Hypothalamus Flashcards
(20 cards)
Where is the hypothalamus located? What structure is it continuous with?
Inferior to the hypothalamic sulcus, superior to the pituitary gland, and caudal to the lamina terminalis.
It is continuous with the pituitary gland by way of the infundibulum and the hypophysial stalk.
What is the composition of the hypothalamus?
Consists of aggregations of neuron cell bodies and their axons.
What is the organization of the hypothalamus?
Rostral area is called the preoptic area
There are 3 zones caudal to the preoptic area running from medial to lateral. They are:
1) Periventricular - located right along the ventricle
2) Medial Zones
3) Lateral Zones
Nuclei within these zones have many funcitons
What fibers interconnect the hypothalamus with rostral/caudal regions?
1) Medial forebrain bundle - traverses the lateral zone
2) Dorsal Longitudinal Fasciculus - Traverses the periventricular zone
Hypothalamic Connections
What is the general rule for connections with the hypothalamus?
Projections tend to be reciprocal - if it gets input form somewhere, it usually sends projections there as well.
Hypothalamic Connections
Where does the hypothalamus get input from?
Hippocampus (memory)
Septal Nuclei (info from frontal cortex)
Amygdala (emotion)
Brainstem - nucleus of the solitary tract and reticular formation
Prefrontal Cortex
Thalamus
Retina (circadian rhythms/light dark cycles; can still be functioning in blind people despite loss of vision)
Hypothalamic Connections
Where does the hypothalamus project to?
Same areas it gets input from plus:
Spinal Cord
Intrinsic connections with the pituitary gland
What are the divisions of the pituitary gland?
Anterior pituitary = adenohypophysis
(releases hormones into the bloodstream)
Posterior Pituitary = neurohypophysis
(secretes hormones that influence adenohypophysis)
What is the function of the pituitary gland?
It coordinates the endocrine system. Problems with the pituitary gland can influence almost any system of the body. these problems can be diffuse or localized. The effect is difficult to predict.
It is controlled by the hypothalamus.
What is the function of the hypothalamus?
To integrate autonomic response and endocrine function with behavior, especially behavior concerned with the basic homeostatic requirements of everyday life.
What are the 6 Basic Physiologic Processes under Hypothalamic Control?
1) BP and Electrolyte Composition
Hypothalamus can adjust CO, change vasomotor tone, blood osmolarity, and renal clearance (what the kidney gets rid of and what it keeps). Can motivate drinking or salt consumption to change electrolyte level.
2) Body Temp
Activates mechanisms for heat dissipation, conservation, and production.
3) Energy Metabolism
Regulates feeding behavior, digestive functions, and metabolic rate.
4) Reproduction
Influences gender identity, sexual orientation, and mating behavior. In females it governs menstrual cycles, pregnancy, and lactation.
5) Emergency response to stress
Governs the release of stress hormones, modulates the balance between sympathetic and parasympathetic tone, and influences the regional distribution of blood flow
6) Sleep-wake Cycle
What are the three physiological mechanisms underlying the function of the hypothalamus?
1) Hypothalamus receives sensory (visceral, visual, olfactory) and contextual info from higher up.
2) It compares this sensory info to biological set points (normal range) .
3) It can then activate relevant autonomic, endocrine, and behavioral responses to restore homeostasis. (It is a reflex)
What are two functional divisions of the hypothalamus?
Caudolateral
Rostromedial
Where is the caudolateral division of the hypothalamus located?
Consists of the lateral zone and the posterior region.
What is the function of the caudolateral division of the hypothalamus?
Produces behavioral manifestations generally associated with anxiety including:
Increased sympathetic tone
Aggressive behavior
Hunger
Increased body temp
Where is the rostromedial division of the hypothalamus located?
Consists of anterior and tuberal regions
What is the function of the rostromedial division of the hypothalamus?
Produces behavioral manifestations generally associated with contentment including:
Increased parasympathetic tone
Passive behavior
Satiety
Decreased body temp
Hypothalamic reflexes: Temperature Regulation
Purpose: Maintain constant body temp
Info about external temp is provided by thermoreceptors in the skin an info about internal temp is provided by thermoreceptors in the hypothalamus
Example: When blood temp is low, thermoreceptors stimulate regions in the hypothalamus that activate mechanisms for heat production (shivering) and heat conservation (vasocontriction)
Hypothalamic reflexes: Water Balance
Purpose: Maintain volume and osmolarity of blood
Info about osmolarity is monitored by osmolarity sensitive neurons in the hypothalamus
Example: when osmolarity is high, osmolarity sensitive neurons in the hypothalamus activate ADH producing neurons in the hypothalamus to release more ADH, which increases renal water absorption.
What might result from a lesion in the hypothalamus?
Specific autonomic, endocrine, and/or memory deficits (depends on the location of the lesion). same goes for the pituitary gland.
