23A16: Exam Report
Outline the role of the hypothalamus.
29% of candidates passed this question.
This question required candidates to integrate parts of the syllabus that are often not presented together in the reference texts.
Many candidates provided only an incomplete list of the roles of the hypothalamus as their answer which did not score enough marks to pass. Additionally, presenting information succinctly and in a format that demonstrated an understanding of priority of function with respect to the CICM syllabus, was critical for time management and ensuring that more the important/major roles were presented in more detail.
This question required candidates to cover roles including autonomic control, thermoregulation, hormonal regulation, body rhythms and regulation of drives with feedback control mechanisms where appropriate.
Those who scored well demonstrated a comprehensive breadth of knowledge of these areas as well as giving the pertinent points around areas of positive and negative feedback and the sensor areas and effector responses required to answer an outline question.
18A20: Exam Report
Outline the structure (20% of marks) and function (80% of marks) of the hypothalamus.
21% of candidates passed this question.
Most candidates understood the endocrine functions of the hypothalamus, and to some degree its interactions with the pituitary. Fewer candidates mentioned the importance of the hypothalamus as an integrator for the autonomic nervous system, or its roles in arousal/emotions.
Many candidates had only a vague idea of the structure of the hypothalamus, while the best candidates were able to relate function to structure quite accurately.
U1iv / 23A16 / 18A20: Outline the structure (20 marks) & function (80 marks) of the hypothalamus
Definition
The hypothalamus is a functionally diverse region of the forebrain
Structure
- Very small, almond shaped, 4g
- Lies below thalamus & above pituitary gland
- One of the 4 major components of the Diencephalon
- Thalamus
- Hypothalamus
- Subthalamus
- Epithalamus
- Organised ANT → POST & MEDIAL → LATERAL
Anterior –> Posterior
- Preoptic region: medial & lateral preoptic nuclei
- Supraoptic region
- Suprachiasmatic nuclei
- Paraventricular nuclei
- Anterior hypothalamic nucleus
- Supraoptic nucleus
- Tuberal region
- Mammillary region: posterior hypothalamic nucleus & mamillary body
Function
Hypothalamus is centre for neural & endocrine control of internal organs
1) Direct Control of ANS
- Parasympathetic effects → anterior region
- Sympathetic effects → posterior region
- Controls vasomotor centre
- VC response to cold
- CV centre in PONTINE & MEDULLARY RETICULAR FORMATION
- Thermoregulation → preoptic region
- Controls body temp
- Senses ∆ temp of blood to regulate thermostat
2) Hormonal Control Of Pituitary System
- Direct connection → sends hormones to PPG for storage & release; ADH & Oxytocin
- Indirect → sends hormones to the APG to regulate the production & release of LH, FSH, ACTH, TSH
- OSMORECEPTORS in Supraoptic Nucleus → control ADH release
- Paraventricular Nucleus → releases Oxytocin to Mammary gland
3) Communicates with Limbic System & Midbrain
- Circadian rhythms
- Mamillary body regulates wakefulness & arousal
- Stimulation of anterior hypothalamus can induce sleep
- Normal circadian rhythm reset by retinal input (normally 24hrs)
- Hunger & satiety
- Ventromedial nuclei inhibit appetite by sensing BGL
- Lateral hypothalamus → seeks food
- Thirst
- Lateral hypothalamus → seeks food + H2O
- Emotions
- Fear, rage, aversion, pleasure, reward
III. Pathways and Nuclei
Function
Autonomic Nervous System
Pathway
Dorsal Longitudinal fasciculus
Afferents
Nucleus of tractus solitarius→parabrachial nucleus (taste, pain, general visceral sensation)
Nuclei
Periventricular Posterior
Efferents
Midbrain central gray
Ventral tegmental area (DA)
Medulla, autonomic centers
Braintem
Sympathetic and paras of spinal cord=hypothalamo-spinal tract
Function
Pertuitary Endocrine Function
Pathway
Tuberoinfundibular tract
Afferents
Receptors responsive to physiological state – feedback
Nuclei
Praventricular Supraoptic (magnocellular)
Arcuate (Parvocellular)
Efferents
Supraoptico-hypophyseal tract → post, pituitrary capillaries (rel ADH, OXT)
Tuberoinfundibular tract → Median eminence → hypophys portal vein (release / rel-inhib factors to anterior pituatary)
Function
Circadian Rhythms
Pathway
Retinohypothalamic fibers
Afferents
Retinal ganglion cells (melanopsin-respons to light → Optic tract fibers
Nuclei
Suprachiasmatic
Efferents
Endogenous oscillator in SCN → normal circadian rhythms, reset by retinal input (normal 24.5 hrs)
Function
Species-preserving behaviors
*hypothal motivates, limbic system selects among them
Pathway
Medical forebrain bundle (MFB)
Mammilliary peduncle (MP)
Afferents
LMA incl VTA (info on species-preserving behaviors, rewarding properties of behav)
Periaqueductal gray of LMA (info abt pain, aversive stimuli)
Nuclei
LHA
Ventromedial
Mammillary bodies
Efferents
Basal forebrain area, picks up fibers from LHA → limbic midbrain areas
Midbrain reticular formation
Function
Connections with higher cortex – limbic systen and prefrontal cortex
Pathway
- Fornix
- ventral amygdalofug
- Stria terminalis
- diffuse fibers
- mammilithal tract
- MFB
Afferents
Hippocampus
Amygdala → basal forebrain
Amygdala
Basal forebrain
Nuclei
MMB and LHA
LHA
Periventricular
Periventricular
Mammillary bodies
Entire hypothal
Efferents
Significance of events
Amygdala – signif of visc-sens
Amygdala
MD, intralam nuc (thal) → ant cing cx, prefrontal
Ant thal nuc → entire cing cx
Telencephalic, midbrain limbic