week 8 - hypothalamus Flashcards
Name the four lobes of the brain
frontal
parietal
occipital
temporal
Where is the hypothalamus located in relation to the thalamus?
ventral and anterior
What is the hypothalamus
paired small nucleus - weight 4g in relation to brain w 1.4 kg
What are nuclei?
cluster of neurons in CNS, neurons in one nucleus usually have roughly similar connections and functions
Name the boundaries of the hypothalamus
superior: hypothalamic sulcus separating it form the thalamus
inferior: optic chasm, tuber cinereum, mammillary bodies
anterior: lamina terminals
posterior: tegmenjtum of midbrain
medial: third ventricle
lateral: internal capsule
define the hypothalamus?
primary regulator of autonomic and endocrine functions
produces hormones that regulate different behaviours
give an example of an endocrine control of the hypothalamus
oxytocin release controls feeding behaviours
give an example of an autonomic control of the hypothalamus
thermoregulation
What are the functions of the hypothalamus
- stress reaction via hypothalamic-pituitary-adrenal axis
- fighting, fleeing, feeding, mating
Give examples of homeostatic processes controlled by the hypothalamus
- respiration
- circulation
- food-water intake
- digestion
- metabolism
- body temp
Why is a functional hypothalamus important?
harmonious growth of the body, differentiation of sexual characteristics, sexual and reproductive activities
Name the three regional subdivisions of the hypothalamus visible int he sagittal plane
anterior (subraoptic), middle (tuberal), posterior (mammillary)
name the three regional subdivisions of the hypothalamus in the coronal plane
lateral, medial, periventricular
name the location and function of the suprachiasmatic nuclei
medial, anterior
biological rhythms such as sleep
name the location and function of the ventromedial nuclei
medial, tuberal
appetite, body weight insulin regulation
name the location and function of the lateral nuclei
lateral, tuberal
appetite and body weight control
define the term afferent
conduct inwards or towards something eg. nerves, CNS, blood vessels, organ
define the term efferent
conduct outwards, away from something eg. nerves, CNS, blood vessels, organ
-> efferent neurons carry impulse outwards to effector organs
Describe the afferent connections of the hypothalamus
formic - fibre track going from hippocampus to hypothalamus
stria terminalis - fibre track from amygdala
olfactory bulb
retina
spinal cord
name the four types of afferent connection
- somatic and visceral
- visual
- Olfaction
- auditory
- corticohypothalamic fibres
- hippocampo-hypothalamic fibres
- amygdala-hypothalamic fibres
- thalami-hypothalamic fibres
- tegmental fibres
describe the route of somatic and visceral afferents
- general somatic, gustatory and visceral sensations reach the hypothalamus through collateral branches of the lemniascal afferent fibres and the tracts solitaries and through the reticular formation
describe the route of visual afferents
leave optic chaise and pass to the suprachiasmatic nucleus
describe the route of olfactory afferents
travel through the medial forebrain bundle
describe the route of the auditory afferents
have not been identified, but since auditory stimuli can influence activities of hypothalamus, they must exist
describe the route of the corticohypothalamic fibres
arise form the frontal lobe of the cerebral Cortex and pass directly to the hypothalamus
describe the route of the hippocampo-hypothalamic fibres
pass form hippocampus through fornix to the mammilary body
describe the route of the amygdala-hypothalamic fibres
pass through amygdaloid complex to hypothalamus through stria terminals by a route that passes inferior to lentiform nucleus
describe the route of the thalami hypothalamic fibres
arise form dorsomedial and midline thalamic nuclei
Where do tefmental fibres arise from?
midbrain
What connections has the forinx?
afferent and efferent connections between the hippocampus and hypothalamus
what connections has the stria terminalis?
afferent and efferent connections between amygdala and hypothalamus
Describe the efferent connections of the hypothalamus
- descending fibres to brainstem and spinal cord
- mammilothalmic tract
- mammillotegmental tract
- multiple pathways to limbic system
describe the course of the descending fibres to the brainstem and spinal cord
- descending fibres to brainstem and spinal cord influence the peripheral neurons of ANS
- descend through series of enurons in reticular formation
- connected to parasympathetic nuclei of CN3, CN7, CN9, CN10
- reticulospinal fibres connect hypothalamus with sympathetic cells of origin in lateral grey horns of first thoracic segment to second lumbar segment of spinal cord and sacral parasympathetic outflow at level of second, third, fourth sacral segments of spinal cord
describe the course of the mammillothalimc tract
arises in maxillary body, terminates in anterior nucleus of thalamus, pathway relayed to cingulate gyrus
describe the course of the mammillotegmental tract
arises form mammilary body and terminates in cells of reticular formation in tegmenjtum of the midbrain
Explain afferent and efferent connections of the mammillary nucleus
- hypothalamus = output of limbic system
- mammilary body receiving nucleus form hippocampus via fornix
- mammillary body is an efferent connection to thalamus, from thalamus there is an efferent connection to cingulate cortex
- lots o limbic system integration occurs in cingulate cortex
what is the function of the hypothalamus in terms of lesions?
temperature regulation
food intake
sleep-wake cycle
emotions
water balance
What does an anterior lesion of the hypothalamus lead to?
hyperthermia
insomnia
diabetes insipidus
what does a posterior lesion of the hypothalamus lead to?
hypothermia
hypersomnia
what does a ventromedial nucleus lesion of the hypothalamus lead to?
excessive eating - hyperphagia
emotions - rage
What does the lateral lesion of the hypothalamus lead to?
reducing eating - hypophagia
describe the circadian regulation if melatonin production
- suprachiasmatic nucleus = pacemaker involving intermediolateral nuclei in spinal cord, superior cervical ganglion and input form eye
- control production and release of melatonin in pineal gland
- SCN sets pace and release hormones