Week 5 - PNS, spinal cord anatomy and function & reflexes - Leaderboard

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Week 5 - PNS, spinal cord anatomy and function & reflexes - Details

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-Nerves -Ganglia -Plexus -Sensory receptors

List AND describe the structures of the PNS

A nerve is an enclosed, cable-like bundle of nerve fibres called axons, in the peripheral nervous system. A nerve transmits electrical impulses and is the basic unit of the peripheral nervous system

Define nerves

Ganglia are ovoid structures containing cell bodies of neurons and glial cells supported by connective tissue. Ganglia function like relay stations - one nerve enters and an other exits. The structure of ganglia is illustrated by the example of the spinal ganglion.

Define Ganglia

A network of converging and diverging nerve fibres Formed by spinal nerves in: -Cervical -Lumbar -Sacral regions No plexus in thoracic region as thoracic nerves (intercostal nerves) directly supply the specific structures or organs

Define Nerve plexus

Anterior and posterior branches of spinal nerves (C1-C5) Supplies parts of head, neck, shoulders and chest Phrenic nerve (C3-C5) -Supplies motor and sensory nerves to diaphragm (75% of breathing control) -Damage to this nerve results in breathing difficulties -Remember C3,4 and 5 keeps you alive!

Define cervical plexus

Anterior and posterior branches of spinal nerves (C5 – T1) Provides the entire nerve supply of the upper limbs Major peripheral nerves include -Radial nerve -Medial nerve -Ulnar nerve

Define branhcial plexus

Anterior and posterior branches of spinal nerves L1-L4, L4-L5, S1-S4 Supplies external genitals & anterior/medial thigh Femoral nerve (L2-4) supplies buttocks, perineum and part of lower limb Sciatic nerve (L4-S3) supplies posterior thigh and rest of leg below knee Sciatic nerve injury can occur due to a herniated (slipped) disc, pressure from the uterus during pregnancy or an improperly administered gluteal injection

Define lumbosacral plexus

Somatic NS - The somatic nervous system (SNS or voluntary nervous system) is the part of the peripheral nervous system associated with the voluntary control of body movements via skeletal muscles. The somatic nervous system consists of afferent nerves or sensory nerves, and efferent nerves or motor nerves. Autonomic NS - The autonomic nervous system is the part of the nervous system that supplies the internal organs, including the blood vessels, stomach, intestine, liver, kidneys, bladder, genitals, lungs, pupils, heart, and sweat, salivary, and digestive glands. The autonomic nervous system has two main divisions: Sympathetic

Name and describe the divisions of the PNS

Diagram

Describe three differences between spinal & cranial nerves

A fast, predictable, ‘involuntary’ response to changes in the environment (internal or external) that helps maintain homeostasis. Spinal reflex integration occurs in the spinal cord grey matter e.g. patellar reflex Cranial reflex integration occurs in the brainstem e.g. tracking movements of your eyes as they read

Define a reflex

If a reflex is not functioning normally there may be damage along the conduction pathway Patellar reflex may be absent in people with chronic diabetes due to nerve degeneration (knee jerk reflex) Pupillary reflex may be absent in brain damage or injury as the reflex synapses in the lower part of the brain (pupillary light reflex)

State the reasons for testing reflexes

The vagus nerve helps to regulate many critical aspects of human physiology, including the heart rate, blood pressure, sweating, digestion, and even speaking. For example, in the stomach, the vagus nerve increases the rate of gastric emptying, and stimulates acid production.

State the function of the vagus nerve

The Phrenic nerve is a nerve of the thoracic region. It is important for breathing, as it passes motor information to the diaphragm and receives sensory information from it. There are two phrenic nerves, a left and a right one The phrenic nerve is a nerve that originates in the neck (C3–C5) and passes down between the lung and heart to reach the diaphragm - very important for breathing

State the location & function of the phrenic nerve

An area of skin which sends most of its sensory input to the CNS from a single pair of spinal nerves Sensory signals travel from the skin, through dorsal root of spinal nerve, into spinal cord and up to the brain In physical assessment it helps determine: -If any segments of the spinal cord are not functioning -Which spinal nerves are affected Nurses test dermatomes with ice following spinal/epidural anaesthesia to check the level at which the anaesthesia is effective

Describe the clinical significance of dermatomes

Specific regions of the CNS coordinate different somatic processes using sensory inputs and motor outputs of peripheral nerves. A simple case is a reflex caused by a synapse between a dorsal sensory neuron axon and a motor neuron in the ventral horn. More complex arrangements are possible to integrate peripheral sensory information with higher processes. The important regions of the CNS that play a role in somatic processes can be separated into the spinal cord brain stem, diencephalon, cerebral cortex, and subcortical structures.

Define somatic sensory pathways

The defining characteristic of the somatic nervous system is that it controls skeletal muscles. Somatic senses inform the nervous system about the external environment, but the response to that is through voluntary muscle movement. The term “voluntary” suggests that there is a conscious decision to make a movement. However, some aspects of the somatic system use voluntary muscles without conscious control.

Define somatic motor pathways

Sensory input travels along tracts toward the brain, and motor output travels from the brain along tracts toward skeletal muscles and other effector tissues For example: Somatic sensory pathways are what perceive sensation. Like when someone tickles our foot Somatic motor pathways control more precise movements such as driving a car or keeping a stable balance

Describe the difference between somatic sensory & somatic motor pathways

Week 5 - PNS, spinal cord anatomy and function & reflexes

PNS, spinal cord anatomy and function & reflexes

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