VPB 121: Veterinary Physiology - II (2+1)

AMYGDALA

• It  morphologically forms the part of the basal gangalia and has bi-directional connections with hypothalamus.  Amygdala receives input signals from all the portions of the limbic cortex, the orbital surface of the frontal lobe, cingulate gyrus, hippocampal gyrus, neocortex of the temporal, parietal and occipital lobes especially from the auditory  olfactory and visual associated areas.  Hence it is referred to as window of the limbic system.  This forms the behavioural awareness area that operates at a subconscious level.  A portion of the amygdala has olfactory function.

• Amygdala in turn transmits signals back to the cortical area, hippocampus, septum, thalamus and hypothalamus. 
• Septum functions in sexual and maternal behavioural pattern.  Stimulation of amygdaloid nuclei causes a pattern of rage, escape, of being punished and reactions of reward and pleasure.
• Functions: It forms the part of the visceral control centre of the limbic system.
  • Located in the interior of the basal temporal bone.
  • Concerned to process inputs that generate fear response and to avoid danger.
  • Deals with emotional memories and prepare the animals to set the goal for fight-flight system.
  • The circuits of amygdala releases GABA, an inhibitory neurotransmitter, so as to initiate fight responses after receiving stronger stimuli.
  • Amygdala due to the presence of GABA filters unthreatening stimuli.