Fundamentals of the Nervous System and Nervous Tissue 11

The master controlling and communicating system of the body Functions Nervous System The master controlling and communicating system of the body Functions Sensory input – monitoring stimuli occurring inside and outside the body Integration – interpretation of sensory input Motor output – response to stimuli by activating effector organs

Organization of the Nervous System Central nervous system (CNS) Brain and spinal cord Integration and command center Peripheral nervous system (PNS) Paired spinal and cranial nerves Carries messages to and from the spinal cord and brain Notes from 12/4 Start here

Peripheral Nervous System (PNS): Two Functional Divisions Sensory (afferent) division Sensory afferent fibers – carry impulses from skin, skeletal muscles, and joints to the brain Visceral afferent fibers – transmit impulses from visceral organs to the brain Motor (efferent) division Transmits impulses from the CNS to effector organs

PNS Motor Division: Two Main Parts Somatic nervous system Conscious control of skeletal muscles Autonomic nervous system (ANS) No conscious control Regulates smooth muscle, cardiac muscle, and glands Has two divisions – sympathetic and parasympathetic 12/5 notes end here

The two principal cell types of the nervous system are: Nerve Tissue The two principal cell types of the nervous system are: Neurons – excitable cells that transmit electrical signals neuroglia or glial cells (Supporting cells) – cells that surround and wrap neurons Provide support & insulation Promote health and growth Classwork for 12/6 and 12/7 starts here

Structural units of the nervous system Neurons (Nerve Cells) Structural units of the nervous system Composed of a body, axon, and dendrites Their plasma membrane functions in Electrical signaling

Whitish, fatty, segmented sheath around most long axons Myelin Sheath Whitish, fatty, segmented sheath around most long axons It functions to: Protect the axon Electrically insulate fibers from one another Increase the speed of nerve impulse transmission

Formed by Schwann cells in the PNS A Schwann cell: Myelin Sheath Formed by Schwann cells in the PNS A Schwann cell: Envelopes and encloses the axon with its plasma membrane

Neuron Functional Classification Neurons are classified based on structure and function (we will only cover function) Functional: Sensory (afferent) — transmit impulses toward the CNS Motor (efferent) — carry impulses away from the CNS Interneurons (association neurons) — shuttle signals through CNS pathways Classwork for 12/6 & 12/7 ends here

The Moving Impulse Notes for 12/8 start The minimum level of a stimulus that is required to activate a neuron is called a threshold. A stimulus must be equal to or greater than the threshold to cause a neuron to produce an impulse.

The Nerve Impulse The way the nerve impulse travels through neurons is like how electricity travels through wires. Nerves generate tiny amounts of electrical charges, based on amounts of sodium ions (Na+) and potassium ions (K+).

This temporarily changes the charge of the neuron… The Moving Impulse A nerve impulse begins when a neuron is stimulated by another neuron or by its environment. At the leading edge of an impulse, the sodium gates open and sodium flows into the neuron. This temporarily changes the charge of the neuron… Potassium gates then open and allow potassium out of a neuron. This continues to reverses the charges further, forming an action potential …

Restoring the Resting Potential The sodium-potassium pump then moves sodium out of the cell and potassium into the cell This restores the original charge across the membrane 12/8 notes stop

https://www.youtube.com/watch?v=SdUUP2pMmQ4

The movement of Na and K changes the charge across the cell membrane Quick review When a stimulus overcomes the threshold a neuron starts an action potential The action potential is created by moving ions of sodium (Na) and potassium (K) The movement of Na and K changes the charge across the cell membrane When the Na and K levels are restored, the charge is reversed and the cell is at rest (resting potential) 12/9 notes

Neurons do not touch other neurons. The Synapse Neurons do not touch other neurons. The tiny space between two neurons is called a synapse. Neurotransmitters are chemicals released by one neuron to transmit an impulse across a synapse and stimulate the next neuron. 12/9 notes

https://www.youtube.com/watch?v=TevNJYyATAM