Lecture 17: Emotions Flashcards
Emotions
Cognitive reflexes with positive and negative valence
Parts of the NS involved in emotion
CNS - amygdala
PNS - enteric and autonomic (sympathetic and parasympathetic)
Autonomic pathways
Have three basic cell types - preganglionic neurons, postganglionic neurons, effector cells.
Autonomic motor neurons
900,000 sympathetic and parasympathetic motor neurons. Often opposing actions.
Autonomic motor neurons lie outside the CNS in clusters or ganglia and are controlled by preganglionic neurones in the SC or brainstem. Specialised neurons in ganglia regulate specific types of effector cells, such as smooth muscle, gland cells, and cardiac muscle.
How is sympathetic outflow organised?
Into groups of paravertebral and prevertebral ganglia.
Paravertebral ganglia
Axons of preganglionic cells in the spinal cord reach postganglionic neurons via the ventral roots and the paravertebral sympathetic chain. Those axons either form synapses on postganglionic neurons in the paravertebral ganglia or project out of the chain into splanchnic nerves.
Prevertebral ganglia
Preganglionic axons in the splanchnic nerves form synapses with postganglionic neurons in prevertebral ganglia and with chromatin cells in the adrenal medulla.
Acetylcholine
In sympathetic ganglia, ACh can activate both nicotinic and muscarinic receptors to produce fast and slow Post-S potentials respectively.
Norepinephrine NE
At neuromuscular junctions norepinephrine can simultaneously activate postS alpha1-adrenergic receptors to produce vasoconstriction and preS alpha2-adrenergic receptors to inhibit further transmitter release.
ACh + VIP
co-transmission involves the co-activation of more than one type of receptor by more than one transmitter; paraS postganglionic nerve terminals in the salivary glands release both Act and VIP to control secretion. Autonomic hypnoses with end-organs sometimes employ more elaborate combinations, activating three or more receptor types.
Effects of the parasympathetic division
- constrict pupils
- stimulate salivation
- constrict airways
- slows heartbeat
- stimulates digestion
- slight simulation of glucose uptake and glycogen synthesis
- inhibits gluconeogenesis
- stimulates activity of intestines
- stimulates urinary bladder to contract
- stimulates penile or clitoral arousal
Sympathetic division - effects
- dilates pupil
- inhibits salivation
- relaxes airways
- accelerates heartbeat
- stimulates sweat glands
- inhibits digestion
- stimulates breakdown of glycogen and release of glucose
- inhibits activity of intestines
- relaxes urinary bladder
- stimulates orgasm, vaginal contraction
Organisation of the preganglionic spinal outflow to sympathetic ganglia
parasympathetic brainstem nuclei
Edinger–Westphal nucleus in the midbrain (which innervates the cili- ary ganglion via the oculomotor nerve and mediates construction of the pupil in response to increased light; see Chapter 12);
the superior and inferior salivatory nuclei in the pons and medulla (which innervate the salivary glands and tear glands, mediating salivary secretion and the production of tears);
a visceral motor division of the nucleus ambiguus in the medulla;
and the dorsal motor nucleus of the vagus nerve, also in the medulla.
Central autonomic network - main afferent pathways
Visceral ingo is dsitributed to the brain from the nucleus of the solitary tract and from ascending spinal pathways activated by the splanchnic nerves (from the gut, eg). The nucleus of the solitary tract distributes this info to the preganglionic paraS neurones (the dorsal motor vagal nucleus and nucleus ambiguous), to regions of the ventrolateral medulla that coordinate autonomic and respiratory reflexes, and to more rostral parts of the central autonomic network in the pons (parabranchial nucleus), midbrain (periaqueductal grey) and forebrain. The parabrachial nucleus also projects to many of the more rostral components of the CAN, including visceral and gustatory nuclei of the thalamus…
Organisation of the enteric component of the visceral motor system
The neurons in the gut wall include local and centrally projecting sensory neurons that monitor mechanical and chemical conditions in the gut, local circuit neurons that integrate this information, and motor neurons that influ- ence the activity of the smooth muscles in the wall of the gut and glandular secretions (e.g., of digestive enzymes, mucus, stomach acid, and bile). This complex arrangement of nerve cells intrinsic to the gut is organized into (1) the myenteric (or Auerbach’s) plexus, which is specifically concerned with regulating the musculature of the gut; and (2) the submucous (or Meissner’s) plexus, which is lo- cated, as the name implies, just beneath the mucus mem- branes of the gut and is concerned with chemical monitor- ing and glandular secretion.
Afferent input from the cranial nerves relevant to visceral sensation (as well as afferent input ascending from second-order visceral afferents in the spinal cord) converges on the caudal division of the nucleus of
the solitary tract (the rostral division is a gustatory relay; see Chapter 15).
Organisation of sensory input into the visceral motor system
Afferent input from the cranial nerves relevant to visceral sensation (as well as afferent input ascending from second-order visceral afferents in the spinal cord) converges on the caudal division of the nucleus of
the solitary tract (the rostral division is a gustatory relay; see Chapter 15).
Distribution of visceral sensory information by the nucleus of the solitary tract.
Sensory information transduced via this pathway serves either local reflex responses or more complex hormonal and behavioral responses via integration within a central autonomic network. As expanded upon in Figure 21.7, forebrain centers also provide input to visceral motor effector systems in the brainstem and spinal cord.
Afferent activity arising from the vis- cera serves two important functions. First, it provides feed- back to local reflexes that modulate moment-to-moment visceral motor activity within individual organs. Second, it informs higher integrative centers of more complex pat- terns of stimulation that may signal potentially threatening conditions or require the coordination of more widespread visceral motor, somatic motor, neuroendocrine, and behav- ioral activities (Figure 21.5). The nucleus of the solitary tract in the medulla is the central structure in the brain that receives visceral sensory information and distributes it accordingly to serve both purposes.
The hypothalamic circuits
hypothalamic circuits receive sensory and contextual information, compare that information with bio- logical set points, and activate relevant visceral motor, neuroendocrine, and so- matic motor effector systems that restore homeostasis or elicit appropriate behav- ioral responses.
Nuclei of the hypothalamus
- paraventrical nucleus
- lateral and medial preoptic nuclei
- suprachiasmatic nucleus
- supraoptic nucleus
- dorsomedial nucleus
- ventromedial nucleus
- arcuate nucleus
