Organization of the Nervous System 1.Central Nervous System The brain + the spinal cord –The center of integration and control 2.Peripheral Nervous System The nervous system outside of the brain and spinal cord Consists of: –31 Spinal nerves –12 Cranial nerves

The Nervous System of a Vertebrate

Central Nervous System (CNS) contains fluid-filled spaces which contain cerebrospinal fluid (CSF). –White matter is composed of bundles of myelinated axons –Gray matter consists of unmyelinated axons, nuclei, and dendrites.

Figure 48.16x Spinal cordFigure 48.16x Spinal cord Gray Matter White Matter Spinal Cord

Figure The main parts of the human brainFigure The main parts of the human brain

Cerebrum is the most highly evolved structure in the mammalian brain. Functions: interpretation, initiating voluntary movements, storing memory, retrieving memory, reasoning, center for intelligence and personality Corpus Callosum is the major connection between the two hemispheres.

Corpus callosum Thalamus Hypothalamus Midbrain Pons Medulla oblongata

Thalamus- leads to cerebral cortex, channeling impulses to appropriate part of cerebral cortex for interpretation Hypothalamus- Regulates autonomic activity involved in thermoregulation, hunger, thirst, sexual and mating behavior, etc… part of the limbic system (emotions) The pituitary gland is attached to the hypothalamus

Structure and Function Brain stem--Consists of the medulla oblongata, pons, and midbrain. Medulla Oblongata- Breathing, heart and blood vessel activity, swallowing, vomiting, digestion, and relays information to and from higher brain centers Pons- involved in the regulation of visceral activities such as breathing and relays info. to higher brain

Figure 48.28x1 Brain MRI

Mapping Language Areas of the Cerebral Cortex Max Min

The Limbic System: Amygdala, Hippocampus, Olfactory Bulb

Midbrain-integration of sensory information, in the regulation of visual and auditory reflexes, and relays as well Cerebellum error-checks and coordinates motor activities, perceptual and cognitive factors. Relays sensory information about joints, muscles, sight, and sound to the cerebrum. Coordinates motor commands issued by the cerebrum; maintains posture

Peripheral Nervous System Responsible for communication btwn the CNS and the rest of the body. Can be divided into: –Sensory Division Afferent division –Conducts impulses from receptors to the CNS –Motor Division Efferent division –Conducts impulses from CNS to effectors (muscles/glands)

Simple Nerve Path

The Knee-Jerk Reflex

Diversity in Nervous Systems

Overview of a Vertebrate Nervous System

Motor Efferent Division Can be divided further: –Somatic Nervous System VOLUNTARY (generally) Somatic nerve fibers that conduct impulses from the CNS to skeletal muscles –Autonomic Nervous System INVOLUNTARY (generally) Conducts impulses from the CNS to smooth muscle, cardiac muscle, and glands.

Autonomic Nervous System

Parasympathetic and Sympathetic Nervous Systems

Structure of a Vertebrate Neuron

Neuron Shape is Dependent on Numbers of Synapses Axon

Neurons

Types of Neurons Sensory Neurons afferent; carry impulses to CNS Interneurons link neurons in the CNS Motor Neurons carry impulses away from CNS to effectors such as muscles and glands SUPPORT CELLS Of Nervous System Schwann Cells: peripheral nervous system— produce myelin sheath Oligodendrocytes: CNS; myelinating cell Astrocytes: CNS; form scar tissue, mop up excess ions, etc, induce synapse formation, connect neurons to blood vessels

Synaptic Transmission An AP reaches the axon terminal and causes V-gated Ca 2+ channels to open. Ca 2+ rushes in & initiates NT exocytosis. NTs diffuse across the synaptic cleft and then bind to receptors on the postsynaptic membrane and initiate some sort of response on the postsynaptic cell.

Schwann Cells

A Chemical Synapse

Nerve Impulses: hill.com/sites/ /student_view0/chapter44/the_nerve_impulse.ht ml Transmission Across a Synapse: hill.com/sites/ /student_view0/chapter44/transmission_across_a_sy napse.html Synaptic Transmission: Neurons and Synapses :

The Major Known Neurotransmitters Put Some Ach Into It!

Forces Behind Resting Potential Selective Permeability- some molecules pass through membrane more freely than others; ion channels Sodium-Potassium Pump- transports 3 Na out of, 2 K into cell Result: Concentration Gradient Electrical Gradient

The Basis of the Membrane Potential

Resting Membrane Potential: Resting Potential: ctures_PPT/media/48_10RestingPotential_A.swf

The Sodium-Potassium Pump: a Specific Case of Active Transport

Sodium-Potassium Exchange Pump: potassium_exchange_pump.html Resting Potential: _Lectures_PPT/media/48_10RestingPotential_A.swf Resting Membrane Potential: Voltage-Gated Channels and the Action Potential :

Molecular Basis of Action Potential – transmission of a signal along an axon Sodium channels open once threshold is reached, influx of sodium Potassium channels open at AP peak; potassium flows out

Generating an Impulse polarized membrane: inside is negative relative to the outside under resting conditions due to distribution of ions controlled by Na+/K+ pump that require ATP Nerve impulse starts when the membrane of the nerve depolarizes due to some stimulus, chemical, temp. changes, mechanical, etc…. Depolarization is caused by the influx of Na+ which causes the membrane to become more positive. This starts an action potential, or nerve impulse. They follow the all or none law!!! The membrane will repolarize when K+ leaves the cell setting the membrane back to resting potential or polarized This de and repolarization continues down the nerve until it reaches another nerve to pass on the impulse or until it reaches an effector.

Propagation of the Action Potential

The Action Potential ctures_PPT/media/48_13ActionPotential_A.swf

Saltatory Conduction

Graded potentials and the action potential in a neuron

What are the two components of the Central Nervous System? What are the two components of the Peripheral Nervous System?

The two hemispheres of the brain are connected by the:

Last Review Questions for the Week: What are the two components of the Peripheral Nervous System? What type of response is processed directly in the spinal cord with no impulses traveling to the brain?

Which part of the neuron receives impulses? carries them away? Describe what occurs at the axon terminal to cause the transmission of a nerve impulse from one neuron to the next. What is the minimum level of a stimulus required to cause an action potential in a neuron called?

What is meant by the term, “all-or- none principle” with regards to the conduction of nerve impulses? What is the difference between a reflex and a normal response?

Draw two neurons side by side and label the cell bodies, myelin sheaths, axon terminals, synapse, nodes, and place of neurotransmitter secretion. Describe what happens during an action potential including movement of the appropriate ions across the axon and the correct charges inside and outside the cell.

Describe the path of a nerve impulse that would occur when someone you don’t like touches your hand and you pull your hand away. Use the following terms: motor neurons, hand, interneurons, sensory neurons, effector (muscle), brain, spinal cord.