Autonomic Nervous System YR1 Lecture PDF

The Autonomic Nervous System Dr Gabriela Visini School of Medicine [email protected] Learning Objectives Describe the physiological and anatomical differences between the sympathetic and parasympathetic nervous systems and their functions. Describe the neurotransmitters that are released...

The Autonomic Nervous System Dr Gabriela Visini School of Medicine [email protected] Learning Objectives Describe the physiological and anatomical differences between the sympathetic and parasympathetic nervous systems and their functions. Describe the neurotransmitters that are released at different stages of autonomic transmission, and where neurons synapse (pre and post ganglionic). Describe the consequences of autonomic dysfunction. Describe the basic anatomy of the spinal column and spinal cord. Anatomy of the ANS The spine The spine is made up of separate vertebrae, which are bones that serve to create vertical alignment and protection for the spinal cord in the human body 7 cervical vertebrae (C1-C7) 12 thoracic vertebrae (T1-T12) 5 lumbar vertebrae (L1-L5) 5 sacral vertebrae (fused S1-S5 - sacrum) 3-5 coccygeal vertebrae (sometimes fused – coccyx) The spinal cord is made of white and grey matter that transmits information throughout the body pertaining to sensory and motor functions It runs from the brain (CNS) to the filum terminale, below the coccyx. Spinal control of reflexes AFFERENT SENSORY INFORMATION EFFERENT MOTOR CONTROL Ganglions Pre-ganglionic: Located in the CNS Post-ganglionic: Located outside of the CNS Copyright Nisora SYMPATHETIC Copyright Richard McLean Sympathetic pathway Sympathetic ganglia are down the spinal cord which allows them to send out signals fast and wide, serving their point as a fight or flight response. The preganglionic axons exit the spinal cord via the ventral root of spinal nerves before separating from the ventral root to form a white ramus They enter paravertebral ganglia/sympathetic chain or trunk and synapse onto postganglionic neurons at the ganglion on same level; at different level; or pass through without synapsing to form a splanchnic nerve which synapses with postganglionic neurons within the prevertebral ganglia Sympathetic chain PARASYMPATHETIC Physiology of the ANS Neurotransmitters The major neurotransmitters released in autonomic transmission are acetyl choline and noradrenaline While hormones and neurotransmitters may be considered different, depending on the target tissues and where they were released, compounds can exert different effects. Sympathetic vs Parasympathetic In the sympathetic nervous system, noradrenaline is released onto target organs, however acetyl choline is used at the ganglion level at the spinal cord. In the parasympathetic system, acetyl choline is released at both levels. Function of the ANS Sympathetic vs Parasympathetic FIGHT OR FLIGHT REST AND DIGEST Increased rate force of heart contractions Decreased rate and force of heart contractions -> decreased BP Vasoconstriction -> shunts blood to vital organs Releases sweat Broncodilation -> increases oxygen intake Increases glucose release Releases adrenaline and dilates pupils Constricts pupils and airways Increased gastrointestinal activity and increased bile release Spinal injury Injury to the spine can cause different loss of function depending on the level affected Injury can extend to both sensory and motor function Loss of ANS function can be assessed and related to the level of spinal injury (i.e. where the injury is located in the spinal column) Summary The ANS controls pivotal functions in the body and both sympathetic and parasympathetic systems can affect the same target organs – though their effects depend on the target organ and which neurotransmitter is released by the postganglionic neuron Damage to the spinal cord can result in location -specific ANS dysfunction