Exam 3: Hypothalamus and Autonomic system Flashcards
hypothalamus
functions to regulate homeostasis ⇒ talks to cerebral cortex and limbic areas as reciprocal connections between these parts of the brain
- keeping us alive as well as continuation of life
things the hypothalamus influences (7)
- Maintaining appropriate body temperature
- Eating
- Drinking
- Blood circulation
- Breathing
- Excreting substances that we don’t want inside us
- Development and growth ⇒ reproduction (long term continuation of life)
what does the hypothalamus interface?
brain, endocrine system, and autonomic nervous system
medial hypothalamus (define + 4)
links with the endocrine system
- Blood volume
- Metabolic rate
- Lactation
- Stress response
hypothalamus interface between the autonomic nervous system and the limbic system
- heart rate, blood pressure, respiration, feeding, thermoregulation
- output to limbic system ⇒ altered motivation
how much does the pituitary weigh?
4 grams (located diencephalon)
which half of the pituitary gland is part of the hypothalamus?
Posterior is part of hypothalamus but anterior is not
Hypothalamic sulcus
divides the thalamus and hypothalamus
lamina terminalis
directly under the anterior commissure and prevents CSF from draining
anterior commissure
connects olfactory and the limbic system
endocrine organs
release chemicals (hormone) into the blood that act at other parts of the body
hypothalamus endocrine functions (2)
- Directly releases hormones into general circulation
- Release chemicals into the blood that act on the pituitary gland ⇒ acts on other endocrine organs
what hormones does the Hypothalamus directly release into general circulation?
from posterior pituitary
- Oxytocin
- Vasopressin
oxytocin
is made in neurons in supraoptic nerve and paraventricular nerve
- their axons directly project to posterior pituitary
- These end on blood vessels to release contents into the bloodstream
where is the paraventricular nerve?
next to 3rd ventricle
where is the supraoptic nerve?
right on top of the optic chiasm and optic tracts
effects of oxytocin?
acts as a tribal hormone
- Uterine contraction during birth
- Milk ejection reflex
- Increases trust, decreases fear, increases generosity
- Promotes monogamous behavior in males
- Also appear to promote racist, xenophobic behavior
Vasopressin
increase blood volume by decreasing excretion of water
- Decreases urine production by increasing reabsorption of water into bloodstream
- cells sense osmolarity (concentration of salt in blood)
- Increased salt ⇒ increased firing of paraventricular and supraoptic nerves
As sodium concentration goes up the secretion of antidiuretic
goes up ⇒ direct relationship
endocrine gland
organ that releases chemicals directly into the blood that have an effect on cells in other organs
- Sometimes directly control secretion of different hormones by other endocrine glands
where are hypothalamic hormones made?
in arcuate nerve (right under hypothalamus) and paraventricular nerve
- ventromedial hypothalamus
where do hypothalamic hormones get released?
into hypothalamic-hypophyseal portal blood vessels
what is the route of hormonal release from the hypothalamus?
hormones from arcuate and paraventricular nerves => hypothalamic-hypophyseal portal blood vessels => capillaries => anterior pituitary => general circulation
portal circulation
supplies two organs, and can carry a hormone from one organ to the other
- we don’t know how there is enough oxygen to survive the second capillary system with its corresponding organs
normal circulation supplies what?
one organ only
Thyrotropin releasing hormone (TRH)
released from hypothalamus into portal circulation ⇒ anterior pituitary
components of TRH (3)
- Causes release of thyroid stimulating hormone from anterior pituitary
- Thyroid stimulating hormone ⇒ general circulation to thyroid
- Causes release of thyroid hormone ⇒ sets basal metabolic rate
hormones in the anterior pituitary have their release controlled by what?
hypothalamic factors released into the portal circulation
Corticotropin releasing hormone
causes release of adrenal corticotropic hormone (ACT) by pituitary
- ACTH causes release of cortisol by adrenal gland
when does cortisol get released?
during stress
- Limbic system cause the hypothalamus to release corticotropin releasing hormone into the portal circulation to the anterior pituitary for release of adrenocorticotropic hormone in the adrenal cortex causing cortisol release
Gonadotropin releasing hormone (GNRH)
causes release of follicle stimulating hormone (FSH) and luteinizing hormone (LH) by pituitary
what do FSH and LH do?
cause maturation of gametes (egg and sperm), ovulation, etc. (sex hormones)
somatostatin
released by the hypothalamus and inhibits the release of growth hormone from pituitary
how does feedback control of hormone synthesis work?
a hormone may directly inhibit the synthesis or release of its hypothalami releasing hormone
- This is important for when hormone levels are too high
thyroid hormones decreases what in a feedback system?
Thyrotropin releasing hormone (TRH)
cortisol decreases what in a feedback system?
