Chapter 15/16 - The Nervous System: Organization

Divisions of the Vertebrate Nervous System The central nervous system (CNS) is the brain and spinal cord. The peripheral nervous system (PNS) is the nerves and ganglia. (Ganglia are clusters of nerve cell bodies outside the CNS.)

CONT’D

Somatic Nervous System The somatic nervous system provides conscious, voluntary control. It includes all of the nerves that serve the skeletal muscles and the exterior sense organs.

Reflex Arc

Autonomic Nervous System

CLASSES OF NEURONS Sensory neurons (afferent neurons) conduct sensory information toward the CNS. Sensory neurons have a long dendrite and a short axon. The brain and spinal cord contain interneurons. These receive information and if they are sufficiently stimulated, they stimulate other neurons. Motor neurons (efferent neurons) send information from interneurons to muscle or gland cells (effectors).

Neurons STRUCTURE Cell Body- contains nucleus and organelles Dendrites- receive input Axon -conducts impulses away from the cell body Axon Terminals - Neurotransmitters are manufactured in the cell body but released from axon terminals. The neurotransmitters stimulate other neurons.

CONT’D Nerves and Ganglia Axons and dendrites are bundled with axons or dendrites from other neurons to form nerves. Clusters of neuron cell bodies are called ganglia.

SODIUM POTASSIUM PUMP NEURON MEMBRANE

ACTION POTENTIAL

Excitatory and inhibitory postsynaptic potentials A synaptic potential can be excitatory (they depolarize) or inhibitory (they polarize). Some neurotransmitters depolarize and others polarize. There are more than 50 different neurotransmitters. In the brain and spinal cord, hundreds of excitatory potentials may be needed before a postsynaptic cell responds with an action potential. l

Synaptic integration

Temporal and Spatial Summation The effect of more than one synaptic potential arriving at a neuron is additive if the time span between the stimuli is short. This is called temporal summation. The effect of more than one synaptic potential arriving at a given region of a neuron can also be additive. This is called spatial summation.

Synaptic Transmission

Central Nervous System The central nervous system is the brain and spinal cord. It is wrapped in 3 layers of membranes called meninges. Meningitis is an infection of these coverings. The brain contains fluid-filled ventricles that are continuous with the central canal of the cord.

The Spinal Cord

The Brain …Hopefully not yours

Regions of Disease and Disorders

Lobes of the cerebral cortex Summary LobeFunction Frontal motor functions; permits conscious control of skeletal muscles; contains the primary motor cortex conscious thought Parietalsensory areas from the skin; contains the primary sensory cortex OccipitalThe primary visual cortex is located within the occipital lobe. Temporalhearing and smell

Parts of the Brain

Summary of Brain Structure Brain StructureFunction Medulla oblongata Vital functions such as breathing, heart rate, and blood pressure Reflexes such as vomiting, coughing, sneezing, hiccupping, swallowing, and digestion Neurons cross PonsBreathing, connects spinal cord, cerebellum and higher brain centers CerebellumMotor coordination Midbrain Receives visual, auditory, and tactile information In mammals, this information is sent to the thalamus and higher brain centers. In lower vertebrates, the information is further processed in the midbrain.

Thalamus Relays sensory information to the cerebral cortex. Contains part of the reticular formation (controls arousal). Hypothalamus Maintains homeostasis, regulates the endocrine system Contains part of the Limbic system (controls emotion) Cerebrum Processes sensory information and produces signals that move the skeletal muscles. Cerebral Cortex This is the outer layer of the cerebrum. Thinking, intelligence, and cognitive functions are located here. Processing of sensory information and motor responses