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Nervous System: Unit III > Hypothalamus & Temperature Regulation > Flashcards

Flashcards in Hypothalamus & Temperature Regulation Deck (20):
1

Pathways connecting hypothalamus to autonomic systems

  • Fibers travel in dorsal longitudinal fasiculus
  • Hypothalamic neurons ==> preganglionic neurons of the SNS and PNS
  • Sympathetic: The preganglionic neurons of the sympathetic nervous system are located in the intermediolateral column of the thoracic and upper 3 lumbar segments of the spinal cord (T1-L3),
  • Parasympathetic:  the preganglionic neurons of the parasympathic nervous system are located in brainstem nuclei and in the sacral spinal cord.  

2

Pathways connecting hypothalamus to somatic motor system

  • Hypothalamic neurons==> reticular formation near the motor nuclei of the cranial nerves
  • somatic motor neurons in turn innervate skeletal muscle.
  • By coordinating activity in these neurons with actions of autonomic neurons ==> organize and initiate complex activities that require both somatic and autonomic responses
    • e.g. vomiting, laughing, crying, and facial expressions
    • activities required for maintenance of homeostasis such as chewing and swallowing.

3

Efferent tracts of the hypothalamus (to autonomic/somatic nervous system)

  • Dorsal longitudinal fasiculus: to autonomic nuclei in the brainstem reticular system and spinal cord
  • Medial forebrain bundle: to brainstem reticular formation (somatic motor)
  • Mammillotegmental tract: from the mammillary bodies to the midbrain reticular formation (tegmentum)

4

Pathways connecting hypothalamus to endocrine system

  • hypothalamus regulates hormone release from anterior nad posterior lobes of pituitary
  • anterior pituitary
    • hypothalamus synthesizes adn releases hormones into the hypothalamo-pituitary portal circulation ==> 
    • release of hormones from glandular cells of ant. pituitary
  • posterior pituitary
    • neurons from supraoptic and paraventricular nucleus ==> vasopressin & oxytocin ==> 
    • stored @ posterior pituitary until release

5

Pathways connecting hypothalamus w/limbic system

  • Connection w/limbic system ==> appropriate initiation of motivated behaviors + integration of emotion and sensation
  • Fornix: afferent/efferent connections between hippocampus and mamillary bodies
  • Stria terminalis: afferent/efferent connections between amygdala and the anterior and tuberal regions of hypothalamus
  • Medial forebrain bundle: afferent/efferent connections between hypothalamus and prefrontal cortex and septum
  • mamillothalamic tract is an efferent pathway connecting the mammillary bodies with the anterior thalamus.


     

6

Role of autonomic nervous system in homeostasis/emotion response (general)

1. Somatic reactions -- escape, fighting, biting, hissing, facial expressions

2. Autonomic reactions -- blushing, dryness of mouth, sweating, GI reactions, fainting

3. Endocrine reactions -- activation of adrenal cortex and medulla

7

Role of autonomic nervous system in emotions

  • SNS:
    • Blushing - vasodilation
    • Fainting - vasodilation
    • White face- vasocontriction
    • Sweating
    • Dry mouth
  • PNS: GI effects - butterflies

 

8

Role of autonomic nervous system in homeostasis

  • body temp = sweating regulation
  • water balance = H2O reabsorption 
  • body weight/hunger = stomach growling

9

Characteristics of neuroendocrine fxn of hypothalamus/control of anterior pituitary

  • (midline/paraventricular regions) hypothalamus synthesizes/releases hormone ==> hypothalamo-pituitary portal circulation ==> release of hormones from anterior pituitary
  • ant. pituitary hormones ==> regulate hormones @ peripheral endocrine organs 
  • thus, hypothalamus indirectly regulates most of endocrine system

10

Characteristics of neuroendocrine fxn of hypothalamus/control of posterior pituitary

  • hormones of the posterior pituitary, vasopressin/ADH and oxytocin are made by neurons in the supraoptic (SON) and paraventricular nuclei (PVN)
  • They are transported down the axons of these neurons to the posterior pituitary where they are released directly into the general circulation for transport to their distant target tissues.

 

Vasopressin acts on the kidneys to increase water reabsorption and on the vasculature to cause vasoconstriction. Oxytocin causes constriction of smooth muscle in the uterus and mammary glands and thereby plays important roles in parturition and lactation.

 

11

Endocrine response (initiated by hypothalamus) : body temp regulation, water balance, body weight regulations

  • body temp = thyroxin
  • water balance = vasopressin
  • body weight regulation = insulin/glucagon (ANS) & epinephrine

12

Somatic motor  (initiated by hypothalamus) : body temp regulation, water balance, body weight regulations

  • body temp
    • exercise (voluntary)
    • shivering (involuntary)
    • drinking warm liquid, using blankets
    • seeking cool environment
  • water balance
    • thirst ==> drinking beverages
  • body weight regulation
    • hunger ==> chewing/swallowing

13

Fever and Pyrogen definition

  • fever = regulated increase in body temp
  • pyrogen = fever-producing agents

14

Hypothalamic mechanisms ==> fever

  • Fever is produced by the actions on the POAH of one or more of the cytokines (interleukin 1 [IL-1], interleukin 6 [IL-6], tissue necrosis factor [TNF] and interferon).
  • IL-1 acts in a non BBB region in the hypothalamus: the OVLT (organumvasculosum of the lamina terminalis).
  • ==> endothelial cells in this region to produce prostaglandin E2.
  • PGE2 ==> POAH and decreases the activity of the thermoreceptors ==>
  • resetting the hypothalamic temperature "set point" to a higher level.

15

Role of the hypothalamus in generation of circadian rhythm

  • Retina ==> info about light/dark cycles ==> SCN
    • SCN generates endogenous rhythms even w/out exogenous information
  •  

16

Role of hypothalamus in emotional and motivated responses

  • responsible for initiating the coordinated autonomic and behavioral responses that contitute emotional expression
  • Integrated hypothalamic components:
    • Somatic reactions -- escape, fighting, biting, hissing, facial expressions
    • Autonomic reactions -- blushing, dryness of mouth, sweating, GI reactions, fainting
    • Endocrine reactions -- activation of adrenal cortex and medulla

17

Hypothalmic lesions ==> behavioral changes

  • Rage or aggressive behavior elicited by:       
    • Lesions of medial hypothalamus (ventromedial nucleus)
    • Stimulation of dorsomedial nucleus
  • Suppression of aggressive behavior or placid behavior:
    • Lesions of lateral hypothalamic area and mammillary region

 

18

Characteristics of "sham rage"

  • phenomena of inapropriate aggression/viciousness
  • occurs when hypothalamus is disconnected from higher cortical connections
  • ==> responses to pain or irritation are short lived and poorly directed (e.g. animal bites itself instead of attacking irritant) OR
  • ==> response occurs to inappropriate stimuli (e.g. soft touch)

19

Location of major nuclei of hypothalamus: suprachiasmatic, paraventricular nucleus, supraoptic nucleus

  • suprachiasmatic = just superior to optic chiasm (more anterior vs. paraventricular/supraoptic)
  • supraoptic = superior to optic chiasm, lateral w/in hypothalamus, posterior to suprachiasm
  • paraventricular = superior to optic chiasm, medial w/in hypothalamus, posterior to suprachiasm

20

Location of hypothalamic nuclei: posterior nucleus, mamillary body

  • mamillary body/posterior nucleus mark the posterior aspect of hypothalamus