Skeletal Muscle Physiology & Neuroendocrine System LABORATORY SIX Skeletal Muscle Physiology & Neuroendocrine System

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 Within a skeletal muscle, not all fibers may be stimulated

EMG Trace Forearm flexors contraction by making a fist

Motor Unit Recruitment More grip force, more motor units activation, more muscle fibers contraction, Successively higher EMG amplitude It is worth noting as well that in Figure 2 even when the subject is not gripping the ball, there is a very small amount of electrical activity being generated by the muscles. This is called tonus, or muscle tone, and is a due to a near-constant stimulation of muscle fibers by motor neurons. 3/10/2008

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

The Neuroendocrine System (homeostasis control) Nervous system (rapid & transient) Central Peripheral Endocrine system (slow & long lasting) Autonomic nervous system – responsible for the regulation of body activities that are involuntary (not under conscious control); e.g., heart rate, the activity of digestive tract, reproductive cycles Ganglia: clusters of neuron cell bodies CNS: brain and spinal cord, centrally located, information received will be processed and commands would be sent down the neurons. PNS: consists of nerves bringing information to the CNS and carrying the command away from the CNS 6

The Endocrine System

Islets of Langerhans Microscopic view of a group of cells in the pancreas that are endocrine in function Contains alpha cells (glucagan) and beta cells (insulin)

Neuron Anatomy Neurons: functional cells that transport electrical impulses Neuroglia: non-conductive Schwann cells Reflex arc on P239 Dandrites transmit information into the soma and axon conveys impulses away from the soma. Myelin is a fatty substance that insulates larger neurons, allows nerve impulses to be conducted at a faster rate. In PNS, Myelin is produced by Schwann cells and in the CNS by oligodendrocytes.

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

(When studying the Cranial Nerves model, turn the page 180o) Auditory Spinal 11

Memory Tool for Learning Cranial Nerves Nerve Name Function Olfactory 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) Mnemonic device On Practicum II, first thing you do: write down these cranial nerves and their functions in the empty space in the back of your answer sheet ( memory dump).

Spinal Nerves (both sensory and motor in function) Cervical (C1-C8) Thoracic (T1-T12) Lumbar (L1-L5) Sacral (S1-S5) Coccygeal (Co) The first pair of cervical nerves attaches between the atlas and occipital bone. C1-C7 occupy the intervertebral foramina above the associated vertebrae Thoracic and lumbar nerve pairs occupy the intervertebral foramina below the associated vertebrae They also need to give the number with the name (e.g. C-1 where the abbreviation “C” is keyed out as cervical spinal nerve) 13

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 Plexseez (plural of plexes) 14