Nerve Conduction (Autonomic/Somatic) and Pain Flashcards
(7 cards)
Describe and compare the structure and function of the autonomic and somatic nervous systems.
The somatic nervous system controls voluntary activities and involves direct innervation of skeletal muscles. It consists of a single neuron that originates in the spinal cord and reaches the target muscle, releasing acetylcholine at the neuromuscular junction. Its actions are always excitatory.
The autonomic nervous system (ANS) controls involuntary functions such as heart rate, digestion, and glandular activity.
It has two main divisions: the sympathetic (fight-or-flight) and parasympathetic (rest-and-digest). Each pathway consists of two neurons: a preganglionic neuron from the CNS that synapses in an autonomic ganglion, and a postganglionic neuron that innervates the target organ. Depending on the division, neurotransmitters such as acetylcholine or noradrenaline are released, and their effects can be excitatory or inhibitory.
Define the following terms: preganglionic, postganglionic, sensation, neuron, synaptic junction
Preganglionic neuron: A nerve fiber that originates in the CNS and synapses in an autonomic ganglion.
Postganglionic neuron: The neuron that arises from the autonomic ganglion and innervates the target tissue.
Sensation: The conscious perception of stimuli such as touch, pain, heat, or pressure, detected by sensory receptors and transmitted to the brain.
Neuron: A fundamental cell of the nervous system that transmits electrical impulses.
Synaptic junction: The site where one neuron communicates with another neuron or an effector cell using neurotransmitters.
Describe the role of cerebrospinal fluid
CSF is a clear fluid produced mainly by the choroid plexus within the brain’s ventricles. It circulates around the brain and spinal cord, serving several functions. It cushions the brain and spinal cord from mechanical injury, provides nutrients, removes waste products, and maintains intracranial pressure. CSF also plays a role in homeostatic regulation of the brain’s extracellular environment.
Briefly describe the function of the spinothalamic, corticospinal and dorsal column pathways
The spinothalamic tract is responsible for transmitting pain, temperature, and crude touch sensations. It crosses to the opposite side of the spinal cord shortly after entering and ascends to the thalamus and then the cortex.
The dorsal column pathway carries information about fine touch, vibration, and proprioception. These fibers ascend on the same side of the spinal cord and decussate in the medulla before reaching the thalamus.
The corticospinal tract is the main motor pathway responsible for voluntary movement. It originates in the cerebral cortex, crosses over in the medulla, and travels down the spinal cord to synapse with lower motor neurons that control skeletal muscles.
List the autonomic transmitters and describe their role and function i.e. state where they are released and how they interact with the nervous system
In the autonomic nervous system, acetylcholine is released by all preganglionic neurons (in both sympathetic and parasympathetic systems) and by postganglionic neurons in the parasympathetic system. It acts on nicotinic and muscarinic receptors depending on the target site.
Noradrenaline is the primary neurotransmitter released by postganglionic sympathetic neurons, except for sweat glands, which still use acetylcholine.
Adrenaline is secreted by the adrenal medulla into the bloodstream during sympathetic stimulation, enhancing the fight-or-flight response.
These neurotransmitters exert their effects by binding to specific receptors on the target tissues, initiating changes in heart rate, smooth muscle tone, secretion, and metabolism.
Describe the function of the blood brain barrier
The blood-brain barrier is a protective mechanism composed of endothelial cells with tight junctions, astrocyte foot processes, and a basement membrane. It prevents harmful substances such as toxins, pathogens, and some drugs from entering the brain while allowing essential nutrients like glucose and amino acids through specialized transport systems. The BBB maintains the brain’s internal environment, protects against infection, and contributes to neurological homeostasis. In conditions like inflammation, trauma, or tumors, the BBB can become compromised, allowing unwanted substances into the brain tissue
Define different types of headaches, describe their symptoms and outline their pathophysiology
Headaches can be classified as primary or secondary. Primary headaches occur without an underlying disease, while secondary headaches are symptoms of other conditions such as infections, tumors, or vascular disorders.
Tension-type headaches are the most common and present as a bilateral, pressing or tightening pain of mild to moderate intensity. They are not aggravated by routine activity and are not associated with nausea or vomiting. The cause is often related to muscle tension or stress.
Migraine is a recurrent, often unilateral headache of moderate to severe intensity that can be throbbing or pulsating. It is usually accompanied by nausea, vomiting, sensitivity to light and sound, and sometimes preceded by an aura. The underlying pathophysiology includes cortical spreading depression, activation of the trigeminovascular system, and neurogenic inflammation. Changes in serotonin levels and vascular tone also contribute.
Cluster headaches are rare but extremely painful and occur in cyclical patterns or clusters. They are characterized by intense unilateral pain around the eye, along with autonomic symptoms like lacrimation, nasal congestion, or ptosis.
According to NICE guidelines (CG150), management of migraine includes identifying and avoiding triggers, using NSAIDs or triptans for acute attacks, and considering prophylactic medication (e.g. propranolol or topiramate) for frequent episodes. Tension headaches are typically managed with lifestyle modifications and simple analgesics. Cluster headaches may be treated with high-flow oxygen or subcutaneous sumatriptan during attacks.
