Hypothalamus and Limbic System MCQs

Suprachiasmatic nucleus (SCN) Concerned with circadian rhythms the normal 24 hour rhythms of humans It is the "dominant pacemaker" that regulates circadian rhythm Bilateral destruction of the SCN results in a loss of most endogenous circadian rhythms including wake-sleep behavior Reference: Ganong 25th ed p.307

Ans. B i.e. Posterior hypothalamus Shivering/Shuddering It is a bodily function in response to early hypothermia in warm- blooded animals. When the core body temperature drops, the shivering reflex is triggered to maintain homeostasis. Muscle groups around the vital organs begin to shake in small movements in an attempt to create warmth by expending energy. Shivering can also be a response to a fever, as a person may feel cold, though their core temperature is already elevated. Located in the posterior hypothalamus near the wall of the third ventricle is an area called the primary motor center for shivering. This area is normally inhibited by signals from the heat center in the anterior hypothalamic-preoptic area but is excited by cold signals from the skin and spinal cord.

Ans. C. Hyperthermia Preoptic nucleus is concerned with regulation of body temperature. Therefore, its lesion will result in defectivetemperature

Anterior Hypothalamus Activated by hot temperature Activation causes cutaneous vasodilation, sweating and increase in thirst sensation (osmoreceptors are present in anterior hypothalamus) Reference: Ganong, 25th edition page no.307

Thermosensitive neurons are located in preoptic area of hypothalamus Reference: Ganong, 25th edition page no.311

Medial preoptic nucleus Produces gonadotropin-releasing hormone (GnRH) Sexually dimorphic- size larger in males when compared to females Reference: Ganong 25 th Edition page no.310

Suprachiasmatic nucleus is Concerned with circadian rhythms - the normal 24 hour rhythms of hum ans Reference: Ganong, 25th edition page no.309

Unconditioned Response (UR) is food eliciting reflex salivation Unconditioned responses are innate (they are produced without learning) Conditioning ( associative learning) Amygdala( window of limbic cortex) and Cerebellum are involved in this type of learning Two types: 1. Classical : Dog + Food = Salivate( innate reflex) Dog + Food + Ring bell = Salivate (innate reflex) Dog + Ring bell = Salivate( Classical conditioning by Pavlov) 2. Operant : Punishment based learning Reference: Ganong, 25th edition page no.283