Adrenocorticotropic hormone (ACTH)
hypothalamic hormones (4)
- Corticotropin releasing hormone (CRH)
- Thyrotropin releasing hormone (TRH)
- Gonadotropin releasing hormone (GNRH)
- somatostatin
→ mostly have releasing in their names
pituitary hormones (3)
- Adrenocorticotropic hormone (ACTH)
- Thyroid stimulating hormone (TSH)
- Luteinizing hormone (LH)
what nerve increases blood pressure and heart rate in response to stress?
dorsomedial nerve of hypothalamus
- Same thing as sympathetic activation due to wiring
what area of the hypothalamus responds to temperature for thermoregulation?
preoptic nucleus (20% of preoptic neurons activated by warmth)
- receive input from skin and blood temperature
- Firing reduces body temperatures
when pre optic nucleus firing reduces body temperature what is affected? (3)
- Activates vasodilation
- Inhibits vasoconstriction
- Ultimately activates sweating
what does exposure to cold do?
activates sympathetic output to skin ⇒ vasoconstriction
- less heat loss
how does the hypothalamus influence descending motor systems?
it excites Central pattern generators ⇒ shivering ⇒ heat
what does hypothalamic input to the limbic system influence?
behavior ⇒ acts on our consciousness not just autonomic
stimulation of lateral hypothalamus does what?
increases eating
lesions to the lateral hypothalamus does what?
aphagia (lack of eating)
stimulation of the medial hypothalamus lead to what?
decreased eating
lesions to the medial hypothalamus leads to what?
hyperphagia (excessive eating)
leptin
released by body fat and measures our stored energy sources
- Decreased appetite
ghrelin
cause you to want to eat
Arcuate nucleus
receptors for leptin, ghrelin, and orexin
orexin
promotes food intake but may be effect of general arousal
- output of hypothalamus to limbic system alters conscious motivation to find food
- More motivated if stomach is empty
- Less motivated if over prices
what does circadian rhythm influence?
- Eating
- Sleeping
- Defecating
- Periods of “physical “activity”
suprachiasmatic nucleus (SCN)
above the optic chiasm and serves as the master clock for our circadian pattern generation
what does light set our circadian clock to? Where does it get input from?
24 hours; Input directly from retinal ganglion cells via retina suprachiasmatic pathway
what does the suprachiasmatic nucleus express?
melatonin receptors
- Melatonin is secreted by pineal gland
- Secretion increases at night
autonomic nervous system
independent of outside control ⇒ doesn’t require conscious control
- Parasympathetic nervous system
- Sympathetic nervous system
- Enteric nervous system
preganglionic neurons
CNS neurons that synapse in ganglia (collections of cells) outside of the CNS (always in the CNS and synapse outside the CNS and PNS)
sympathetic preganglionic neurons
in thoracic ⇒ mostly spinal cord
Parasympathetic preganglionic neurons
preganglionics in brain stem plus in sacral spinal cord
ganglia
project their post ganglionic axons to targets that are not skeletal muscle ⇒ long ways away from the SNS and close for PSN
places that ganglia project to (3)
- Glands
- Smooth muscle
- Cardiac muscle
where do CNS preganglia originate from?
Originating from neural tube
- cell somata within the skull or vertebrae
where do PNS post-ganglia originate from?
Originating from neural crest or placodes
- cell somata outside the skull or vertebrae
Enteric nervous system
intrinsic to the gut ⇒ gut secretions and motility
placodes
special tissues that induces changes to grow out toward it ⇒ tissue can develop into certain structures like eye lens and bones of ear
common organization of sympathetic and parasympathetic nervous system?
ACh cholingergic prę-ganglionic neuron synapses (CNS) on ganglionic neuron nicotinic receptor (PNS) which synapses on target tissue
nicotinic cholinergic receptor
mediates synapse in the peripheral NS on a ganglionic neuron ⇒ ion channel receptor
what neurotransmitter is expressed with parasympathetic system vs sympathetic?
parasympathetic is acetylcholine and sympathetic is usually norepinephrine (1 exception)
parasmpathetic nervous system organization
- cholinergic preganglionic neuron in brainstem or intermediate gray matter sacral spinal cord sends a signal to the neuron in the targets ganglion
- the ganglionic neuron contains acetylcholine again and is a nicotinic ACh receptor
- Target tissue expressing muscarinic cholinergic receptor near the the neurons
what type of receptor are muscarinic?
G-protein coupled receptor so they act more slowly
- different than responding to acetylcholine
what are the parasympathetic cranial nerves (preganglionic neurons) (5)
- CN 3: oculomotor
- CN 7: Facial
- CN 9: Glossopharyngeal
- CN 10: vagus
- Sacral parasympathetic nucleus
Sacral parasympathetic nucleus
targets are in or near the pelvis
- Rectum, bladder, sex organs
what does CN 3 target in the parasympathetic system?
Edinger-Westphal nucleus in oculomotor nuclear complex
what does CN 7 target in the parasympathetic system?
superior salivatory nucleus in lower pons
what does CN 9 target in the parasympathetic system?
inferior salivatory nucleus in upper medulla
where do preganglionic neurons in oculomotor complex (Edinger Westphal nucleus [EWN]) project to?
ciliary ganglion in the eye
where are the preganglionic cell bodies for the oculomotor neuron?
