Sievert: Autonomics & Hypothalamus

Question 1

Give two examples of local autonomic reflexes

Answer 1

1. 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.
2. When the bladder is stretched, it contracts reflexively

Question 2

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?

Answer 2

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.

Question 3

Some local reflexes also incorporate (blank) as an intermediary in the reflex

Answer 3

brainstem nuclei

Question 4

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.

Answer 4

nucleus solitarius

Question 5

So, in a local response, visceral sensory input may project to the (blank) before reaching preganglionic neurons and causing a visceral motor response.

Answer 5

nucleus solitarius

Question 6

The (blank) is strategically placed to receive input about the state of the body from many areas

Answer 6

hypothalamus

Question 7

The hypothalamus contains neurons that can directly read things like what???

Answer 7

body temperature
levels of fatty acids and glucose
length of day
levels of circulating hormones

Question 8

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

Answer 8

motor neurons

Question 9

What would happen if you cut the tract from the hypothalamus that has direct control over autonomics?

Answer 9

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)

Question 10

What are the three components in bladder control?

Answer 10

1. spinal cord
2. brainstem & hypothalamus
3. cortex

Question 11

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).

Answer 11

lower motor neurons; upper motor neurons

Question 12

Damage to hypothalamus/reticular formation will cause (blank) bladder, while damage to sacral preganglionic parasympathetics to the bladder will result in (blank) bladder.

Answer 12

reflex; flaccid (like LMN syndrome)

Question 13

Describe reflex bladder that occurs when you damage cortical input of bladder control.

Answer 13

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.

Question 14

There are 3 prominent afferents to the hypothalamus. What are they?

Answer 14

from hippocampus via the fornix
from brainstem via the medial forebrain bundle
from amygdala via stria terminalis

Question 15

What’s this?

bidirectional path from the brainstem to the hypothalamus and cortex

Answer 15

medial forebrain bundle

Question 16

Does the medial forebrain bundle pass through the thalamus?

Answer 16

No

Question 17

Describe the path of the medial forebrain bundle (MFB)?

Answer 17

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.

Question 18

The hypothalamus sends info to the cortex via three main bundles. What are they?

Answer 18

fornix (this is bidirectional)
MFB
mammillothalamic tract
**there are also just direct connections to brainstem & spinal cord

Question 19

The hypothalamus can be divided into 3 zones from medial to lateral. What are they?

Answer 19

paraventricular, medial, and lateral

Question 20

What separates the medial and lateral zones of the hypothalamus?

Answer 20

the fornix

Question 21

What does the medial zone of the hypothalamus contain?

Answer 21

numerous well defined nuclei

Question 22

What does the lateral zone of the hypothalamus contain?

Answer 22

the massive medial forebrain bundle coming from the brainstem reticular formation heading to the cortex

Question 23

Why is it important that the medial forebrain bundle passes through the hypothalamus?

Answer 23

it allows the hypothalamus to influence cortical outputs

Question 24

The hypothalamus can also be divided into 3 zones from rostral to caudal. What are they?

Answer 24

supraoptic at the optic chiasm
tuberal just behind the pituitary stalk
mammillary bodies

Question 25

What are the important nuclei in the supraoptic zone of the hypothalamus?

Answer 25

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

Question 26

There is also an area in the supraoptic region connected w (blank) regulation

Answer 26

temperature

*specifically heat dissipation

Question 27

What are the important nuclei in the tuberal region of the hypothalamus?

Answer 27

arcuate (periventricular) nucleus: main area for production of releasing factors
ventromedial nucleus: satiety center
lateral hypothalamic area: hunger center

Question 28

Interactions bw the ventromedial nucleus and lateral hypothalamic area are though to regulate what? Lesion studies here have demonstrated major changes in what?

Answer 28

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!)

Question 29

The mammillary area is the area where you can finally see the (blank)

Answer 29

mammillary bodies

Question 30

What two nuclei are important in the mammillary zone of the hypothalamus?

Answer 30

1. mammillary nucleus: consolidation of memory (think of Korsakoff’s caused by chronic alcohol abuse & its affects on the mammillary bodies and memory)
2. posterior nucleus: temperature regulation and area for generating heat

Question 31

What happens to animals w lesions in their mammillary zone?

Answer 31

they become hypothermic when placed in a room where the temp is not controlled