Hypothalamus and autonomic control

What’s the relationship between the hypothalamus and the pituitary gland?

hypothalamus will make the hormones for or that stimulate the pituitary glands so control their activity + negative feedback

What are the different divisions of the ANS?

PSNS + SNS

How were key regions involved in autonomic control identified experimentally?

control of sympathetic preganglionic neurons were found by electrical excitation in different parts of the medulla of a cat (ventrolateral medulla)

How many major nuclei make up the hypothalamus?

11

Define a nuclei?

group of neuronal cell bodies working together towards a same function

What are 3 roles of the hypothalamus?

• motivated behaviour

• links body to mind via ANS and pituitary

• regulates homeostasis

Which structures of the hypothalamus link body to mind?

medial, periventricular and pituitary

Where are the periventricular, medial and lateral parts of the hypothalamus found in relation to the third ventricle?

third ventricle then periventricular then medial finally lateral

Which structure in the hypothalamus is involved in motivated behaviour?

lateral part

Once a vital parameter has been disrupted, what mechanisms follow to indicate this change then to resolve it, by the hypothalamus?

sensory inputs integrated in the hypothalamus where it can use:

• ANS

• neuroendocrine system

• behavioural changes

to restore vital parameters

What are contextual inputs that could affect the action of the hypothalamus in regulating homeostasis?

social eg like needing to go to the toilet modified by prefrontal or cerebral cortexes stop body from going to toilet

When hot, what is an example of ANS or behavioural action that could be coded by the hypothalamus to come back to the correct body temp.?

ANS = increase blood flow to release heat

behavioural = take coat off

What are 2 important nuclei of the hypothalamus called ?

paraventricular nucleus and supraoptic nucleus

How does the adenohypophysis release hormones into circulation? Which cells release these hormones and stimulates that release?

into portal vein (2 capillary networks directly connected)

troph cells, from parvocellular neurons

How does the neurohypophysis release hormones into circulation? Which cells release these hormones?

directly into system circulation

magnocellular neurons

Which pituitary gland secretes tropic hormones ? Name a couple

anterior, flat peg (FSH, LH, ACTH, TSH)

Which pituitary secretes hormones linked to lactation and growth? Name them

anterior, flat peg (PRL, endorphins, Growth Hormone )

Which pituitary secretes hormones linked to body fluid balance and parturition (+ lactation)?

posterior, ADH and Oxytocin

What are effectors of the ANS?

smooth + cardiac muscle and glands + brown adipose tissue

To what degree can the ANS function without the hypothalamus?

sensory and motor divisions still work fine, brainstem nuclei can still maintain cardiac, vasomotor and respiratory functions without the hypothalamus

What would require more input from the hypothalamus:

pupillary dilation; salivation; regulation of body temp.?

greatest cortical input ie the body temp., the other two are more reflexes - hypothalamus would be involved in salivation when thinking of food

What are examples of preganglionic neurons in the ANS?

brainstem and spinal cord

What are examples of postganglionic neurons in the ANS?

sympathetic and parasympathetic ganglia

What are examples of effector cells in the ANS?

smooth muscle cell, gland cell, brown adipocytes

Where do para.sympathetic ganglia develop from?

neural crest

Where do the brainstem and the spinal cord develop from? What type of NT do they release and therefore what are they termed?

neural tube

ACh so cholinergic paraganglionic neurons

What are the most prevalent receptors within the ANS?

Nicotinic ACh receptors

Where do sympathetic preganglionic neurons sit in the nervous system? Where do they go out after passing through the other horns?

T1 to L3 so in the lateral horn (thoracic - lumbar region of it)

ventral horn

What is the sympathetic chain ganglia?

series of interconnected ganglia located bilaterally on either side of the spinal column, serving as relay stations

What controls sympathetic preganglionic neurons?

Nucleus tractus solitarii (NTS - dorsal sensory nucleus) + ventrolateral medulla (regulates nerve activity, BP, pain)

Where do parasympathetic preganglionic neurons sit?

sacral spinal cord (not in the lateral horn, more like lateral area)

What is the parasympathetic chain ganglia?

doesn’t exist

What types of receptors are expressed on sympathetic postganglionic neurons? What do these neurons produce?

AChRs

NE

What types of receptors are expressed on parasympathetic postganglionic neurons? What do these neurons produce?

AChRs

ACh

What’s the importance of the vagus nerve?

carries ~80% of total parasympathetic outflow (Vagus is Latin for wanderer) + lots of afferents

What are 2 essential structures of the cranial parasympathetic organisation? Name 3 nuclei in this organisation?

midbrain and medulla

• edinger-westphal nucleus

• dorsal motor nucleus of the vagus

• nucleus ambiguus

Which nerve carries parasympathetic info from the dorsal motor and ambiguus nuclei?

vagus nerve (CN X ie tenth cranial nerve)

Which nerve carries parasympathetic info from the edinger-westphal nucelus?

oculomotor nerve (CN III ie third cranial nerve)