Ventral to the aqueduct there is the oculomotor nucleus and there are 2 light areas in the middle that are myelinated and the EWN
CN 3 pathway for parasympathetic ganglia?
Ciliary ganglion (behind eye) ⇒ pupillary constrictor muscle and ciliary muscle (focuses the lens) ⇒ innervated by EWN
CN 7 pathway for parasympathetic ganglia? (2)
- Submandibular ganglion ⇒ submandibular and sublingual salivary glands
- (don’t need to know gland) ⇒ lacrimal gland of eye and mucus glands of nose and mouth
CN 9 pathway for parasympathetic ganglia?
(don’t need to know gland) ⇒ parotid salivary gland
Ciliary ganglion
behind eyeball innervating pupillary constrictor muscle and ciliary muscles focusing the lens for close vision
Submandibular ganglion
CN 7 to submandibular glands just medial to jaw
Sublingual gland
CN 7 to sublingual ganglion
Otic ganglion
CN 9 to parotid gland about 3 cm deep
Cell bodies of preganglionic neurons
in dorsal motor nucleus of vagus (DMX)
- medial to nucleus of solitary tract; lateral to hypoglossal nucleus
parasympathetic post ganglionic neurons outside the head (3)
- Heart: in regions generating heartbeat ⇒ ganglion in the heart tissue the vagus nerve end on
- Lungs: in lung tissue
- Gut: in ganglia in the abdomen and pelvis
effects of activation of PNS for CN 3?
- Iris sphincter: constricts pupil of eye
- Ciliary muscle: focuses lens of eye
effects of activation of PNS for CN 7?
- Lacrimal gland (tears): increased secretion
- Nasal mucosa (mucus): increased secretion
- Sublingual and submandibular salivary glands: increased secretion
effects of activation of PNS for CN 9?
- Parotid salivary gland: increased secretion
effects of activation of PNS for CN 10?
- Heart: slows heart rate
- Lungs: constricts bronchial tree
- Gut: increased gut motility and secretion
effects of activation of PNS for sacral parasympathetic nucleus?
- Urinary bladder: contracts ⇒ urination
- Bowel: evacuates excretion
- clitoris/penis: erection
T/F there are both inhibitory and excitatory forms for parasympathetic ACh receptor?
True
who first demonstrated the existence of neurotransmitters?
Otto Loewi who took stimulated vagus heart fluid and put it into a tub with a different heart which caused the second heart to slow like the first one
general organization of SNS
- cholinergic pre ganglionic neuron in CNS
- (chain) ganglionic neuron expressing nicotinic receptor and usually containing norepinephrine
- target tissue with alpha or beta adrenergic receptors
- usually target is distant
sympathetic chain ganglia
in PNS are second order neurons and live in bulges outside of the spinal cord
where are the cell bodies of the SNS?
preganglionic neurons are in the thoracic spinal cord in the intermediolateral nucleus in the intermediate gray area
- goes out to sympathetic chain ganglia
organization of SNS
- axons exit through the ventral root to spinal nerve
- right next to the vertebrae is the sympathetic chain where the neurons synapse with norepinephrine
- this targets blood vessels, heart, trachea, hair follicles, etc.
adrenal gland; what its stimulated by
unique part of the sympathetic nervous system
- when stimulated they release epinephrine (and norepinephrine) into the bloodstream
- Ach released from preganglionic neurons
where does the adrenal medulla core develop from?
neural crest cells
adrenal medulla is analogous to what?
chain ganglion
- innervated directly by intermediolateral nucleus of thoracic spinal cord (IML)
- bypasses the chain ganglia so there is no synapse there unlike other parts of the SNS
receptors of norepinephrine and epinephrine
- alpha
- beta
alpha receptors
- constricts many blood vessels to increase blood pressure and decrease nasal secretions
- Decreases gut motility
- Contracts pupillary dilator muscle to make the pupil bigger
beta receptors
- Increase contractility of the heart
- Dilates lung airways
what is special about sweat glands?
part of SNS but don’t use norepinephrine and instead use Ash on their cholinergic neuron chain ganglion receptor
- still expressed the muscarinic cholinergic target receptor
enteric nervous system roles
- Contractions move food along gut
- Secretions digest food
what is the enteric gut system modulated by?
both sympathetic and parasympathetic nervous systems
anatomy of the small intestine (7)
- Outer serosal layer
- Longitudinal muscle ⇒ constricts the length
- Myenteric plexus ⇒ nerve group
- Circular muscle ⇒ constricts the diameter
- Submucosal plexus ⇒ controls mucosa
- Mucosa + villi
- Lumen of the gut
submucosal plexus
control secretion of digestive fluids from the mucosal layer
myenteric plexus
gets input from the sympathetic and parasympathetic NS’s to control gut contractions
what 2 parts of the gut control digestion?
submucosal plexus and mucosa
