LABORATORY SIX

Skeletal Muscle Physiology &

Neuroendocrine System

1

An Introduction to Electromyogram

• Muscle contraction begins with ion flow across the muscle cell membrane, causing depolarization of the muscle cell

• The flow of electrically charged ions causes electrical current

• Using electrodes, we can detect this current and visualize it with a computer - EMG

2

EMG TraceForearm flexors contraction by making a fist

3

Motor Unit Recruitment More grip force, more motor units

activation, more muscle fibers contraction, Successively higher EMG amplitude

3/10/2008 4

Electromyogram Recording

• Biopac Student software is used to look at graded response in a whole muscle

• Calibrate the software for each volunteer– Eliminate electrical noise– Normalize for each individual muscle action

• To see a graded response, the volunteer does a minimal (1/4), a small (1/2), a medium (3/4), and a full (4/4) grip force

• By increasing the grip force, you are activating more motor units

5

The Neuroendocrine System(homeostasis control)

• Nervous system (rapid & transient)

• Central• Peripheral

• Endocrine system (slow & long lasting)

The Endocrine System

Islets of Langerhans

Microscopic view of a group of cells in the pancreas that are endocrine in function

Neuron Anatomy

• Neurons: functional cells that transport electrical impulses

• Neuroglia: non-conductive – Schwann cells

• Reflex arc on P239

The Peripheral Nervous System

• Cranial Nerves - 12 pairs– Sensory (afferent) - carry impulses toward the CNS– Motor (efferent) - carry impulses away from the CNS– Mixed (both sensory & motor in a nerve bundle)– Located inferiorly, numbered in order, anterior to

posterior

• Spinal Nerves - 31 pairs– Mixed– Numbered based on the name and number of their

associated vertebrae

Cranial Nerves

Auditory

Spinal

(When studying the Cranial Nerves model, turn the

page 180o)

Memory Tool for Learning Cranial Nerves

Nerve Name FunctionOlfactory nerve I On Some (sensory)Optic nerve II Old Say (sensory)Oculomotor nerve III Olympus’ Marry (motor)Trochlear nerve IV Towering Money (motor)Trigeminal nerve V Top But (both S & M)Abducens nerve VI A My (motor)Facial nerve VII Finn Brother (both)Auditory nerve VIII And Says (sensory)Glossopharygeal nerve IX German Big (both)Vagus nerve X Viewed Brains (both)Spinal Accessory nerve XI Some Matter (motor)Hypoglossal nerve XII Hops More (motor)

Spinal Nerves(both sensory and motor

in function)

• Cervical (C1-C8)• Thoracic (T1-T12)• Lumbar (L1-L5) • Sacral (S1-S5)• Coccygeal (Co)

Plexuses

Collection of nerves that innervates a specific region of the body:

• Cervical: head & neck, diaphragm

• Brachial: upper limb• Lumbar: anterior thigh• Sacral: buttocks, lower

limb, and pelvis