Sievert: Autonomics & Hypothalamus Flashcards
Give two examples of local autonomic reflexes
- When you put a hot pad on a small area of your arm, there is LOCAL vasodilation and sweating, but no massive response in elevated body temp.
- When the bladder is stretched, it contracts reflexively
How does the sweating that occurs when you put a hot pad on your arm differ from the sweating that occurs when you wrap a blanket around your entire torso?
If you wrap something warm around your torso, your whole body may start to sweat in an effort to lower your body temperature. To generate systemic sweating to lower body temp, this involves SUPRASPINAL control – need to talk to all sympathetics along the spinal cord.
When you simply use a hot pad, the upper brain control is not necessarily needed.
Some local reflexes also incorporate (blank) as an intermediary in the reflex
brainstem nuclei
What is one prominent intermediary for many reflexes that can exert its influence by way of direct connections to preganglionic neurons or thru other brainstem reticular nuclei like cardiovascular, respiratory, or micturition centers.
nucleus solitarius
So, in a local response, visceral sensory input may project to the (blank) before reaching preganglionic neurons and causing a visceral motor response.
nucleus solitarius
The (blank) is strategically placed to receive input about the state of the body from many areas
hypothalamus
The hypothalamus contains neurons that can directly read things like what???
body temperature
levels of fatty acids and glucose
length of day
levels of circulating hormones
After the hypothalamus receives info about body temp, glucose levels, FA levels, length of day, etc, it has both direct and indirect connections to (blank) by way of neural and humoral pathways
motor neurons
What would happen if you cut the tract from the hypothalamus that has direct control over autonomics?
You will lose supraspinal control of autonomic reflex arch to viscera; autonomic control for things like bladder control and temp regulation will be lost(can lead to hypo/hyperthermia)
What are the three components in bladder control?
- spinal cord
- brainstem & hypothalamus
- cortex
An easy way to think about bladder control is to equate the sacral preganglionic para’s to (blank) and the descending input from the hypothalamus and reticular formation to (blank).
lower motor neurons; upper motor neurons
Damage to hypothalamus/reticular formation will cause (blank) bladder, while damage to sacral preganglionic parasympathetics to the bladder will result in (blank) bladder.
reflex; flaccid (like LMN syndrome)
Describe reflex bladder that occurs when you damage cortical input of bladder control.
If you take away the cortex control, you lose the ability to know when your bladder is full and when to void. So, your bladder will still contract reflexively, but you won’t have control over it.
There are 3 prominent afferents to the hypothalamus. What are they?
from hippocampus via the fornix
from brainstem via the medial forebrain bundle
from amygdala via stria terminalis
What’s this?
bidirectional path from the brainstem to the hypothalamus and cortex
medial forebrain bundle
Does the medial forebrain bundle pass through the thalamus?
No
Describe the path of the medial forebrain bundle (MFB)?
From the brainstem, this is a bidirectional pathway to the cortex. It passes thru the hypothalamus, picks some things up, drops some things off and proceeds to cortex.
The hypothalamus sends info to the cortex via three main bundles. What are they?
fornix (this is bidirectional)
MFB
mammillothalamic tract
**there are also just direct connections to brainstem & spinal cord
The hypothalamus can be divided into 3 zones from medial to lateral. What are they?
paraventricular, medial, and lateral
What separates the medial and lateral zones of the hypothalamus?
the fornix
What does the medial zone of the hypothalamus contain?
numerous well defined nuclei
What does the lateral zone of the hypothalamus contain?
the massive medial forebrain bundle coming from the brainstem reticular formation heading to the cortex
Why is it important that the medial forebrain bundle passes through the hypothalamus?
it allows the hypothalamus to influence cortical outputs
The hypothalamus can also be divided into 3 zones from rostral to caudal. What are they?
supraoptic at the optic chiasm
tuberal just behind the pituitary stalk
mammillary bodies
What are the important nuclei in the supraoptic zone of the hypothalamus?
supraoptic and paraventricular nuclei: cause the release of oxytocin and ADH from pituitary)
suprachiasmatic nucleus: plays a role in control of circadian rhythms and the light-dark cycle bc it receives projections from the optic tract
There is also an area in the supraoptic region connected w (blank) regulation
temperature
*specifically heat dissipation
What are the important nuclei in the tuberal region of the hypothalamus?
arcuate (periventricular) nucleus: main area for production of releasing factors
ventromedial nucleus: satiety center
lateral hypothalamic area: hunger center
Interactions bw the ventromedial nucleus and lateral hypothalamic area are though to regulate what? Lesion studies here have demonstrated major changes in what?
body weight and the biological set point of weight; level of aggression (if your hunger system is out of whack, you get angry and will kill for food!)
The mammillary area is the area where you can finally see the (blank)
mammillary bodies
What two nuclei are important in the mammillary zone of the hypothalamus?
- mammillary nucleus: consolidation of memory (think of Korsakoff’s caused by chronic alcohol abuse & its affects on the mammillary bodies and memory)
- posterior nucleus: temperature regulation and area for generating heat
What happens to animals w lesions in their mammillary zone?
they become hypothermic when placed in a room where the temp is not controlled
