The limbic system

What is it?

collection of grey matter nuclei connected via white matter tracts, controlling memory and emotion.

parts involved in memory

• hippocampal formation

• anterior thalamus

• lhypothalamus: mammilary bodies.

emotional response control

• amygdyla 

• dorsimedial thalamus 

• hypothalamus: ANS nuclei

what forms the limbic lobe

cingulate gyrus, parahippocampal gyrus 

what do mammilary bodies do? 

• thalamic relay 

• episodic memory 

• appropriate behavioural reactions

what does the hippocampus do?

• who, what, where, when?

• long-term memory formation

• output to cortex via fornix (a white matter tract).

Amygdyla

• analyzes anger, and fear expressions

• assesses danger and ellicits fear responses.

• emotional memories.

• output to hypothalamus.

episodic memory (what is it and location)

• Thalamus, amygfyla, hippocampus.

• Event memory

semantic memory 

• neocortex 

• Factual memory 

procedural

cerebellum & basal nuclei 

muscle memory 

explain the papez circuit

Starts in the cingulate cortex, gathers all information, then goes to hippocampus, the mammilary bodies via fornix, then anterior thalamius, then back to cingu

emotion + behaviour

• anygdyla and hypothalamus work together to enable an automatic response to govern emotional responses.

• pituitary gland.

• ANS, feeding, sexual stuff.

what is the ANS

• Things you can’t control - heartbeat and stuff.

• meant to maintain homeostasis.

• controlled by limbic system and its connections to the hypothalamus.

explain the difference between somatic and autonomic systems.

• Somatic: One neuron to CNS effector (no ganglia), Acetylcholine is the only neurotransmitter.

• Autonomic: Two neurons between the CNS and the effector. Pre- ganglionic neuron is mylenated, the post-ganglionic is not. At the ganglia, the neurotransmitter is Ach and at the muscle: the neurotransmitter is either Ach or epinepherin and norepinepherin are released (if its sympathetic. These activate the smooth muscle, cardiac muscle and glands.

which autonomic system dominates?

• Parasympathetic.

Give examples iof some organs that have only one tyoe if ANS input.

• Sweat glands = sympathetic only.

• Visceral arterioles = only sympathetic.

• pupillary sphincter = parasympathetic only (constricts the pupil).

• Pupillary dilator = sympatheric only.

Difference between sympathetic and parasympathetic nervous system.

Parasympathetic: Ganglia are close to effectors, controlled by cranial nerves (vagus nerve has control over most parts of the body).

Sympathetic nervous system: sympathetic trunk / chain is far from its effectors. Some synmpathetic neurons have split axons that send messages up and down the sympathetic trink ganglia and out to collateral ganglia.

Receptors of the autonomic nervous system

Cholinergic Receptors:

• Found in the synapse of the sympathetic and parasympathetic ganglia, the postganglionic receptors.

• Adrenegenic receptors: Found only in the sympathetic postganglionic organs/ effectors.

Types of cholinergic receptors

• muscarinic = found in all parasympathetic target organs. Acetylcholine leads to all of the parasympathetic effects.

• Nicotinic = receptors are found in the parasympathetic and sympathetic ganglia. Stimulation of these effects leads to both sympathetic and parasympathetic effects. Acetylcholine breaks down rapidly

types of adregenic receptors

Two subtypes:

Aplha: simulates contractions

Bata: Inhibits contraction (not myocardium)

Simulation leads to long activation of neurons.

Alpha subtyles

a1 = causes contraction of smooth muscle. found mostly on blood vessel of viscera, NOT heart.

a2 = presynaptic receptors, promotes clotting.

Beta subtypes

B1 = heart muscles - tachycardia and increased contractibility.

B2 = relaxes bronchioles, relaxes uterus. relaxes cardiac arterioles.

B3 = Increases lipolysis.

Limbic + autonomic +endocrine stress

limbic via amygdyla and hypothalamus. then release of NE.

explain the process of HPA axis.

hypothalamis + pituitary + adrenal gland.

Hypothalamus releases corticotrophin (CRH), the pinuitarty releases (ACTH) and the adrenal glands relsease cortisol.