complex array of cell groups and axon pathways. Many ascending and descending pathways to and from cerebral cortex and brainstem passes through the hypothalamus. Some results of older stimulation and lesion studies have been found to be caused by involvement of the pathways passing through hypothalamus
Hypothalamus set pointset point for a variety of physiological processes including temp, blood sugar, sodium, osmolarity, hormone levels, body weight
e.g. Hypothalamus compares sensory input and circulating blood with biological set points and if it is too cold (decrease from set point), it activates autonomic (cutaneous vasoconstriction), endocrine (increase thyroxine), behavioural responses (shivering, moving to warmer environment)
Change in set point caused by damage (lesions) in hypothalamus (2)1. Fever. Pyrogens (interleukins) from bacteria reset the thermostat higher to try to kill bacteria. Paradoxical situation - high temp but fever pushes it higher. Treat with Tylenol, Advil or Aspirin (not aspirin in children).
2. Experimentally made lesion of ventral medial hypothalamus (changes set point for body weight so fat rat)
Hypothalamus feedforward controlGo into cold room with shorts on. Temp receptors in skin detect cold and sends info to hypothalamus. Hypothalamus activates heat conserving mechanisms BEFORE internal temperature (the regulated variable) begins to fall. Feedforward mechanism may be activated if a subject only thinks about going into cold room
What are the 2 advantages of feedforward control of hypothalamus?1. Improvement in speed of homeostatic response.
2. Minimize fluctuations in regulated variable. If feedforward worked perfectly, there would be no change in regulated variable
Is drinking and eating under feedforward or feedback control?Feedforward because you estimate you should drink that amount
What conditions are regulated under feedforward mechanisms?body temp, blood pressure, feeding (no negative feedback/homeostatic reflexes), controlled in part by feedforward signals originating from limbic cortex
Is hypothalamus involved in feedback mechanism?Yes, some hormones
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