Musculoskeletal & Nervous System Quiz MNB.14

Musculoskeletal System, Nervous System & Bioelectricity, MNB.14

• The lecture covers the musculoskeletal system, nervous system, and bioelectricity, specifically focusing on the peripheral nervous system and reflexes.
• The presenter is Professor Warren Thomas.
• The date of the lecture is November 26, 2024.

Learning Outcomes

• Learners will be able to describe the effects of neurotransmitters on various bodily systems.
• Learners will be able to recall the peripheral nervous system.
• Learners will be able to describe the structure of the spinal cord and its connection to the somatic nervous system.
• Learners will be able to outline the operation of the reflex arc.
• Learners will be able to differentiate between monosynaptic and polysynaptic reflexes.

Chemical Synapse

• The sequence of events converts electrical energy (action potential) to a chemical signal (neurotransmitter) and back to electrical energy.
• In the Autonomic Nervous System (ANS), this can involve neuron-neuron communication (at ganglia) or neuron-target tissue interaction.
• Key components of chemical synapses include synaptic vesicles, neurotransmitters, receptors in the plasma membrane of the postsynaptic neuron, and the synaptic cleft.

Neurotransmitters

• Approximately 40 different chemicals act as neurotransmitters.
• Each neuron typically releases only one small-molecule neurotransmitter.
• A neuron may also release one or more neuropeptides concurrently.
• Postsynaptic neurons often have receptors for multiple neurotransmitters, which can be excitatory or inhibitory.
• Examples of neurotransmitters and their abbreviations, locations, receptors, and effects are provided in a table.

Peripheral Nervous System (PNS)

• The PNS is divided into the autonomic nervous system (ANS) and somatic nervous system.
• The ANS further branches into sympathetic, parasympathetic, and enteric systems.
• 31 pairs of spinal nerves branch from the spinal cord, with specific locations and names.
• The lecture provides details on the anatomy and function of the sympathetic and parasympathetic nervous systems, including how they branch through the body and their function.

Autonomic Nervous System

• The Autonomic Nervous System has pre-ganglionic and post-ganglionic neurons.
• Pre-ganglionic neurons run from the spinal cord to the ganglion.
• Post-ganglionic neurons run from the ganglion to the target organ.

Sympathetic Nervous System

• Sympathetic nervous system has a thoracolumbar outflow with short pre-ganglionic and long post-ganglionic neurons.
• Neurons connect to paravertebral ganglia on both sides of the spinal column.
• The primary neurotransmitter of the SNS is acetylcholine (ACh) at the synapse.
• The neurotransmitter at the target tissue is adrenaline.
• The effect of the sympathetic system, in a generalized way, is preparation for the "fight or flight" response.

Parasympathetic Nervous System

• This system has a craniosacral outflow with long pre-ganglionic and short post-ganglionic neurons.
• Ganglions lie close to or within target organs.
• The primary neurotransmitter for both pre- and post-ganglionic neurons is Acetylcholine (ACh).

Spinal cord

• The spinal cord functions as a transmitter of nerve impulses and a reflex center.
• Anatomically, the spinal cord is protected by the vertebrae and lies within the vertebral canal.
• The histology of the spinal cord distinguishes between grey matter, and white matter.
• Grey matter comprises cell bodies and dendrites of motor and interneurons, along with neuroglial cells and blood vessels.
• White matter contains bundles of axons and dendrites.
• The spinal cord is divided into 4 regions: Cervical (neck), Thoracic (chest/upper back), Lumbar (lower back), and Sacral (base of spine).

Spinal Reflexes

• Reflex actions are automatic responses to stimuli that do not require conscious thought.
• Reflex actions involve sensory neurons, interneurons, and motor neurons.

Reflex Arc

• Receptor cells pick up stimuli and carry it towards the spinal cord through sensory neurons and long afferent somatic nerve fibers.
• The sensory neurons synapse with interneurons in the greay matter.
• In the grey matte, the interneurons synapse with the efferent/motor neurons.
• The efferent/motor neuron carries the signal to the effector organ.
• Details on various components of the reflex arc are included along with specifics regarding monosynaptic and polysynaptic reflexes.

Monosynaptic vs Polysynaptic Reflexes

• Monosynaptic reflexes involve direct connection between sensory and motor neurons.
• Polysynaptic reflexes utilize interneurons, facilitating more complex responses.

Stretch Reflex

• This reflex results in muscle contraction in response to stretching.
• It is a monosynaptic reflex. The reflex arc starts at the receptor and then travels to the spinal cord where it will synapse with the effector muscles causing it to contract. This is involved in the patella tap in your knee.

Tendon Reflex

• This reflex relaxes muscles to prevent tendon rupture from excessive tension
• It is a polysynaptic reflex.

Summary

• The lecture covers a comprehensive overview of the peripheral nervous system.
• Neurotransmitters control various bodily systems, while the peripheral nervous system and its two branches — the autonomic and somatic nervous systems — are critical for functionality.
• Reflex responses, including stretch and tendon reflexes, are essential in regulating muscle tension.