HYPOTHALAMUS Flashcards
HYPOTHALAMUS
FUNCTION:
LOCATION
CONTAINS; NUCLEI
PURPOSE
FUNCTION: has AUTONOMIC, NEUROENDOCRINE and LIMBIC
FOUND WHERE?
Anterior inferior to the thalamus
wall and floor of the inferior portion of 3rd ventricle
0.3% of total brain
CONTAINS
- dorsal medial. nucleus
- ventral lateral nucleus
PURPOSE: Hypothalamus produces hormones that are released from the posterior pituitary + releasing factors that control the release of hormones from the anterior pit.
UNDERSTANDING THE AFFERENT CONNECTIONS OF HYPOTHALAMUS: 8
RECEIVES AFFERENTS FROM:
- SOMATIC AND VISCERAL SYSTEMS
- LIMBIC SYSTEM
- OLFACTORY SYSTEM
- CORTEX
- RETINA
- FORNIX; delivers afferents from HIPPOCAMPUS (and vice versa)
- STRIA TERMINALS delivers afferents from AMYGDALA to HYPOTHALAMUS (and vice versa)
- afferents from BRAINSTEM and SPINAL CORD delivered via MEDIAL FOREBRAIN BUNDLE or DORSAL LONGITUDINAL FASICULUS (and vice versa)
UNDERSTANDING EFFERENT CONNECTIONS of HYPOTHALAMUS
The hypothalamus sends efferents to:
- SPINAL CORD and BRAINSTEM and FOREBRAIN STRUCTURES
- MAMMILLARY BODIES to :
- HIPPOCAMPUS.
- PERIAQUEDUCTAL GREY (PAG) matter,
- ANTERIOR NUCLEI OF THALAMUS
HYPOTHALAMUS: REGULATION OF ENDOCRINE FUNCTIONS
THE CELLS THAT PRODUCE THE NEURHORMONES AND WHAT?
- MAGNOCELLULAR NEURONS OF PARAVENTRICULAR NUCLEUS = produces oxytocin
- MAGNOCELLULAR NEURONS OF SUPRAOPTIC NUCLEUS =
antidiurectic hormone ; ADH; VASOPRESSIN - PARVOCELLULAR NEURONS = releasing and inhibiting hormones transport these down their axons and secrete them into primary capillary plexus
How are OT and ADH transported and released?
- OT and ADH TRANSPORTED along AXONS of the HYPOTHALAMUS via the “HYPOTHALAMIC-HYPOPHYSEAL portal system before being RELEASED IN POSTERIOR LOBE = NEUROHYPOPHYSIS
- B.vlessels of the hypothalamic-hypophyseal portal system UPTAKE the HORMONES for TRANSPORT via the VASCULAR SYSTEM
- 1% increase in osmotic pressure or a 5-10% reduction in blood volume or blood pressure stimulates the release of ADH from the POSTERIOR PITUITARY.
UNDERSTANDING THE PITUITARY GLAND
HYPOPHYSIS
- TWO GLANDS:
ADENOHYPOPHYSIS (anterior)
NEUROHYPOPHYSIS (posterior)
ANTERIOR LOBE SYNTHESISES AND RELEASES:
1. Adrenocorticotropi (ACTH)
2. luteinising hormone (LH)
3. Follicle stimulating hormone (FSH)
4. Thyroid-stimulating hormone (TSH)
5. Growth Hormone (GH)
6. PROLACTIN
REGULATION OF THE VISCERAL FUNCTION
ANTERIOR VS POSTERIOR
NUCLEUS SOLITARIUS
HYPOTHALAMOBULBAR AND HYPOTHALAMOSPINAL
ANTERIOR HYPOTHALAMUS:
- stimulus will activate PARASYMPATHETIC SYSTEM
- the autonomic (visceral) nervous system is REGULATED BY HYPOTHALAMUS
POSTERIOR THALAMUS:
- Stimulus will activate SYMPATHETIC SYSTEM
NUCLEUS SOLITARIUS projects to HYPOTHALAMUS conveying info collected by BARORECEPTORS AND CHEMORECEPTORS received by CN IX AND X
HYPOTHALAMOBULBAR AND HYPOTHALAMOSPINAL TRACTS WILL SYNAPSE ONTO THE PRE-GANGLIONIC AUTONOMIC FIBRES TO MODULATE THIER ACTIVITY.
REGULATION OF BODY TEMPERATURE
DECREASE/INCREASE BODY TEMP
INCREASED BODY TEMP
- ACTIVATES ANTERIOR HYPOTHALAMUS
initiate heat-loss mechanisms to cool the body
1. BEHAVIOURAL CHANGES
2. VASODIALATION
3. SWEATING
4. DECREASED METABOLIC RATE
DECREASE IN BODY TEMP
-ACTIVATES POSTERIOR HYPOTHALAMUS to initiate heat-gain mechanisms to warm up the body
1. BEHAVIOURAL CHANGES
2. VASOCONSTRICTION
3. SHIVERING
4. INCREASED METABOLIC RATE
REGULATION OF FOOD AND WATER INTAKE BY THE HYPOTHALAMUS
WHERE AND HOW? = 3
Coordinated by LATERAL VS VENTROMEDIAL AREA of HYPOTHALAMUS
- LATERAL HYPOTHALAMUS = HUNGER (stimulating increased feeding)
- VENTROMEDIAL = SAFETY (stimulation inhibits feeding)
- THIRST CENTRE = influences release of ADH from SUPRATROPIC AND PARAVENTRICULAR NUCLEI
Regulation of CIRCADIAN RHYTHMS
WHAT, MELATONIN AND WHAT IS IT?
- “Master clock” = SUPRACHIASMATIC NUCLEUS (SCN)
- 24HR RHYTHM OF ELECTRICAL ACTIVITY - LIGHT (via RETINOHYPOTHALAMIC TRACT) AND MELATONIN; SECREATED BY PINEAL GLAND
- REGULATES SCN - Melatonin signals a clock “ time of day” and calendar “time of year - FUNCTION TO ALL TISSUES OF THE BDY
SCN PATHWAY - explain it
LIGHT -> EYE –> PACEMAKERS –>
- HYPOTHALAMIC NUCLEI (SCN)
PITUITARY GLAND: glands, viscera, GI tract, immune system, pineal, vasculature
AUTONOMIC NERVOUS SYSTEM: glands, viscera, GI tract, immune system, pineal, vasculature
BRAIN OSCILLATORS: Behaviour
REGULATION OF SLEEP-WAKE CYCLE: HYPOTHALAMUS
- Preoptic area (ANTERIOR HYPOTHALAMUS)
-> important for the generation of SLOW WAVE SLEEP (deep, non-REM) - Lesions of pre-optic area = INSOMINA
- POSTERIOR HYPOTHALAMUS = important in wakefulness
- LESIONS IN THERE WILL CAUSE DROWSINES ==> COMA
BLOOD SUPPLY OF HYPOTHALAMUS: EXPLAIN
ANTERIOR HYPOTHALAMUS:
- ANTERIOR CEREBRAL
- ANTERIOR COMMUNICATING
POSTERIOR HYPOTHALAMUS
- POSTERIOR CEREBRAL
- POSTERIOR COMMUNICATING
UNDERSTAND THE MESOCORTICOLIMBIC REWARD SYSTEM
LOOK AT DIAGRAM
