Biomedical Science - ANS and Limbic System

ANS functions

not conscious, involuntary, regulate internal environment

branches of ANS

-Sympathetic: reaches all parts of body, involved in fight or flight in organs and tissues

-Parasympathetic: more localised to certain organs/glands, rest and digest in organs and tissues

ANS pathways

-start in hypothalamus

-result of emotional input

-travel down fibres in the lateral spinal cord or activate cranial nerves

ANS lower motor neurons

-2 step pathway after emerging from spinal cord

-ALWAYS a pre ganglionic neuron and a post ganglionic neuron that synapse in a ganglion

3 key differences between sympathetic and parasympathetic

1. point of exit from CNS

2. length of pre and post ganglionic neurons

3. type of neurotransmitter

difference in point of exit from CNS

S: emerge alongside T1-T12 and L1-3 spinal nerves, reach all parts of the body

P: emerge from brainstem cranial nerves (III, VI, IX, X) and sacral spinal nerves (S2-4)

difference in length of pre and post ganglionic neurons

S: short pre, long post

P: long pre, short post

difference in type of neurotransmitter

S: 1) ACh, 2) Noradrenaline

P: 1) ACh, 2) ACh

effects of ANS on cardiovascular system

-S: increase HR, dilate blood vessels in muscle, constricts blood in GIT

-P: decrease HR

-blood vessels in skin don't need P supply, naturally dilate when S constriction eases and due to pressure inside

effects of ANS on respiratory system

S: dilates bronchial tree and pulmonary blood vessels to increase gas exchanhe

P: constricts bronchial tree and pulmonary blood vessels to normal diameters

effects of ANS on gastrointestinal tract

S: inhibits secretion, inhibits mobility, constricts blood vessels to gut

P: stimulates secretion of more saliva, stimulates mobility of gut, blood vessels dilate when sympathetic tone decreased

effects of ANS on skin

S: constricts blood vessels (pale), stimulates sweat secretion, causes hair erection

-no structures in skin have a P supply so will return to norm once threat has passed and S stimulation stops

effects of ANS on eye

S: pupils dilate, inhibits lacrimal gland secretion

P: pupils constrict, increases thickness of lens for accommodation, stimulates lacrimal secretion (tears

limbic system

-Areas in the cortex surrounding the diencephalon

-One of the 'oldest' parts of the brain

-The different areas are connected, forming complex communication loops

-Involved in cognitive functions -memory, attention, emotional responses

-Important because it controls many of the responses mediated by the ANS

important regions of limbic system for ANS

amygdala, hippocampus, hypothalamus, adrenal medulla

amygdala

emotional excitability -assesses sensory inputs for emotional significance e.g. fear, stress and threat and triggers response

hippocampus

contextual processing of experience, particularly stress (Also converts short-term memories into long-term and for spatial navigation)

hypothalamus

integrates these inputs, coordinating ANS activation of sympathetic or parasympathetic pathways to adapt to emotional and environmental demands (e.g., stress, danger, relaxation)