EXSS1010 Lecture 2: EXSS1010 - NEUROMASCULAR STRUCTURE AND FUNCTION
30 May 2018
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EXSS1010 - NEUROMASCULAR STRUCTURE AND FUNCTION
LECTURE OBJECTIVES:
1. Understand the major divisions of the nervous system
2. Describe the structure and function of a neuron
3. Describe the structure of skeletal muscle from the whole muscle to sarcomere level
4. Discuss factors that influence muscle architecture
5. List and describe factors that can influence muscle contraction force production
NEURAL PHYSIOLOGY
MAJOR DIVISIONS OF THE NERVOUS SYSTEM
• Central nervous system: brain & spinal cord
• Peripheral nervous system
o Sensory (afferent): incoming
o Motor (efferent): outgoing
• Somatic: voluntary, to skeletal muscles
• Autonomic: involuntary, to viscera
▪ Sympathetic
▪ Parasympathetic
SENSORY DIVISION
• Transmits information from periphery to brain
• Major families of sensory receptors
o Mechanoreceptors: physical forces
o Thermoreceptors: temperature
o Nociceptors: pain
o Photoreceptors: light
o Chemoreceptors: chemical stimuli
MOTOR DIVISION
• Transmits information from brain to periphery
• Two divisions
o Autonomic: regulates visceral activity
o Somatic: stimulates skeletal muscle activity
STRUCTURE AND FUNCTION OF THE NERVOUS SYSTEM
• Neuron
o Basic structural unit of nervous system
o Has same basic structure everywhere in body
o Has three major regions
• Cell body (soma)
• Dendrites
• Axon
• Cell body
o Contains nucleus
o Neural impulse development
• Dendrites
o Receive neural impulses
o Carry impulse toward cell body
• Axon
o Sends neural impulses, starts at axon hillock
o End branches, axon terminals, neurotransmitters
ACTION POTENTIALS
• Electrical signal for communication in the nervous system
• Arises when a stimulus changes the normal electrical charge of a neuron
• Propagates down an axon
• Transmitted to next cell in line ending finally at an organ such as the brain muscle
SENSORY-MOTIOR INTEGRATION
• Process of communication and interaction between sensory and motor systems
• Five sequential steps
1. Stimulus sensed by sensory receptor
2. Sensory AP sent on sensory neurons to CNS
3. CNS interprets sensory information, sends out response
4. Motor AP sent out on α-motor neurons
5. Motor AP arrives at skeletal muscle, response occurs
MUSCLE FIBER CONTRACTION
• α-motor neuron receives action potential from central nervous system
• AP travels down the Axon until the Axon Terminals
• AP innovates muscle fiber cell and initiates muscle contraction
See diagram below
MOTOR UNIT
• Motor unit
o Single α-motor neuron + all fibers it innervates
o More operating motor units = more contractile force
• Eye muscles – 1:1 muscle/nerve ratio
• Hamstrings – 300:1 muscle/nerve ratio
Document Summary
Major divisions of the nervous system: central nervous system: brain & spinal cord, peripheral nervous system, sensory (afferent): incoming, motor (efferent): outgoing. Somatic: voluntary, to skeletal muscles: autonomic: involuntary, to viscera. Sensory division: transmits information from periphery to brain, major families of sensory receptors, mechanoreceptors: physical forces, thermoreceptors: temperature, nociceptors: pain, photoreceptors: light, chemoreceptors: chemical stimuli. Motor division: transmits information from brain to periphery, two divisions, autonomic: regulates visceral activity, somatic: stimulates skeletal muscle activity. Sensory-motior integration: process of communication and interaction between sensory and motor systems. Five sequential steps: stimulus sensed by sensory receptor, sensory ap sent on sensory neurons to cns, cns interprets sensory information, sends out response, motor ap sent out on -motor neurons, motor ap arrives at skeletal muscle, response occurs. Muscle fiber contraction: -motor neuron receives action potential from central nervous system, ap travels down the axon until the axon terminals, ap innovates muscle fiber cell and initiates muscle contraction.
